58964 - Study of Oil Film Heat Transfer in Gas Turbine Engine Bearing Chamber 

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

Illia Petukhov, Taras Mykhailenko, Oleksii Lysytsia, Artem Kovalov

National Aerospace University “Kharkiv Aviation Institute”, Kharkiv, 61070, Ukraine

E-mail: t.mykhailenko@khai.edu

A reliable prediction of thermal and hydraulic processes in a compact bearing chamber plays a key role in its efficient design to minimize power consumption for lubricating, thermal protection, and pressurization. The task complexity is defined by the high intensity of transfer processes in three-dimensional multiphase flow of variable structure and the processes significant dependence on the engine operating mode. Therefore, a combination of simulation methods and experimental studies is crucial for a better understanding of the heat transfer and flow distribution phenomena in the bearing chamber.

Bearing chamber of a gas turbine engine is filled with a mixture of supplied lubricating oil and secondary air that leaks through the seals. The sources of oil droplets in the multi-phase flow core with a low volume fraction of liquid are the bearing and the shaft. The oil droplets motion to the chamber wall is caused by their interaction with a swirling airflow. When oil droplets get to the walls of the bearing chamber, they form an oil film. Due to the partial reflection of drops and splashing of the film, the flow structure at its surface is very complex. The film moves under the influence of shear forces, gravity, and viscosity, as well as under the influence of droplets deposition. As a result, the thickness of the oil film is non-uniform along the bearing chamber wall.

Data on heat transfer in the bearing chamber are the most important for engineering applications . The heat transfer coefficient calculated on the basis of the classical Newton-Richman equation is widely used to represent them. However, this approach is only formally applicable for a two-phase medium. Also, choosing of the flow core temperature is an ambiguous issue. At the same time, this approach is useful for analyzing the thermal resistance of heat transfer and its structure. These issues are addressed in this study.

Heat transfer from the flow core to the boundary of the oil film is carried out by adjacent air and precipitating droplets. The CFD methods application in combination with an analysis of the integral contribution of individual interfacial effects showed that the droplets deposition plays a decisive role in this process. Such a mechanism significantly intensifies heat transfer, and therefore the main contribution to the thermal resistance of internal heat transfer is made by the oil film. This study considers the issues of the oil film modeling with account for the factors determined by the engine operating mode as well as the possibility of applying the methods of thermohydraulic analogy for the oil film thermal resistance determination. Based on the obtained results, the study presents practical recommendations for reliable processes modelling in the bearing chamber.

The research leading to these results has been performed in the frame of the “Advanced Modelling Methodology for Bearing Chamber in Hot Environment (AMBEC)” project. This project has received funding from the Clean Sky 2 Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 785493”.

Key words: gas turbine engine, bearing chamber, heat transfer, thermal resistance, multiphase flow, oil film.