利用LBM-FVM-CA耦合方法模拟管表面上的颗粒沉积与脱离过程  

Coupled LBM-FVM-CA simulation of particle deposition and removal processes on tubes

作　　者：童自翔 何雅玲[1] 李印实[1] 谭厚章[1] 

机构地区：[1]西安交通大学,热流科学与工程教育部重点实验室,西安710049

出　　处：《科学通报》2016年第17期1912-1921,共10页Chinese Science Bulletin

基　　金：国家重点基础研究发展计划(2013CB228304,2013CB228303)资助

摘　　要：发展了一个包含积灰形状演化、颗粒沉积和脱离机理的数值模型和计算方法,模拟了单排管表面的积灰过程.首先建立了流动的格子Boltzmann方法-有限容积方法(LBM-FVM)耦合的计算模型,给出了通过宏观参数构建多松弛LBM分布函数的重构算子;并结合元胞自动机模型、能量平衡模型以及力和力矩分析,模拟了颗粒的运动、沉积和碰撞过程;其次,针对模拟的时间步长相对于实际积灰时间较短的困难,提出了用于将模拟时间换算到实际时间的比例;然后,具体模拟和分析了不同直径颗粒在不同入口速度下的积灰过程.结果显示,积灰面积随时间呈指数增长并趋近于一个平衡值;在颗粒质量分数一定时,存在一个积灰速率较高的速度范围;颗粒脱离在迎风面和管子正后方较为严重,但在背风面侧面相对缓和;积灰层在整个背风面生长,在迎风面形成锥形,改变了流动并阻止了颗粒的进一步沉积.A numerical model was proposed to simulate the fouling processes on the tubes, which contained the evolution of the fouling shape and the particle deposition/removal mechanisms. Firstly, the coupled lattice Boltzmann method（LBM） and finite volume method（FVM） was established to simulate the air flow. The flow around the tubes was simulated by the LBM due to its convenience in complex boundary conditions. The downstream flow was simulated by the FVM to save the computational source. A reconstruction operator was derived for the information transfer from macroscopic parameters to multiple-relaxation-time LBM. The cellular automata model, energy conservation model and moment analysis were included to simulate the particle motion, collision, deposition and removal. Then, because the time step in the simulation was several orders of magnitude shorter than the real fouling time, a time ratio was proposed for the conversion between simulation and real time. Finally, the evolutions of the fouling shapes along with time for different particle diameters and inlet velocities were simulated and analyzed. The results showed that the proposed coupled model can be used to study the particle deposition, removal and the changing of the fouling layers. When the mass concentration was the same, the fouling of small particle grew faster. The fouling area grew exponentially with time. It grew rapidly in the beginning, then grew slower and finally reached an asymptotic balance value. When the particle concentration was specified, the fouling rate first grew with and then decreased with the increasing inlet velocity. Therefore, there was a velocity range in which the fouling rate was high. As for the shape of the fouling layer, the removal was severe on the windward side, but the direct impaction of the particles formed the cone-shaped fouling layers. The cone-shape changed the air flow and stopped the deposition on the windward side. The fouling layers grew on the entire leeward side of the tubes and finally stopped when the re

关 键 词：工业余热 积灰 颗粒沉积 颗粒脱离 格子BOLTZMANN方法 有限容积方法 

分 类 号：TK115[动力工程及工程热物理—热能工程]