Full-Scale Testing Of A Passively Modulated Oil-To-Air Cooler

Advanced gas turbine engines need efficient and effective thermal management systems to increase performance and service life. One thermal management system used in gas turbine engines is the lubrication system cooler or oil cooler. The lubrication system provides the necessary lubrication to components and removes the heat generated by them. Currently used lubrication systems must be designed to the worst thermal condition, ground idle, resulting in overcooling the lubricating oil across the remainder of the flight envelope. Overcooling the oil lowers the component’s efficiency, reducing performance and increasing the wear, lowering the component’s life span. The lubrication system cooler uses heat exchangers placed in the bypass flow stream, using the bypass air as a heat sink. This leads to unwanted flow structures and total pressure losses within the bypass, increasing the thrust-specific fuel consumption. There exists an opportunity to improve the performance of the cooler system by modulating its heat rejection to match the thermal load being generated by the gas turbine engine. Implementing smart materials into this system would allow autonomous, passive, and lightweight modulation of the oil cooling system. Using smart material actuators to control the cooler’s heat exchanger air intake based on a target oil temperature range will reduce the total pressure losses and keep the oil in a more optimum temperature range. This thesis intends to empirically prove and investigate this hypothesis through full-scale testing of a smart material-actuated Advanced Air Oil Cooler (AAOC). For testing a multidisciplinary test article was constructed with 3 smart material-actuated coolers operating in series. The test article was then wind tunnel tested to a variety of flight conditions. The results of full-scale testing proved the feasibility of a smart material-integrated thermal management system. The AAOCs were shown to independently modulate augmenting the cooling systems heat rejection, and the behaviors shown in the bench scale testing were validated. The unknown unknowns with a smart material-integrated thermal management system were also identified, aiding in its future implementation.