Experimental Research And Simulation On Balancing Axial Force With Cutting Amount Of Back Cover Plate Of Centrifugal Pump Impeller

As a new method of balancing axial force,cutting the back cover plate of impeller has the advantages of convenient processing and cost saving.However,after cutting the back cover plate of impeller,the changes of pump performance,pump cavity pressure,leakage and other parameters have not been explained in detail in the thesis.In this thesis,the writer take IS80-50-315 centrifugal pump as the research object,and designs 15 kinds of test plans.Each test scheme adopts the research method of combination of test and numerical simulation.The influence of the cutting amount of the back cover plate of the impeller on the performance of the centrifugal pump,the pressure of the pump cavity,the leakage amount and the axial force was studied.（1）After analyzing the test data,it is found that the performance curve of the pump decreases with the increase of the cutting amount of the rear cover plate of the impeller,and the change of the head can be traced.Based on the cutting law,the relationship formula between the diameter of the rear cover plate of the impeller and the head is proposed.When the index n is in the range of 0.85¹.11,the error between the calculated value and the test value is less than 5%.It is found that the influence of speed on pump performance meets the requirements of similarity law,and the maximum deviation is less than 6%.（2）The experimental study on the pressure of the pump cavity shows that the pressure distribution of the front and rear pump cavities is different along the radial direction before and after the cutting of the rear cover plate of the impeller.With the increase of the cutting amount of the rear cover plate of the impeller,the pressure of the front and rear pump cavities decreases continuously.Compared with the pressure of the front pump cavity,the cutting of the rear cover plate of the impeller has a greater impact on the pressure of the rear pump cavity.It shows that cutting the back cover plate of impeller can reduce the cover plate force of liquid acting on the impeller in the area above the impeller seal.（3）After cutting the rear cover plate of the impeller,the correction coefficient of liquid angular velocity in the rear pump cavity is the range value changing with the cutting amount of the rear cover plate of the impeller.According to the test data and relevant calculation formula,the value range of correction coefficient k₁ of liquid angular velocity in the cutting area is 0.93⁰.97,and the value range of correction coefficient k₂ of liquid angular velocity in the uncut area is 0.42⁰.46.After comparing the theoretical curve with the experimental curve,it is found that the maximum error is4.17%,which shows that the correction coefficient has high reliability.（4）When the rear cover plate of the impeller is not cut,the axial force direction points to the inlet direction of the impeller.When the cutting amount of the rear cover plate of the impellerΔD=30 mm,the axial force direction does not change,but the value is greatly reduced.When the cutting amount of the rear cover plate of the impellerΔD=40 mm,the axial force is close to zero.As the cutting amount continues to increase,the axial force starts to increase in reverse direction.It shows that cutting the rear cover plate of impeller can effectively reduce the axial force,but the cutting amount should not be too large.From the perspective of reducing the axial force,the cutting scale should be controlled at about 30 mm⁴0 mm.（5）On the basis of the test,the numerical simulation technology is used to simulate each test scheme.After comparing the test curve and simulation curve of pump head and efficiency,it is found that the test curve and simulation curve are in good agreement,which shows that the simulation results are reliable.According to the simulation results,the flow field in the rear pump cavity is analyzed.The results show that after the impeller rear cover plate is cut,the vortex is formed in the rear pump cavity.The larger the cutting amount is,the larger the area and the number of vortices are.The existence of the vortex and the change of the impeller structure cause the decrease of the pump lift and efficiency.