稀释系统论文：分流稀释颗粒测量系统的模拟研究.doc

稀释系统论文：分流稀释颗粒测量系统的模拟研究【中文摘要】柴油机排气颗粒粒径极小,易被直接吸入体内,引发呼吸道及肺部疾病,并且其常吸附有致癌物质,危害人类健康。研究柴油机颗粒排放特性及其控制技术的前提之一是要有良好精度的颗粒排放测量系统。本文基于流体动力学原理,对现有一分流稀释颗粒测量系统进行了研究。应用FLUENT软件对分流稀释颗粒测量系统的稀释混合能力进行了模拟计算。分析了不同实验条件时,柴油机排气与稀释空气在稀释通道内的混合状况。空气与柴油机排气由不同的入口进入稀释通道,本文应用组分输运模型来研究其混合状况,并利用能量方程、湍流模型考虑能量的转换与湍流的影响。应用FLUENT软件对分流稀释颗粒测量系统对传输管内流场的分布特征以及变化规律进行了研究。模拟分析了不同入口速度、入口温度下排气传输管内近壁温度梯度场和整个管径范围内湍动能场的分布特征及变化规律。文中分别利用能量方程、湍流模型考虑能量的转换和湍流的影响。模拟分析了传输管内颗粒沉降率的影响因素及其变化规律。结合传输管内流场的分布特征以及变化规律,应用能量方程、湍流模型、辐射模型、离散相模型分析了不同入口温度、入口速度下,颗粒在壁面上沉降率的变化规律,得出了该传输管内颗粒沉降情况。在考虑颗粒在排气传输管壁面的沉降状况时,充分考虑了湍流脉动的影响,并对不同入口参数下颗粒的热泳沉降率、湍流脉动沉降率以及热泳力与湍流脉动共同作用下的总沉降率进行了分析比较。文中应用离散坐标辐射模型来考虑气体与颗粒间的辐射换热,应用离散相模型分析颗粒在壁面的沉降率通过以上工作,得到了本文研究参数范围内该系统的稀释混合能力和排气传输管内颗粒沉降率的情况,研究成果可为进一步优化该分流稀释颗粒测量系统提供一定的理论依据和研究基础。【英文摘要】Diesel exhaust particles are easily inhaled due to their fine size, which will cause respiratory and lung disease, and the particles have carcinogenic substances adsorption, which is harmful to peoples health. Particle pollution has become a problem needed to be solved urgently. First, we must have a better system for particulate emissions measurement to research of diesel particulate emission control technology. In this paper, many works have been done on the partial flow dilution sampling system for diesel particulate measurement based on the principles of computational fluid dynamics.The mixed-ability of the partial flow dilution sampling system is studied by FLUENT software. Diesel exhaust and air mixing quality are analyzed under different experimental conditions. Due to air and diesel exhaust enter the dilution channel by different entry, Species Model was used to analyze their mixing quality, and Energy Equation was used to analyze their energy exchange, Turbulent Model was used to analyze turbulent effects.Distribution characteristics and variation regularity in the pipeline is studied by FLUENT software. The distribution characteristics and variation regularity of both temperature gradient field of near-wall and turbulent kinetic energy field of pipeline are analyzed under different conditions of inlet velocity and temperature based on Energy Equation, Viscous Model.Influence factors and its variation regularity of diesel particulates deposition rate in the transport pipe are studied. Combine the distribution characteristics and variation regularity of flow field in the transport pipe, particulates thermophoresis deposition, turbulent deposition and the total deposition under thermophoretic force and turbulence are researched, under different conditions of inlet velocity and temperature using Energy Equation, Viscous Model and Radiation Model, Discrete Phase Model. During the course of researching on particulates deposition, influence of turbulent edd is also taken into account enough, also. particulates thermophoresis deposition, turbulent deposition and the total deposition are compared. Radiation Model was used to analyze radiation heat transfer between air and particulates in this paper.After the research work above, the mixed-ability of the particulate measurement system with partial flow dilution sampling system and diesel particulates deposition rate in the pipeline are concluded. Theoretical basis and research foundation of further optimizing this system are supplied by the research results.【关键词】稀释系统 混合能力 柴油机颗粒 热泳沉降 湍流脉动沉降【英文关键词】dilution sampling system mixed-ability diesel particulates thermophoresis deposition turbulent deposition【目录】分流稀释颗粒测量系统的模拟研究摘要11-12ABSTRACT12-13第1章 绪论14-221.1 课题研究背景14-171.2 课题研究意义171.3 国内外研究现状17-211.3.1 多相流研究现状17-181.3.2 热泳沉降研究现状18-211.4 课题研究的主要内容21-22第2章 计算流体动力学基础22-322.1 引言222.2 流体动力学基本控制方程22-272.2.1 连续性方程22-232.2.2 动量方程23-242.2.3 能量守恒方程24-252.2.4 组分质量守恒方程25-262.2.5 控制方程通用形式26-272.3 数值模拟方法27-302.3.1 连续相数值模拟方法27-292.3.2 离散相数值模拟方法29-302.4 FLUENT软件30-312.5 本章小结31-32第3章 模型的建立与方程的离散求解32-463.1 引言323.2 几何模型的建立与网格的划分方法32-333.3 常用边界条件333.4 物理模型的选择33-433.4.1 能量方程33-343.4.2 辐射模型34-353.4.3 湍流模型及近壁区处理35-403.4.4 组分模型40-413.4.5 两相流模型41-433.5 求解器的选择及方程的离散与求解43-453.5.1 求解器的选择433.5.2 方程的离散与求解43-453.6 本章小结45-46第4章 分流稀释颗粒测量系统稀释混合能力分析46-584.1 引言464.2 计算前处理46-524.2.1 几何模型建立与网格划分46-494.2.2 物理模型和边界条件的选定49-504.2.3 模拟用实验条件50-524.3 不同实验条件下稀释通道内流场分析52-564.3.1 稀释通道内不同横截面流场分布52-554.3.2 采样前排气与稀释空气混合质量分析55-564.4 模拟结果验证56-574.5 本章小结57-58第5章 基于颗粒沉降排气传输管数值模拟分析58-785.1 引言58-595.2 计算前处理59-635.2.