Numerical study on enhancing propagation stability of semi-confined detonation waves by increasing inert gas temperature

This is the authors' abstract. We don't add key points for this paper.

To sustain the propagation of rotating detonation waves, a method for suppressing triple-point escape in gas interfaces is proposed in this paper. The attached oblique shock (AOS) or detached oblique shock (DOS) configuration of shock–detonation complexes at gas interfaces is governed by the acoustic impedance ratio. The low impedance ratio between the high-temperature combustion products and the low-temperature injected explosive mixtures yields the DOS configuration, which enables the stable propagation of detonation waves. To determine the critical inert-gas temperature T* for the transition between AOS and DOS configurations, the flow field of detonation transmission is theoretically resolved. Polar analysis identifies the dimensionless threshold temperature T* = 1.51 for hydrogen–oxygen–nitrogen mixtures. The reactive Euler equations with a two-step Arrhenius chemistry model are adopted. Numerical results verify the temperature threshold and reveal the complex structure of the DOS configuration. Numerical simulations of multi-head detonation transmission are conducted to investigate the confinement effect of inert gas layers. Under the conditions of T* = 1.44, 2.25, and 4.44, the triple-point reflection ratios of detonation waves at the gas interfaces are 0%, 20.0%, and 66.76%, respectively. It was found that the DOS configuration continuously expands in scale. As the length of its branched transmitted wave (BTW) grows to approximately the induction length of detonation, two transverse waves and a high-pressure induction zone (HPIZ) form. The collision between the triple point and the two transverse waves compresses the HPIZ, triggers an explosion, induces the triple-point reflection, and constitutes the formation mechanism of detonation cellular patterns. A higher T* shortens the time required to form a BTW with a size comparable to the detonation transverse wave, thereby enhancing triple-point reflection. The findings of this study can provide a reference for the working condition design of rotating detonation waves.