组合弯头内气固两相流动磨损特性的数值模拟与结构优化

Numerical Simulation of the Erosion Characteristics and Structure Optimization of Elbows Connection for Gas-solid Flow

燃煤电厂烟道及煤粉管道中的流动是高雷诺数的气–固两相流,其流动磨损特性影响烟风煤粉系统的性能。受布置空间限制,管道常需要连续布置弯头,此时弯头间距往往较小,弯头结构的耦合作用会对管道内的流动及磨损特性产生影响。该文采用离散相模型（discrete phase model,DPM）离散相模型和Tulsa大学冲蚀与腐蚀研究中心（Erosion/Corrosion Research Center,E/CRC）磨损模型,分别对两种组合弯头内的气–固两相流动与磨损特性进行了数值模拟。获得了两种组合弯头内流场、壁面磨损分布及最大磨损出现位置。并基于管壁磨损特性对组合弯头结构进行优化。结果表明在布置Z型组合弯头结构时,应尽量采用L/D=2的组合方式,以保证较小的壁面磨损;而在布置Π型组合弯头结构时,应尽量使两弯头直接相连（L/D=0）使管壁磨损最轻。

In pulverized coal power plants, the flow in flue ducts and pulverized coal piping is gas-solid flow with high Reynolds number. The flow and erosion characteristics in the pipelines influence the performance of flue and pulverized coal system. Continuous layout of elbows is often necessary due to the restriction of outer space. And connection length between elbows is short at this point. The interaction between two elbows can influence the flow field and erosion pattern in elbows connection structure. In present paper, discrete phase model（DPM） model and Tulsa Erosion/Corrosion Research Center（E/CRC） erosion model were adopted to simulate the flow and erosion characteristics in two kinds of elbows connection. The flow field, erosion distribution and the most eroded position in these two elbows connection were obtained. Moreover, the influence of connection length on erosion rate was also analyzed. Structure optimization was conducted based on the erosion pattern of pipe wall. Results suggest that for Z-type elbows connection, L/D = 2 can yield small erosion rate. But for Π-type elbows connection, direct connection（L/D = 0） is most recommended.