Determination of temperatures and fuel/air ratios in an ethene–air flame by dual‐pump CARS

The simultaneous determination of temperature and ethene, oxygen and nitrogen concentrations is demonstrated using the dual‐pump coherent anti‐Stokes Raman spectroscopy (CARS) technique. Temperature and relative N2/O2 concentrations were calculated from contour fitting against theoretically calculated spectra, while relative N2/C2H4 concentrations were obtained from the integrated intensity ratio, calibrated in a heated gas cell. Detailed measurements were performed in a partially premixed ethene–air co‐flowing jet flame established on a slot burner. As the two vibrational Raman modes ν2 (1623 cm−1) and ν3 (1342 cm−1) of ethene are in close vicinity of the oxygen Raman transition at 1556 cm−1, either the ν2 or the ν3 transition can be excited together with O2 using a single narrowband–broadband laser combination. Both possibilities are discussed. Additionally, nitrogen is probed for thermometry with the same broadband laser but another narrowband laser in a dual‐pump CARS approach.