Investigation of the combustion characteristics and knock tendencies of neat C1-C4 alcohol fuels using a CFR engine

Even though it is primarily used in blends with gasoline, neat ethanol is considered an excellent fuel for spark- ignition engines, as demonstrated by its widespread use as a transportation fuel in Brazil. The use of biologically produced alcohols in neat form has the potential to displace larger amounts of fossil fuels, compared to using them solely as oxygenate blend components. Consequently, further reductions in net CO2 emissions can be achieved. Besides ethanol, other lower alcohols also have the potential to be used as neat spark-ignition fuels, thus warranting further investigation. Therefore, this work provides a direct comparison, performed on a modified Waukesha CFR engine, of neat C1-C4 alcohols, with ethanol being the reference fuel. The tests focused on the combustion characteristics and knock propensities of the different compounds. The experimental test procedure was comprised of spark-timing sweeps at two compression ratios, at stoichiometric conditions and constant engine speed. In summary, the results showed that, with the notable exception of n-butanol, the C1-C4 alcohols exhibited good combustion characteristics and knock resistance, indicating their strong potential as biofuels that can be used in neat form, thus offering an additional pathway to reduce the use of fossil energy in transportation.