The Effects of Radiative Heat Transfer on the Flame Structures of Pulverized Coal Combustion

研究了辐射换热对煤粉燃烧火焰结构的影响。使用严格的辐射处理，数值模型描述了一个一维模型的火焰涉及燃烧的混合物与惰性颗粒悬浮液。同时进行了实验研究，以证实数值分析的结果。研究结果分为以下三大类：1.使用具有颗粒悬浮物的可燃气体混合物的燃烧系统的一维模型，公开了悬浮颗粒具有两个主要影响。一种是通过颗粒的热容抑制燃烧，另一种是通过基于辐射传热的能量再循环增强燃烧。当加载比较小时，后一种效应上级优于前一种效应;当加载比较大时，后一种效应优于前一种效应。颗粒直径和t的影响 关于我们 定量地阐明了粒子的辐射性质.本文从热力学角度对产物-反应物能量再循环燃烧系统进行了深入的讨论，提出了一个新的特征温度--“绝热极限火焰温度”。该温度的概念非常重要，特别是在考虑可用能量和燃烧系统的效率时。研究还表明，对应于绝热极限火焰温度，存在理论最大可用能量。3.本文在考虑颗粒/壁面、壁面/壁面辐射传热以及颗粒间辐射交换的情况下，对气固两相系统的火焰结构和燃烧速度进行了进一步的研究。结果表明，颗粒与壁面、壁面与壁面的辐射换热以及壁面与燃气的对流换热是强化燃烧的重要能量回流途径。少

This study is aimed at clarifying the effects of radiative heat transfer on the on the flame structures of pulverized coal combustion. Using a strict treatment of radiation, a numerical model is developed describing a one-dimensional model of a flame involving a burning mixture with inert particle suspensions. Experimental studies have been also executed simultaneously to confirm the results of numerical analyses. The results are classified into following three large groups.1. Using the one dimensional model of a combustion system of a combustible gas mixture with particle suspension, it is disclosed that the suspended particles have two major effects. One is the suppression of combustion by the heat capacity of particles, and the other is the combustion augmentation by the energy recirculation based on radiative heat transfer. The latter effect is superior to the former one when the loading ratio is small and vice versa when it becomes large. The effects of the particle diameter and t … More he radiative properties of the particle have been clarified quantitatively.2. The thermodynamic aspect of the combustion system with energy recirculation between products and reactants is discussed extensively, and a new characteristic temperature, the "adiabatic limit flame temperature", has been proposed. The concept of this temperature is very important, especially when considering the available energy and the efficiency of combustion systems. It is also shown that there exists the theoretical maximum of the available energy corresponding to the adiabatic limit flame temperature.3. A farther study has been made on the flame structure and burning velocity in a gas-solid two- phase system where particle/wall and wall/wall radiative heat transfers have been taken into account as well as the radiative exchange between particles. The result shows that the important route of energy recirculation for combustion augmentation is the particle to wall and wall to wall radiative heat transfers and the wall to gas convective heat transfer. Less