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本研究通过数值模拟的方法研究了低真空条件下(4000 Pa)UF6气流中的亚微米UO2F2颗粒(0.2 μm和1 μm)在管道内的团聚和沉积特性。在欧拉-拉格朗日框架下构建了用于描述气固两相流中颗粒团聚和沉积的动力学模型，其中团聚模型考虑了湍流团聚和布朗团聚，沉积模型是基于能量守恒的临界速度模型。在此基础上研究了节流件结构、气体流量和粒径对颗粒沉积和团聚特性的影响规律。结果表明：低真空条件下，带孔板的管道和带阀门的弯管内，惯性分离是颗粒沉积的主要机制，大粒径颗粒的沉积比例高于小粒径颗粒。在带孔板的管道内，颗粒主要受回流气体夹带而沉积在孔板下游管道壁面，沉积位置的形状呈环状和柱面形状；增加气体流量会增加孔板上下游的压比，使孔板下游局部位置的气体达到超声速，增大回流区强度，卷吸更多颗粒，进一步增加颗粒的沉积比例。在带阀门的管道内，颗粒主要沉积在附近存在回流区的管道壁面，沉积位置的形状呈特有的3个环状(低流量下)或柱面形状(高流量下)。由于孔板的节流效应大于阀门，孔板管道内颗粒的惯性分离作用更显著，因此孔板内颗粒的沉积比例更高。湍流耗散率和碰撞核函数的分析表明，带孔板的管道内，气体流量为90 g/s时，湍流碰撞和布朗碰撞在颗粒长大过程中贡献相似；其他工况下，布朗碰撞在颗粒长大过程中贡献大于湍流碰撞。
Abstract：This study investigates the agglomeration and deposition characteristics of submicron UO2F2 particles (0.2 μm and 1 μm) within the pipe in UF6 gas flow under low-vacuum conditions (4000 Pa) through numerical simulations. A kinetic model was developed within the Euler-Lagrange framework to describe particle agglomeration and deposition in gas-solid two-phase flow. The agglomeration model incorporates turbulent agglomeration and Brownian agglomeration， while the deposition model is based on a critical velocity approach derived from energy conservation. The effects of throttle structure， gas flow rate， and particle size on particle deposition and agglomeration were systematically analyzed. The results demonstrate that under low-vacuum conditions， inertial separation is the primary mechanism for particle deposition in both orifice plate and valve-equipped pipelines. Larger particles exhibit higher deposition ratios than smaller ones. In the orifice plate pipeline， particles are primarily entrained by recirculating gas and deposit on the pipe wall downstream of the orifice plate， forming annular or cylindrical deposition patterns. Increasing the gas flow rate raises the pressure ratio across the orifice plate， resulting in localized supersonic flow downstream and enhancing the recirculation zone intensity， thereby entraining more particles and further increasing the deposition ratio. In the valve-equipped pipeline， particles mainly deposit on the pipe wall near recirculation zones， forming three distinct rings at low flow rates or cylindrical shapes at high flow rates. Due to the stronger throttling effect of the orifice plate compared to the valve， the inertial separation of particles is more pronounced in the orifice plate pipeline， leading to higher particle deposition ratios. Analysis of the turbulent dissipation rate and collision kernel functions reveals that in the orifice plate pipeline at a gas flow rate of 90 g/s， the contributions of turbulent collisions and Brownian collisions to particle growth are comparable. Under other conditions， Brownian collisions play a more significant role in particle growth than turbulent collisions.
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基本信息:
DOI：10.13922/j.cnki.cjvst.202511001
中图分类号:TB75;TP391.9
引用信息:
[1]王泽涛,张克杰,华伟健,等.低真空节流元件内颗粒团聚与沉积仿真研究[J].真空科学与技术学报().DOI:10.13922/j.cnki.cjvst.202511001.
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