A two-wavelength ethylene-absorption temperature diagnostic

Recent high-temperature absorption cross-section measurements of ethylene have revealed spectral features with strong sensitivity to temperature. Motivated by these observations, this work presents a novel two-wavelength laser absorption diagnostic for inferring temperature from the ethylene spectrum. Two CO2 gas laser wavelengths, 10.532 mu m and 10.591 mu m, were systematically chosen for their cross-section strengths and the temperature sensitivity of their absorbance ratio. Cross-sections at each wavelength and absorbance ratio measurements were collected over conditions 418-1671K, 0.3-4.3 atm in a shock tube. The absorbance ratio was found to be insensitive to pressure between 1.1 atm and 4.3 atm, and a correlation was developed to describe the ratio as a function of temperature. At lower pressures, the correlation incorporates an additional pressure factor. The diagnostic was used to study the shock tube pyrolysis of ethane at 1330K and 2.2 atm, and further applications are suggested.