Research On Cavitation Process And Prevention Measures Of External Gear Pump Based On Numerical Simulation

External gear pumps are widely used in agricultural machinery,engineering machinery,and aerospace due to their many advantages such as simple working principles.However,due to structural limitations,cavitation has always been an important factor restricting their development.In addition,in recent years,the speed of the pump and the pressure in industrial production is getting higher and higher,which exacerbates the cavitation phenomenon of the pump.Therefore,this subject researches on the cavitation of gear pumps,uses numerical simulation to analyze the causes of cavitation of gear pumps and the influence of cavitation on pump performance,and proposes specific measures to suppress cavitation of gear pumps.Provides a technical idea for improving the working performance of the pump and prolonging the service life of the pump,which has important engineering practical value.First,by understanding the basic theory of cavitation and the basic model of numerical calculation,the conditions of various types of cavitation and the governing equations used in the numerical calculation were clarified;a simulation model was established,by comparing the results of numerical and theoretical calculations,the accuracy of the simulation model was analyzed.The results show that the calculation model is more accurate when the gear mesh clearance is 5 ?m and the number of meshes is about 210,000.Next,the oil flow state in the pump at several key positions was analyzed,and the basic law of oil pressure change was obtained.Through numerical simulation,the changes of pressure,velocity and gas volume fraction in the flow field were analyzed.The causes of cavitation of gear pumps,the conditions of cavitation and the main types of cavitation were obtained.The results show that the cavitation phenomenon of the gear pump is caused by the suction phenomenon and high-speed swirling flow;the increase of the speed is the main condition of the pump cavitation;the gas cavitation dominates the pump cavitation process.Then,the cavitation of different degrees was simulated by controlling the gas content in the oil in the pump,and numerical calculations were performed to analyze the effect of the degree of cavitation on performance parameters such as the oil suction capacity,outlet flow rate,and volumetric efficiency.The results show that the increase in cavitation will increase the stability of the pump's suction,but will reduce the pump's efficiency;the more severe the cavitation,the worse the stability of the pump's outlet flow,the worse the volumetric efficiency,and the lower the volume efficiency;Increase;cavitation has less effect on trapped oil pressure.Finally,three cavitation prevention measures were proposed: increasing the size of the suction port,designing the type of the relief groove,and changing the shape of the gear,and the effectiveness and feasibility of these measures were analyzed and verified.The results show that: increasing the size of the suction port can reduce the cavitation of the pump.The relief groove can improve the cavitation characteristics of the pump,but different types of relief groove have different capabilities,and the special-shaped relief groove have the best effect;the serrated gear can suppress the occurrence of cavitation.