关键词: 单边膨胀喷管, 俯仰力矩差, 膨胀程度, 风洞试验, 推力系数

Abstract:

The single expansion ramp nozzle (SERN) is a key component of a scramjet engine. However, because of its asymmetrical geometry large pitch moment differences exist from the SERN at the start and shut-down moment of the scramjet engine, which seriously affects the stability of the aircraft. To overcome the shortcomings of the existing methods of reducing pitch moment differences which use adjustable nozzles, a nozzle Model B based on controllable expansion degree distribution is presented in this paper. Model B compares with baseline Model A. Cold-flow test and numerical simulation are conducted on the sub-scaled Model B, and their results agree well with each other. The results demonstrate that at flight Mach numbers 4.5 and 6.5, the pitch moment of the cold-state and hot-state of Model B decreases by 80.49% and 12.73% respectively, while the thrust coefficient decreases by 0.1% at flight Mach number 4.5 and increases by 1.1% at flight number 6.5. The pitch moment performance of the SERN is improved significantly, which effectively reduces the difficulty of the aircraft trim. The validity of the design thinking and method is fully verified, which provides a new approach for improving the pitch moment performance of the SERN.

Key words: single expansion ramp nozzle, pitch moment difference, expansion degree, wind tunnel experiment, thrust coefficient