| Sensor systems based on room-temperature diode lasers and high-resolution absorption spectroscopy techniques are advantageous because they allow for fast and absolute measurements of species mole fractions. In addition, novel external cavity diode lasers (ECDL) provide large and continuous wavelength tuning ranges that are ideal for spectroscopic studies.;InGaAsP and extended InGaAsP ECDL emitting near 1.5 and 2.0 mum, respectively, were used to measure absorption spectra of CO (3nu band) and CO2 (2nu1 + 2nu2 + nu3, 4nu2 + nu3, nu1 + 2nu2 + nu3, and 2nu1 + nu3 bands) to obtain accurate values of spectroscopic parameters and to verify relevant databases. Comparisons to recorded H2O spectra enabled the identification of relatively strong and isolated CO and CO 2 transitions for unambiguous species detection. These transitions formed the basis of diode laser sensors for measurements of CO and CO2 mole fractions in exhaust gases using extraction-sampling techniques and for non-intrusive measurements of CO2 in high-temperature combustion environments.;The first sensor system was applied to measure species mole fractions in the burned gases of a premixed CH4-air flame. The measurements showed good agreement of total carbon yield with calculated equilibrium values (to within 4%). Measured CO mole fractions were slightly lower and measured CO2 mole fractions were slightly higher than calculated equilibrium values for fuel-rich conditions, indicating partial conversion of CO to CO2 in the gas-sampling system. The sensor system achieved a noise equivalent absorbance of 1.6 x 10-5 (200-Hz noise bandwidth) corresponding to minimum detectivities of 10 ppm CO (1.5 mum), 7 ppm CO2 (1.5 mum), and 0.1 ppm CO2 (2.0 mum).;The second diode laser sensor was applied to determine CO2 mole fractions in the burned gas region of a premixed C2H 4-air flat-flame burner operating at fuel-lean conditions. Measured CO2 mole fractions agreed, on average, to within 2% with calculated equilibrium values. The minimum CO2 detectivity was 200 ppm-m ppm-m (1530 K, 200-Hz detection bandwidth). |
