影响离心泵效率的方面

　　离心泵作为一种通用的流体机械，在工业生产和日常生活中被广泛的应用。离心泵效率的提高会减少社会对能源需求的压力。通过利用CFD对离心泵进行数值模拟，预测离心泵性能、考察离其内部流场，并提出了一种离心泵叶轮的切削方法，在满足使用需要的同时，降低离心泵的扬程，扩大离心泵的使用范围，提高离心泵的效率，从而达到节约能源的目的。具体工作从以下几方面展开：

　　论述了课题的意义及研究背景，介绍了离心泵的种类结构以及离心泵的应用，列举了目前常用离心泵研究方法及优化方法，同时概括了本文主要的研究内容。

　　网格的一些基本概念，网格生成软件Gridgen和PLOT3D格式文件。重点阐述了离心泵全流道六面体结构网格的生成方法。针对离心泵的不同部件，综合运用Gridgen与Fortran相结合的办法，完成了离心泵包括叶轮、蜗壳以及前后盖板以外的密封部分六的面体结构网格划分。

　　CFD过程，包括前处理，求解和后处理。叙述了目前常用的湍流计算模型。本文提出选取SST湍流模型，结合k模型和k模型的优点来对离心泵进行数值模拟，并比对了模拟结果。接着FLUENT和Ansys CFX在离心泵模拟中的应用。最后对不同的水模进行了横向对比。

　　对现有典型离心泵进行内流分析，考察了离心泵的速度场和压力场的分布情况。然后对不同条件下对离心泵进行数值模拟并分析结果，包括考虑到泄漏回流条件和不同入口条件下对离心泵数值模拟结果的影响。

　　阐述了现阶段叶轮切割的一般方法，提出了一种只切削叶片，不切削前后盖板的切削方法，可以降低离心泵扬程。在满足用户需要的同时，提高离心泵的效率。利用CFD方法分析不同切削量下，离心泵的性能和内流场的分布情况，对改善离心泵性能具有很大的现实意义。

　　最后对本文所做的工作进行了总结，指出本文的创新点和不足之处，同时对这些不足之处的解决方法进行了思考。

　　英文翻译：As a kind of general fluid machinery, centrifugal pump is widely used in daily life and industrial production. It can reduce the pressure of energy demand when the efficiency of centrifugal pumps increase. In this thesis, several centrifugal pumps were studied to predict the performances and distributions of the internal flow field by using CFD method. In order to meet the practical needs, for example, to reduce the head of centrifugal pumps, a kind of centrifugal pump impeller cutting method was used in industrial practice. It can achieve the purpose of matching the specific application needs without changing a new pump. Several cut impellers were studied in this paper. The whole thesis consists of 6 chapters as follows:

　　The background and significance of the research is presented. The different kinds of centrifugal pumps and the application of them are introduced. The common methods of study and optimization are also discussed in this part. Then the main research contents are summarized.

　　The basic conception of grid is illustrated, including the software of grid generation named Gridgen and a file format named PLOT3D. The most important thing is the method of structure grid generation in a centrifugal pump. According to the different parts of the centrifugal pump, all the structure grids are accomplished including impeller part, volute part and the leakage part of the centrifugal pump by using a method of combining Gridgen with Fortran.

　　The process of CFD is introduced firstly. That is pre-processing, solver and post-processing. Then some commonly used turbulence models are introduced. SST and k turbulence model simulation results are compared, including the different commercial softwares of FLUENT and Ansys CFX. The last, the performances of different centrifugal pumps are studied.

　　The typical centrifugal pump is studied, including the distribution situations of velocity fields and pressure fields. And then, the numerical simulation results are analyzed in different conditions which include considering the leakage and different inlets.

　　A common method of cutting centrifugal pump impeller is introduced firstly. And then a kind of centrifugal pump impeller cutting method was put forward. That is the blades are cut only and ignored the impeller cover plates to reduce the head and increase the efficiency of centrifugal pumps based CFD numerical simulation. This method has a great practical significance to improve the performance of centrifugal pumps.

　　The thesis is summarized and the conclusion remarks are presented.