Volume of Fluid (VOF) Analysis of Oil-Jet Lubrication for High-Speed Spur Gears Using an Adaptive Meshing Approach

Abstract

In high speed gearbox systems, the lubrication is generally provided using nozzles to create small oil jets that feed oil into the meshing zone. It is essential that the gear teeth are properly lubricated and that enough oil gets into the tooth spaces to permit sufficient cooling and prevent gearbox failure. A good understanding of the oil behaviour inside the gearbox is therefore desirable, to minimize lubrication losses and reduce the oil volume involved, and ensure gearbox reliability. In order to reach these objectives, a comprehensive numerical study of a single oil jet impinging radially on a single spur gear teeth has been carried out using the Volume of Fluid (VOF) method. The aims of this study are to evaluate the resistant torque produced by the oil jet lubrication, and to develop a physical understanding of the losses deriving from the oil-gear interaction, studying the droplets and ligaments formation produced by the breaking up of the jet as well as the formation of an oil film on the surface of the teeth. URANS calculations have been performed with the commercial code ANSYS FLUENT and an adaptive mesh approach has been developed as a way of significantly reducing the simulation costs. This method allows an automatic mesh refinement and/or coarsening at the air-oil interface based on the volume of fluid gradient, increasing the accuracy of the predictions of oil break-up as well as minimizing numerical diffusion of the interface. A global sensitivity analysis of adopted models has been carried out and a numerical set-up has been defined. Finally several simulations varying the oil injection angle have been performed, in order to evaluate how this parameter affects the resistant torque and the lubrication performances.

CFD study of oil-jet gear interaction flow phenomena in spur gears

“…5c, the generated oil film is spreading on the flank and parts of the oil are flung off directly during the impact process, which is then further supported by the acting centrifugal forces. The predicted results agree well with the work by Fondelli et al (1,12) and Keller et al (2,13) The illustration of the observable flow phenomenology during the OGI in Fig. 5 shows the complex structure of the prevailing two-phase flow -in its geometric shape and in its temporal evolution.…”

“…Here and in the following discussions, the third impact of the oil-jet on the dry gear at is analysed. As concluded by Fondelli et al (12) , it was found that the preceding impacts contain start-up effects while subsequent impacts yield repetitive results.…”

“…ωN is analysed. As concluded by Fondelli et al (12) , it was found that the preceding impacts contain start-up effects while subsequent impacts yield repetitive results.…”

“…Although they mentioned the importance n of an accurate modeling of the oil distribution near the gear surface, the small-scale flow phenomena were not captured in detail. Fondelli et al (12) conducted more fine-resolved CFD simulations. They presented a CFD setup, also using the VOF method but with a more detailed focus on the OGI itself.…”

Jet cooling for rolling bearings: Flow visualization and temperature distribution

“…Many industrial applications use impinging liquid jet to provide an effective mode of heat transfer, such as electrical motor [1], gearbox [2] and steel rolling [3]. For high-speed transmission systems, such as aircraft engines, turbomachinery, and drive trains, oil-jet is applied to the ball bearing cooling [4].…”