Oil Autonomy of a Turbojet

Abstract: The oil circuit of a jet engine is required to lubricate and cool mechanical parts. The oil is pumped from the oil tank and flows through heat exchangers. Then it is injected on the bearings for lubrication and cooling, before being scavenged at the bottom of the sumps and finally flows back to the oil tank. During flight, the volume of oil inside the tank fluctuates depending on many parameters like the engine rotation speed and the oil temperature to name but a few. The flow inside the sumps is diphasic with oil and air mixing up. The physical phenomena taking place in the oil circuit are complex and understanding them is essential to size an oil circuit for a new engine design. Mass is a critical factor in aviation and being able to design accordingly an oil circuit is a valuable asset.This work focuses on improving a 1D model predicting the evolution of the oil level in the tank. The model relies on the geometry of the engine, the architecture of the oil circuit and real flight data provided by the airline companies. This data contains flight parameters such as engine rotation speed, oil temperature and pressure. The prediction is then compared with the real volume of oil in the tank measured during the flight. The model is compared to experimental data to access its accuracy. Finally, the model is adapted to three different engines produces by Safran to test its robustness to geometry changes.