A simple model with detailed chemistry for estimation of NOx and CO emission of porous burners

Abstract

A simple model with detailed chemistry for predictions of NO and CO emission from cylindrical porous burners is proposed on the basis of chemical reactor network concept. Combustion in the inner hollow of the burner is modelled by laminar premixed flame while the processes inside the porous shell are described by zero-dimensional constant pressure perfect stirred reactor. Numerical results on NO and CO concentrations in combustion products are compared with experimental data obtained for combustible mixtures of different compositions including natural gas/air blended with hydrogen or oxygen. It is found that CO concentration is highly sensitive to the conditions in an exhaust pipe and processes in this pipe have to be modelled to achieve accurate enough prediction of carbon oxide emission. Numerical results are in a good qualitative agreement with experimental data and provide an estimate of pollutant emission concentration. Both computational and experimental results coincide in conclusion that hydrogen additives slightly reduce pollutant emission while usage of oxygen-enriched oxidiser noticeably increase NO concentration. The proposed model is also applied to predict the effect of water vapour injection on NO and CO emission of porous media burners. In this case, numerical results allow to expect more prominent emission reduction compared with Hl addition. The model assumptions, limits of applicability, possible ways of further improvement and expansion of the model are also discussed in the paper.