Performance and Knock Limits of Ethanol-Gasoline Blends in Spark-Ignited Engines 850213
Ethanol-gasoilne blends have been investigated as a spark-ignition engine fuel. The work was carried out on a Ricardo E6 variable compression engine in which all the significant operating parameters can be varied and accurately measured including onset of knock. Various blends were used (10 to 70% ethanol by volume) and the effects of mixture strength, ignition timing and speed on the highest useful compression ratio were accurately defined. Borderline road test data were evaluated using information on reference fuels and the required performance of the automatic spark advance mechanism was deduced. The results revealed that higher concentration of ethanol in the blend greatly enhances knock resistance. A blend of 50% gasoline and 50% ethanol produced the highest output in both the rich and lean mixture regions. The performance of the automatic spark advance mechanism was found to vary considerably with various blends and mixture strengths. The sensitivity of optimum power attainment to ignition timing and mixture strength was illustrated. Also the saving in mechanical octanes was put forward.