斜流泵小流量工况压力脉动数值模拟与实验

摘要

The pressure fluctuation experiment was conducted and the entire flow field of mixed-flow pump was simulated by large eddy simulation (LES) with standard Smagorinsky subgrid scale model to investigate pressure fluctuations and mixed-flow pump inner flow under low flow conditions.The experimental results indicated that the multiples of pressure fluctuation at the impeller inlet was the highest and it was increased when the flow rate was decreased.the main pressure fluctuation frequencies at the impeller inlet,impeller ouflet and vanes inlet were blades passing frequency under different conditions,however,the main pressure fluctuation frequencies at the vanes outlet was changed under different conditions.The large eddy simulation results indicated that the flow conditions at impeller inlet was better and axial velocity was changed small under 0.8Qopt (Qopt,operating condition).Under 0.4Qopt,however,the flow conditions at impeller inlet became complicated,therefore,the axial velocity was changed significantly.The angle of attack of the fluid on the blades was increased and affected by tip leakage flow.The flow separation was generated at the leading edge of suction surface at t* =0.041 6,when the impeller was rotated from t* =0.041 6 to t* =0.124 9,the flow separation was intensified and the swirling strength of the separation vortex was gradually increased,so the static pressure of the leading edge of suction surface was decreased,the adverse pressure gradient was increased which promoted the generation of backflow.When the backflow reached the leading edge,the static pressure of leading edge was gradually restored,therefore the flow separation was an important reason that making the multiples of pressure fluctuation increased.%基于标准的Smagorinsky亚格子尺度模型,对斜流泵全流场进行大涡模拟并结合压力脉动实验对小流量工况下的压力脉动和内部流场进行研究.实验结果表明,叶轮进口处的脉动幅值最高,随着流量的降低压力脉动幅值逐渐增加,不同工况下叶轮进口、叶轮出口、导叶进口的压力脉动主频为叶频,但导叶出口脉动主频随着流量的变化而变化.大涡模拟表明,0.SQopt工况下叶轮进口流动状态较好,叶轮进口轴面速度变化较小,而在0.4Qopt工况下叶轮进口流动状态较复杂,轴面速度变化较大,0.4Qo.工况时叶轮进口冲角增加以及受到相邻叶片叶顶泄漏流的影响,在t* =0.0416时叶片进口吸力面已发生流动分离,当叶轮从t*=0.041 6旋转到t*=0.124 9时,叶片吸力面流动分离加剧,轮缘处的轴面速度明显升高,同时分离涡的旋转强度也逐渐增强,导致该区域的静压下降,逆压梯度上升,促使回流的产生,当回流到达叶片进口时进口处的静压逐渐恢复,因此叶轮进口流动分离是引起叶轮进口压力脉动幅值增加的重要因素.