Experimental Investigation of Engine Bypass Flow Behavior in the Presence of Surface Heat Exchangers

Ongoing engine developments require advanced thermal management technologies to handle the increasing demand of refrigeration and lubrication. As the thermal capacity of the oil lubricant and coolant circuits becomes saturated, cooling sources in addition to the conventional fuel based oil cooling systems are essential for the engine operation. This research is focused in the experimental investigation of the turbofan bypass flow behavior in the presence of finned heat exchangers oriented with the mean flow direction. Engine testing methods alternative to flight testing were developed for this purpose. A new test facility reproducing the engine bypass flow at cruise velocities and take off atmospheric conditions was built to study the flow phenomena. Different measurement techniques were adapted to the requirements of the flow and wind tunnel characteristics. Particular attention was dedicated to the development of a multi-hole probe and a data reduction methodology providing accurate results in a wide angular range at transonic conditions. The flow development along the bypass channel flow was characterized in the presence of different heat exchanger geometries, and compared to the flow development in the absence of heat exchangers.