Approaches to the control of compression ignition through chemical-mechanistic investigation of low temperature oxidation process of hydrocarbons

1)建立了用于低温氧化反应基元能级分析的激光光谱分析系统，并将其应用于二甲醚氧化的初始步骤--甲氧甲基+O2反应。该系统包括用于检测HO2和OH的近红外多通道吸收光学系统，用于检测烷基和烷基过氧基的紫外光吸收光学系统，以及用于引发主体反应的激光脉冲光解。测量了HO2、OH和甲氧甲基过氧基的时间分辨分布，并与动力学模型计算的结果进行了比较。由于甲氧基甲基自由基热分解速率是模型中不确定的一个原因，因此分别测量了该速率。本研究提出甲氧基甲基+O2不仅与O2加合物发生复合反应，还可直接生成OH+甲醛。OH+甲醛的二次反应是生成H_2O_2的主要途径，而H-…则是直接生成H_2O_2的途径对单缸活塞式发动机两步自燃过程进行了化学力学分析。由于暂态物种在步骤中的行为对分析至关重要，因此开发和应用了针对此类物种的检测技术。(1)在差动抽气真空系统中，采用直接质谱学检测技术，改进了电动阀时间分辨采样技术。经过高贵校正，消除了初始采样的壁面分量的影响，有效分辨率小于1ms。结果表明，在第一次冷点火阶段生成了甲醛和H_2O_2等暂态物质，在最终热点火阶段消失。相对于部分燃料消耗的量也与最近的二甲醚氧化模型一致。(2)在热点火抑制条件下，还测量了排气中冷点火的瞬变物种。该方法虽然限制了当量比等实验条件的范围，但利用质谱仪和傅立叶变换红外光谱技术，扩大了可观察物种的范围，提高了分析的准确度。通过对二甲醚冷点火过程中甲酸和甲酸甲酯的检测，验证了2000年版Curran等方法的相对正确性。详细的氧化模型与1998年的版本进行了比较。较少

1)A laser-spectroscopic system for elementary reaction level analysis of low temperature oxidation has been developed and applied to methoxymethyl + O2 reaction, which is the initial step of dimethyl ether oxidation. The system consists of near-IR multi-pass absorption optics for detection of HO2 and OH, UV absorption optics for detection of alkyl radical and alkyl peroxy radicals, and laser pulse photolysis to initiate the subject reaction. Time-resolved profiles of HO2, OH and methoxymethyl-peroxy radical were measured and compared to those calculated with kinetic models. Thermal decomposition of methoxymethyl radical was separately measured as the rate was a cause of uncertainty in the models. It was proposed in this study that methoxymethyl + O2 undergoes not only recombination to O2 adducts but also direct formation of OH + formaldehydes. The secondary reaction of OH + formaldehyde was confirmed to be the main route to HO2 formation, but another route through direct formation of H … More CO was also suggested.2)Chemical-mechanistic analyses of two-step autoignition process have been conducted in a single-cylinder piston engine. As the behaviors of transient species during the steps are crucial for the analysis, detection techniques for such species were developed and applied. (1)The time-resolved sampling technique through an electrically actuated valve was improved by adopting a direct mass-spectroscopic detection in a differentially pumped vacuum system. With a noble correction eliminating the contribution of initially sampled wall-boundary components, effective resolution of less than 1 ms was attained. It was confirmed that the transient species such as HCHO and H2O2 are formed in the first cool ignition stage and disappear in the final hot ignition. The amounts relative to the partial fuel consumption were also consistent with the recent model of dimethyl-ether oxidation. (2)The transient species of cool ignition were also measure in the exhaust within hot ignition suppressed conditions. Although the range of experimental conditions such as equivalence ratio is limited in this method, observable species is expanded and the accuracy are better by using mass spectrometer and FT-IR. The detection of formic acid and methyl formate in the cool ignition of dimethyl ether demonstrate the relative correctness of the 2000 version of Curran et al. detailed oxidation model compared to the 1998 version. Less