著者

小原 哲郎 大八木 重治 高藤 亮一 蔡 品

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.67, no.659, pp.1680-1686, 2001-07-25 (Released:2008-03-28)

参考文献数

14

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Experiments are carried out to investigate behavior of shock wave diffraction from a safety-engineering point of view. Because, once the shock wave is released into an ambience, high pressure and negative pressure lasting for relatively long period have possibility to cause serious damages against human bodies as well as general buildings. Therefore, it should be one of the most significant subjects to attenuate the shock wave efficiently within a short distance from the source. In this report, a cavity is installed at an open end of a shock tube and flow-fields behind diffracted shock wave are visualized using schlieren photography. In addition, piezo-electric pressure transducer is flush mounted on the surface of reflector, which is installed at test section, and pressure histories are recorded with wide frequency response. Lastly, numerical simulation using the TVD finite difference scheme is performed to compare with the experimental results. As a result, (i) the pressure histories on the reflector coincides well between the numerical and experimental results, (ii) flow-fields behind the shock wave are clarified, (iii) maximum pressure behind reflected shock wave can be attenuated by installing several cavities inside the open end of the shock tube.

著者

高藤 亮一 山中 昭央 小原 哲郎 蔡 品 大八木 重治

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 B編 (ISSN:03875016)

巻号頁・発行日

vol.65, no.639, pp.3602-3607, 1999-11-25 (Released:2008-03-28)

参考文献数

12

被引用文献数

2 2

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As is well known when a shock wave is emitted from an open end of a tube, an expansion wave and a vortex ring are generated behind the shock wave. Furthermore, a contact surface, slip line and these wave interactions may cause considerably complicate flow-fields. In this study, shock waves of Mach number 1.3, 1.6 and 2.2 are produced utilizing diaphragm-less shock tube of 50 mm diameter and c. a. 10 m total length, and the flow-fields are visualized with an aid of schlieren optical techniques. A cylindrical reflector is installed at test section and stagnation pressure behind reflected shock wave is measured with wide frequency response. A numerical analysis is also carried out to investigate these flow-fields using Predictor-Corrector TVD finite difference scheme. As a result, (i) the contour of diffracted shock wave is well coincided between experimental and numerical results, (ii) pressure histories behind reflected shock wave are clarified, (iii) an empirical formula is obtained between Mach number, non-dimensional distance from the open end of the tube and non-dimensional pressure just behind reflected shock wave.

著者

大八木 重治

出版者

埼玉大学総合研究機構

雑誌

総合研究機構研究プロジェクト研究成果報告書

巻号頁・発行日

vol.16年度, 2005

著者

永井 厚司 岡部 俊彦 キム ギョンミン 吉橋 照夫 小原 哲郎 大八木 重治

出版者

一般社団法人 日本燃焼学会

雑誌

日本燃焼学会誌 = Journal of the Combustion Society of Japan (ISSN:13471864)

巻号頁・発行日

vol.52, no.159, pp.86-93, 2010-02-15

参考文献数

27

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<p>Pulse detonation engines (PDEs) are expected to be the next-generation engine systems, and are expected to have applications in various fields. One of the fundamental problems faced during the development of PDEs is the deflagration to detonation transition (DDT). In order to realize a PDE, it is essential to shorten a parameter of detonation transition called a detonation induction distance (DID). However, the mechanism underlying the DDT process and methods to shorten DID in narrow channels have not yet been understood. An experimental study on DDT process in a narrow rectangular channel with a height of 1-5 mm and a width of 8 mm was carried out by employing pressure transducers, ionization probes, and sooted plate technique in oxyhydrogen mixtures. The effects of the tube height and equivalence ratio on pressure detonation limits were discussed. Detonation velocity, DDT process, and DID were discussed on the basis of pressure history and soot track record. Overdriven detonation and attenuated detonation were observed in the narrow channel. The DID value measured on the basis of the soot track record in the present study was in the range of the empirical formula obtained by the other researchers.</p>

著者

大八木 重治 落合 辰夫 吉橋 照夫 針谷 安男

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. B編 (ISSN:03875016)

巻号頁・発行日

vol.54, no.508, pp.3559-3564, 1988-12-25

被引用文献数

7

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Detonation cell size has been measured in a mixture of hydrogen with oxygen over wide ranges of equivalence ratio and subatmosheric initial pressure. The experiments have been carried out in a cylindrical tube of diameter 30 mm and the cell size has been determined by using the sooted plate technique. The data of the cell size at subatomospheric pressures have indicated that it is proportional to p_0^<-1.2>, where p_0 is an initial pressure of the mixtures. Values at the atmospheric pressure have been obtained by extrapolating the obtained subatmosheric values of the cell size, and have been plotted against the equivalence ratio and compared with calculated induction zone length by Westbrook. The fact that the cell size is directly proportional to the induction zone length has been verified for the oxyhydrogen mixture over the range of the equivalence ratio tested. The proportionality factor for this mixture has been found to be 23.3, while that for hydrogen/air mixtures had been found by Knystautas et al. to be 52.2. The critical initiation energies etimated from the cell size data obtained here by utilizing the theoretical model proposed by Lee have been found to be in good agreement with measured critical initiation energies by the critical tube diameter method of Matsui and Lee.