Study On Flow And Pressure Characteristics And Application Of External Gear Pump

The external gear pump has the advantages of compact structure,strong antipollution ability,good self-priming performance,stable and reliable operation,high-speed operation and low cost.However,it has the remarkable characteristics of large flow fluctuation and noise,and low volume efficiency at low speed.Therefore,this paper takes PH407-A20 external gear pump as the research object.The external output characteristics,internal pressure characteristics and pump control cylinder characteristics of external meshing gear pump are studied and analyzed in depth by using the methods of modeling,simulation and experimental verification.The flow,pressure,energy efficiency of external gear pump and characteristics of external gear pump driving single-rod hydraulic cylinder system are explored.Above research is of guiding significance to the development and design of gear pump.Firstly,the structure and working principle of the external gear pump is analysed and the control volume and flow between which are defined.The internal cavity of the pump is divided into four regions and flow and pressure characteristics of which are described by lumped parameter method.The calculation theory of flow rate and pulsation rate at the outlet of external gear pump is given,and the affection on the flow rate of the gear pump outlet is summarized.The dimension parameters of the pump are measured by three coordinate measuring instrument.Two-dimensional and three-dimensional models of the external gear pump are drawn by AutoCAD software and SolidWorks software.In the three-dimensional model,the parameters data used to build the hydraulic model are extracted by changing the rotation angle of external gear pump and imported into the multidisciplinary domain modeling software SimulationX.With the using of the components in the mechanical and hydraulic modules of the modeling software,the flow and pressure dynamic model of the external gear pump is built by the method of centralized parameters.The model precisely defines the geometric characteristics of the pump as the function of gear rotation angle making the model be of wide simulation versatility,which provides a useful tool for further innovative research of external gear pump.SimulationX is used to simulate the flow and pressure characteristics under different loads and the internal pressure and flow changes of single tooth volume.The no-load characteristics were studied.The effects of different rotational speeds on the deviation between simulation no-load displacement and geometric calculation displacement were studied.The displacement and volume efficiency and flow fluctuation rate were calculated verifying the accuracy of the simulation model.The simulation flow rate and theoretical value under different rotating speed conditions is compared.The model can deeply analyze the operation of the pump and give some simulation curves(such as the pressure between teeth)which are difficult to measure in some experiments which is helpful for predicting and evaluating the internal cavitation performance and output pressure and flow characteristics of the pump.The model of single rod hydraulic cylinder controlled by gear pump is built and its characteristics are analyzed.The characteristics of different speed steps,different frequency tracking and the pressure of hydraulic cylinder under different loads are analyzed in detail.At the same speed and displacement,the energy loss of the external gear pump control cylinder system is of no change,whose energy consumption of the system is increased and energy efficiency is improved with the increasing of load force.Finally,an external meshing gear pump experimental platform is built to test and verify the model.By comparing the experimental results with the simulation results,it is concluded that the simulation experiments of flow and pressure fluctuation trends under no-load and load conditions are consistent.