并联TBCC排气系统稳态与模态转换实验研究

Experimental study on steady state and mode transition of parallel TBCC exhaust system

关键词:  涡轮基组合循环  排气系统  实验  稳态  模态转换

Key words:  TBCC  Exhaust system  Experiment  Steady state  Mode transition

摘要:

涡轮基组合循环排气系统在稳态工作与模态转换动态过程中性能参数和流场结构的变化规律会对高超声速飞行器总体性能产生巨大影响。为此开展了稳态与动态风洞模型实验研究，测量了喷管模型的流量、六分量力、壁面压力，并拍摄了典型的流场结构纹影照片。采用核密度估计的方法确定了稳态推力系数的测量结果；采用中值滤波结合平滑函数处理的方法获得了模态转换过程的推力系数和矢量角。稳态实验分别固定涡轮通道和冲压通道压比，调节另一通道压比，由于被调节的通道随压比增大从过膨胀逐渐转变为欠膨胀，所以推力系数呈先增大后减小的趋势；双通道喷流干扰产生的桶型激波撞击在涡轮通道上壁面上，改变了壁面压力分布。模态转换动态实验模拟了冲压发动机点火后双通道共同工作加速爬升的过程。在此期间推力系数逐渐减小，矢量角不断增大，且变化趋势与理论分析结果一致；双通道喷流干扰显著改变了冲压通道射流方向。无论是稳态实验还是动态实验，测力结果、测压结果、流场结构纹影照片以及理论分析结果都能互相印证，佐证了实验结果的准确性和可靠性。

Abstract:

The changes of performance and flow field structure of the Turbine Based Combined Cycle exhaust system in the process of steady state operation and mode transition have great effect on the performance of hypersonic aircraft. So steady and dynamic wind tunnel experiments were carried out and the mass flow rate， six-component force， wall pressure were measured and schlieren images of typical flow structure were taken. The measurement results of steady state thrust coefficient is determined by kernel density estimation. The thrust coefficient and thrust vector angle of the mode transition process are obtained by median filtering and smoothing function. In the steady state experiments， the pressure ratio of the turbojet flow path and the ramjet flowpath are fixed respectively， and the pressure ratio of the other flow path is adjusted. Because the regulated channel changes from over-expanded to under-expanded with the increase of the pressure ratio， the thrust coefficient first increases and then decreases. The barrel shock generated by the interaction between two flow paths impinges on the ramp of the turbojet flowpath， and changes the wall pressure distribution. The dynamic experiment of mode transition simulates the acceleration and climbing process of two flow paths working together after ramjet ignition. In this process， the thrust coefficient decreases and the thrust vector angle increases. The change trends are consistent with the theoretical analysis. The interaction between two flow paths significantly changes the jet direction of the ramjet flowpath. Whether it is steady state experiments or dynamic experiment， the results of force measurement， pressure measurement， schlieren images of flow structure and results of theoretical analysis can be mutually verified， which confirmed the accuracy and reliability of the experimental results.