Date of Award
Master of Science in Aeronautical Engineering
Department of Aeronautics and Astronautics
Paul I. King, PhD
Shock tubes utilize a difference in pressures between gases separated by a diaphragm to create a shock wave when the diaphragm ruptures. By using sensors of known spacing, the speed of the wave can be determined. The AFIT 2-inch shock tube was reassembled and tested to ensure proper and safe operation. A high-speed data acquisition system was configured to take data at 2 MS/s. This research showed that the Mach number of the shock waves produced in this shock tube fall within 7% of theoretical values at speeds under Mach 3 and within 9% at higher speeds. The peak velocity of each shock wave was shown to occur at approximately 3 meters from the diaphragm. The second portion of the research focused on the testing of sensors used to evaluate the performance of the pulse detonation engine (PDE) for research and developmental purposes. The high temperatures of the PDE are too harsh for unaltered dynamic pressure transducers to provide accurate pressure measurements. Therefore, two alternatives were developed: coat the sensors with a 0.6 mm thick insulating silicone that protects them from the heat and detect the waves by detecting ions in the combustion inside the PDE tubes with spark plugs instead of measuring pressure. However, neither the effect of putting this coating on the sensors nor the sensitivity of the spark plug as an ion sensor were known. This researched proved that no degradation in response time, rise time, or sensitivity results from coating the pressure transducers with silicone. The research also found that the ion sensors are unable to consistently detect ions created by a Mach 8 shock wave through air suggesting that ions detected in the PDE most likely result from combustion only.
DTIC Accession Number
McMillan, Robert J., "Shock Tube Investigation of Pressure and Ion Sensors Used in Pulse Detonation Engine Research" (2004). Theses and Dissertations. 3915.