Calculation of Dual-Mode Engine Performance

Abstract

Thrust performance and operating conditions of a dual-mode engine were calculated with a one-dimensional flow model. Pseudo-shock in the isolator in the ramjet mode was modeled with the momentum balance model. The decelerated air at the end of the pseudo-shock showed the highest pressure in the engine in the ramjet mode. The effects of height of the inflow boundary layer, combustion efficiency, and angle of attack were investigated. Larger thrust was produced with larger angle of attack, while specific impulse was unaffected by the angle of attack but by the contraction ratio of the engine. A small change in the combustion efficiency induced a large change in the position of the pseudo-shock in the isolator. Thrust in the ramjet mode was almost the same as that in the scramjet mode at the same flight Mach number.