Spinning Effects on a Trapped Vortex Combustor

摘要

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.