Investigation of the effect of turbulence induced by double non-reactive gas jet on the deflagration-to-detonation transition

摘要

Jet-in-crossflow (JICF) is proved to be advantageous to accelerate flame propagation and stimulate the deflagration-to-detonation transition (DDT) process in the recent decade. Studies focused on the performance of the jet of combustible mixture or reactive gas on facilitating the DDT process are carried out, and the results show that the combustible JICF can promote the flame transition to detonation efficiently. Although most investigations attribute the ability of the JICF on promoting DDT to the turbulent effect induced by the jet, the combustion-enhancement effect of the jet medium is seldom considered. In our previous work, it is proposed that the non-reactive gas jet in an optimal condition can accelerate flame propagation and promote the precursor shock wave formation. Hence, the performance of the multi-jet of non-reactive gas on facilitating the DDT process is worth investigating. In this paper, three different double jet placement methods are designed: parallel, staggered, and opposite positioned, and their performances on accelerating flame propagation and promoting the DDT process are investigated systematically. The results indicate that the staggered jet can accelerate the flame to detonation within a short run-up distance whereas the parallel jet and the opposite jet can only make the flame accelerate slightly. The schlieren images of flame evolution affected by double jet indicate that the complicated reactivity gradients generate on the flame surface while the flame is disturbed by the double jet. The interaction between the staggered jet and the flame induces local explosions, which results in a prominent increase of the flame area and a large volumetric burning rate. For the opposite jet, its negative effect of combustion-inhibition of the aggregated CO_2 overwhelms the positive effect of turbulence-enhancement on the flame acceleration.