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初级反应水平分析的激光光谱系统，并将其应用于二甲醚氧化的第一步甲氧基甲基+ O2反应。该系统包括用于检测HO2和OH的近红外多通吸收光学元件，用于检测烷基自由基和烷基过氧自由基的紫外吸收光学元件，以及用于引发主体反应的激光脉冲光解。测定了HO2、OH和甲氧基过氧自由基的时间分辨谱，并与动力学模型计算结果进行了比较。甲氧基甲基自由基的热分解速率是模型不确定的一个原因，因此分别测量。本研究提出甲氧基甲基+ O2不仅可以重组成O2加合物，还可以直接生成OH +甲醛。证实了OH +甲醛的二次反应是生成HO2的主要途径，但也提出了直接生成H和更多CO的途径。对单缸活塞发动机的两步自燃过程进行了化学-力学分析。由于这些步骤中瞬态物种的行为对分析至关重要，因此开发并应用了瞬态物种的检测技术。(1)在差抽真空系统中采用直接质谱检测，改进了电动阀时间分辨采样技术。通过消除初始采样壁面边界分量的高贵校正，获得了小于1 ms的有效分辨率。结果表明，HCHO和H2O2等瞬态物质在第一次冷点火阶段形成，在最后的热点火阶段消失。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，对排气中的冷点火瞬态物质进行了测量。虽然该方法的等效比等实验条件范围有限，但利用质谱仪和傅里叶变换红外光谱，扩大了可观测物种，提高了测量精度。二甲醚冷点火过程中甲酸和甲酸甲酯的检测证明了Curran等人的2000版详细氧化模型相对于1998版的正确性。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