LAUSR

Abstract A procedure for predicting the Critical Compression Ratio (CCR) and the Octane Number (ON) of hydrocarbon fuel blends is presented in this work. Compositional data as well as antiknock characteristics and thermo-physical properties of the constituent hydrocarbons are taken as input parameters for this calculation. The proposed methodology was developed by considering single-step kinetics for the pre-flame reactions taking place within the combustion chamber of the CFR engine, which is the standard apparatus used in ON evaluation tests. Furthermore, a thermodynamic model was used to describe the relevant processes the in-cylinder fuel-air mixture undergoes prior to the occurrence of knock. In order to validate the proposed method, CCRs of Primary Reference Fuel (PRF) mixtures; Motor ONs (MONs) of paraffinic fuels; and Research ONs (RONs) of Liquefied Petroleum Gas (LPG) fuels were computed and compared with experimental data reported in literature. The maximal absolute error and the root mean square deviation found were, respectively, 0.084 and 0.047 for the CCR of PRF mixtures; 1.6 and 0.60 for the MONs of paraffinic fuels; and 1.45 and 0.70 for the RONs of LPG fuels.