Experimental study on the effects of different fluidic jets on the acceleration of deflagration prior its transition to detonation

Abstract

Fluidic jet-in-crossflow (JICF) is a reliable technique facilitating the flame acceleration and the transition from deflagration to detonation, most previous investigations on this project have focused on JICF using combustible mixtures but there are relatively few studies explored the mechanism of non-reactive gas JICF in the process of deflagration-to-detonation transition (DDT). In this study, three non-reactive gases (i.e., He, N2 and CO2) are considered as the medium of fluidic jets, the detailed mechanism of JICF enhancing deflagrations in stoichiometric methane-oxygen mixture is discussed. We experimentally demonstrate that JICF prominently enhances the propagation characteristics of deflagration, i.e., the 1st shock wave (1st SW), the 2nd shock wave (2nd SW), the combustion wave (CW) and the formation of precursor shock wave. Non-reactive gas JICF has concurrently positive turbulence-enhancement as well as negative inert gas-inhibition effects, which simultaneously influence the propagation behavior of deflagration. By adjusting the pressure difference (i.e., pJ0/p0) in JICF and test mixture, the performance of non-reactive gas jet on the propagation characteristics of deflagration is varied and mainly dependent on the attributes of the JICF. Our observation sheds light on the competing mechanism of JICF in the acceleration of a deflagration.