不同导叶数下液力透平蜗壳内压力脉动计算

Calculation of pressure fluctuation within volute of hydraulic turbine under different guide vane numbers

当离心泵作液力透平运行时其内存在振动现象,为了使液力透平能够稳定运行,在液力透平蜗壳出口设计不同数量的导叶,然后在不同导叶数下利用Pro/e软件建立几何模型,并利用ANSYS-CFD软件通过在蜗壳内沿周向和径向设置监测点,计算在不同导叶数下液力透平蜗壳内的压力脉动幅值,之后通过快速傅里叶变换将压力脉动的计算结果进行数据处理,分析不同导叶数下液力透平蜗壳内的压力脉动频域分布和液力透平机组内的振动情况.研究结果表明:当导叶数等于9时,蜗壳内周向和径向各监测点处的压力脉动主频幅值最小;蜗壳内径向各监测点处的压力脉动主频幅值和最大脉动幅值随着流量的增加而增大,但随着导叶数的增加其增大程度逐渐减小;当液力透平蜗壳出口添加导叶数为9的导叶时有效降低了液力透平机组内的振动和噪声,提高了液力透平机组运行时的稳定性.

Vibration phenomenon exists when centrifugal pump is operated as hydraulic turbine. In order to make hydraulic turbine operate stably, the volute outlet of hydraulic turbine was designed with different guide vane numbers; then, the geometric models were established using Pro/e software under different guide vane numbers; the monitoring points were set using ANSYS-CFD software along circumferential and radial directions of volute, and amplitudes of pressure fluctuation within volute of hydraulic turbine were calculated under different guide vane numbers; afterwards, the calculational results of pressure fluctuation were transformed by fast Fourier transform, and the distribution of frequency do- main of pressure fluctuation in volute and vibration in hydraulic turbine were analyzed under different guide vane numbers. Investigation results show that the dominant frequency ampli- tude of pressure fluctuation is minimal along circumferential and radial directions of volute when the guide vane number is equal to 9. With the increase of flow rate, dominant frequen- cy amplitude and maximum fluctuation amplitude of pressure fluctuation of monitorin points of valute along radial direction gradually increase, but the degree of increase gradually de- creases with the increase of guide vane numbers. When the volute outlet of hydraulic turbine is designed with a set of guide vanes that the guide vane number is equal to 9, the vibration and noise within hydraulic turbine are effectively reduced, and the stability of hydraulic tur- bine is enhanced.