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Dubois, Thomas
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Investigating the Impact of Ethanol on the Lubricity of Gasoline and on the Lubricity Improvers Efficiency

Total ACS-Thomas Dubois, Lidwine Abiad, Pauline Caine
Published 2017-10-08 by SAE International in United States
As it is the case for Diesel engines, the Gasoline Direct Injection engines are using higher and higher injection pressures. The state of the art gasoline Direct Injection (GDI) engines are currently using injection pressures as high as 500 bar. A lot of work is also currently ongoing on Gasoline Compression Ignition (GCI) engines which use even higher injection pressures (above 1 000 bar). A high injection pressure means that a high pressure pump has to be used and so, proper lubricity has to be brought by the fuel. In the mean time the use of biofuels is increasing and several studies have shown the positive impact of ethanol on the energy consumption of gasoline engines mainly thru an octane number effect. For all these reasons, it seems important to evaluate the impact of ethanol on the lubricity of gasoline as well as on the response of lubricity additives that may be required in a medium-term future to provide gasoline enough lubricity to ensure the operability of these new engines. This paper determines how ethanol…
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Thermodiffusive Effect on the Flame Development in Lean Burn Spark Ignition Engine

Total Marketing Services-Thomas Dubois
Universite D'Orleans-Pierre Brequigny, Fabien Halter, Christine Mounaïm-Rousselle, Bruno Moreau
Published 2014-10-13 by SAE International in United States
In Spark Ignition engines, the heat release rate is not only piloted by the mixture reactivity but also by its sensitivity to stretch effects. Only few results can be found in the literature about flame stretch effect in SI engine configurations.For this study, three different fuels (Methane, Propane, Iso-octane) were studied, but at different air-fuel lean mixture conditions, to present almost equivalent laminar flame speeds and thermo-dynamical properties at ignition timing condition. Besides those mixtures present different Lewis numbers which are relevant parameters to describe flame-stretch interactions. Mie-scattering tomography was then performed in an optical Spark Ignition (S.I.) engine. Using a high speed camera, flame propagation images were acquired through the piston. Thermodynamic analyses based on in-cylinder pressure traces were performed to estimate in-cylinder temperature and burnt mass fraction during the engine cycle.From the determination of flame areas, the global flame stretch and an equivalent propagation speed have been then defined and estimated. Results prove that mixtures have the same ranking in terms of flame stretch sensitivities as in the laminar regime. Probability density functions…
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Modelling a Gasoline Compression Ignition (GCI) Engine Concept

Concawe-Roger F. Cracknell, Javier Ariztegui, Thomas Dubois, Heather Hamje, Leonardo Pellegrini, David Rickeard, Kenneth D. Rose
FEV GmbH-Karl Alexander Heufer, Hans Rohs
Published 2014-04-01 by SAE International in United States
Future engines and vehicles will be required to reduce both regulated and CO2 emissions. To achieve this performance, they will be configured with advanced hardware and engine control technology that will enable their operation on a broader range of fuel properties than today.Previous work has shown that an advanced compression ignition bench engine can operate successfully on a European market gasoline over a range of speed/load conditions while achieving diesel-like engine efficiency and acceptable regulated emissions and noise levels. Stable Gasoline CI (GCI) combustion using a European market gasoline was achieved at high to medium engine loads but combustion at lower loads was very sensitive to EGR rates, leading to longer ignition delays and a steep cylinder pressure rise. In general, the simultaneous optimisation of engine-out emissions and combustion noise was a considerable challenge and the engine could not be operated successfully at lower load conditions without an unrealistic amount of boost pressure.To identify ways to improve the lower load performance of a GCI engine concept, Computational Fluid Dynamics and KIVA simulations have now been…
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Impact of Fuel Properties and Flame Stretch on the Turbulent Flame Speed in Spark-Ignition Engines

Total Marketing and Service-Thomas Dubois
Universite d'Orleans-Pierre Brequigny, Christine Mounaïm-Rousselle, Fabien Halter, Bruno Moreau
Published 2013-09-08 by SAE International in United States
The current decrease in fossil energy resources requires a diversification of the liquid and gaseous fuels potentially consumable in internal combustion engines. The use of these fuels modifies the combustion process and the heat released as well. In a Spark Ignition (SI) engine, the heat released is mainly piloted not only by the mixture reactivity but also by its sensitivity to stretch effects. Only a few results can be found in the literature about stretch effects for SI engine configurations. The purpose of the present paper is to evaluate stretch effects on the flame front propagation in an optical SI engine and to investigate the relative importance of these effects depending on the fuel considered.Different air-fuel mixtures presenting different flame stretch sensitivities were selected. Four different engine regimes (1400, 1600, 1800 and 2000 rpm) were studied for all the mixtures in order to evaluate the impact of different turbulence intensities. In-cylinder pressure analyses were performed to determine the heat release rate and the crank angle corresponding to 5% of mass burned. At the same time,…
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