报告内容摘要：

Spontaneous ignition of hydrogen jets was first investigated by Wolanski and Wojcicki in the seventies. In accident scenarios triggered by a sudden rupture of a high pressure hydrogen vessel, ignition is occasionally observed during the transient, early phase of the rupture. A number of potential mechanisms has been proposed.  While no consensus has been reached, the so-called diffusion ignition mechanism remains the most likely. In the shock structure due to the sudden release, shock heated air is initially separated from hydrogen cooled by expansion by a contact surface.  Heat and mass diffusion at that interface may result in fuel-air mixture at a temperature sufficient to result in a sustained ignition. however, the three-dimensional shock structure expands, resulting in a drop in pressure near the contact surface
We have developed and analysis of such a diffusion process with chemical reaction.  The analysis consider a time sufficiently short that only small, incipient chemistry takes place, which can thus be looked at as a perturbation added to a non-reactive solution to the diffusion process.
Initially, a single step kinetic model was considered, assuming high activation energy.  Results showed the depending upon the Lewis number, and if the expansion rate stays below a cutoff value, either ignition would take place in finite time, or no ignition would occur at all.
Next, the analysis was extended, accounting for complex schemes. The key assumption is that reaction rates can be divided into three categories: initiation, which is slow, most binary steps involving a radical released by initiation, which is faster, and termination which is even faster.  Then the short time assumption implies that the concentration of radicals released by initiation is small, and only some steps remain important.  The problem requires a numerical solution, which was developed using Hermite polynomials. Results confirm the importance of the Lewis number, not only of molecular hydrogen but also of the H radical.

报告人简介：

Luc Bauwens，卡尔加里大学机械工程学院教授, 1989年于美国加州大学伯克利分校机械工程专业博士毕业。主要研究领域为爆轰、爆炸安全。在“XVth International Stirling Engine Conference and Exhibition”、“France's national academy of sciences”、“International Symposium on Recent Advances in Combustion and Noise Control for Propulsion”、“39th Aerospace Sciences Meeting, AIAA”、“10th the International Seminar on Electroanalytical Chemistry”等国际会议上作邀请报告20余次。在《Proceedings of The Combustion Institute》、《J. Acoustical Society of America》、《Hydrogen Energy》、《Royal Society of London A》、《Shock Waves》、《Physics of Fluids》、《Journal of Fluid Mechanics》、《AIAA》等国际重要刊物发表论文50余篇。目前担任国际爆炸与反应系统动力学会主席(President of Institute of Dynamics of Explosions and Reactive System)、美国航空航天学会（AIAA）Associate Fellow、《Shock Waves》副主编等学术职务。
 
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