Correlations for heat generation and outer ring temperature of high speed and highly loaded ball bearings in an aero-engine

Advanced aircraft engine development in recent years has dictated increased rotational speeds with the consequence of increased mechanical stress requirements for rolling element bearings. A vast amount of heat is rejected which results in high oil scavenge and bearing metal temperatures. A ball bearing and its associated chamber from an RB199 turbofan Engine were used in an experimental investigation to determine the impact of several operating parameters on the scavenge and bearing race temperatures. The test bearing was a 124 turn PCD ball bearing with a split inner-ring employing under-race lubrication by two individual jets providing oil through each half of the inner-ring. The bearing run over a wide range of D times N (DN) values ranging from 0.3 x 105 to 2.1 x 10(6) rpm x turn with D the bore diameter of the bearing. The direction of the oil ingestion in the bearing (for or against the direction of the axial load) was found to have a considerable effect to the oil distribution and consequently to the heat generation in it. A significant reduction in the heat to oil was achieved when the oil was fed at certain proportions (ratio) by the two nozzles. Heat to Oil and Outer ring metal temperature correlations which consider the influence of the direction of oil ingestion relative to the direction of the axial load have been developed and compared to test results. This work is part of the European Research programme Brite Euram, ATOS (Advanced Transmission and Oil Systems). (c) 2006 Elsevier Masson SAS. All rights reserved.