Optimal octane number correlations for mixtures of toluene reference fuels (TRFs) and ethanol

Abstract

This paper presents a method for correlating the octane numbers of fuel mixtures, and applies this to the study of toluene reference fuels (TRFs) blended with ethanol. This method combines linear regression and exhaustive (or brute-force) searching for optimal Scheffé polynomials, where optimality is defined as the shortest polynomial that meets a reasonable estimate of the reproducibility limits in the standard, octane number test procedures. Two correlations for the RON and MON are found to be optimal. These achieve maximum absolute errors (MAE) of less than 2 octane numbers across TRF/ethanol mixtures with a RON between 80 and 120. These two correlations use mole fractions as the correlat..