摘要现如今，我国沙尘天气出现的频率越来越高，沙尘天气对人们的健康、出行，社会生产活动等都有较大的影响。因此，人们对于风沙运动的研究越来越重视。本文正是在这样 的背景下，主要着眼于沙尘颗粒形成的流场对于汽车的尾气排放形成的热场所产生的影 响，利用 FLUENT 软件，结合专业知识，综合分析沙尘天气条件的气象特性并总结提出简 化的沙尘天气流场模型，数值模拟汽油机和柴油机排气在沙尘天气流场中的状态，从而分 析汽油机和柴油机排气在沙尘流场中的变化规律以及热特性。 80461

在模拟研究风沙天气对汽车尾气的热流场产生的影响时，首先，结合一些典型风沙天 气的研究资料，选用一组具有代表性的沙尘天气数据，由此确定数值模拟中的颗粒相的具 体参数，如粒径、体积分数和流速。其次，以空气作为第一相，沙尘颗粒作为第二相，采 用欧拉-欧拉方法中的 Mixture 模型，假定沙尘颗粒浓度在流域进口处是均匀的，气体相 和颗粒相之间没有相对滑移，将标准的 k-ε 湍流模型扩展到两相流中，加入辐射换热模型， 并用 SIMPLE 算法，根据沙尘颗粒浓度，粒径和风速等不同条件，对比分析了温度场和流 场的各项特性。

毕业论文关键词 车辆排气；风沙两相流；数值模拟；FLUENT

Title The Thermal Simulation Analysis of Vehicle Emission In the Sand-dust Condition

Abstract Sand-dust weather could often be seen in China now, which has deep impact on people’s health, traffic, and social production。 Therefore, researches of windblown sand movement arouse great attention gradually。 Under such background, the paper focuses on the influence of the flow field from sand and dust particles on the thermal field from vehicle emission; comprehensively analyzes the meteorological features of sand-dust weather and summarizes the simplified flow field model of sand-dust weather to do the numerical simulation of the emission state of gasoline engine and diesel engine in the sand-dust flow field with FLUENT and professional knowledge; analyzes the change rules and thermal features of emission of gasoline engine and diesel engine in the sand-dust flow filed。

When simulating the influence of sand-dust weather on the thermal flow field of vehicle off gas, the paper selects some representative sand-dust weather data and researches to confirm the concrete parameters of particle phases in numerical simulation such as particle size, volume fraction, and flow velocity at first。 Furthermore, the research takes air as the first phase and sand particle as the second phase to adopt the Mixture model in Newton-Euler method to assume that the concentration of sand and dust particles is even at the basin entrance and there is no relative slippage between gas phase and particle phase。 Besides, the research expands the standard k-ε turbulent flow model into these two phases, adds the radiation heat transfer model, and adopts the SIMPLE algorithm to compare and analyze the features of temperature field and flow field according to different conditions such as sand and dust concentration, particle size, and wind velocity。

Keyword vehicle emission, windblown sand two-phase flow, numerical simulation, FLUENT

本科毕业设计说明书 第 I 页

目 次

1  绪论 1

1。1   课题研究背景 1

1。2   风沙条件数值模拟的研究现状 1

1。2。1 风沙流数值模拟 1

1。2。2 沙波纹数值模拟