Ignition of methane/air mixture by the passage of a shock wave is an important issue for understanding more details ofits gaseous detonation.The experiments of shock-induced ignition of stoichiometric methane/air mixt...Ignition of methane/air mixture by the passage of a shock wave is an important issue for understanding more details ofits gaseous detonation.The experiments of shock-induced ignition of stoichiometric methane/air mixture were conducted on a shock tube platform.The reaction zone structure in weak and strong ignition cases were investigated by digital chemiluminescence imaging and planar laser induced fluorescence(PLIF) techniques.Due to smaller gradients in induced time in weak ignition,which provided more time to nonlinear chemical reaction process,the results show that the reaction structures are highly nonuniform in those weak ignition cases,which become more regular while induced shock waves become stronger.In strong ignition case,it gives a typical detonation structure.The characteristics of reaction zone released by single-pulsed OH PLIF technique agreed well with other experimental measurements in this paper and were also in accord with the conclusions of previous researches.The successful implementation of the PLIF system has explored a new high temporally and spatially resolved method for the study ofinteraction between shock wave and gaseous matter in shock tube.展开更多
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 sho...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.展开更多
基金Supported by the National High Technology R&D Program of China(Grant No.2006AA05Z210)Graduated Student Research Foundation of Chinese Acdemy Science
文摘Ignition of methane/air mixture by the passage of a shock wave is an important issue for understanding more details ofits gaseous detonation.The experiments of shock-induced ignition of stoichiometric methane/air mixture were conducted on a shock tube platform.The reaction zone structure in weak and strong ignition cases were investigated by digital chemiluminescence imaging and planar laser induced fluorescence(PLIF) techniques.Due to smaller gradients in induced time in weak ignition,which provided more time to nonlinear chemical reaction process,the results show that the reaction structures are highly nonuniform in those weak ignition cases,which become more regular while induced shock waves become stronger.In strong ignition case,it gives a typical detonation structure.The characteristics of reaction zone released by single-pulsed OH PLIF technique agreed well with other experimental measurements in this paper and were also in accord with the conclusions of previous researches.The successful implementation of the PLIF system has explored a new high temporally and spatially resolved method for the study ofinteraction between shock wave and gaseous matter in shock tube.
基金supported by the National Natural Science Foundation of China(Grant Nos.52006001,and 52176096).
文摘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.
