Cold start and full cycle emissions from a flexible fuel vehicle operating with natural gas, ethanol and gasoline

Abstract This paper describes a comparative study between the pollutant emissions produced by a spark ignition engine operating with three different fuels: commercial gasoline with 22% of ethanol (E22), compressed natural gas (CNG) and hydrous ethanol. The emission levels of oxides of nitrogen (NO x ), carbon monoxide (CO), carbon dioxide (CO 2 ), total hydrocarbons (HC), and methane (CH 4 ) produced by a flexible fuel engine operating according to the US 1975 Federal Test Procedure (FTP 75) were analyzed. Tests were performed with a mid-size sedan powered by 1.4-L spark ignition engine on a chassis dynamometer. The results for the cold start tests demonstrate that E22 produced the lowest CO and HC emissions, while CNG produced the lowest NO x emissions. Considering the full test cycle, CNG emitted the lowest CO, NO x and CO 2 concentrations, and the lowest fuel consumption. Gasoline presented the lowest emission levels of HC and CH 4 . Ethanol showed the highest fuel consumption and higher pollutant emission levels than the other fuels, except for CO 2 , which was higher than CNG and lower than gasoline.

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