Load oscillations caused by unstart of hypersonic wind tunnels and engines
Load oscillations caused by unstart of hypersonic wind tunnels and engines
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DOI：
10.2514/2.5287
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发表时间：
1998-05-01
影响因子：
1.9
通讯作者：
Izumikawa, M
中科院分区：
文献类型：
--
作者：
Shimura, T;Mitani, T;Izumikawa, M
高超声速发动机模型在自由射流式风洞中进行试验时，观察到了大幅度的载荷振荡。为了阐明振荡的原因及其特性，对阻力模型和发动机模型上的振荡壁压和载荷进行了研究。利用阴影法观察了流场，分析了起动载荷大的原因。通过快速傅立叶变换，得到了壁压和载荷的功率谱密度函数和概率函数。非定常锋面压力的幅值与动压相关。起动载荷的大小与模型的阻力系数有关，并对大型冲压发动机试验设备的预期最大峰值载荷进行了评估。发动机未起动负荷也通过二次流喷射到一个小比例模型的冲压发动机模拟。利用这些方法，研究了发动机不起动负荷的特性和早期感知发动机不起动的可能性。发动机不起动可以在其变得严重之前通过发动机喉部周围的压力测量来感测。此外，与超燃冲压发动机燃烧相关的发动机未起动载荷与发动机的阻力系数有关。
Large-amplitude load oscillations were observed during the tests of a hypersonic engine model in a freejet-type wind tunnel. To clarify the cause of the oscillations and their characteristics, oscillating wall pressures and loads on a drag model and engine models were investigated. Flowfield was observed by shadowgraph to determine the cause of the large starting loads. Power spectral density functions and probability functions of wall pressures and loads were derived by the fast Fourier transform. The amplitude of the unsteady frontal pressure was correlated with the dynamic pressure. The magnitude of the starting load was related to the drag coefficient of the models, and the expected maximum peak loads of a large-scale ramjet engine test facility were evaluated. Engine unstart loads were also simulated by means of secondary flow injection into a small-scale model of a ramjet engine. With these methods, characteristics of engine unstart loads and the possibility of sensing engine unstart in its early phase were studied. Engine unstart could be sensed with pressure measurement around the engine throat before it became severe. Furthermore, engine unstart loads associated with scramjet engine combustion were related to the drag coefficient of the engine.