Heat transfer analysis of AEDC test cell J-2 inlet ducting using a lumped-parameter mathematical model

In order to stay competitive in the modem business world, Arnold Engineering Development Center (AEDC) has become more committed than ever to improve efficiency and decrease the costs of aeropropulsion testing. One of the major drawbacks to efficient testing in several air-breathing test cells at AEDC is long time delays in transitioning inlet temperature. Due to the long runs of ducting, and their large metal masses, a great deal of heat transfer is allowed to take place between the conditioned process air inside the ducting, and the ambient environment outside the ducting. One of the best examples of this process is in the Engine Test Facility (ETF) large aeropropulsion test cell, J-2. Test observations have determined that when cooling to a lower temperature, the test section inlet temperature can generally only be varied on the order of one to two degrees Fahrenheit per minute. This thesis discusses this phenomena and the development of a SIMULINK® lumped-parameter mathematical model to predict and quantify the thermal losses of J-2's. inlet ducting. The model was calibrated and verified against data collected from both the ETF and Aeropropulsion Systems Test Facility (ASTF). In general, the model was shown to predict time-varying temperatures to within 5° of the recorded facility data. The model was then used to compare the results of four possible facility modifications to J-2's current configuration. Temperature transition times for J-2's current configuration were compared to the calculated transition time after: (1) augmenting the existing outer-duct insulation; (2) insulating the duct's inner diameter; (3) increasing the airflow through the venturi bulkhead, and; (4) removing the venturi bulkhead from the inlet ducting. Removing the (non-functional) venturi bulkhead from the inlet airflow ducting was determined to have the greatest impact on improving the temperature transition time in J-2.