In a jet engine air and oil are mixed during removal from the bearing chamber. Before the oil can be recycled back into the system it must be separated from the air. This is accomplished through use of a de-aerator and breather. The oil air mixture enters the de-aerator first. The de-aerator is a vertical cylinder in which the air and oil enter from the top of the system. Gravity then pulls the oil down as it circulates along the outer wall of the de-aerator. The air is forced out through a top hole and sent to the breather where any oil droplets which remain are furthered separated. A pedestal is located near the bottom of the de-aerator. The pedestal creates a gap between itself and the de-aerator wall. Ideally this gap should be large enough to allow oil to flow through the gap without pooling on the pedestal, but small enough so that air does not flow through the gap. The oil will pool up on the pedestal and reduce the efficiency of the system. In this research, a 30° conical pedestal with a gap of 10.7% was tested. The results showed that the pedestal gap of 10.7% is too large and allows air to flow through the gap. The maximum water was 8.5% and the average water thickness was 5.11%. After studying both the previous experimental data and current CFD data, it is recommended further testing be conducted on pedestal gaps between 8.5% and 9.5%. / Master of Science / In jet engines, the turbine provides power and thrust to the aircraft by spinning at high speeds. This spin is created through the expansions of the hot gases leaving the combustion chamber. To prevent the degradation of turbine it spins on lubricated ball bearings. However, the oil which lubricates these ball bearings increases in temperature due to its proximity to the turbine. To prevent the oil from deteriorating it must be recycled from the ball bearings allowing the oil to cool. In process of recycling the oil, air is also pulled out of the system. Before the oil can be reinserted to the ball bearings it must first be separated from the air. This is accomplished in the de-aerator. In the de-aerator the oil and air mixture enter the side of a long cylinder. The oil flows down the side of this cylinder and out vents at the base. The air flows out vents at the top of the cylinder. Towards the base of the de-aerator is a pedestal, which creates a gap between itself and the wall. This gap should create a seal between the oil and the air, so that air does not flow through the gap and oil does not pool on top of the pedestal. Using CFD (Computational Fluid Dynamics), a software which simulates fluid flow, it was determined that pedestal gap should be between 8.5% and 9.5% of the radius of the de-aerator.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/73386 |
| Date | 07 November 2016 |
| Creators | Hehir, Ryan Thomas |
| Contributors | Mechanical Engineering, Ekkad, Srinath V., Morvan, Herve P., Vick, Brian L. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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