Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen–oxygen mixture

详细信息    查看全文

• 作者：S. Maeda ; S. Minami ; D. Okamoto ; T. Obara
• 关键词：Detonation wave ; Deflagration wave ; Deflagration ; to ; detonation transition (DDT) ; Obstacle ; filled channel ; Schlieren visualization
• 刊名：Shock Waves
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：26
• 期：5
• 页码：573-586
• 全文大小：7,219 KB
• 刊物类别：Physics and Astronomy
• 刊物主题：Physics
  Mechanics, Fluids and Thermodynamics
  Fluids
  Thermodynamics
  Acoustics
  Condensed Matter
  Solid State Physics and Spectroscopy
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-2153
• 卷排序：26

文摘

The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.