Choked Surge in a Cavitating Turbopump Inducer
Choked Surge in a Cavitating Turbopump Inducer
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DOI：
10.5293/ijfms.2008.1.1.064
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发表时间：
2008-08
影响因子：
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通讯作者：
Toshifumi Watanabe;D. Kang;A. Cervone;Y. Kawata;Y. Tsujimoto
中科院分区：
文献类型：
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作者：
Toshifumi Watanabe;D. Kang;A. Cervone;Y. Kawata;Y. Tsujimoto
在对一个三叶片和一个四叶片轴流诱导轮的实验研究中，观察到了严重的喘振不稳定性的空化数范围内，叶片通道被阻塞，诱导轮头部从非空化值下降。与具有相同的进口和出口叶片角度的3叶片诱导轮相比，4叶片诱导轮的喘振更强。对于四叶诱导轮，随着空化数的减小，扬程突然减小。在水头突然下降后，观察到浪涌。发现这种水头下降与叶顶空腔迅速延伸到叶片通道中有关。喘振的原因是由于阻塞引起的水头-流量特性曲线负斜率的减小。假设3叶片诱导轮和4叶片诱导轮之间的差异是由叶片阻塞效应的差异引起的，通过加厚3叶片诱导轮的叶片进行了试验。然而，与预期相反，头部下降变得更加平滑，加厚叶片诱导轮上的不稳定性消失。对两种诱导器上的压力分布的检查无法解释这种差异。有人指出，二维空化流分析预测较小的破裂空化数在较高的流量，如果冲角小于一半的叶片角。这导致性能曲线的正斜率，并表明在本研究中观察到的扼流喘振可能发生在更一般的情况下。
During an experimental investigation on a 3-bladed and a 4-bladed axial inducer, a severe surge instability was observed in a range of cavitation number where the blade passage is choked and the inducer head is decreased from noncavitating value. The surge was stronger for the 4-bladed inducer as compared with a 3-bladed inducer with the same inlet and outlet blade angles. For the 4-bladed inducer, the head decreases suddenly as the cavitation number is decreased. The surge was observed after the sudden drop of head. This head drop was found to be associated with a rapid extension of tip cavity into the blade passage. The cause of surge is attributed to the decrease of the negative slope of the head-flow rate performance curve due to choke. Assuming that the difference between the 3 and 4-bladed inducers is caused by the difference of the blockage effects of the blade, a test was carried out by thickening the blades of the 3-bladed inducer. However, opposite to the expectations, the head drop became smoother and the instability disappeared on the thickened blade inducer. Examination of the pressure distribution on both inducers could not explain the difference. It was pointed out that two-dimensional cavitating flow analyses predict smaller breakdown cavitation number at higher flow rates, if the incidence angle is smaller than half of the blade angle. This causes the positive slope of the performance curve and suggests that the choked surge as observed in the present study might occur in more general cases.