Flow Control and Thermal Behavior of Bearings Using a Proportional Valve in a Closed-Loop Lubrication System for Turbofan Engines
Yasin Ince* and Ilhan Kocaarslan
ABSTRACT
Effective lubrication and thermal management have become extremely important in modern turbofan engines, under extreme temperatures and high rotational speeds. The bearings in both the cold and hot sections of these engines are subjected to considerable thermal and mechanical stresses and require credible lubrication to reduce wear and avoid early failures [1,2]. Indeed, closed-loop lubrication has become the de facto industry norm in aero-engine designs as it efficiently re-circulates oil, controls heat, and removes contaminants [3]. However, the biggest engineering challenge still lies in the proper optimization of oil distribution, especially across regions where there is a difference in thermal load [4].
Fixed or manually adjusted components have always been a part of the traditional lubrication system. They do not adequately respond to the dynamic conditions of the engine with varying RPM and sudden thermal excursions during operation [5]. New-age systems try to overcome this limitation by adding active flow control devices like proportional valves that control oil delivery to important parts of the system in real-time [6]. These valves offer very precise control of oil flow, ensuring that the bearing temperatures are kept safe, which ultimately improves the durability of the engine and its operational reliability [7].
The study is directed towards the incorporation of oil flow regulation using proportional valves into a closed-loop lubrication system of a small turbofan engine, rated for approximately 4000 N of thrust . The research investigates two most vital bearings in the engine - one in the cold sector and the other in the hot sector. The bearings thermally responds appropriately to oil distribution changes under different flow scenarios. Moreover, the work contributes to the overall advancement in the aerospace arena in thermal management by showing how adaptive lubrication control could elevate efficiency and safety [8-10].
