【作者】 梁霞；

【导师】 尧命发；

【作者基本信息】 天津大学 ， 动力机械及工程， 2005， 硕士

【摘要】 均质充量压燃（HCCI）燃烧概念给出了实现内燃机高效、低污染燃烧的新途径,也是目前国际内燃机界的研究热点。着火时刻和燃烧反应速率的控制以及运行工况范围的拓宽是实际工作中应用HCCI的关键和难点。本文提出了一种甲醇燃料高效清洁燃烧新技术,应用甲醇催化合成二甲基醚实现发动机燃用二甲基醚/甲醇两种燃料,通过控制两种燃料的比例来控制着火时刻和燃烧反应速度,使发动机在较大的工况范围内实现HCCI燃烧。甲醇催化合成二甲基醚的反应是放热反应,这些热量可以从发动机排气中得到。作者主要负责利用CHEMKIN软件从理论上研究HCCI燃烧反应的动力学机理,研究边界条件变化对燃烧过程的影响,探讨控制着火时刻和燃烧反应速率以及拓宽HCCI工况范围的技术途径,为实际中控制双燃料的均质压燃燃烧提供理论指导。对二甲基醚/甲醇双燃料的均质压燃燃烧工况范围进行了理论计算,计算的工况范围与实测的工况范围相当一致。应用零维详细化学反应动力学模型,研究了二甲基醚/甲醇双燃料均质压燃氧化反应机理,研究分析了初始温度、甲醇浓度和二甲醚浓度对氧化反应的影响。结果表明,甲醇改变了二甲基醚低温反应途径,二甲基醚的低温和二次加氧过程反应受到抑制,CH₃OCH₂直接裂解（β-scission）起主导作用,二甲基醚与甲醇高温反应几乎同时进行。在详细反应动力学研究基础上,通过对二甲基醚/甲醇均质压燃燃烧反应途径和敏感性分析,构建了双燃料简化动力学模型。此模型包括27种产物和35个基元反应。结果表明,所提出的双燃料简化动力学模型与详细动力学模型计算结果相当吻合,简化模型在对着火时刻、缸内温度和压力计算结果与详细模型基本一致,简化机理对变初始温度和混合气浓度也有较好的预测能力,对着火时刻和温度峰值以及压力峰值的预测与实验结果相当一致。可应用于模拟双燃料HCCI燃烧过程。更多还原

【Abstract】 Homogeneous Charge Combustion Ignition (HCCI) is an attractive advancedcombustion process that offers the potential for substantial reductions in both NOx andPM, while providing high efficiencies. Controlling of the auto-ignition timing andreaction rate of combustion expanding of engine loads are the keys and difficulties toput HCCI engines into practical use. A new combustion technique of methanol which enables high efficiency andlow emission has been developed in this paper. DME is to be produced from methanol,the HCCI engine is fueled with DME/methanol dual fuels, and controlling ofauto-ignition timing and reaction rate of combustion expanding of HCCI combustionto a wide operable range through adjusting the proportion of two fuels. DME can bereformed from methanol in endothermic reactions by using the heat from the exhaustgases. The chemical reaction kinetics processes in a HCCI engine fueled withDimethyl Ether / Methanol were investigated by using a zero-dimensional detailedkinetic model. The HCCI operating range of DME/methanol dual fuels is computedand the result is consistent with the experiments. The effects of initial temperature,excess air ratio of dimethyl ether (DME) and methanol on oxidation methanism ofDME/methanol were investigated also. The results show that methanol affects theDME oxidation path, LTR of DME and the second O2 addition is inhabited. Therefore,the thermal decomposition reaction of the methoxymethyl radical (CH3OCH2) namedβ-scission plays a more important role in LTR of DME. Also, high temperaturereactions (HTR) of DME and methanol almost occur at the same time. A reducedmodel of dymethyl ether (DME)/methanol has been developed on the basic of detailedkinetics model through analysis of reaction paths of combustion of DME/methanoland sensitivity analysis . It consists of 35 reactions for 27 species. The developedreduced model of DME/methanol agreed well with the detailed model in ignitiontiming temperature and pressure in cylinder. The reduced model also can predict wellwith various of initial temperature and concentration. It can well predict theauto-ignition timing and peak temperature and peak pressure. This reduced model canbe used to simulate HCCI combustion of DME/methanol.更多还原