热力发电

在煤粉炉中，传热过程主要以辐射为主导，且随着炉膛尺寸的增大，煤粉颗粒的辐射贡献更为显著。值得注意的是，煤粉颗粒的燃尽率对其辐射特性具有重要影响，但现有多数数值模拟研究往往忽略此效应，将颗粒发射率与散射系数设为常数。为此，以600 MW超临界对冲燃烧锅炉为研究对象，采用计算流体动力学（CFD）方法对比了三类辐射特性模型对辐射传热预测结果的影响，具体包括常数模型（发射率和散射系数恒定）、线性模型（辐射特性随颗粒燃尽率呈线性变化）、普朗克平均系数模型（基于普朗克平均发射率和散射系数）。研究结果表明：相较于同时计入气体与颗粒辐射的情况，忽略颗粒辐射会使炉膛峰值温度高估约300 K。在计入颗粒辐射的前提下，与普朗克平均系数模型相比，常数模型对燃烧器区域螺旋膜式壁传热量的估算偏低约9%，对壁面平均热流密度峰值的估算也偏低约12.5%；而线性模型则会高估该峰值。上述发现可为煤粉燃烧数值模拟中辐射特性模型的合理选取提供参考。

In pulverized coal-fired furnaces, the heat transfer process is dominated by radiation. With the increase in furnace size, the radiative contribution of pulverized coal particles becomes increasingly prominent. Notably, the burnout ratio of pulverized coal particles exerts a critical influence on their radiative properties. However, most existing numerical simulation studies tend to overlook this effect and set the particle emissivity and scattering coefficient as constants. To address this issue, this study takes a 600 MW supercritical opposed-fired boiler as the research object and employs computational fluid dynamics(CFD) to analyze the effects of three types of radiative property models on the prediction results of radiative heat transfer. These models include the constant model(emissivity and scattering coefficient remain constant), the linear model(radiative properties vary linearly with particle burnout ratio), and the Planck mean coefficient model(based on Planck mean emissivity and scattering coefficient). The results indicate that compared with the scenario where both gas and particle radiation are considered, neglecting particle radiation leads to an overestimation of the furnace peak temperature by approximately 300 K. When particle radiation is taken into account, compared with the Planck mean coefficient model, the constant model underestimates the heat transfer rate of the spiral membrane wall in the burner region by about 9% and the peak value of the average wall heat flux by 12.5%, while the linear model results in an overestimation of the peak value. These findings can provide a reference for the reasonable selection of radiative property models in the numerical simulation of pulverized coal combustion.