多孔焦炭燃烧特性的模型构建及数值模拟

焦炭燃烧在固体含碳燃料燃烧进程中占有主导地位,常规燃烧温度范围内(1273～1700 K)的焦炭燃烧过程研究及其模型化对于燃烧设备的设计和优化具有重要的意义。本文根据实际炉内的炭粒燃烧情况,将焦炭燃烧的模拟过程分解成几个环节分别进行研究,即热解后焦炭的初始化学反应活性、焦炭燃烧中化学活性变化、外部氧的扩散对于内孔燃烧的影响,并给出了相关过程的模型计算式。通过与已有管式炉实验结果的比较,新模型的预测结果能较好地反映焦炭的真实燃烧状况。与目前常用的焦炭燃烧模型相比,本模型具备一定的燃料通用性,计算负荷低且能保持相当的预测精度,可耦合到大型燃烧计算程序之中,更为有效地指导实际燃烧设备的优化设计。

Modelling and Numerical Simulation of Porous Char Combustion Characteristics

Char burning process plays an important role on the whole combustion of carbonaceous solid fuels.The modelling and numerical simulation of char burning under the temperature range from 1273 to 1700 K is significant to the design and optimization of combustion devices.According to the char combustion process in the actual furnaces,the modelling of char combustion was divided into several parts and studied separately in this paper,which includes building up of relationship between initial char reactivity and its type,modifying the structure function to describe the change of the intrinsic char reactivity at different carbon conversion and considering the effect of the global oxygen diffusion.Additionally,the developed model equations were proposed.By comparing the predicting values with the experimental data gained from the entrained flow reactor,the good agreement was obtained.Compared with the other char combustion models,the new model has a certain generality, lower computational load,better predicting accurate and can be implanted into the large-scale combustion computational code,which can guide the design or optimization of actual combustion devices more effectively.