Plasma Combined Mass-Flux and Gas Species Sensor For Hypersonic Combustion Monitoring

Naval Surface Warfare Center, Crane Division is interested in receiving proposals for research aimed at the development of a sensor that utilizes a small contained amount of ionized gas to simultaneously measure mass-flux and gas species in high-speed, high-enthalpy flows that are endemic of hypersonic flight and SCRAM-jet propulsion. The sensor is based on the optical emission properties of a stable glow discharge or plasma. The use of the plasma sensor for mass-flux measurements has already been demonstrated1. It incorporates a high frequency (1MHz) AC discharge to ionize the gas between two closely spaced electrodes. The voltage drop across the discharge correlates with the time-dependent mass-flux, ρU. With an alternate design, the plasma sensor can also be used to measure static pressure. Recent experiments have examined the use of the plasma sensor for spectral analysis of the optical emission produced by the glow discharge. Results for combustion in both Ethylene and Propane indicate that the plasma sensor produces useful emission lines that can be used to measure temperature, density and possibly gas species. Utilizing the other attributes of the plasma sensor, these optical emission measurements could be performed simultaneously with mass-flux and/or pressure in a combined sensor suite. The proposed research seeks to further develop this capability.