【作者】 王秀勇；

【导师】 王灿星；

【作者基本信息】 浙江大学 ， 流体力学， 2007， 硕士

【摘要】 近几年来，随着计算机硬件水平的不断提高，国际上CFD技术在流体机械的优化设计中得到了广泛的应用，在国内却还处于初级阶段，如何将CFD技术更有效地应用到产品分析和设计中去，还有待于进一步的分析研究。在前人工作的基础上，本文对CFD技术在离心泵的性能预测、能量损失和流场结构的分析等方面的应用进行了一些有益的尝试和探索，以数值模拟的方式详细地揭示了不同工况下离心泵的流动特征。本文首先对一些CFD基本理论进行了简要介绍，推导了旋转坐标系下用于离心泵内部流场计算的控制方程。其次在确定数值模拟方案时，对计算域的组成结构、网格的划分方案提出了自己的观点，即计算域应该由叶轮通道、蜗室、前腔、后腔和密封环间隙组成，而不是仅仅包含叶轮通道和蜗室；对计算域进行网格划分时，对于前后腔和密封环间隙采用结构化网格，蜗室以及叶轮通道采用非结构化网格；分别通过对不同的网格数量和湍流模型的计算结果与试验结果进行比较，确定了适合于所采用的离心泵模型的网格数量和湍流模型；本文同时对叶片与蜗舌不同相对位置时的流场进行了数值模拟，发现叶片与蜗舌相对位置的不同对计算结果也有一定的影响，并对计算结果与相对位置之间的关系进行了总结分析。在数值模拟方案确定了之后，通过对两种不同计算域的计算结果与试验值进行对比，证明本文关于计算域的组成结构的观点是正确的，并且在0～1.35Q_opt流量范围内，扬程、轴功率和效率等性能参数的预测曲线与试验曲线吻合情况良好。由于计算域已经比较完整，对离心泵中存在的圆盘摩擦损失、容积损失和水力损失也能够应用数值模拟的方法做出全面的预测。通过对传统的能量损失计算公式中存在的不足之处进行修正，对各过流部件中的能量损失进行了预测，表明叶轮和蜗壳中的水力损失是能量损失的主要方式，并揭示了各种能量损失随流量的变化规律。受蜗壳变截面面积的影响，各个叶轮通道中的流量和能量损失情况也不一样，其中在即将掠过蜗舌的几个叶轮通道中的水力损失最大，并且从最靠近蜗舌的叶轮通道中流出的液体是产生圆盘摩擦损失和泄漏损失的主体。通过数值模拟捕捉到了离心泵不同部位中存在的一些不利的流动现象，如二次流、冲击现象，以及某些工况下在叶轮和蜗室中存在的死水区，等等，并分析了总压、静压和速度等物理量在各个过流部件中的分布规律，为离心泵的进一步优化设计提供了重要的参考信息。更多还原

【Abstract】 In recent years, CFD technology has been widely used for theoptimum design of fluid machinery in developed country. In our country,the research and applications of CFD technology are still preliminary, andit needs a further development on the application of CFD technology todesign fluid machinery more efficiently. Based on the CFD technology, anumerical method is developed to predict performance, analyse energylosses and flow characteristics in a centrifugal pump, and the detailedflow field at different operating conditions is also revealed by thismethod.In the paper, some CFD theories are introduced firstly, and thecontrol equations in rotating reference frame used to the simulation of theflow field of a centrifugal pump are deduced. A new kind ofcomputational domain structure, that is, the front and back chambers andthe seal clearance should be involved in the computational domainbesides the impeller passages and volute casing, is developed innumerical simulation. The following grid-generation method is selected,the structured grid is used in front chamber, back chamber and sealclearance, the unstructured grid is used in the volute casing and thecomplicated impeller passages. Through the comprehensive comparisonsbetween simulating datum, in different grid number and turbulencemodels, and experimental datum, the suitable gird number and turbulencemodel are confirmed for the centrifugal pump model. The flow are also simulated at different relative positions between blade and volute tongue,it is found that the different relative positions between blade and volutetongue can influence the numerical simulation results, and the regularitiesbetween them are analyzed. Based on the method of numerical simulation,the simulating results show that the computational domain structure usedby the authors is better, through the comparison between the simulatingresults derived from two different kinds of computational domains and theexperimental results. Within the flow range from 0 to 1.35Q_opt, thecomputational performance curves such as head, shaft power andefficiency agree well with the tested curves. Due to the completecomputational domain, a full prediction can be made too, such as the diskfriction loss, volume loss and hydraulic loss existing in a centrifugalpump. The losses existing in each through-flow part are predicted bycorrecting the disadvantage of traditional method, the computationalresults shows that the losses in the impeller passage and volute casing arethe majority of the whole losses, and the energy losses regularitiesaccording with flow rate are revealed, too. Influenced by the varyingcross-section area of volute casing, the flowrates and energy losses ineach impeller passage are quite different, the losses in the passages nearthe volute tongue are much more than the others, and the liquids comingfrom the passages most near the volute tongue are the major componentsthat produce the disk friction loss and volume loss. By numericalsimulation, some adverse phenomena are found, such as jet-wakestructure, secondary flow, impact phenomenon, dead water zones, and soon. The distribution regularities of total pressure, static pressure andvelocity are also analyzed in each through-flow part. It provides importantguidance for the optimum design of a centrifugal pump.更多还原