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With the increase of heavy-duty transportation, more fuel efficient technologies and services have become of great importance due to their environmental and economical impacts for the fleet managers. In this paper, we first develop a new analytical model of the heavy-truck for its dynamics and its fuel consumption, and valid the model with experimental measurements. Then, we propose a bi-level optimization approach to reduce the fuel consumption, thus the CO2 emissions, while ensuring several safety constraints in real-time. Numerical results show that important reduction of the fuel consumption can be achieved, while satisfying imposed safety constraints.

Low speed pre-ignition (LSPI) in downsized spark-ignition engines has been studied for more than a decade but no definitive explanation has been found regarding the exact sources of auto-ignition. No single mechanism can explain all the occurrences of LSPI and that each engine should be considered as a particular case supporting different conditions for auto-ignition. In a different context, dual fuel Diesel-Methane engines have been more recently studied in large to medium bore compression ignition engines. However, if Dual Fuel combustion is less knock sensitive, LSPI remains one of the main limitations of low-end torque also for dual fuel engines. Indeed, in some cases, premature ignition of CNG can be observed before the Diesel pilot injection as LSPI can classically be observed before the spark in gasoline engines. This article aims at highlighting the similarities and discrepancies between LSPI phenomena in SI gasoline and dual fuel engines.

In this paper, a sectional soot model coupled to a tabulated combustion model is compared with measurements from an experimental engine database. The sectional soot model, based on the work of Vervisch-Klakjic (Ph.D. thesis, Ecole Centrale Paris, Paris, 2011) and Netzell et al. (P. Combust. Inst., 31(1):667-674, 2007), has been implemented into IFPC3D (Bohbot et al., Oil Gas Sci Technol, 64(3):309-335, 2009), a 3D RANS solver. It enables a complex modeling of soot particles evolution, in a 3D Diesel simulation. Five distinct source terms are applied to each soot section at any time and any location of the flow. The inputs of the soot model are provided by a tabulated combustion model derived from the Engine Approximated Diffusion Flame (EADF) one (Michel and Colin, Int. J. Engine Res., 2013) and specifically modified to include the minor species required by the soot model.

The more and more severe regulations on exhaust emissions from vehicles and the worldwide demand for fuel consumption reduction impose continuous improvements of the engine thermal efficiency. Base engine geometrical setups are important aspects which have to be taken into account to improve the engine efficiency. This paper discusses the influence of the bore-to-stroke ratio on emissions, fuel consumption and full load performances of a Diesel engine. The expected advantage of a reduced bore-to-stroke ratio is mainly a decrease of the thermal losses, due to a higher volume-to-surface ratio, reducing the wall surfaces, responsible for the heat losses, per volume of gas. The advantages concerning the wall heat losses are opposed to the disadvantages of lower volumetric efficiency, as a smaller bore requires smaller valve diameter. Additionally does a reduction of the bore-to-stroke ratio lead to an increase of the friction losses, as the mean piston speed increases.

Legal constraints concerning CO2 emissions have made the improvement of light duty vehicle efficiency mandatory. In result, vehicle powertrain and its development have become increasingly complex, requiring the ability to assess rapidly the effect of several technological solutions, such as hybridization or internal combustion engine (or ICE) downsizing, on vehicle CO2 emissions. In this respect, simulation is nowadays a common way to estimate a vehicle's fuel consumption on a given driving cycle. This estimation can be done with the knowledge of vehicle main characteristics, its transmission ratio and efficiency and its internal combustion engine fuel consumption map. While vehicle and transmission parameters are relatively easy to know, the ICE consumption map has to be obtained through either test bench measurements or computation.

The 3-Zones Extended Coherent Flame Model (ECFM3Z) and the Tabulated Kinetics for Ignition (TKI) auto-ignition model are widely used for RANS simulations of reactive flows in Diesel engines. ECFM3Z accounts for the turbulent mixing between one zone that contains compressed air and EGR and another zone that contains evaporated fuel. These zones mix to form a reactive zone where combustion occurs. In this mixing zone TKI is applied to predict the auto-ignition event, including the ignition delay time and the heat release rate. Because it is tabulated, TKI can model complex fuels over a wide range of engine thermodynamic conditions. However, the ECFM3Z/TKI combustion modeling approach requires an efficient predictive spray injection calculation. In a Diesel direct injection engine, the turbulent mixing and spray atomization are mainly driven by the liquid/gas coupling phenomenon that occurs at moving liquid/gas interfaces.

A practical Gasoline Compression Ignition (GCI) concept is presented that works on standard European 95 RON E10 gasoline over the whole speed/load range. A spark is employed to assist the gasoline autoignition at low loads; this avoids the requirement of a complex cam profile to control the local mixture temperature for reliable autoignition. The combustion phasing is controlled by the injection pattern and timing, and a sufficient degree of stratification is needed to control the maximum rate of pressure rise and prevent knock. With active control of the swirl level, the combustion system is found to be relatively robust against variability in charge motion, and subtle differences in fuel reactivity. Results show that the new concept can achieve very low fuel consumption over a significant portion of the speed/load map, equivalent to diesel efficiency. The efficiency is worse than an equivalent diesel engine only at low load where the combustion assistance operates.

The hydrogen internal combustion engine is a promising alternative to fossil fuel-based engines, which, in a short time, can reduce the carbon footprint of the ground transport sector. However, the high heat release rates associated with hydrogen combustion results in higher NOx emissions. The NOx production can be mitigated by diluting the in-cylinder mixture with air, Exhaust Gas Recirculation (EGR) or water injected in the intake manifold. This study aims at assessing these dilution options on the emissions, efficiency, combustion performance and boosting effort. These dilution modes are, at first, compared on a single cylinder engine (SCE) with direct injection of hydrogen in steady state conditions. Air and EGR dilutions are then evaluated on a corresponding 4-cylinder engine by 0D simulation on a complete map under NOx emission constraint.

An automatic mesh generation process for a body fitted 3D CFD code is presented in this paper along with the methodology to guarantee the mesh quality. This tool named OMEGA (Optimized MEsh Generation Automation) uses a direct coupling procedure between the IFP-C3D solver and a hybrid mesher Centaur. Thanks to this automatic procedure, the engineering time needed for body fitted 3D CFD simulation in internal combustion engines is drastically reduced from a few weeks to a few hours. Valve and piston motion laws are just given as input files and geometries and meshes are automatically moved and generated. Unlike other procedures, this automatic mesh generation does not use an intermediate geometry discretization (STL file, tetrahedral surface mesh) but directly the original CAD that has been modified thanks to the geometry motion functionalities integrated into the mesher.

The Engine Combustion Network (ECN) is becoming a leading group concerning the experimental and computational analysis of Engine combustion. In order to establish a coherent database for model validation, all the institutions participating to the experimental effort carry out experiments at well-defined standard conditions (in particular at Spray A conditions: 22.8kg/m3, 900K, 0% and 15% O2) and with Diesel injectors having the same specifications. Due to the rising number of ECN participants and also to unavoidable damages, additional injectors are required. This raises the question of injector's characteristics reproducibility and of the appropriate method to introduce such new injectors in the ECN network. In order to investigate this issue, a set of 8 new injectors with identical nominal Spray A specification were purchased and 4 of them were characterized using ECN standard diagnostics.

Recent work has demonstrated the potential of gasoline-like fuels to reduce NOx and particulate emissions when used in compression ignition engines. In this context, low research octane number (RON) gasoline, a refinery stream derived from the atmospheric crude oil distillation process, has been identified as a highly valuable fuel. In addition, thanks to its higher H/C ratio and energy content compared to diesel, CO2 benefits are also expected when used in such engines. In previous studies, different cetane number (CN) fuels have been evaluated and a CN 35 fuel has been selected. The assessment and the choice of the required engine hardware adapted to this fuel, such as the compression ratio, bowl pattern and nozzle design have been performed on a single cylinder compression-ignition engine.

Meeting Euro 6d NOx emission regulations lower than 80 mg/km for light duty diesel (60 mg/km gasoline) vehicles remains a challenge, especially during cold-start tests at which the selective catalyst reduction (SCR) system does not work because of low exhaust gas temperatures (light-off temperature around 200 °C). While several exhaust aftertreatment system (EATS) designs are suggested in literature, solutions with gaseous ammonia injections seem to be an efficient and cost-effective way to enhance the NOx abatement at low temperature. Compared to standard SCR systems using urea water solution (UWS) injection, gaseous NH3 systems allow an earlier injection, prevent deposit formation and increase the NH3 content density. However non-uniform ammonia mixture distribution upstream of the SCR catalyst remains an issue. These exhaust gas/ NH3 inhomogeneities lead to a non-optimal NOx reduction performance, resulting in higher than expected NOx emissions and/or ammonia slip.

The present paper is concerned with part of the work performed by Renault, IFPEN and Politecnico di Torino within a research project founded by the European Commission. The project has been focused on the development of a dedicated CNG engine featuring a 25% decrease in fuel consumption with respect to an equivalent Diesel engine with the same performance targets. To that end, different technologies were implemented and optimized in the engine, namely, direct injection, variable valve timing, LP EGR with advanced turbocharging, and diluted combustion. With specific reference to diluted combustion, it is rather well established for gasoline engines whereas it still poses several critical issues for CNG ones, mainly due to the lower exhaust temperatures. Moreover, dilution is accompanied by a decrease in the laminar burning speed of the unburned mixture and this generally leads to a detriment in combustion efficiency and stability.

Hydrogen may be used to feed a fuel cell or directly an internal combustion engine as an alternative to current fossil fuels. The latter option offers the advantages of already existing hydrocarbon fuel engines - autonomy, pre-existing and proven technology, lifetime, controlled cost, existing industrial tools and short time to market - with a very low carbon footprint and high tolerance to low purity hydrogen. Hydrogen is expected to be relevant for light and heavy duty applications as well as for off road applications, but currently most of research focus on small engine and especially spark ignition engine which is easily adaptable. This guided us to select modern high-efficient gasoline-based engines to start the investigation of hydrogen internal combustion engine development. This study aims to access the properties and limitations of hydrogen combustion on a high-efficiency spark ignited single cylinder engine with the support of the 3D-CFD computation.

Increasing the internal combustion engine efficiency is necessary to decrease their environmental impact. Several combustion systems demonstrated the interest of low temperature combustion to move toward this objective. However, to ensure a stable combustion, the use of additives has been considered in a several studies. Amongst them, 2-Ethylhexyl nitrate (EHN) is considered as a good candidate for these systems but characterizing its chemical effect is required to optimize its use. In this study, its promoting effect (0.1 - 1% mol.) on combustion has been investigated experimentally and numerically in order to better characterize its behavior under different thermodynamic and mixture. Rapid compression machine (RCM) experiments were carried out at equivalence ratio 0.5 and pressure 10 bar, from 675 to 995 K. The targeted surrogate fuel is a mixture of toluene and n-heptane in order to capture the additive effect on both cool flame and main ignition.

The Diesel engine has now become a vital component of the transport sector, in view of its performance in terms of efficiency and therefore CO2 emissions some 25 % less than a traditional gasoline engine, its main competitor. However, the introduction of more and more stringent regulations on engine emissions (NOx, PM) requires complex after-treatment systems and combustion strategies to decrease pollutant emissions (regeneration strategies, injection strategies, …) with some penalty in fuel consumption. It becomes necessary to find new ways to improve the Diesel efficiency in order to maintain its inherent advantage. In the present work, we are looking for strategies and technologies to reduce Diesel engine fuel consumption. Based on the observation that large Diesel engines have a better efficiency than the smaller ones, a detailed thermodynamic combustion analysis of one Heavy Duty (HD) engine and two Passenger car (PC) engines is performed to understand these differences.

Diesel spray mixture formation is investigated at target conditions using multiple diagnostics and laboratories. High-speed Particle Image Velocimetry (PIV) is used to measure the velocity field inside and outside the jet simultaneously with a new frame straddling synchronization scheme. The PIV measurements are carried out in the Engine Combustion Network Spray A target conditions, enabling direct comparisons with mixture fraction measurements previously performed in the same conditions, and forming a unique database at diesel conditions. A 1D spray model, based upon mass and momentum exchange between axial control volumes and near-Gaussian velocity and mixture fraction profiles is evaluated against the data.

This paper proposes a method to detect an intake manifold leakage for a Diesel engine with a dual loop EGR system. The intake manifold leak has a strong impact on the engine performances by changing the intake manifold burned gas ratio. This fault is analyzed according to the control structure used and also according to the EGR operating mode. The paper proposes a diagnosis algorithm to detect the intake manifold leak in sequential or simultaneous use of the two EGR paths. The sensors considered are the mass air flow meter, the intake manifold pressure sensor, the exhaust equivalence ratio sensor and the differential pressure sensor (across the HP EGR valve). The diagnosis is based on a criteria that uses the redundancy between these sensors and air system models or estimators. The diagnosis threshold depends on the engine operating conditions as well as the sensor or model dispersions.

Increasingly restrictive emission standards and CO2 targets drive the need for innovative engine architectures that satisfy the design constraints in terms of performance, emissions and drivability. Downsizing is one major trend for Spark-Ignition (SI) engines. For downsized SI engines, the increased boost levels and compression ratios may lead to a higher propensity of abnormal combustions. Thus increased levels of Exhaust Gas Recirculation (EGR) are used in order to limit the appearance of knock and super-knock. The drawback of high EGR rates is the increased tendency for Cycle-to-Cycle Variations (CCV) it engenders. A possible way to reduce CCV could be the generation of an increased in-cylinder turbulence to accelerate the combustion process. To manage all these aspects, 1D simulators are increasingly used. Accordingly, adapted modeling approaches must be developed to deal with all the relevant physics impacting combustion and pollutant emissions formation.

Thermal management is a key issue to minimize fuel consumption while dealing with pollutant emissions. It paves the way for developing new methods and tools in order to assess the effects of warm up phase with different drivetrains architectures and to define the most suitable solution to manage oil and coolant temperatures. DEVICE (Downsized hybrid Diesel Engine for Very low fuel ConsumptIon and CO2 Emissions) project consists in designing hybrid powertrain to cut off significantly CO2 emissions. It combines a 2-cylinder engine with an electric motor and a 7-gear dual clutch transmission. Hybridization and downsizing offer a great improvement of fuel economy and it is valuable to study their effects on thermal management. Hence, a dedicated AMESim platform is developed to model the fluids temperatures as well as the energy balance changes due to the powertrain architecture.