N2/O2/H2 dual-pump cars: validation experiments

The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) method is used to measure temperature and the relative species densities of N₂, O₂ and H₂ in two experiments. Average values and root-mean-square (RMS) deviations are determined. Mean temperature measurements in a furnace containing air between 300 and 1800 K agreed with thermocouple measurements within 26 K on average, while mean mole fractions agree to within 1.6% of the expected value. The temperature measurement standard deviation averaged 64 K while the standard deviation of the species mole fractions averaged 7.8% for O₂ and 3.8% for N₂, based on 200 single-shot measurements. Measurements have been performed in a hydrogen-air flat-flame burner for fuel-lean and fuel-rich conditions. A preliminary comparison is shown between the fitted data and an adiabatic, equilibrium computation. For fuel-lean conditions, good agreement was found for temperature. Temperatures measured under fuel-rich conditions were about 50 K higher than the computation. Mole-fractions for N₂ agreed with the computation to within 3%. Measured O₂ mole fractions were systematically high while measured H₂ mole fractions were systematically low by 10-15% compared to the computation. For an equivalence ratio of 2.8, the standard deviation of 58 single-shot temperature measurements was 108 K, or 5.8%, and the standard deviations of H₂ and N₂ mole fractions were 9.8% and 3.8% of the measured values, respectively.