| The change of key parameters in the diaphragm area of the double volute centrifugal pump will not only affect the hydraulic performance of the centrifugal pump,but also play a key role in controlling the flow-induced vibration and noise of the centrifugal pump.In order to improve the hydraulic performance of th e centrifugal pump and ensure the stability and safety of the pump operation,this paper takes the double-volute centrifugal pump with a specific speed of 83 as the research object.By changing the installation angle of the separating tongue,the gap between the separating tongue and the impeller,The rounding radius of the partition tongue is optimized for the double-volute centrifugal pump,and the influence of the flow-induced vibration and flow-induced noise of the double-volute centrifugal pump is studied by changing the important parameters of the partition tongue area.The specific research content and related conclusions of this topic are as follows:1.Analysis of pressure pulsation distribution and noise transmission law of double volute centrifugal pumpComparing the performance of the double-volute centrifugal pump head,output power and efficiency under different working conditions,the efficiency value is the highest when 1.2Qopt is obtained.The fluid velocity near the rear cover of the impeller is higher than the fluid velocity near the front cover.This is because the fluid velocity in the wake area is relatively small,and it is attached to the outlet of the suction surface of the blade and closely adheres to the front of the impeller.The surface of the cover,and the surface of the rear cover of the impeller and the pressure surface of the blade are attached to the jet area with a relatively high relative speed.The static pressure value of the point far away from the volute separation tongue is lower,and the influence of the backflow and the secondary flow near the separation tongue is gradually reduced,making the fluid flow state gradually stable.The change law of pressure pulsation at each point is studied in detail,and it is found that the pulsation peaks of each model pump are located at the blade frequency and multiplier frequency,and the points arranged along the radial,circumferential and axial directions of the volute.Compare the trend of pressure pulsation.,There is a clear increase and decrease relationship.In order to ensure the accuracy of noise calculation,the pressure pulsation frequency domain information of the radial monitoring point is compared with the sound pressure level calculated by the acoustic software.The result shows a positive correlation,and all directions can be found The noise change on the above coincides with the pressure pulsation,indicating that dynamic and static interference and jet-wake action are important causes of pressure pulsation and noi se.The pressure pulsation at each point gradually away from the outlet of the impeller appears to gradually decrease.Due to the weaker and weaker impact of the impeller,the peak value of the pulsation becomes smaller and smaller.Compare the pressure pu lsation at each point along the axial direction of the volute.The peak value of point z6-1 near the rear cover plate is slightly higher than the point z6-2 near the front cover plate.This is due to the influence of the jet-wake effect of the blade exit,resulting in the pressure surface of the impeller blade and the rear cover plate.The jet area with relatively high relative velocity,and at the exit of the suction surface of the blade,there is a wake area with a relatively small relative speed,and it is close to the front cover surface of the impeller,so that the pressure pulsation peak at point z6-1 near the rear cover is slightly larger than that at point z6-2 near the front cover.The pressure pulsation at various points along the circumference of the volute shows the peak sound pressure level from point j5-1 to point j7-1,showing a gradual decrease.The peak sound pressure level at point j5-1 is greater than j6-1 Point and j7-1 point peak value.2.The influence of the installation angle of the se parating tongue on the pressure pulsation and noise of the double volute centrifugal pumpAfter comparing the external characteristic parameters of each model,it is found that the efficiency value is the highest when the installation angle is 25°.From the velocity distribution diagram,it can also be seen that in the tongue area of the double-volute centrifugal pump and the starting end of the separator of the centrifugal pump,a large range of vortices can be found.This is because the relative velocity of the fluid in the wake Obviously lower than the relative velocity of the jet zone,the high-speed jet on the pressure surface of the blade meets the low-speed wake on the suction surface of the blade to form a vortex.The influence of the change of the placement angle on the pressure pulsation at each point is studied,and the main frequency of the pressure pulsation at each placement angle is also located at the leaf frequency and the doubling frequency.When the tongue placement angle is 20°,the pressure pulsation amplitude fluctuates the least.It can be seen from the comparison chart of sound pressure level amplitude that when the installation angle is 20°,the sound pressure level amplitude is the lowest.It can be seen from the overall sound pressure level cloud diagram of the centrifugal pump that as the frequency increases,the sound pressure level shows a decreasing trend.3.The influence of the radial position of the diaphragm on the pressure pulsation and noise of the double volute centrifugal pumpChanging the radial position of the diaphragm will affect the size of the gap between the volute and the impeller,which not only affects the overall performance of the pump,but is also closely related to the internal fluid flow,pressure pulsation and changes in sound pressure level.On this basis,the radial position of the diaphragm is modified,and the lift,output power and efficiency of each model are analyzed.It is found that the model pump has the lowest efficiency value when the impeller-diaphragm gap is 10.3mm,which is more efficient than the original model.The value is reduced by 0.11%.The peak of the sound pressure level has a trend of decreasing with the increase of frequency.From the comparison chart of the sound pressure level amplitude,it is found that the maximum sound pressure level is the smallest when the gap between the impeller and the tongue is 9.3mm.In the sound pressure level cloud diagram,it is found that with the continuous increase of the radial gap between the impeller and the tongue,the minimum sound pressure level of each model at the 7-fold axial frequency shows a trend of first increasing and then decreasing.4.The influence of the rounding radius of the separating tongue on the pressure pulsation and noise of the double volute centrifugal pumpAfter comparing the external characteristic parameters of each model,it is found that the efficiency value of the model pump is the highest when the rounding radius is1.8mm,which is an increase of 0.23% compared with th e original model efficiency value.It can also be seen from the velocity distribution diagram that a large range of vortices can be found in the tongue area of the double-volute centrifugal pump and the starting end of the separator of the centrifugal pump.This is because the relative velocity of the fluid in the wake area is obvious.Less than the relative velocity of the jet zone,the high-speed jet on the pressure surface of the blade meets the low-speed wake on the suction surface of the blade to form a vortex.Next,the study on the influence of the rounding radius of the separating tongue on the pressure pulsation characteristics of the centrifugal pump was analyzed,and the results showed that the main frequency of the pressure pulsation under each m odel is at the blade passing frequency and the doubling frequency position.When the rounding radius of the separating tongue is 0.9mm,Its pulsation amplitude is significantly higher than other models;the pulsation amplitudes of the other four models are not significantly different.The pressure pulsation of the original model is lower than that of the modified model in the tongue area and the starting end of the diaphragm.It can be seen from the sound pressure level cloud chart that the maximum sound pressure level when the rounding radius of the tongue is 0.9mm and 2.1mm is lower than other models,and the value is 185 d B. |
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