空化现象一直以来是离心泵面临的一个难题，空化会使泵的性能下降、腐蚀破坏过流部件、产生振动和噪声等，严重时泵将不能运行[1]。 因此有必要对离心泵汽蚀时的汽-液两相流进行深入研究。

Cavitation has always been a difficult problem for centrifugal pumps. Cavitation can reduce the performance of the pump, destroy the overcurrent components, produce vibration and noise, and the pump will not run [1] when it is serious. Therefore, it is necessary to further study the vapor-liquid two-phase flow during centrifugal pump cavitation.

基于经验的传统叶轮设计需要繁琐的模型试验，大大增加了设计成本和设计周期，制约了离心泵高空化性能优化设计的进一步发展[2] 。随着计算流体动力学( CFD) 技术在水力机械内部流场计算中应用日益广泛，CFD成为优化设计的重要工具。长期以来，国内外学者采用数值模拟的方法对水泵内部空化流动进行了很多研究[5,6]，并成功预测了空化临界点[7,8,9]和离心泵叶轮内发生的多区域空化流动现象等[10,11]。如Medvitz等[12]捕捉到了离心泵在偏流量工况的能量和扬程下降特性，Coutier Delgosha等[13]采用正压状态方程对3台离心泵进行定常空化流动计算，成功获取了泵的扬程下降曲线及空泡结构。

The traditional design of the traditional impeller based on experience needs tedious model test, which greatly increases the design cost and design cycle, which restricts the further development of the optimization design of the high altitude performance of the centrifugal pump [2]. As computational fluid dynamics (CFD) technology is applied more and more widely in the computation of internal flow field of hydraulic machinery, CFD has become an important tool for optimization design. For a long time, many domestic and foreign scholars have studied the cavitation flow inside the pump by numerical simulation methods, and have successfully predicted the [10,11] of the cavitation critical point [7,8,9] and the multi area cavitation flow phenomenon in the impeller of the centrifugal pump. [12], such as Medvitz and so on, captured the energy and head drop characteristic of the centrifugal pump in the partial flow condition, and the [13] of Coutier Delgosha and so on uses the positive pressure state equation to calculate the constant cavitation flow of the 3 centrifugal pumps, and successfully obtained the head drop curve and the vacuole structure of the pump.

不难看出，上述离心泵的空化研究较多集中于对外特性的预测，目前对叶轮空化性能优化改进的相关工作虽然也做了不少，但仍有待于深入研究。本文应用汽液两相流混合模型基本方程，对一台比转速为100的双吸泵叶轮内部空化性能进行数值计算和分析，并通过修改叶轮入口直径、前盖板圆弧半径及叶片进口边形状来提升叶轮空化性能，旨在给出离心泵空化流计算中叶轮改进的合理建议。

It is not difficult to see that the cavitation research of the centrifugal pump is mostly focused on the prediction of external characteristics. Although many related work on the optimization of the cavitation performance of the impeller has been done, it still needs to be studied in depth. In this paper, the cavitation performance of a double suction pump impeller with a specific speed of 100 is numerically calculated and analyzed by using the basic equations of the mixture model of the steam and liquid two phase flow. The cavitation performance of the impeller is improved by modifying the inlet diameter of the impeller, the arc radius of the front cover plate and the shape of the inlet edge of the blade. The purpose of this paper is to give a reasonable suggestion for the improvement of the impeller in the calculation of the cavitation flow of the centrifugal pump.

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基本参数及网格划分

Basic parameters and grid partition

本文计算模型为一台双吸泵，流量 QO=7000m3/h，扬程H=55m，叶片数Z=6，转速n =740rpm。计算域由吸水室、叶轮及压水室组成。划分网格时采用非结构化四面体网格，并在叶片头部及尾部，压水室隔舌处进行加密，计算域见图1。进行网格无关性检查时，当扬程的相对误差低于0.5%便可认为网格对计算结果无影响，最后确定计算所采用的网格总数为240万。

The calculation model is a double suction pump. The flow rate is QO=7000m3/h, the lift is H=55m, the number of blades is Z=6, and the speed is n =740rpm. The calculation domain consists of water absorption chamber, impeller and water pressure chamber. The unstructured tetrahedral mesh is used to divide the grid, and it is encrypted at the tongue end of the blade head and tail, and the computational domain is shown in Figure 1. When the relative error of the lift is less than 0.5%, it is considered that the grid has no effect on the results of the calculation, and the total number of grids used in the calculation is 2 million 400 thousand.