An Investigation on Instability of Deflagration and Detonation Induced by Conical Shock Wave

Numerical simulation was carried out to investigate the structures and instabilities of deflagration and detonation waves induced by an incoming flow of stoichiometric H2/air premixed gas with Mach Number 6.5 over a cone with half cone angle 32°,based on the multi-component Euler equations with chemical reactions.The reliabilities of numerical model and computational grid were verified using the experimental results in Literature[7].The numerical results show that the combustion induced by conical shock wave includes both detonation and deflagration modes.Both the modes,which can alternately appear,show the regularly spatial instability and the temporally periodic oscillation instability.The regularly spatial unstable detonation is regarded as a coalescence of the basic triple wave structures,while the unstable deflagration shows a zigzag reaction front.In an oscillation combustion period,the evolution of detonation and deflagration modes is affected by triple wave structure,thermodynamics of unburned gas in the reaction induction region and disturbance of reflected waves from wall,and shows the distinct phenomena of which the chemical reaction induction length increases along the cone wall during the deflagration process and decreases during the detonation process.The results are significant for the combustion chamber design of scramjet or standing detonation engine.