A Multiphase Computational Study of Oil-Air Flow Within the Bearing Sector of Aeroengines

Abstract

The bearing chamber of an aeroengine houses roller bearings and other structural parts. The spatial limitation, high operational speeds of the HP shaft and the proximity to the combustion chamber can make the operating conditions of the bearing chamber challenging. A roller bearing consists of an inner race, an outer race and a cage constraining a number of rolling elements. In the aeroengine application, oil is introduced into the bearing chamber via the inner race regions of the bearing into the rolling elements interstices. This provides lubrication for the roller bearings. The source of heat in the bearing chamber is mainly from rolling contact friction and the high temperature of combustion. Cooling results from the oil transport within the bearing chamber and thus an efficient transport of oil is critical to maintaining the integrity of the entire structure. The bearing chamber contains the oil which is eventually scavenged and recycled for recirculation. Experiments have been conducted over the years on bearing chamber flows but often simplified to create the best emulation of the real aeroengine. The complexity of the bearing chamber structure is also challenging for experimental measurements of the oil characteristic in the roller bearing elements and the bearing chamber compartment. Previous experiments have shown that the oil continuum breaks up in the bearing chamber compartment but it is not quantitatively clear how and what parameters affect these. Previous simulation attempt of bearing chamber, also, have been limited by the boundary conditions for the oil. This work presents a computational fluid dynamics (CFD) transient simulation of flow in the bearing sector in an attempt create boundary conditions for such models. The current results show that the oil emerges in the form of droplets into the bearing chamber compartment with speed of the order of 10% of the shaft rotation.

Jet cooling for rolling bearings: Flow visualization and temperature distribution

“…Most of the oil is used to provide sufficient cooling capability [4,12]. Besides, the heat dissipation characteristic and the oil-air flow characteristic in a bearing can be largely affected by parameters such as pockets shape and contact angle [13,14]. For this reason, a sufficient assessment of the flow around the ball bearing is helpful when the jet cooling performance is investigated.…”

Oil-Air Flow Between the Cage and Inner Race of an Aeroengine Bearing

“…Table 1 gives the matrix of the cases that have been run. The case nomenclature is such that those starting with S refer to the cases with slotted feed, Q refer to the feed through a hole in the race with 40 • separation and H for hole feed with 60 • separation Mesh dependence A full mesh independence study has not been conducted for this modelling work because it builds largely on work previously reported [13]. The only parameter investigated was the number of cells across the gap between inner race and cage.…”

Innovative Meshing Strategies for Bearing Lubrication Simulations

“…Steady-state approaches relying on rotating reference frames were used by several authors. Among them, Raju et al [22] who studied needle bearings, Adeniyi et al [23] who studied aeronautical bearings and Wen et al [24] who simulated ball bearings. These approaches could be effective for rotating elements.…”