Spinning Effects on a Trapped Vortex Combustor

Abstract

The trapped vortex combustor concept provides a simple design for flame stabilization by trapping a pilot flame inside a cavity instead of exposing it to the mainstream. Under some circumstances, the combustor may operate in a high-spinning motion (for example, when it is installed in a spin-stabilized ramjet projectile), in which the spinning rate can be as high as 30,000 rpm. The objective of this study is to numerically investigate the effects of high-spinning motion on the trapped vortex combustor, including the cavity vortex dynamics, fuel–air mixing, and combustion performance. Numerical computations have been performed with the Reynolds stress model for turbulence and the eddy dissipation model for combustion in a rotating reference frame. The results of the spinning trapped vortex combustor show that the Coriolis effects dominate the flow in the cavity when it is subjected to a high-spinning motion (30,000 rpm). The vortex breakdown in the cavity brings strong three-dimensional flow and promotes fuel–air mixing so that a stronger cavity pilot flame is generated. But, the effect of the centrifugal force also generates a short recirculation zone in the main combustor and concentrates the fuel stream on the combustor axis, which in turn impairs fuel–air mixing and leads to a longer main combustor flame.