The Research On The Effect Of Reflux Orifices On The Performance And Internal Characteristics Of Self Priming Pumps

Self-priming pumps are widely used in industrial production and life.Therefore,it is of great significance to study the influencing factors of self-priming performance of self-priming pumps and the internal mechanism of influencing factors affecting self-priming performance of self-priming pumps for guiding the design of self-priming pumps.As one of the important factors influencing the self-priming performance of the self-priming pump,it is necessary to study the influence of the shape,radial distance and angle of the return hole on the self-priming performance of the self-priming pump.This paper takes ZX12-25 externally mixed self-priming pump as the research object.Based on the model,the shape,radial distance and angle of the return orifice are changed respectively,and the influence of the changes of the above factors on the self-priming pump internal characteristics is analyzed.Finally,based on the full-factor test method,the main influencing factors on the self-priming performance and hydraulic performance of the self-priming pump are analyzed,and the interaction of the above factors on the self-priming performance of the self-priming pump is analyzed.1.This thesis takes ZX12-25 self-priming pump as the research object,builds simulation model based on the external mixing self-priming pump,and uses ANSYS Fluent fluid simulation software to simulate the pump,obtaining the head efficiency curve of the simulation model.Hydraulic performance test is carried out on the solid pump and the accuracy of the simulation model is verified by comparing simulation data with test data.2.Among the three schemes with different shapes of return orifice,the amplitude at blade frequency of the lumbar-orifice scheme is significantly higher than that of the other two schemes,and the pressure change at the return orifice is more intense than that of the other two schemes.Therefore,although the peak value of lumbar-orifice type return flow is the largest,the flow fluctuation of return fluid in the lumbar-orifice scheme is greater and the oval return flow rate is the most stable.Therefore,the gas content in the self-priming pump body of the three schemes with oval return orifice Round return hole scheme has more but slightly less than lumbar hole scheme,i.e.oval return hole scheme has the shortest self-priming time and lumbar hole scheme has the longest self-priming time.The low-speed fluid returned through the return orifice is distributed at the outer edge of the volute from the return orifice of the volute to the inlet of the diffuser.The high-speed fluid at the outlet of the impeller collides with the lowspeed fluid,which increases the fluid pressure from the return orifice of the volute to the inlet of the diffuser.The radial force of the impeller increases in this direction,which makes the radial force of the impeller eccentrically distributed as a whole.However,the radial force fluctuation of the impeller3.In the early stage of self-priming process of self-priming pump,the scheme of return hole with reduced radial distance is closer to the orifice ring,so that more return liquid flows into the impeller,which makes the mass fraction of gas in the impeller drop sharply at 0.3s,and a distinct liquid belt is formed from the third section to the outer edge of the volute of the return hole.In the case of constant radial distance,the whole pressure fluctuation amplitude in the volute is larger.4.In the early stage of self-priming process,the counterclockwise rotating return orifice scheme impeller sucks the gas at the fastest speed and the clockwise rotating return orifice scheme is the slowest.However,with the decrease of gas in the intake pipe,the in-situ return orifice scheme impeller sucks the gas at the fastest speed,so its self-priming time is shorter than the other two schemes.The pressure fluctuation frequency domain clockwise rotation of the return orifice scheme has the largest amplitude at the single blade frequency,26% and 8% larger than the clockwise rotation of the return orifice scheme and the in-situ return orifice scheme respectively,which makes the self-priming time of the clockwise rotation of the return orifice scheme significantly higher than that of the clockwise rotation of the return orifice scheme and the in-situ return orifice scheme.5.The radial distance and angle of the return orifice are the main influencing factors of the efficiency of the self-priming pump.With the increase of the radial distance of the return orifice of the self-priming pump,the efficiency of the self-priming pump decreases,and the counterclockwise change of the angle of the return orifice also causes the efficiency of the self-priming pump to decrease to a certain extent.The shape,radial distance and angle of the return orifice of the self-priming pump have certain influence on the self-priming time of the self-priming pump.The self-priming time of the self-priming pump will increase unlike the elliptical return orifice or the setting of the return orifice deviating from the original position.The three parameters have a great influence on the vibration amplitude of the self-priming pump,of which the angle of the return hole has the greatest influence,the lumbar hole shape and radial distance increase by 5 mm and the angle deflects clockwise by 15 degrees.The vibration amplitude of the self-priming pump is the smallest in the return hole scheme.