Effects of velocity shear layer on detonation propagation in a supersonic expanding combustor

Abstract

This study investigates the mechanism of detonation propagation in a stoichiometric hydrogen-oxygen mixture with non-uniform flow velocity entering an expanding combustor. For simulation of the detonation propagation, the Navier-Stokes equations with a one-step two-species chemistry model are solved by employing the hybrid sixth-order weighted essentially non-oscillatory centre difference scheme. The self-sustaining mechanism of detonation propagation in an expanding combustor under the action of non-uniform supersonic flow with a velocity shear layer is revealed. The results show that under the influence of velocity shear layer, two different unburned jets are produced behind the detonation front. These jets are induced by the velocity shear layers and the Prandtl-Meyer expansion fan. The two jets interact and mix gradually. The interaction between the mixed unburned jets and highly unstable shear layers creates large-scale vortices that intensify the turbulent mixing of the unburned jets. Meanwhile, the baroclinic mechanism generates numerous vortices on the boundary of the unburned jet. These vortices promote the mixing of the burned and unburned gases, which eventually leads to the rapid consumption of the unburned pockets. The heat released due to the burning of the unreacted pockets behind the detonation wave, supports a self-sustaining propagation of the detonation wave. When the velocity difference among the shear layers increases, the surface fluctuation of the detonation wave increases.

Numerical Investigation on Detonation Initiation and Propagation with a Symmetric-Jet in Supersonic Combustible Gas

“…The interaction of the vortex formed by the dual jet in the static air flow field and the combustion front enhances the intensity of the turbulence, which contributes significantly to the detonation process [18]. To accurately simulate small-scale flow details such as turbulence and vortices, the two-dimensional Navier-Stokes equation is adopted as the governing equation [29].…”

Generation mechanism of a new type of unburnt gas pocket and its influences on the detonation-wave/boundary-layer interaction

“…In uniform supersonic flows, experimental analyses demonstrated that the propagation speed of the leading detonation wave in straight tubes is closely related to the ratio of the height occupied by the detonation wave to the height of the duct [8]. While in nonuniform supersonic flows, the self-sustaining mechanism of the detonation propagation becomes more complicated owing to the interaction with a velocity shear layer [9]. Since the combustion mechanisms in the mainstream and boundary layers are totally different owing to shock bifurcations and boundary limit, it is of great importance to distinguish the combustion modes/propagation modes of the detonation wave in the DWBLI [38][39][40].…”

Insight Into Supersonic Combustion Using High-order Simulations

“…Researchers have looked into various aspects of scramjet combustion phenomena. These include the mechanism of detonation propagation; shock impingement at the inlet; flame acceleration and deflagration to detonation transition; solid-fueled scramjets; supersonic hydrogen jet in a crossflow configuration; computational analysis of high-speed combustors, such as HyShot II and the DLR experimental rig, and staggered ramp and strut injector configurations [4][5][6][7][8][9][10][11] . Due to the extreme flow environment, experimental measurements are difficult to be obtained and encompass many uncertainties.…”