【作者】 张勇；

【导师】 王晓放；

【作者基本信息】 大连理工大学 ， 动力机械及工程， 2016， 硕士

【摘要】 叶轮口环间隙结构的存在与改变会对核主泵的水力性能产生较大影响,本文通过CFX软件对课题组自主设计的CAP1400核主泵水力部件进行整机数值模拟,获得核主泵的水力性能及其内部流场结构,并结合实验对比验证数值模拟的准确性。分析叶轮口环间隙尺寸变化对叶轮所受轴向力、整机内部压力脉动特性及叶片水力载荷分布的影响,进而研究核主泵内部的水动力特性。核主泵长周期运行过程中,由于高温环境产生的热变形、高速旋转产生的离心力和轴承磨损等综合因素的影响,使核主泵叶轮口环间隙的尺寸发生改变,从而导致其水力性能和水动力特性的变化。考虑在290℃C高温环境下叶轮口环间隙热变形及长周期轴承磨损的共同影响,分析口环间隙尺寸变化对核主泵水力性能和水动力特性的影响是目前的研究重点。本文首先分析无口环间隙的核主泵整机内部流动结构和水动力特性,其次通过不同口环间隙尺寸下整机水力部件的全流道数值计算,比对分析口环间隙变化对核主泵的水力性能及流场分布、叶轮所受轴向力和水动力特性的影响。研究发现, (1)考虑叶轮口环间隙会导致核主泵整机设计点效率降低1%,扬程降低1.7%,并且随口环间隙尺寸增大,整机效率及扬程逐渐减小,叶轮进口处涡量增大,二次流冲击造成的水力损失增加； (2)口环间隙的增大会使叶轮前腔的泄漏量逐渐增加,进而导致叶轮前盖板处轴向力减小5%左右,使得叶轮轴向力增大2.4%-4.5%,方向指向叶轮进口； (3)设计条件下口环间隙的存在及尺寸变化对导叶叶片水力载荷的整体分布影响不大,对叶轮叶片中部水力载荷影响最大在8%左右波动,同时,口环间隙的改变导致叶轮叶片前缘的静压载荷突增,产生压力突变,说明口环间隙的变化对核主泵的可靠性会产生一定影响。本文的研究主要为长周期运行下核主泵叶轮口环间隙尺寸变化对其性能、叶轮轴向力、压力脉动及叶片水力载荷分布的影响分析,为进一步研究口环间隙对核主泵内部水动力特性影响的机理打下基础。更多还原

【Abstract】 Because of its existence and variation, the clearance of wear-rings can make a great impact on the performance of a nuclear main pump. The internal flow of an independent designed CAP 1400 model pumpwas simulated through CFX. The performance of the pump and its internal flow field structure are obtained in this paper. The accuracy of the results was verified by compareing the numerical results with the test results. Then the influence of the variation of the wear-rings clearance dimensions on impeller was analyzed, includingi axial force,internal pressure fluctuaion characteristics and blade load distribution, in order to have further study on hydrodynamic characteristics of the model pump.During a long period operating, the clearance sizes will chang as a result of thigh operating temperature, centrifugal force caused by high rotating speed, bearing wear and so on. This will result in the changesof the performance and the hydrodynamic characteristics. In consideration of common effects on clearance for the above three reasons, the current research emphasized on analyzing the effects on the performance and the hydrodynamic characteristics of the model pump with different clearance sizes in various operating conditions.Firstly, the internal flow field structure and the hydrodynamic characteristics of the model pump without clearance of wear-rings are analysed. Then, the numerical simulation results of the whole flow field with different wear-ring clearance sizes were obtained through changing the clearance size, and the comparison could help to analyze the effects on the performance, flow field distribution of the model pump, and also on the axial force, hydraulic load of the impeller related to different clearance sizes. It was shown that the existence of the clearance reduced the efficiency of the pump by 1%, and reduced the hydraulic head by 1.7%. What’s more, as the size increased, the vorticity at impeller inlet also increased, which led to hydraulic losses caused by the increased secondary flow. The variation of the axial force of the impeller was mainly caused by the change of the pressure distribution on the shroud of the impeller. The leakage flow increased as the size of the clearance added, which further reduced the axial force on the shroud of impeller by about 5%, resulting in the increasmnet of the axial force o by 2.4%-4.5%. At the nominal condition, the clearance did not have much influence on the load distribution of the impeller, and the variation of the hydraulic load at the middle part of the blades was no more than 8%. Furthermore, the hydrostatic loads would increase rapidly at the leading edge of the impeller blade due to the variation of the clearance size, which meant that the variation of the wear-rings clearance size of could have an effect on the reliability of nuclear main pump.The research of the paper mainly focuses on the influences of the variation of the wear-ring clearance size on the performance and the load distribution on the blades under operating conditions. It will lay the foundation for the further study on the mechanism of the effects the clearance of wear-rings have on the hydrodynamic characteristics of the nuclear main pump.更多还原