Thermal effect and oxygen-enriched effect of N2O decomposition on soot formation in ethylene diffusion flames

Abstract

This study experimentally investigated the effect of nitrous oxide (N2O) decomposition on soot formation in N2O/ethylene diffusion flames. The effect of N2O decomposition on the soot formation mechanism was examined in three oxidation cases (Cases Case I–III). In Case I, N2O was used as the oxidant; in Case II, an oxygen-enriched N2/O2 mixture (67 % N2 + 33 % O2) was used as the oxidant; and in Case III, standard air (79 % N2 + 21 % O2) was used as the oxidant. A triple-port burner was used to generate diffusion flames with various R (ratio of the oxidizer flow velocity to the fuel flow velocity) values (R = 0–6). The soot concentration was measured through laser-induced incandescence, and the soot temperature was determined using two-color pyrometry. The measured soot temperatures increased significantly due to the thermal effect in the upstream position of the N2O/C2H4 flames. The oxygen-enrichment effect on soot formation increased gradually from 10 % to 60 % as R increased from 0.5 to 6. The integration of the soot concentration along the flame length revealed that the soot formation rate and soot oxidation rate might rebalance under the N2O decomposition effect.