两点射流间隔时间对爆震波起爆特性影响的数值研究

Numerical Study of Effects of Double-Jet Interval Time on Detonation Initiation Characteristics

关键词:  爆震发动机  射流起爆  多点射流点火  射流间隔时间  起爆特性

Key words:  Detonation engine  Jet initiation  Multiple jets initiation  Jet interval time  Initiation characteristics

摘要:

为快速、短距起爆爆震波，基于H₂/Air 8组分19步反应简化机理，采用两点射流点火的方法数值研究了不同射流管高度差引起的射流间隔时间对H₂/Air混合物起爆特性的影响规律。采用与CEA计算结果及实验结果对比的方法验证了数值模拟的可靠性。结果表明，射流间隔时间对两点射流起爆有明显影响。一定射流间隔时间内可以成功起爆，但第一射流的衰减过程随射流间隔时间的延长而变长，不利于起爆。射流管的高度差使得射流管出口形成射流强度梯度，对射流强度的影响较小。射流管高度差ΔH的增加会加大两个射流之间的强度差，从而削弱射流相互作用。射流之间的相互作用受火焰面和压力面的共同影响，热点的形成更依赖于射流压力的相互作用。

Abstract:

In order to initiate the detonation waves efficiently， the ignition method of two jets was proposed and utilized to initiate the mixture of H₂/Air in a detonation chamber. The numerical simulation based on H₂/Air 8 species and 19 steps chemical reaction kinetics mechanism was carried out to study the effects of the double-jet interval time caused by jet tubes height difference on detonation initiation. The reliability of the numerical simulation was verified by the experimental results and the calculation results of CEA. The results indicated that the two hot jets detonated the mixed gas in the detonation chamber successfully within a certain range of jet interval time. However the decrease of jet interaction caused by the increase of jet interval time was not beneficial to the initiation of detonation wave. The height of jet tube affected the jet intensity， and the jet intensity gradient was formed near the outlet of the jet tubes during the detonation initiation. The increase of jet tubes height difference ΔH enlarged the intensity difference between two jets， which weakened the jet interaction. The interaction between two jets was caused by the pressure front interaction and the temperature front interaction， and the pressure interaction had a greater influence on the formation of hot spots.