离心泵作透平多工况内流与能量转换特性

为揭示不同流量下离心泵作透平的能量转换特性,基于1台比转数为90的单级悬臂式离心泵,在透平工况下对其进行数值模拟,并结合试验验证了数值模拟的准确性.结果表明:叶轮是透平内水力损失的主要部件,叶轮内水力损失占比随流量的增大呈现出先减小后增大的变化趋势.设计工况(Q=80m³/h)下,蜗壳、叶轮、腔体的水力损失占比分别为33.0%,35.1%,22.3%.通过对内流场中的流线分布和叶片进口速度三角形进行分析,揭示了不同工况下透平内流特性与水力损失之间的关系.设计工况下叶轮内流动均匀,无明显旋涡存在,在小流量工况下叶轮进口端面存在回流现象,旋涡出现在大流量工况叶片的吸力面.最后,采用拟涡能系数从能量的角度分析了不同工况内部流动的损失情况,进一步揭示了透平的能量转换机理.研究结果可为离心泵作透平的高效设计及实际现场运行调控提供参考.

Research on inflow and energy conversion characteristics of centrifugal pump as turbine in different conditions

To reveal the energy conversion characteristic of the pump as turbine(PAT)under different discharges, a single-stage cantilever centrifugal pump with the specific speed of 90 under the turbine mode was studied. By applying the finite volume method(FVM)to simulate the performance of diffe-rent flow rates, the accuracy of numerical simulation was validated by experimental results. The results show that the impeller is the main component of hydraulic loss in PAT. With the discharge increasing, the proportion of hydraulic loss in the impeller shows the tendency of decreasing first and then increa-sing. Under the design operating condition(Q=80 m³/h), the proportion of hydraulic loss of volute, impeller and cavity is 33%, 35.1% and 22.3%, respectively. By analyzing the distributions of stream-lines and velocity triangle at the inlet of the blade under different conditions, the relation between the flow characteristic and the hydraulic loss was revealed. The flow in the impeller is uniform and without vortex. However, the poor flow characteristic can be observed with the discharge deviating from the design condition. The backflow occurs at the inlet of the impeller under the part-flow condition, and the vortex occurs at the suction side of the blade under the large-flow condition. Finally, to further research the mechanism of energy conversion, enstrophy coefficient was utilized to analyze the hydraulic loss from the aspect of energy. The research results could provide references for the efficient design and operating of PAT.