Investigation of a variable geometry combined cycle engine inlet with double passage

Combined cycle engines, used for the spaceflight launch vehicle, have wide Mach number operation range. Therefore, a variable geometry inlet scheme with double passage regulation was put forward in the paper. The inlet inner passage was divided into two passages by a baffle. The lower passage could be close by rotating the last compress face at high fight Mach number, so only the upper passage allows air flow into the engine. The wide operation range regulation of inlet compress angle and contraction ratio could be achieved at the same time. Investigation shows that: present variable geometry inlet has higher total pressure recovery coefficient from flight Mach number 2.2 to 7.0, especially higher flow coefficient, and proper exit Mach number during most of the Mach number range. It is most important that the inlet has high mass flow during the wide flight Mach number. In addition, the regulation process is simple, dependable and easily actualized.