On the application of reynolds theory to thermo-piezo-viscous lubrication in oil hydraulics

The efficiency of fluid power motors and pumps is a subject to research, which has generated numerous publications during the last three decades. The main incentives for this research are optimization of reliability and efficiency through the study of loss and wear mechanisms, which are very difficult to study experimentally, whereby modeling and simulation are necessary. A common approach to theoretical investigation of the pressure generated in the lubricated joints is the use of Reynolds equation, in which the oil viscosity is modelled with dependency of both pressure and temperature. In this paper the derivation of Reynolds equation from the continuum assumption is reviewed and it is shown that the validity of Reynolds theory based pressure field solutions in oil hydraulic thermo-piezo-viscous lubrication models are subject to maximum bounds on the pressure and temperature field gradients. These bound must be evaluated a posteriori to validate that model results is complying with the principle of conservation of mass and momentum.