Influence of air jet characteristics on the pure ammonia-fuelled swirl diffusion flame
Ammonia is an ideal energy source,in order to make better use of pure ammonia fuel and develop a burner suitable for pure am-monia fuel,this study conducted 3D modelling of a 10 kWth natural gas swirl burner by numerical simulation,and simulated the combus-tion and NO emission performance of pure ammonia in it.The influence of air jet characteristics on the flame morphology,temperature dis-tribution,NO generation and emission was explored,in order to optimize the pure ammonia combustion capability of the burner.In the early stage of combustion,the influence of swirl on the mixing of fuel and air is more significant,while in the late stage of combustion the turbulence intensity has a greater influence on the process.It was found that the swirl intensity could be enhanced by increasing the air jet hole area(from 12.8 mm2 to 19.2 mm2)and the air jet angle(from 15° to 30°),which could promote the mixing of fuel and air,and thus promote the rapid and stable combustion of ammonia fuel and shorten the ignition distance.However,too large jet angle may lead to a short separation of air and fuel,delaying the mixing process and prolonging the ignition distance.In addition,it was also found that de-creasing the jet hole area and increasing the jet angle would also enhance the intensity of nearby turbulence near the combustor nozzle,which would promote the mixing and combustion of ammonia fuel and air,thus generating a localized high-temperature zone and leading to an increase in the concentration of NO generation.Through comparative optimization,the pure ammonia burner achieved stable low-NO combustion with air jet orifice area 19.2 mm2,jet angle 15°,jet velocity 19.83 m/s,ignition distance 0.024 m,flame length 0.446 m,and the peak NO generation concentration and emission concentration were reduced to 443x10-6 and 37.7x10-6,respectively.
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