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Numerical and Experimental Investigation of Combustion Regimes in a Dual Fuel Engine

Universite d'Orleans-Christine Mounaïm-Rousselle
Universite d'Orleans and IFPEN-Haifa Belaid-Saleh
Published 2013-09-08 by SAE International in United States
Among the new combustion concepts envisaged to meet future regulations, the Dual Fuel (DF) concept is considered to be an attractive strategy due to its potential to reduce CO2 emissions and engine-out pollutant emissions levels. A small quantity of high-cetane fuel (Diesel) is injected in the combustion chamber in order to ignite a homogeneous mixture of air and a highly volatile fuel (gasoline in our study). The DF concept has been shown to achieve improved engine thermal efficiency and low engine-out NOx and soot emissions. However, the physical mechanisms controlling DF combustion and in particular, determination of the predominant combustion regime(s) are not yet well understood. In this study, numerical simulations (CFD) and optical engine measurements are used to investigate Dual Fuel combustion. The ECFM3Z combustion model (implemented in the IFP-C3D code) is presented in this paper in addition to preliminary results which have been performed for DF internal combustion (IC) engine simulations. The approach employed in this study allowed determination of the relative contributions of auto-ignition (AI), flame propagation (ECFM) and Burned Gas (BG)…
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Engine Performances and Emissions of Second-Generation Biofuels in Spark Ignition Engines: The Case of Methyl and Ethyl Valerates

Universite D'Orleans-Christine Mounaïm-Rousselle
Universite d'Orleans-Fabrice Foucher, Fabien Halter
Published 2013-09-08 by SAE International in United States
As an alternative to second generation ethanol, valeric esters can be produced from lignocellulose through levulinic acid. While some data on these fuels are available, only few experiments have been performed to analyze their combustion characteristics under engine conditions. Using a traditional spark ignition engine converted to mono-cylinder operation, we have investigated the engine performances and emissions of methyl and ethyl valerates. This paper compares the experimental results for pure valeric esters and for blends of 20% of esters in PRF95, with PRF95 as the reference fuel. The esters propagate faster than PRF95 which requires a slight change of ignition timing to optimise the work output. However, both the performances and the emissions are not significantly changed compared to the reference. Accordingly, methyl and ethyl valerate represent very good alternatives as biofuels for SI engines. Future studies will focus on testing these esters in real application engines and performing endurance tests.
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Improving the Overall Efficiency of a Pneumatic-Combustion Hybrid Engine by Adding an Intermediate Heated Tank

Universite d'Orleans-Pascal Brejaud, Alain Charlet, Pascal Higelin
Published 2013-09-08 by SAE International in United States
Several works have previously shown that the concept of pneumatic-combustion hybrid engine is an interesting alternative to the Electric Hybrid Vehicle, by leading to equivalent fuel savings for a probable lower cost. However, these studies have shown that the thermal insulation of the tank is a problem. Indeed, due to its size and its location, the adiabaticity of the pneumatic tank cannot be guaranteed. During a regenerative braking (pneumatic pump mode) the hot and pressurized air that is send to the tank cools, pressure drops and density increases. When reusing the air in pneumatic motor mode, the mass necessary to fill the cylinder is greater than the one that would have been necessary if the air was not cool at its stay in the tank. This phenomenon is the major cause to the quite low regenerative efficiency that has been observed on a prototype engine. This paper proposes and evaluates a solution to this problem by using an intermediate air tank heated by the exhaust gases while the engine operates in the conventional combustion mode.…
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Towards HCCI Control by Ozone Seeding

Universite d'Orleans-Fabrice Foucher, Christine Mounaïm-Rousselle
Universite d'Orleans - CNRS-Jean-Baptiste Masurier
Published 2013-09-08 by SAE International in United States
Nowadays, the main objectives in the automobile engine field are to reduce fuel consumption and pollutant emissions. HCCI engines can be a good solution to meet pollutant emission requirements and to achieve high combustion efficiency. However, before an HCCI engine is used as a conventional engine, several problems must be overcome, in particular control of the progression of combustion.Many studies have been conducted into possible control methods. A new strategy consists in using oxidizing chemical species such as ozone to seed the intake of a HCCI engine. As increasingly smaller ozonizers are now being designed, this kind of device could be integrated on a vehicle and on a HCCI engine, in order to control combustion phasing and promote the future use of this engine as a conventional engine.In the present study, experiments on a HCCI engine fuelled with iso-octane were carried out with ozone seeding in the intake. Results showed that when assisted by the addition of ozone, combustion can be enhanced and moved forward. Consequently, the use of oxidizing chemical species can be a…
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Impact of Fuel Properties and Flame Stretch on the Turbulent Flame Speed in Spark-Ignition Engines

Universite d'Orleans-Pierre Brequigny, Christine Mounaïm-Rousselle, Fabien Halter, Bruno Moreau
Total Marketing and Service-Thomas Dubois
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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