【作者】 项春艳；

【导师】 姚春德；

【作者基本信息】 天津大学 ， 动力机械及工程， 2008， 硕士

【摘要】 作为汽车的代用燃料,甲醇由于生产成本低,生产技术成熟等原因在我国有着广泛的应用前景,但是甲醇燃料的使用会使发动机尾气中甲醛排放增多。甲醛是较高毒性的物质,对人体和大气环境都存在危害。因此,了解与掌握内燃机尾气中的醛类排放特性,对控制甲醛排放、推广醇类燃料的推广使用具有重要意义。本课题采用酸性条件下的2,4-二硝基苯肼吸收尾气中的甲醛,生成甲醛腙,利用气相色谱仪分析出甲醛腙的含量,经过计算从而最终得出尾气中甲醛的含量。基于此原理建立了一套内燃机尾气甲醛检测装置,并根据大量实验结果对比,确定了采样系统以及色谱的参数。利用此检测装置和方法本课题着重研究了柴油/甲醇组合燃烧方式(diesel/methanol compound combustion, DMCC)和掺甲醇汽油尾气中甲醛排放规律,通过大量试验对比,发现发动机负荷、甲醇替代率、喷射方式、催化转化器、排气温度对尾气中甲醛排放都存在影响。研究结果表明: DMCC燃烧方式的尾气中甲醛排放浓度是原机的10～30倍;在相同转速和相同甲醇替代率时,低负荷下甲醛排放最高,中负荷时甲醛排放最少,高负荷时甲醛排放居中;在中低负荷时,随着甲醇替代率的升高,甲醛生成量呈现递增趋势。在高负荷高甲醇替代率时,甲醛排放则略有下降;相同工况点,顺序喷射的尾气中甲醛含量要低于连续喷射;催化转化器对尾气中甲醛的消除效果与排气温度有很大关系。当排气温度低于300℃或高于410℃时,催化后甲醛会减少;当排气温度300℃<T<410℃时,催化后甲醛反而会增加。对汽油机燃用93#汽油与不同甲醇汽油配比燃料(M10、M20和M30)时的醛类排放进行了对比分析,结果表明:与燃用纯汽油相比,掺烧甲醇时尾气中的甲醛排放明显增加。M10、M20可以达到M0的2倍,而M30增加幅度最大,可以达到M0的近7倍;三效催化转化器可以很好地消除尾气中甲醛排放,经过催化处理后,不同汽油甲醇配比燃料的甲醛排放均明显降低,都可以被控制在接近零排放的水平。更多还原

【Abstract】 Methanol as alternative fuel for vehicles has a broad prospect in China because of its low producing cost and formed production technique. However, Formaldehyde emission of engine powered by methanol is known for strong carcinogenicity,and it can harm atmospheric environment and human health.Hence,generalize the methanol fuel so as to controlling the emission concentration of aldehyde is of great significance.A method is provided to determinate formaldehyde in the engine exhaust: Formaldehyde is absorbed by the acidic saturated solution of 2,4-dinitrophenyl hydrazine (DNPH) and converted to its hydrazone, the hydrazone is then extracted with CS2 and determinated using Gas Chromatography (GC). Based on theory mentioned above ,a sampling system is designed to measure formaldehyde emitted from engine.The measure method is applied to determine the formaldehyde emission from a DMCC engine, It is revealed by experiments that load、methanol proportion、methanol injection styles、catalytic converter、exhaust temperature affect formaldehyde emission characteristic from DMCC engine.The results showed as follows: the formaldehyde concentration from DMCC engine is about 10～30 times higher than that of diesel engine; the formaldehyde concentration is the highest at low-load, the lowest at medium-load at same rotate speed and methanol proportion; with the increasing of methanol proportion, the formaldehyde in exhaust is increasing in low load and middle load; the formaldehyde emission of Sequential Fuel Injection mode is less than that of Continuous Fuel Injection style at same work condition; the exhaust temperature is a key factor for the catalytic converter’s effect. When the exhaust temperature is lower than 300℃or higher than 410℃, the formaldehyde emission is decreased by the catalyst, but it would increased if the exhaust temperature between 300℃to 410℃.Besides, this measure method determine the formaldehyde emission from a gasoline engine powered by M0、M10、M20、M30,respectively. The results showed as follows: the formaldehyde concentration of methanol/gasoline engine is 2~7 times higher than that of gasoline engine, but it is decreased by catalytic converter obviously to approach ultra-low emission.更多还原