口环间隙变化对离心泵性能影响的数值模拟研究
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摘要
随着计算机科学及流体力学理论的发展，CFD技术已经广泛应于用离心泵性能预测与内部流动研究。但目前在进行离心泵性能预测时，往往采用简化的模型，忽略了口环间隙及泵腔对离心泵性能的影响，这样就造成了预测结果的误差。实际上，水泵中的泄漏是不可避免的，而且口环间隙作为一种非接触式密封形式，可以保持较小的泄漏损失，对研究离心泵的容积损失及内部流动结构有着十分重要的意义。
本文以一台单级单吸悬臂离心油泵为主要模型，该原型泵包含平衡孔。首先利用CFD技术对整体流道模型和简化模型进行三维流场数值模拟，预测了两种模型的的性能曲线，并与试验曲线进行对比，验证离心泵整体模型的数值模拟计算与试验数据更为贴近，为后期研究口环间隙中流动对离心泵性能的影响奠定基础。之后本文基于CFD的数值模拟方法，通过建立不同口环间隙的离心泵实体模型对性能进行详尽的分析，对比前、后口环间隙大小的变化对离心泵外特性及内部流动情况的影响。通过数值模拟结果的分析，初步探讨了口环间隙变化后，泵腔内液体流动的情况；文中还通过对比不同口环间隙的泄漏量随流量的变化，分析口环间隙改变后口环间隙进出口压差、泄漏量、流量变化的关系；以及分析叶轮盖板的压力变化情况，并计算不同口环间隙的离心泵的轴向力及径向力。在进行了上述研究后，得到以下结论：
1）整体模型的数值模拟预测的离心泵性能曲线与试验曲线趋势相近，简化模型对比试验曲线的误差较大，证明整体模型数值模拟结果的可靠性。同时对整体模型内部流动进行分析，发现原型泵水力设计存在一定问题。
2）对加大口环间隙的模型进行数值模拟后，所得的设计工况参数均发生变化，且水泵的性能明显差于原型泵。
3）口环间隙值的改变，影响泵腔内液体的压力及速度分布。
4）口环间隙内泄漏量的改变与间隙值的大小有直接关系，且泄漏量的大小影响了轴向力的变化，但对径向力影响不大。
因此，离心泵在进行建模及数值计算时须考虑口环间隙，口环间隙中的流动非常复杂且影响离心泵的性能及内部流动情况。本文研究结果为口环间隙大小的合理设计及离心泵性能预测提供参考，且为改善和提高离心泵性能奠定了基础。
Recently, computational fluid dynamics(CFD) has been used extensively inpredicting centrifugal pump performance and the internal flows of pumps along withthe development of the computer science and fluid mechanics theory. But at present,people often use simplified model to predict pump performance, ignored the effect ofliquid flow in the clearance of wear-rings and in the pump chamber. And it will bringsome errors of the result. In fact, the leakage of the centrifugal pump is inevitable. Asa non-contact sealing form, wear-rings of impeller can not olny keep the less leakage,but also play a part in the research of the capacity lose and the internal fluid structureof the pump.
The paper chooses the single-stage, single-suction, cantilevered and centrifugalpump with balance holes as the main model. Firstly, CFD technology is used forthree-dimensional flow field numerical simulation of whole flow model and thesimplified model. We studied the influence of the model including wear-rings ofimpeller and liquid flow in the pump cavity on the result of the flow field simulationand predicted the performance curve of these two kinds of models. Then the curveswere compared with the experiment curves, and we found that the data of the wholemodel of centrifugal pump numerical simulation is closer to the experiment data. Itwill lay a foundation for further research on the influence of the flow in the clearanceof wear-rings on the performance of the centrifugal pump. Then, based on the CFDnumerical simulation method, the pump function will be analyzed in details throughestablishing different models of different size of clearance of wear-rings, and theeffect of size change of the clearance of wear-rings on the outside characteristics andthe internal flow will be contrasted. By the analysis of numerical simulation data, wedicussed the liquid flow status in the pump chamber after the change of clearance ofwear-rings; the paper contrasted the change of the leakage of different clearance ofwear-rings along with the change of flux and also we analyzed the relations ofpressure difference of into and out the clearance of wear-rings, leakage and flow ratechange after size change of clearance of wear-rings; Analyzed pressure changes offront and back cover board of impeller, and calculated axial and radial force withdifferent clearance of wear-rings. In the study, conclusions are as follow:1) the performance curve of the numerical simulation of the whole model predictionof the centrifugal pump matches well with the experiment curve, but the simplified model is poored matched. This indicated that the whole model is more reliable. At thesame time based on the analysis of the flow in the whole model, we found theprototype pump hydraulic design has some problems.2) the numerical simulation wich extends the clearance of the wear-rings, we foundthe design parameters of the conditions are all changed, and the performance of thepump is obviously poorer than prototype pump.3) the change of clearance of wear-rings affects liquid pressure and velocitydistribution in pump chamber.4) the leakage in the clearance of wear-rings is directly related with the size of theclearance of wear-rings and the leakage will affect the axial force but there is lessimpact to radial force.
we need consider the clearance of wear-rings in moleding and numericalcaculation of centrifugal pump and the flow in the clearance of wear-rings is verycomplex. It will affect the performance of the centrifugal pump and the internal flow.The results in this paper can offer a reference for future reasonable design of theclearance of wear-rings and centrifugal pump performance prediction, and it can alsooffer a foundation to the improvement and enhancement of the centrifugal pumpperformance.
本文以一台单级单吸悬臂离心油泵为主要模型，该原型泵包含平衡孔。首先利用CFD技术对整体流道模型和简化模型进行三维流场数值模拟，预测了两种模型的的性能曲线，并与试验曲线进行对比，验证离心泵整体模型的数值模拟计算与试验数据更为贴近，为后期研究口环间隙中流动对离心泵性能的影响奠定基础。之后本文基于CFD的数值模拟方法，通过建立不同口环间隙的离心泵实体模型对性能进行详尽的分析，对比前、后口环间隙大小的变化对离心泵外特性及内部流动情况的影响。通过数值模拟结果的分析，初步探讨了口环间隙变化后，泵腔内液体流动的情况；文中还通过对比不同口环间隙的泄漏量随流量的变化，分析口环间隙改变后口环间隙进出口压差、泄漏量、流量变化的关系；以及分析叶轮盖板的压力变化情况，并计算不同口环间隙的离心泵的轴向力及径向力。在进行了上述研究后，得到以下结论：
1）整体模型的数值模拟预测的离心泵性能曲线与试验曲线趋势相近，简化模型对比试验曲线的误差较大，证明整体模型数值模拟结果的可靠性。同时对整体模型内部流动进行分析，发现原型泵水力设计存在一定问题。
2）对加大口环间隙的模型进行数值模拟后，所得的设计工况参数均发生变化，且水泵的性能明显差于原型泵。
3）口环间隙值的改变，影响泵腔内液体的压力及速度分布。
4）口环间隙内泄漏量的改变与间隙值的大小有直接关系，且泄漏量的大小影响了轴向力的变化，但对径向力影响不大。
因此，离心泵在进行建模及数值计算时须考虑口环间隙，口环间隙中的流动非常复杂且影响离心泵的性能及内部流动情况。本文研究结果为口环间隙大小的合理设计及离心泵性能预测提供参考，且为改善和提高离心泵性能奠定了基础。
Recently, computational fluid dynamics(CFD) has been used extensively inpredicting centrifugal pump performance and the internal flows of pumps along withthe development of the computer science and fluid mechanics theory. But at present,people often use simplified model to predict pump performance, ignored the effect ofliquid flow in the clearance of wear-rings and in the pump chamber. And it will bringsome errors of the result. In fact, the leakage of the centrifugal pump is inevitable. Asa non-contact sealing form, wear-rings of impeller can not olny keep the less leakage,but also play a part in the research of the capacity lose and the internal fluid structureof the pump.
The paper chooses the single-stage, single-suction, cantilevered and centrifugalpump with balance holes as the main model. Firstly, CFD technology is used forthree-dimensional flow field numerical simulation of whole flow model and thesimplified model. We studied the influence of the model including wear-rings ofimpeller and liquid flow in the pump cavity on the result of the flow field simulationand predicted the performance curve of these two kinds of models. Then the curveswere compared with the experiment curves, and we found that the data of the wholemodel of centrifugal pump numerical simulation is closer to the experiment data. Itwill lay a foundation for further research on the influence of the flow in the clearanceof wear-rings on the performance of the centrifugal pump. Then, based on the CFDnumerical simulation method, the pump function will be analyzed in details throughestablishing different models of different size of clearance of wear-rings, and theeffect of size change of the clearance of wear-rings on the outside characteristics andthe internal flow will be contrasted. By the analysis of numerical simulation data, wedicussed the liquid flow status in the pump chamber after the change of clearance ofwear-rings; the paper contrasted the change of the leakage of different clearance ofwear-rings along with the change of flux and also we analyzed the relations ofpressure difference of into and out the clearance of wear-rings, leakage and flow ratechange after size change of clearance of wear-rings; Analyzed pressure changes offront and back cover board of impeller, and calculated axial and radial force withdifferent clearance of wear-rings. In the study, conclusions are as follow:1) the performance curve of the numerical simulation of the whole model predictionof the centrifugal pump matches well with the experiment curve, but the simplified model is poored matched. This indicated that the whole model is more reliable. At thesame time based on the analysis of the flow in the whole model, we found theprototype pump hydraulic design has some problems.2) the numerical simulation wich extends the clearance of the wear-rings, we foundthe design parameters of the conditions are all changed, and the performance of thepump is obviously poorer than prototype pump.3) the change of clearance of wear-rings affects liquid pressure and velocitydistribution in pump chamber.4) the leakage in the clearance of wear-rings is directly related with the size of theclearance of wear-rings and the leakage will affect the axial force but there is lessimpact to radial force.
we need consider the clearance of wear-rings in moleding and numericalcaculation of centrifugal pump and the flow in the clearance of wear-rings is verycomplex. It will affect the performance of the centrifugal pump and the internal flow.The results in this paper can offer a reference for future reasonable design of theclearance of wear-rings and centrifugal pump performance prediction, and it can alsooffer a foundation to the improvement and enhancement of the centrifugal pumpperformance.
引文
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[2] Dale E. Van Zante，Anthony J. Strazisar，Jerry R. Wood etc. Recommendationsfor Achieving Accurate Numerical Simulation of Tip Clearance Flows inTransonic Compressor Rotors. Journal of Turbo machinery,2000,122:733-742.
[3] Behnam H. Beheshti, Joao A. Teixeira and Paul C. Ivey etc. Parametric Study ofTip Clearance—Casing Treatment on Performance and Stability of a TransonicAxial Compressor. Transactions of the ASME,2004,126:527-535.
[4] Anil Prasad, Joel H. Wagner. Unsteady Effects in Turbine Tip Clearance Flows.Transactions of the ASME,2000,122:621-627.
[5]姜桐,吴克启.叶轮机械内部流动实验分析方法[M].北京,机械工业出版社,1989
[6]李诗久.工程流体力学[M].北京,机械工业出版社，1990
[7]王洋，张祥.叶轮口环间隙对低比转速离心泵效率的影响[J].排灌机械，2007,26(6)：27-30
[8] K.塔鲁达纳夫斯基.非接触密封[M].李均卿,刁元康,译.北京:机械工业出版社,1986.(TRUTNOVSKY K. Motionless Seals [M].Beijing: MechanicalIndustryPress,1986.(in Chinese)).
[9] A.A Lomakin. Calculation of Critical Speed and Securing of Dynamic Stabilityof Hydraulic High-Pressure Pumps with Reference to the Forces Arising in theGap Seals. Energomashinostroenie,1962,14(1):1158~11701.
[10]赵万勇.多级泵平衡盘间隙流动的理论分析[J].水泵技术，2001(1):21-23.
[11] A.H.TPKNH.Знергомашиностроение[M].1978.
[12]徐林.湍流工况下泵的环状间隙密封内流场分析及泄漏量计算[J].水泵技术,2002,2:17-20.
[13] KurokawaJ.MatsmotoK，Matusi J and Imamura H.Pedbrmance Improvement andPeculiar Behavior of Disk Friction and Leakage in Very Low Specific-speeds，Purms Proeeedings of20th IAHR Symposium on Hymposiu on HydraulicMachinery，and Systems，Char10ttle，USA，2000，August
[14]李文广,费振桃,蔡永雄.离心油泵叶轮口环间隙对性能的影响[J].水泵技术,2004(5)：7-13.
[15]陈鱼，费振桃，蔡永雄等.输送清水时口环间隙对离心油泵性能的影响[J].流体机械，2006,34(1):1-5.
[16]刘在伦，魏烈江，齐学义，陈云富.新型轴向力平衡装置间隙泄漏量的计算[J].农业机械学报，2005(12):74-76.
[17]费振桃，蔡永雄，李文广.泄漏量对圆盘摩擦损失的数值计算[J].水泵技术，2004(2):8-12.
[18]吴大转，许斌杰，武鹏，李志锋，王乐勤.多级离心泵内部间隙流动与泄漏损失[J].浙江大学学报，2011，45:1-6.
[19]吴钢，张克危，戴勇峰.转轮间隙及密封结构对混流式水电机组安全运行的影响[J].大电机技术，2005，1:44-52.
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