High-Resolution Spectroscopic Measurement of Small Molecules in Combustion

Spectrometers, both interferometric and dispersive, are a useful tool for measuring high-resolution spectra in combustion. The method of spectral acquisition depends on the wavelength region of interest, required speed of the measurement and available light sources.;A novel method which uses a Fourier-Transform Infrared Spectrometer to measure dynamic processes is presented. This method is used to measure time-resolved emission spectra of H2O, CO2, hydrocarbon fuels, and various aldehyde-like molecules in an internal combustion engine. Gas properties are inferred from the measured spectra. A variation of the method is used to measure time-resolved absorption spectra in a reciprocating engine. The resulting spectra are used to determine gas temperatures and mole fractions of H2O and fuel.;Ultraviolet absorption spectra of the hydroxyl radical in various H 2/Air and CH4/Air diffusion flames are measured using a Czerny-Turner grating spectrometer. Gas temperatures are inferred from the spectra. Temperature measurements at 31.25 kHz are demonstrated using a high-speed version of the instrument.