Detailed Investigations on the Oil Flow in Dip-Lubricated Gearboxes by the Finite Volume CFD Method

Abstract

Three main concerns are in the focus of the development of geared transmissions nowadays: load carrying capacity, noise-vibration-harshness (NVH) behavior, and efficiency. Increasing the efficiency of modern gearboxes contributes significantly to the reduction of energy consumption and the saving of resources. Gearboxes are frequently designed conservatively with an oversupply of oil to guarantee operational reliability. An oversupply of oil results in an unnecessarily high amount of oil kept in motion and to high no-load losses. Detailed information on the oil distribution in the early design stages of gearboxes would help to optimize the lubrication and to increase the efficiency. Thereby, CFD (computational fluid dynamics) methods offer a very flexible way to visualize the oil flow inside gearboxes with much fewer restrictions compared to measurements with transparent gearbox designs. In this study, a verified CFD model based on the finite volume method is used to investigate the oil flow in a single-stage gearbox. Different oil viscosities and circumferential speeds are considered. The investigations focus on the oil flow. The gear churning loss, as part of the no-load loss, is additionally considered. Experimental validation is obtained by high-speed camera recordings and measurements at the FZG no-load power loss test rig. The results show very strong agreement between simulation and measurement. The results show that CFD simulations can visualize the oil flow behavior with a very high degree of detail.

WITHDRAWN: Numerical Visualization of Grease Flow in a Gearbox

“…The test gearbox features the same geometry as considered in previous studies (Liu et al [3][4][5]). It contains a pair of spur gears with a gear ratio of 1.5.…”

“…In this study, a high-speed camera of type Photron FASTCAM Mini AX200 is used. The considered gears are case-hardened test gears of FZG type C-PT as used in [3][4][5]. The main geometry data for both the pinion and wheel is shown in Table 1.…”

“…In the context of the lubrication of geared transmissions, the application of computational fluid dynamics (CFD) methods has developed into a helpful tool for assisting with the design of fluid flow in gearboxes. Most CFD studies have focused on oil lubrication, e. g. Liu et al [3][4] [5], Concli and Gorla [6][7][8], Kvist et al [9] and Klier et al [10]. Whereas oil can usually be considered as Newtonian fluid at low shear rate and pressure, grease exhibits complex non-Newtonian flow behavior.…”

Efficiency and heat balance calculation of worm gears

“…Friction within the contact of two tooth flanks relates to the applied load of the tooth system and results in load-dependent gear losses (P VZP ). Churning losses, squeezing losses, impulse losses and ventilation losses are related to the oil flow in the gearbox [18]. They are referred to as no-load gear losses (P VZ0 ) as they are almost independent from the applied load.…”

Influence of the Dynamic Motion of a Splash-Lubricated Gearbox on Churning Power Losses

“…It is difficult to predict oil churning loss directly by theoretical methods, because its determination is affected by many factors, such as the complex inner shape of housing of gearboxes, flow field characteristics inside gearboxes, etc. [6][7][8][9].…”