双吸离心泵压力脉动特性数值模拟及试验研究

Numerical simulation and tests for pressure fluctuation characteristics in a double-suction centrifugal pump

为深入了解双吸离心泵内部非定常压力脉动特性,对一台双吸离心泵在0.6 Q d、0.8 Q d、1.0 Q d和1.2 Q d工况下的压力脉动特性进行了试验和数值模拟研究,得到了吸水室和蜗壳壁面上3个监测点的压力脉动时频域特性及泵内部压力脉动强度分布。对比试验和数值模拟的泵外特性和监测点的压力脉动功率谱密度,验证了数值模拟的准确性。结果表明:在设计工况和小流量工况下吸水室监测点处叶频是压力脉动的主频,在1.2 Q d时主频转变为轴频,且轴频的幅值随流量变化较小;因吸水室顶部漩涡较多,采用SST k-ω模型进行数值模拟未能准确预测吸水室中的压力脉动。蜗壳上监测点的压力脉动主频为叶频,其振幅随流量的增加先减小后增大,由于蜗壳内压力脉动主要原因为叶轮和蜗壳的动静干涉作用,数值模拟可以准确预测蜗壳中的压力脉动。在小流量时蜗壳出口处监测点的压力脉动主频为轴频,在设计工况和大流量时为叶频,但由于数值模拟未考虑环境因素,使得其结果与试验有偏差。蜗壳中压力脉动强度随着流量增加先降低后变大,在设计工况最低,在设计流量和大流量工况下隔舌断面上压力脉动强度对称分布。

In order to study deeply unsteady pressure fluctuation characteristics inside a double-suction centrifugal pump,numerical simulation and tests were conducted for the pump under multiple operating conditions to obtain pressure fluctuation characteristics in time and frequency domains at 3 monitoring points in suction chamber and volute wall and pressure fluctuation intensity distribution inside the pump.The pump characteristics and pressure pulsation power spectral density at monitoring points obtained in tests were compared with those obtained in numerical simulation to verify correctness of numerical simulation.Results showed that under designed operation condition and small flow rate one,blade frequency at the monitoring point in auction chamber is the dominant frequency of pressure fluctuation,while under 1.2 Q d operation condition,the dominant frequency becomes shaft frequency,and amplitude of shaft frequency has smaller variation with varying of flow rate;due to more vortexes on top of suction chamber,numerical simulation with the SST k-ωmodel can’t predict pressure fluctuation inside suction chamber;duo to rotor-stator interaction between impeller and volute,the dominant frequency at the monitoring point on volute wall is blade frequency,its amplitude firstly decreases and then increases with increase in flow rate,numerical simulation can correctly predict pressure fluctuation inside volute;under small flow rate condition,the dominant frequency of pressure fluctuation at the monitoring point of volute outlet is shaft frequency,while under designed condition and large flow rate one,it is blade frequency,due to not considering environment factors,simulation results deviate from test ones;the pressure fluctuation intensity in volute firstly decreases and then increases with increase in flow rate;during the lowest design condition,the pressure fluctuation intensity on the pump’s tongue section is symmetrically distributed under designed flow rate and large flow rate conditions.