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

Abstract

This study analyses the influence of swirler vane angle (β) 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 β = 15° is larger than that of β = 0°; and β = 30°, 45° and 60° have very little difference in the LFL, and their LFL are smaller than that of β = 0° Flame anchoring mainly depends on the corner recirculation zone (CRZ) when β is 0° and 15°, and when β exceeds 30°, 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 β improves outer wall temperature when inlet velocity is relatively small. Under a larger inlet velocity, an enormous β 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 micro-combustor.