Study of Oil Film Heat Transfer in Gas Turbine Engine Bearing Chamber

A clear understanding of the heat transfer processes in a gas turbine engine bearing chamber at the design stage makes it possible to properly design the lubrication and sealing systems and ensure the future bearing safe operation. The heat transfer coefficient (HTC) calculated based on the classical Newton-Richman equation is widely used to represent the heat transfer data and useful for the thermal resistance analysis. However, this approach is only formally applicable in the case of a two-phase medium. While there is a need to model a two-phase medium, setting the flow core temperature correctly in the Newton-Richman equation is an issue that is analyzed in this study. The heat from the flow core is transferred to the boundary of the oil film on the bearing chamber walls by an adjacent air and precipitating droplets. The analysis showed that droplet deposition plays a decisive role in this process and significantly intensifies the heat transfer. The main contribution to the thermal resistance of internal heat transfer is provided by the oil film. In this regard, the study considers the issues of the bearing chamber workflow modeling allowing to determine the hydrodynamic parameters of the oil film taking into account air and oil flow rates and shaft revolutions. The study also considers a possibility to apply the thermohydraulic analogy methods for the oil film thermal resistance determination. The study presents practical recommendations for process modeling in the bearing chamber.