Flow characteristics of a trapped-vortex pilot cavity under the influence of radial structure

Abstract

In this study, using a laboratory-scale combustor model, we examined the flow modes in the trapped-vortex cavity under the influence of a radial bluff-body structure by particle image velocimetry (PIV) technology. The tested area included both inside the cavity and the mainstream zone. It is found that, under different inlet parameters, structure width, and circumferential positions, the flow characteristics change significantly for this structure. The number of vortexes, the distribution of vorticity, and the Q-value differ at different circumferential positions; while the increase in radial structure width, incoming flow velocity, and total pressure will all lead to stronger vortex flow. The flow pattern inside the cavity and behind the radial structure are coupled with each other, forming six typical flow modes. Further theoretical analysis summarized the causes of the six flow modes according to two aspects: how the mainstream influences the cavity flow, and the influence degree of the mainstream on the cavity flow. Considering the effect of the radial structure, the mainstream at different positions will have different effects on the cavity, which can be represented by the ratio of the radial position to the width of the structure. The influence degree was related to the inlet parameters and the width of the radial structure, which can be represented by the dynamic pressure of cavity inlet jets.