【作者】 韩健；

【导师】 郎静；

【作者基本信息】 华中科技大学 ， 动力机械及工程， 2006， 硕士

【摘要】 随着全球能源危机和环境问题的加剧,各国对发动机代用燃料和新型燃烧方式的研究越来越重视。其中二甲醚(DME)均质充量压缩燃烧(HCCI)发动机以其良好的着火性能和超低的NOx、碳烟排放得到了广泛的研究,但是还存在一些亟待解决的问题,如其运行范围过窄,碳氢(HC)和一氧化碳(CO)排放较高,而且会生成甲醛等非常规排放物。本文对DME HCCI发动机燃烧及排放过程进行了数值模拟及试验研究。首先,建立了一个包含31种组分和46个反应的DME化学反应动力学简化模型,并建立了发动机二维轴对称计算模型,将DME化学反应动力学简化模型与CFD软件Fluent耦合,对DME HCCI发动机的燃烧与排放特性进行了变参数模拟计算。计算结果表明,该简化模型能够在较大的初始条件范围内有效模拟HCCI发动机的工作过程,并能预测甲醛、甲酸等重要产物的变化历程和NO的排放。研究了进气温度、进气压力、空燃比、压缩比、转速和惰性气体等因素对燃烧特性的影响,同时预测了缸内反应物、生成物、自由基浓度随曲轴转角变化的历程。本文经过大量反复试验,优化了气相色谱仪的分离和检测条件,为定量分析DME发动机尾气中甲醛、甲酸甲酯等非常规排放物的浓度提供了有效方法。更多还原

【Abstract】 With the energy crisis and environmental pollution of the world being more intensive, many countries pay more attention to the research of substitute fuels and combustion style of engine. Dimethyl Ether (DME) Homogeneous Charge Compression Ignition (HCCI) engine is widely researched because of its good ignition characteristic and very low emissions of NOx and soot. But there are some problems to be solved, such as reduced operating range, high HC and CO emissions and some unregulated emissions like formaldehyde.This paper researched the combustion and emissions forming progress of DME HCCI engine by numerical simulation and experimental methods. First, we built a reduced chemical kinetic model of DME which includes 31 species and 46 reactions, and built an engine’s two-dimensional model. We completed numerical simulations of the combustion and emission characteristics of DME HCCI engine using CFD software Fluent coupled with reduced chemical kinetic model. By analysis of calculated results, the model is valid in calculating HCCI engine operations in a wide range of initial conditions, can predict species concentration profiles such as formaldehyde and formic acid, and also the NO emission. We analyzed the influence of some factors to the engine performance, such as intake temperature, intake pressure, equivalence ratio, compression ratio, speed and inert gas, predicted the in-cylinder concentration histories of the reactants, products and intermediate radicals.After lots of experiments, we optimized the operating conditions of gas chromatography, provided a method to measure the concentrations of unregulated emissions including formaldehyde and formic ether.更多还原