Advanced Diagnostics for Detonation-Powered Vehicles

Pulsed detonation engines (PDE) have the potential to operate with higher efficiency and lower operating costs than scramjets and turbines.  Initiating and sustaining detonation in a controlled, repeatable manner is difficult, at present, and requires optimization of a number of parameters.  Key issues include the need for rapid fuel injection and fast mixing of fuel and oxidizer.  Successful PDE development requires new diagnostics capable of rapid measurements of the concentrations and distributions of combustion species and products, as well as reaction temperatures.  Optical diagnostics are preferred because they are non-intrusive.  Southwest Sciences proposes the development of a high-speed (≥10 kHz) optical absorption diagnostic for detonation-powered vehicles.  At the end of Phase II, we will deliver to the Air Force a prototype instrument capable of measuring the line-of-sight concentrations of at least three key combustion species such as water vapor, carbon dioxide, methane, and oxygen with time resolution of 1 ms, or better.  The proposed approach builds on our recent successful work that achieved true frequency modulation spectroscopy at GHz bandwidths.  We plan now to develop a variation of frequency modulation spectroscopy called high-speed, two-tone frequency modulation spectroscopy that simplifies the signal processing requirements while maintaining fast time response.   BENEFIT: We propose an enabling technology that will help with the development of pulsed detonation engines.  These engines have the potential to be more energy efficient than do existing propulsion designs.