Abstract
The bent-axis piston pump is the core component of electrohydrostatic actuators (EHA) in aerospace applications, and its wear of key friction interfaces is greatly related to the healthy operation of pumps. The leakage of the piston ring-cylinder bore interface (PRCB), as the important part of the return oil flow of the pump house that commonly assesses the wear of key friction interfaces in piston pumps, is changed with the rotation speed. Thus, the wear of key friction interfaces is usually inaccurate by using the leakage of PRCB. In order to obtain the relationship between the PRCB leakage and the rotation speed, an elastohydrodynamic lubrication model is proposed. First, the proposed model includes a minimum film thickness model of PRCB to analyze the dynamic change of oil film of PRCB when subject to the elastohydrodynamic lubrication. After that, a mathematical model of PRCB is induced by combining the minimum film thickness model with the flow equation, which helps produce the effects of the oil film on the leakage of PRCB. The proposed model is verified by numerical simulation and experiment. The results show that the leakage of PRCB has a negative effect on the return oil flow of the pump case in the range of rotation speed of 700–1300 r/min and discharge pressure of 10–20 MPa. Furthermore, the leakage of PRCB is proportional to the rotation speed, but the return oil flow of the pump case is decreased. The effects of rotation speed are enhanced under the high discharge pressure conditions.
Highlights
Bent-axis piston pumps are widely used in electrohydrostatic actuators (EHA) in aerospace applications due to the advantage of miniaturization and lightweight through high speed and high pressure. erefore, the bent-axis piston pump greatly affects the healthy operation of EHA [1,2,3]
As the wear increases with pump working time, the lubricating interface gap increases and the lubricating interface leakage increases, which eventually leads to the increase of the return oil flow rate of the pump case [10, 11]
The lubricating interface leakage is inevitably changed with the varying working conditions, such as the rotation speed, which affects the accurate evaluation of wear states
Summary
Bent-axis piston pumps are widely used in electrohydrostatic actuators (EHA) in aerospace applications due to the advantage of miniaturization and lightweight through high speed and high pressure. erefore, the bent-axis piston pump greatly affects the healthy operation of EHA [1,2,3]. Kumar established the theoretical model of the piston ringpiston bore pair in the bent-axis piston pump with rectangular cross-section of piston ring and analyzed the leakage flow characteristics between piston ring and cylinder bore under different working conditions through numerical simulation and test [21]. Some researchers studied the effects of the elastic deformation and micromotion of piston ring on the oil film thickness, pressure field, and friction force of PRCB in the bent-axis piston pump under certain rotation speed conditions. The variable speed and wide speed are the typical working conditions of bent-axis piston pump in EHA, and the influence of rotation speed on PRCB leakage considering elastohydrodynamic lubrication effect has not been fully elucidated.
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