Merit function for simultaneous optimization of fuel properties, naturally aspirated spark-ignition engines equipped with port fuel injection system, and regulated emissions

Abstract

Merit function allows systematically rank gasolines to better understand the relationship between fuel properties and thermal engine efficiency relative to E10 gasoline. In this sense, merit function was employed to ranking Mexican gasolines and for optimization of fuel properties. The performance of fuels was extended to investigate thermal engine efficiency, fuel consumption, and regulated emissions. Three base gasolines were blended with ethyl-tert-butyl-ether (ETBE), methanol, ethanol, dimethyl carbonate or isobutanol at 3.5, 10, and 20 wt% of oxygen. Fuels were tested in a mono cylinder spark-ignition research engine, which is coupled to an asynchronous dynamometer and equipped with an emissions analysis system.Results obtained in the mono cylinder engine show that gasolines blended with ETBE, or ethanol improve thermal engine efficiency (+2.4%) in line with a reduction of fuel consumption (−1.0%) relative to Premium gasoline. Besides, emissions of NO (−3.6%), HC (−3.1%), and CO (−8.5%) show a steadily reduction compared to those observed for Premium gasoline. However, gasolines blended with ethanol present a major impact on thermal engine efficiency, fuel consumption, and emissions (of CO and hydrocarbons) respect to those blended with ETBE. In fact, we found that a gasoline blended with ethanol (9.4% vol.%) could help to reduce by 5.5%, 7.5%, 11.3%, and 1.2% emissions of NO, HC, CO, and CO2, respectively, by boosting thermal engine efficiency (+3.5%) with a reduction on fuel consumption (−1.0%), relative to Premium gasoline. For the old vehicular fleet from México, a merit function based on Regular gasoline is proposed. It was found that the US E10 gasoline has a negative impact on thermal engine efficiency (−1.0%) relative to Regular gasoline. Results obtained in this investigation confirm that boosting the merit score by enhancing fuel properties relative to E10 or Regular gasolines, result in a reduction of the final emissions. However, there is not a clear correlation among the magnitude of variation of emissions, fuel consumption, thermal engine efficiency, and merit score.