Effects of inlet conditions on low swirl combustion flame stability

A numerical simulation of premixed methane-air gas at equivalence ratio 0.7 was conducted to investigate the flame stability of the low swirl combustion under the conditions of different bulk velocity from 10.12 m/s to 40.00 m/s, inlet temperature from 300 K to 500 K and inlet pressure from 101.325 kPa to 8×101.325 kPa. Mechanism of the combustion stability was revealed by analysis of flow field structure and flame characteristics of the low swirl injector. The results show that the bulk velocity, inlet temperature and inlet pressure exert small influences on the flow field structure, so the self-similar characteristics of the low swirl combustion remain. The mean axial aerodynamic stretch rate, the mean radial aerodynamic stretch rate and the virtual origin are almost not affected by the inlet conditions, which facilitates protecting the stability of flame front. The possibility of backfiring reduces with the increasing bulk velocity or the inlet pressure, while the possibility of backfiring increases with the increasing inlet temperature. The flame front of low swirl combustion retains its stability under wider inlet conditions.