Soot characteristics in laminar co-flow ethylene flames under reactant preheating conditions

Flame temperature has a significant effect on the sooting propensities of a fuel burning in a diffusion flame. Preheating technology is commonly used to reduce emissions and increase efficiency in combustion devices. This study aims to investigate the effects of increasing reactant preheating temperature on different sooting parameters, including soot temperature, concentration and maturity in laminar diffusion flames. This was achieved by an optical setup capable of coupling emission and extinction measurements, for i n - s i t u evaluation of these parameters. Measurements were conducted for multiple wavelengths, extending into the near-infrared (NIR) spectrum to circumvent the wavelength dependence of the soot absorption function, E ( m ) . Two-dimensional distributions of flame temperature, soot volume fraction and soot maturity were calculated and compared for different cases of reactants at ambient and elevated reactant temperatures. The distribution of the maturity of soot present in the flame was correlated with the quantification of the spectral dependence of the soot absorption function, as non-mature soot exhibits a strong spectral dependence, which decreases with increasing maturation. The soot maturity level was observed to change with the preheating temperature, with the maximum effects observed at the wings and the nascent soot region. Using this spectral dependence, absolute E ( m ) distributions were determined at each wavelength. Lastly, corrected soot concentration and temperature distributions were calculated and compared quantitatively as well as qualitatively. • Effects of reactant preheating on soot evolution in laminar non-smoking co-flow flames. • State-of-the-art optical setup combining light extinction and soot emission measurements. • Quantification of soot absorption function E ( m ) and changes due to preheating. • Corrected soot volume fraction, temperature incorporating maturation effects. • Improved insights into temperature errors and guidance for modeling preheated flames.