Performance Prediction Of Centrifugal Pumps Under Multiple Conditions Based On Hydraulic Loss Model

The head of centrifugal pump varies with flow rate and can work under different working conditions.There are also some special centrifugal pumps which not only meet the requirements of head-flow under design conditions,but also strictly meet the requirements of head-flow at several special operating points under non-design conditions.At present,the multi-working condition design of centrifugal pumps has become a research hotspot.It is very important to predict the performance of centrifugal pumps at multiple working conditions accurately for the multi-working condition design of centrifugal pumps.At present,there are many researchs on the performance prediction of centrifugal pumps at design working conditions,and the prediction results are more accurate.However,there are few studies on the performance prediction of centrifugal pumps at non-design working conditions,and the prediction accuracy needs to be improved.Therefore,the research on performance prediction of centrifugal pumps under multi-operating conditions has important theoretical significance and certain economic value.The main work and research results are as follows:1.The flow of centrifugal pump under different working conditions is analyzed.The loss in centrifugal pump is divided into mechanical loss,volume loss and hydraulic loss.The internal hydraulic loss of single stage single suction centrifugal pump can be divided into impeller internal hydraulic loss and volute internal hydraulic loss.The hydraulic loss in impeller can be divided into impact loss at blade inlet,friction loss in impeller and diffusion loss in impeller.Hydraulic loss in volute can be divided into impact loss at volute inlet,friction loss and diffusion loss in volute.Based on this,the loss model of centrifugal pump is established.2.In order to accurately calculate the impact loss of blade inlet under different working conditions,eight centrifugal pumps with different specific speeds were selected to calculate the impact angle and impact loss coefficient of the eight centrifugal pumps under different working conditions respectively.The functional relationship between the impact angle of impeller inlet and the impact loss coefficient was obtained by regression analysis method.Based on this,the impact loss of blade inlet under different working conditions could be calculated.3.In order to verify the feasibility of the hydraulic loss model,four centrifugal pumps with different specific speeds are taken as the research objects.The loss model of centrifugal pumps established in this paper is used to predict the head,efficiency and power of centrifugal pumps under different working conditions,and the results are compared and analyzed with the experimental results.The prediction results of the loss model of centrifugal pump established in this paper are basically consistent with the test results.The error between the predicted head and the test head is less than 5%in the range of 0.4Q_d~1.3Q_d.This shows that the hydraulic loss model established in this paper can accurately predict the head of centrifugal pump under different working conditions,but there are still some errors in the prediction of efficiency and power under low flow conditions.4.In order to compare the accuracy of the hydraulic loss model and CFD flow field analysis method in predicting the performance of centrifugal pumps under different working conditions,3D model was established,meshing and flow field calculation were carried out for four centrifugal pumps.The head,efficiency and power of centrifugal pump under different working conditions are predicted by CFD software,and the results of CFD,hydraulic loss model and test results are compared and analyzed.The results show that the both methods can accurately predict the performance of centrifugal pumps at design operating points,and the prediction error of loss model method is smaller for the performance prediction of centrifugal pumps at non-design operating points.