Influences Of Key Parameters At Impeller Outlet On Hydrodynamic Characteristics Of Centrifugal Pump With Double Volute

The impeller outlet of double volute centrifugal pump is a direct influence area of dynamic and static interference.The change of its parameters not only affects the hydraulic performance of the pump,but also plays an important role in the magnitude of pressure pulsation.In order to improve the hydraulic performance of the centrifugal pump,reduce the low-frequency vibration induced by the fluid,and ensure the safety and stability of the centrifugal pump,this thesis takes the double volute centrifugal pump with a specific speed of 83 as the research object,and optimize the hydraulic performance of the centrifugal pump by changing the impeller diameter,the number of impeller blades,and the thickness.The influences of the change of impeller parameters on the pressure pulsation of the double volute centrifugal pump and the structure of the impeller outflow wake was also studied.The main research contents and conclusions of the paper are as follows:1.Influences of impeller-volute radial clearance on hydraulic performance and pressure pulsation characteristics of double volute centrifugal pumpThe diameter of the impeller is modified according to the cutting law of the impeller.The change of this parameter directly affects the radial clearance between the impeller and the volute（factors directly affecting the flow of impeller outlet）,so as to study its influence on the hydraulic performance of the double volute centrifugal pump and the pressure fluctuation characteristics of the internal flow field.First,comparing the changes of hydraulic performance under different impeller-volute radial clearances,the difference between the numerical calculation results and the experimental results under different flow rates,the results showed that the double volute centrifugal pump with impeller outer diameter D₂=230mm has the highest efficiency.Based on this analysis of pressure pulsation characteristics in a double volute centrifugal pump with different impeller-volute radial clearances,The main frequency of the pressure pulsation of the centrifugal pump is the blade passing frequency and its higher harmonic,and the amplitude of the pressure pulsation of the double volute centrifugal pump with D₂=230mm is the lowest;Affected by the jet-wake flow structure,the relative velocity on the flow structure at the impeller outlet of the blade appears to be divided into zones,and with the impeller rotates,the flow zone gradually disappears,and the flow produces a mixed superposition.2.Influences of the number of impeller blades on the hydraulic performance and pressure pulsation characteristics of double voluteOn the basis of the hydraulic performance required by the experiment,and the calculation results of the model pump above,adopting the principle of matching the number of blades and double volute tongues to change the number of blades（indirect factors affecting impeller outlet flow）.The effect of the change of the number of impeller blades on the hydraulic performance and pressure fluctuation characteristics of the internal flow field of the double volute centrifugal pump was studied.First,investigate the changes in hydraulic performance parameters of model pumps under different flow rates when the number of impeller blades changes,and the errors between the calculated results and the experimental results,the results showed that the double volute centrifugal pump with impeller blade number Z=6 is higher than the other two pumps;Based on this analysis of pressure pulsation characteristics in a double volute centrifugal pump with different numbers of impeller blades,similar to the analysis results under different impeller-volute radial clearance conditions,the main frequency of the pressure pulsation under this parameter condition is the blade passing frequency and its frequency multiplication,and the pressure pulsation amplitude of the double volute centrifugal pump with Z=6 is lower;Similar to the results of wake flow distribution under different impeller-volute radial clearance conditions,due to the influence of the jet-wake flow structure,the relative flow velocity at the blade exit tail section appears,and as the impeller rotates,the flow section gradually disappears,and the flow produces mixed superposition.3.Influences of blade thickness at outlet on hydraulic performance and pressure pulsation characteristics of double volute centrifugal pumpChanges in the diameter of the impeller and the number of impeller blades not only affect the hydraulic performance of the centrifugal pump,but also change the internal flow performance of the pump,among them,the pressure distribution in the dynamic and static interference area affects by the jet-wake flow structure of blade outlet,thereby affecting the pressure pulsation characteristics.On the basis,by changing the thickness of the inlet and outlet edges of the blade（secondary influence factors of impeller outlet flow）,the hydraulic performance of the double volute centrifugal pump and the pressure pulsation characteristics of the internal flow field under different blade thicknesses were studied.First,by comparing the hydraulic performance curves of double volute centrifugal pumps under different flow rates,the double volute centrifugal pump with T₂ thickness is the most efficient,and is 4.68%and 3.34%higher than T₁ and T₃ at nominal flow rate,respectively,the change of this parameter condition not only affects the change of hydraulic performance,but also affects the pressure pulsation distribution of the centrifugal pump.The pressure pulsation frequency domain distribution of double volute centrifugal pumps with different blade thicknesses at different monitoring points is compared.The model with T₂ thickness has the lowest pulsation amplitude,and the pulsation main frequency is the blade passing frequency.The pulsation amplitude of the measurement point is higher than that of the volute circular measurement point;The blade wake structure under the conditions of the impeller parameters is similar to the conclusions obtained by the previous two methods.During the operation of the T₂ centrifugal pump,the flow of blade outlet that periodically rotates with time shows a clear divisional flow,and the flow division gradually disappears with flow-time.