Chemical structures and theoretical models of lean premixed atmospheric-pressure propene/O&lt;sub&gt;2&lt;/sub&gt;/N&lt;sub&gt;2&lt;/sub&gt; flames

A Seydi,J.L Delfau,J Biet,C Vovelle

doi:10.4314/bcse.v26i2.5

Abstract

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three detailed reaction mechanisms. A very good agreement was observed for the main properties: reactants consumption, final products (CO 2 , H 2 O) and the main intermediates: CO and H 2 . Only a general agreement is also observed between predicted and measured mole fraction profiles for minor intermediates. Marked differences occurred in the prediction of active intermediate species present in small concentrations. Pathways analyses were performed to identify the origins of these discrepancies. It was shown that the same reactions were involved in the three mechanisms to describe the consumption of propene, but with marked differences in their importance. C 2 H 5 , C 2 H 4 , and C 3 H 5 are the main species formed in the first step and their consumption increases the differences between the mechanisms either by the use of different kinetics data for common reactions or by differences in the nature of the consumption reactions. KEY WORDS : Flame structure, Lean flame, Propene, Combustion mechanisms Bull. Chem. Soc. Ethiop. 2012 , 26(2), 211-226. DOI: http://dx.doi.org/10.4314/bcse.v26i2.5

Highlights

Lean premixed combustion has been considered as one of the promising solutions for fuel economy and the reduction of pollutants emission (CO, nitric oxides, and soot)
The very good agreement observed for the maximum temperature shows that experimental heat losses were reduced to a minimum and the flames were stabilized in adiabatic conditions
The structure of lean, premixed propene-oxygen-nitrogen stabilized at atmospheric pressure was studied both experimentally and numerically

Summary

Introduction

Lean premixed combustion has been considered as one of the promising solutions for fuel economy and the reduction of pollutants emission (CO, nitric oxides, and soot). Using lean premixed flames to produce energy in gas turbine is considered as an efficient way to reduce pollutants levels in exhaust gas. Soot and poly aromatic hydrocarbons (PAH) are not formed in lean flames. CO is formed as intermediate species but readily converted into CO2. A decrease in the maximum temperature and in concentration of CH2 radicals limits NOX formation to very low levels. Very lean flames are subjected to instabilities and eventually extinction with, as potential risk, the presence of partial oxygenated species, such as aldehydes, in the exhaust gas. A better knowledge of the combustion chemistry of fueloxygen mixtures is needed to overcome these limitations

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