Unregulated emissions from a gasohol (E5, E15, M5, and M15) fuelled spark ignition engine

Gasoline is increasingly blended with primary alcohols globally, in order to ensure energy security and to reduce local and global pollution load. However, no systematic scientific study reporting unregulated emissions from gasohol (gasoline blend with alcohol) fuelled engines has been undertaken by measuring the real-time emissions. To investigate unregulated emissions experimentally, a 4-cylinder, water-cooled, multipoint port fuel injection (MPFI) gasoline engine coupled with an eddy current dynamometer was used. Exhaustive experiments were carried out in this spark ignition (SI) engine, which was fuelled by gasohols (E5, E15, M5 and M15) vis-a-vis baseline gasoline for characterizing regulated and unregulated emissions. A raw exhaust gas emission analyzer was used for regulated emission measurements and a Fourier transform infrared (FTIR) emission analyzer was used for unregulated emission measurements. Experiments revealed that formic acid (HCOOH), iso-butane (iso-C4H10), and iso-pentane (iso-C5H12) were present in the exhaust in relatively lower concentration in gasohol blends compared to baseline gasoline. For higher gasohol blends (E15), iso-butane, n-pentane, ethane, toluene, and benzene were present in significantly low concentrations in the exhaust while ethyl alcohol, formaldehyde, propane and iso-butylene emissions were present in relatively higher concentrations in the exhaust. M15 emitted relatively lower concentrations of formic acid, iso-butane, iso-pentane, and benzene, but higher concentrations of methanol, formaldehyde, propane, n-pentane, and toluene compared to other test fuels. Gasohols were ineffective in reducing emissions of carbon dioxide (CO2) and acetic acid. Acetaldehyde was emitted by gasoline–ethanol blends however it was not detected in the emissions from gasoline and gasoline–methanol blends.