Investigation On The Characteristics Of Gas-Oil Flow And Heat Transfer In A Bearing Chamber

With the whole performance of aero-engine increment, the thermal load of bearing chamber at principal axis fulcrum become large. The heat conducted from high temperature surrounding through cavity wall and bearing seat increased besides the heat generated from roll bearing gose up. Many problems such as oil over heated and oil fired have occurred. All of these will affect the working performance of bearing and reliability of aero-engine. So it is very necessary to investigate the air-oil two phase flow in the bearing chamber to obtain the rule of the mixture lubricant flow and heat transfer in the chamber.Based on the analysis of investigations home and aboard, an aero-engine back fulcrum bearing chamber was studied and the simplified test rig was built up. The proportion of air flow through the vent port and the temperature raise of oil pumped out through the scavenge change with different rotate speed were found through the experiment. Based on the algebraic slip mixture model and Euler-Euler model, the commercial computational fluid dynamics software Fluent is introduced to simulate the air-oil two phase flow and heat transfer in teat rig bearing chamber. Compared with test results, it is reliable to use the algebraic slip mixture multiphase model and RNG turbulence model to simulate the multiphase flow. This method was adopted to simulate several real working condition in a complex geometry configuration bearing chamber, and the rule of oil temperature rise, proportion of oil pumped out through different port with the change of shaft rotate speed, air leakage, and oil supply were obstained. In order to make it simple to use the studied result and computational method, a bearing chamber thermal analysis software was developed. Gambit and Fluent were included in this software so as to simplify the designer's operation. It can achieve many functions, such as modeling, grid generation, fast calculation and results management. The fluid film which has the same flow direction with the shaft rotation was found at high rotate speed. Based on S.Witting's oil film model, a computing program was developed to investigate the oil film depth and velocity profile. Using this program, some work conditions tested by A.Glahn were carried out. The numerical simulations fit very well with the test results. It is proved that the program is correct and a solid foundation was established to develop further the model of oil film heat transfer.The conclusion in this thesis can provide theoretics and technology for bearing chamber thermal design.