【作者】 程传辉；

【导师】 姚春德；

【作者基本信息】 天津大学 ， 动力机械及工程， 2005， 硕士

【摘要】 柴油机作为热效率最高的车用发动机,一直受到人们的高度重视,现代内燃机比传统内燃机虽然已有很大的进步和完善,但近几年,世界各国制定的日益严格的排放法规又对柴油机的研究提出了新的挑战。寻求清洁有效的替代燃料是解决这一问题的主要途径,同时又可以缓解石油短缺危机。甲醇是一种较清洁的替代燃料,不仅含氧量高、燃烧充分、有害排放物少,而且我国是一个煤资源很丰富的国家,以煤制取甲醇的技术以较成熟,生产成本也较低,因此,甲醇是内燃机较理想的替代燃料之一。在柴油机上燃用甲醇能有效地降低碳烟和NOx的排放,因此,柴油机燃用甲醇的技术得到了人们广泛的重视。前期研究表明,柴油/甲醇组合燃烧模式能成功的应用到柴油机上,实现同时降低NOx和碳烟排放,同时替代一部分柴油燃料,但是发现应用柴油/甲醇组合燃烧模式后,发动机的HC和CO排放明显升高。为了降低升高的HC和CO排放量,提出了使用氧化催化转化后处理技术。在一台改造过的柴油机上实现了柴油/甲醇组合燃烧模式,利用自主开发的一套控制系统控制喷射的甲醇量和喷射时刻,用十三工况循环等方式测量全面地检测了纯柴油、柴油/甲醇组合燃烧催化器前后的NOx、HC和CO的浓度以及微粒排放量,主要研究了在该模式下运行的发动机的排放性能及废气经氧化催化器后的净化效果,分析了甲醇的氧化机理和微粒的形态特征。试验结果表明,和纯柴油模式相比,柴油/甲醇组合燃烧模式的动力性和经济性都有所提高,排气温度有所下降;NOx和碳烟排放下降幅度较大,NOx下降平均达到41%,而碳烟排放降低幅度达到50%左右。但是,HC和CO排放增加较多,微粒比排放量也有所增加。经过催化氧化后,HC和CO得到了极大的降低,和原机相比下降幅度分别达47%和70%,微粒经氧化后比原机也有所下降。表明柴油/甲醇组合燃烧经采用催化转化器后,废气质量得到全面的改善,打破了传统柴油机在同时降低NOx-微粒时的权衡关系。另外,柴油/甲醇组合燃烧方式在一定程度上也缓解柴油机对石油资源的依赖,具有重要的应用价值和实际意义。更多还原

【Abstract】 Nowadays, diesel engines have been established as the most efficient of all the engines, which convert energy from hydrocarbon fuels into work.For this reason,it has received much attention,and has been the subject of numerous investigations in recent years. Modern engines have more remarkably improved on combustion and emissions than traditional engines. But the tightening of recent and future exhaust emission limits for diesel engines challenge our investigation. In order to compensate shortage of fossil fuel and reduce the atmospheric pollutants emitted by I.C. engines, it is worthwhile to assess the suitability of clean burning fuels. Methanol offer the most promising substitutes for petroleum as engines fuels at present because it contains oxygen up to 50%, can be completely burned in cylinder of engines and has low pollution emissions. Additionally, coal is abundance in China and coal-to-methanol technology is practicable because of its low cost. The methanol-fueled diesel engine can considerably depress smoke density and Oxides of Nitrogen (NO_x) emissions. Therefore, the investigation of diesel engines fuelled with methanol has been attented.Previous research results showed that diesel/methanol compound combustion (DMCC) mode could be successfully applied to diesel engines and promised reduction of smoke and NOx emissions simultaneously and replaced part of diesel fuel. But we also found that diesel engines with DMCC mode hydrocarbon (HC) and carbon monoxide (CO) emissions had an appreciable increase. In this study, the oxidation catalyst technique will be employed to decrease HC and CO emissions.The present contribution describes an experimental investigation conducted on the 4-cylinder D.I. engine, which has been properly modified to operate under DMCC mode. Methanol injection quantity and injection timing were controlled by self-development electrically controlled unit (ECU). Diesel and methanol amount measurements were carried out by two fuel consumption meter, respectively. The DMCC engine performance and emissions characteristics were investigated with/without oxidation catalyst, revealing the effect of DMCC engine equipped with oxidation catalyst on exhaust emissions. The NO_x, HC, and CO measurements were carried out by exhaust gas analyzer in ppm. Particulate matter (PM) measurements were carried by a high volume sampler which is connected to the tail pipe of the engine. The NO_x, HC, and CO emissions were measured using CLD, FID, and NDIR更多还原