TDM - Transports Durables et Mobilité

Downsized Spark-Ignition Engine with Controlled Oxygen Concentration – MACDOC

Controlled Oxygen in a Downsized Spark Ignition Engine

Downsized Spark Ignition Engine whose oxygen concentration of the intake air is controlled by a membrane filtration device.

Understanding of the physico-chemical phenomena of highly diluted premix flame and impact on the downsized spark ignition engines

The propulsion of automobile vehicle is currently ensured and will continue for a few decades by an internal combustion engine of the spark-ignition engine or diesel engine type. As the emission standards became more and more stringent, the depollution of diesel engines made this engine uncompetitive compared to the spark-ignition engine, despite a much higher efficiency. In order to substantially improve the efficiency of spark-ignition engines and therefore to reduce fuel consumption and CO2 emissions, the increase in engine load, ie the intake air pressure, and the reduction in the size of the engine are technological paths commonly retained by industrialists but sometimes resulting in the appearance of knock and auto ignition which can degrade or even destroy the engine. To remedy this problem, the dilution by the burned gases of the combustion commonly called EGR is envisaged.<br />During the MACDOC project, we focused on:<br />(1) improve the fundamental knowledge of the highly diluted premix flame and to propose new kinetic schemes allowing to describe the oxidation of the fuel,<br />(2) evaluate the performance of a supercharged single-cylinder engine whose intake gases have been diluted to provide new experimental data to validate system simulations,<br />(3) propose new combustion models that take into account the dilution of fresh gases depending on the diluent composition and integrate these new models into commercial software,<br />(4) to propose a new membrane filtration technology to separate oxygen and nitrogen from the air in order to dilute the intake air of an engine with nitrogen by developing polymeric membranes specific to the internal combustion engine.

The feasibility of membrane filtration of oxygen and nitrogen in air was evaluated on a prototype filter mounted on a synthetic gas bench. A research of the key parameters related to the membrane filtration was carried out including the filtration surface, the thickness of the membrane, the material and taking into account the constraints related to the operation of the spark-ignition engine (flow and intake pressure, temperature). Engine tests were then carried out on a single-cylinder engine whose concentration of the chemical species of the intake air was perfectly controlled (O2, N2, CO2, H2O) in order to simulate the gases emitted by the membrane filter. The influence of the oxygen concentration on the basic parameters of the combustion was characterized on experimental devices. On the other hand, the laminar and turbulent flame velocities were measured on high-pressure and high-temperature spherical chambers, while the self-ignition times were evaluated in a microreactor. Thus, these fundamental parameters made it possible to construct new correlations which have been integrated into an OD model in order to predict the operation of a spark-ignition engine.

The modeling of combustion requires to know precisely the dependence of the fundamental parameters such as the flame velocity or the self-ignition time to the composition of the air in terms of concentration of O2, N2, CO2, H2. The experiments carried out made it possible to determine correlations which have been implemented in commercial 0D simulation software (Amesim) and which can be used in different applications such as simulation of industrial burners, boilers, gas turbines ... On the other hand, the search for materials allowing the optimization of the membrane filtration in terms of permeability and selectivity was also carried out. The Polymem project partner was able to develop new composite membranes.

The ANR MACDOC project helped to significantly enhance the knowledge of highly diluted combustion phenomena encountered in new generation spark-ignition engines. Membrane filtration of intake air and exhaust gases was assessed. The demonstrator allowed us to carry out the first tests on engine bench. Polymem, in charge of this development, is currently continuing to develop new products to meet the need for gas filtration and hopes to open up new markets.

During the project, the results were published in the form of scientific papers and presented at several international conferences. These publications also made it possible to enhance the work of the two PhD students who participated in the project. In particular, measurements and correlations of laminar and turbulent flame velocities and the methodology for determining self-ignition times were disseminated and published in 10 articles and conferences. The impact of the composition and concentration of diluents on single-cylinder engine operation was published at SAE (Society of Automotive Engineers) congresses.

The Downsizing Spark-Ignition Engine (DSIE) is one of the most promising solutions to reduce the CO2 emissions. But in order to optimize all operating modes, the dilution of fresh gases by exhaust gases (EGR) is the most planned way to decrease the pumping losses, to limit abnormal combustions but also the emissions of Nox. However, the dilution obtained by recirculation of exhaust gases requires a cooler to control the temperature of fresh gases and can involve a certain number of technological problems such as those related on the vapor condensation and the clogging of EGR circuit. Moreover, the control of the composition of recirculated gases and the time response of EGR loop can disturb the management of the automotive control.
A different way will be explored within the framework of MACDOC: to control the concentration of oxygen in-situ thanks to the technology of the polymer membranes. That could make it possible to simplify the loop of dilution of air-fuel mixtures, by avoid it and answer partly the various technological bolts such as the efficiency increase, the control of abnormal combustions and of the strong fluctuations cycles with cycle, but also the adequacy between DSIE and alternative fuels (Natural Gases, alcohols…) and hybridization of the vehicles which requires an optimization to limit regulated or not-regulated pollutant emissions, due to the more frequent stops of the IC engine.
The research project MACDOC (DSIE at Controlled Oxygen rate) thus aims at evaluating, in experiments then by a simulation system, the potential of controlling oxygen quantity in the inlet of DSIE. An exploratory phase based on single-cylinder engine will be done to estimate the impact of oxygen concentration control on abnormal combustions during mean and strong load and on the adequacy between fuel and engine in the case of stabilized characteristic operating points (PRISME-PCA). In parallel, a demonstrator of filtration system by membrane will be carried out by Polymem, specialist in the polymer membranes. For that, a characterization of selectivity of membranes with respect to oxygen and nitrogen will be carried out and will make it possible to determine ideal surface to obtain adequate oxygen concentration and to limit obstruction and pressure loss. As the variation of the oxygen content strongly influences the parameters, characteristic of the premixed combustion, which develops in the DSIE, a fine characterization of laminar flame velocity, auto-ignition delay and turbulent propagation velocities will be carried out from original devices such as a spherical combustion chamber, a micro-channel and a spherical combustion chamber with controlled turbulence rate (ICARE-PRISME). All these results will be finally capitalized in the form of a model system carried out under AMESim by the IFPEN. This model will make it possible to perform simulations of engine and vehicle in order to evaluate the potential of the control of the oxygen rate on various driving cycles. Lastly, an exploratory task will be devoted to evaluate the impact of an enrichment by CO2 at the inlet, which will be the 1st phase towards a possible in situ sequestration of CO2 emitted by a power unit.

Project coordination

Fabrice Foucher (Institut Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique) – fabrice.foucher@univ-orleans.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Polymem Polymem SA
PRISME Institut Pluridisciplinaire de Recherche en Ingénierie des Systèmes, Mécanique et Energétique
PCA Peugeot Citroën Automobiles
IFPEN IFP Energies Nouvelles
ICARE Institut de Combustion Aérothermique Réactivité et Environnement

Help of the ANR 1,023,196 euros
Beginning and duration of the scientific project: October 2012 - 42 Months

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