【作者】 李方成；

【导师】 宋崇林；

【作者基本信息】 天津大学 ， 动力机械及工程， 2010， 博士

【摘要】 针对醇类燃料羰基类化合物排放量较高的问题,本文开展了柴油机燃用醇类/柴油混合燃料羰基化合物的排放特性和生成机理的研究。利用衍生化法和高效液相色谱技术对羰基类化合物进行收集和分析;针对醇类/柴油混合燃料羰基化合物的排放特性和生成历程进行了研究;建立了甲醇/柴油混合燃料喷雾过程和燃烧过程的多维模型,开展了相应的醛类化合物理论研究与分析,论文的研究成果和主要结论如下:1、以DNPH固体吸附和高效液相色谱技术为手段,对醇类燃料燃烧过程及发动机尾气中羰基化合物的检测技术进行了研究,建立了系统的采集、分析方法,为研究发动机燃烧过程中羰基化合物的演化历程及排放特性奠定了基础。2、通过测定负荷特性上的羰基类污染物的排放量,研究了醇类掺烧比例、发动机转速及负荷对羰基类污染物排放特性的影响规律。研究结果发现,不论燃用纯柴油还是醇类/柴油混合燃料,羰基类污染物中甲醛和乙醛的含量最高,掺烧比例、发动机转速及负荷对各种羰基类化合物排放影响较大。3、研究了纯柴油(M0)、两种不同掺烧比例的甲醇/柴油混合燃料(M8、M13)、两种不同乙醇掺烧比例的乙醇/柴油混合燃料(E10、E20)对发动机燃烧过程的影响和燃烧过程中羰基化合物(醛、酮)的生成规律。研究结果表明,柴油机燃用醇类/柴油混合燃料后,缸内最高温度升高,最大爆发压力提高;同时,柴油机的燃烧始点提前,急燃期的缸内压力、缸内温度和放热率升高速率加快。燃用醇类/柴油混合燃料,在任意曲轴转角下甲醛和乙醛的含量最大,其次是丙烯醛、丙醛、丁醛、环己酮、对甲基苯甲醛和己醛,这八种羰基化合物约占总羰基化合物的90%,其余醛、酮化合物生成量较小,无明显变化规律。4、开展了甲醇/柴油混合燃料以及纯柴油喷雾和燃烧机理的理论研究和模拟计算,并与试验结果进行对比。计算及实验结果表明,甲醇/柴油混合燃料有助于改善缸内混合气的混合,混合燃料的湍动能明显提高,混合燃料的平均燃烧温度略高,有助于燃烧的迅速发展,提高燃烧效率,降低不完全燃烧化合物产物的生成。由于混合燃料的高气化潜热和较低的喷注贯穿度,使得燃烧壁面的淬熄层中产生大量的非常规排放物,并随缸内已燃气体排出,造成发动机尾气中羰基化合物的排放量高。更多还原

【Abstract】 Due to the presence of carbonyl compound emissions in higher concentration for engines fueled with methanol/ethanol-diesel blends, this study focuses on the emission characteristics and formation mechanism of carbonyl compounds (CBCs) in diesel engine fueled with alcohols-diesel blends. The CBCs were gathered and analyzed by the method of 2, 4-dinitrophenylhydrazine (DNPH) derivative and high-performance liquid chromatography, and the emission characteristics and formation history of CBCs for alcohols-diesel blends were investigated. Based on the models of spray and combustion, the numerical simulation during combustion process was carried out for the CBCs of methanol/diesel blends. The major achievements and conclusions of this dissertation are listed as follows:1. Based on DNPH cartridge and HPLC, the detection of CBCs during combustion process and in the exhaust emissions from engines fueled with alcohols-diesel blends were studied, and the sampling and analysis strategies were established systematically. These paved the way to study the formation history of CBCs in engine combustion process and CBCs emission characteristics.2. By the means of measuring the CBC emissions during the constant speed/varying load tests, the influence of alcohols/diesel ratio, engine speed and load on the CBC emissions was investigated. The engine experimental results indicated that for either pure diesel fuel or alcohols/diesel blends, formaldehyde and acetaldehyde were most abundant in CBC emissions. The alcohols/diesel ratio, engine speed and load exhibited profound effects on CBC emissions.3. The influences of pure diesel (M0), two kinds of methanol-diesel blends (M8, M13), two kinds of ethanol-diesel blends (E10, E20) on the engine combustion process and CBC formation history were studied. The experimental data indicated that the introduction of methanol/ethanol-diesel blends in diesel engine led to an increase in both highest cylinder pressure and temperature. In addition, the ignition timing was advanced; the pressure and temperature increase rate accelerated; and heat release rate was improved. For the alcohols-diesel blends, formaldehyde and acetaldehyde were mostly abundant in CBCs at different crankshaft angle during combustion process, followed by acrolein, propionaldehyde, butyraldehyde, cyclohexanone, p-tolualdehyde and hexaldehyde. And these eight kinds of CBCs mentioned above accounted for 90% of total CBC emissions. Other CBCs were occasionally present in the samples and showed unobvious variation trends.4. The spray and combustion of both pure diesel and methanol/diesel blends were studied by means of theoretical analysis and numerical simulation, and the results obtained were also compared with experimental data. The experimental data showed that the methanol/diesel blends could improve the mixture quality and turbulent kinetic energy in the cylinder, and the average combustion temperature for the methanol/diesel blends was higher than that for pure diesel fuel. These would help to accelerate the combustion development, boost the combustion efficiency and decrease the formation of incomplete combustion products. Due to high latent heat of vaporization and short injection penetration distance of the methanol/diesel blends, a large amount of CBCs would originate from quenching layer around cylinder wall. The incomplete combustion compounds stayed in the quenching layer emitted with other combustion products from the engine, and caused higher CBC emission in the engine exhaust pipe.更多还原