A Simple Model of Pulsed Ejector Thrust Augmentation
A Simple Model of Pulsed Ejector Thrust Augmentation
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发表时间：
2003-08
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通讯作者：
Jack Wilson
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作者：
Jack Wilson
摘要描述了脉冲源推力增大的一个简单模型。在该模型中，假定进入喷射器的流动是准定常的，并且可以用势流技术来计算。气流的速度与射流形成的起始涡环的速度有关。在已知射流直径、速度和弹塞长度的情况下，根据弹塞模型得到了涡环的特性。该模型与实验结果相结合，预测了增大推力的最佳引射器半径。采用哈特曼-斯普林格管作为脉冲射流源，获得了与模型比较的脉冲引射器性能数据。以喷射器长度、直径和机头半径为独立参数，在四种不同的频率下进行了统计实验。这些频率对应于四个不同的弹状物长径比，两个在截止点以下，两个在截止点以上。模型与实验数据的比较表明，模型与实验数据吻合较好。对于长径比等于截止值的脉冲源，脉冲推力增大最大。
Summary A simple model of thrust augmentation from a pulsed source is described. In the model it is assumed that the flow into the ejector is quasi-steady, and can be calculated using potential flow techniques. The velocity of the flow is related to the speed of the starting vortex ring formed by the jet. The vortex ring properties are obtained from the slug model, knowing the jet diameter, speed and slug length. The model, when combined with experimental results, predicts an optimum ejector radius for thrust augmentation. Data on pulsed ejector performance for comparison with the model was obtained using a shrouded Hartmann-Sprenger tube as the pulsed jet source. A statistical experiment, in which ejector length, diameter, and nose radius were independent parameters, was performed at four different frequencies. These frequencies corresponded to four different slug length to diameter ratios, two below cut-off, and two above. Comparison of the model with the experimental data showed reasonable agreement. Maximum pulsed thrust augmentation is shown to occur for a pulsed source with slug length to diameter ratio equal to the cut-off value.