Research On The Effect Of Centrifugal Pump Impeller Geometry On Fluid Excitation Noise

As an important and universal fluid transportation machine,centrifugal pumps are widely used in various industries and departments.The pump will inevitably produce noise and vibration when it is running,and currently reducing the noise of centrifugal pumps is an important research hotspot.In this paper,a centrifugal pump is used as the research object.Through the combination of experiment and numerical simulation,the RNG k-?model is used to simulate the unsteady flows of the centrifugal pump,and the dipole sound source is extracted according to the FW-H equation from the volute surface.Based on the acoustic boundary element method,the sound field calculation of the ce ntrifugal pump is performed,and the results of the acoustic calculation and the pressure pulsation of the flow field are comprehensively analyzed.And by exploring the influence of the structure of the impeller on the internal and external sound fields of the centrifugal pump,in order to find the optimal structural parameters.The main research contents and conclusions are as follows::1.Correlation analysis of turbulent pressure pulsation and internal sound field characteristics of centrifugal pump.Experiments and numerical simulation calculations of model pumps under different flow conditions show that the dynamic and static interference between the volute tongue and the impeller is the main reason for the dramatic change in the peak pressure pulsation in the volute.The pressure pulsation of the design flow and large flow conditions is highest at the tongue,followed by the volute exit.The pulsation peaks under different operating conditions are mainly concentrated in the blade passing frequency and its double frequency,with the peak value at the blade passing frequency being the highest.The pressure pulsation in the tongue separation area conditions is the lowest under the design operating conditions.The turbulent pressure pulsation has a certain correlation with the noise of the internal flow field,and the sound pressure level in the area with a large turbulent pressure pulsation peak is also large.The jet-wake causes a low pressure on the back of the blade exit.When the blade sweeps the tongue,the formed jet makes the blade exit region have a higher tangential velocity and a lower radial velocity.The sound field distribution in the volute exhibits dipole characteristics,and the sound pressure level gradient near the tongue is large.The tongue is the main noise source.At different characteristic frequencies,the sound pressure level at the leaf frequency is the highest,and the sound pressure level at the exit section is greater than that at the inlet.The flow is the main factor affecting the noise of the internal sound field,and the maximum sound pressure level in the design conditions is the lowest compared to other conditions.2.Study on the sound field characteristics of centrifugal pump gap drainage.Through the gap drainage of the impeller blades,the pressure distribution of the blade pressure surface and the suction surface is adjusted,thereby improving the flow of the impeller outlet.The results show that the pressure difference between the pressure surface and the suction surface of the impeller blade is the main factor that causes the impeller tail-jet and uneven flow at the outlet.The blade trailing edge ga p can well balance the pressure distribution on both sides of the blade and reasonably improve the flow state at the exit of the impeller.Slit blades have a certain positive effect on reducing the sound pressure level of the internal and external sound fi elds.When the radial slit diameter is?=0.9,the sound pressure level decreases significantly,and the wider the gap width,the lower the sound pressure level,but the head loss increases,the noise reduction effect of the centrifugal pump is optimal when the gap width?=0.500.3.Research on the noise performance of centrifugal pumps by cutting the front and back cover plates of impeller.By cutting the front and back cover plates of impeller,the diameter of the blade is kept unchanged,thereby reducing the impact of the impeller outlet fluid on the volute.The results show that:cutting the impeller cover can reduce the turbulent kinetic energy fluctuation area of the blade trailing edge,weaken the vortex strength in the volute,and thus improve the fluid flow state.The pressure pulsation is related to the sound pressure level of the internal sound field,the side reflects the size of the sound pressure level,and the diaphragm is the main noise source.Cutting the impeller cover can effectively reduce the pressure pulsation inside the volute,thereby reducing the internal and external sound field noise.Cutting the impeller cover and keeping the blades can effectively reduce the noise while ensuring a small head loss.When?a=7mm,that is,the percentage of the cut is?a/D₂=5.4%,the noise reduction effect is the best.The external sound field distribution of the fluid-excited pump body is jointly affected by the shape of the pump body and the internal flow field.The maximum value of the sound pressure level is mainly distributed around the susceptible base and the pipeline with less freedom constraints.