Numerical and experimental investigation of improving combustion performance of variable geometry dual-mode combustor

As part of our efforts to find ways and means to further improve the combustion performance of variable geometry dual-mode combustor, flow field characteristics and mechanisms of combustion performance losses, which included compression and combustion losses resulted by heat addition, were investigated in variable geometry dual-mode combustor numerically and experimentally with a Mach number of 3.0, a divergent ratio ranging from 1.3 to 1.8 and a fuel equivalence ratio varying from 0.6 to 1.2. Irreversible entropy increase analysis was extended specifically in this paper to study the mechanism of combustion performance loss for the variable geometry dual-mode combustor. Numerical and experimental results indicated that for a given fuel equivalence ratio, the wall static pressure, total pressure recovery coefficient, combustion efficiency and thrust of the variable geometry dual-mode combustor increased with the decreasing of divergent ratio and there was a maximum thrust performance for the divergent ratio of 1.3 within stability margin. It was therefore strongly believed that the combustion performance of a variable geometry dual-mode combustor could be further improved by decreasing divergent ratio.