Effect of swirler vane angle on the combustion characteristics of premixed lean hydrogen-air mixture in a swirl micro-combustor

This study analyses the influence of swirler vane angle (beta) on the combustion characteristics of premixed lean hydrogen-air flame in a swirl micro-combustor via numerical simulations. The results show that lower flammability limit (LFL) under beta = 15 degrees is larger than that of beta = 0 degrees; and beta = 30 degrees, 45 degrees and 60 degrees have very little difference in the LFL, and their LFL are smaller than that of beta = 0 degrees Flame anchoring mainly depends on the corner recirculation zone (CRZ) when beta is 0 degrees and 15 degrees, and when beta exceeds 30 degrees, flame anchoring is chiefly determined by the inner recirculation zone (IRZ). The flame stabilization ability of IRZ is stronger than that of CRZ, but excessive swirling intensity will increase the length of IRZ, which in turn results in a decrease in stabilization ability. Increasing beta improves outer wall temperature when inlet velocity is relatively small. Under a larger inlet velocity, an enormous beta reduces combustor thermal performance and combustion efficiency due to the downstream movement of flame root and reaction zone. This work helps us to better understand the swirling flame characteristics in micro-combustor and provides guidance for the design and optimization of swirl microcombustor.