The Test And Simulation Of Pressure Characteristics And Leakage Volume Of Impeller Back Blade Cavity Of Centrifugal Pump

The impeller back blade not only has the function of balancing the axial force,but also has the sealing effect,belongs to the "non-contact" dynamic seal,can effectively reduce the pressure difference at the shaft seal,reduce leakage or even achieve no leakage,widely used in conveying impurities centrifugal pump or slurry pump.Based on the existing closed test bed of centrifugal pump in the laboratory and the modified is80-50-315 centrifugal pump as the research object,the back blade models of impeller A,B,C and D were designed by laying the back blade on the back cover of the impeller.For each model,different axial clearances of the back blade were obtained by changing the axial length of the back blade of the impeller,and the experimental study was carried out.Combined with the numerical simulation method,the influence law of the back blade on the pump performance,the liquid pressure characteristics of the pump chamber and the leakage amount of the pump chamber was studied.(1)after the impeller is laid with the back blade,it has a significant impact on the overall performance of the pump.Compared with the impeller without back blade,the pump head and shaft power increase,and the efficiency decreases.When the back blade model is constant,the head and axial power of the centrifugal pump gradually decrease with the increase of the axial clearance of the back blade,and the efficiency of the pump gradually increases with the increase of the axial clearance.When the axial clearance increases from 3mm to 4.5mm,the efficiency is significantly improved.When the axial clearance of the back blade is constant,the head and shaft power of model B of the back blade are the largest and the efficiency is the lowest,while that of model C is the lowest and the efficiency is the highest,and the head,shaft power and efficiency of model D are between model B and model C.Model D: the combination impeller back blade with radial length of 100 mm and radial length of65 mm is the best back blade selection,and the efficiency decreases less when the pump head is improved.(2)through the experimental study,it is found that the impeller laid on the back blade has a significant impact on the liquid pressure in the rear pump cavity within the radius r=89mm-133 mm,forming a low pressure area,especially the liquid pressure near the hub is very small,and has a small impact on the liquid pressure at the edge of the rear pump cavity with the radial radius r=146mm-154 mm.When the back blade model is constant,with the increase of the axial clearance of the back blade,the range of the low pressure area near the hub gradually increases,and the overall pressure of the rear pump cavity gradually increases,while the liquid pressure at the edge of the rear pump cavity with a larger radial radius does not change significantly with the increase of the axial clearance.Back vane axial clearance must,back after the blade model B on the distribution of the liquid pressure of the pump housing more than the model C,D,specific differences in model B model C and D more influence on the wheel hub near the low pressure area,and there are along the axial direction,the same radial radius position of the liquid pressure does not change.(3)compared with the impeller without back blade,the laying of the impeller’s back blade effectively reduces the liquid pressure in the balance chamber.The liquid pressure in the balance chamber gradually increases with the increase of the axial clearance of the back blade.The smaller the axial clearance of the back blade is,the more significant the effect is on reducing the pressure in the balance chamber.The effect of impeller back blade model B on reducing the liquid pressure in the equilibrium chamber is better than that of model C and model D.(4)the test and simulation results show that the leakage amount of the rear pump cavity decreases gradually with the increase of the flow rate,and the liquid leakage of the rear pump cavity is effectively reduced after the impeller is laid with the back blade.Under the same flow rate,when the back blade model is constant,the leakage amount of the rear pump cavity gradually increases with the increase of axial clearance.When the axial clearance is constant,model B with an outer diameter length of 100 mm is most effective in reducing the leakage amount.