锅炉烟气绕换热器管道的直接数值模拟

Direct Numerical Simulation Studies on Boiler Gas Flowing Through Heat-exchanger Pipe

采用直接数值模拟方法对含尘烟气经过受热面管道的气相场和颗粒场进行了数值计算，讨论了管壁后涡结构的脱落，同时分析了灰粒与受热面管壁的碰撞与磨损问题。认为随雷诺数的增加，漩涡脱落频率也随之增加，并得出二维流场向三维转捩的临界雷诺数为170～180。得出灰粒尺寸是影响碰撞频率和磨损率的一个主要因素，随粒径的增大，灰粒与壁面的碰撞频率呈指数增长。颗粒的冲击角度在20°左右颗粒对壁面的冲击率最大。

Direct numerical simulation studies are conducted on the characteristics of gas field and particle field when the ash-laden gas flowing through the heating surface pipe. The vortex dislocation is discussed, and the impact and erosion between the coal ash and the heating surface pipe are analyzed. When Reynolds number increases, the frequency of the vortexes shedding off the pipe increases. The critical Reynolds is in range of 170 - 180 in transition process of two-dimensional to three-dimensional gas field. It is conclu- ded that the diameter of coal ash is an important factor of collision frequency, and the increase of diameter of particle leads to exponential augment of the collision frequency. The abrasion loss of surface is boosted to the maximum extent with the impact angle 20°of coal ash.