The Experts below are selected from a list of 18141 Experts worldwide ranked by ideXlab platform
Ikkoh Funaki - One of the best experts on this subject based on the ideXlab platform.
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front shock behavior of stable curved detonation waves in Rectangular Cross Section curved channels
Proceedings of the Combustion Institute, 2013Co-Authors: Hisahiro Nakayama, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The propagation of curved detonation waves of gaseous explosives stabilized in Rectangular-Cross-Section curved channels is investigated. Three types of stoichiometric test gases, C 2 H 4 + 3O 2 , 2H 2 + O 2 , and 2C 2 H 2 + 5O 2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel ( r i ) to the normal detonation cell width ( λ ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around r i / λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity ( D n )−curvature ( κ ) relations are evaluated. The D n nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity ( D CJ ) is a function of the κ nondimensionalized by λ . The D n / D CJ − λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the D n / D CJ − λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same r i / λ , regardless of the curved channel and test gas.
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stable detonation wave propagation in Rectangular Cross Section curved channels
Combustion and Flame, 2012Co-Authors: Hisahiro Nakayama, Takahiro Moriya, Yuya Sasamoto, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of Rectangular-Cross-Section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel ( r i ) equivalent to 21–32 times the normal detonation cell width ( λ ). In the stable propagation mode, the normal detonation velocity ( D n ) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight Section of the curved channel ( D str ). The smallest D n was observed on the inner wall and decreased with decreasing r i / λ . The distribution of D n on the detonation wave in the stable mode was approximately formulated. The approximated D n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave ( κ ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r i / λ . D n / D str decreased with increasing λκ . This nondimensionalized D n – κ relation was nearly independent of r i / λ .
Akiko Matsuo - One of the best experts on this subject based on the ideXlab platform.
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front shock behavior of stable curved detonation waves in Rectangular Cross Section curved channels
Proceedings of the Combustion Institute, 2013Co-Authors: Hisahiro Nakayama, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The propagation of curved detonation waves of gaseous explosives stabilized in Rectangular-Cross-Section curved channels is investigated. Three types of stoichiometric test gases, C 2 H 4 + 3O 2 , 2H 2 + O 2 , and 2C 2 H 2 + 5O 2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel ( r i ) to the normal detonation cell width ( λ ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around r i / λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity ( D n )−curvature ( κ ) relations are evaluated. The D n nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity ( D CJ ) is a function of the κ nondimensionalized by λ . The D n / D CJ − λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the D n / D CJ − λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same r i / λ , regardless of the curved channel and test gas.
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stable detonation wave propagation in Rectangular Cross Section curved channels
Combustion and Flame, 2012Co-Authors: Hisahiro Nakayama, Takahiro Moriya, Yuya Sasamoto, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of Rectangular-Cross-Section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel ( r i ) equivalent to 21–32 times the normal detonation cell width ( λ ). In the stable propagation mode, the normal detonation velocity ( D n ) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight Section of the curved channel ( D str ). The smallest D n was observed on the inner wall and decreased with decreasing r i / λ . The distribution of D n on the detonation wave in the stable mode was approximately formulated. The approximated D n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave ( κ ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r i / λ . D n / D str decreased with increasing λκ . This nondimensionalized D n – κ relation was nearly independent of r i / λ .
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oblique detonation waves stabilized in Rectangular Cross Section bent tubes
Proceedings of the Combustion Institute, 2011Co-Authors: Yusuke Kudo, Yuya Sasamoto, Jiro Kasahara, Yuuto Nagura, Akiko MatsuoAbstract:Abstract Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through Rectangular-Cross-Section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the Rectangular-Cross-Section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the Rectangular-Cross-Section bent tubes was the curvature radius of the inside wall of the Rectangular-Cross-Section bent tube equivalent to 14–40 times the cell width.
Hisahiro Nakayama - One of the best experts on this subject based on the ideXlab platform.
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front shock behavior of stable curved detonation waves in Rectangular Cross Section curved channels
Proceedings of the Combustion Institute, 2013Co-Authors: Hisahiro Nakayama, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The propagation of curved detonation waves of gaseous explosives stabilized in Rectangular-Cross-Section curved channels is investigated. Three types of stoichiometric test gases, C 2 H 4 + 3O 2 , 2H 2 + O 2 , and 2C 2 H 2 + 5O 2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel ( r i ) to the normal detonation cell width ( λ ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around r i / λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity ( D n )−curvature ( κ ) relations are evaluated. The D n nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity ( D CJ ) is a function of the κ nondimensionalized by λ . The D n / D CJ − λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the D n / D CJ − λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same r i / λ , regardless of the curved channel and test gas.
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stable detonation wave propagation in Rectangular Cross Section curved channels
Combustion and Flame, 2012Co-Authors: Hisahiro Nakayama, Takahiro Moriya, Yuya Sasamoto, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of Rectangular-Cross-Section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel ( r i ) equivalent to 21–32 times the normal detonation cell width ( λ ). In the stable propagation mode, the normal detonation velocity ( D n ) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight Section of the curved channel ( D str ). The smallest D n was observed on the inner wall and decreased with decreasing r i / λ . The distribution of D n on the detonation wave in the stable mode was approximately formulated. The approximated D n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave ( κ ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r i / λ . D n / D str decreased with increasing λκ . This nondimensionalized D n – κ relation was nearly independent of r i / λ .
Jiro Kasahara - One of the best experts on this subject based on the ideXlab platform.
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front shock behavior of stable curved detonation waves in Rectangular Cross Section curved channels
Proceedings of the Combustion Institute, 2013Co-Authors: Hisahiro Nakayama, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The propagation of curved detonation waves of gaseous explosives stabilized in Rectangular-Cross-Section curved channels is investigated. Three types of stoichiometric test gases, C 2 H 4 + 3O 2 , 2H 2 + O 2 , and 2C 2 H 2 + 5O 2 + 7Ar, are evaluated. The ratio of the inner radius of the curved channel ( r i ) to the normal detonation cell width ( λ ) is an important factor in stabilizing curved detonation waves. The lower boundary of stabilization is around r i / λ = 23, regardless of the test gas. The stabilized curved detonation waves eventually attain a specific curved shape as they propagate through the curved channels. The specific curved shapes of stabilized curved detonation waves are approximately formulated, and the normal detonation velocity ( D n )−curvature ( κ ) relations are evaluated. The D n nondimensionalized by the Chapman–Jouguet (CJ) detonation velocity ( D CJ ) is a function of the κ nondimensionalized by λ . The D n / D CJ − λκ relation does not depend on the type of test gas. The propagation behavior of the stabilized curved detonation waves is controlled by the D n / D CJ − λκ relation. Due to this propagation characteristic, the fully-developed, stabilized curved detonation waves propagate through the curved channels while maintaining a specific curved shape with a constant angular velocity. Self-similarity is seen in the front shock shapes of the stabilized curved detonation waves with the same r i / λ , regardless of the curved channel and test gas.
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stable detonation wave propagation in Rectangular Cross Section curved channels
Combustion and Flame, 2012Co-Authors: Hisahiro Nakayama, Takahiro Moriya, Yuya Sasamoto, Akiko Matsuo, Jiro Kasahara, Ikkoh FunakiAbstract:Abstract The detonation propagation phenomena in curved channels were experimentally studied in order to determine the stable propagation condition. A stoichiometric ethylene–oxygen mixture gas and five types of Rectangular-Cross-Section curved channels with different inner radii of curvature were employed. The detonation waves propagating through the curved channels were visualized using a high-speed video camera. Multi-frame short-time open-shutter photography (MSOP) was developed in the present study to simultaneously observe the front shock shape of the detonation wave and the trajectories of triple points on the detonation wave. The detonation wave became more stable under the conditions of a higher filling pressure of the mixture gas and/or a larger inner radius of curvature of the curved channel. The critical condition under which the propagation mode of the detonation wave transitioned from unstable to stable was having an inner radius of curvature of the curved channel ( r i ) equivalent to 21–32 times the normal detonation cell width ( λ ). In the stable propagation mode, the normal detonation velocity ( D n ) increased with the distance from the inner wall of the curved channel and approached the velocity of the planar detonation propagating through the straight Section of the curved channel ( D str ). The smallest D n was observed on the inner wall and decreased with decreasing r i / λ . The distribution of D n on the detonation wave in the stable mode was approximately formulated. The approximated D n given by the formula agreed well with the experimental results. The front shock shape of the detonation wave could be reconstructed accurately using the formula. The local curvature of the detonation wave ( κ ) nondimensionalized by λ decreased with increasing distance from the inner wall. The largest λκ was observed on the inner wall and increased with increasing r i / λ . D n / D str decreased with increasing λκ . This nondimensionalized D n – κ relation was nearly independent of r i / λ .
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oblique detonation waves stabilized in Rectangular Cross Section bent tubes
Proceedings of the Combustion Institute, 2011Co-Authors: Yusuke Kudo, Yuya Sasamoto, Jiro Kasahara, Yuuto Nagura, Akiko MatsuoAbstract:Abstract Oblique detonation waves, which are generated by a fundamental detonation phenomenon occurring in bent tubes, may be applied to fuel combustion in high-efficiency engines such as a pulse detonation engine (PDE) and a rotating detonation engine (RDE). The present study has experimentally demonstrated that steady-state oblique detonation waves propagated stably through Rectangular-Cross-Section bent tubes by visualizing these waves using a high-speed camera and the shadowgraph method. The oblique detonation waves were stabilized under the conditions of high initial pressure and a large curvature radius of the inside wall of the Rectangular-Cross-Section bent tube. The geometrical shapes of the stabilized oblique detonation waves were calculated, and the results of the calculation were in good agreement with those of our experiment. Moreover, it was experimentally shown that the critical condition under which steady-state oblique detonation waves can stably propagate through the Rectangular-Cross-Section bent tubes was the curvature radius of the inside wall of the Rectangular-Cross-Section bent tube equivalent to 14–40 times the cell width.
Yuying Yan - One of the best experts on this subject based on the ideXlab platform.
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confined bubble growth during flow boiling in a mini micro channel of Rectangular Cross Section part i experiments and 1 d modelling
International Journal of Thermal Sciences, 2011Co-Authors: Sateesh Gedupudi, T G Karayiannis, D B R Kenning, Yuying YanAbstract:Abstract Heat sinks using evaporation in arrays of parallel microchannels have potential for the removal of high heat fluxes from small areas. They suffer from flow instabilities and uneven distribution between channels that may cause local dryout and overheating. The current state of the art is reviewed critically. A simple 1-D model for bubble growth in a single channel with a compressible volume in its upstream plenum is developed as a tool for the rational design of measures known to reduce flow instabilities, namely inlet resistance and enhanced nucleation in every channel. The model considers two stages of partially and fully confined bubble growth in a single channel of Rectangular Cross-Section, suggested by experimental observations, followed by venting of vapour to the downstream plenum. The experiments also show the influence of apparently minor changes in rig design and operation on upstream compressibility and flow reversal. The model considers upstream compressibility due to subcooled boiling in a preheater or trapped non-condensable gas and the reduction of flow reversal by inlet resistance. The feasibility of measuring transient axial variations in pressure within small channels using inexpensive transducers is demonstrated.
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confined bubble growth during flow boiling in a mini micro channel of Rectangular Cross Section part ii approximate 3 d numerical simulation
International Journal of Thermal Sciences, 2011Co-Authors: Yuying Yan, Sateesh Gedupudi, T G Karayiannis, D B R KenningAbstract:Abstract This Part II of the paper reports the three-dimensional (3-D) numerical modelling on bubbly flow in confined mini-/micro-channels using the volume of fluid (VOF) method in commercial CFD code FLUENT. The numerical simulation aims to provide detailed information of the fields of velocity, temperature and pressure so as to further understand the effect of bubble growth on the flow field and heat transfer from the channel wall. In Part I, the experiment of flow boiling in a mini-/micro-channel of Rectangular Cross-Section was carried out and a simple one-dimensional (1-D) model for the interaction of the pressure fluctuations during the growth of a confined bubble with various kinds of upstream compressibility was developed as an aid to the rational specification of inlet resistance. In Part II, the experimental observers and the theoretical model developed in Part I are tested by performing the 3-D numerical simulation of bubble growth from nucleation to full confinement. The simulation involves some approximations based on a concept of pseudo-boiling to avoid the well-known difficulties of modelling bubble generation and growth. During the simulation, the volumetric growth rate of the bubble is defined to match the experimental observations. At small times prior to bubble detachment, a vapour flow was injected through a small hole in the wall to simulate nucleation. Following partial confinement, vapour injection was stopped and growth was driven by the generation of vapour at a defined rate at the contact area between the bubble and the superheated wall. The 3-D simulation reproduces the experimental observations of the distorted profile of the bubble and its trajectory during partially confined growth and provides information about flow and heat transfer in the bulk liquid outside the thin film region. The 3-D and 1-D predictions of the development of axial pressure distributions during partially and fully confined growth are in satisfactory agreement.
