Axial Dispersion Modeling of Laminar Flames

The reduction of nitrogen oxides (NOx) emissions from an existing burner is a a challenging task requiring the understanding of interactions between burner geometry and flame aerodynamics. Currently, three approaches for NOx control exist: fuel or flue gas treatment and combustion modifications. Low NOx burner design is economically attractive for natural gas and light fuel oil combustion since very low NOx emissions are achievable without the requirement for expensive equipment such as needed for post combustion reduction techniques. This paper deals with the laminar flame modeling through the axial dispersion approach, using the Residence Time Distribution (RTD) analysis. Some small quantity of inert tracer gas is injected upstream the combustor chamber. Downstream, the fluid rich in tracer passes through the detection point, where a mass spectrometer is used to quantitatively measure the tracer’s concentration. Then, the analysis of the curves is done and the axial dispersion coefficients are computed. Afterwards, a flow model consisting of a series of a plug flow and an axial dispersion zones is proposed, the model parameters being regressed against the experimental data. This model, combined with a simplified kinetics, is therefore expected to be an interesting tool to reduce NOx in the existing combustors. Model validation against experiments was done. 2 E.D. Lavric et al.