燃煤锅炉三维CFD数值模型水冷壁热边界条件设定方法

目前,燃煤锅炉三维CFD数值模拟中对炉膛水冷壁传热分布的预测大都基于给定的壁面温度边界条件。然而,此方法无法体现锅炉运行状态对壁面传热与壁温分布的影响。提出了一种基于锅炉烟气侧放热与汽水侧吸热间热平衡关系的壁面传热计算方法,并重点讨论了壁面传热系数的物理意义及取值方法。研究发现,壁面传热系数基本由壁面结渣状态决定,因此可根据壁面渣层的传热系数确定。本文方法将影响壁面传热的关键因素合理地体现在计算过程中,同时在模型复杂性与工程适用性之间保持了合理的平衡。采用此方法对一台320 MW锅炉的燃烧与传热分布进行了数值模拟,水冷壁吸热量的预测结果与锅炉运行数据吻合良好。

Setting Method of Thermal Boundary Condition of Water Wall for Three-dimensional CFD Numerical Model of Coal-fired Boiler

Currently,the prediction of the heat transfer distribution of the water wall in the furnace is mostly based on the given wall temperature boundary condition in three dimensional CFD numerical simulation of coal fired boiler. However,this method cannot reflect the impacts of boiler operating conditions on the wall heat transfer and wall temperature distribution. A calculation method of the wall heat transfer based on the heat balance relationship between the boiler flue gas side heat release and steam water side heat absorption is proposed.The physical significance and evaluation method of the wall heat transfer coefficient are discussed emphatically.The research results show that the wall heat transfer coefficient is largely determined by the slagging condition of furnace wall, so that its value can be determined in accordance with the heat transfer coefficient of the slag layer on the wall.The key factors affecting wall heat transfer are reasonably reflected in the calculation process by the method introduced in this paper, and a reasonable balance is maintained between model complexity and engineering applicability.The combustion and heat transfer distribution of a 320 MW boiler are numerically simulated by using this method, and the predicted results of heat absorption of water wall agree well with the boiler operation data.