煤粉无焰富氧燃烧的数值模拟方法进展

无焰富氧燃烧是煤粉清洁燃烧技术的前沿发展方向之一,可在捕集高浓度CO₂的同时显著降低NOx排放,并提升富氧燃烧稳定性和热力性能。计算流体力学(CFD)作为燃烧研究的重要手段之一,具有快捷、成本低和数据丰富等优点,有效促进了无焰富氧燃烧技术发展。基于笔者团队对煤粉富氧燃烧和无焰燃烧的多年研究积累,对近十几年来煤粉无焰富氧燃烧CFD模拟方法和模拟研究进展进行了总结:首先强调了煤粉无焰燃烧的试验和数学定义,其由于存在非均相反应而区别于气体燃料无焰燃烧;然后详述了煤粉无焰富氧燃烧CFD模拟方法进展,包括模拟流动、传热、燃烧和污染物生成方面的子模型和机理,其中考虑强烈烟气卷吸的可实现k-ε湍流模型、P1或DO辐射模型及针对富氧气氛修正的WSGG气体辐射模型、CPD挥发分析出模型、考虑湍流与化学反应交互的有限速率EDC均相燃烧模型、针对无焰及富氧燃烧开发验证的均相反应机理、考虑气化反应的多步表面焦炭非均相燃尽模型、含氮化学详细反应机理氮转化模拟、动态自适应反应机理加速算法等可显著提高煤粉无焰富氧燃烧的模拟精度和计算效率。总结了煤粉无焰富氧燃烧在基准对照试验、微观反应区域分析、宏观反应特征、污染物生成及大型化锅炉概念设计方面的模拟研究情况;最后以大涡模拟、燃烧模型、高精度反应机理及动态自适应反应机理、工业应用优化等角度展望了煤粉无焰富氧燃烧CFD研究的发展方向。

Progress in numerical methods for flameless oxy-fuel combustion of pulverized coal

Flameless oxy-fuel combustion of pulverized coal is one of the development directions of clean coal combustion technology,which can obtain high concentration of CO₂,significantly reduce NOx emissions,and improve the combustion stability and thermal perform?ance.Computational fluid dynamics(CFD),as one of the important means of combustion research,has the advantages of fast running,low cost,and rich data,which effectively promotes the development of flameless oxy-fuel combustion technology.Based on our long-term research experience on oxy-fuel and flameless combustion of pulverized coal,the CFD simulation method and research progress of flameless oxy-fuel combustion of pulverized coal were summarized.The experimental and mathematical definitions of coal flameless com?bustion were firstly introduced,which were different from the flameless combustion of gaseous fuels due to the heterogeneous reaction.Then the progress of the CFD methods for flameless oxy-fuel combustion of pulverized coal was discussed in detail,including the sub-models and mechanisms of flow,heat transfer,combustion and pollutant formation.The simulation accuracy and calculation efficiency of flameless oxy-fuel combustion of pulverized coal can be significantly improved by using the realizable k-εturbulence model considering strong flue gas entrainment,P1 or DO radiation model,WSGG gaseous radiation model modified for oxy-fuel condition,CPD devolatilization mod?el,finite-rate EDC homogeneous combustion model considering turbulence-chemistry interaction,homogeneous reaction mechanisms devel?oped for flameless and oxy-fuel combustion,multi-step surface heterogeneous char burnout model,detailed reaction mechanisms for nitro?gen conversion and dynamic adaptive chemistry for calculation acceleration.Next,the numerical studies on flameless oxy-fuel combustion of pulverized coal were reviewed in the aspects of benchmark experiments,micro reaction zone analysis,macro reaction characteristics,pol?lutant formation and conceptual designs of large-scale boiler.Finally,the development direction of CFD research on flameless oxycoal combustion were proposed,such as large eddy simulation,combustion models,high-precision detailed reaction mechanisms,dynamic adaptive chemistry modeling,and industrial application optimization.