Comparison of performance and emissions for gasoline-oxygenated blends up to 20 percent oxygen and implications for combustion on a spark-ignited engine

Abstract

Although experimental studies have shown that alcohol fuels burn cleaner than unleaded gasoline, there is limited information regarding the comparison among the alcohol fuels as gasoline additive in spark-ignited engines. Therefore, in this work, twelve different fuel formulations varying base composition (three different base gasolines), oxygenated level (3.5wt% up to 20wt%) and oxygenating agent (i.e. ethers, alcohols and one carbonate) were burned in a spark-ignited engine (AVL 5401 SI single cylinder) engine electronically controlled to investigate the relationships between fuel formulation, engine performance and exhaust emissions at constant spark advance (without combustion phasing optimization). Fuel properties related to initial phases of evaporation i.e. Reid Vapor Pressure, T10, T50, and heat of vaporization suggested an important effects of mixture formation and fuel metering in the combustion development. Experimental results were supported by both direct analysis of test matrix and statistical analysis. Moreover, results indicated that oxygen content and specific gravity were directly associated with CO and CO2 emissions, and inversely associated with NOx emissions. Hydrogen fuel content was directly associated with NOx emissions and inversely with CO2. Naphthenes, iso-paraffins, T90, and final boiling point showed marginal effect on engine performance and emissions.