摘 要

进气歧管是柴油机实现进气功能的主要组成部分，影响了柴油机的排放性，经济性，工况稳定性等特性。因此，要想提高柴油机的各项性能指标，优化进气歧管的几何形状和结构来减少进气过程中的进气阻力是极为有效的方式。进气歧管的优化对于柴油机更广范围内的推广和使用具有重要意义。在以往的传统优化设计中，往往是通过稳态实验加上数值测量来进行，这样的方式不能获得进气歧管内部的能量损失情况，因此无法进行有效的改进。随着计算机的发展，建模软件和CFD流体计算软件的商业化使得进气歧管的优化方式有了根本性的变化。

在本文中，选用的是仿真三维模型加上流场计算的方式进行设计优化。首先，按照某款进气歧管的特征参数，利用CATIA软件获得进气歧管的三维模型，然后导入Hypermesh软件中进行画网格，画网格完成以后导入到ANSYS软件得出流场内部情况，如流量和能量的损耗，是不是存在涡流等等。并且ANSYS软件也可以获得热场的云图。获得流场信息后，再使用CATIA对进气歧管的结构进行改进，如倒角大小、孔径尺寸等等。得出热场情况后，说明优化热场情况是否有必要。

在对进气歧管的热场和流场进行分析之后，获得如下结论：对于进气歧管的热场，由于温度较低，不需要进行优化设计。进气歧管的流场存在压力过大部位，有必要提出优化方案。本文给出了对进气道，格栅以及第一结构柱的改进优化方案。最终给出了进气歧管优化前后的效果图对照情况，给出了优化方案。在最后，将新的进气歧管模型导入CFD分析软件，发现各处压力均有改善，压力差减小约20%，对于进气歧管的应力情况有改善。由于各方面条件不足，本文不采取稳流实验。

论文工作对进气歧管的优化设计提供了具有一定参考价值的研究方法，在文中所提及的进气歧管的优化思路对流场优化是普遍适用的，该研究方法对与柴油机的歧管优化设计也具有普遍适用性。

关键词：进气歧管，三维建模，流场计算，分析优化

Abstract

The intake manifold is the main component of the diesel engine to achieve the intake function, which affects the characteristics of the diesel engine's emissions, economy, and operating conditions. Therefore, in order to improve the various performance indicators of the diesel engine, optimizing the geometry and structure of the intake manifold to reduce the intake resistance in the intake process is an extremely effective method. The optimization of the intake manifold is of great significance for the promotion and use of a wide range of diesel engines. In the conventional optimization design, steady-state experiments and numerical measurements are often performed. In this manner, the energy loss inside the intake manifold cannot be obtained, and therefore it cannot be effectively improved. With the development of computers, the commercialization of modeling software and CFD fluid calculation software has fundamentally changed the way the intake manifold is optimized.

In this paper, the choice of simulation 3D model plus flow field calculations is used to optimize the design. At first, according to the characteristic parameters of a certain type of intake manifold, the 3D model of the intake manifold was obtained using CATIA software, and then imported into the Hypermesh software to draw a grid. After the grid is completed, it is imported into the ANSYS software to obtain the internal flow field. Conditions, such as the loss of flow and energy, is there eddy current and so on. And ANSYS software can also get the hot field cloud map. After obtaining the flow field information, use CATIA to improve the structure of the intake manifold, such as the size of the chamfer, the size of the aperture, and so on. After deriving thermal conditions, it is necessary to explain whether it is necessary to optimize the thermal field.

In this paper, after analyzing the thermal and flow fields of the intake manifold, the following conclusions are obtained: For the thermal field of the intake manifold, no optimization design is required due to the low temperature. In the intake manifold, there is an excessive pressure in the flow field and it is necessary to propose an optimization solution. This paper presents an improved optimization scheme for the air intake, grille and the first structural column. Finally, the comparison of the effect map before and after the optimization of the intake manifold is given, and the optimization scheme is given. In the end, the new intake manifold model was introduced into the CFD analysis software and it was found that all the pressures were improved and the pressure difference was reduced by about 20%. The stress on the intake manifold was improved. Due to insufficient conditions in all aspects, this article does not adopt steady flow experiments.

This paper provides a research method with considerable reference value for the optimal design of the intake manifold. The optimization idea of ​​the intake manifold mentioned in the article is generally applicable to flow field optimization. This research method is applied to the manifold of a diesel engine. Optimal design also has universal applicability.

Key words: intake manifold, 3D modeling, flow field calculation, analysis and optimization

目录

摘要 I

Abstract II

第1章 引言 1

1.1 研究背景与意义 1

1.2 国内外研究现状 2

1.2.1 现代优化技术的发展 2

1.2.2 国内研究现状 2

1.2.3 国外研究现状 3

1.3 研究主要内容 4

第2章 进气歧管模型的建立 6

2.1 三维模型的建立 6

2.2 网格模型的建立 7

2.3 结果提取 8

2.4 本章小结 8

第3章 进气歧管的CFD分析与计算 9

3.1 CFD技术介绍 9

3.2 确定边界条件和收敛方法 9

3.3 CFD仿真及分析 10

3.3.1 进气歧管热模拟 10

3.3.2 进气歧管流场模拟 11

3.3.3网格模型模拟计算和结果分析 13

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