Turbofan Engine Testing Oil Collection System Re-Design

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Grist, Blake
Liang, Tony
Nixon, Adam
Psooy, Erik
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Standard Aero, one of the world’s largest independent providers of maintenance, repair, and overhaul (MRO) services, has provided service for two configurations of the CF34 engine: the CF34-8C, and CF34-E. The CF34 engine was commercially developed by General Electric. Bombardier and Embraer have used this engine on select models of their regional aircraft. The goal of this project was to re-design the oil collection system for Standard Aero’s testing of the CF-34 turbofan engine. The oil collection system connects to the high-pressure drain line, where it is intended to collect oil from the engine’s bearing sumps while the engine is in operation in the test cell. The amount of oil leakage in volume and rate is required for Standard Aero to certify their repaired engines as airworthy. The existing oil collection for this drain line consisted of a drain mast made of stainless steel tubing connecting to a plastic bottle. This plastic bottle was intended to capture all oil as it exits the engine. However, since the bottle is subjected to the high-pressure air-oil mixture, holes were drilled through the top to relieve pressure build-up. These holes prevent the bottle from becoming dislodged during testing. As a consequence of these holes, the air-oil mixture escapes the bottle, which means that oil leakage volume rate cannot be accurately captured or measured while the engines are undergoing testing. Standard Aero asked Team 22 with re-designing the oil collection system. Design needs were identified and built upon to develop a list of target specifications for which their importance could be ranked. Where applicable, the target specifications were given a quantifiable metric. The list of specifications served as a means to evaluate the final design’s ability to meet the client's needs. With consultation of the client and through site visits, Team 22 identified some design constraints and limitations. Given the design needs, constraints, and limitations, the group was able to establish a scope for the design project. Team 22 completed a concept generation phase of the project in which the oil collection system was broken down into several components. The components were the drain mast, air-oil separation, oil collection, and flow regulation. A weighted decision matrix was applied to each component section to evaluate each concept for that particular component section. The selected novel oil collection system was the combination of the best components determined through the weighted decision matrix. The final conceptual design included a cyclone air-oil separator which separated air from the oil via centrifugal motion, forcing the oil to the walls of the device as the air swirls inside. Standard Aero expressed interest in sourcing and adapting existing products that could be incorporated into the current system. For ease of use and quick design implementation, the client also expressed interest in retaining as much of the current system as possible. The Mishimoto Carbon Fiber Baffled Oil Catch Can was determined to be the best commercially available air-oil separator. Team 22 designed the necessary modifications and sourced parts required to mate the catch can to the current drain mast system.
Mechanical Engineering