Infrared absorption spectroscopy: The absorptance of low molecular weight paraffin hydrocarbons and the development of a device for measuring time resolved molecular species concentrations

Infrared absorption spectroscopy is a powerful diagnostic tool that has important applications in the field of combustion. One area in which it is particularly useful is the measurement of radiative transfer parameters that are used in combustion modeling or in the calibration of infrared measurement systems. A related application is its use as a measurement tool where species identification and quantitative concentrations can be determined through use of a properly calibrated system. These applications were the focus of this dissertation.; The spectral absorptance of methane, ethane, propane, and butane were measured using an FTIR spectrometer over a range of temperatures from 296--900 K. The absorptance of the 3.3 mum band was integrated to give total absorptance and empirical correlations were developed to express this quantity as a function of temperature and concentration. These measurements have important applications in fire modeling where blockage of thermal radiation by fuel gases can effect the burning rates of large fires.; An instrument called Fast-Spec was developed with the capability of making time resolved concentration measurements of molecular species. While there are several potential applications for such an instrument, it was developed here by measuring unburned hydrocarbon and carbon monoxide concentrations in the exhaust stream of an internal combustion engine. Time resolution was on the order of 1 ms. Good agreement was seen in the hydrocarbon measurements with time averaged values obtained with a Flame Ionization Detector (FID). Results from the CO measurements demonstrated, however, that several modifications still need to be made.