A Coupled Transient Thermal Elastohydrodynamic Lubrication Model for Radial Piston Motors

This study presents the computationally efficient transient mixed thermal elastohydrodynamic lubrication model for a multi-lobe radial piston motor. The periodic boundary condition and time domain segmentation for a coupled thermal system of equations enable a 500 times faster simulation than direct full-domain simulation. The accuracy of the developed model was validated with transient temperature measurement. The steady-state results suggest a large temperature rise in solid parts and lubricating films. At 350 bar and for 80 RPM, the temperature rises are 22.8°C for the roller–bushing and 88.1°C for the piston–cylinder interface. Due to a significant decrease in viscosity, the tribological performance of the piston lubricating interfaces degrades. The roller–bushing interface demonstrated partial rupture of the lubricating film, and the piston–cylinder interface showed 33% higher contact force and pressure during piston upstroke than the isothermal simulation. Overall, the developed method can be applied to any type of hydrostatic such as axial piston pumps and gear pumps while provides system-level transient thermal analysis under varying operating conditions.