不同口环间隙离心泵性能及水力激励特性分析及试验

Analysis and test of performance and hydraulic excitation characteristics of centrifugal pump with different seal ring clearances

为进一步研究改变口环间隙所产生的影响,该文通过改变口环间隙大小,采用数值计算与试验相结合的方法,研究了离心泵内叶轮所受径向力以及压力脉动的变化。分别采用0.25、0.5以及0.75 mm的口环间隙,进行数值计算和试验。通过对叶轮外表面的压力场求解和分析,得到不同口环间隙对叶轮所受径向力的影响,通过试验测得的各监测点的压力脉动数据进行分析。结果表明:模拟所得扬程与试验结果较为吻合。叶频所对应的压力脉动幅值在前腔进口处,口环间隙为0.5 mm的方案约为0.25 mm方案的3.1倍,在叶轮出口处约为1.3倍;口环一周的平均压力脉动在0.75 mm时最小,此时约为0.5 mm方案的0.81倍;叶轮进口及其上游的压力脉动以0.75 mm方案最小,约为其他2个方案的0.67倍,说明口环间隙为0.5 mm时离心泵前腔及进口处的压力脉动最大。叶轮所受径向力随着口环间隙的改变呈现非线性变化,小流量及设计工况时0.75 mm方案的径向力最小,设计工况时0.25 mm方案的径向力最小。通过研究不同口环间隙所诱导的压力脉动及径向力的变化,对离心泵的传统设计进行了一定的补充,并且对口环的设计提供了参考。

In order to obtain more information about the clearance flow in a centrifugal pump and provide further reference for the design of centrifugal pumps, this paper researched and analyzed the distribution of radial force and pressure fluctuation of the impeller in a centrifugal pump via using the methods of the numerical simulation and the verification of experiment. Numerical calculations and experiments were carried out with different seal ring clearances which were respectively 0.25, 0.5 and 0.75 mm. The special speed of model pump was 69. On the one hand, after numerical simulation the influence of different seal ring clearances on the impeller radial force was obtained by calculating and analyzing the pressure of outer surface of impeller. On the other hand, the pressure pulsation signals were obtained by experimental measuring at monitoring points that included 8 locations. Of those, 6 monitoring points were arranged at the seal ring and volute, and 2 monitoring points were arranged at the impeller inlet. According to the clearance size of model pump seal ring (0.25, 0.5 and 0.75 mm), there were 3 cases. The comparison of 2 head curves from the numerical calculation and the experiment showed they had good agreement. The influence of the seal ring clearance on the pressure pulsation of the model pump could be changed obviously with the changing of the condition and the location of the monitoring points. And there was an optimum size of the seal ring clearance with which the pressure pulsation amplitude under the design condition was the smallest. At the inlet of the front cavity, the pressure pulsation amplitude of the case of 0.25 mm was about 3.1 times that of the case of 0.5 mm, and about 1.3 times at the impeller outlet. When the seal ring clearance was 0.25 mm, the mean pressure pulsation amplitude of the wear-ring was the minimum. At this time the pressure pulsation amplitude of the case of 0.75 mm was about 1.24 times that of the case of 0.5 mm. At the impeller inlet and its upstream, the pressure pulsation amplitude of the case of 0.75 mm was about 0.67 times that of the case of 0.25 and 0.5 mm. The radial force of the impeller was changed by the changing of the seal ring clearance. With the increasing of the seal ring clearance, the leakage of the fluid flow increased, which not only changed the pressure fluctuation at the impeller inlet and outlet, but also induced the pressure fluctuation at the inlet of the front cavity. For the pressure fluctuation under the design condition, there was an optimum value of the seal ring clearance, with which the pressure fluctuation amplitude was the minimum. At the same time, the radial force of the impeller changed with the changing of the pressure along the outer surface of the impeller, and the total radial force changed nonlinearly. The traditional design of the centrifugal pump has been carried out by studying the pressure fluctuation and the radial force induced by different seal ring clearances. By studying the changing of pressure pulsation signals and radial forces, this paper provides the reference for the traditional design of centrifugal pumps.