Experiment and simulation study on lean blow-out of trapped vortex combustor with various aspect ratios

This paper investigated the lean blow-out (LBO) performance of several combustors which utilized trapped vortex in the cavity to improve the flame stability. Experiments and simulation study had been performed for various height to length (Hf/L) ratios of the cavity. The experiment results showed that the minimum pressure drop across the combustor occurred when the Hf/L ratio was 0.8; and that very low overall LBO equivalence ratios were observed over a wide range of primary air flows at the same H/L ratio. In the simulations, the large eddy simulation (LES) was used to predicate the transient flow field in the cavity. Simulation results showed that the core of the trapped vortex was in the middle of the cavity at Hf/L=0.8, and the velocity profile of the vortex was better organized than those of other combustors with different Hf/L ratios. Moreover, the simulated period of vortex swirling was the shortest at Hf/L=0.8. Therefore, the experimental observations on the LBO performance of several combustors with different Hf/L ratios were well explained by the present simulation results. Based on the experimental data, a preliminary study of the empirical correlation of LBO was conducted on trapped vortex combustor (TVC). Compared with Lefebvre's empirical correlation, the proposed new empirical correlation has better agreement with the experimental data.