A novel Fluid-Structure-Thermal Interaction (FSTI) model for modeling of the lateral lubricating gaps between gears and lateral bushes in External Gear Machines (EGM) is presented in this study. Pressure compensated lateral bushes are key design elements for efficient operation of EGMs for high pressure hydraulic applications. The axial balance of these elements determines their actual position during operation, with significant implications on the effective sealing capabilities of the displacement chambers and on the losses from viscous friction.

The FSTI model presented in this paper is the first model of the lateral lubricating interface in EGMs capable of considering the heat transfer, thermal effects in the fluid film and solid components as well as thermo-elastic deformation of the solids. These capabilities, alongside a fluid flow solver and a stress/deformation solver for solid components due to pressure loads, enable prediction of the film thickness in the lateral gaps in EGMs considering thermo-elastohydrodynamic lubrication (TEHD) for the first time. In the present study the formulation of the novel FSTI model and detailed results are discussed with a particular focus on understanding the implications of thermal and TEHD effects.

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