【作者】 贺文江；

【导师】 黄海波； 曾东建；

【作者基本信息】 西华大学 ， 动力机械及工程， 2008， 硕士

【摘要】 开发可再生、环保的替代性燃料已成为21世纪人类的最重要课题之一。二甲醚(DME)是一种极其清洁和有发展潜力的柴油替代燃料,可以用多种支持可变能量来源的原料合成,它被很多国家作为未来使用的混合燃料。二甲醚的十六烷值高、蒸发潜热大、分子结构中没有C-C键、雾化质量好等特点决定了它是目前柴油最优良的替代燃料;但是它的粘度值低、弹性模量小、分子小、饱和蒸汽压力大、液态密度小等性质对传统柴油机供给系统提出了新的挑战,影响了其良好发展势头。本文在对国内外对新型清洁代用燃料二甲醚理论和应用研究广泛了解的基础上,借鉴柴油机供给系统的设计方法,对多缸发动机的燃油供给系统进行了改进设计,使之能为压燃式发动机持续可靠地提供二甲醚燃料。其中,二甲醚在常温常压下是气态,这就需要让柴油机的供油系统以及二甲醚的容器保持足够的压力,并要求密封。为了保证柴油机在燃用二甲醚时的动力性与燃用柴油时相同,对柴油机燃油系统的主要部件,如喷油泵柱塞偶件,出油阀偶件,喷油嘴偶件进行了设计计算,使其能够满足490柴油机燃用柴油时的动力性指标。借助仿真软件AMEsim建立了二甲醚发动机燃料喷射系统模型,其中主要包括柱塞油泵模型、出油阀模型和喷油器模型。以490柴油机为这套燃料喷射系统的配套目标机型,通过相应的参数设置,对490原柴油机燃用柴油及二甲醚的情况进行了计算仿真。结合二甲醚的物理化学性质对燃料喷射系统模型关键设计参数进行调整,利用AMEsim强大的批处理功能,对设计的二甲醚喷射系统的工作特性进行了仿真计算研究。仿真计算主要是针对供油特性影响比较大的参数:启喷压力、喷油孔直径、喷油孔数、发动机转速、凸轮型线。仿真计算结果表明,启喷压力对最高喷油压力影响较小,但对喷油持续角、针阀开启曲轴转角位置、二次喷射等均有较大影响;喷油孔直径对喷油率、喷油持续角、喷油量有一定的影响;凸轮转速对供油量、供油率、针阀升程等有较大影响;凸轮型线对供油提前角,供油规律,供油量有较大影响。结合台架试验,柴油机改烧二甲醚,其燃料在储罐内需要氮气保压,燃料喷射系统需要加大柱塞直径,需要较高的管路密封性,二甲醚中应添加适当的润滑剂。以上结论对二甲醚发动机的进一步开发研究提供一定方向性指导。更多还原

【Abstract】 Developing reproducible, alternative and environmentally friendly fuels has become one of the most important tasks for human beings in the 21st century. Dimethyl ether (DME) is a potential ultra-clean diesel alternative fuel that-could be synthesized from a variety of feedstock, which can support the use of alternative energy resources. DME has been considered as a compound fuel by many countries for future use.DME has high cetane value, great vaporization heat, good quality atomization, and zero C-C keys in the molecular structure. All these characteristics decide that DME is the best alternative fuel of diesel oil. However, DME is of low viscidity, low liquid state density, small elasticity module, and high saturation vapor pressure. Those disadvantages put forward a new challenge towards the supply system of traditional diesel engines, and affect the process of development to some extent.On the basis of wide knowledge of theoretical and applied research on new clean alternative fuel DME at home and abroad, in view of methodology of designing the supply system of diesel engines, this paper tries to give an improvement to the fuel supply system of multi-cylinder engines, so that it can provide diesel engines with DME fuel continually and reliably. DME is gaseous under the condition of standard atmosphere and temperature, which requires the oil supply system of diesel engines and the vessel storing up DME maintain seal with enough pressure. In order to make sure the equal sum of power can be produced when applying DME to an engine, the main components of the system need to be improved, including the plunger matching part in the oil spraying pump, the delivery valve matching part, and the nozzle matching part. The new fuel supply system can meet the power performance and emission regulation of diesel engine 490. With the simulation software AMEsim, an fuel injection system model of DME engines has been built, which includes a piston pump model, a delivery valve model and a fuel injector model. Parameters are set with Diesel 490 as a target model, and the situation of diesel and DME used by new fuel injection system is simulated in a computer. Key design parameters of fuel injection system are adjusted combined with the physical and chemical properties of DME. Making use of the batch disposal function of AMEsim, working characteristics study is also made towards the fuel injection system by using the simulation model of DME. Simulation calculation mainly concerns several influential parameters, such as the unlocking pressure, the hole diameter, the engine speed, the cam-line and so on.The simulation calculation results shows that, the unlocking pressure has less effect on the highest injection pressure, but greater impact on continued angle of fuel injection, the needle open crank angle displacement and the second jet. Injection hole diameter affects the fuel injection rate, continued angle of fuel injection and fuel injection volume; cam speed has a greater impact on the fuel supply volume, fuel supply rate, needle valve lift and so on; cam-line largely decides the fuel advanced angle, fuel supply laws and fuel supply volume. Combined with practical tests, diesel engines with DME need to use nitrogen to keep pressure in the fuel tank. Fuel injection system needs to increase the plunger diameter, strengthen the tightness of pipelines, and add appropriate lubricants in the DME. Better effect can be achieved when it is used in large diesel engines. The conclusions above will provide some directional guidance for further research on DME engine.更多还原