华中科技大学硕士学位论文
摘要
随着我国经济社会的快速发展，国内对汽车的需求量呈爆发式增长，与此同时，环境污染和能源危机问题日趋严重，我国原油对外依存度超过65%。这对我国经济的可持续发展和能源安全来说都是一个极大的隐患。汽车消耗了大量的石油资源，汽车尾气则是造成环境污染的主要因素之一，寻求一种更加清洁、高效的替代燃料成为了汽车发动机的发展方向之一。
甲醇的理化性质与汽油比较接近，并且其辛烷值远高于汽油，允许发动机提高压缩比，从而提高动力性和燃油经济性；且甲醇的汽化潜热超过汽油的3倍，进气预混时能有效降低混合气的温度，从而抑制爆震。甲醇来源广泛，可以再生，在我国可通过丰富的煤炭资源制取，这是解决我国动力燃料紧缺的有效途径。
根据甲醇燃料的特点，对发动机的燃料供给系统进行了改装，并根据一维仿真计算结果，除了原机9.5的压缩比之外，选取了11和12两个压缩比方案。以台架试验的方式，对发动机分别燃用汽油与甲醇、以及不同压缩比对甲醇发动机动力性、经济性、排放特性和燃烧过程的影响进行了研究。
试验结果表明：原汽油发动机在燃用甲醇后，提升了动力性、改善了经济性。发动机燃用甲醇及提高压
缩比后，压力升高率和缸内最大爆发压力提高，且由于甲醇辛烷值较高，无需大幅推迟点火以抑制爆震。因此，即使在较大负荷时，也可以保持较高的循环热效率。发动机燃用甲醇后，CO的排放变化不大；未燃HC最多降低超过90%；NOx小负荷时大幅降低，大负荷时略有降低。
压缩比对甲醇发动机燃烧特性具有显著影响，压缩比为12时，发动机能耗率相对于原汽油机可降低约20%，最高有效热效率由31.02%提高到了39.02%；最大扭矩提高7.58%，最大功率提高4.03%。大负荷工况需要推迟点火，以降低发动机机械负荷和热负荷，这限制了压缩比的进一步提高。提高压缩比后，CO排放呈下降趋势；压缩比提高到11后，未燃HC排放有所下降，但压缩比为12时，HC排放量和压缩比为11时相当；随着压缩比的提高，NOx排放呈上升趋势，但提高压缩比后NOx的排放仍低于原汽油机。
关键词：甲醇发动机压缩比仿真计算性能试验
华中科技大学硕士学位论文
ABSTRACT
With the rapid development of China's economy and society, the demand for automobiles in our country is increasing. Meanwhile, the problem of environmental pollution and energy crisis is becomi
ng more and more serious. Our dependence on foreign oil is more than 65%. This is a great This is a great risk for energy security and sustainable development of national economy. The automobile consumes a large amount of petroleum resources, and automobile exhaust is one of the main factors that cause environmental pollution. It is one of the development direction of automobile engine to seek a cleaner and more efficient alternative fuel.
The physical and chemical properties of methanol is close to that of gasoline, and its octane number is much higher than that of gasoline, which allows the engine to increase the compression ratio, s so as to improve the power and economy of the engine. The latent heat of vaporization of methanol is about 3 times that of gasoline, which can effectively reduce the temperature of the mixture, thus inhibiting the knock. Methanol has a wide range of sources and can be regenerated. It can be made through a wealth of coal resources. This is an effective way to solve the shortage of power fuel in China.
According to the characteristics of methanol, the fuel supply system of engine is modified. According to the simulation results, in addition to the compression ratio of the original 9.5, the 11 and 12 are selected as the two compression ratio program. The characteristics of gasoline and methanol, and the effects of different compression ratios on the engine power, economy, combustion and emission
characteristics are investigated in the way of bench test.
The results show that the gasoline engine has improved its power and economy after burning methanol. When the engine is fueled with methanol and the compression ratio is increased, the pressure rise rate and the maximum explosion pressure in the cylinder are increased, and because of the high octane number of methanol, there is no need to significantly delay the ignition to suppress knocking. Therefore, even at a relatively large load, it is possible to maintain a high cycle thermal efficiency. When the engine is fueled
华中科技大学硕士学位论文
with methanol, the emission of CO is almost not changed, the unburned HC is reduced by up to more than 90%, and NOx is significantly reduced at low load and slightly at large load.
The compression ratio has a significant effect on the combustion characteristics of the methanol engine. When the compression ratio is 12, the engine energy consumption can be reduced by about 20% compared with the original gasoline engine, the maximum effective thermal efficiency is increased from 31.02% to 39.02%, the maximum torque is increased by a factor of 7.58%, and the maximum power is increased by 4.03%. It is necessary to delay ignition to reduce the mechanical loa
d and heat load, which limits the further improvement of compression ratio. With the increase of compression ratio, CO emission decreased. When the compression ratio is increased to 11, the unburned HC emission decreases, but when the compression ratio is about 12, the HC emission is close to the compression ratio of 11. With the increase of the compression ratio, the NOx emission showed an upward trend, but the NOx emission was still lower than that of the original gasoline engine.
Key words: Methanol Engine Compression ratio Simulation
Performance test
华中科技大学硕士学位论文
目录
摘要............................................................................................................... II 1 绪论
1.1 研究背景及意义 (1)
1.2 甲醇及其特性 (2)
1.3 甲醇作为汽车发动机代用燃料的应用和研究进展 (5)
1.4 本文研究内容 (12)
2 甲醇发动机仿真计算模型的建立
2.1 GT-POWER简介 (13)
2.2 仿真模型的建立 (13)
2.3 仿真模型的验证 (19)
2.4 本章小结 (21)
3 仿真结果及压缩比方案的对比分析
3.1 不同压缩比下的外特性分析 (22)
3.2 改变压缩比之后常用转速下的负荷特性 (24)
3.3 压缩比对缸内燃烧过程的影响 (26)
3.4 本章小结 (33)
4 发动机试验台架设计与构建
4.1 发动机试验台架和测试设备 (34)
华中科技大学硕士学位论文
4.2发动机及试验台架的改造 (41)
4.3 本章小结 (43)
5 发动机燃用汽油与甲醇性能对比试验
5.1 试验内容 (44)
5.2 发动机动力性 (45)
5.3 发动机经济性 (46)
5.4 发动机燃烧特性分析 (48)
5.5 发动机尾气排放特性分析 (51)
5.6 本章小结 (55)
6 全文总结及展望
6.1 全文总结 (56)
汽车改甲醇
6.2 工作展望 (57)
致谢 (58)
参考文献 (59)
附录1 攻读硕士学位期间发表论文目录 (63)
附录2 磨合工况 (64)