电站锅炉燃烧过程数值模拟的收敛性分析

Convergence of Numerical Simulations of the Combustion Process in Utility Boiler

对电站锅炉燃烧过程数值模拟的收敛性进行了详细的分析 .研究表明 :燃烧过程所有控制变量的残差是随迭代次数震荡减小的 .在燃烧迭代的初始阶段 ,残差的下降较快 ;之后 ,随着迭代次数的不断增多 ,残差的降幅减小 ;最后 ,各变量残差会随迭代过程的进行呈现出周期性的变化 ,即计算残差的平均值趋于定值 ,这时 ,在残差的一个震荡周期内的模拟速度、紊动能和温度等参数变化很小 ,燃烧计算有可能假收敛 ,在这种情况下 ,如果将迭代继续下去 ,假收敛的计算参数会随迭代次数缓慢变化 ,只有当迭代次数足够多时 ,即计算次数大于某一个大数后 ,锅炉燃烧计算的速度场、紊动能场和温度场等参数不再随迭代次数变化而变化 ,燃烧计算才达到收敛 .

Convergence of numerical simulations of combustion process in a utility boiler is analyzed carefully.The results show that residuals of all calculated parameters are reduced and oscillated.The residuals drop down fast in first period of combustion calculation,then their falling trend becomes less and less when iteration goes on.Finally the residuals show regular periodicity,and combustion parameters are nearly constant in a concussive period,such as velocity ,turbulence kinetic energy and temperature,etc.This case may be pseudo convergence.If the combustion iteration continues,parameters of pseudo convergence will change slowly.When iteration number is enough,that iteration is bigger than the great one,and all parameters retain constant.This is symbol of combustion convergence.