정적, 동적 출구조건에서의 초음속 흡입구 유동진동 해석 연구

Abstract

Ramjet engine has small throttling ratio in initial launching state and pressure around the engine oscillates in high frequency. Moreover, at that time, throttling ratio is changed abruptly. The flow unsteadiness from throttling ratio changing could bring result in engine unstart or even structure damage to engine. A numerical study was conducted to simulate the pressure oscillation phenomenon that is occurred in small throttling ratio. Simulation and analysis of flow charateristics are not only nuder static throttling condition but also under dynamic throttling condition. Generally, throttling ratio is defined as ratio of throat area and exit area. Throttling ratio 0.70 is threshold between high frequency boundary and low frequency boundary in the present geometry[1] research. Numerical simulation is conducted in 0.55 throttling ratio case and 0.00 that is below 0.70. By the way, the result shows high frequency oscillation between 300 and 400 Hz. Dynamic throttling condition is assumed that throttling ratio can be moved in the range between 0.00 and 0.70. Numerical analysis and discussion of result is conducted for the changing of flow oscillation characteristics under the dynamic throttling condition from the initial condition that pressure oscillation has been already onset.