著者

Nagura Yuto Kasahara Jiro Sugiyama Yuta Matsuo Akiko

出版者

Elsevier Inc.

雑誌

Proceedings of the Combustion Institute (ISSN:15407489)

巻号頁・発行日

vol.34, no.2, pp.1949-1956, 2013

被引用文献数

26

---

The geometry and characteristic length of diffraction and re-initiation during a two-dimensional detonation propagation were revealed by visualization. C2H4 + 3O2 (unstable), 2C2H2 + 5O2 + 7Ar (stable) and 2C2H2 + 5O2 + 21Ar (stable) were used as the test mixtures. Experiments were performed over the deviation angle range from 30° to 150° and the initial pressure range from 15.8 to 102.3 kPa. By self-emitting photography, we confirmed that the geometry and the characteristic length of diffraction are not different among test gases, with the exception of the fan-like structure of re-initiation that occurred regardless of whether the mixture was unstable or stable. We conducted a compensative experiment by changing the deviation angle and initial pressure, and summarized the detonation diffraction by shadowgraph. At deviation angles larger than 60°, we measured the distances from the vertex of the channel corner to the point where the transverse detonation wave reflected on the under wall (= wall reflection distance) and confirmed that wall reflection distances are approximately in the range of 10–15 times the cell width, whether the mixture is unstable or stable.

著者

Yamashita Hiroki Kasahara Jiro Sugiyama Yuta Matsuo Akiko

出版者

Elsevier Inc.

雑誌

Combustion and flame (ISSN:00102180)

巻号頁・発行日

vol.159, no.9, pp.2954-2966, 2012-09

被引用文献数

47 1

---

This study was a numerical and experimental investigation of low-temperature auto-ignitions behindreflected shock waves in which a shock tube was employed as the experimental system. We used ahigh-speed video camera and the Schlieren method to visualize the ignition phenomena. Experimentswere performed over a temperature range from 549 ± 10 to 1349 ± 11 K and a pressure range from56 ± 2 to 203 ± 13 kPa, and a non-diluted stoichiometric acetylene–oxygen mixture was chosen as thecombustible gas. We introduced a numerical simulation to help us understand the disturbed temperaturedistribution behind bifurcated shock waves due to interference between reflected shock waves and theboundary layer developed behind incident shock waves. Additionally, we experimentally observed andevaluated quantitatively a tendency for ignition positions to be located farther from the reflecting wallas the temperature decreased behind reflected shock waves. To focus our attention on the ignition positions,we classified the ignition types behind reflected shock waves as near-wall ignition and far-wallignition by 4.7 mm distance from reflecting wall. The criterion for these ignition types was estimatedto be -1.0≦(∂ti/∂T5t)p5t≦-0.5. As a main object in this manuscript, we proposed an ignition modelin which local ignition is induced at some distance from reflecting wall based on the numerical simulationand results; the local ignitions at a point distant from the reflecting wall are induced by the temperaturerise, with the distance from the reflecting wall, immediately behind concave reflected shock wavesdue to developing of bifurcated shock waves. We confirmed that there is no discrepancy between the proposedmodel and experimental results.