Impact Of Heat Addition Amount on The Combustor Design of the Rocket-Based Combined Cycle Engine

Abstract

Rapidly changing and variable ambient conditions impose higher requirements on integral multi-mode rocket-based combined cycle (RBCC) engines. In order to ensure integral operation stability and performance under wide flight speed range, it is necessary to carry out the matching characteristic analysis and research its impact on the combined-cycle engine geometry design. Numerous results in present analysis indicate that the pre-combustion shock in the isolator is critical to balance the pressure difference between intake air and combustion gas. Its position directly determines the inlet’s operation mode. Compared to previous proposed operation mode, there exists a kind of pseudo start mode due to the self-sustained separation adjustment between intake and combustion through the bleed block. In order to meet the inlet operation requirement, the combustor geometry should be designed over its area ratio limit. This low bound is directly determined by the total heat addition and fuel’s caloric value. Present integrated engine performance comparison verifies their relation behaves monotonic. When flight conditions changes, increased air captured amount leading more heat addition results the combustor should be further enlarged. Depending on this relationship, the configuration of a combined-cycle engine working under wide flight speed range can be rapidly obtained.

Keywords: Rocket-based combined-cycle, multi-mode, area ratio, heat addition, fuel