Numerical Simulation Of Heat Transfer And NO_x Generation In A Natural Gas-Fired Flat Glass Furnace

The operating temperature of the glass furnace is 1400℃,thermal NO_x is the main pathway of NO_x generation.Radiation heat transfer is one of the key factors affecting the temperature field in the furnace.In this paper,the high-precision weighted sum of gray gases models for the H₂O-CO₂-soot mixture are developed,and the NO_x generation characteristics in the flat glass furnace are investigated on this basis.Firstly,different gas and/or soot radiative property models are compared on a one-dimensional plane-parallel slab with non-isothermal inhomogeneous conditions,including two gas radiative property models:based on H₂O-CO₂ mixture（MM）and based on single species（SM）,two soot radiative property models:gray model（GS）and non-gray model（NS）,and four gas-soot radiative property models:combining the two gas radiative property models and two soot radiative property models with coupling directly method and superposition method.The discrete coordinate method is used to solve the radiation transfer equation.The predicted total emissivity,radiative source term,and radiation heat flux are examined under different path lengths.The results show that,under different working conditions and different path lengths,the max error of the MM-GS and the SM-GS model is within 15%,while the max error of the MM-NS and the SM-NS is within 5%.Then,the gas-soot radiative property models with good evaluation results in a one-dimensional are selected for validation in an Adelaide turbulent jet flame,i.e.,the GMM-GS model,the MM-GS model,the MM-NS model,the SM-GS model,the FSCK model,and the OTA model are selected for validation.The effects of different radiative property models on turbulent flame temperature,soot volume fraction,radiation source term,and wall heat flux are analyzed.The results show that the effect of radiative property models on flame temperature and soot volume fraction is less than the effect on wall heat flux simulation calculation,and the difference of different radiative property models on the calculation of radiation heat flux can be up to 26%.The MM-NS model is more accurate,the maximum relative error on the calculation of the radiation source term is within 6%,and the maximum relative error on the calculation of radiation heat flux is within 3%.The calculation cost is1.5 times of the FSCK16 model.Finally,three-dimensional numerical simulations of a foreign natural gas-fired flat glass furnace are carried out for the simulation of pollutant generation.Considering the calculation cost and calculation accuracy,the MM-GS model was selected as the radiative property model,and the non-premixed combustion model was used for the simulation of the combustion process.Numerical simulation of the combustion process was used to optimize the actual operating conditions and to study the effects of input thermal power,excess air coefficient and furnace volume on pollutant generation.The results show that reducing the heat input by 10%and increasing the excess air coefficient by 6%can increase the heat efficiency of the furnace by 1%and reduce NO_x by 40%,CO by 70%,and CO₂ by 10%.