导叶式混流泵内部非定常流动特性数值模拟

Numerical Simulation of Unsteady Flow Characteristics in Mixed-flow Pump with Guide Vanes

为了研究不同流量工况对导叶式混流泵内部非定常流动特性的影响,基于ANSYS CFX软件并采用标准k-ε两方程模型对混流泵的外特性进行了数值预测,分析了流量工况对混流泵内压力分布、流线分布和湍动能的影响,探讨了不同流量工况下不同监测点的压力脉动时域和频域响应。研究结果表明,数值计算的外特性结果与试验测量结果趋势基本一致,最优工况点数值预测与试验测量的扬程和效率误差分别为3.29%和0.27%,数值计算的准确度较高。小流量工况下,叶片工作面与背面之间存在着较大的压力梯度,形成的轮缘泄漏流对主流产生较大干扰,同时受到动静干涉的影响,在叶轮出口和导叶流道内造成较大的能量损失和湍动能耗散;随着流量增加,轮缘泄漏流逐渐减少,动静干涉效应相对减弱,流场流动趋于平稳。不同流量工况下,各监测点压力脉动呈明显的周期性变化,一个旋转周期内压力脉动曲线有4个波峰和4个波谷,叶片通过频率始终占主导作用;流量对叶轮进口处和导叶中间处的压力脉动影响最明显,小流量工况下压力脉动系数的幅值变化最大;随着流量的增大,压力脉动频域幅值随之减小。本研究可为扩大混流泵的运行范围以及混流泵叶轮和导叶的优化设计提供参考依据。

In order to study the internal unsteady flow characteristics in the mixed-flow pump caused by flow rate conditions,the external characteristic of mixed-flow pump was predicted based on the standard k-ε two-equation model by using ANSYS CFX software. The influences of flow rate on internal pressure distribution,streamlines and turbulence kinetic energy distribution were further analyzed. The time domain and frequency domain responses at different monitor positions under various flow rate conditions were compared with each other. The results showed that the trend of external characteristic curve of mixed-flow pump acquired by numerical simulation or experiment test was basically the same,the deviations of head and efficiency compared with numerical prediction and experimental measurement were3. 29% and 0. 27%,respectively,which indicated that the numerical calculation was equipped with high accuracy. When it was operated under part loading conditions,the high pressure gradient between blade pressure surface and blade suction surface could lead to blade tip leakage flow,which had a great impact on mainstream in the impeller. Meanwhile,affected by the rotor-stator interaction,more energy loss and higher turbulent kinetic energy dissipation were appeared in the impeller outlet and flow passages of guidevanes. With the increase of flow rate,the tip leakage flow was decreased gradually,the rotor-stator interaction became weaker and the flow field in the impeller tended to be steady. Under different flow rate conditions,the pressure fluctuations at different monitoring positions had obvious periodic property,the time domain curve of pressure fluctuation contained four peak values and four valley values within a spin cycle of the impeller,and also the blade passing frequency always played the dominant role. Moreover,the influence of flow rate condition on impeller inlet and guide vane middle section was the most obvious and the amplitude value of pressure pulsation coefficient under part loading condition was the most dramatically changed. With the increase of flow rate,the amplitude value of pressure fluctuation in the frequency domain was decreased. This research provided a reference for expanding the operation range of mixed-flow pump and optimization design of impeller and guide vanes in mixed-flow pump.