洁净煤技术

2021, v.27;No.132(02) 150-160

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富氧燃烧中气体辐射模型对燃烧与换热数值模拟的影响
Effect of gas radiation model on the numerical simulation of combustion and heat transfer in oxy-fuel combustion

吴晓峰;范卫东;
WU Xiaofeng;FAN Weidong;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;

摘要(Abstract):

富氧燃烧过程中,由于使用再循环烟气代替空气中N_2作为稀释剂,烟气中存在大量CO_2和H_2O。CO_2和H_2O作为非极性三原子分子,具有N_2没有的辐射能力,导致富氧燃烧中气体辐射特性发生变化。在数值模拟过程中,气体辐射模型是一个重要的子模型。前人提出多种修改后适用于富氧燃烧的气体辐射模型,但不同气体辐射模型在不同富氧燃烧工况数值模拟中的影响尚未有统一研究。为了研究不同炉型下,气体燃烧和煤粉燃烧中气体辐射模型对燃烧换热模拟结果的影响,通过编程,将一种考虑CO影响的气体辐射模型以及文献中的6种典型气体辐射模型耦合入数值模拟计算。结果表明,在气体富氧燃烧中,气体辐射模型影响了火焰结构。同时,燃烧温度分布有所变化,不同模型结果之间差别最高可到500 K。气体与壁面之间的辐射换热受到影响。气体辐射模型对炉膛中心火焰区域影响较大,而对非火焰区域影响较小。在煤粉富氧燃烧过程中,当有效辐射层厚度在0.3 m左右时,如在100 kW下行炉中,气体辐射模型对煤粉燃烧数值模拟结果几乎没有影响。这可能是由于颗粒辐射在辐射换热计算中占主导地位。而当有效辐射层厚度在16 m左右时,如1 000 MW塔式炉中,气体辐射模型对炉内切圆燃烧火焰温度以及组分浓度影响较大,温度差别可到100 K左右。而气体辐射模型对炉膛中心模拟结果没有影响。
In oxy-fuel combustion,flue gas is mainly composed of CO_2 and H_2O because the recycled flue gas is used as diluent instead of N_2 in the air. CO_2 and H_2O have an intensive radiation ability as non-polar triatomic molecule while N_2 has no radiation ability,which leads to the change of gas radiation characteristics in oxy-fuel combustion. In the numerical simulation,gas radiation model is an important sub model. Several modified gas radiation models have been proposed for applying to oxy-fuel combustion,but the effect of different gas radiation model on the numerical simulation of oxy-fuel combustion in different conditions has not been unified. In order to research the effect of gas radiation model on the simulation results of combustion heat transfer in different sizes of furnace with gas or coal combustion,one new gas radiation model considering the effect of CO and other six typical models in the literatures were coupled into the numerical simulation by user defined function programming. The results show that: in the oxy-gas combustion,the flame structure is affected by gas radiation models. Meanwhile,the combustion temperature distribution changes and the difference between the results of different models can reach 500 K. Radiation heat transfer between gas and wall is also controlled by gas radiation models. The effect of gas radiation models on flame zone is rather large while it is ignored in the non-flame zone. In the oxy-coal combustion,when the effective radiation layer thickness is around 0.3 m such as in a 100 kW_(th) down-fired furnace,gas radiation models almost have no effect on the coal combustion numerical simulation results. This may be because particle radiation plays a dominant role in the radiation heat transfer calculation.When the path length is around 16 m such as in a 1 000 MW tower type boiler,gas radiation models have a large effect on the combustion temperature and species concentration. The temperature difference can reach 100 K. However,the gas radiation model has no effect on the simulation results in the non-flame zone in middle of furnace.

关键词(KeyWords): 富氧燃烧;煤燃烧;气体辐射;灰气体加权模型
oxy-fuel combustion;coal combustion;gas radiation;weighted sum of gray gas model

Abstract:

Keywords:

基金项目(Foundation): 国家重点研发计划资助项目(2018YFB0605301)

作者(Author): 吴晓峰;范卫东;
WU Xiaofeng;FAN Weidong;School of Mechanical and Power Engineering,Shanghai Jiao Tong University;

Email:

DOI: 10.13226/j.issn.1006-6772.CCUS20090601

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