离心泵蜗舌区非定常流动特性

采用Navier-Stokes方程和RNG k-ε双方程湍流模型，对多工况下离心泵全流道进行了非定常流动数值模拟. 非定常计算得到的离心泵外特性与试验数据吻合较好. 在离心泵蜗舌区设置了3个监测点，计算得到了蜗舌区流体瞬态速度矢量分布，各监测点的压力、径向速度、周向速度的脉动时域特性，并对其进行了分析. 结果表明:设计工况下，蜗舌区流动比较均匀，压力和速度脉动幅度较小. 大流量工况下，在叶轮出口的射流-尾迹结构影响下，各监测点的压力和速度随叶片转动出现相应的峰值和谷值. 小流量工况下，蜗舌区内存在绕蜗舌顶端逆向流动、叶轮出口回流、蜗舌附近蜗型段内旋涡，使得流动非常复杂，流体压力和速度脉动幅度较大，压力最大值约为最小值6倍. 

Characteristic of Unsteady Flow Around the Tongue Region in a Centrifugal Pump

On the basis of the Navier-Stokes equations and RNG k-ε turbulent model, the numerical simulations of unsteady flow around the tongue region for five flow rates in a centrifugal pump were performed. The pump performances obtained from the unsteady numerical simulations were well coincident with the experiment results. Three monitor points around the tongue region were set to record the time evolution of pressure and velocity variations. The instantaneous vector maps of velocity for three flow rates were captured. The numerical results show that the flow fields are even in the tongue region with small pulsations of pressure and velocity at the design flow rate. The maximum and minimum values of pressure and velocity on monitor points are affected by the well known jet-wake pattern which exists at the impeller exit in the large flow rate. For the small flow rate, there are reverse flows around the tongue tip, back flows from the tongue region to the impeller, and vortexes in the worm section adjacent to the tongue. All these phenomena interacting in the tongue region make the flow complex with considerable fluctuations, where the maximum value of the pressure is 6 times of the minimum value.