SOOT FORMATION IN PREMIXED HYDROCARBON FLAMES - PREDICTION OF TEMPERATURE AND PRESSURE-DEPENDENCE

Premixed sooting burner stabilized ethene-air flames at pressures from 0.1 to 1.0 MPa that have been investigated experimentally by Wagner et al. have been simulated numerically. The numerical calculations have been performed on the basis of the conservation equations for that system including a detailed chemical model for soot formation. The maximum temperatures in the flames have been varied in the experiments by changing the flow rates of the feed. In accordance with the experimental data the numerical calculations predict a bell shaped dependence of the final soot volume fraction on the maximum flame temperature. A sensitivity analysis of the final soot volume fraction with respect to the rate coefficients of the different reactions identifies the classes of reactions that are most important for soot formation. These are ''pre-soot'' gas phase reactions. The dependence of the final soot volume fraction on pressure is calculated to be proportional to p(2) at 0.1 MPa and proportional to p(1) at 1 MPa. This is in accordance with the experiments of Wagner et al. The agreement between predictions and experimental results is reasonable. Important phenomena connected with the formation of soot in premixed hydrocarbon flames are reproduced in the framework of the employed model. A further validation of the model, in particular through the investigation of the reaction rates of the involved elementary steps and their pressure dependence should corroborate the qualitative dependence predicted by the model as it stands now.