This project develops the necessary tools and methods to measure H 2O absorption spectra in harsh environments, and calculate temperature and mole fraction from the measured spectra. Various wavelength-agile sources are designed to obtain absorption spectra. The best performing wavelength-agile laser source for H2O measurements to date is the Fourier-Domain Mode-Locking laser. Specific procedures are highlighted to best accommodate the measurements in the presence of beam steering and thermal emission. A robust method to calculate temperature and absorber mole fraction is also developed.
Measurements were taken to quantify accuracy in a shock tube and steady burner (used to stimulate gas turbine conditions). Results from HCCI engine measurements demonstrated the precision of the measurements. Temperature results greater than 1000 K have been shown to be biased low. This is a major concern since the main function of the sensor is high temperature combustion studies. Preliminary studies indicate that using a better database for reference spectra should improve these high temperature results.