| The external gear pump has many advantages,such as compact structure,easy processing and manufacturing,large speed range,and insensitivity to oil pollution,so it is widely used in machine tools,engineering machinery and other hydraulic systems.In order to meet the requirements of modern industry and hydraulic transmission control systems,high-pressure,high-efficiency gear pumps have become the development trend of the hydraulic industry,but when the working pressure of the gear pump is increased,the phenomenon of oil reflux will occurs inside the pump,which leads to the increase of pump leakage,the decrease of the volume efficiency and the increase of radial force.Therefore,to achieve the high pressure of the gear pump,we must make a breakthrough in the following two aspects: on the one hand,it is necessary to reduce the leakage of the pump under high pressure,so that the pump can maintain a high volumetric efficiency;on the other hand,it is necessary to reduce the radial force,improve the bearing capacity of the shaft and the bearing,and prolong the working life of the pump.This paper takes a certain type of involute external gear pump as the research object,with the purpose of improving the working pressure and volumetric efficiency of the pump,analyzes its radial force,clearance leakage,trapped oil characteristics,etc,provides a theoretical basis of the external gears in further study.The main research work of this paper can be summarized as the following 5 points:1.The flow characteristics,turbulence theory,fluid dynamics and the three major control equations of and the viscous fluid motion equations are taken as the research foundation of the dynamic theory.Firstly,two-dimensional drawing software CAXA is used to model the pump,and then GAMBIT is used to mesh the model.Finally using FLUENT dynamic grid simulation technology to analyze the external gear pump's trapped oil phenomenon.2.Based on the existing theory,the calculation formula of the radial force of external gear pump is deduced.The factors that affect radial force are analyzed from the theoretical calculation formula and the model structure.Proposed to expand the high pressure zone,expand the low pressure zone,open the hydraulic balance slot,reduce the size of the pressure inlet to reduce the radial force,thereby reducing the radial load of the shaft and bearing,and prolong the service life of the gear pump.3.From the perspective of the change in trapped oil volume caused by the radial resultant force generated in the pump operation,the effect of the radial unbalanceforce on the trapped oil volume of the gear pump is analyzed by measuring and caculating the value of the trapped oil volume during one cycle from entering into meshing to exit meshing.4.The mathematical model of internal leakage for involute external gear pump was established;the leakage path in the pump was analyzed and the leakage flow was quantitatively calculated.For the purpose of minimizing the total power loss of the pump,The optimal value of the radial clearance and end clearance of the pump were obtained by theoretical analysis.5.The optimal clearance value of the pump was obtained by iterative calculation of the simulation program JLZY.CPP,and the mechanical efficiency and volumetric efficiency of the pump under the optimal clearance were obtained by the simulation program JLCY.CPP.The energy loss of the gear pump was analyzed by changing the clearance value of the gear pump,the outlet pressure and the rotation speed,and the total working efficiency was calculated. |
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