Scavenge Flow in a Bearing Chamber With Tangential Sump Off-Take

A tangential sump design is employed in several aero-engines mainly due to its simplicity and compactness. However various problems have prompted investigations of the sump design. An experimental program at Purdue University (Chandra, 2006, "Flows in Turbine Engine Oil Sumps," Ph.D. thesis, School of Aeronautics and Astronautics, Purdue University and Radocaj, 2001, "Experimental Characterization of a Simple Gas Turbine Engine Sump Geometry," M.S. thesis, School of Aeronautics and Astronautics, Purdue University) was conducted to investigate the characteristics of a tangential sump design like one used in the AE3007 aero-engine. The research employed a transparent chamber to allow unprecedented view of the flow inside the bearing chamber. It was quickly found that a persistent liquid pooling near the drain entrance of a tangential sump obstructs the outflow to the scavenge pump. The air flow near the drain entrance has been shown to have strong reverse flow, even with, or perhaps due to, substantial over-scavenging. Various modifications were tested with varying degrees of success. The work highlights limitations of a tangential sump design. Based on the lessons learned, a new sump design was proposed. Preliminary test of the new sump design has shown positive results.