Numerical Simulation Study Of Flameless Porous Media Combustion Of Ammonia

The greenhouse gases produced by the burning of traditional fossil fuels in industry have caused serious harm to the environment and there is a need for further development of alternative clean energy sources and new combustion technologies.Compared with traditional combustion methods,porous media burners have simple structure,high combustion efficiency and low pollutant emission.At present,the research on porous media combustion mainly focuses on hydrocarbon fuel.Ammonia is a hydrogen carrier with high ignition point,low laminar flame propagation speed and no greenhouse gas in combustion products.Using porous media combustion technology can reduce NOx produced by ammonia combustion and improve the combustion stability.Therefore,it is of great significance to study the combustion of ammonia in inert porous media to reduce environmental pressure.In this paper,chemical reaction kinetics software was used to simplify the detailed combustion reaction mechanism of ammonia gas and verify the accuracy of the mechanism through the linear diagram method and sensitivity analysis method based on error propagation.Will simplify the mechanism of import the FLUENT software,respectively using heat balance model and the coupling calculation of heat balance model,by changing the equivalent ratio,inlet velocity,wall material,porosity,solid skeleton coefficient of thermal conductivity,the microchannel width,explores the ammonia and air premixed gases in partially filled with porous media combustion chamber and combustion characteristic of microchannel and stable-combustion range.By synthesizing the two simplified methods,the simplified mechanism containing 20 components and 65 steps of elemental reaction was obtained,and it was verified that the 65 steps of simplified mechanism could well predict the ammonia combustion in the range of 0.2～1.4 equivalent ratio.Ammonia was burned at 2mm of microchannel entrance.With the increase of the width of the porous media microchannel,the steady fire equivalent ratio range of ammonia in the microchannel first increased and then decreased,and the steady fire inlet velocity range became smaller and smaller.The steady burning equivalent ratio of ammonia in porous medium combustion ranges from 0.15 to 0.45,and the steady burning velocity ranges from 0.2 to 0.4m/s.After the addition of porous media to the burner,NOx emissions were significantly reduced compared with single channel,and NOx concentration increased with the increase of the equivalent ratio and inlet velocity.In conclusion,by using porous media can realized ammonia high efficient and clean combustion.