水泵水轮机压力脉动传播特性试验研究

压力脉动是影响水泵水轮机运行稳定性的主要因素。现有研究更多关注高频压力脉动的频域和传播特性，而小于叶频的低频也是压力脉动的主要来源。采用试验方法研究压力脉动可以得到更准确的结果，不易遗漏主要频率成分。通过从蜗壳到尾水管布置不同的压力脉动监测点，采用试验方法研究了水泵水轮机分别在水轮机和水泵工况时，过流部件内压力脉动高频成分和低频成分的上下游传播特性。结果表明，水轮机和水泵工况下，无叶区压力脉动幅值最大，主频为叶频及其倍频，向上下游传播时，急剧减少，传播性较弱；压力脉动幅值较小的转频，向上下游传播时衰减较少，具有较强的传播性；其它监测点处小于叶频的频率成分增加。水轮机工况时，形成于蜗壳进口和锥管处小于转频的低频频率，具有较强的传播性，而转轮可以削减其传播能力。水泵工况时，小于叶频的频率成分大多在无叶区最大，向上下游传播时有所衰减；低频f/f_n=0.006具有较强的上下游传播特性，偏离最优工况时，向上游传播会有所增强；转频的倍频f/f_n=3的压力脉动幅值较小，但在整个流道中无衰减。

Experimental Investigation on Transmission Characteristics of Pressure Fluctuation in Pump-turbine

Pressure fluctuation is the main factor affecting the operation stability of pump turbine. In the existing studies, the frequency domain and transmission characteristics of high frequency pressure fluctuation were investigated, while low frequencies less than blade frequency were also the main sources of pressure pulsation. Comparing with numerical simulation, more accurate results can be obtained with experimental method. The main frequency components were not lost easily. Different pressure fluctuation monitor points from volute to draft tube were arranged. The transmission characteristics of high frequency and low frequency components under turbine operation and pump operation were studied by experimental method separately. The results showed that under both of the turbine and pump operation conditions, the pressure pulsation in the vaneless zone was the largest, and the main frequencies were the blade frequency and its multiple frequencies. These frequencies were decreased sharply when these frequencies propagate toward upstream and downstream, so their propagation characteristics were weak. The attenuation of the rotation frequency with small amplitude was less when it transmitted toward upstream and downstream. So transmission property of the rotation frequency was strong. The frequencies less than the blade frequency were increased at other monitoring points. Under the turbine operation, propagation of the low frequencies less than the rotation frequency forming in the volute and the conical tube of draft turbine was strong, but their propagation ability can be weakened by the runner. Under the pump operation, most of the frequencies less than the blade frequency were large in the vaneless region. The amplitudes of these frequencies were decreased when they were transmitted toward the upstream and downstream. The transmission characteristic of the low frequency f/fn =0.006 was strong toward upstream and downstream. The propagation property toward the upstream was enhanced when the operation condition was deviated from the optimal condition. The amplitude for the multiple frequency of rotation frequency f/fn=3 was small, but its attenuation was less when it was transmitted throughout the flow field.