口环间隙变化对离心泵性能影响的数值模拟研究

发布时间：2019-01-07 08:22

【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。
[Abstract]:With the development of computer science and hydrodynamics theory, CFD technology has been widely used in centrifugal pump performance prediction and internal flow research. But at present, the simplified model is used to predict the performance of centrifugal pump, and the influence of the clearance of the ring and the cavity of the pump on the performance of the centrifugal pump is ignored, which results in the error of the prediction result. In fact, the leakage in the pump is inevitable, and as a non-contact seal, the gap of the orifice ring can keep a small leakage loss, which is of great significance to the study of the volume loss and the internal flow structure of the centrifugal pump. In this paper, a single-stage single-suction cantilever centrifugal oil pump is used as the main model. The prototype pump contains a balance hole. Firstly, the 3-D flow field of the whole channel model and the simplified model are simulated by using CFD technology, and the performance curves of the two models are predicted and compared with the experimental curves. It is proved that the numerical simulation calculation of the whole model of centrifugal pump is closer to the experimental data, which lays a foundation for the later study of the effect of the flow in the clearance of the orifice ring on the performance of the centrifugal pump. Then, based on the numerical simulation method of CFD, the performance of centrifugal pump is analyzed in detail by establishing the solid model of centrifugal pump with different orifice clearance. Before the comparison, the influence of the size of the clearance on the external characteristics and internal flow of centrifugal pump is discussed. Through the analysis of the numerical simulation results, the flow of liquid in the pump cavity after the change of the gap between the orifice and the ring is discussed preliminarily. In this paper, the relationship among the pressure difference, leakage volume and flow rate of the inlet and outlet of the gap after the change of the gap is analyzed by comparing the leakage volume of the different ring gap with the flow rate. The pressure variation of impeller cover plate is analyzed and the axial and radial forces of centrifugal pump with different clearance are calculated. After the above research, the following conclusions are obtained: 1) the performance curve of centrifugal pump predicted by numerical simulation of the whole model is similar to that of the test curve, and the error between the simplified model and the test curve is large. The reliability of the numerical simulation results of the whole model is proved. At the same time, the internal flow of the whole model is analyzed, and it is found that there are some problems in the hydraulic design of the prototype pump. 2) after numerical simulation of the model, the design parameters of the pump are all changed, and the performance of the pump is obviously worse than that of the prototype pump. 3) the pressure and velocity distribution of the liquid in the pump cavity is affected by the change of the gap value. 4) the change of leakage amount in the gap is directly related to the value of the gap, and the magnitude of the leakage affects the change of axial force, but not the radial force. Therefore, the clearance of the orifice ring should be taken into account in the modeling and numerical calculation of the centrifugal pump. The flow in the clearance of the orifice ring is very complex and affects the performance and internal flow of the centrifugal pump. The results of this paper provide a reference for the reasonable design of the clearance between the orifice ring and the performance prediction of the centrifugal pump, and lay a foundation for improving and improving the performance of the centrifugal pump.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH311

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