Experimental study of multiphase flow in a model gearbox

Abstract

This study concerns dynamics of a two-phase flow around a rotating solid body. Under consideration is a model of a gear wheel in a gearbox which rotates and is partially submerged in oil. The flow of interest is complex and involves effects of free surface dynamics, rotation, and formation of bubbles and drops. Occurring flow regimes include laminar, transitional and turbulent. The major focus of the investigation is on details of the developed flow, and the purpose is validation of numerical methods developed for design and optimization of such components. Current experiments are performed in a test rig which is modelling a generic simplified gearbox with a single isolated rotating wheel. The flow measurements are carried out by using particle image velocimetry (PIV) and the test rig is specially designed for this purpose with the optical access maximized. The flow similarity with respect to a real gearbox is fully maintained and the working fluid is a transparent mineral oil. The PIV measurements are performed at four different rotation speeds for two different wheel configurations in order to cover a spectrum of operational conditions needed for numerical modelling. The emphasis is on the result of experiments on a smooth wheel. The measurements are providing velocity distribution around the wheel and details on bubble and drop distribution.

Numerical modeling of the churning power losses in planetary gearboxes: An innovative partitioning‐based meshing methodology for the application of a computational effort reduction strategy to complex gearbox configurations

“…In between a lubricant foam (air‐lubricant mixture) generates. This foam is also present in the gaps between the teeth as shown experimentally by Chernoray . Figure N shows clearly that when the gears mate, this foam condensates ensuring the separation of the gear flanks through the formation of a lubricant layer.…”

“…This foam is also present in the gaps between the teeth as shown experimentally by Chernoray. 34 Figure 15N shows clearly that when the gears mate, this foam condensates ensuring the separation of the gear flanks through the formation of a lubricant layer. This is fundamental to reduce the friction coefficient as well as to prevent damaging like wear and scuffing.…”

Mass Flux Distribution Measurements and Visualizations of a Fluid Sheet Generated by a Partially Immersed Dip-Lubricated Gear

“…One may assume that the weakened boundary condition significantly reduces the driving efficiency of the gear compared to a viscous pump of full solid cylinder. This is not the case, as measurements by other authors, like [19] and [20] show that for large speeds, the boundary layer momentum thickness and the driven mass flow does not differ significantly between a gear with teeth and a smooth, solid cylinder which has the same width and diameter as the gear tip diameter. …”

“…The authors of [19] used flash flow field visualizations and PIV on a single smooth gear and a mesh gear partially immersed in fluid in a closed large rectangular tank. Apart from the few shown visualizations, the comparison of momentum thickness distributions in the boundary layer around the immersed parts showed that for large Reynolds numbers, the momentum thickness distribution of a gear and a cylinder do not differ significantly.…”

Effect of the static pressure on the power dissipation of gearboxes

“…The reduction of the power loss can be explained looking at the way in which, with the lower static pressure, the air pillow (Figure ) that takes place around the submerged portion of the gear completely covers the teeth while for the environment pressure condition, air is trapped only in the bottom of the teeth gaps and the teeth tips interact with the lubricant (higher viscosity and density and consequent pressure peaks) causing the higher power dissipation. In dip‐lubrication, in fact, the loss is significantly dependent from the distribution of the contact areas between teeth and the lubricant …”