摘  要

乘用车进气系统是车辆的重要组成部分，进气系统的性能影响着发动机和整车性能。不合理的进气系统设计导致进气阻力较大，发动机燃油经济性变差.同时进气阻力增加造成系统内部真空度加大，对系统各接口密封性提出严格的要求，当不能完全满足密封条件时，未经过滤的空气会从各接口被吸入气缸，造成气缸的磨损，减短气缸的使用寿命。

本次毕业设计运用Fluent流体分析软件对车辆进气系统特性进行三维数值模拟分析，排气消声系统内部流动特性进行三维数值模拟分析，根据仿真分析的结果得出气流速度、温度和压力分布规律，从而确定进气系统的改进方向。本课题将涉及到热力学、声学、流体力学等多门学科，具有一定的学术价值和工程应用价值。应用Fluent流体力学分析软件建立进气系统内部数值计算模型，模拟结果可以用于指导实验研究，节约实验次数和时间，促进进气系统结构改进。

关键词：排气系统；内流场；流体分析；数值模拟；CFD

Abstract

The intake system of passenger car is an important part of the vehicle. The performance of the intake system affects the performance of the engine and the whole vehicle. Unreasonable design of intake system leads to larger intake resistance and worse fuel economy of engine. At the same time，the increase of air intake resistance increases the internal vacuum of the system and puts forward strict requirements for the sealing property of the system interfaces. When the sealing conditions are not fully satisfied，the unfiltered air will be sucked into the cylinder from the various interfaces，resulting in the wear and tear of the cylinder. Reduce the service life of the cylinder.

The graduation project uses the Fluent fluid analysis software to carry on the three-dimensional numerical simulation analysis to the vehicle intake system characteristic，the exhaust muffler system interior flow characteristic carries on the three-dimensional numerical simulation analysis，according to the simulation analysis result obtains the airflow velocity，The distribution law of temperature and pressure，so as to determine the direction of improvement of the intake system. This subject will involve many subjects such as thermodynamics，acoustics，fluid mechanics and so on. It has certain academic value and engineering application value. The internal numerical calculation model of intake air system is established by using Fluent hydrodynamic analysis software. The simulation results can be used to guide the experimental research and save the times and time of the experiment. Promote the improvement of intake system structure.

Keywords：exhaust system；internal flow field；fluid analysis；numerical simulation；CFD