Impacts of gasoline fuel components on GDI engine performances: Part 1, influence on gaseous toxic pollutants

In this paper, effects of different components in gasoline fuel on GDI engine emission characteristics were investigated. To simplify this investigation, model fuel CDTRF (composed of n-heptane, iso-pentane, diisobutylene, cyclohexane and toluene) instead of real gasoline fuel were used. To see how components of gasoline fuel affect engine performances, iso-pentane, diisobutylene, cyclohexane or toluene in CDTRF was substituted by other iso-alkanes, olefins, naphthenes and aromatics for comparative researches. N-heptane fraction is varied to balance fuel octane number. It is found that variation of fuel components obviously affect engine regulated and unregulated emissions. While, such effects vary when engine operation condition varies and are more distinct under lower engine speed or load conditions. Fuel components affect engine emission not just simply via chemical manner, but also through accompanying thermal-power process (cylinder pressure and temperature history). Thus variation of fuel components remarkably affects engine NOx emission. Alkanes, olefins and alkynes, aromatics contribute most to VOC emission followed by aldehydes. While, proportion of alcohols in VOC is negligible. However, variation of fuel components does not remarkably affect the proportion of alkanes, olefins and alkynes, aromatics as well as aldehydes in VOC although it affects total VOC emission obviously. Olefins and alkynes contribute most to OFP followed by aromatics and aldehydes. The contribution of alkanes is relatively low although it takes significant proportion in VOC. While, variation of fuel components remarkably affects total OFP of VOC though it does not obviously affect OFP composition. According to the results, it is hinted that more short chain i-paraffins and less branch chained cyclohexane in gasoline fuel would potentially help to reduce OFP of VOC.