Stationary Conical Detonation Wave Structure And Stability Studies

The two-dimensional axisymmetric Euler equations were used to numerically study the phenomenon of detonation waves induced by an incoming flow composed of stoichiometric H₂/air premixed gas over a cone. The reliability of numerical model and grid resolution was verified by experimental results from literature. Based on the model, the structures and instabilities of deflagration and detonation waves induced by a cone were firstly investigated. The numerical results show that the combustion induced by conical shock wave includes both detonation and deflagration modes. Both modes show the regularly spatial instability and the temporally periodic oscillation instability of combustion in which two modes can alternately appear. Within an oscillation combustion period, the evolution of detonation and deflagration modes is affected by triple structure, thermodynamics of unburned gas within reaction induction region and disturbance of reflected waves from wall. Secondly, the effects of initial temperatures, initial pressure, incoming flow Mach number and incoming flow deflection angle on the detonation wave structure were investigated. The results show that the detonation wave front shows a smooth shape at the higher initial inflow temperature, while at the lower initial temperature, the triple structures appear at the front. The higher initial temperature is, the more number of the serried triple points are. These triple points with higher pressure contribute to the pressure variations behind the standing detonation wave. The higher initial pressure, higher Mach number and larger deflection angle are in favor of formation of stable detonation wave, on the contrary, a regularly spatial instable detonation wave or a deflagration wave, can be formed. Finally, the effects of the different shape of cones on the structures and instabilities of detonation waves were investigated. The results show that the dual cones induce the detonation waves more easily than the single cones which have the same length/radius ratio as the dual one, and the detonation waves induced by the dual cone are more stable than those induced by single cone. The results are significant for the design of structures and the control of stabilities of oblique detonation wave engine.