液力透平进口截面对蜗壳内压力脉动的影响

Effect of Entrance Section of Hydraulic Turbine on Pressure Pulsations within Volute

为研究液力透平不同进口截面对蜗壳内压力脉动的影响,选取一单级液力透平为研究对象,利用流场分析软件CFD对该液力透平内流场进行三维非定常数值计算,在蜗壳内沿周向和径向设置监测点,计算各监测点在不同进口截面和最优工况下沿周向和径向的压力脉动,以及各监测点在不同流量和不同进口截面下沿径向的压力脉动,利用快速傅里叶变换对各监测点的压力脉动计算结果进行变换,分析各监测点处压力脉动的时域和频域分布。结果表明:蜗壳进口直径越大,隔舌处的压力脉动幅值越大;蜗壳进口直径越小,叶轮动静相干作用越强,蜗壳内压力脉动幅值越大;流量越大,不同蜗壳进口截面下蜗壳内压力脉动主频幅值之间相差越小;当离心泵用作液力透平时为了使液力透平能够较稳定运行,需适当减小液力透平进口截面面积。

In order to study the effect of the different entrance sections of hydraulic turbine on pressure fluctuation within volute, a single stage hydraulic turbine was selected, and internal flow field of hydraulic turbine was calculated by using software CFD. We set monitoring points along the circumference and radial direction of volute and calculated the pressure fluctuation along the circumference and radial direction at each monitoring points under the different entrance sections and the optimum conditions of hydraulic turbine. Pressure fluctuation were also calculated along the radial direction at each monitoring points under the different entrance sections and the different flow rates, and the results of numerical calculation were dealt with at each monitoring points by using FFT. We analyzed the distribution rule of time domain and frequency domain of pressure fluctuation at each monitoring points. The results show that the greater the inlet diameter of volute is, the greater the pressure pulsation would appear at the tongue. The smaller the inlet diameter of volute is, the greater the intensity of dynamic and static coupling between the impeller and the volute would present. These lead to big- ger amplitude of pressure fluctuation in the volute. With the increase of flow rate, the difference value of amplitude of dominant fre- quency gradually decreases in the volute under the different volute import. When the centrifugal pump is used to hydraulic turbine, in order to make hydraulic turbine to steady work, the area of entrance section of hydraulic turbine should be appropriately reduced.