基于推力连续准则的小型涡轮冲压组合发动机模态转换过程分析

基于数值模拟方法开展了小型涡轮冲压组合发动机性能计算与匹配性分析,给出了详细的性能计算流程、设计点参数确定准则和模态转换过程参数计算方法,根据涡喷发动机压气机进口、涡轮出口的总静压参数沿飞行轨迹的变化规律,确定了涡轮模态向冲压模态转换的合理区间,根据冲压燃烧室进口参数和静压平衡等约束条件,确定了小型涡轮冲压组合发动机关键截面几何参数.分析了不同的流最调节阀开度对模态转换过程参数变化的影响,按照推力连续的准则,确定了模态转换过程流量调节阀开度随马赫数的变化规律,最后给出了沿飞行轨迹的涡轮冲压组合发动机推力、比冲和喷管喉道面积的变化.

Analysis of mode transition with thrust smoothing of small turbine/ramjet combined cycle engine

One area of special interest with the turbine/ramjet combined cycle engine concept is system behavior during the transition periods, these are the periods during the flight when the turbojet hands-off to the ramjet. The effects of closing off the turbojet, to protect it from the high Mach airflow, and the matching of turbojet and ramjet engine performance ranges around transition are important areas of interest that have not yet been evaluated. The goal of this study is to establish mathematical model for computing peformance and analyzing the therodynamic parameters variation of turbine/ramjet combined cycle engine during mode transition. Firstly, the computed flow charts of performance and thermodynamic parameters of combined engine, and the critera of determining design parameters of combined engine were given. Secondly, according to computed performance and thermodynamic parameters along flight trajectory and design limitations, such as the Mach number at ramjet burner extrance <0.3, the reasonable mode transition periods were optimized, and geometry parameters of critical section were given. Thirdly, the effect of opening area of mode transition valve on thermodynamic parameters, especially the relations of total and static pressure were analyzed. The quatitative opening area of mode transition valve along flight trajetory were given for satisfing criteria of thrust smoothing. At last, the thrust and ISP of turbine/ramjet combined cycle engine were calculated along flight trajectory.