Thermal Analysis of an Oil Jet-Dry Sump Transmission Gear Under Mixed-Elastohydrodynamic Conditions

Abstract

Improved fuel efficiency and reduced emissions are key drivers for modern drivetrain systems. Therefore, in recent years, dry sumps with air–oil mist lubrication have been used for efficient transmission design in order to reduce the churning losses. With dry sumps, appropriate cooling measures should be implemented to dissipate the generated contact heat in an efficient manner. This paper integrates a tribological model with three-dimensional (3D) thermofluid analysis in order to predict the heat generated in the lubricated meshing gear contacts and its dissipation rate by an impinging oil jet in air–oil mist environment. Such an approach has not hitherto been reported in literature. The results show that the generated heat under realistic conditions cannot be entirely dissipated by the impinging oil jet in the air–oil mist transmission casing. Numerical results are used to derive extrapolated regressed equations for heat transfer purposes for time-efficient analysis. These conform well with the detailed numerical results.

Transient thermal analysis of mixed-elastohydrodynamic contact of high performance transmission in a dry sump environment

“…The computational fluid dynamics model A standard k-" turbulence model is developed to analyse an impinging lubricant flow on a rotating gear. The model is similar to that developed through CFD by Fatourehchi et al, 18 which was qualitatively validated against the findings of DeWinter and Blok. 15 The governing equations for conservation of mass and momenta for each phase in a 3D Newtonian and incompressible turbulent flow are according to the approach proposed by Hou and Zou 34 as follows.…”

“…The model is similar to that developed through CFD by Fatourehchi et al [18] which was qualitatively validated against the findings of DeWinter and Blok [15]. The governing equations for conservation of mass and momenta for each phase in a 3D…”

“…They used estimated analytical equations for heat transfer coefficients on different parts of their model. Recently, Fatourehchi et al 18 developed a transient multiphase computational fluid dynamics (CFD) model to more accurately determine the heat transfer coefficients for different parts of a loaded gear pair for a wide range of operational conditions. They introduced regressed equations as an aid for the calculation of heat transfer coefficient on a gear surfaces lubricated and cooled under dry sump lubrication system.…”

A system level computational model for thermo-tribological functioning of high-performance racing transmission with dry sump lubrication

“…A similar approach was developed by Long et al 20 to investigate the effects of geometrical and operational conditions as well as lubrication conditions on the surface temperature of high-speed gear teeth. Later, Fatourehchi et al 21 determined these heat transfer coefficients more accurately using a transient multiphase CFD model.…”

Improvements in the mixed elastohydrodynamic lubrication and in the efficiency of hypoid gears

“…Some of them are referenced. [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] The geometrical separation of contacting tooth surfaces has an important role in the mixed EHL. Nowadays, in all the hypoid gears, appropriate tooth surface modifications are introduced to reduce the sensitivity of the gear pair to tooth errors and misalignments inherent in the gear box and to avoid the very dangerous edge contact.…”