不同通道内超临界水中颗粒物的运动沉积特性研究

Sedimentary characteristics of particle motion in supercritical water in different channels

利用ANSYS CFX软件模拟,采用κ-ε模型来预测通道内的湍流变化,得到不同粒径(1～10μm)颗粒在不同管道内超临界水中的运动沉积特性规律。发现不同管道中细颗粒物的运动沉积浓度在不同入口温度下,大致呈现"M"型分布,在靠近管道附近存在颗粒物浓度的极值。不同入口速度条件下,低速时各管道中颗粒浓度分布非常离散,速度提高后各管道内的颗粒物浓度呈现各自分布特点,主要受到颗粒扩散、热泳力、湍流作用及二次流等影响。分析出颗粒的运动沉积主要是颗粒与水分子间动量交换,以及颗粒运动受到阻力综合作用的结果。

[Background] Motion characteristics of fine particles in different pipelines is of great significance to the development of two-phase flow and improves the removal efficiency of particulate matter emitted from power plants.[Purpose] This study aims at the effects of temperature gradient and velocity on the motion law and distribution characteristics of fine particulate matter in supercritical water.[Methods] Ansys CFX software was employed as simulation tool, and the κ-ε model was used to predict the turbulence change in the channel. Motion deposition characteristics of particles with different sizes (1~10 μm) in different pipelines in the supercritical water were calculated and analyzed.[Results] Simulation results showed that the motion deposition concentration of fine particulate matter in different pipes was roughly shown as "M" distribution at different inlet temperatures. At the same time, there was an extreme value of particulate matter concentration near the pipe. Under different inlet speed conditions, the distribution of particle concentration in each pipeline was very discrete at low speed, and the concentration of particulate matter in each pipeline exhibited their own distribution characteristics while the speed was increasing.[Conclusion] The kinetic deposition of particles is the result of the momentum exchange between the particles and the resistance of the particle movement.