Performance Comparison for Aeroengine-Type Sump Geometries

Abstract

Oil removal from aeroengine bearing chambers presents a challenge for aeroengine designers. Effective scavenging of oil is necessary to avoid excessive heat in the bearing chamber as this may lead to degradation of oil properties and deterioration in heat transfer functionality. However the task of oil removal is not trivial. Oil is entrained in a highly rotating environment induced by rotating shafts. An aeroengine scavenge pump must remove both air and oil from the chamber and the ratio of the two fluids depends on pump operating point as well as the geometry of the exit region. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems is conducting an on-going experimental programme investigating liquid and gas flow behaviour in a relevant highly rotating environment. Previously reported work [2, 4] in combination with work conducted by Purdue University [3, 5] suggests that a deeper sump may help to reduce residence volume. More recently a study has been conducted that investigates geometries incorporating features sometimes included in aeroengine scavenge. Three very different exit geometries were investigated experimentally using chamber residence volume as a parameter of comparison. Data for one of these, the so called Curved Wall Deep Sump (CWDS), has already been reported in [4]. This paper presents residence volume data for all three sumps over a range of shaft speeds, inlet flow rates and scavenge ratios. Trends are analysed and presented and areas for future work identified.