论文总字数：22561字

摘 要

随着排放法规的日益严格，发动机节能减排的技术在不断进步。燃料的雾化效果好坏对发动机的燃烧与排放有重要影响。本次探究主要借助有限元仿真计算软件Fluent仿真计算燃料通过低压喷嘴雾化的过程，希望弄清低压喷嘴的雾化机理。

本文以低压喷射发动机的雾化过程为主要研究对象，分别通过对针阀内的一次雾化和定容燃烧弹内的二次雾化进行仿真计算，通过横向对比5.5bar、6.5bar、7.5bar三种阀内压力下的一次雾化情况，研究一次雾化的机理，并且在其他数据的参考下尝试解答了这些机理的产生原因。然后结合已有工程经验选择一个5.5bar的阀内压力情况做纵向的二次雾化机理研究，总结燃料二次雾化的发展情况。最后结合两次雾化依据贯穿距离、喷雾锥角和SMD等评价指标，初步探究了低压喷嘴的雾化机理，给出了本次探究得到的结论，同时又对相关方向做了展望。仿真结果显示，阀内压力越小一次雾化效果越好，5.5bar时燃料的二次雾化有滞后现象，但雾化的效果还不错。

关键词：低压空气辅助 二次雾化 Fluent

Simulation study on atomization mechanism of low pressure nozzle

Abstract

The effect of fuel atomization has an important impact on the combustion and emissions of the engine. This investigation mainly uses the finite element simulation calculation software Fluent to simulate the process of fuel atomization through the low-pressure nozzle, hoping to find the atomization mechanism of the low-pressure nozzle.

This article takes the atomization process of the low-pressure injection engine as the main research object, through the simulation calculation of the primary atomization in the needle valve and the secondary atomization in the fixed-volume incendiary bomb respectively, through the horizontal comparison of 5.5bar, 6.5bar, 7.5bar One atomization situation under three kinds of valve pressure, the mechanism of one atomization was studied, and the causes of these mechanisms were tried to be solved under the reference of other data. Then combined with the existing engineering experience, a 5.5 bar valve pressure situation was selected to conduct a longitudinal secondary atomization mechanism study, and the development of the secondary atomization of fuel was summarized. Based on other parameters obtained, an attempt was made to answer why this development occurred. Finally, combining the evaluation indexes such as penetration distance, spray cone angle and SMD of the two atomizations, the atomization mechanism of the low-pressure nozzle was preliminarily explored, and the conclusions obtained in this investigation were given, and the relevant directions were also prospected. The simulation results show that the smaller the pressure in the valve, the better the primary atomization effect, and the secondary atomization of fuel at 5.5 bar has a lag, but the effect of atomization is not bad.

Key Words：Low-pressure air-assisted; Secondary atomization; Fluent

目录

摘 要 I

Abstract II

第一章 绪论 1

1.1 背景 1

1.2 发动机的燃烧技术 1

1.2.1 雾化效果的评价指标 1

1.2.2 雾化的影响因素 2

1.3 低压喷射发动机 2

第二章 计算理论依据 4

2.1 能量方程 4

2.1.1 积分形式的能量方程 4

2.2 质量方程 5

2.2.1 积分形式的连续方程 5

2.2.2 微分形式的连续方程 5

2.3 动量方程 6

2.3.1 积分形式的动量方程 6

2.3.2 积分形式的动量矩方程 6

2.3.3 微分形式的动量方程 6

2.4 湍流模型 7

2.4.1 湍流模型的选取 7

2.4.2 所选湍流模型的介绍 8

2.5 离散相模型 8

2.5.1 离散项模型的创建 8

2.5.2 离散项模型的求解过程 8

2.5.3 颗粒的运动方程 9

第三章 建模 10

3.1 3D模型 10

3.1.1 建模软件介绍 10

3.2 网格划分 12

3.3 仿真参数的设置 16

第四章 计算结果与分析 17

4.1 一次雾化 17

4.1.1 0.5ms的数据对比分析 17

4.1.2 1.0ms的数据对比分析 21

4.1.3 不同阀内压力对一次雾化的影响 25

4.2 二次雾化 26

4.2.1 仿真计算对象的选择 26

4.2.2 针阀开启0.5ms 26

4.2.3 针阀开启1.0ms 28

4.2.4 针阀开启1.5ms 29

4.2.4 针阀开启2.0ms 30

4.2.5 整个二次雾化过程分析 32

第五章 总结与展望 34

5.1 总结 34

5.2 经济性分析 34

5.3 展望 35

参考文献 36

致谢 39

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