【作者】 文媛媛；

【导师】 肖合林；

【作者基本信息】 武汉理工大学 ， 动力机械及工程， 2011， 硕士

【摘要】 上世纪六十年代后,世界经历了3次严重的石油危机。由此带来的全球环境污染问题严重影响到各个国家的发展。能源特别是石油资源的严重匮乏、全球环境的日益恶化成为了世界两大难题。为了解决此问题,新型发动机以及各类汽车代用燃料的研究越来越引起广大学者的关注。天然气掺氢(HCNG)燃料,是满足节能减排问题的车用气体替代燃料之一,也是实现从传统燃料汽车到氢能汽车过渡的最具可行性方案。本文的工作主要是围绕天然气掺氢燃料发动机的燃烧排放特性进行的。本文首先对天然气掺氢燃料发动机的研究动态以及存在的相关问题进行了综述。然后利用大型气相化学动力学软件CHEMKIN对美国加州大学开发的GRI(Gas Research Instiutte)3.0天然气(CNG)详细化学反应机理进行分析。在天然气详细化学反应动力学机理上,参考已有的简化模型及方法,通过对天然气均质压燃燃烧反应途径的分析,再结合敏感度分析法和反应速率分析法,构建天然气燃烧简化机理。对比分析所构建的简化机理和详细机理的模拟结果,计算结果显示,此简化模型对HC、CO、NOX以及CH20排放物的变化历程有较为准确的预测,可以用来代替详细模型进行计算分析。简化模型大大减少了计算时间,并且为化学动力学模型与CFD多维模型进行耦合提供了可行性。依据此机理再加上本文中选用的氢氧燃烧机理,建立天然气掺氢燃烧反应模型。此模型由上述两个机理中提取,其中化学反应速率常数未做出改变。理论上推导出HCNG燃料的质量掺氢比,HCNG混合燃料中各组分的含量计算,HCNG混合气的热值计算以及HCNG化学计量比的计算公式。利用计算流体动力学软件FLUENT建立以ZS195发动机燃烧室为原型的三维计算模型,并将此CFD多维模型分别和天然气简化化学机理、天然气掺氢化学动力学模型相耦合,对CNG发动机以及HCNG发动机HCCI燃烧过程、排放特性进行模拟分析。结果显示：在天然气中掺入氢气后,相对纯天然气而言,发动机缸内着火时刻提前,温度峰值增加,燃烧更加充分,后燃减小,缸内压力峰值也随之增加。随着掺氢比的增加,CO和NOX(主要是NO)排放量增加,HC(主要是CH4)、CH20排放量减小。更多还原

【Abstract】 After the sixties of the last century, the world experienced three times’serious oil crisis.The global environmental resulted from the crisis severely affected the development of countries around the world. Energy, especially for the serious shortage of the oil resources and the deteriorating global environment have been regarded as the two difficulties around the world. To slove the problems, people pay more and more attention to the research on combustion innovative engine and alternative fuels. Hydrogen enriched natural gas is not only an alternative fuel meeting the demand of automobile developing "saving energy and reducing emission", but also act as feasible way to transform vehicle fule from conventional fuel to hydrogen gas. Good combustion and emission characteristics of HCNG engine are the focus of this thesis.Firstly this thesis summarizes the research trends, existent problems of Hydrogen enriched natural gas engines. According to the Gas Research Instiutte 3.0 natural gas detailed chemical kinetic mechanism of methane proposed by the University of California, this paper analyzes the natural gas detailed chemical kinetic mechanism by CHEMKIN. Based on the detailed chemical kinetics mechanism and existing simplified model, a new methane simplified chemical reaction mechanism is presented by sensitivity analysis and rate of production analysis. And then the comparative studies were given between the simplified model and the detailed model.The simulation results show that the simplified model can be used in place of the detailed model. It also can predict the variational courses of unregulated emissions such as formaldehyde, CO, NO and HC emission. The new simplified chemical kinetic model save more time for calculating, which provides a feasible way for the simulation of the chemical kinetics model coupled with the CFD multidimensional model.The paper plus hydrogen combustion mechanism based on the new methane simplified mechanism, then this thesis builds HCNG combustion reaction model. The model is extracted from the above two mechanisms that the chemical reaction rate constant isn’t made changes.In theoretical part of the paper, the equations are carried out for computing H2/CNG ratio in mass, stoichiometric ratio, heat value of fuel-air mixture on various H2 fractions in volume and the content of each component of HCNG mixture. This paper builds a combustion chamber three-dimensional model made by ZS195 diesel engine.With the CNG and HCNG reduced model coupling with the CFD software FLUENT, then it calculates the combustion and emission characteristics of natural gas and Hydrogen enriched natural gas HCCI engine. Compared with CNG, it can be seen that as the hydrogen fractions increased, the temperature peak grow up, the combustion stabilize, the duration decrease, and emission temperature drop down, as the cylinder pressure peak grow up correspondingly. With increasing the hydrogen blend ratio, the NOx(mainly NO) and CO emissions increase, and HC(Methane)、CH2O emission decreases respectively.更多还原