Formaldehyde and Acetaldehyde in Exhaust Gases Emitted from an Ethanol Fueled S.I. Engine

Abstract

Unburned ethanol, formaldehyde, acetaldehyde, hydrocarbons, NO and NO₂ concentrations along the exhaust tube of an ethanol fueled single cylinder S.I. engine were measured for various equivalence ratios and ignition timings. Experiments showed that periodical changes in concentrations of each species in the exhaust tube corresponded to the engine stroke cycle, and to a distribution of the species in the cylinder. Moreover, the changes were overlapped with the resulting oxidation of unburned ethanol. Formaldehyde and acetaldehyde were formed at the same time with the oxidation during the exhaust process. Using a temperature controlled reactor tube, characteristics of aldehyde formation were verified. It is found that aldehyde accumulation in exhaust system occurs at a temperature around 80 K.