Investigation Of Combustion Characteristics Of Steam Diluting Natural Gas Diffusion Flame

In the problem of the domestic gas turbine power plant frequently start-up causing by yellow fume under low load condition,the diffusion flame on duty high pollutant emission is the main reason.Steam dilution is a feasible solution to reduce the emission of fire pollutants on duty.The effect of steam dilution uniformity on the emission characteristics of natural gas diffusion flame pollutants was studied by the means of numerical simulation and experiments.According to the diffusion burner used in a gas turbine combustor,the influence of natural gas/steam mixture on combustion and emission characteristics was studied by numerical simulation,and the key structure of mixing was studied.The influence of preferred equipment on combustion characteristics was studied through experiments.The work is shown as follows:(1)Chemical reaction network model was built by CHEMKIN to get the NOx emissions under different natural gas/steam mixing uniformity(Spatial Mixing Defficiency,SMD)and dilution ratio.The influence of steam dilution ratio and SMD on CO and NOx is analyzed qualitatively.The results showed that,with the increase of steam dilution ratio,the flame temperature decreased,the emission of NOx decreased,and CO emissions increased.Increasing steam dilution uniformity improves the generation of CO and NOx.(2)In view of the mixing device of natural gas and steam,the structure of SV static mixer is selected,and the influence of mixing unit number,mixing unit obliquity and mixing interval on mixing performance is analyzed by numerical simulation.The optimum structure of the static mixer is determined:the number of mixing units is 5,the blade angle of the mixing unit is 45 degrees,and the gap between the mixing units is zero.(3)The effect of steam dilution ratio and dilution uniformity on diffusion flame characteristics and pollutant emission was studied by numerical simulation combined with experimental method.The results show that with the increase of dilution ratio,strength of OH natural gas diffusion flame tends to weak,the flame structure tends to be compact,thw emission of CO increase and NOx decrease.But with the further increase of dilution ratio,NOx emission yields decreased,and the flame stability decreased;Under the same steam dilution ratio,reducing the steam dilution SMD by static mixer,diffusion flame structure seemed approximately no change,but the reaction zone of OH peak signal intensity decreased,and NOx and CO showed a decreasing trend.The experimental results that the effectiveness of improving the uniformity of steam dilution on emission reduction was verified.The results can provide theoretical basis and experimental data for solving the yellow smoke problem in the starting process of natural gas turbine and widening the scope of low NOx.