摘 要

现阶段，石油与工业、农业、交通等方面息息相关，但是由于石油能源的紧缺与快速消耗，现已经成为各个国家争夺的关键性资源。而且由于汽车保有量的快速增长，内燃机燃用汽油、柴油产生大量排放会对环境造成很大的破坏并会威胁人们的身体健康。为了提高内燃机的热效率节约燃油，并且降低其污染物排放，全球内燃机研究者就内燃机新技术做出了许多新的突破。

由于柴油机压缩比很高，输出功率以及燃油经济性都高于汽油机，但是柴油机污染物排放较高，会对环境造成很大污染。本研究就此问题采用汽油/柴油双燃料模式，试图进一步提升柴油机性能，并且改善其污染物排放水平。

本研究基于较为成熟的KIVA4与CHEMKIN代码耦合方法，建模研究了在不同负荷下，不同混合比例的汽油/柴油混合燃料在柴油机中的燃烧过程。结果表明：

（1）在不同负荷条件下，由于汽油的十六烷值低且易蒸发，混合燃料燃烧滞燃期延长，空气与燃料有更多时间混合充分，前期混合燃料燃烧更为平稳，缸压下降；后期燃料燃烧快速且充分，燃烧累计释放的热量较纯柴油更高。

（2）较高质量分数（15%，20%）的汽油/柴油混合燃料对于提升柴油机性能与改善CO排放都有较好效果。但是在低、中等负荷下，纯柴油中直接掺入汽油的方法对于降低NO的排放并没有很好的作用。

关键词：柴油机；汽油/柴油混合燃料；排放特性；数值模拟；简化燃烧机理

Modeling on Blend Gasoline/Diesel Fuel Combustion in a Direct Injection Diesel Engine

Abstract

Nowadays, petroleum is closely related to industry, agriculture, and transportation. But due to the shortage and rapid consumption of petroleum energy, it has become a key resource for various countries to compete for. Moreover, due to the rapid growth of car ownership, the large amount of emissions from the internal combustion engines fueled with gasoline or diesel will cause great damage to the environment and threaten people's health. To improve the thermal efficiency of internal combustion engines, to save fuel, and to reduce their pollutant emissions, global internal combustion engine researchers have made many new breakthroughs in the new technologies for internal combustion engines.

Due to the high thermal efficiency and output power of diesel engines, as well as good durability and fuel economy, diesel engines have been increasingly used in heavy-duty vehicles. However, the high emission of NOx and PM from diesel engines will cause great pollution to the environment. This study adopts the blend gasoline/diesel fuel mode for this issue in attempt to further improve diesel engine performance and improve its pollutant emission levels.

This study is based on the coupled KIVA4 and CHEMKIN code. It was used to model the combustion process of blend diesel/gasoline fuel with different mixing ratios under different loads. The results show that:

(1) Under different load conditions, due to the low cetane number of gasoline and high latent heat of evaporation, the ignition delay of the combustion is extended. The air and fuel have much more time to fully mix together at earlier-stage. In consequence, the mixed fuel burns more smoothly and the cylinder pressure decreases. At later-stage, fuel fast and completely burns out; thus, the cumulative heat released during combustion is higher than that fueled with pure diesel.

(2) The higher ratio (15%, 20%) of blend gasoline/diesel fuel has a positive effect on improving diesel engine performance and reducing CO emissions. However, the blend of gasoline in diesel at low and moderate loads does not have a good impact on reducing NO emissions.

Keywords: Diesel engine; Blend gasoline/diesel fuel mode; Fuel emission characteristics; Numerical simulation; Simplified combustion mechanism

目录

摘要 I

ABSTRACT II

第一章 绪论 1

1.1课题研究背景及意义 1

1.2柴油机简介 2

1.3 污染物产生原理 2

1.4 柴油机排放控制技术 3

1.5 本文主要研究内容 4

第二章 数值模拟方法 6

2.1 KIVA4-CHEMKIN代码介绍 6

2.2 计算网格介绍 7

2.3 化学反应机理 8

2.4 模型验证 9

2.5 本章小结 11

第三章 掺混汽油对柴油机性能及排放影响分析 12

3.1 性能表现 13

3.2 燃烧过程分析 14

3.2.1 缸压变化分析 14

3.2.2 热释放率分析 16

3.3 排放分析 18

3.3.1 NO排放分析 18

3.3.2 CO排放分析 20

3.4 经济性分析 22

3.5 本章小结 22

第四章 总结与展望 23

4.1 全文总结 23

4.2工作展望 24

参考文献 25

致谢 28

第一章 绪论

1.1课题研究背景及意义

自第一次工业革命以来，随着科学技术的快速发展，人们生活水平有了质的飞跃，但伴随着的却是巨大的能源消耗与环境污染。现阶段能源危机与环境问题已经成为威胁人类生存发展的重大问题。现阶段，随着全球汽车保有量的快速增长，石油的消耗也急剧上升，据统计，2006年原油占世界能源消耗总量的36.4%，分别超出煤炭和天然气约11%与24%^[1]。世界能源展望组织估计世界可开采的原油大约为13000亿桶，而世界能源消耗将以每年2%的速率增长，原油的消耗水平在2030年将达到6100万桶/天，而2015年的水平仅为4600万桶/天^[2]，这表明原油将在本世纪中期前开采完毕。现阶段，石油资源已经成为各国争夺的关键性资源。

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