缸内直喷点燃式甲醇发动机非常规排放仿真研究

发布时间：2018-07-06 10:28

本文选题：缸内直喷 + 甲醇发动机　；参考：《吉林大学》2015年硕士论文

【摘要】：随着能源危机和环境危机日益加剧，寻求一种清洁的可替代燃料迫在眉睫。经过多年的探索，人们开始将目光转向了甲醇。甲醇,化学分子式为CH3OH，具有和汽油、柴油媲美的储存运输和应用方面的优势，同时在常规排放性能方面比传统燃料更优，所以甲醇被公认为是21世纪最具发展潜力的代用燃料。除了以上种种优势，甲醇燃料的应用也面临不少问题亟待解决，，特别是甲醇燃料带来的非常规排放问题，严重制约了甲醇燃料的大规模应用。本文以一台经柴油机改装的缸内直喷点燃式甲醇发动机为原型，通过三维建模软件Pro/E对模型进行精简优化并将模型以*.stl格式导出，采用AVL-FIRE软件对模型进行前处理，使用AVL-FIRE软件耦合甲醇详细氧化机理进行模拟计算，用仿真计算得到的缸压曲线与实验所测的缸压曲线进行对比验证以确保仿真计算的准确性。通过模拟计算研究进气温度（过量空气系数）、点火正时、喷油正时对冷启动和稳态工况非常规排放影响，得到以下结论：一、冷启动工况： 1.提高进气温度能促进甲醇雾化及蒸发，改善缸内混合气分布，提高缸内混合气燃烧质量，有效降低未燃甲醇和甲醛排放；当进气温度从283K提高到313K未燃甲醇和甲醛的排放能够得到极大改善；当进气温度达到313K继续提高进气温度对降低未燃甲醇和甲醛的排放效果不明显。 2.推迟点火正时，缸内混合气分布恶化，燃烧恶化，未燃甲醇和甲醛排放升高；当点正时由20°CA BTDC推迟到11°CA BTDC未燃甲醇和甲醛排放增加不明显；当点火正时由11°CA BTDC推迟到8°CABTDC时未燃甲醇和甲醛排放会急剧增加。 3.推迟喷油正时，缸内混合气分布得到优化，燃烧更加充分，有效降低未燃甲醇和甲醛排放；当喷油正时为57°CA BTDC时未燃甲醇和甲醛排放最高，随着喷油正时推迟未燃甲醇和甲醛排放呈递减趋势；但是当喷油正时为49°CA BTDC时由于缸内燃烧温度维持在1000K左右会促进未燃甲醇不完全氧化成甲醛使得甲醛排放达到峰值，当喷油正时进一步推迟甲醛排放明显下降。二、稳态工况： 1.增大过量空气系数，不利于混合气形成，燃烧恶化，未燃甲醇和甲醛排放增加；当过量空气系数由λ=1.5增加到λ=2.5未燃甲醇甲醛排放增加不明显；当过量空气系数增加到λ=3.0未燃甲醇和甲醛排放急剧增加。 2.推迟点火正时，缸内混合气分布恶化，燃烧恶化，未燃甲醇和甲醛排放增加；当点火正时由20°CA BTDC推迟到11°CA BTDC未燃甲醇和甲醛排放有轻微增加；当点火正时推迟到8°CABTDC未燃甲醇和甲醛排放急剧增加。 3.推迟喷油正时，能有效改善缸内混合气分布，燃烧质量提高，未燃甲醇和甲醛排放显著降低；当喷油正时为57°CA BTDC时未燃甲醇和甲醛排放十分高；当喷油正时推迟到53°CA BTDC未燃甲醇和甲醛排放有显著降低；当喷油正时进一步推迟未燃甲醇和甲醛排放降轻微降低。
[Abstract]:With the increasing of energy crisis and environmental crisis , it is urgent to seek a clean alternative fuel . After many years of exploration , people have begun to turn their attention to methanol . Methanol and chemical molecular formula CH3OH have the advantages of storage transportation and application as well as gasoline and diesel oil . At the same time , methanol is recognized as a substitute fuel with the most development potential in the 21st century . In addition to the above advantages , the application of methanol fuel has many problems to be solved , especially the problem of unconventional discharge caused by methanol fuel , which seriously restricts the large - scale application of methanol fuel .

In this paper , a diesel engine modified in - cylinder direct injection ignition methanol engine is used as a prototype , and the model is optimized by three - dimensional modeling software Pro / E and the model is derived in the form of * . stl . The simulation calculation is carried out on the model by using the software Pro / E . The cylinder pressure curve obtained by the simulation is compared with the cylinder pressure curve measured by the experiment to ensure the accuracy of the simulation calculation .

I . Cold start working condition :

1 , increasing the intake air temperature , promoting methanol atomization and evaporation , improving the distribution of the in - cylinder mixture , improving the combustion quality of the in - cylinder mixture , and effectively reducing unburned methanol and formaldehyde emission ;
When the inlet temperature is increased from 283K to 313K , the discharge of unburned methanol and formaldehyde can be greatly improved ;
When the intake air temperature reaches 313K , the effect of increasing the intake air temperature on reducing unburned methanol and formaldehyde is not obvious .

2 . When the ignition timing is retarded , the distribution of the in - cylinder mixture deteriorates , the combustion deteriorates , the unburned methanol and the formaldehyde emission increase ;
When the ignition timing was retarded from 20 掳 CA BTDC to 11 掳 CA BTDC unburned methanol and formaldehyde emission increased obviously ;
Unburned methanol and formaldehyde emissions increase sharply when the ignition timing is retarded from 11 掳 CA BTDC to 8 掳 CABTDC .

3 . When the fuel injection timing is delayed , the distribution of the in - cylinder mixture is optimized , the combustion is more fully , the unburned methanol and formaldehyde emission are effectively reduced ;
When the fuel injection timing was 57 掳 CA BTDC , unburned methanol and formaldehyde were the highest , and the emission of unburned methanol and formaldehyde was decreased with the fuel injection timing .
However , when the fuel injection timing is 49 掳 CA BTDC , the combustion temperature in the cylinder is maintained around 1000K to promote the incomplete oxidation of unburned methanol to formaldehyde so that the formaldehyde emission reaches the peak value , and the emission of formaldehyde is further delayed when the injection timing is positive .

II . Steady - state operating conditions :

1 . Increasing the excess air coefficient is not conducive to the formation of the mixed gas , the combustion deteriorates , the unburned methanol and the formaldehyde emission increase ;
When the excess air coefficient increases from 位 = 1.5 to 位 = 2.5 , the formaldehyde emission of unburned methanol is not obvious ;
When the excess air factor increases to 位 = 3.0 unburned methanol and formaldehyde emissions sharply increase .

2 . When the ignition timing is retarded , the distribution of the in - cylinder mixture deteriorates , combustion deteriorates , unburned methanol and formaldehyde emission increase ;
When the ignition timing was retarded from 20 掳 CA BTDC to 11 掳 CA BTDC unburned methanol and formaldehyde emissions slightly increased ;
When the ignition timing was retarded to 8 掳 CABTDC unburned methanol and formaldehyde emissions sharply increased .

3 . When the fuel injection timing is delayed , the in - cylinder mixed gas distribution can be effectively improved , the combustion quality is improved , the unburned methanol and the formaldehyde emission are obviously reduced ;
Unburned methanol and formaldehyde emissions were very high when the fuel injection timing was 57 掳 CA BTDC ;
When the injection timing was retarded to 53 掳 CA BTDC unburned methanol and formaldehyde emission decreased significantly ;
A slight decrease in unburned methanol and formaldehyde emissions was further delayed when the injection timing was positive .
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK401

【参考文献】