| Abstract |
This work investigates both experimentally and numerically turbulent diffusion flames in a laboratory combustor with a slot burner. Experiments were carried out using a mixture of natural gas (75 vol.\%) and hydrogen (25 vol.\%) as fuel and three oxidizers with compositions of 35\% O-2/65\% N-2, 35\% O-2/32.5\% N2/32.5\% CO2 and 35\% O-2/20\% N-2/45\% CO2. For these three oxidizers, hydroxyl radical chemiluminescence (OH/) imaging and spatial distributions of temperature and of O-2, CO2, CO and NOx concentrations are reported, which enabled to identify the location and structure of the reaction zone. The regions of highest temperatures coincided with the regions where the OH/intensity was maximum. Moreover, the addition of CO2 to the oxidizer forced the reaction to take place further downstream, lowered the OH/intensity and suppressed the NO formation. On the modeling side, numerical simulations were carried out using the ANSYS Fluent 15.0 commercial code. Turbulence was modeled using the k-epsilon realizable model. The eddy dissipation concept was employed along with a chemical mechanism comprising 42 transported species and 167 chemical reactions. The model was able to satisfactorily predict the temperature and the concentrations of O-2 and CO2, but discrepancies were found in the prediction of the CO concentration. (C) 2016 Elsevier Ltd. All rights reserved. |
