Effects of the Relative Position of a Centrifugal Impeller Blade Against the Tongue on the Steadily Simulated Pump Performance

The performance of a single-stage centrifugal pump with designed flow rate of 0.028m(3)/s, head of 20m and rotating speed of 1450rpm have been steadily simulated for four geometric models, in which the angle between the impeller blade and the tongue is 44 degrees, 29 degrees, 15 degrees and 0 degrees (where the blade meets the tongue) separately. The comparison of the simulated results to the experimental data show that the computed head and power are lower than that of the experiment, but the efficiency is up to 12.0% higher than the test result. The steadily simulated characteristics of the pump in four cases change with the blade relative location against the tongue. At the small flow rate of 0.6Qd (Qd is the designed flow rate), the pump head fluctuation Delta H is nearly 2.14m, pump efficiency fluctuation Ark reaches 3.06%, and the impeller efficiency variation Delta eta i reaches up to 8.0%. At the high flow rate of 1.4Qd, Delta H equals 1.45m, Delta eta is approximately 6.68%,Delta eta i is 1.03%. Under the design condition, the pump performance in four cases are almost the same show that the angle between the impeller blade and the tongue has neglectable effect. At last, unsteady simulation of the pump performance has been carried out and compared to experimental result. It indicates that the unsteady simulation is in agreement with the experiments. As a result, careful consideration should be taken while optimizing the pump performance by a method of steady simulation.