Development Of Accelerated Life Test System For Shaft Seal Of Airborne Hydraulic Pump

Airborne hydraulic pump is a crucial hydraulic component that provides pressurized liquid for hydraulic transmission mechanism.The onboard hydraulic pump prevents the return oil leak through a mechanical seal on the shaft tail.The failure or degradation of the mechanical seal will cause the performance deterioration of the power systems of aircrafts.To date,the life time of airborne hydraulic pump seals produced in China is lower than that of the similar products in the world-wide market.The material,structure,and manufacturing process of airborne hydraulic pump seals are the key factors affecting reliability.In order to evaluate the reliability of mechanical seals,a special test rig is needed to simulate the real environmental and working stresses in the flight of aircrafts to facilitate its reliability improvment.In this paper,the failure mode and effects analysis(FMEA)is conducted for mechanical seals to identify the key environmental stress of mechanical seals.Subsequently,a rig for the accelerated life testing of seals in the shaft and tail of airborne hydraulic pump is developed to facilitate the life prediction and reliability evaluation of seals.The major works of this thesis are as follows:(1)The main stress conditions associated with the failure mechanism of the shaft seal of airborne hydraulic pump are analyzed.Firstly,the sealing mechanism and classification method of mechanical seal are introduced,along with the main functions of each component of mechanical seal.Secondly,the failure mode and effects analysis of the airborne hydraulic pump seal system is conducted to determine the prone-to-failure components in mechanical seals.Lastly,the environmental stress is identified in accordance to the major causes of the mechanical seals failure,and the result provides a theoretical basis for the design of the accelerated life test device.(2)A design scheme of the test rig for the accelerated life test of mechanical seal is proposed.Firstly,the parameters to be measured are determined in accordance to the major stress conditions of mechanical seal and the weak components of mechanical seals.Secondly,a sealing medium supply device is designed to simulate the two stress conditions of oil pressure and temperature for the test rig.Lastly,a new experimental method for torque and speed test is proposed.The test can reveal the change of the torque of mechanical seal in the initial start-up and the stable operation phases.(3)A system control scheme for the designed test rig is developed.Firstly,the configuration and program control of the test rig are presented.Secondly,the spindle drive system and data acquisition system are designed for the speed control of the test rig,along with the servo motor communication message and sensor selection.Thridly,the PID optimization for the hydraulic system is developed.Lastly,the main circuit design of the electrical control system is provided based on the basic electrical equipment specification and daily maintenance regulations.