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Dayma, Guillaume
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Towards Stoichiometric Combustion in HCCI Engines: Effect of Ozone Seeding and Dilution

CNRS-Guillaume Dayma, Philippe Dagaut
Laboratoire Prisme-Pietro Matteo Pinazzi, Fabrice Foucher
Published 2015-09-06 by SAE International in United States
Homogeneous Charge Compression Ignition (HCCI) is generally considered as an efficient solution to reduce fuel consumption and meet the pollutant requirements of internal combustion engines. Furthermore, the HCCI combustion strategy delivers drastically reduced levels of NOx and particulate matter, and combined with a post treatment device, low levels of unburned hydrocarbons (HC) and carbon monoxide (CO) can be achieved. However, affordable and widely used three-way catalytic converters require the engine to be run under stoichiometric conditions. Running an HCCI engine under an increased equivalence ratio leads to advanced combustion phasing and an excessive in-cylinder pressure rate that can affect engine operation. The dilution effect of Exhaust Gas Recirculation (EGR) represents a way to delay ignition of the mixture and reduce excessive in-cylinder pressure gradients. However, acting exclusively on dilution in order to control HCCI combustion is problematic and could lead to misfire or unstable combustion characteristics. Recent studies demonstrated that seeding the engine intake with oxidizing chemical species is a promising strategy to achieve combustion control in HCCI engines. Among many oxidizing chemical species, ozone…
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Application of an Ozone Generator to Control the Homogeneous Charge Compression Ignition Combustion Process

CNRS-Guillaume Dayma, Philippe Dagaut
Universite D'Orleans-Fabrice Foucher, Christine Rousselle
Published 2015-09-06 by SAE International in United States
The present investigation examines a new way to control the homogeneous charge compression ignition (HCCI) process. An ozone generator was set up to seed the intake of a single-cylinder engine with low concentrations of ozone. Two kinds of gas supply were tested: an oxygen supply and an air supply; as well as two kinds of injection: a plenum injection and an injection inside one of the intake pipes. The results showed that air can easily be used and that the second injection mode is the best way to achieve an on-road application. Moreover, experiments demonstrated that each combustion parameter such as the phasing, the indicated mean effective pressure and the pollutants can be controlled by varying the capacity of the ozone generator. Then, from experimental results, two dynamic control approaches on the maximum pressure phasing were proposed. A cartography control showed that a fast control of the combustion phasing can be achieved and a closed loop control demonstrated an excellent accuracy. Finally, this investigation demonstrated that an on-road application is achievable and improvements of this…
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Effect of Additives on Combustion Characteristics of a Natural Gas Fueled HCCI Engine

CNRS-Guillaume Dayma, Philippe Dagaut
CNRS - Université d'Orléans-Jean-Baptiste Masurier
Published 2014-10-13 by SAE International in United States
Homogeneous Charge Compression Ignition (HCCI) is among the new generation of combustion modes which can be applied to internal combustion engines. It is currently the topic of numerous studies in various fields. Due to its operating process, HCCI ensures a good efficiency, similar to that of compression ignition (CI) engines, and low particulate and nitric oxide (NOx) emissions. However, before promoting the use of this kind of engine, several challenges must be addressed, in particular controlling the combustion.Recent work showed that the combustion phasing can be controlled using low concentrations of ozone, an oxidizing chemical species. As ozone generators become increasingly compact, the integration of this kind of device in passenger cars can be considered.The present study investigates the effect of ozone on the combustion of different fuel mixtures. The engine was fuelled with various blends: a 95%methane/5%propane mixture and three different methane/hydrogen mixtures. The engine parameters and pollutant emissions were analyzed as a function of ozone seeding in several cases: by degrading the intake pressure, by degrading the intake temperature, and by varying the…
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Engine Performances and Emissions of Second-Generation Biofuels in Spark Ignition Engines: The Case of Methyl and Ethyl Valerates

CNRS-Guillaume Dayma, Philippe Dagaut
Universite D'Orleans-Christine Mounaïm-Rousselle
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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Towards HCCI Control by Ozone Seeding

CNRS-Guillaume Dayma, Philippe Dagaut
Universite d'Orleans-Fabrice Foucher, Christine Mounaïm-Rousselle
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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