Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IATED-INT ASSOC TECHNOLOGY EDUCATION & DEVELOPMENT  

Over the years, it has been a problem in Japan that students do not actually feel the significance and usefulness of studying Science compared with another country. However, the school hours for experimental training in Science and Technology will not be increased. The number of teachers for Science and Technology has not been increased. Therefore, effective science educational materials have been required. Junior and Senior high school students are interested in space anatomy, space technology, rockets and so on. Pictures of rockets are commonly included in a Japanese Science textbook to stimulate interest towards Science. Therefore, a rocket is considered to be a useful tool in increasing the motivation of a student studying Science and Technology. In this study, a small hybrid rocket was developed as an educational material using conventional materials such as a carbonate plastic bottle, polyethylene, aluminum, steel, and nichrome wire. The rocket can be launched in a science classroom regardless of weather.Japan Society for the Promotion of Science (JSPS) supports many scientific programs. "Hirameki, Tokimeki, Science" (HTS) is one of such outreach programs held by JSPS. HTS introduces university scientific researches and a fascination of science to the students between 5th and 12th Grade (10 to 18 years old) students. Our educational hybrid rocket was demonstrated in HTS. The title of our program is "Excitement of a Real Rocket" (Rocket outreach program for tomorrow's study). The aim of this study is to validate the effectiveness and problems of the utilization of hybrid rocket as educational material in an outreach program such as HTS program. As a result, the utilization of the educational hybrid rocket was very effective not only in order to evoke the interest of engineering and science but also in order to achieve the purpose of HTS. However, we have to try to shorten the assembling process and to simplify preparations equipment.

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Language：Japanese   Publishing type：Research paper (scientific journal)  

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

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Siva Muppala, Masaya Nakahara, Tidswell, V. C. Madhav Rao, Siaka Dembele, Konstantin Volkov

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IATED-INT ASSOC TECHNOLOGY EDUCATION A& DEVELOPMENT  

The movement of science, technology, engineering, mathematics integrated education (STEM) is being promoted in many countries. Similarly in Japan, in order to promote the originality, intellectual curiosity, research interest in science, technology, mathematics of students, and to foster the next generation of leaders in science and technology, many programs such as SSH(Super Science High Schools), SPP(Science Partnership Project), and so on have been performed. However, over the years, it has been a problem in Japan that students do not actually feel the significance and usefulness of studying science. It's said that substantiality of empirical learning is important in order to let a student recognize the significance of studying science. In order to improve a student's individual skill and volition, teachers have to understand the personality of each student further, and find the time for students to face the teachers while cooperating with an organization outside of the school. However, the school hours for experimental trainings in science and technology will not be increased when it was reviewed from its circumstances of the past courses of study. Furthermore, it is difficult to conduct time-consuming experiments and training in a public junior high school due to extra costs, extra works required more than a regular lesson and teaching. Even though, most teachers have high volition and consciousness about the education in the school. Therefore, effective educational materials are required in science and technology. Junior high school students are fascinated with new technology. A robot is considered to be a motivation to increase a student's interest in science or technology. The aim of this study is to validate the effectiveness and problems of the utilization of a robot as an education material for usual classes in a public junior high school.
A collaboration science and technology class was performed in third grade of Kazokita Junior High School in Saitama, Japan, using small mobile robots as teaching materials. The number of students was 39. Ten teaching assistants volunteered. The class lesson was carried out for two hours continuously with a break of 10 minutes in between. A small mobile robot was assembled using electric parts on a bead board as an educational material in the class. The application program used to mobilize the mobile robot was S4A(Scratch for Arduino) and modified specifically for the class. The contents taught are related to the science and technology text book chapter "Information and communications technology in our life" and "Let's know a role and the function of the program". The questionnaire surveys of the science class showed that students recognized that they made a robot by themselves and most students enjoyed the class and want to do again. As a result, the utilization of the small mobile robot as an educational material with the cooperation between a junior high school and a university was very effective not only in order to achieve the purpose of a science lesson, but also in order to evoke the interest of engineering and science.

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：愛媛大学教育・学生支援機構  

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

<p>The objective of this study is to establish a method of direct combustion that allows safe and effective incineration of difficult-to-process woody waste as well as its utilization as fuel. A tremendous amount of debris including woody waste was washed into the sea by the tsunami of the Great East Japan Earthquake in 2011, and still remains on the coastal seabed. In order to examine the feasibility and effectiveness of incineration of the woody debris containing seawater, combustion experiments are conducted using a small combustor by applying the two-stage combustion method which we developed for woody biomass. Simulated wastes with three different moisture contents (13, 22, 38 %) are prepared by saturating woody chips with artificial seawater. The experiments confirm that the two-stage combustion method is applicable to the combustion of the woody waste containing seawater. In addition, it is clarified that combustion temperature could be widely controlled by changing the amount of air in the range of about 860 to 1250 K in the pyrolytic combustion process and about 820 to 1240 K in the surface combustion process. The results indicate that the two-stage combustion method is effective to reduce salt content in combustion gas, and that a large part of contained salt could be recovered as a residue after incineration. It is also revealed that combustion temperature is an important factor influencing the generation of hydrogen chloride.</p>

DOI： 10.1299/transjsme.16-00351

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

This study was made to establish a prediction method of turbulent burning velocity for lean hydrogen-propane-air mixtures, with paying special attention to the importance of local burning velocity to turbulent burning velocity. In this study, lean hydrogen added propane air mixtures with different rates of addition of hydrogen<i> δ</i><i>_H</i> and equivalence ratios <i>Φ</i>(0.5, 0.6 and 0.8) were prepared, where <i>Φ</i> includes fuel concentration below a lean flammability limit of propane-air mixtures. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity <i>S</i><i>_F</i> of turbulent flames was quantitatively measured as a key parameter of local burning velocity. It was found that the mean values of <i>S</i><i>_F</i>, <i>S</i><i>_F,m</i>, at the same<i> u'/S</i><i>_L</i>₀ tended to increase as hydrogen was added to lean propane-air mixtures with <i>Φ</i>=0.8. The trends of <i>S</i><i>_F,m</i> against <i>u'/S</i><i>_L</i>₀ also corresponded well to its turbulent burning velocities, regardless of <i>δ</i><i>_H</i> and <i>Φ</i>. An attempt was also made to predict the turbulent burning velocity by some empirical equations. As a result, the predicted turbulent burning velocities, where the obtained <i>S</i><i>_F,m</i> was employed instead of <i>S</i><i>_L</i>₀as a local burning velocity, were in better agreement with experimental ones for lean hydrogen-propane-air mixtures.

DOI： 10.1299/transjsme.14-00318

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Aiming to make clear a method for improving combustion of micro/meso-scale flames, effects of dilution gas and characteristic chemical time tau(c) on the burning velocity of meso-scale flames were studied experimentally using H-2-O-2-dilution gas mixtures. The meso-scale outwardly propagating spherical laminar flames, in a flame radius r(f) range of approximately from 1 to 5 mm, were observed by using sequential schlieren images recorded under appropriate ignition condition. The mixtures at each equivalence ratio (phi = 0.5-1.0) were diluted with Ar, CO2 or N-2 to set different laminar burning velocities (S-L0 = 15-90 cm/s) at so-called unstretched flames, because tau(c) can vary depending on S-L0. The radius rf and the burning velocity SLl of micro-scale flames were estimated from obtained images. Macro-scale laminar flames with r(f) &gt;7 mm were also examined for comparison. It was found that the burning velocities of meso-scale flames for the mixtures diluted with CO2 at phi = 0.5-1.0 have a tendency to decrease with increasing rf, and approach those of macro-scale flames, whereas such a trend cannot be seen for the mixtures diluted with Ar as well as N-2 at phi = 0.7-1.0. This shows flame size and Karlovitz number to have optimum values to improve burning velocity. The S-Ll at the same rf; however, tended to meaningfully decrease with the Lewis number Le and the Markstein number Ma, irrespective of the dilution gas types in addition to phi. It also becomes clear that the observed optimal values of each dilution gas are little dependent on tau(c). (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

DOI： 10.1016/j.proci.2014.05.050

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Language：Japanese   Publisher：The Robotics Society of Japan  

In order to improve a student's individual skill and volition, teachers have to understand the personality of each student further, and find the time for students to face each other, cooperating with an organization outside of the school. However, it is difficult to conduct time-consuming experiments and trainings in a public junior high school due to extra costs, extra works other than a regular lesson and teaching, and so on, though almost teachers have high volition and consciousness for the education in a school. The aim of this study is the validation about the effectiveness and problems of the utilization of robots as a teaching material for science classes in a public junior high school collaborated with the university. As a result, the utilization of robots as a teaching material with the cooperation between a junior high school and a university was very effective not only in order to achieve the purpose of a science lesson, but also in order to evoke the interest to engineering and science. We gave and obtained the precious impression in 50 minutes class work, as shown in the comments in the questionnaire survey. Therefore we attached a subtitle ``The treasures of the 50 minutes''.

DOI： 10.7210/jrsj.33.613

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

The purpose of this study is to establish a two-stage combustion method, which has advantages of a wide range of combustion temperature and high controllability compared to the conventional methods, from the standpoint of promoting the use of woody biomass as solid fuel and the effective utilization of unused wood materials. In this method, we use a vertical grate-type combustor, into which chipped woody biomass is loaded as a batch. The wood chips are burned at a low air ratio of 0.3 to 0.5 from the top to the bottom of a fuel layer, which is opposite to the direction of supplied air flow. The two-stage combustion method can be achieved through the way described above. Under the new method, wood chip combustion can be divided into two stages, namely, pyrolytic combustion process (generation of carbides) and surface combustion process (combustion of carbides). In this paper, the combustion of wood chips with different moisture contents (11, 20, 35%) was investigated, and the effects of the amount of air and moisture contents on the burning characteristics were discussed. The result clarified the mechanisms of combustion under the new method. In addition, we confirmed that combustion temperature and burning rate could be controlled by simply changing the amount of air. The temperature could be changed in the range of about 800 to 1300 K in the pyrolytic combustion process and about 800 to 1500 K in the surface combustion process.

DOI： 10.1299/transjsme.2014tep0367

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The present study is experimentally performed to establish a prediction method of turbulent burning velocity for stoichiometric hydrogen-oxygen-dilution gas mixtures, paying special attention to the importance of local burning velocity to turbulent burning velocity, where Ar and CO2 in addition to N2 as a conventional dilution gas were adopted. In this study, stoichiometric mixtures with different dilution ratios, whose laminar burning velocity SL0 was varied from 25 to 90 cm/s, were also used under almost the same weak turbulence condition, so that the ratio of turbulence intensity u&#039; to SL0 becomes 0.4 to 2.0. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between a flame shape and a flame movement in a constant-volume vessel. The local flame displacement velocity SF of turbulent flames was quantitatively measured as a key parameter of local burning velocity. It was found that the trends of the mean values of SF, SF, m, against u&#039;/SL0 corresponded well to its turbulent burning velocities; however, regardless of dilution gas types SF, m did not increase infinitely with increasing u&#039;/SL0. An attempt was also made to predict the turbulent burning velocity using some empirical equations. As a result, the predicted turbulent burning velocities, where the obtained SF, m was employed instead of SL0 as the local burning velocity, were in good agreement with the experimental findings.

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This study was made to establish a prediction method of turbulent burning velocity for stoichiometric hydrogen-oxygen-argon mixtures, with paying special attention to the importance of local burning velocity to turbulent burning velocity. In this study, stoichiometric mixtures with different dilutions, whose laminar burning velocity SL0 was varied from 25 to 90 cm/s, were used under almost the same weak turbulence condition, so that the ratio of turbulence intensity u&#039; to SL0 becomes 0.4 to 2.0. Nitrogen was also used as a conventional dilution gas for comparison with argon. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity SF of turbulent flames was quantitatively measured as the key parameter of local burning velocity. It was found that the trends of the mean values of SF, SF,m, against u&#039;/SL0 corresponded well to its turbulent burning velocities, but SF,m did not increase infinitely with increasing u&#039;/SL0. The turbulent burning velocity also attempted to be predicted by some empirical equations. As a result, the predicted turbulent burning velocities, where the obtained SF,m was employed instead of SL0 as the local burning velocity, were in good agreement with experimental ones. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.79.1675

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This study was made to establish a prediction method of turbulent burning velocity for stoichiometric hydrogen-oxygen-argon mixtures, with paying special attention to the importance of local burning velocity to turbulent burning velocity. In this study, stoichiometric mixtures with different dilutions, whose laminar burning velocity <i>S</i>_<i>L</i>0 was varied from 25 to 90 cm/s, were used under almost the same weak turbulence condition, so that the ratio of turbulence intensity <i>u'</i> to <i>S</i>_<i>L</i>0 becomes 0.4 to 2.0. Nitrogen was also used as a conventional dilution gas for comparison with argon. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity <i>S_F</i> of turbulent flames was quantitatively measured as the key parameter of local burning velocity. It was found that the trends of the mean values of <i>S_F</i>, <i>S_F,m</i>, against <i>u'</i>/<i>S</i>_<i>L</i>0 corresponded well to its turbulent burning velocities, but <i>S_F,m</i> did not increase infinitely with increasing <i>u'</i>/<i>S</i>_<i>L</i>0. The turbulent burning velocity also attempted to be predicted by some empirical equations. As a result, the predicted turbulent burning velocities, where the obtained <i>S_F,m</i> was employed instead of <i>S</i>_<i>L</i>0 as the local burning velocity, were in good agreement with experimental ones.

DOI： 10.1299/kikaib.79.1675

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This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale outwardly propagating spherical laminar flames in the range of flame radius r(f) approximately from 1 to 5 mm for hydrogen, methane and propane mixtures, in order to make clear a method for improving combustion of micro-meso scale flames. Macro-scale laminar flames with r(f) &gt; 7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity (S-L0 = 25 cm/s) for unstretched flames and different equivalence ratios phi. The radius r(f) and the burning velocity S-Ll of meso-scale flames are estimated by using sequential schlieren images recorded under appropriate ignition conditions. It is found that S-Ll of hydrogen and methane premixed meso-scale flames at the same r(f) or the Karlovitz number Ka shows a tendency to increase with decreasing phi, whereas S-Ll of propane flames increases with phi. However, S-Ll tends to decrease with the Lewis number Le and the Markstein number Ma, irrespective of the type of fuel and phi. It also becomes clear that the optimum flame size and Ka to improve the burning velocity exist for some mixtures depending on Le and fuel types. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

DOI： 10.1016/j.proci.2012.08.007

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This Stlldy Is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale spherical laminar flames in the range of flame radius r f approximately from I to 5 mm for hydrogen-oxygen mixtures diluted with Ar. CO 2 or N 2. in order to make clear an influence of dilution gas on burning velocities of meso-scale flames and a method for improving combustion of niicro-mcso scale flames. Macro-scale laminar flames w ith r f&gt;7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity for unstretched flames and different equivalence ratios θ(=O.5̃4).9). The radius and the burning velocity of ineso-scale flames are obtained by using sequential schlicrcn images recorded under appropriate ignition conditions It is found iiiat the burning velocities of meso-scale flames for CO 2 diluted mixtures (θ=0.5̃0.9) have a tendency to decrease with increasing r f, and approach those of macro-scale flames. Such a trend, however, can not be seen for Ar- as well as N2- diluted mixtures of hydrogen and oxygen with 0.7 and 0.9. whose burning velocity of meso-scale flames can not be explained based on that of macro-scale Ilamnes. This suggests that mnmcro-meso scale flames have the optimum site amid Karlovitz number to improve the burning velocity, depending on dilution gas types in addition to and fuel types. © 2012 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaib.78.1640

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This study is performed to experimentally examine the fundamental burning velocity characteristics of meso-scale spherical laminar flames in the range of flame radius <i>r_f</i> approximately from 1 to 5 mm for hydrogen-oxygen mixtures diluted with Ar, CO₂ or N₂, in order to make clear an influence of dilution gas on burning velocities of meso-scale flames and a method for improving combustion of micro-meso scale flames. Macro-scale laminar flames with <i>r_f</i> > 7 mm are also examined for comparison. The mixtures have nearly the same laminar burning velocity for unstretched flames and different equivalence ratios <i>&phi;</i>(=0.5-0.9). The radius and the burning velocity of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocities of meso-scale flames for CO₂ diluted mixtures (<i>&phi;</i>=0.5-0.9) have a tendency to decrease with increasing <i>r_f</i>, and approach those of macro-scale flames. Such a trend, however, can not be seen for Ar- as well as N₂- diluted mixtures of hydrogen and oxygen with <i>&phi;</i>=0.7 and 0.9, whose burning velocity of meso-scale flames can not be explained based on that of macro-scale flames. This suggests that micro-meso scale flames have the optimum size and Karlovitz number to improve the burning velocity, depending on dilution gas types in addition to <i>&phi;</i> and fuel types.

DOI： 10.1299/kikaib.78.1640

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This experimental study was performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition, in order to clarify basically the influence of the addition of dilution gas to hydrogen mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different dilution gas types and equivalence ratios were prepared. A two-dimensional sequential laser tomography technique was used to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity <i>S_F</i>, curvature and stretch of turbulent flames were quantitatively measured as some of the key parameters of local flame properties on turbulent flames. Additionally, the Markstein number <i>Ma</i> was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured <i>S_F</i> with respect to dilution gas types and equivalence ratios corresponded well its turbulent burning velocity. The trend of the obtained <i>Ma</i> could explain the <i>S_F</i> of turbulent flames only qualitatively. The local burning velocity at the part of turbulent flames with positive stretch and curvature due to the <i>Ma</i>, <i>S_Lt</i> , attempted to be estimated quantitatively. As a result, a quantitative relationship between the estimated <i>S_Lt</i> and the <i>S_F</i> at positive stretch and curvature of turbulent flames could be observed only for mixtures with <i>Le</i> > 1 or <i>Ma</i> > 0, regardless of dilution gas types.

DOI： 10.1299/kikaib.78.162

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This study has examined the influence of the addition of hydrogen to propane mixtures on its local burning velocity. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δ<SUB>H</SUB> and equivalence ratios Φ(0.8∼1.4) were prepared. A two-dimensional sequential laser tomography technique was used to obtain the temporal and statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity <I>S<SUB>F</SUB></I> and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. The Markstein number <I>Ma</I> was also obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It became clear that the trends of the mean values of measured <I>S<SUB>F</SUB></I> with respect to δ<SUB>H</SUB> and Φ gave good agreement with the turbulent burning velocity. The trends of <I>Ma</I> with respect to δ<SUB>H</SUB>, Φ and fuel types could also explain qualitatively the local burning velocity and turbulent burning velocity.

DOI： 10.1299/jee.6.700

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This study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u'/S-L0=1.4), in order to clarify basically the influence of the addition of hydrogen to methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen delta(H) are prepared. A two-dimensional sequential laser tomography technique is used to obtain the relationship between the flame shape and the flame displacement. The local flame displacement velocity S-F is quantitatively obtained as the key parameters of the turbulent combustion. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effects of positive stretch and curvature on burning velocity. It was found that the trends of the mean values of measured S-F with respect to delta(H), the total equivalence ratio Phi and fuel types corresponded well its turbulent burning velocity. The trend of the obtained Ma could explain the local burning velocity of turbulent flames only qualitatively. Based on the Ma, the local burning velocity at the part of turbulent flames with positive stretch and curvature, S-Lt, is estimated quantitatively. As a result, a quantitative relationship between the estimated S-Lt and the S-F at positive stretch and curvature of turbulent flames could be observed for mixtures with increasing the Lewis number.

DOI： 10.1115/ajtec2011-44039

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Understanding of the burning velocity for micro-scale flames is inevitable in the improved design of micro-combustors for miniaturized power supplies, and also useful for modeling local burning characteristics of turbulent flames. The present study is performed to examine experimentally the burning velocity characteristics of micro-scale spherical laminar flames in the range of flame radius <i>r_f</i> approximately from 1 to 5 mm for methane and propane mixtures as hydrocarbon fuel, and also macro-scale laminar flames with <i>r_f</i> >7 mm for comparison. The mixtures have nearly the same laminar burning velocity at so-called unstretched flames and different equivalence ratio <i>&phi;</i> (<i>&phi;</i>=0.8-1.0 for CH₄, <i>&phi;</i>=1.0-1.4 for C₃H₈). The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocity of all micro-scale flames has a tendency to increase with increasing <i>r_f</i> , and approach that of macro-scale flames. The propane mixture with <i>&phi;</i>1.4 , however, shows that the burning velocity of micro-scale flames can not be explained based on that of macro-scale flames. This suggests that the optimum size and Karlovitz number to improve the burning velocity are existed, depending on <i>&phi;</i> and fuel types.

DOI： 10.1299/kikaib.77.376

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Comprehension of the burning velocity for micro-scale flames is inevitable in the improved design of micro-combustors for miniaturized power supplies. The present study is performed to examine experimentally the burning velocity characteristics of hydrogen-premixed micro-scale spherical laminar flames in the range of flame radius <i>r_f</i> < 5 mm, and also macro-scale laminar flames with <i>r_f</i> > 7 mm for comparison. The mixtures have nearly the laminar burning velocity <i>S_L0</i> at so-called unstretched flames with different equivalence ratios (&phi;=0.3-1.2). In this experiment, the values of the <i>S_L0</i> are fixed at approximately 15, 25 and 35 cm/s, in order to examine the influence of characteristic chemical reaction time on micro-scale spherical laminar flames. The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. The results show that the burning velocities of micro-scale flames with &phi;=0.3 and 0.5 or 1.2 have a tendency to decrease or increase with increasing <i>r_f</i> and approach that of macro-scale flames, but such a trend can not be seen for &phi;0.7 and 0.9 micro-scale flames, irrespective of <i>S_L0</i>. It is also found that the optimum size and Karlovitz number to improve the burning velocity are existed for &phi;0.7 and 0.9 micro-scale flames, irrespective of <i>S_L0</i>.

DOI： 10.1299/kikaib.77.168

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This study has examined the influence of the addition of hydrogen to propane mixtures on its local burning velocity. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δ_H and equivalence ratios Φ(0.8〜1.4) were prepared. A two-dimensional sequential laser tomography technique was used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. The Markstein number Ma was also obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It became clear that the trends of the mean values of measured S_F with respect to δ_H and Φ gave good agreement with the turbulent burning velocity. The trends of Ma with respect to δ_H, Φ and fuel types could also explain qualitatively the local burning velocity and turbulent burning velocity.

DOI： 10.1299/kikaib.75.760_2550

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This study has examined the influence of the addition of hydrogen to propane mixtures on its local burning velocity. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δHand equivalence ratios ø(0.8∼1.4) were prepared. A two-dimensional sequential laser tomography technique was used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity SF and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. The Markstein number Ma was also obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It became clear that the trends of the mean values of measured SF with respect to δH and Φ1 gave good agreement with the turbulent burning velocity. The trends of Ma with respect to 5,Φ and fuel types could also explain qualitatively the local burning velocity and turbulent burning velocity.

DOI： 10.1299/kikaib.75.760_2550

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

In this paper, we present some experimental and analytical model results of two-component fuel mixtures of methane, propane and hydrogen. Experimentally obtained turbulent burning velocity S(T) for outwardly propagating spherical lean turbulent premixed flames is examined with an algebraic flame surface wrinkling reaction model using 1) mean local burning velocity, and 2) the critical chemical time scale from the leading edge model by Zel&apos;dovich and Frank-Kamenetskii. Based on the latter approach, the time scale that characterizes the effects of preferential diffusion phenomenon in critically curved spherical flames is incorporated into the reaction model. For this, a proposed simple linear model is used for estimating the effective Lewis number of the two-component fuel (CH(4)H(2) and C(3)H(8)-H(2))/Air mixtures. in general, both approaches are effective ways in achieving qualitatively consistent ST trends for both mixtures. However, in the second approach, model predictions show large S(T) deviation especially at high turbulence. This I may be attributed to the use of approximate values of activation temperature and for the use of the effective Lewis number of both mixtures based on the simple linear model. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijhydene.2009.09.036

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Language：Japanese   Publisher：水素エネルギ-協会  

A series of experiments on the control and the prevention of the propagation of hydrogen combustion by water spray were carried out to decrease the damage caused by the combustion of hydrogen. The hydrogen-air mixture mainly 16% or 8% hydrogen concentration was supplied in an acrylic resin duct (150mmx150mmx750mm) and ignited. The average particle size of the sprayed water was 16μm and sprayed with a flow rate of 0,21/min. Inert gas was added in the duct to control the combustion if necessary. The pressure and temperature during the combustion in the duct were measured. The magnitude of the pressure change during the combustion decreased by using water spray. The propagation of combustion was prevented by using high density water spray and helium.

DOI： 10.50988/hess.34.3_23

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

This experimental study is performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition (u'/S-L0 = 1.4), in order to clarify basically the influence of the addition of hydrogen to lean and rich methane or propane mixtures on its local burning velocity. The mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen delta(H) are prepared. A two-dimensional sequential laser tomography technique is used to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. Some of the key parameters of local flame properties quantitatively measured are the local flame displacement velocity S-F, curvature and stretch of turbulent flames. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured S-F with respect to delta(H), the total equivalence ratio Phi and fuel types corresponded well its turbulent burning velocity. The trend of the obtained Ma could explain the S-F of turbulent flames only qualitatively. The local burning velocity at the part of turbulent flames with positive stretch and curvature using this Ma, S-Lt, attempted to be estimated quantitatively. As a result, a quantitative relationship between the estimated S-Lt and the S-F at positive stretch and curvature of turbulent flames could be observed only for mixtures with Le &gt; 1 or Ma &gt; 0.

DOI： 10.1299/jtst.4.190

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

This study is made to attempt to establish a prediction model of tubulent burning velocity for hydrogen mixtures based on the local burning velocity of turbulent flames instead of laminar burning velocity. The turbulent burning velocity characteristics of the specific mixtures having the same laminar burning velocity S_<L0> with different equivalence ratio φ are examined experimentally at a constant volume vessel (φ=0.3〜3.6 at the maximum, S_<L0>=10〜50cm/s). The mean local burning velocity S_L of turbulent flames is also determined by using our proposed method which takes the preferential diffusion effect into consideration. It is found that the lower the equivalence ratio is, the higher the turbulent burning velocity becomes and the more extended the quenching limit is. S_L/S_<L0> for each φ of hydrogen mixture has a tendency to increase or decrease with u'/S_<L0>, as compared with hydrocarbon mixtures. Therefore, the S_L for hydrogen mixtures needs to take account of u' as well as φ and S_<L0>. The quantitative accuracy of our proposed model for hydrogen mixtures is improved by using S_L based on φ and u'/S_<L0>.

DOI： 10.1299/kikaib.74.2229

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST AERONAUT ASTRONAUT  

To clarify the turbulent burning velocity of hydrogen in the presence of hydrocarbons, a two-component fuel mixture of hydrogen, methane, and propane was considered. Both hydrocarbon fuel-lean and fuel-rich mixtures were prepared while keeping the laminar burning velocity approximately constant. Even though the laminar burning velocities were approximately the same, a distinct difference in the measured turbulent burning velocity at the same turbulence intensity is observed, depending on the addition of hydrocarbon, the equivalence ratio, and the kind of hydrocarbon. The burning velocities of lean mixtures changed almost monotonically as the rate of addition changed, whereas the burning velocities of the rich mixtures showed no such tendency. This trend can be explained qualitatively based on the mean local burning velocity, which is estimated by taking into account the preferential diffusion effect for each fuel component.

DOI： 10.2514/1.23560

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The influence of the addition of hydrogen to methane mixtures on its local burning velocity has been investigated directly. Hydrogen added lean and rich methane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen &delta;<I><SUB>H</SUB></I> were prepared.A two-dimensional sequential laser tomography technique was used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity <I>S<SUB>F</SUB></I> and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. Additionally, the Markstein number <I>Ma</I> was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured <I>S<SUB>F</SUB></I> with respect to &delta;<I><SUB>H</SUB></I> and the equivalence ratio &phi; corresponded well the turbulent burning velocity. The trends of <I>Ma</I> with respect to &delta;<I><SUB>H</SUB></I> and &phi; could possibly explain qualitatively the local burning velocity and turbulent burning velocity.

DOI： 10.1299/kikaib.73.2579

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This study is attempted to establish a prediction model of turbulent burning velocity for hydrogen mixtures based on the local burning velocity of turbulent flames instead of laminar burning velocity. The turbulent burning velocity characteristics of the specific mixtures having the same laminar burning velocity SL0 with different equivalence ratio φ are examined experimentally at a constant volume vessel (φ=mainly 0.3-1.4, SL0=10-50 cm/s). The mean local burning velocity SL of turbulent flames is also estimated by using our proposed method which takes the preferential diffusion effect into consideration. It is found that the lower the equivalence ratio is, the higher the turbulent burning velocity becomes and the more extended the quenching limit is. SL/SL0 for each φ of hydrogen mixture has a tendency to increase or decrease with u&#039;/S L0, as compared with hydrocarbon mixtures. Therefore, the S L for hydrogen mixtures needs to take account of u&#039; as well as φ and SL0. The quantitative accuracy of our proposed model for hydrogen mixtures is improved by using SL based on φ and u&#039;/S L0.

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

The influence of the addition of hydrogen to methane mixtures on its local burning velocity has been investigated directly. Hydrogen added lean and rich methane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen δH were prepared. A two-dimensional sequential laser tomography technique was used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity SF and curvature of turbulent flames were quantitatively measured as the key parameters on turbulent combustion. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the trends of the mean values of measured SF with respect to δH and the equivalence ratio φ corresponded well the turbulent burning velocity. The trends of Ma with respect to δH and φ could possibly explain qualitatively the local burning velocity and turbulent burning velocity.

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：水素エネルギ-協会  

One of the dangers latent in the hydrogen society is that hydrogen has much larger possible for the deflagration to detonation transitions (DDT) than ordinary hydrocarbon fuels, because of its higher laminar burning velocity and wider detonability limits. DDT may easier occur in a long and narrow space such as tunnels and ducts. It is important to be developed for predicting and preventing serious fire or explosion, and detonation. The present study is performed to investigate experimentally the deflagration flame of hydrogen mixtures propagating in a tunnel simulated channel (10x10x2440 mm) with special attention to flame front configurations and speeds, because of DDT caused mostly by enhancement of the flame front propagation. Hydrogen-air mixtures with 0.3~0.4 of equivalence ratio and hydrogen mixtures having nearly the same laminar burning velocity <i>S</i>_<i>LO</i> with ɸ=0.4~0.7 are prepared, in order to examine effects of the laminar burning velocity and the equivalence ratio on enhancement of the flame speeds. The flame shape and speeds are obtained by using sequential schlieren images recorded under conditions with the center ignition and the both-ends open of channel. The results show that the flame propagation is oscillating due to acoustic instability. Some flames also shows to begin to accelerate after traveling a distance, so that the factors of flame acceleration are discussed.

DOI： 10.50988/hess.32.3_24

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

The effect of positive stretch on the local flame properties of turbulent propagating flames in the flamelet regime was investigated experimentally for methane-, hydrogen- and propane-air mixtures with lean and rich having nearly the same laminar burning velocity (S-L0=25cm/s). The ratio of the turbulence intensity u' to S-L0 was varied as 1.4 and 2. A 2D laser tomography technique was used to obtain the temporal local flame configuration and movement in a constant-volume vessel. Some of the key parameters of turbulent combustion quantitatively measured are the local flame displacement velocity S-F, curvature and stretch of turbulent flames. Additionally, the Markstein number Ma was obtained from outwardly propagating spherical laminar flames, in order to examine the effect of positive stretch on burning velocity. It was found that the obtained S-F was distributed over a wide range with flame stretch as well as curvature, even for low turbulence (u'/S-L0=1.4). There also existed a good relationship between S-F and the turbulent burning velocity. A quantitative relationship between Ma based on laminar flames and the S-F for positive stretch and curvature of turbulent flames could be observed only for mixtures with Lewis number Le greater about one.

DOI： 10.1299/jtst.2.268

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

Comprehension of the burning velocity for micro-scale flames is inevitable in the improved design of micro-combustors for miniaturized power supplies, and also useful for modeling local burning characteristics of turbulent flames. The present study is performed to examine experimentally the burning velocity characteristics of lean hydrogen-premixed micro-scale spherical laminar flames in the range of flame radius γ_f approximately from 1 to 5mm, and also macro-scale laminar flames with γ_f>7mm for comparison. The mixtures have nearly the same laminar burning velocity at socalled unstretched flames and different equivalence ratio φ which is varied from 0.3 to 0.9. The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. The results show that the burning velocity of micro-scale flames with φ=0.3 and 0.5 has a tendency to decrease with increasing γ_f and approach that of macro-scale flames, but such a trend can not be seen for φ0.9 micro-scale flames. This suggests that burning velocity characteristics of micro-scale flames can not be always explained based on that of macro-scale flames. In the micro-scale flames, the optimum size and stretch of flames to improve the burning velocity are also found to exist, depending on φ.

DOI： 10.1299/kikaib.72.3166

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

This study is made to attempt to establish a prediction model of turbulent burning velocity for hydrogen mixtures based on the local burning velocity of turbulent flames instead of laminar burning velocity. The turbulent burning velocity characteristics of the specific mixtures having the same laminar burning velocity SL0 with different equivalence ratio φ are examined experimentally at a constant volume vessel (φ=mainly 0.3∼1.4, S L0=10∼50 cm/s). The mean local burning velocity SL of turbulent flames is also determined by using our proposed method which takes the preferential diffusion effect into consideration. It is found that the lower the equivalence ratio is, the higher the turbulent burning velocity becomes and the more extended the quenching limit is. SL/SL0 for each φ of hydrogen mixture has a tendency to increase or decrease with u&#039;/S L0, as compared with hydrocarbon mixtures. Therefore, the S L for hydrogen mixtures needs to take account of u&#039; as well as φ and SL0.The quantitative accuracy of our proposed model for hydrogen mixtures is improved by using SL based on φ and u&#039;/S L0.

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Comprehension of the burning velocity for micro-scale flames is inevitable in the improved design of micro-combustors for miniaturized power supplies, and also useful for modeling local burning characteristics of turbulent flames. The present study is performed to examine experimentally the burning velocity characteristics of lean hydrogen-premixed micro-scale spherical laminar flames in the range of flame radius &gamma;<SUB><I>f</I></SUB> approximately from 1 to 5 mm, and also macro-scale laminar flames with &gamma;<SUB><I>f</I></SUB>>7 mm for comparison. The mixtures have nearly the same laminar burning velocity at socalled unstretched flames and different equivalence ratio &phi; which is varied from. 0.3 to 0.9. The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. The results show that the burning velocity of micro-scale flames with &phi;=0.3 and 0.5 has a tendency to decrease with increasing &gamma;<SUB><I>f</I></SUB> and approach that of macro-scale flames, but such a trend can not be seen for &phi; 0.9 micro-scale flames. This suggests that burning velocity characteristics of micro-scale flames can not be always explained based on that of macro-scale flames. In the micro-scale flames, the optimum size and stretch of flames to improve the burning velocity are also found to exist, depending on &phi;.

DOI： 10.1299/kikaib.72.3166

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Hydrogen Energy Systems Society of Japan  

One of the dangers latent in the hydrogen society is that hydrogen has wider flammable range and smaller minimum ignition energy than hydrocarbons. Elucidating the mechanisms of turbulent combustion and establishing a model of turbulent burning velocity for hydrogen mixtures are expected to be developed for prediction and prevention of serious fire or explosion. In our previous studies, the local burning velocity of turbulent flames could be changed from the laminar burning velocity caused by the preferential diffusion effect, and play an important role in the turbulent burning velocity. The present study is performed to investigate directly the local flame properties of hydrogen premixed turbulent flames at the weak turbulence condition. Lean and rich hydrogen mixtures having nearly the same laminar burning velocity are prepared. Propane fueled mixtures are also examined for comparison. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement. In order to examine the local burning velocity, the local flame displacement velocity <i>SF</i> is quantitatively obtained as the key parameters of the turbulent combustion. The obtained <i>SF</i> is also discussed by the concept of the Markstein number as well as the preferential diffusion effect.

DOI： 10.50988/hess.31.1_66

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：自動車技術会  

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：Hydrogen Energy Systems Society of Japan  

It is important that the effect of dilution gas on the turbulent burning velocity of hydrogen mixtures is elucidated to develop modern hydrogen combustion devices. In our previous studies, the preferential diffusion effect was made clear to play an important role in the turbulent combustion characteristics, affecting the local burning velocity, where nitrogen was added as a dilution gas to several fuel/air mixtures. The present study is performed to obtain experimentally the turbulent combustion characteristics of dilution gas added lean hydrogen mixtures with special attention to the local burning velocity of turbulent flame, in order to elucidate the mechanism of turbulent combustion of those mixtures. In this study, the turbulent burning velocities of the prepared mixtures, whose laminar burning velocity were nearly the same and the equivalence ratio were varied, w ere experimentally investigated. Where, argon, helium and carbon dioxide in addition to nitrogen were adopted as dilution gas. It is found that carbon dioxide added mixtures show larger turbulent burning velocities than that of nitrogen added mixtures at the same equivalence ratio. On the contrary, helium added mixtures show very smaller turbulent burning velocities. Those characteristics are discussed in preferential diffusion effect, turbulent flame-front configurations and Markstein number.

DOI： 10.50988/hess.30.2_58

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：自動車技術会  

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The local flame properties of turbulent propagating flames with respect to the ratio of the turbulence intensity to the laminar burning velocity <i>u&rsquo;/S_L0</i> in the flamelet regime have been investigated experimentally for methane, propane and hydrogen mixtures having nearly the same laminar burning velocity with different equivalence ratios. <i>u&rsquo;/S_L0</i> is varied as 1.4 and 2.3. A 2D laser tomography technique is used to obtain the flame configuration and movement in a constant-volume vessel and then the local flame displacement velocity <i>S_F</i> is quantitatively measured as a key parameter of turbulent combustion. As a result, the mean value of <i>S_F</i> shows to be affected by <i>u&rsquo;/S_L0</i>, which indicates a relation between the characteristic chemical reaction time and the characteristic flow time, to some extent, especially for leaner and richer mixtures. <i>S_F</i> is also discussed by the concept of preferential diffusion and Markstein number which can affect the local burning velocity characteristics.

DOI： 10.1299/jsmeb.48.164

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Comprehension of the turbulent burning velocity for lean hydrogen mixtures is inevitable in the improved design of hydrogen engines. The present study is performed to examine experimentally the turbulent burning velocity of lean hydrogen mixtures whose laminar burning velocity <I>S<SUB>L0</SUB></I> and equivalence ratio &phi; are varied extensively from 15 to 35 cm/s and approximately 0.9 to 0.3, respectively. The measured turbulent burning velocities at the same turbulence intensity show to increase as &phi; decreases until about 0.5. Those, however, does not show such increase when &phi; becomes lower than about 0.5, regardless of <I>S<SUB>L0</SUB></I>. This phenomenon is discussed by the observation of turbulent flame structure and the estimation of Markstein number. The estimation of the mean local burning velocity of the turbulent flame is made also taking account of the preferential diffusion. It is found that their tendencies with &phi; is changed when &phi; becomes about 0.5.

DOI： 10.1299/kikaib.71.275

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

In order to clarify the turbulent burning velocity of hydrogen mixtures including hydrocarbons as a multicomponent fuel mixture, both lean and rich hydrocarbon(methane and propane)-added hydrogen mixtures as two-component fuel mixtures were prepared while maintaining the laminar burning velocity approximately constant. A distinct difference in the measured turbulent burning velocity at the same turbulence intensity is observed depending on the additional rate of hydrocarbon, the equivalence ratio and the kind of hydrocarbon, even the laminar burning velocities are approximately the same. The burning velocities of lean mixtures change almost monotonously as the rate of addition changes, whereas the burning velocities of the rich mixtures show no such tendency. This trend can be explained qualitatively based on the mean local burning velocity, which is estimated by taking into account the preferential diffusion effect for each fuel component. In addition, a model of turbulent burning velocity proposed for single-component fuel mixtures can be applied to hydrocarbon-added lean hydrogen mixtures by considering the estimated mean local burning velocity of each fuel. © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

DOI： 10.2514/6.2003-4638

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The present study is performed to examine experimentally the turbulent burning velocity characteristics of lean hydrogen mixtures with attention to the local burning velocity. The special mixtures, having nearly the same laminar burning velocity with different equivalence ratios D&amp;=0.3-0.9, are prepared. The measured turbulent burning velocities at the same turbulence intensity show to large increase as D; decreases until about 0.5. Those, however, do not show such large increase when D&amp; becomes lower than about 0.5. This phenomenon is discussed by the estimated mean local burning velocity taking account of preferential diffusion, tomograms of turbulent flames and estimated Markstein number. Copyright © 2003 Society of Automotive Engineers of Japan, Inc.

DOI： 10.4271/2003-01-1773

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In our previous studies, the turbulent burning velocities of several mixtures having nearly the same laminar burning velocity were experimentally investigated. As a result, it becomes clear that the mean local burning velocity of turbulent flame can be changed from the original laminar burning velocity depending on the equivalence ratio, caused by the diffusional properties of reactants, i.e., the preferential diffusion effect. This change affects substantially the turbulent burning velocity characteristics. In order to clarify the influence of the local burning velocity on the turbulent burning velocity, an attempt is made in this study to examine directly the local flame propagation properties of premixed turbulent flames under weak turbulence condition where the continuous and thin reaction sheet is predominant. Several mixtures having nearly the same laminar burning velocity are prepared for experiments by adding nitrogen to hydrogen-air, methane-air and propane-air mixtures where the equivalence ratio is varied. A laser tomography technique is used to obtain the sequential two-dimensional flame shape and motion, and quantitative analyses are performed. Where, the local flame front curvature and the local flame displacement velocity are quantitatively obtained as the key parameters of the turbulent combustion. In the first place, the observation of sequential flame tomograms shows that the turbulent flame front can be classified into the active and inactive parts depending on its geometric configuration. In the next place, the local burning velocity and the local curvature are obtained directly by the flame front movement. The local flame displacement velocities of the turbulent flame are found to be not a constant value as the laminar burning velocity, but to be distributed over a wide range depending on the local curvature of the turbulent flame. In addition, the mean local flame displacement velocities of the hydrogen and methane mixtures have a tendency to become larger as decreasing its equivalence ratio, whereas those of the propane mixtures become smaller, even in Fig. A-1. These experimental results seem to be in disagreement with the conventional concept of turbulent burning velocity, where the local burning velocity is likely to be equal to the original laminar burning velocity under such weak turbulence condition. The discussion on the influence of preferential diffusion and Markstein number on the local flame displacement velocity is also made.[figure]

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In our previous works, the mean local burning velocity turned out to be changed from the original laminar burning velocity due to the preferential diffusion effect and it was found to be an important factor as dominating the turbulent burning velocity. In the present study, an attempt is made to investigate directly the local propagation characteristics of methane and propane premixed turbulent flames in the wrinkled laminar flame region. A laser tomography technique is used to obtain the local flame configuration and movement, and quantitative analyses are performed. As a result, the estimated local flame displacement velocities are found to be distributed over a wide range and to be dependent on the local curvature of the turbulent flame. In addition, its mean value of the methane mixture has a tendency to become larger as decreasing its equivalence ratio, whereas that of the propane mixture becomes smaller.

DOI： 10.1299/jsmeb.46.92

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：COMBUSTION INST  

In our previous works, the mean local burning velocity turned out to be changed from the original laminar burning velocity due to the preferential diffusion effect, and it was found to be an important factor dominating the turbulent burning velocity The present study investigates directly the local flame propagation properties of methane, propane, and hydrogen premixed turbulent flames in the weak turbulence region. A laser tomography technique is used to obtain the temporal local flame configuration and movement in a constant-volume vessel, and quantitative analyses are performed. The local flame-front curvature and the local flame displacement velocity SF are quantitatively obtained as the key parameters of the turbulent combustion. First, the observation of sequential flame tomograms shows that the turbulent flame front seems to be classified into active and inactive parts depending on its geometric configuration. Next, the values Of SF are found to be distributed over a wide range and to be dependent on the local curvature of the turbulent flame. In addition, the values of SF for the methane and hydrogen mixtures have a tendency to become larger with decreasing equivalence ratio, whereas those for the propane mixture become smaller. We discuss also the influence of preferential diffusion and Markstein number on the local flame displacement velocity.

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

In our previous works, the mean local burning velocity turned out to be changed from the original laminar burning velocity due to the preferential diffusion effect, and it was found to be an important factor dominating the turbulent burning velocity. The present study investigates directly the local flame propagation properties of methane, propane, and hydrogen premixed turbulent flames in the weak turbulence region. A laser tomography technique is used to obtain the temporal local flame configuration and movement in a constant-volume vessel, and quantitative analyses are performed. The local flame-front curvature and the local flame displacement velocity SF are quantitatively obtained as the key parameters of the turbulent combustion. First, the observation of sequential flame tomograms shows that the turbulent flame front seems to be classified into active and inactive parts depending on its geometric configuration. Next, the values of SF are found to be distributed over a wide range and to be dependent on the local curvature of the turbulent flame. In addition, the values of SF for the methane and hydrogen mixtures have a tendency to become larger with decreasing equivalence ratio, whereas those for the propane mixture become smaller. We discuss also the influence of preferential diffusion and Markstein number on the local flame displacement velocity.

DOI： 10.1016/S1540-7489(02)80225-5

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In order to clarify the turbulent burning velocity of multi-component fuel mixtures, both lean and rich two-component fuel mixtures, in which methane, propane and hydrogen were used as fuels, were prepared while maintaining the laminar burning velocity approximately constant. A distinct difference in the measured turbulent burning velocity at the same turbulence intensity is observed for two-component fuel mixtures having different addition rates of fuel, even the laminar burning velocities are approximately the same. The burning velocities of lean mixtures change almost constantly as the rate of addition changes, whereas the burning velocities of the rich mixtures show no such tendency. This trend can be explained qualitatively based on the mean local burning velocity, which is estimated by taking into account the preferential diffusion effect for each fuel component. In addition, a model of turbulent burning velocity proposed for single-component fuel mixtures may be applied to two-component fuel mixtures by considering the estimated mean local burning velocity of each fuel.

DOI： 10.1299/jsmeb.45.355

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Japan Society of Mechanical Engineers  

It is well known that the combustion in SI engines typically takes place in the wrinkled laminar flame region. According to the concept of the conventional models of turbulent burning velocity in this turbulence condition, the ratio of the turbulent burning velocity to the local burning velocity is proportional to the ratio of the turbulent flame surface area to the laminar flame surface area. The area ratio is well approximated to be proportional to the ratio of the turbulence intensity to the local burning velocity, which is usually taken to be equal to the original laminar burning velocity. However, in our previous works, the mean local burning velocity turned out to be changed from the original laminar burning velocity due to the preferential diffusion effect and it was found to be an important factor as dominating the turbulent burning velocity. This fact seems to contradict the concept of the conventional models. In the present study, an attempt is made to investigate directly the local propagation characteristics of methane and propane premixed turbulent flames in the wrinkled laminar flame region. A laser tomography technique is used to obtain the local flame configuration and movement. And quantitative analyses are performed. The local flame front curvature 1/r and the local flame burning velocity S_F are quantitatively obtained as the key parameters of the turbulent combustion. In the first place, the observation of sequential flame tomograms shows that the turbulent flame front can be classified into the active and inactive part depending on its geometric configuration. In the next place, the values of S_F are obtained directly from the sequential flame tomograms as the local burning velocity. Figure shows a typical probability density function (pdf) of the acquired 1/r normalized by the preheat zone thickness η_o, and a distribution of the acquired S_F normalized by S_<LO> for the laminar flame and the turbulent flame, respectively. It is found that the values of S_F of the turbulent flame are not a constant value as S_<LO>, but to be distributed over a wide range depending on the local curvature of the turbulent flame. In addition, the mean value of S_F for the methane mixture has a tendency to become larger as decreasing its equivalence ratio, whereas that of the propane mixture to become smaller.

DOI： 10.1299/jmsesdm.01.204.32

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An attempt is made to examine the configuration and propagation characteristics of premixed turbulent flame in a weak turbulence region. A laser tomography technique is used to obtain the flame shape, and quantitative analysis is performed. It is found that the turbulent flame front can be classified into the active and the inactive part for the flame propagation, where the former is the convex part of flame toward the unburned mixture and the latter is toward the burned gas. In this paper, the local burning velocity and the local flame front curvature are determined directly by sequential flame tomograms. (C) 2001 Society of Automotive Engineers of Japan, Inc. and Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0389-4304(01)00083-2

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

In order to clarify the turbulent burning velocity of the multi-component fuel mixtures, the lean and rich two-component fuel mixtures, where methane, propane and hydrogen were used as fuels, were prepared keeping the laminar burning velocity nearly the same value. Clear difference in the measured turbulent burning velocity at the same turbulence intensity can be seen among the two-component fuel mixtures with different addition rate of fuel, even under nearly the same laminar burning velocity. The burning velocities of lean mixtures change almost monotonously as addition rate changes, those of rich mixtures, however, do not show such a monotony. These phenomena can be explained qualitatively from the local burning velocities, estimated by taking account of the preferential diffusion effect for each fuel component. In addition, a model of turbulent burning velocity proposed for the one-component fuel mixtures can possibly be applied to the two-component fuel mixtures by using the estimated local burning velocity of each fuel.

DOI： 10.1299/kikaib.66.651_3021

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

In our previous study, it was found that the mean local burning velocity turned out to be changed from the original laminar burning velocity due to the preferential diffusion effect and it's quantitative value was estimated experimentally. In the present study, the configuration and propagation characteristics of premixed turbulent flames in a constant-volume vessel are investigated in the wrinkled laminar flame region. A laser tomography technique is used to obtain the flame shape, and quantitative analyses are performed. The obtained tomograms show that the turbulent flame surface area depends almost only on the turbulence intensity. In addition, the local burning velocities for several mixtures are determined directly from the flame front movement. As a result, the local flame propagation velocities are found to be distributed over a wide range and to be dependent on the local curvature of the turbulent flame.

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Authorship：Corresponding author   Language：Japanese   Publisher：防衛庁技術研究本部  

資料形態 : テキストデータ プレーンテキスト

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Language：English   Publishing type：Research paper (bulletin of university, research institution)   Publisher：Kyushu University  

In our previous works, the preferential diffusion effect was found to play an important role in premixed turbulent combustion characteristics, where N2 was added as an inert gas to several Fuel/Oxygen mixtures. In this study, the inert gas is changed to Ar, He and CO2, and the relationship between the turbulent burning velocity and the diffusion coefficient of each inert gas in the multi-component mixture is examined experimentally. As a result, Ar and CO2 added mixtures show slightly larger turbulent burning velocities than that of N2 added mixtures. On the contrary, He added mixtures show very smaller turbulent burning velocities at the same equivalence ratio. These characteristics are discussed in connection with each diffusion coefficient of fuel, oxygen and inert gas in multi-component system.

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

The thire paper examined the effect of turbulence by combustion causes to heat loss. But in real gasoline engine, the air fuel mixture, which inhaled it in cylinder includes initial turbulence. Therefore effect of initial turbulence of mixture was examined to estimate heat loss of gasoline engine in this paper. The initial turbulence was expressed using a simple model in which the momentum of turbulence damps when turbulence moves from unburned gas to burned gas. The expression to estimate heat loss is expressed as next by using the model. [numerical formula] Where the third term expressed the effect of initial turbulence and the coefficient: Cd&ap;0.24 has expressed damping of initial turbulence.

DOI： 10.1299/kikaib.65.2915

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.102.966_275_2

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC MECHANICAL ENGINEERS  

In our previous work, we found that the preferential diffusion in a turbulent flame played an important role in its turbulent combustion characteristics, and estimated the local burning velocity in premixed turbulent combustion experimentally, taking account of the preferential diffusion effect. In this study, a model, which takes the preferential diffusion effect into consideration, is proposed to predict the premixed turbulent burning velocity, using the local burning velocity as a reference instead of the original laminar burning velocity. The model can be explained as fellows. The turbulence affects the turbulent burning velocity by increasing the flame surface area and stretching the flame. Consequently, the turbulent burning velocity and quenching limit are determined by the balance of both effects. The predicted velocities are compared with the measured turbulent burning velocities where the fuel, equivalence ratio and the laminar burning velocity were varied extensively. As a result, quantitative accuracy of this simple model is confirmed.

DOI： 10.1299/jsmeb.41.666

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)   Publisher：Kyushu University  

In order to clarify the mechanism of premixed turbulent combustion, the turbulent burning velocity characteristics for hydrocarbon and hydrogen mixtures are investigated experimentally. The preferential diffusion of turbulent flame is found to play an important role in the turbulent combustion characteristics. The local burning velocity of turbulent flame can possibly change from the original laminar burning velocity caused by the preferential diffusion effect, and is estimated quantitatively by using a proposed experimental method. In addition, a model, which takes the preferential diffusion effect into consideration, is proposed to predict the turbulent burning velocity and the quenching limit, based on the local burning velocity as a reference instead of the original laminar burning velocity. The model can be simply explained as follows. The turbulence affects the turbulent burning velocity by increasing the flame surface area and stretching the flame. Consequently, the turbulent burning velocity and quenching limit are determined by the balance of both effects. The predicted velocities are compared with the measured turbulent burning velocities for mixtures where the fuel, equivalence ratio and the laminar burning velocity were varied extensively. As a result, quantitative accuracy of this simple model is confirmed.

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

In our previous work, we found that the preferential diffusion in a turbulent flame played an important role in its turbulent combustion characteristics, and estimated the local burning velocity in premixed turbulent combustion experimentally, taking account of the preferential diffusion effect. In this study, a model which takes the preferential diffusion effect into consideration, is proposed to predict the premixed turbulent burning velocity, using the local burning velocity as a reference instead of the original laminar burning velocity. The model can be explained as follows. The turbulence affects the turbulent burning velocity by increasing the flame surface area and stretching the flame. Consequently, the turbulent burning velocity and quenching limit are determined by the balancing of both effects. The predicted velocities are compared with the measured turbulent burning velocities such that the fuel, equivalence ratio and laminar burning velocity were varied extensively. As a result, quantitative accuracy of this simple model is confirmed.

DOI： 10.1299/kikaib.63.3477

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publisher：自動車技術会  

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DOI： 10.1016/S0389-4304(96)00029-X

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Recently, in order to establish the lean-burn technique, the structure of non-stoichiometric mixture flames has been studied extensively, as well as that of stoichiometric mixture flames. In those studies, emphasis was placed not only on macroscopic behavior of the turbulent flame but also on microscopic behavior of reactants. The purpose of this paper is to estimate the change in the local burning velocity in turbulent flame. In addition, it is suggested that the turbulent burning velocity and quenching mechanism may be explained regardless of the kind of fuel, when the estimated local burning velocity is used as a reference instead of the laminar burning velocity.

DOI： 10.1016/S0389-4304(96)00029-X

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Mechanical Engineers  

Recently, clarifying the turbulent combustion mechanism of hydrogen mixtures and the local burning mechanism in the turbulent flame has become necessary to establish the lean-burn technique in internal combustion engines in order to protect the environment and save energy. In previous work, experimental results indicated that local burning velocity in turbulent combustion of hydrocarbon mixtures changed from the original laminar burning velocity, and this mechanism was qualitatively explained in terms of the effects of the Lewis number and preferential diffusion. The purpose of this paper is to estimate quantitatively the change in the local burning velocity of the turbulent combustion of hydrogen mixtures, caused by preferential diffusion. In addition, it is suggested that the quenching mechanism can possibly be explained regardless of the kind of fuel, when the estimated local burning velocity is used as a reference instead of the laminar burning velocity.

DOI： 10.1299/kikaib.62.3198

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記事分類: 化学・化学工業--燃料・爆発物--爆発物

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記事分類: 化学・化学工業--燃料・爆発物--爆発物

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記事分類: 化学・化学工業--燃料・爆発物--爆発物

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DOI： 10.1299/jsmecs.2018.56.Prize1

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<p>This study is performed to examine experimentally the influence of dilution gas addition on the burning velocity of ultra-lean hydrogen added propane air premixed meso-scale spherical laminar flames, whose equivalence ratio <i>φ</i> is 0.5 and hydrogen additional rate δ_H is 0.8. N₂ and CO₂, dilution gas, are adopted as simulated EGR gas. The flame radius rf and the burning velocity <i>S_Ll</i> of meso-scale flames in the range of <i>r_f</i> approximately from 1 to 5 mm are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It was found that <i>S_Ll</i> normalized by the laminar burning velocity at the same <i>r_f</i> tends to increase with a simulated EGR gas additional rate.</p>

DOI： 10.1299/jsmeted.2018.0126

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00003565

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<p>The purpose of this study is to develop a low-temperature combustion method to suppress the volatilization of salt or radioactive materials contained in woody wastes. From the standpoint of suppressing the generation of flame in the two-stage combustion method for woody biomass, simulated wastes were incinerated using nitrogen-diluted air. The results of the experiments confirmed that this combustion method is applicable to the incineration of simulated wastes. It is also revealed that the low-temperature combustion could be realized by setting an appropriate dilution rate.</p>

DOI： 10.1299/jsmepes.2016.21.E221

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DOI： 10.1299/jsmecs.2016.54._716-1_

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<p>This study is performed to examine experimentally the effect of H₂ addition on the burning velocity of lean-propane premixed meso-scale spherical laminar flames in the range of flame radius <i>rf</i> approximately from 1 to 5mm. The mixtures having the same laminar burning velocity (<i>S_L0</i>=25cm/s) with different equivalence ratios (ϕ=0.5 and 0.8) and hydrogen additional rates (δ_H=0.0~1.0) are prepared. The <i>rf</i> and the burning velocity <i>S_Ll</i> of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It was found that <i>S_Ll</i> at the same <i>rf</i> tends to increase with δH, where the Lewis number of the mixtures decrease as H₂ is added to mixtures.</p>

DOI： 10.1299/jsmeted.2016.E232

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DOI： 10.1299/jsmecs.2016.54._715-1_

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<p>This experimental study was performed to investigate directly the local flame properties of turbulent propagating flames at the same weak turbulence condition for hydrogen added ultra-lean propane mixtures. A two-dimensional sequential laser tomography technique was applied to obtain the relationship between the flame shape and the flame displacement in a constant-volume vessel. The local flame displacement velocity <i>S_F</i>, curvature and stretch of turbulent flames was quantitatively measured as key parameters of local burning characteristics. It was found that the trends of the mean values of measured <i>S_F</i> ,<i>S_F,m</i> , with respect to hydrogen additional rates correspond well its turbulent burning velocity. The local burning velocity at the part of turbulent flames with positive stretch and curvature due to the <i>Ma</i>, <i>S_Lt</i>, attempted to be estimated quantitatively. As a result, a quantitative relationship between the estimated <i>S_Lt</i> and the <i>S_F,mu</i> at positive stretch and curvature of turbulent flames could be observed only for mixtures with Le>1.</p>

DOI： 10.1299/jsmeted.2016.E234

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<p>This study is aiming to develop an effective and safe direct combustion method for woody wastes containing seawater by applying the two-stage combustion method for woody biomass. Combustion experiments are performed in a small combustor using simulated wastes with moisture contents of 13, 22, and 38 %, which are prepared by saturating woody chips with artificial seawater. No-salt-containing woody chips with moisture content of 17 % are also used for comparison. The experiments revealed that under the two-stage combustion method, the diffusion of salt could be suppressed in the low-temperature range of below 1030 K.</p>

DOI： 10.1299/jsmeted.2016.F212

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<p>The present study is performed to investigate experimentally the deflagration flame of hydrogen-propane-air mixtures propagating in a narrow space simulated channel ( t10×w150×h500 mm ) with special attention to flame acceleration and deceleration. In order to examine the effects of C₃H₈ addition and the grids on the flame propagation speed, the mixtures with different equivalence ratios (ϕ=0.8~1.4) with different propane additional rates (δ_p=0.2~1.0) are prepared. The flame shape and propagation speeds are obtained by using sequential shadowgraph or schlieren images recorded under conditions which are the ignition near the bottom and the upper-end open of channel. It was found that as the additional rate of C₃H₈ increase, the acceleration of flame propagation tends to be suppressed, especially for lean mixtures.</p>

DOI： 10.1299/jsmeted.2016.D111

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This study is performed to examine experimentally the effects of CO_2 as one of EGR gas on the burning velocity of the propane-oxygen-dilution gas premixed meso-scale spherical laminar flames with the flame radius r_f < about 5mm. The mixtures have nearly the same laminar burning velocity (S_<L0>=25cm/s) with different equivalence ratios (φ=0.5-1.4). N_2 is also examined for comparison. The radius and the burning velocity of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It was clear that the burning velocity for the mixture diluted with CO_2 at the same r_f and Karlovitz number has tendency to be larger than that with N_2, except for φ=1.4.

DOI： 10.1299/jsmeted.2015._F141-1_

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The aim of this study is to develop a method of direct combustion that allows safe and effective incineration of difficult-to-process woody industrial wastes which contain sea water or radioactive materials by applying the two-stage combustion method for woody biomass, which were proposed in our previous study. The experiments are conducted using a small combustor. The result clarified the combustion characteristics of cypress chips containing artificial sea water as well as cypress bark chips. In addition, it was confirmed that the combustion of these chips can be controlled over a wide range by changing the amount of air.

DOI： 10.1299/jsmepes.2015.20.297

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DOI： 10.1299/jsmecs.2015.53._1008-1_

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Language：Japanese   Publisher：日本理科教育学会事務局  

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This study is performed to examine experimentally the effects of dilation gas types (N_2, Ar and CO_2) and dilution rates of N_2 on the burning velocity of the stoichiometric methane-oxygen-dilution gas premixed meso-scale spherical laminar flames with the flame radius r_f < approximately 5mm. The radius and the burning velocity of meso-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocity at the same r_f has tendency to increase not only with the mixture diluted with CO_2 at the same laminar burning velocity, but also with decreasing the dilution rate at the stoichiometric mixture.

DOI： 10.1299/jsmeted.2014._I121-1_

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DOI： 10.1299/jsmecs.2013.51._1402-1_

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DOI： 10.1299/jsmecs.2013.51._1403-1_

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DOI： 10.1299/jsmecs.2013.51._1404-1_

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The purpose of this study is to develop a safe and efficient incineration method to treat a large amount of woody debris in the sea caused by the Great East Japan Earthquake Much of the debris remains untouched even two years after the earthquake We apply the two-stage combustion technique, which we developed for woody biomass, to the method Experiments are conducted using a small combustor and woody chips saturated with artificial sea water to simulate the incineration of the woody debris Effects of chloride on the combustion as well as combustion controllability are investigated for three different moisture contents

DOI： 10.1299/jsmepes.2013.18.53

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For the development of new combustion apparatus, a two-stage woody biomass combustion technique (pyrolytic combustion and surface combustion process) is proposed and discussed in this paper.

DOI： 10.20550/jiebiomassronbun.7.0_26

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Language：Japanese   Publisher：The Japan Society of Mechanical Engineers  

DOI： 10.1299/jsmecs.2012.50.140301

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DOI： 10.1299/jsmecs.2012.50.140501

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The development of a high-performance woody biomass combustion device becomes to be important, from the standpoint of the effective use of woody biomass. Woody biomass combustion is more complex and more difficult to control than gas or liquid fuel combustion due to its high combustibility and low thermal conductivity. For this reason, we propose a new combustion technique where the combustion process is divided into two stages: pyrolytic and surface combustion process. In this study, the mechanism and characteristics of the two-stage combustion are investigated.

DOI： 10.1299/jsmepes.2012.17.149

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In order to establish a model of the turbulent burning velocity of multi-component fuel mixtures, the turbulent burning velocity S_T of hydrogen added hydrocarbon-air mixtures with a wide range of equivalence ratio and hydrogen additional rate was examined, where methane and propane are adopted as hydrocarbon. S_T normalized by the laminar burning velocity S_<L0> at the same turbulent intensity u' normalized by S_<L0> was found to tend to increase with adding hydrogen to methane-air mixtures, however S_T for richer propane mixtures deceases with adding hydrogen. The increase of S_T/S_<L0> with hydrogen additions for lean methane mixtures was larger than that for rich mixtures. Additionally, a model of turbulent burning velocity proposed for single-component fuel mixtures in our previous study may be applied to two-component fuel-air mixtures by considering the estimated mean local burning velocities.

DOI： 10.1299/jsmepes.2012.17.277

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For the development of new combustion apparatus, a two-stage woody biomass combustion technique (pyrolytic combustion and surface combustion process) is proposed and discussed in this paper.

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DOI： 10.1299/jsmecs.2011.49.403

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DOI： 10.1299/jsmecs.2011.49.439

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In order to clarify and establish a model of the turbulent burning velocity of multi-component fuel mixtures, the turbulent burning velocity of hydrogen added methane-air mixtures with a wide range of equivalence ratio and hydrogen additional rate was examined. The turbulent burning velocity S_T at the same u'/S_<L0> was found to tend to increase with adding hydrogen to methane-air mixtures. The increase of S_T with hydrogen additions in lean mixtures was larger than that in rich mixtures. Additionally, a model of turbulent burning velocity proposed for single-component fuel mixtures may be applied to two-component fuel-air mixtures by considering the estimated mean local burning velocity.

DOI： 10.1299/jsmeted.2011.111

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Language：Japanese   Publisher：The Heat Transfer Society of Japan  

本研究は、層流燃焼速度を揃えた水素－酸素－希釈ガス混合気を用いて、定容燃焼器内に火炎半径５mm以下の微小球状伝ぱ層流火炎を作成し基礎燃焼特性を検討する。ここでは、希釈ガスに一般的な窒素に加え、アルゴンおよび二酸化炭素を対象とする。各混合気が有する最小点火エネルギー近傍で形成された微小球状伝ぱ層流火炎をシュリーレン法により観測する。火炎半径および伸長が、火炎面の平均燃焼速度に与える影響を定量的に明らかにする。

DOI： 10.11368/nhts.2011.0.190.0

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DOI： 10.1299/jsmecs.2011.49.399

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DOI： 10.1299/jsmecs.2011.49.401

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DOI： 10.1299/jsmecs.2010.48.327

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This study is performed to investigate experimentally the deflagration flame of dilution gas added to hydrogen-air mixtures propagating in a narrow space simulated channel with special attention to flame front configurations and speeds, because the deflagration to detonation transitions is caused mostly by enhancement of the flame front propagation. Mixtures having nearly the same laminar burning velocity S_<L0> diluted with Ar, CO_2 or He as well as N_2 are prepared, in order to examine effect of dilution gas types on inhibition of the flame propagation speed. The flame shape and propagation speeds are obtained by using sequential schlieren photograph images recorded. The results show that He deteriorates the flame acceleration with traveling a distance.

DOI： 10.1299/jsmeted.2010.99

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This study is performed to examine experimental the burning velocity characteristics of hydrocarbon-premixed micro-scale spherical laminar flames with the flame radius r_f<approximately 5 mm, and also macro-scale laminar flames with r_f>7 mm for comparison, where methane or propane is used as hydrocarbon. The mixtures have nearly the same laminar burning velocity and different equivalence ratio φ(φ=0.8〜1.0 for methane mixtures, φ=0.8〜1.2 for propane mixtures). The radius, stretch and the burning. velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. The results show that the burning velocities of micro-scale flames have tendency to increase with increasing r_f or decreasing the Karlovitz number and approach that of macro-scale flames. However, dependence on φ shows to be the difference between methane and propane mixtures.

DOI： 10.1299/jsmepes.2010.15.203

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DOI： 10.1299/jsmecs.2010.48.491

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DOI： 10.1299/jsmecs.2009.47.273

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This study is performed to examine experimental the burning velocity characteristics of the methane-premixed micro-scale spherical laminar flames with the flame radius r_f < approximately 5mm, and also macro-scale laminar flames with r_f > 5mm for comparison. The mixtures have nearly the same laminar burning velocity and different equivalence ratio φ(0.8〜1.0). The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. The results show that the burning velocity of methane-premixed micro-scale flames has tendency to increase with increasing r_f and approach that of macro-scale flames.

DOI： 10.1299/jsmeted.2009.3

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The influence of the addition of hydrogen to propane mixtures on its local burning velocity is investigated directly. Hydrogen added propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen and equivalence ratios are prepared. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F is quantitatively obtained as the key parameters of the turbulent combustion. The obtained S_F is also discussed by the concept of Markstein number.

DOI： 10.1299/jsmeted.2007.343

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DOI： 10.1299/jsmekyushu.2006.59.159

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The present study is performed to examine experimentally the burning velocity characteristics of lean hydrogen-premixed micro-scale spherical laminar flames in the range of flame radius γ_f approximately from 1 to 5mm, and also macro-scale laminar flames with γ_f>7mm for comparison. The mixtures have nearly the same laminar burning velocity and different equivalence ratio φ(0.3〜1.2). The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images. The results show that the burning velocities of micro-scale flames with φ=0.3, 0.5 and 1.2 have a tendency to decrease with increasing γ_f and approach that of macro-scale flames, but such a trend can not be seen for φ=0.7 and 0.9 micro-scale flames.

DOI： 10.1299/jsmeted.2006.307

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This study is attempted to establish a prediction model of turbulent burning velocity for hydrogen mixtures as a reference of the mean local burning velocity S_L estimated by taking account of the preferential diffusion effect, instead of the laminar burning velocity S_<L0>. The S_L is estimated for the specific mixtures having the same S_<L0> by adding nitrogen to hydrogen-air mixtures, where S_<L0> as well as the equivalence ratio are varied extensively, in order to confirm the effect of u'/S_<L0> on S_L. It is found that accuracy of the proposed simple mode can be improved by using S_L with respect to u'/S_<L0>.

DOI： 10.1299/jsmemecjo.2006.3.0_359

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The influence of the addition of hydrogen to propane mixtures on its local burning velocity is investigated directly. Hydrogen added lean and rich propane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen are prepared. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement. The local flame displacement velocity S_F is quantitatively obtained as the key parameters of the turbulent combustion. The obtained S_F is also discussed by the concept of Markstein number.

DOI： 10.1299/jsmemecjo.2006.3.0_357

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Language：Japanese   Publisher：日本流体力学会  

This study carries out to investigate directly the local flame propagation properties of hydrogen, methane and propane premixed turbulent flames in the weak turbulence region. A laser tomography technique is used to obtain the temporal local flame configuration and movement in a constant-volume vessel, and quantitative analyses are performed. The local flame front curvature and the local flame displacement velocity S_F are quantitatively obtained as the key parameters of the turbulent combustion. The values of S_F are found to be distributed over a wide range and to be dependent on the local curvature of the turbulent flame. In addition, the value of S_F for the methane and hydrogen mixtures have a tendency to become larger as decreasing its equivalence ratio, whereas those for the propane mixture become smaller. We discuss also the influence of preferential diffusion and Markstein number on the local flame displacement velocity.

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DOI： 10.1299/jsmekyushu.2006.59.161

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This study is made to attempt to establish a prediction model of turbulent burning velocity for hydrogen mixtures based on the mean local burning velocity estimated by taking the preferential diffusion into consideration S_L, instead of the laminar burning velocity S_<LO>. The S_L is estimated for the specific mixtures having the same S_<LO> by adding nitrogen to hydrogen-air mixtures, where S_<LO> as well as the equivalence ratio are varied extensively, in order to confirm the effect of u'/S_<LO>. It is found that accuracy of the proposed simple mode can be improved by using S_L with respect to u'/S_<LO>.

DOI： 10.1299/jsmeted.2005.61

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DOI： 10.1299/jsmekyushu.2005.58.147

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DOI： 10.1299/jsmekyushu.2005.58.145

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DOI： 10.1299/jsmekyushu.2004.57.191

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The influence of the addition of hydrogen to methane mixtures on its local burning velocity is investigated directly. Hydrogen added lean and rich methane mixtures having nearly the same laminar burning velocity with different rates of addition of hydrogen are prepared. A two-dimensional sequential laser tomography technique is used to obtain the temporal statistical relationship between the flame shape and the flame displacement The local flame displacement velocity Sp_F is quantitatively obtained as the key parameters of the turbulent combustioa The obtained S_F is also discussed by the concept of Markstein number.

DOI： 10.1299/jsmeted.2004.305

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Language：Japanese   Publisher：一般社団法人 日本機械学会  

DOI： 10.1299/jsmemag.107.1029_614_2

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DOI： 10.1299/jsmekyushu.2003.56.1

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DOI： 10.1299/jsmekyushu.2003.56.321

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Turbulent burning velocity characteristics of hydrogen mixtures with having the same laminar burning velocity are investigated experimentally in the present study, where the laminar burning velocity S_<L0> and the equivalence ratio Φ are varied extensively. The measured turbulent burning velocity at the same turbulence intensity shows to increase as Φ decreases, regardless of S_<L0>. That, however, becomes to depend on the characteristics chemical time when Φ is as low as around 1.0. This phenomenon is discussed by the estimated mean local burning velocity taking account of the preferential diffusion effect and the obtained turbulent flame images.

DOI： 10.1299/jsmeted.2003.559

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DOI： 10.1299/jsmekyushu.2003.56.323

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The present study is to clarify the relationship between the turbulent burning velocity and the turbulent flame configuration of hydrogen/oxygen/dilution gas mixtures, where the dilution gas is changed to N_2,Ar, CO_2,He keeping the laminar burning velocity nearly the same value. A laser tomography technique is used to obtain the flame shape. In the weak turbulence, the surface area of turbulent flame is found to be dependent slightly on the kind of dilution gas. The local burning velocity characteristics are discussed based on the local flame front configuration obtained by the flame tomograms.

DOI： 10.1299/jsmeptec.2002.0_145

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DOI： 10.1299/jsmekyushu.2002.55.193

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In our previous works, it was elucidated that the preferential diffusion effect played an important role in the turbulent burning velocity characteristics of hydrogen mixtures because of its high molecular diffusivity. In this study, the turbulent burning velocity and the effect of the preferential diffusion on turbulent burning velocity of lean hydrogen mixtures are investigated in more detail, by changing the laminar burning velocity 15 to 35cm/s and the equivalence ratioФ 0.9 to 0.3. The turbulent burning velocity at the same turbulence intensity shows to increase as Ф decreases up to about 0.5. That, however, does not show such increase when Ф is under about 0.5,regardless of the laminar burning velocity. From the estimate of mean local burning velocity taking the preferential diffusion effect into consideration, it is found that the mean local burning velocity tends to decrease as Ф becomes under about 0.5.

DOI： 10.1299/jsmekansai.2002.77._5-11_

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In this study, an attempt is made to examine the effect of the kind of fuel on the propagation characteristics of turbulent flame in a weak turbulence region. In order to measure directly the local buming velocity, the sequential flame tomograms of hydrogen, methane and propane mixtures are obtained by a laser tomography technique. As a result, the measured local buming velocities of turbulent flame are found to be not a constant value equal to the laminar burning velocity, but to be distributed over wide range. This distribution for hydrogen mixture is wider than that for hydrocarbon mixtures. In addition, the mean value of local buming velocity for the lean hydrogen and the lean methane mixture have a tendency to become larger than its original laminar burning velocity, whereas that for the lean propane mixture becomes smaller.

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DOI： 10.1299/jsmekyushu.2001.54.183

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DOI： 10.1299/jsmekyushu.2000.53.41

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