Numerical studies on weak and strong ignition induced by reflected shock and boundary layer interaction  

反射激波与边界层相互作用引起弱点火和强点火的数值研究

作　　者：Chengyang Huang Yuan Wang Ralf Deiterding Dehai Yu Zheng Chen 黄成扬;王元;Deiterding Ralf;于德海;陈正(SKLTCS,CAPT,College of Engineering,Peking University,Beijing 100871,China;Institute of Applied Physics ami Computational Mathematics,Beijing 100094,China;Aerochnamics and Flight Mechanics Research Group,University of Southampton,Highfield Campus,Southampton SO171BJ,UK)

机构地区：[1]SKLTCS,CAPT,College of Engineering,Peking University,Beijing 100871,China [2]Institute of Applied Physics ami Computational Mathematics,Beijing 100094,China [3]Aerochnamics and Flight Mechanics Research Group,University of Southampton,Highfield Campus,Southampton SO171BJ,UK

出　　处：《Acta Mechanica Sinica》2022年第2期24-34,I0001,共12页力学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.52006001,and 52176096).

摘　　要：In shock tube experiments,the interaction between the reflected shock and boundary layer can induce shock bifurcation and weak ignition.The weak ignition can greatly affect the ignition delay time measurement in a shock tube experiment.In this work,two-dimensional simulations considering detailed chemistry and transport are conducted to investigate the shock bifurcation and non-uniform ignition behind a retlected shock.The objectives are to interpret the formation of shock bifurcation induced by the reflected shock and boundary layer interaction and to investigate the weak ignition and its transition to strong ignition for both hydrogen and dimethyl ether.It is found that the non-uniform reflection of the incident shock at the end wall produces a wedge-shaped oblique shock foot at the wall.The wedge-shaped structure results in strong interactions between reflected shock and boundary layer,which induces the shock bifurcation.It is demonstrated that the local high-temperature spots at the foot of the bifurcated shock is caused by viscous dissipation and pressure work.As the post-reflected shock temperature increases,the transition from weak ignition to strong ignition in a stoichiometric hydrogen/oxygen mixture is observed.The relative sensitivity of ignition delay time to the post-rellected shock temperature is introduced to characterize the appearance of weak ignition behind the reflected shock.Unlike in the hydrogen/oxygen mixture,weak ignition is not observed in the stoichiometric dimethyl-ether/oxygen mixture since it has a relatively longer ignition delay time and smaller relative sensitivity.在激波管实验中,反射激波与边界层的相互作用会导致激波分义和弱点火.在激波管实验中,弱点火会严重影响点火延迟时间的测量.在考虑详细的化学和输运效应下,本文通过二维数值模拟研究反射激波后的激波分岔和非均匀点火,以解释反射激波和边界层相互作用引发激波分岔的形成机理,并研究氢和二甲醚的弱点火及其向强点火的转变.研究发现入射激波在端壁的非均匀反射会在壁面产生一个楔形斜激波脚.楔形结构导致反射激波和边界层之间的强烈相互作用,从而导致激波分岔.结果表明分叉激波底部的局部高温点产生于黏性耗散和压力功.随着反射后激波温度的升高,在化学计量氢/氧混合物中观察到从弱点火到强点火的转变.通过引入点火延迟时间对反射后激波温度的相对灵敏度,可以表征反射激波后弱点火出现.与氢/氧混合物不同,在二甲醚/氧混合物中未观察到弱点火现象,因为其具有相对较长的点火延迟时间和较小的相对灵敏度.

关 键 词：Shock tube Weak ignition Shock-houndary layer interaction 

分 类 号：O302[理学—力学]