带第三流路辅助进气的引射喷管流动特性研究

为避免低落压比条件下引射喷管内气流过膨胀，本文研究了第三流路辅助进气门开启状态下引射喷管的内流特性，分析了飞行马赫数为0，主喷管落压比为2.1，次流流动状态分别为回流和顺流对引射喷管流动特性的影响规律，并获得了不同辅助进气门开度下次流通道的最小顺流压比。结果表明：当次流为回流状态时，逐渐增加辅助进气门开度，主流过膨胀程度逐渐降低，第三流路流量的增加使剪切层内动量传递效率提高，引射喷管的推力系数从0.60提升至0.73；当次流为顺流状态时，随着辅助进气门开度的增加，次流流量减少，主流过膨胀程度逐渐增大，第三流路流量的增加使剪切层内动量传递效率降低，推力系数则从0.97下降至0.75。次流为顺流状态时引射喷管的推力系数整体高于次流为回流状态，因此当次流处于顺流状态时引射喷管取得更优的推力性能。但在低马赫数状态下，次流流动极有可能出现倒流，此时适当增加辅助进气门的开度有益于改善推力性能。随着辅助进气门开度逐渐增大，次流的最小顺流压比呈逐渐上升趋势。

Flow Characteristics of an Integrated Ejector Nozzle with Tertiary Intake

In order to avoid overexpansion of the flow in the ejector nozzle under low pressure ratio, the flow characteristics in an integrated ejector nozzle with tertiary door are investigated. The effects of the secondary flow states, i.e., reversed flow and downstream flow, on the ejector flow features are analyzed under the flight Mach number of 0 and the nozzle pressure ratio (NPR) of the primary flow of 2.1. And the minimum downstream pressure ratios at different opening angles of tertiary door have been obtained. The results show that when the secondary flow is in the reversed flow state, with the increasing of the opening angle of the tertiary door, the overexpansion degree of the mainstream gradually decreases. The mass flow rate of the tertiary flow increases, which arises the momentum transfer efficiency in the shear layer, leading to an ascending tendency of the thrust coefficient from 0.60 to 0.73. When the secondary flow is in the downstream flow state, the secondary mass flow rate descends and the overexpansion degree of the mainstream gradually increases with the opening angle of tertiary door. The increase in the mass flow rate of the tertiary flow lowers the momentum transfer efficiency in the shear layer, resulting in a decreasing thrust coefficient from 0.97 to 0.75. As the thrust coefficient in the downstream flow state is higher than that in the reversed flow state, a better thrust performance could be attained in the downstream flow state. Nevertheless, the secondary flow may be reversed under low flight Mach number, it is beneficial to increase the opening angle of tertiary door to improve the thrust performance in this state. Furthermore, as the angle of the tertiary door gradually increases, the minimum downstream pressure ratio of the secondary flow shows an increasing trend.