Experimental and Simulation Studies to Determine the Effective Octane Number in an Engine Fuelled with Ethanol and Gasoline

Abstract

Alcohols are widely used along with gasoline owing to their superior antiknock
properties. Engine knocking depends on both fuel properties and operating conditions.
The Research and Motor Octane Numbers widely used to characterize antiknock
potential are calculated under specific operating conditions. In this work, a method that
incorporates the effects of actual operating conditions is developed, used to determine
the antiknock potential when ethanol and gasoline are used in a port fuel injected engine
using simultaneous and pre-blended injection modes. Experimental results are used to
build and validate an analytical model of the engine which is used to study the
antiknock benefits in terms of “Effective Octane Number” (ONEff). Experiments are
conducted using a newly developed injection system which utilizes separate injectors
for ethanol and gasoline. This method could capture the effects of engine operating
conditions in calculating antiknock benefits. Higher ethanol fractions showed better
antiknock capabilities. ONEff increases from 90 to 105 units when the ethanol quantity is
increased from 0 to 100% by mass, but the effect diminishes after 50%. Hence,
considering antiknock benefits, the use of 50% ethanol in gasoline is recommended.
ONEff of the pre-blended injection case was only 0.8 units higher, indicating the similar
antiknock potential of both injection strategies.