Quantitative acetylene measurements in laminar and turbulent flames using 1D Raman/Rayleigh scattering

This work presents the extension of the established detection of seven major species in 1D Raman/Rayleigh measurements to incorporate acetylene (C₂H₂) as an eighth species. Acetylene is an important soot precursor which is generated in hydrocarbon flames as an intermediate species following decomposition. It occurs over a broad temperature range in flames and has been identified as a potentially detectable species in 1D Raman/Rayleigh measurements. In this paper, we discuss the Raman spectral signature of acetylene, its temperature dependence, calibration procedures, and the interference with other Raman-active species, C₂ and broadband interferences, all of which are essential to quantify for accurate data processing. In this regard, Raman measurements in laminar and turbulent dimethyl ether flames were acquired. The data are spectrally analyzed and low-temperature calibrations of the Raman response are combined with an extrapolation model for high temperatures in order to place the acetylene signals on an absolute scale. Single-shot and conditional-mean values are presented as a function of mixture fraction for a laminar partially-premixed DME/air flame. Measurements from the laminar flame are compared to a 1D laminar flame calculation to assess the accuracy of the calibration and analysis procedures. Finally, detection limits, signal-to-noise, and signal-to-interference ratio of the C₂H₂ measurement are discussed, and single-shot measurements of acetylene in a turbulent DME/air jet flame are demonstrated.