Measurement Methodologies for Hydrocarbons, Ethanol and Aldehyde Emissions From Ethanol-Fuelled Vehicles

摘要

Alternative-fuelled vehicles are a growing market, and emission performance of these vehicles should be thoroughly investigated. The emission legislation is however very diversified in different countries; a short summary of the legislation in the EU, the USA and Brazil is presented in this study. In the EU regulations, everything measured with the FID (Flame Ionization Detector) is treated as hydrocarbon emissions. In the USA the alcohols and aldehydes are measured and reported separately from hydrocarbons. In Brazil, the alcohol part can be measured separately on voluntary basis. The influence of some of these differences has been further investigated in this report. Results from two related studies are presented. The FID response for ethanol was investigated and emission testing of an E85-fuelled FFV (Flex Fuel Vehicle) was performed. The FID sensitivity at two different detector temperatures - 113°C (as stated by the US EPA when testing alcohol-fuelled vehicles) and 190°C (often used as default setting in the EU) - were investigated showing a higher FID response at 113°C. The response curve shows a slow response due to adsorption of ethanol in the measurement system. One FFV fuelled with E85 was tested on chassis dynamometer at two ambient temperatures: +22°C and -7°C. The ethanol emissions were analyzed with FTIR and sampled in impingers (standardized method approved in the USA). The acetaldehyde emissions were analyzed with FTIR and sampled in DNPH(2,4-dinitrophenyl hydrazine)-cartridges (standardized method approved in the USA). The FTIR provides second-by-second data which showed that high levels of unburned ethanol were emitted during the cold start phase. Comparison between the FTIR results and methods standardized in the USA were performed. The percentage distribution of some of the components included in the total hydrocarbons measured by the FID was investigated, and comparison between tests performed at the two different ambient temperatures can be made. The proportion of unburned ethanol increased at cold climate testing - from 24% at +22°C up to 53% at -7°C.