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Soot Volume Fraction (SVF) measurements were performed in an IFP Energies nouvelles optical single cylinder Diesel engine operated in Low Temperature Combustion (LTC) conditions. The engine was equipped with a sapphire liner, a dedicated flat bowl piston and a six-hole common-rail high pressure injector. The piston design included four quartz windows allowing optical access into the bowl. The aim of this work was to study soot formation and oxidation during the LTC Diesel combustion process and to build a database providing soot formation and oxidation data under a set of engine conditions to help developing and testing Computational Fluid Dynamics (CFD) models. Two complementary optical diagnostic techniques were combined: Planar Laser Induced Incandescence (PLII) and Laser Extinction Method (LEM).

Current progress in the development of diesel engines substantially contributes to the reduction of NOx and Particulate Matter (PM) emissions but will not succeed to eliminate the application of Diesel Particulate Filters (DPFs) in the future. In the past we have introduced a Multi-Functional Reactor (MFR) prototype, suitable for the abatement of the gaseous and PM emissions of the Low Temperature Combustion (LTC) engine operation. In this work the performance of MFR prototypes under both conventional and advanced combustion engine operating conditions is presented. The effect of the MFR on the fuel penalty associated to the filter regeneration is assessed via simulation. Special focus is placed on presenting the performance assessment in combination with the existing differences in the morphology and reactivity of the soot particles between the different modes of diesel engine operation (conventional and advanced). The effect of aging on the MFR performance is also presented.

Large Eddy Simulation (LES) appears today as a prospective tool for engine study. Even if recent works have demonstrated the feasibility of multi-cycle LES, they have also pointed out a lack of detailed experimental data for validation as well as for boundary condition definition. The acquisition of such experimental data would require dedicated experimental set-ups. Nevertheless, in future industrial applications, unconditional dedicated experimental set-ups will not be the main stream. To overcome this difficulty, a methodology is proposed using system simulation to define fluid boundary conditions (crank-resolved intake/exhaust pressures and temperatures) and wall temperatures. The methodology combines system simulation for the whole experimental set-up and LES for the flow in the combustion chamber as well as a part of the intake and exhaust ducts. System simulation provides the crank-resolved temperature and pressure traces at the LES mesh inlet and outlet.

Burned gas recirculation is emerging as a promising technology to reduce fuel consumption without compromising performance in turbocharged spark ignited engines. This recirculation can be done internally through Internal Gas Residual (IGR) using Variable Valve Timing (VVT) or externally through classical Exhaust Gas Recirculation circuit (EGR). Both have a large impact on combustion. The purpose of the paper is to give clues to get the best compromise at moderate load between these two technologies in terms of fuel consumption. This experimental work was performed on a Gasoline Direct Injection (GDI) engine, 2.0L displacement, dual independent VVT, equipped with a Low Pressure, cooled and catalyzed EGR loop (LP EGR). The load region covers 6 to 10 bar Indicated Mean Effective Pressure (IMEP). EGR rates obtained vary between 0 and 15%. IGR variation is obtained by using the VVT in order to vary the valve overlap. IGR rates vary from 4 to 8%.

In the frame of tighter emission requirements and environmental protection, future standards will soon lead to the use of an OBD soot sensor to monitor DPF leakage. Such a sensor will first be introduced in the US by MY 2015 and then in Europe for Euro 6.2 in 2017. The resistive ceramic sensing technology has been selected by most OEM as the most appropriate. The sensor collects the soot in a time cumulative manner and has an internal heater to clean the ceramic before each measurement sequence. The actual challenge of the hardware is to design a wide band collecting system with a high sensitivity and repeatability circuit processing. Electricfil has overcome major drawbacks of the resistive technology with an innovative sensor tip, with filtration features and a boosting electronic scheme. This sensor integrates internal diagnostic capability at power on and during operation.

Within the Engine Combustion Network (ECN) spray combustion research frame, simultaneous line-of-sight laser extinction measurements and laser-induced incandescence (LII) imaging were performed to derive the soot volume fraction (fv). Experiments are conducted at engine-relevant high-temperature and high-pressure conditions in a constant-volume pre-combustion type vessel. The target condition, called "Spray A," uses well-defined ambient (900 K, 60 bar, 22.8 kg/m₃, 15% oxygen) and injector conditions (common rail, 1500 bar, KS1.5/86 nozzle, 0.090 mm orifice diameter, n-dodecane, 363 K). Extinction measurements are used to calibrate LII images for quantitative soot distribution measurements at cross sections intersecting the spray axis. LII images are taken after the start of injection where quasi-stationary combustion is already established.

A 300 cc gasoline engine has been experimentally and numerically studied to compare PFI and DI operation on naturally-aspirated and turbocharged full load operating points. Experiment outlines the benefits from DI operation in terms of volumetric efficiency, fuel economy and knock propensity but also clearly indicates worse raw engine-out CO emissions. The latter is an indication of the survival of a large scale mixture heterogeneity in this downsized GDI engine even when early injection and intense induced fluid motion are combined. For such a full load operation, the application of optical diagnostics to study mixture heterogeneity cannot be considered because pressure and temperature exceed sustainable levels for transparent materials. Therefore, 3D CFD RANS computations of the intake, injection, combustion and pollutant formation processes including detailed chemistry information are performed to complement the experimental data.

In order to meet the CO₂ challenge, today a wide variety of solutions are developed in the automotive industry such as advanced technologies (downsizing, VVA, VCR), new combustion modes (HCCI, stratified and lean combustion), hybridization, electrification or alternative fuels. Furthermore, couplings between these solutions can be envisaged, increasing considerably the number of degrees of freedom which have to be accounted for in the development of future powertrains. Consequently, for time and cost reasons, it is not obvious to evaluate and optimize the full potential of new concepts only by the mean of experimental investigation. In this context, system simulation appears as a powerful and relevant complement to engine tests for its flexibility and its high CPU efficiency. This paper focuses on the development of a methodology combining both simulation and experimental tools to quantify the interest of innovative solutions in the very first steps of their development.

In the last two decades, piston engine specifications have deeply evolved. Indeed, new challenges nowadays concern the reduction of pollutant emissions (EURO regulations) and CO2 emissions. To satisfy these new requirements, powertrains have become very complex systems including a large number of high technology components (high pressure injectors, turbocharger, Exhaust Gas Recirculation (EGR) loop, after-treatment devices...). In this context, the engine control plays a major role in the development and the optimization of powertrains. Few years ago, engine control strategies were mainly defined by experiments on engine test benches. This approach is not adapted to the complexity of future engines: on the one hand, tests are too expensive and on the other hand, they do not give much information to understand interactions between components. Today, a promising alternative to tests may be the use of 0D/1D simulation tools.

The fuel film thickness resulting from fuel spray impingement on a flat transparent window was characterized in a high pressure high temperature cell for various thermodynamic conditions, injection pressures, injection durations, fuel types and injector technologies by Refractive Index Matching technique. The ambient conditions at injection timing were similar to that of a direct injection spark ignition engine at Top Dead Center, with the distance between the injector tip and the impinging surface set to 10 mm. The spray axis was set normal to the rough transparent window surface at ambient temperatures of 453 K, 573 K and 673 K, and ambient densities of 5.0 kg/m₃, 6.0 kg/m₃ and 6.5 kg/m₃. Injection pressures of 100 and 200 bar were investigated. Three injector technologies were studied: piezo-electric, multi-holes and swirl types. Two fuels, iso-octane and model gasoline, were tested.

In spark-ignition engines, cyclic variability limits the optimisation of operating conditions (choice of spark advance and/or injection timing) since it induces load variations and the occurrence of misfire and/or knock. This, in turn, restricts the operation range of new concepts such as downsizing or stratified combustion. To understand the basic physical phenomena behind cyclic variations, careful experimental studies are necessary to simultaneously characterise the combustion and the unsteady flow in the complete engine set-up. With a well-characterised experimental engine set-up, Large Eddy Simulation (LES) modelling can be easily combined with experiment in order to tackle intricate physical phenomena couplings. This paper describes an experimental database acquired on an optical research engine. The single-cylinder spark-ignition engine is equipped with four valves, a pentroof combustion chamber and a flat piston. The database is dedicated to the validation of LES models.

Regulations in terms of pollutant emissions are becoming more and more constraining. The car manufacturers need to adopt a global optimisation approach of engine and exhaust after-treatment systems. An engine architecture definition coupled to an adapted control strategy seem to be an ideal way to address this issue. The problem is particularly complex, considering the trade off between the drivability which must be maintained, the reduction of the in-cylinder pollutant emissions, the reduction of the fuel consumption and the optimisation of the operating conditions to reach high conversion efficiencies via exhaust gas after-treatment systems. Sophisticated control strategies and models can only be developed with a complete understanding of the physical phenomena occurring in the combustion chamber, thanks to experimental measurements and engine system simulations.

Acoustics influence on internal combustion engine volumetric efficiency is obvious and the use of modeling to represent its effect is largely spread. In this regard, LMS has developed a new 1D model library, namely CFD1D, to model engine intake and exhaust lines under LMS Imagine. Lab AMESim platform. Simulations have been performed at IFP Energies nouvelles (IFPEN) to compare duct system modeling with two different approaches: on the one side, with the brand new 1D library and on the other side, with state-of-the-art 0D lumped parameter models (IFP-Engine library under the same platform). This paper aims at comparing 0D and 1D modeling strategies for two naturally-aspirated spark-ignition engines: a single-cylinder propane-fueled engine and a Honda K20A engine with a dedicated intake system used for a cylinder deactivation concept development. For each application, a 0D and a 1D intake system model is realized, based on real engine test-bed geometry.

Compared to Spark Ignition (SI) engines, Compression Ignition (CI) engines are more efficient because of the higher compression ratios and leaner operation. However, thanks to stoichiometric air fuel ratio, SI engines allow efficient pollutants after treatment, particularly for NOx emissions. In this context, IFP Energies nouvelles (IFPEN) has developed the concept of diesel-gasoline combustion in order to combine the advantages of both fuels and both combustion processes. Focusing on a passenger car application, experiments have been performed using a modified DI turbocharged small diesel engine (the combustion chamber has been redesigned and port fuel injectors have been added). In-Cylinder Fuel Blending (ICFB) using port-fuel-injection of gasoline and optimized direct injection of diesel was used to control combustion phasing and duration. This modified engine can still run on diesel alone.

In a context of a fossil reserve depletion and reduction of greenhouse gases (GHG) emissions, the search for new energy for transport is fundamental. Among those new energies, alternative fuels and especially synthetic fuel from Fischer-Tropsch process (so-called XtL, "X-to-Liquid" fuels) seem to have an interesting potential in terms of availability and GHG emission reduction, according to the feedstock used. Due to the special properties of such products, especially high cetane number, several strategies of incorporation can be envisaged: as a blend in specific basestocks in order to obtain a conventional fuel or a premium fuel or as a pure component. In order to assess these strategies; a standard diesel fuel (B0), a blend with 40%vol of Fischer-Tropsch and a neat Fischer-Tropsch have been tested on a modern downsized high pressure direct injection single-cylinder diesel engine. The used Fischer-Tropsch fuel is a commercial GtL - Gas to Liquid, with a cetane number higher than 80.

The aim of this work is to study the effect of ethanol/gasoline blends on stratified operation in a single-cylinder GDI engine and to build up a large database that will be used to improve engine simulation codes. The effects of three different fuel blends are compared: a reference RON 95 fuel without oxygenates, E20 with 20% in volume of ethanol added to the RON 95 fuel, and E85 corresponding to 85% of ethanol added to the RON 95 fuel. The engine was equipped with a centrally-mounted piezoelectric injector. A wide range of engine speed and load operating conditions were studied: from 1000 to 4000 rpm and from 1.5 to 9 bar IMEP. Injection strategies were optimized using up to three injections per working cycle. It was shown that multi-injection is necessary to improve stratified combustion stability and to limit particulate emissions.

The numerical simulation of internal aerodynamic of automotive combustion chamber is characterised by complex displacements of moving elements (piston, intake/exhaust valves…) and by a strong variation of volume that cause some problems with classical numerical based mesh methods. With those methods (FEM, FVM) which use geometric polyhedral elements (hexaedron, tetrahedron, prismes…), it is necessary to change periodically the mesh to adapt the grid to the new geometry. This step of remeshing is very fastidious and costly in term of engineer time and may reduce the precision of calculation by numerical dissipation during the interpolation process of the variables from one mesh to another. Recently, the researcher community has renewed his interest for the development of a generation of numerical to circumvent the drawbacks of the classical methods.

In spark-ignition engines, Cycle-to-Cycle Variations (CCV) limit the optimization of engine operation since they induce torque variations and the occurrence of misfire and/or knock. A mean for limiting the related negative impact of CCV on fuel consumption and emissions would be control strategies able to address them. At present, engine simulation codes used for control purposes can only describe CCV linked to variations of gas exchanges in the air loop. CCV of the in-cylinder flow motion cannot be naturally captured by classical quasi-dimensional combustion chamber models. A convenient way to mimic CCV is to impose stochastic distributions of the combustion model parameters. Nevertheless, it is not always clear if these perturbations have physical bases as well as realistic ranges of variation.

In this paper, an integrated simulation-based methodology demonstrating feasibility and performance of several electric-hybrid concepts is developed. Several advanced tools are coupled to define the specifications of each component of the hybrid powertrain, to select the most promising hybrid architecture and finally to assess the proposed powertrain with regard to CO2 and pollutants emissions. Concurrent minimization of NOx and CO2 emissions enables to find the best compromise to fulfil Euro 6 standards while lowering fuel consumption. This stage consists in an iterative co-optimization of the power split strategies between the electric drive and the Diesel engine and of the engine settings (injection pressure, EGR rate, etc.). The methodology combines optimal control laws and optimization methodology based on global statistical models using single-cylinder design of experiments. After several iterations, this method allows to find the optimal NOx/CO2 trade-off curve.

Dedicated experiments were performed in an optically-accessible, constant volume combustion vessel whose geometry and aerodynamic flow was representative of a pentroof SI engine combustion chamber. A detailed characterization of the flowfield was conducted in several near-wall regions where flame-wall interaction occurs using high-speed Particle Image Velocimetry (PIV). Simultaneous heat flux measurements were also performed at these same spatial locations. From a numerical point of view, current Reynolds Averaged Navier Stokes (RANS) or Large Eddy Simulation (LES) models take into account the effects of the wall on the flame however the effects of the turbulent flame-wall interaction on wall heat flux are not accounted for. Direct Numerical Simulations (DNS) of a 2D, premixed, steady-state V-flame were performed in order to aid the development and validation of a new model based on the flame surface density concept in order to take into account flame-wall interaction effects [1].