The Numerical Study Of Combustion And Heat Transfer Process Based On Oxy-fuel Condition

With the global depletion of fossil fuels and environmental pollution becoming increas-ingly serious,there is a urgent need of energy saving and emission reduction for every country,at the same time,the research of new energy and efficient environmentally friendly combus-tion technology gradually concerned by people.Oxy-fuel combustion technology(O2/CO2 recycle combustion)has the advantages of high combustion efficiency and less pollutant dis-charge,which has attracted wide attention of scholars.However,the research on this technol-ogy is confined to coal combustion.Because of its high calorific value,low combustion pol-lution and wide sources,methane is considered to be the most promising clean energy.There-fore,the oxy-fuel combustion process of methane is studies by numerical method in this paper.Because of the large amount of absorptive medium in the flue gas under the condition of oxy-fuel combustion,the radiation characteristic parameter of the flue gas will change greatly.Whether the traditional radiation models are applicable under the condition of oxy-fuel com-bustion is to be studied.At the same time,the turbulence-radiation interactions effect are ob-vious in the turbulent diffusion combustion.Therefore,the above two points must be consid-ered in the mathematical model.The vast majority of commercial CFD software(such as Fluent)can not consider the non-gray radiation and TRI effect.Therefore,a non-gray radia-tive heat transfer model and its non-gray-TRI model are developed in this paper.In order to comprehensively investigate the accuracy and efficiency of non-gray radiation model,the line-by-line model(LBL)based on HITRAN database was built firstly.Based on the results of the LBL model,the emissivity and radiative heat transfer(including heat transfer rate and ra-diative source term)of the typical radiation model at different compositions and temperatures under dry and wet recycles were investigated.The applicability and computational speed of each model under the conditions of oxy-fuel combustion were analyzed,and the radiative heat transfer model which is suitable for non-gray-TRI was obtained.On this basis,this paper aimed at solving the axisymmetric combustion process in cylindrical coordinate system.The results of the non-gray-TRI model are verified by compared with experiments and simulations of relevant literatures.The results show that the model of this paper is correct and accurate.Based on the non-gray-TRI model,the results of ignoring radiation and using Gray,Gray-TRI and WSGG were discussed respectively.The results show that,in oxy-fuel combustion,con-sidering the gas as gray,and ignoring the influence of turbulence pulsation will lead to greater error,which further proves that the non-gray-TRI model is necessary.At last,the effect of different O2 concentration on the combustion and heat transfer process was investigated by non-gray-TRI diffusion combustion model.The law of the change of temperature and heat transfer rate with O2 concentration was obtained,which provided the theoretical basis for the industrial application of methane O2/CO2 combustion.