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The recent development of biofuel production worldwide is closely linked to GHG savings objectives and to regional agricultural policies. Many existing studies intend to evaluate the net non renewable energy and GHG savings associated to the various biofuel production pathways. However, there is no consensus on the results of those studies. The main explanations of variations among the results are the following: energy consumption and GHG emissions of the reference fossil pathway, data used for the representation of farming processes and biofuel production processes, accounting for carbon storage in agricultural soils, reference use of the land, choice of an allocation method in case of coproduction. There is a strong drive in the European Union for a certification on the sustainability of biofuel pathways.

In the last few years, the effect of diabatic test conditions on compressor performance maps has been widely investigated, leading some Authors to propose different correction models. The accuracy of turbocharger performance map constitute the basis for the tuning and validation of a numerical method, usually adopted for the prediction of engine-turbocharger matching. Actually, it is common practice in automotive applications to use simulation codes, which can either require measured compression ratio and efficiency maps as input values or calculate them “on the fly” throughout specific sub-models integrated in the numerical procedures. Therefore, the ability to correct the measured performance maps taking into account internal heat transfer would allow the implementation of commercial simulation codes used for engine-turbocharger matching calculations.

Detailed and fast combustion models are necessary to support design of Diesel engines with low emission and fuel consumption. Over the years, the importance of turbulence chemistry interaction to correctly describe the diffusion flame structure was demonstrated by a detailed assessment with optical data from constant-volume vessel experiments. The main objective of this work is to carry out an extensive validation of two different combustion models which are suitable for the simulation of Diesel engine combustion. The first one is the Representative Interactive Flamelet model (RIF) employing direct chemistry integration. A single flamelet formulation is generally used to reduce the computational time but this aspect limits the capability to reproduce the flame stabilization process. To overcome such limitation, a second model called tabulated flamelet progress variable (TFPV) is tested in this work.

In former high compression ratio Diesel engines a single injection was used to introduce the fuel into the combustion chamber. With actual direct injection engines which exhibit a compression ratio between 17:1 and 18:1 single or multiple early injections called “pilot injections” are also added in order to reduce the combustion noise. For after-treatment reasons a late injection during the expansion stroke named “post injection” may also be used in some operating conditions. Investigations have been conducted on lower compression ratio Diesel engine and in high EGR rate operating conditions to evaluate the benefits of multiple injection strategies to improve the trade off between engine emissions, noise and fuel economy.

In nowadays diesel engine, the turbocharger system plays a very important role in the engine functioning and any loss of the turbine efficiency can lead to driveability problems and the increment of emissions. In this paper, a VGT turbocharger fault detection system is proposed. The method is based on a physical model of the turbocharger and includes an estimation of the turbine efficiency by a nonlinear adaptive observer. A sensitivity analysis is provided in order to evaluate the impact of different sensors fault, (drift and bias), used to feed the observer, on the estimation of turbine efficiency error. By the means of this analysis a robust variable threshold is provided in order to reduce false detection alarm. Simulation results, based on co-simulation professional platform (AMEsim© and Simulink©), are provided to validate the strategy.

Tracer laser induced fluorescence (LIF) imaging of piston-top fuel films has been performed within the combustion chamber of an optically-accessible, single cylinder Diesel engine. The first objective of the study was to adapt the tracer LIF technique so as to perform in-cylinder imaging of the fuel films under reacting (i.e. combustion) conditions. The results obtained in a wall-guided, combustion chamber operating under highly dilute, Diesel low temperature combustion (LTC) conditions reveal the significant presence of late-cycle piston-top fuel films. Furthermore, it is believed that these fuel films contribute to engine-out hydrocarbon (HC) emissions via a mechanism of flash boiling. An attempt was also made to evaluate the role of fuel volatility on fuel film lifetimes. This was achieved by using a 50/50 fuel mixture of two single component fuels whose boiling points correspond to moderately high and low volatility components of standard Diesel fuel.

Detailed chemistry and turbulence-chemistry interaction need to be properly taken into account for a realistic combustion simulation of IC engines where advanced combustion modes, multiple injections and stratified combustion involve a wide range of combustion regimes and require a proper description of several phenomena such as auto-ignition, flame stabilization, diffusive combustion and lean premixed flame propagation. To this end, different approaches are applied and the most used ones rely on the well-stirred reactor or flamelet assumption. However, well-mixed models do not describe correctly flame structure, while unsteady flamelet models cannot easily predict premixed flame propagation and triple flames. A possible alternative for them is represented by transported probability density functions (PDF) methods, which have been applied widely and effectively for modeling turbulent reacting flows under a wide range of combustion regimes.

The implementation and the combination of advanced boundary conditions and subgrid scale models for Large Eddy Simulation (LES) in the multi-dimensional open-source CFD code OpenFOAM® are presented. The goal is to perform reliable cold flow LES simulations in complex geometries, such as in the cylinders of internal combustion engines. The implementation of a boundary condition for synthetic turbulence generation upstream of the valve port and of the compressible formulation of the Wall-Adapting Local Eddy-viscosity sgs model (WALE) is described. The WALE model is based on the square of the velocity gradient tensor and it accounts for the effects of both the strain and the rotation rate of the smallest resolved turbulent fluctuations and it recovers the proper y₃ near-wall scaling for the eddy viscosity without requiring dynamic procedure; hence, it is supposed to be a very reliable model for ICE simulation.

In order to address the CO₂ emissions issue and to diversify the energy for transportation, CNG (Compressed Natural Gas) is considered as one of the most promising alternative fuels given its high octane number. However, gaseous injection decreases volumetric efficiency, impacting directly the maximal torque through a reduction of the cylinder fill-up. To overcome this drawback, both independent natural gas and gasoline indirect injection systems with dedicated engine control were fitted on a RENAULT 2.0L turbocharged SI (Spark Ignition) engine and were adapted for simultaneous operation. The main objective of this innovative combination of gas and liquid fuel injections is to increase the volumetric efficiency without losing the high knocking resistance of methane.

In future decarbonized scenarios, hydrogen is widely considered as one of the best alternative fuels for internal combustion engines, allowing to achieve zero CO2 emissions at the tailpipe. However, NOx emissions represent the predominant pollutants and their production has to be controlled. In this work different strategies for the control and abatement of pollutant emissions on a H2-fueled high-performance V8 twin turbo 3.9L IC engine are tested. The characterization of pollutant production on a single-cylinder configuration is carried out by means of the 1D code Gasdyn, considering lean and homogeneous conditions. The NOx are extremely low in lean conditions with respect to the emissions legislation limits, while the maximum mass flow rate remains below the turbocharger technical constraint limit at λ=1 only.

The reduction of NOx emissions required by the future Euro 6 standards leads engine manufacturers to develop Diesel Homogeneous Charge Compression Ignition (HCCI) combustion processes. Because this concept allows reducing both NOx and particulates simultaneously, it appears as a promising way to meet the next environmental challenges. Unfortunately, HCCI combustion often increases CO and HC emissions. Conventional oxidation catalyst technologies, currently used for Euro 4 vehicles, may not be able to convert these emissions because of the saturation of active catalytic sites. As a result, such increased CO and HC emissions have to be reduced under standard levels using innovative catalysts or emergent technologies. The work reported in this paper has been conducted within the framework of the PAGODE project (PSA, IFP, Chalmers University, APTL, CRF, Johnson Matthey and Supelec) and financed by the European Commission.

The aim of the paper is to provide simple and accurate analytical formulae describing the straight motion of a road vehicle. Such formulae can be used to compute either the steering torque or the additional rolling resistance induced by vehicle side-slip angle. The paper introduces a revised formulation of the Handling Diagram Theory to take into account tire ply-steer, conicity and road banking. Pacejka’s Handling Diagram Theory is based on a relatively simple fully non-linear single track model. We will refer to the linear part of the Handling Diagram, since straight motion will be considered only. Both the elastokinematics of suspension system and tire characteristics are taken into account. The validation of the analytical expressions has been performed both theoretically and after a subjective-objective test campaign. By means of the new and unreferenced analytical formulae, practical hints are given to set to zero the steering torque during straight running.

A comprehensive research is presented aiming at assessing the ride comfort of subjects seated into road or off-road vehicles. Although many papers and books have appeared in the literature, many issues on ride comfort are still to be understood, in particular, the paper investigates the mutual effects of the posture and the vibration caused mostly from road unevenness. The paper is divided into two parts. In the first part, a mathematical model of a seated subject is validated by means of actual measurements on human subjects riding on a car. Such measurements refer to the accelerations acting at the subject/seat interface (vertical acceleration at the seat cushion and horizontal acceleration at the seat back). A proper dummy is used to derive the seat stiffness and damping.

Transient and steady-state kinetic data are herein presented to analyze the inhibiting effect of ammonia on the NH₃-SCR of NO at low temperatures over a Fe-zeolite commercial catalyst for vehicles. It is shown that in SCR converter models a rate expression accounting for NH₃ inhibition of the Standard SCR reaction is needed in order to predict the specific dynamics observed both in lab-scale and in engine test bench runs upon switching on and off the ammonia feed. Two redox, dual site kinetic models are developed which ascribe such inhibition to the spill-over of ammonia from its adsorption sites, associated with the zeolite, to the redox sites, associated with the Fe promoter. Better agreement both with lab-scale intrinsic kinetic runs and with engine test-bench data, particularly during transients associated with dosing of ammonia to the SCR catalyst, is obtained assuming slow migration of NH₃ between the two sites.

The purpose of the ELEVATE (European Low Emission V4 Automotive Two-stroke Engine) industrial research project is to develop a small, compact, light weight, high torque and highly efficient clean gasoline 2-stroke engine of 120 kW which could industrially replace the relatively big existing automotive spark ignition or diesel 4-stroke engine used in the top of the mid size or in the large size vehicles, including the minivan vehicles used for multi people and family transportation. This new gasoline direct injection engine concept is based on the combined implementation on a 4-stroke bottom end of several 2-stroke engine innovative technologies such as the IAPAC compressed air assisted direct fuel injection, the CAI (Controlled Auto-Ignition) combustion process, the D2SC (Dual Delivery Screw SuperCharger) for both low pressure engine scavenging and higher pressure IAPAC air assisted DI and the ETV (Exhaust charge Trapping Valve).

Within the framework of the French research program PREDIT, a study was undertaken by ADEME, IFP, LGRE, PSA Peugeot Citroën and Umicore, whose main objective was a better understanding of the NOx storage and reduction phenomena on an aged, sulfated and desulfated NOx-trap. The target of this work was to use the information on catalyst working conditions to optimize catalyst management for a gasoline direct injection engine. The catalysts were characterized on both engine and synthetic gas benches. Aging and poisoning phenomena were studied and a variety of different chemical analytical tools were used. The behavior of two different thermally aged cores was investigated under rich conditions on a synthetic gas test bench. The dependence of the NOx regeneration efficiency of the traps is reported for several operating parameters, including reductant concentrations, durations of the rich pulse and trap loadings.

The mixing and combustion processes of short double Diesel injections are investigated by optical diagnostics. A single hole Common Rail Diesel injector allowing high injection pressure up to 120MPa is used. The spray is observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. Three configurations are studied: a single short injection serving as a reference case and two double short injections with short and long dwell time (time between the injections). Several optical diagnostics were performed successively. The mixing process is studied by normalized Laser Induced Exciplex Fluorescence giving access to the vapor fuel concentration fields. In addition, the flow fields both inside and outside the jets are characterized by Particle Imaging Velocimetry.

The air entrainment of multi-hole diesel injection is investigated by high speed Particle Image Velocimetry (PIV) using a multi-hole common rail injector with an injection pressure of 100 MPa. The sprays are observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a diesel engine during injection. Typical ambient temperature of 800K and ambient density of 25 kg/m3 are chosen. The air entrainment is studied with the PIV technique, giving access to the velocity fields in the surrounding air and/or in the interior of two neighboring jets. High acquisition rate of 5000 Hz, corresponding to 200 μs between two consecutive image pairs is obtained by a high-speed camera coupled with a high-speed Nd:YLF laser. The effect of neighboring jets interaction is studied by comparing four injectors with different numbers of holes (4, 6, 8 and 12) with similar static mass flow rate per hole.

The reduction of particulate emissions from Diesel engines is a key issue to meet future emission standards. Particulate traps represent an attractive solution to the problem of this source of pollution. However, they have the disadvantage of requiring periodic and safe regeneration to release exhaust back pressure and to recover filtration efficiency. Natural regeneration of the particulate filter may occur. Nevertheless, with light-duty vehicles and their low level of exhaust gas temperature, it may be necessary to facilitate or force the regeneration. The objective of this work is to give an overview of the possibilities offered by the engine management system to increase significantly exhaust gas temperatures. Thus, different engine tunes, through injection timing, boost pressure or EGR rate, may be sufficient to ensure safe regeneration of the trap.

Multi-dimensional models represent today consolidated tools to simulate the combustion process in HCCI and diesel engines. Various approaches are available for this purpose, it is however widely accepted that detailed chemistry represents a fundamental prerequisite to obtain satisfactory results when the engine runs with complex injection strategies or advanced combustion modes. Yet, integrating such mechanisms generally results in prohibitive computational cost. This paper presents a comprehensive methodology for fast and efficient simulations of combustion in internal combustion engines using detailed chemistry. For this purpose, techniques to tabulate the species reaction rates and to reduce the chemical mechanisms on the fly have been coupled.