NO formation in premixed flames of C1–C3 alkanes and alcohols

The influence of alkane and alcohol molecular structures on nitric oxide (NO) pollutant formation trends is investigated through the study of C1–C3 alkanes and alcohols in premixed stagnation flames at atmospheric pressure. The flame diagnostics consist of one-dimensional (1-D) Planar Laser-Induced Fluorescence (PLIF) for measurements of NO and CH concentrations, 1-D NO-LIF thermometry, and 1-D Particle Tracking Velocimetry (PTV) for the determination of flame reactivity and burning rates. The results show that alcohols produce less NO than their alkane equivalents. This behaviour is linked to the lower flame temperatures of alcohol flames and the tendency of alcohols to produce lower concentrations of the CH radical, due to inhibition of the formation of methyl groups. These trends are captured in the available thermochemical models; however, there are discrepancies regarding the formation pathways of NO and its intermediates which are linked to variability in model rate coefficients. Further adjustments to all of the thermochemical models are needed to accurately capture the nature of NOx pollutant formation in premixed alkane and alcohol flames, and this experimental study provides target data for this effort.