Infrared Hyperspectral Imaging Diagnostics of Fueling Strategy for Scramjets

摘要

A novel diagnostic technique was applied to an ethylene-fueled supersonic combustion ramjet cavity to measure fuel scalar values, as a function of fueling strategy, before ignition. Imaging Fourier-transform absorption spectroscopy was employed to measure fuel concentration, temperature, and plume structure in the cavity and core supersonic flow. Additionally, a Fourier-transform infrared spectrometer measured fuel concentration through extractive sampling from the base of the cavity as a point of validation. Two different fuel-injection locations were used and a range of fuel flow rates were investigated. Both diagnostic techniques showed similar trends in fuel concentrations within the cavity as a function of both fuel-injection flow rate and location. Furthermore, the unique combination of full spectral content and imaging of the imaging Fourier-transform infrared spectroscopy allowed for fuel mole fraction and temperature estimates to be attained throughout the flowfield. Temperature maps indicated a strong sensitivity of cavity temperature on fueling strategy.