【作者】 宋印东；

【导师】 袁银男；

【作者基本信息】 江苏大学 ， 动力机械及工程， 2013， 博士

【摘要】 甲醇来源丰富,且可以实现清洁燃烧,因此被认为是最具潜力的柴油机替代燃料之一。柴油机燃用甲醇最简单便捷的方法是乳化法。然而甲醇与柴油互不相溶,通常要采用添加乳化剂辅以高速搅拌或者超声振荡等手段乳化,并且所配乳化液不透明或者半透明,且保存时间短,易分层。本文依据微乳化理论,优化了甲醇柴油的配方,研究甲醇柴油微观特征和宏观理化性质,构建简化化学动力学模型分析甲醇柴油的燃烧特性,基于实验台架和三维数值模拟研究甲醇柴油应用于柴油机的特性。论文主要工作包括以下几个方面：(1)优化了甲醇柴油的配方和工艺。基于微乳化理论,实验研究了微乳化剂在不同条件下对甲醇柴油体系的乳化效率,通过均匀设计法优化甲醇柴油的配方。以油酸为主微乳化剂,异丁醇为辅助微乳化剂,并与乙酸乙酯和大豆油进行复配制备甲醇柴油。该甲醇柴油澄清透明,不分层,在室温密封的条件下可以稳定保存一年以上。制备工艺简单、不需外力辅助。(2)提出了基于小角X射线散射技术表征甲醇柴油微观形貌特征的方法。研究表明：甲醇柴油粒子呈球状,甲醇柴油除了散射粒子外还存在微电子密度不均匀区域,体系中存在界面层,甲醇柴油粒子具有质量分形特征。甲醇柴油的微观形貌与柴油相似。(3)开展了甲醇柴油的稳定性和流动性的实验研究。分析了甲醇柴油各组分含量和含水量对温度稳定性和时间稳定性的影响,甲醇柴油的各组分对粘度、凝点和冷滤点的影响特性,以及温度对粘度的影响特性。结果显示：甲醇柴油的凝点、粘度和冷滤点均低于柴油。(4)构建了新的正庚烷和甲醇耦合化学动力学模型研究甲醇柴油的燃烧特性。构建了正庚烷简化化学动力学机理模型(40/192机理模型)、甲醇简化化学动力学机理模型(18/45机理模型)、正庚烷和甲醇耦合化学动力学机理模型(35/77机理模型)。40/192机理模型可以在较大范围模拟正庚烷的滞燃期、层流火焰速度和质量流率；18/45机理模型可以在较大范围模拟甲醇的滞燃期、层流火焰速度；35/77机理模型可以模拟HCCI发动机燃用正庚烷和甲醇的燃烧特性。(5)在4B26增压直喷柴油机上开展了燃用甲醇柴油的实验研究和三维数值模拟研究。实验研究获得了柴油机的宏观参数,三维数值模拟研究获得了实验难于测量的微观信息。柴油机燃用甲醇柴油时的气缸压力曲线与燃用柴油时相似,气缸压力峰值比燃用M0时略低；压力升高率和压力升高加速度比燃用M0时高。柴油机燃用甲醇柴油与燃用柴油的燃烧噪声相比,低频段相差很小,中频段高出较多,高频段略高。气缸压力A声级的负荷特性变化趋势与燃用柴油时基本一致。研究了柴油机燃用甲醇柴油的燃烧放热规律,在高转速大负荷时,燃用甲醇柴油的放热规律曲线与燃用柴油时相似；在低负荷以及低转速全负荷时,甲醇柴油的滞燃期延长,放热持续期明显缩短,放热峰值随着甲醇含量的增加而升高。用三维数值模拟的方法对柴油机燃用甲醇柴油的性能和排放开展进一步分析,获得了实验难于测量的气缸内流场、温度场、油气浓度场、NO浓度场和Soot浓度场。更多还原

【Abstract】 Methanol is considered as one of the most potential alternative fuels for diesel engine as its rich source and clean combustion. The most simple and convenient method to use methanol in diesel engine is emulsification. However, methanol and diesel can’t be dissolved each other. It should be added emulsifier and stirred with high speed or applying ultrasonic oscillating. Emulsion is non-transparent or semitranslucent, easily stratified, and shorter storage.A formula on methanol-diesel is optimized based on microemulsion theory in this dissertation. The physical and chemical properties of methanol-diesel are studied as the formula. The chemical and dynamic model is set up to analyze combustion characteristic of methanol-diesel. The characteristic of methanol-diesel applying in diesel engine is also studied based on experimental bench and numerical simulation of three-dimension. The dissertation mainly includes the following several aspects:(1) It optimizes a formula and a process on methanol-diesel. The emulsification efficiency of different microemulsifier is experimentally studied under different conditions on methanol-diesel based on microemulsion theory. A methanol-diesel formula is determined by the uniform design method. It is uses oleic acid as primary emulsifier, isobutyl alcohol as auxiliary emulsifier, and mixed with ethyl acetate and soybean oil. The process is simple, it does not need any external support.(2) It puts forward microstructure characteristics of methanol-diesel by small angle X-ray scattering technique (SASX). Methanol-diesel particle is spherical. Besides scattering particles, it exists uneven microelectronic density area. There is interface layer in methanol-diesel. Methanol-diesel particle characterized with quality fractal. And its microstructure is similar with that of diesel.(3) It achieves the liquidity and stability of methanol-diesel on the formula are achieved. The influence of each component and water content on temperature stability and time stability, the influence of each component on viscosity, solidifying point and cold filtration point, and the influence of temperature on viscosity are achieved. Its solidifying point, viscosity and cold filtration point are lower than that of diesel.(4) It structures the chemical kinetics model of methanol-diesel. The the model of the simplified chemical kinetics mechanism of N-heptane(40/192), methanol(18/45), the coupling of N-heptane and methanol(35/77) are built. The40/192mechanism model can simulate ignition delay period, the laminar flame speed and mass flow rate of N-heptane in wide range; the18/45mechanism model can simulate ignition delay period, the laminar flame speed and mass flow rate of methanol in wide range; the35/77mechanism model can simulate the combustion characteristic of HCCI engine fueled n-heptane and methanol.(5) The experimental study and numerical simulation of three-dimension are conducted on4B26turbocharged direct injection diesel engine fueled with methanol-diesel. The macroscopic parameters are achieved by the experimental study and micro information is achieved by the numerical simulation. The experiment shows the cylinder pressure curve flued methanol-diesel is similar with that of diesel. is similar with that of diesel the peak cylinder pressure is slightly lower than fueled MO. The rate of and rise acceleration of the pressure rise are higher than fueled MO. Difference of combustion noise between methanol-diesel and diesel is very small at low frequency band, the former is much higher at intermediate frequency band, and slightly higher at high frequency band.The load characteristic fueled methanol-diesel cylinder pressure sound lever A is almost the same as that of diesel. Study on the heat release rate shows that the heat release rate fueled methanol-diesel was similar with fueled diesel under heavy load and high speed. Under low load or low speed full load, ignition delay period become longer, the duration of heat release become significantly shorter, but heat release rate increase with increase of methanol content. The performance and emissions is studied fueled methanol-diesel by three-dimensional numerical simulation. It achieves the flow field, temperature field, oil concentration, NO concentration field and Soot concentration field which is difficult to achieve by experiment.更多还原