Flameout characteristics of coaxial jet flame with hetero-type edge lobe mixer in air turbo rocket engine combustor

The primary function of an Air Turbo Rocket （ATR） engine combustor is to achieve efficient combustion between the fuel-rich combustion products in the core flow and the bypass fresh air. The hetero-type edge lobe mixer achieves an integrated design for mixing and flame stabilization by creating multi-source vortex structures in the combustor， which can effectively reduce combustor length and improve the engine’s thrust-to-weight ratio. This paper experimentally investigates the flameout characteristics of coaxial jet flames in ATR engines equipped with hetero-type edge lobe mixers， establishing flameout boundaries and analyzing flame dynamic behavior near flameout conditions through experimental studies. The research findings indicate： （1）As the airflow velocity progressively increases， the blowout velocity of the combustor demonstrates a gradual decrease， while the weak extinction equivalence ratio shows a trend of first decreasing and then increasing. （2）Compared to the basic lobe mixer， adding sawteeth to the mixer edge expands the blowout velocity and the weak extinction equivalence ratio by an average of 21.9% and 35.5%， respectively. （3）Increasing the incidence angle and height of the lobe mixer sawtooth trailing edge structure can enhance flame stability in the combustor. （4）The oscillation pattern of the lobe mixed coaxial jet flame is primarily characterized by low-frequency oscillations coupling pressure and heat release， with high-frequency wavelets superimposed on these low-frequency oscillations. Near blowout conditions， flame stratification oscillations occur with a peak frequency of 30 Hz and approximately 15 Hz bandwidth.