【作者】 王真；

【导师】 帅石金；

【作者基本信息】 清华大学 ， 动力工程及工程热物理， 2010， 硕士

【摘要】 甲醇作为一种汽油替代燃料,具有资源丰富、价格便宜和燃烧性能良好等优势,但甲醇燃烧产生的未燃甲醇、甲醛等非常规排放,对人体及环境会造成较大危害,不容忽视。本课题基于国家863项目“甲醇灵活燃料汽车技术开发”,主要针对不同比例甲醇汽油在普通汽油机及汽油车上的应用,研究其燃烧性能以及常规与非常规排放特性。首先,进行不同比例甲醇汽油的油耗和排放性能发动机台架试验。在一台进气道多点电喷汽油机(JL479QA)上,未作任何调整,直接燃用汽油、M5、M15和M30低比例甲醇汽油,采用AVL傅里叶变换红外光谱多组分分析仪(SESAM-FTIR)测量了低比例甲醇汽油的排放成分。结果表明:在发动机未经调整情况下,低比例甲醇汽油能控制在闭环,可以较好地适用于普通汽油机,在相同输出功率条件下,等效油耗值略有下降;外特性开环控制下,空燃比向偏稀移动,功率下降。对于高比例甲醇汽油M85,不经过任何调整已经较难使发动机正常工作,通过改变标定的目标空燃比来增大喷油脉宽,使其与汽油的实际空燃比一致,经过调整后的M30和M85外特性下动力与汽油相近,等效油耗随着甲醇比例的增大略有降低。无论是汽油、低比例M5、M15、M30,还是高比例M85,催化剂前的THC随着甲醇比例的增大逐渐降低,NOx和CO差别不大。经过三效催化剂后,只要保持在化学计量空燃比附近,催化剂都能达到很高的转化效率。对于非常规排放,甲醇汽油中未燃甲醇以及甲醛的排放随着甲醇比例的增加而增加,但通过三效催化剂后能达到与汽油一致的低水平排放。其次,对低比例甲醇汽油M10、M20、M30应用于普通汽油车的瞬态冷起动排放特性进行了研究。按照国III工况测试循环,分别进行了25℃常温冷起动和-7℃低温冷起动试验。结果表明:无论在低温冷起动还是常温冷起动下,低比例甲醇汽油的常规排放与汽油相近,催化剂起燃后能将THC、NOx和CO控制在较低的水平,排放主要集中在起动的初始阶段。低温冷起动相比常温冷起动会产生更多的THC排放。对于甲醇汽油的非常规排放,甲醇和甲醛的排放随着燃料中甲醇比例的增大而增加,催化剂后的排放仍然集中在初始阶段,一旦催化剂进入正常工作,甲醇和甲醛都能被很好地转化。更多还原

【Abstract】 Methanol has many advantages as an alternative gasoline fuel. However, the unregulated emissions like formaldehyde from the methanol combustion will do great harm to human health and environment. This study was based on the national 863 project of“Development of methanol flexible fuel vehicle technologies”, focusing on the combustion performance and unregulated emissions of methanol-gasoline fuels.First, the specific fuel consumption and emission performance of different methanol-gasoline fuels were tested on an engine test bench. The engine used was JL479QA and AVL SESAM-FTIR was used to measure the emissions. M5, M15 and M30 together with gasoline were tested on the unadjusted engine. The results show that for the same power output, the specific energy consumptions of the low-proportion methanol-gasoline fuels are a little bit lower than that of gasoline. But the power decreases in the engine speed characteristics because of the increase of A/F ratio. The gasoline needs to be adjusted with high proportion of methanol-gasoline blends like M85. The speed characteristics are similar to that of gaslone after being adjusted. THC gets lower with more methanols in the fuel, while NOX and CO are similar with gasoline. Methanol and formaldehyde emmsions get higher with the increase of methanols in the fuel. As long as the A/F ratio is near the stoichiometry, the TWC (Three Way Catalyst) has high conversion efficiency for all the emissions.Secondly, the cold start application with M10, M20 and M30 both under ambient temperature 25°C and low temperature -7°C was studied. The results show that the regular emissions of the methanol-gasoline fuels are similar to that of gasoline. Methanol and formaldehyde emmsions still get higher with the increase of methanols in the fuel. The initial cold start stage contributes the major of total emission. But once the catalyst is lit off, TWC has a high convertion efficiency of both regulated and unregulated emissions.更多还原