Design And Research Of The Hold Down Device In High Speed Aviation Fuel Pumps

The aviation fuel piston pump is one of the core components in an aeronautical powerplant,which is using for providing fuel in certain pressure and flow.The hold down device is the direct function of the slipper’s return stroke in the piston pump.When in a high speed condition,the moment of inertia of the slipper has a large impact on the hold down device.If the hold down device is inappropriate,the slipper cannot be pressed against the swash plate at all times,which will result in large leakage of the pump,low volumetric efficiency,and even damage to the parts.Therefore,the design of the device is the research focus in the normal operation of the pump,and has certain theoretical value and practical value.In this paper,the prototype of one aviation fuel pump is taken as the research object,and the cause of the failure under high speed conditions is analyzed.The hold down device is redesigned,supplemented by simulation analysis and experimental research.Firstly,the motion and force of the high-speed axial piston pump are analyzed,which lays a foundation for the calculation of the force in slipper and spring.Through the metallographic detection and stress-strain analysis of the faulty part,the cause of the failure in the device is determined.These work indicates the limitation of the device with central spring in the prototype at high speed.Furthermore,a new hold down device with fixed clearance is proposed,and the rigid-flexible hybrid dynamics model of the structure is built.The simulation proves the feasibility of the designed structure.The fluid model of the designed fuel pump is established,and the flow and pressure characteristics are obtained.Finally,the test prototype is processed and the corresponding test platform is built.It is verified by experiments that the designed device with fixed clearance can meet the specific working conditions.The main research contents of this paper are as follows:(1)Analysis of the motion and force in the fuel piston pump are studied under high speed conditions.The movement of the slipper and the piston in the fuel pump is discussed.According to the derived equation of motion,the force of the piston pair in the oil absorption zone and the oil extraction zone is further analyzed,and the required spring force of the hold down device is derived,whicn lays the foundation for the subsequent analysis of the return mechanism.(2)Modeling and simulation analysis of the central spring return mechanism are studied.For the failure of the prototype under high-speed working conditions,the metallographic detection and stress-strain analysis are used to determine the cause of failure.The spring force is discussed about how does it be affected by the high-speed working condition,and it is determined that the old prototype is not suitable under high-speed conditions.The dynamic simulation model of the prototype is built to reproduce the cause of the failure,and it is verified whether the calculated spring force can satisfy the return stroke of the slipper in the oil absorption zone.(3)The design of the new hold down device is proposed.The static ansys is applied to the weak part of the designed device.The flexible body of the retainer is generated by Ansys to be used in Adams for building rigid-flexible hybrid dynamics simulation model of the pump,which is used to ansys the retainer and also determine the feasibility of the new device.(4)The flow and pressure characteristics of the fuel pump under the new hold down device are discussed.Firstly,the fluid model of the prototype is built.The fluid characteristic is obtained by simulation.The pressure and flow characteristics of the prototype under variable conditions are discussed,as well as the characteristics influenced by the damping groove structure on the valve plate.The test prototype was processed,and the outlet pressure and outlet flow of the pump at different speeds,as well as the flow characteristics under the fixed outlet pressure were tested.It was verified that the designed hold down device with fixed clearance can meet the pressure and speed requirements of the rated working condition.