Effects of the quantity and arrangement of reactive jet obstacles on flame acceleration and transition to detonation: A numerical study

Abstract

Solid obstacles induce the detonation in premixed gases while causing significant thrust losses. Jet obstacles can alleviate this deficiency, but there have been few studies on multi-group reactive jet obstacles. In this study, a detailed numerical simulation is performed to investigate the selection of the quantity of reactive jet obstacles and examine the effect of the arrangement of different jet obstacles on flame acceleration and the deflagration to detonation transition (DDT) processes. The results show that there is an optimal quantity of jet obstacles that can rapidly trigger detonation while reducing thrust loss and combustion chamber weight. In terms of flame acceleration, the mechanisms of flame acceleration by reactive jet obstacles with various arrangement types are complex. Specifically, the initial flame acceleration effect of reactive jet obstacles with different arrangement types is similar. However, the staggered arrangement has a longer-lasting vortex structure, stronger leading compression wave and flow field intensity, which provides favorable conditions for the ensuing flame acceleration. When the flame interacts with the jet, the larger virtual blockage ratio and stronger combustion heat release effect further amplify the flame acceleration discrepancy. In DDT, compared with solid obstacles, reactive jet obstacles have more advantages. Different types of jet obstacles arrangement differ in their ability and method in triggering DDT, with the staggered arrangement having the best DDT effect, and detonation initiation modes are divided into two categories: i) the detonation induced by the coupling of the flame surface and the high-pressure region; ii) the reflected wave impinges on the flame surface after the compression waves in front of the flame collide with the wall, resulting in a detonation. Although the quantity and arrangement of jet obstacles vary in this study, all the cases where detonation occurs are consistent with the flame acceleration model of Liberman and similar SWACER mechanism.