Using RON Synergistic Effects to Formulate Fuels for Better Fuel Economy and Lower CO2 Emissions

Abstract

The knock resistance of gasoline is a key factor to decrease the specific fuel consumption and CO2 emissions of modern turbocharged spark ignition engines. For this purpose, high RON and octane sensitivity (S) are needed.This study shows a relevant synergistic effect on RON and S when formulating a fuel with isooctane, cyclopentane and aromatics, the mixtures reaching RON levels well beyond the ones of individual components. The same is observed when measuring their knock resistance on a boosted single cylinder engine.The mixtures were also characterized on a rapid compression machine at 700 K and 850 K, a shock tube at 1000 K, an instrumented and an adapted CFR engine. The components responsible for the synergistic effects are thus identified. Furthermore, the correlations plotted between these experiments results disclose our current understanding on the origin of these synergistic effects.This study concludes that this synergistic effect encourages formulating highly paraffinic fuels for lower specific fuel consumptions and CO2 emissions. Thus, paraffins are still relevant compounds to formulate highly efficient gasolines, despite their low octane sensitivity when individually considered. Furthermore, the CFR engine is still the best known device to anticipate synergistic effects in gasoline's knock resistance, through the Octane Index (OI = RON -K.S). A sensitivity study on the "K value" of the octane index shows that octane sensitivity mainly drives the gasoline performance for the low-sensitivity fuels while RON also drives it for the high-sensitivity ones.

Prediction of the Octane Number: A Bayesian Pseudo-Component Method

“…The saturate and the aromatic hydrocarbon classes are associated with an antagonist and a synergistic blending eect, 42 respectively.…”

“…Thus, the saturate class controls the antagonist blending effect. 41 • The covariance between the aromatic and olefin classes is positive. Thus, an aromatic molecule mixed with an olefin tends to increase the octane numbers.…”

A kinetic investigation on the synergistic low-temperature reactivity, antagonistic RON blending of high-octane fuels: Diisobutylene and cyclopentane

“…The IDTs of all blending components were measured at a core gas temperature of T C = 700±1.5 K and two different top dead center (TDC) pressures of p C = 25±0.18 bar and 20±0.17 bar, which are close to "RON-like" condition as discussed in the literature [1,15,37], while keeping the equivalence ratio at unity.…”

“…However, the octane behavior of a blend between two or more compounds is rarely a linear function of the blend composition [10][11][12][13][14][15]. For example, the octane number of isooctane (iC8)ethanol blends increases steeply as the ethanol content increases at low ethanol composition, but shows a saturated behavior as more ethanol is blended [16].…”

“…In another study, DIB was blended with PRFs and fueled into an engine, and the unburned mixture was sampled to investigate the modification of the reaction pathways induced by DIB addition [18]. Similar efforts were also conducted using different high octane compounds, for example Dauphin et al [15] examined the effect of the composition of mixtures of cyclopentane (CPT) and aromatics blended into iC8 and observed synergistic octane boosting effect. Fundamental combustion research facilities, i.e.…”