Simultaneous N(2), CO, and H(2) multiplex CARS measurements in combustion environments using a single dye laser

A method for accurately inferring temperatures and concentrations from simultaneous multiplex CARS spectra of N(2), CO, and H(2) is introduced. Only a single dye laser is employed in these measurements. Temperatures inferred from the nitrogen portion of spectra taken in a furnace of preanalyzed samples of these gases show agreement with temperatures measured by thermocouple to well within the estimated accuracies of the thermocouple (1%). Carbon monoxide and hydrogen concentrations may be inferred from the remainder of the spectrum with accuracies of 2 and 1/2%, respectively. Spectra taken downstream from a combustor burning diesel fuel and preheated air indicated that simultaneous measurements of temperature and CO concentration with mole fractions from below 0.01 may be made in turbulent reacting flows. The S(9) rotational line of hydrogen is employed to infer concentrations of H(2). Minimum detectable mole fractions of hydrogen are presented as functions of temperature and CO mole fraction. The effects of temporal instabilities of the dye laser and interspecies coupling during analysis on the accuracy of the inferred values are discussed.