| The Oxy-Coal Combustion System of Near-zero Emissions?OCCSS?uses syngas and super clean coal as the fuels.Using different coals or different syngas processing technology can change the ratios of main flammable gas CO/H2/CH4 in fuels.Besides,the influence of equivalence ratios,preheating temperature and vapor concentration to the laminar flame speed should be considered during designing combustor and organizing combustion process.The dissertation measures the laminar flame speed of Pre-mixture CO/H2/CH4 under different fuel ratios,equivalence ratios,preheating temperature and vapor concentrations by bunsen burner.Compete the flame speed between experiment results and simulation results obtained by USC II mechanism and GRI 3.0 mechanism.Finally,GRI 3.0 mechanism is selected to analyze the results in thermodynamics and chemistry dynamics,for its simulation results are closer to the experiment results.The results show that the influence of CH4 content to laminar flame speed is related to the ratio of CO/H2,at the vapor concentration 47%condition,the flame speed increases nonlinearly with CH4 content rising,when CO/H2 is above 75/25;the flame speed decreases nonlinearly with CH4 content rising when CO/H2 is under 75/25;when CO/H2equals 75/25,the flame speed doesn't change with CH4 content changing.Temperature isn't the main factor affecting the laminar flame speed.Compared with the max concentration of OH and H+OH,the max concentration of H shows a better positive correlation with the flame speed.In O2/H2O condition,the flame speed of CO/H2/CH4 increases firstly,and then declines with the increasing of equivalence ratio,when CH4 content is 2%,the max flame speed occurs at the equivalence ratio 1.3,when CH4 content is 8%,the max flame speed occurs at the equivalence ratio 1.2,the equivalence ratio corresponding with the max flame speed has no concern with CO/H2 ratio.The chemistry dynamics factor influences the flame speed greater than thermodynamics factor when changing equivalence ratios.When the equivalence ratios are between 0.8 and 1.4,elemental reactions R99:CO+OH=CO2+H and R84:OH+H2=H+H2O generate the most radical H while R38:H+O2=O+OHconsumes radical H most,with the increase of equivalence ratio,the growth rate of R99 and R84 is higher than that of R38,promoting the accumulation of H radical.With the equivalence ratio increasing,R3:O+H2=H+OH grows rapidly.Increasing the preheating temperature can increase the adiabatic flame temperature,while it influences the sensitivity of main elemental reactions not obviously.Therefore,increasing the preheating temperature affects the flame speed in thermodynamic aspect mainly.In different CO/H2/CH4 ratios,the flame speed changes completely with the increase of vapor concentration.When CH4 and H2 content is low,with the increase of vapor concentration,the flame speed rise first and then decreases,increasing CH4 or H2 content appropriate,the flame speed declines slowly at first and then drops fast with the increase of vapor concentration,when the H2 content is higher,the flame speed shows nearly linear decrease with the vapor concentration rising.This phenomenon is mainly caused by the coupling between the thermodynamic and chemistry dynamics influence of water vapor.The chemistry dynamics influence of water vapor is mainly caused by the elemental reaction R86:2OH=O+H2O moving to reverse direction.The H2 content mainly affects the reaction rate of R84:OH+H2=H+H2O and R3:O+H2=H+OH;The CH4 content mainly affects the reaction rate of R3:O+H2=H+OH,R11:O+CH4=OH+CH3,R84:OH+H2=H+H2O and R98:OH+CH4=CH3+H2O. |
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