Combustion wave propagation and detonation initiation in the vicinity of closed-tube end walls |
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Authors: | Jun Yageta Satoshi Shimada Ken Matsuoka Jiro Kasahara Akiko Matsuo |
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Institution: | aDepartment of Engineering Mechanics and Energy, University of Tsukuba, Tennodai 1-1-1, Tsukuba 305-8573, Japan;bDepartment of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522, Japan |
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Abstract: | There are not many studies on DDT with no obstacles and the initiation of DDT near the end of a closed tube. Therefore in the present study we experimentally investigate the mechanism of the combustion wave transition to a detonation wave when there are no obstacles. In particular, we show that a local explosion near the tube wall is necessary for the initiation of a detonation. Parameters that we varied are the wall configuration, distance between the ignition point and the wall, and initial filling pressure. The combustion waves and the compression waves are visualized using the Schlieren optical system. From the results, we found it is necessary for the combustion wave to reach four walls so that the detonation could be initiated by the local explosion. In the conditions of the present experiment, we exhibited that the local explosion did not occur in the vicinity of a single wall and four orthogonal walls; instead, the local explosion occurred in a situation with five orthogonal walls. The time of the local explosion and the detonation initiation is 2.6 ± 1.1 and 2.0 ± 0.1 times the characteristic time for the combustion wave to propagate hemispherically from an ignitor and reach the four walls. |
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Keywords: | Detonation wave Detonation initiation Deflagration-to-detonation transition Pulse detonation engine |
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