A thermal-fluid coupling numerical study on the characteristics of air–oil two phase flow and heat transfer in a micro UAV bearing chamber

Abstract

Design of lubrication systems, particularly of bearing chambers, requires a sufficient understanding of the physical characteristics of the air–oil two phase flow. Due to a high shaft rotating speed of micro UAV (Unmanned Aerial Vehicle) engines, the heat production of bearings often results in a poor cooling effect on the bearings. In the present work, numerical simulation was conducted on the above topic for a certain type of UAV engine. Firstly, the heat production in the bearings was theoretically analysed, and a three dimensional structural model of the bearing chamber was built by Unigraphics (UG) software. Then on the FLUENT platform, some key physical fields, such as path lines, velocity and temperature distributions were presented and discussed, with the simulated results were verified by measured values under typical working conditions. Afterwards, the influences of some important operating conditions, including revolving speed, oil supply, and air inlet velocity were investigated. Finally, optimal values were suggested for each operating condition, taking into consideration the cooling effect, lubrication effect and engine efficiency.