不同进口截面下液力透平非定常压力脉动计算

为了研究不同进口截面对液力透平内压力脉动的影响,利用CFX软件对一单级液力透平进行非定常数值计算,通过设置监测点,计算各监测点在不同进口截面下的压力脉动,通过快速傅里叶变换将其压力脉动计算结果做相应分析,分析各监测点处压力脉动的时域和频域分布.结果表明:蜗壳内在大蜗壳进口下,随着蜗壳进口直径的增加,每个监测点处的压力逐渐增加,而在小蜗壳进口下,每个监测点处的压力逐渐减小.在距离蜗壳收缩管较远处,大蜗壳进口下的压力脉动较小,而在距离收缩管较近处,小蜗壳进口下的压力脉动较小.在叶轮内不同进口截面压力脉动的差异在同一时刻从进口到出口逐渐减小.尾水管内在小蜗壳进口下尾水管进口处的压力脉动最大. 

Unsteady calculation of pressure pulsations within hydraulic turbine under different entrance sections

In order to study effect of different entrance sections on pressure pulsation within hydraulic turbine, a single stage hydraulic turbine was selected, and the internal flow field of hydraulic turbine was calculated and analyzed by software CFX; by setting the monitoring points in each flow components, the pressure pulsation at each monitoring points under different entrance sections was calculated; finally, the calculation results of pressure pulsation were switched by means of fast Fourier transformation(FFT) algorithm, and the distribution of time domain and frequency domain at each monitoring point was analyzed. Result show that with the increase of entrance diameter of volute, the pressure gradually increased at each monitoring point under the larger entrance of volute in the volute, but the pressure gradually decreased at each monitoring point under the smaller entrance of volute. The pressure pulsation was less under the larger entrance of volute when the monitoring points and the shrinkage tube were a greater distance apart, but the pressure pulsation was less under the smaller entrance of volute when the monitoring points and the shrinkage tube were a smaller distance apart. The difference of pressure pulsation of different entrance sections gradually decreased from entrance to outlet at the same time in the impeller. The pressure pulsation of draft tube entrance was maximum under the smaller entrance of volute in the draft tube.