Combustion characteristics of higher-alcohol/gasoline blends

Abstract

An experimental investigation of combustion characteristics of higher-alcohol/gasoline [unleaded test gas 96 (UTG 96)] blends is presented. Lower alcohols (methanol and ethanol) have been used in the past as fuel extenders by mixing them with gasoline, but relatively little work has been reported on higher alcohols (propanol, butanol and pentanol). All these alcohols can be produced from coal-derived syngas. Given the abundant coal reserves in the United States, use of such higher alcohols offers an attractive alternative to alleviate the country's growing needs for transportation fuels. Comparisons of knock limits, indicated mean effective pressure (i.m.e.p.), emissions and fuel characteristics between higher-alcohol/gasoline blends and neat gasoline were made to determine the advantages and disadvantages of blending alcohol with gasoline. All tests were conducted on a single-cylinder Waukesha cooperative fuel research (CFR) engine operating at steady state conditions and stoichiometric air-fuel ratio. The data show that higher-alcohol/gasoline blends have a greater resistance to knock than neat gasoline does, as indicated by the knock resistance indicator (KRI) and the (RON+MON)/2 antiknock index (where RON is the research octane number and MON the motor octane number). Ignition delay and combustion interval data show that higher-alcohol/gasoline blends tend to have faster flame speeds.