Study of oxygen-containing hydrocarbons in exhaust emission from a spark ignition combustion engine

For the auto-ignition phenomena such as homogeneous charge compression ignition combustion and knocking of spark ignition engines, it is thought that combustion products in burned gas affect ignition timing. However, those compounds are not clarified because it is difficult to separate compounds by using one-dimensional gas chromatography which is the most common method for gas analysis. In this study, a comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometer was employed to analyze combustion products in exhaust gas emitted by spark ignition combustion. In the exhaust gas analysis of spark ignition combustion which used regular gasoline and 10W-30 lubricating oil, a lot of mass spectrometer signals which include many compounds produced by lubricating oil were detected. In addition to the influence of the oil, the large number of detected substances about fuel and exhaust gas makes analysis of relation between reactants and products difficult. Therefore, n-heptane as fuel and poly-α-olefin as lubricating oil were applied for engine experiments. By these changes, the number of detected substances was decreased and influence of lubricating oil became weak. From the analysis of each detected substance, it was suggested that nitrogen compounds, aromatic compounds and cyclic compounds existed in exhaust gas of n-heptane spark ignition combustion. In addition, existence of many types of oxygen-containing hydrocarbons was suggested. From the analysis focusing on linear and branched oxygen-containing hydrocarbons with seven carbon atoms, it was suggested that many types of oxygen-containing hydrocarbons which were not considered in detailed reaction model existed in exhaust gas.