An Experimental Investigation on Aldehyde and Methane Emissions from Hydrous Ethanol and Gasoline Fueled SI Engine

Use of ethanol as gasoline replacement can contribute to the reduction of nitrogen oxide (NO_x) and carbon oxide (CO) emissions. Depending on ethanol production, significant reduction of greenhouse-gas emissions is possible. Concentration of certain species, such as unburned ethanol and acetaldehyde in the engine-out emissions are known to rise when ratio of ethanol to gasoline increases in the fuel. This research explores on hydrous ethanol fueled port-fuel injection (PFI) spark ignition (SI) engine emissions that contribute to photochemical formation of ozone, or so-called ozone precursors and the precursor of peroxyacetyl nitrates (PANs). The results are compared to engine operation on gasoline. Concentration obtained by FTIR gas analyzer, and mass-specific emissions of formaldehyde (HCHO), acetaldehyde (MeCHO) and methane (CH₄) under two engine speed, four load and two spark advance settings are analyzed and presented. Combustion phasing results based on in-cylinder pressure analysis are also included. Concentration and specific emissions of acetaldehyde and methane were found to increase in case of hydrous ethanol, comparing to gasoline use. Difference in formaldehyde emissions was statistically insignificant at slower engine speed.