Octane requirements of modern downsized boosted gasoline engines

Cracknell, Roger; Warnecke, Wolfgang; Redmann, Jan-Hendrik; Goh, Tor Kit

doi:10.1007/s38313-015-0023-9

Cited by 9 publications

(10 citation statements)

References 11 publications

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“…Gasoline fuels are widely used in automobiles powered by spark ignition (SI) engines. Stringent regulations on fuel economy and emissions are motivating engine downsizing and boosting [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

“…Increasing the intake pressure (i.e., boosting) via turbocharging typically results in higher in-cylinder temperatures; however, by the use of intercooling and exhaust gas recirculation, the intake temperatures for a given pressure are lower resulting in increased engine efficiency [2,3]. In such modern engines, the conventional antiknock quality metrics of research octane number (RON) [4] and motor octane number (MON) [5] are less relevant.…”

Section: Introductionmentioning

confidence: 99%

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Compositional effects on the ignition of FACE gasolines

Sarathy

Kukkadapu

Mehl

et al. 2016

Combustion and Flame

181

236

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As regulatory measures for improved fuel economy and decreased emissions are pushing gasoline engine combustion technologies towards extreme conditions (i.e., boosted and intercooled intake with exhaust gas recirculation), fuel ignition characteristics become increasingly important for enabling stable operation. This study explores the effects of chemical composition on the fundamental ignition behavior of gasoline fuels. Two well-characterized, high-octane, non-oxygenated FACE (Fuels for Advanced Combustion Engines) gasolines, FACE F and FACE G, having similar antiknock indices but different octane sensitivities and chemical compositions are studied. Ignition experiments were conducted in shock tubes and a rapid compression machine (RCM) at nominal pressures of 20 and 40 atm, equivalence ratios of 0.5 and 1.0, and temperatures ranging from 650 to 1270 K. Results at temperatures above 900 K indicate that ignition delay time is similar for these fuels. However, RCM measurements below 900 K demonstrate a stronger negative temperature coefficient behavior for the FACE F gasoline having lower octane sensitivity. In addition, RCM pressure profiles under two-stage ignition conditions illustrate that the magnitude of low-temperature heat release (LTHR) increases with decreasing fuel octane sensitivity. However, intermediate-temperature heat release is shown to increase as fuel octane sensitivity increases. Various surrogate fuel mixtures were formulated to conduct chemical kinetic modeling, and complex KAUST multicomponent surrogate mixtures were shown to reproduce experimentally observed trends better than simpler two-and three-component mixtures composed of n-heptane, iso-octane, and toluene. Measurements in a Cooperative Fuels Research (CFR) engine demonstrated that the KAUST multicomponent surrogates accurately captured the antiknock quality of the FACE gasolines. Simulations were performed using multicomponent surrogates for FACE F and G to reveal the underlying chemical kinetics linking fuel composition with ignition characteristics. A key discovery of this work is the kinetic coupling between aromatics and naphthenes, which affects the radical pool population and thereby controls ignition.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Compositional effects on the ignition of FACE gasolines

Sarathy

Kukkadapu

Mehl

et al. 2016

Combustion and Flame

181

236

View full text Add to dashboard Cite

show abstract

“…Relevant conditions relating to the anti-knock quality of fuel blends within engines are the temperature and pressure conditions experienced by the unburnt end gas, which in modern engines tends to be at lower temperatures than those in the RON test. Hence, the most appropriate way to describe the octane appetite is neither RON nor MON, but an extrapolation of RON/MON values to cooler conditions [14].…”

Section: Introductionmentioning

confidence: 99%

Experimental and modelling study of the impacts of n-butanol blending on the auto-ignition behaviour of gasoline and its surrogate at low temperatures

Gorbatenko

Tomlin

Lawes

et al. 2019

Proceedings of the Combustion Institute

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“…This can lead to the flawed conclusion that, as long as a high octane sensitivity is desired for fuel performance, their incorporation is detrimental. Boot et al [14] have indeed demonstrated that, from a statistical point of view, a higher paraffinic fraction leads to lower octane sensitivity, which leads to a lower Octane Index in modern turbocharged engines, which in the end leads to a lower fuel performance [15,16,17,18]. But the use of optimized blending laws, such as those described above, allowing to create synergistic effects with isoparaffins on RON and octane sensitivity, could radically change this conclusion.…”

Section: = (4)mentioning

confidence: 99%

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

Dauphin¹,

Obiols²,

Serrano³

et al. 2019

SAE Technical Paper Series

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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.

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Octane requirements of modern downsized boosted gasoline engines

Cited by 9 publications

References 11 publications

Compositional effects on the ignition of FACE gasolines

Compositional effects on the ignition of FACE gasolines

Experimental and modelling study of the impacts of n-butanol blending on the auto-ignition behaviour of gasoline and its surrogate at low temperatures

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

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