Impact of interaction between cavity flow and mainstream on the performance of a model trapped vortex combustor

Abstract

In trapped vortex combustors, radial strut serves as a critical component for it determines the interaction between cavity flow and mainstream and thus combustion and emission performances. Aiming at this topic, a trapped vortex combustor comprising interchangeable aerodynamic multipoint fueling setup, which have different strut width but same passage area, is designed. Experimental studies are carried out to investigate the combustion efficiency and emission performance. The configuration with wider struts exhibits excellent ability of NOx reduction in all operating conditions. However, relatively higher level of carbon monoxide and hydrocarbon are produced especially under cavity-only conditions, and thus the corresponding combustion efficiencies are lower. Nonreacting computational fluid dynamics results show that it is difficult for cavity flow to rush to the tail of bluff body because slenderer struts cannot provide sufficient protection. Thus, flow pattern and mixing of cavity flow and mainstream are influenced. Residence time of cavity-fore flow is calculated using a novel approach referred to as difference of tracer-pulse response. Reacting flow simulations show a different flow structure from reacting flow. It reveals that cavity flow can partially rush to the tail of bluff body through the channel behind the slenderer struts of configuration-1. However, the mixture fraction and temperature behind the bluff body of configuration-1 are still lower, and thus the NOx formation rate is relative lower.