Influences of staggered blades on hydrodynamic performance of three-channel volute centrifugal pump

Abstract: Vibration and noise usually happens during the centrifugal pump running because of the interference between impeller blades and tongue. There are three tongues in the volute of barrel pump primary impeller, it makes the interference between impeller and tongue stronger, leading more serious vibration and noise, even reducing the service life of equipment. Three dimensional unsteady numerical simulations with SST k-ω turbulence model is used in barrel pump primary impeller. In order to research the influences of blade stagger angle to reduce the barrel pump vibration and noise, enhance hydrodynamic performance and improve the equipment operation stability and service life. To ensure the accuracy of the calculation results, constant calculate is used in centrifugal pump original model in the first place, considering the grid independence and compare the different of calculated value and experimental value. Centrifugal pump external characteristic experiment according to GB/T 3216-2005. The results show that performance curves trend of them is consistently, maximum deviation is about 5%, head and efficiency curves within 3% deviation at most of the flow point, results of numerical simulation has good reliability in general. The impeller rotated for 6 cycles in the simulation and the total computation time is 0.243s. The simulation result of the last one period was used to analyze the pressure fluctuation in the pump. Pressure fluctuation of different monitor points analyzed by time-frequency domain data processing method. Pressure fluctuation at different volute cross-section of same impeller model and the influence of different stagger angle to pressure fluctuation and radial force was researched. The simulation results show that head of centrifugal pump most falls nearly 7% after using staggered blade impeller as the stagger angle increases. The efficiency of 30°stagger angle model is about 5% higher than 0°stagger angle model in low flow rate condition. The monitor point pressure and pressure fluctuation in three-channel volute is similar every 120°, most violent point is 30°after the tongue, follow the impeller rotation direction. As the stagger degree increases, pressure fluctuation of monitor point close tongue and follow the impeller rotation direction decline most in the volute, standard deviation of pressure decline more than 85%. The standard deviation of other monitor point pressure in the volute also decline more than 50%. The reason is fluid highest radial velocity average distribution along axial direction reduce about 20% at impeller outlet, flow instability cause by fluid impact tongue more less. Pressure fluctuation frequency is mainly affected by the blade passing frequency in the volute, it has the trend of shift to higher frequency as the blade stagger angle increase. Radial force on the impeller most reduce about 60% when stagger angle increase from 0 to 30°. Liquid will be more prone to flow in axial direction after blade staggered, leading the reduce of centrifugal pump head and efficiency but smooth the pressure inside the volute. From the discussion above, staggered blades is useful to improve pressure fluctuation situation in the volute, reduce radial force on the impeller but cause the loss of centrifugal pump head and efficiency.