The effect of ammonia on soot formation in ethylene diffusion flames

This paper originally investigates the effect of NH 3 dilution on soot formation when NH 3 is gradually added into the fuel stream in an ethylene laminar diffusion flame stabilized on a Santoro burner. The variations of flame diameter and two flame heights, i.e., mixture-strength flame height and visible flame height are carefully documented and analyzed. Moreover, local soot volume fraction (SVF) and soot temperature fields are simultaneously measured by compact-modulated absorption and emission technique, and the corresponding measurement random errors are also provided by the error propagation calculations for the first time. All the reported measurement random errors of SVF and soot temperature fields are estimated within the range of ±0.07–±0.08 ppm and ±40–±91 K, respectively. As an original database, the concomitantly measured SVF and soot temperature distributions are provided as high-fidelity datasets for refining soot formation model that is overrode by NH 3 . In addition, the flame cross-section average SVF F soot ( z ) is calculated for every NH 3 diluted flame, and the relative contributions of NH 3 dilution and chemical effect are quantitatively assessed in terms of F max − X NH 3 plotting. It is found that when X NH 3 < 30 % , the chemical effect of ammonia is about twice that of the dilution effect. While X NH 3 > 30 % , the chemical effect and dilution effect of ammonia are gradually equal. Eventually, through modeling of the soot formation rate V in the flames, the relative contributions of chemical effect, dilution effect and thermal effect of NH 3 are further novelty discriminated within the X NH 3 from 0 to 46% and it is shown that NH 3 chemical effect plays the dominate role in soot suppression, then the dilution effect and the thermal one at the least.