Experiments have been carried out to investigate the effect of cowl length variation on performance characteristics of a single expansion ramp nozzle. The performance parameters were estimated for cowl lengths of 0, 25, 50, 75, and 100% with respect to the horizontal length of the ramp. Experiments were conducted for different nozzle pressure ratios ranging between 1.5 and 9. The wall static pressure distribution data were measured from the tests to estimate the various performance parameters, such as axial thrust, normal force, gross thrust, thrust vectoring angle, and coefficient of pitching moment. High-speed schlieren imaging was used to visualize the flow separation and shock patterns and to measure the jet width. The flow was separated from the ramp wall up to a nozzle pressure ratio of 3 for all cowl cases. The shorter cowl length delays the downstream movement of shock-induced boundary separation inside the nozzle as compared to the longer cowl. The cowl trailing-edge flow was more underexpanded than the ramp tip flow. As cowl length increases, the increased restriction results in higher axial thrust and also increases the normal force. The pitching moment and thrust vectoring were dominated by normal force. Overall, as the nozzle pressure ratio increases, the axial force and jet width increase, whereas the normal force and the pitching moment increase up to a certain level and then decrease. As the cowl length increases, the axial thrust, normal thrust, pitching moment, and thrust vector angle increase, while the jet width decreases.

已经进行了实验以研究前围长度变化对单个膨胀斜面喷嘴的性能特征的影响。相对于坡道的水平长度，对前围长度为0、25、50、75和100％的性能参数进行了估计。针对1.5至9之间的不同喷嘴压力比进行了实验。从测试中测量了壁静压力分布数据，以估算各种性能参数，例如轴向推力，法向力，总推力，推力矢量倾角和最大推力系数。投球时刻。高速schlieren成像用于可视化流动分离和冲击波，并测量射流宽度。对于所有前围箱，气流与坡道壁分开，直至喷嘴压力比为3。与较长的前围板相比，较短的前围板长度延迟了喷嘴内部激振引起的边界分离的下游运动。前围后缘流比坡道末梢流膨胀不足。随着前围长度的增加，增加的限制会导致更高的轴向推力，并且还会增加法向力。俯仰力矩和推力矢量主要由法向力决定。总的来说，随着喷嘴压力比的增加，轴向力和射流宽度增加，而法向力和俯仰力矩增加到一定水平，然后下降。随着前围长度的增加，轴向推力，法向推力，俯仰力矩和推力矢量角都会增加，而射流宽度则会减小。前围后缘流比坡道末梢流膨胀不足。随着前围长度的增加，增加的限制会导致更高的轴向推力，并且还会增加法向力。俯仰力矩和推力矢量主要由法向力决定。总的来说，随着喷嘴压力比的增加，轴向力和射流宽度增加，而法向力和俯仰力矩增加到一定水平，然后下降。随着前围长度的增加，轴向推力，法向推力，俯仰力矩和推力矢量角都会增加，而射流宽度则会减小。前围后缘流比坡道末梢流膨胀不足。随着前围长度的增加，增加的限制会导致更高的轴向推力，并且还会增加法向力。俯仰力矩和推力矢量主要由法向力决定。总的来说，随着喷嘴压力比的增加，轴向力和射流宽度增加，而法向力和俯仰力矩增加到一定水平，然后下降。随着前围长度的增加，轴向推力，法向推力，俯仰力矩和推力矢量角都会增加，而射流宽度则会减小。总的来说，随着喷嘴压力比的增加，轴向力和射流宽度增加，而法向力和俯仰力矩增加到一定水平，然后下降。随着前围长度的增加，轴向推力，法向推力，俯仰力矩和推力矢量角都会增加，而射流宽度则会减小。总的来说，随着喷嘴压力比的增加，轴向力和射流宽度增加，而法向力和俯仰力矩增加到一定水平，然后下降。随着前围长度的增加，轴向推力，法向推力，俯仰力矩和推力矢量角都会增加，而射流宽度则会减小。