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The simultaneous reduction of engine-out nitrogen oxide (NOx) and particulate emissions via low-temperature combustion (LTC) strategies for compression-ignition engines is generally achieved via the use of high levels of exhaust gas recirculation (EGR). High EGR rates not only result in a drastic reduction of combustion temperatures to mitigate thermal NOx formation but also increases the level of pre-mixing thereby limiting particulate (soot) formation. However, highly pre-mixed combustion strategies such as LTC are usually limited at higher loads by excessively high heat release rates leading to unacceptable levels of combustion noise and particulate emissions. Further increasing the level of charge dilution (via EGR) can help to reduce combustion noise but maximum EGR rates are ultimately restricted by turbocharger and EGR path technologies.

The authors present the supervisory control of a parallel hybrid powertrain, focusing on several issues related to the real-time implementation of optimal control based techniques, such as the Equivalent Consumption Minimization Strategies (ECMS). Real-time implementation is introduced as an intermediate step of a complete chain of tools aimed at investigating the supervisory control problem. These tools comprise an offline optimizer based on Pontryagin Minimum Principle (PMP), a two-layer real-time control structure, and a modular engine-in-the-loop test bench. Control results are presented for a regulatory drive cycle with the aim of illustrating the benefits of optimal control in terms of fuel economy, the role of the optimization constraints dictated by drivability requirements, and the effectiveness of the feedback rule proposed for the adaptation of the equivalence factor (Lagrange multiplier).

The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap. This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR.

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.

Diversifying energy resources and reducing greenhouse gas emissions are key priorities in the forthcoming years for the automotive industry. Currently, among the different solutions, sustainable biofuels are considered as one of the most attractive answer to these issues. This paper deals with the vehicle application of an innovative diesel fuel formulation using Ethanol to tackle these future challenges. The main goal is to better understand the impact of using biofuel blends on engine behavior, reliability and pollutants emissions. This alternative oxygenated fuel reduces dramatically particulate matter (PM) emissions; this paves the way to improve the NOx/PM/CO₂ trade-off. Another major interest is to avoid adding a particulate filter in the exhaust line and to avoid modifying powertrain and vehicle hardware and therefore to minimize the overall cost to fulfill upcoming emission regulations.

Facing the CO2 emission reduction challenge, the combination of downsizing and turbocharging appears as one of the most promising solution for the development of high efficiency gasoline engines. In this context, as knock resistance is a major issue, limiting the performances of turbocharged downsized gasoline engines, fuel properties are more than ever key parameters to achieve high performances and low fuel consumption's levels. This paper presents a combustion study carried out into the GSM consortium of fuel quality effects on the performances of a downsized turbocharged Direct Injection SI engine. The formulation of two adapted fuel matrix has allowed to separate and evaluate the impacts of three major fuel properties: Research Octane Number (RON), Motor Octane Number (MON) and Latent Heat of Vaporization (LHV). Engine tests were performed on a single cylinder engine at steady state operating condition.

Among the existing concepts that help to improve the efficiency of spark ignition engines at part load, Controlled Auto-Ignition™ (CAI™) is an effective way to lower both fuel consumption and pollutant emissions without major modifications of the engine design. The CAI™ concept is based on the auto-ignition of a fuel mixture highly diluted with burnt gases in order to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. Large amounts of burnt gases can be trapped in the cylinder by re-breathing them through the exhaust ports during the intake stroke. For that, a 2-step exhaust valve-lift profile is used. The interaction between the intake and exhaust flows during the intake stroke was identified as a key parameter to control the subsequent combustion in a CAI™ port fuel injected (PFI) engine.

Environment protection issues regarding CO2 emissions as well as customers requirements for fun-to-drive and fuel economy explain the strong increase of Diesel engine on European market share in all passenger car segments. To comply future purposes of emission regulations, particularly dramatic decrease in NOx emissions, technology need to keep upgrading; the reduction of the volumetric compression ratio (VCR) is one of the most promising research ways to allow a simultaneous increase in power at full load and NOx / PM trade-off improvement at part load. This study describes the combustion effects of the reduction of compression ratio and quantifies improvements obtained at full load and part load running conditions on a HSDI Common Rail engine out performance (power, fuel consumption, emissions and noise). Potential and limitations of a reduced compression ratio from 18:1 to 14:1 are underlined.

Low temperature combustion concept as HCCI is one of the most promising research ways to comply future emission regulations of Diesel passenger vehicles. IFP promoted this concept with NADI™ (Narrow Angle Direct Injection) combustion design whose original approach lies on a fuel spray guided by the bowl central tip to the re-entrant. For full load operating range, one of the key issue for success is to use as much as possible available air in the combustion chamber in order to reach low value of air fuel ratio, and therefore high value of specific power and specific torque. In this study, engine tests on a single cylinder engine with NADI™ concept are performed at full load; 3-D calculations as well as air/fuel mixing process visualizations in a constant volume vessel with optical access allowed to establish criteria for helping future combustion system design for full load operation.

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.

Pollutants emissions from transportation have become a major focus of environmental concerns in the last decades. Many alternative fuels are under consideration, among which Natural Gas as fossil resource offering an advantageous potential to reduce local emissions. The European Commission has set an objective of 10% of Natural Gas consumption for the transport sector by 2020. In a sustainable development view, both vehicle emissions and energy supply chain analysis from well to wheel must be addressed. Even if the main focus today is on CO2 emissions, it is interesting to evaluate the pollutant emissions of the whole Well to Wheel chain. Besides, as the potential of reducing pollutant emissions of vehicle (due to the improvement of engines and severization of norms), looking at pollutant emissions of the Well to Tank part of the chain could show the possible further improvements. Former studies exist, comparing Natural Gas to conventional and non conventional fuels.

Compressed natural gas (CNG) is considered as one of the most promising alternative fuels for transportation due to its ability to reduce greenhouse gas emissions (CO2, in particular) and its abundance. An earlier study from IFP has shown that CNG has a considerable potential when used as a fuel for a dedicated downsized turbo-charged SI engine on a small urban vehicle. To take further advantage of CNG assets, this approach can be profitably extended by adding a small secondary (electrical) power source to the CNG engine, thus hybridizing the powertrain. This is precisely the focus of the new IFP project, VEHGAN, which aims to develop a mild-hybrid CNG prototype vehicle based on a MCC smart car equipped with a reversible starter-alternator and ultra-capacitors (Valeo Starter Alternator Reversible System, StARS).

A 3 way catalytic converter (3WCC) model based on a global kinetic model was developed and validated against laboratory scale and engine test bench experiments. Various equivalence ratios and temperatures were tested. A methodology was finalized and applied to calibrate the kinetic constants. Laboratory scale experiments were first used to characterize the reaction mechanism during light-off, including the way reduction and oxidation reactions begin and compete with each other when temperature increases. The numerical results are in good agreement with the laboratory scale light-off results. Also, when adapted to simulate the engine test bench experiments, the model is able to correctly reproduce both the light-off tests and the 3WCC conversion efficiency evolution versus equivalence ratio. A calibration method in two steps was thus established and successfully used. The combination of modeling with experimental work appeared to be a powerful tool to determine the reaction mechanism.

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.

Facing more and more stringent regulations, new solutions are developed to decrease pollutant emissions. One of them have shown promising and relevant results. It consists of the use of ethanol as a blending component for diesel fuel Nevertheless, the addition of ethanol to Diesel fuel affects some key properties such as the flash point. Consequently, Diesel blends containing ethanol become highly flammable at a temperature around ambient temperature. This study proposes to improve the formulation of ethanol based diesel fuel in order to avoid flash point drawbacks. First, a focus on physical and chemical properties is done for ethanol based diesel fuels with and without flash point improvement. Second, blends are tested on a passenger car diesel engine, under a wide operating range conditions from low load low speed up to maximum power. The main advantage of the ethanol based fuels generate low smoke level, that allows using higher EGR rate, thus leading to an important NOx decrease.

Among the existing concepts that help to improve the efficiency of spark-ignition engines at part load, Controlled Auto-Ignition™ (CAI™) is an effective way to lower both fuel consumption and pollutant emissions. This combustion concept is based on the auto-ignition of an air-fuel-mixture highly diluted with hot burnt gases to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. To minimize the costs of conversion of a standard spark-ignition engine into a CAI engine, the present study is restricted to a Port Fuel Injection engine with a cam-profile switching system and a cam phaser on both intake and exhaust sides. In a 4-stroke engine, a large amount of burnt gases can be trapped in the cylinder via early closure of the exhaust valves. This so-called Negative Valve Overlap (NVO) strategy has a key parameter to control the amount of trapped burnt gases and consequently the combustion: the exhaust valve-lift profile.

Among the last years, environmental concerns have raised the interest for biofuels. Ethanol, blended with gasoline seems particularly suited for the operation of internal combustion engines, and has been in use for severals years in some countries. However, it has a strong impact on engine performance, which is emphasized on recent engine architectures, with downsizing through turbocharging and variable valve actuation. Taking all the benefits of ethanol-blended fuel thus requires an adaptation of the engine management system. This paper intends to assess the effect of gasoline-ethanol blending from this point of view, then to describe a mean-value model of a fuel-flexible turbocharged PFI-SI engine, which will serve as a basis for the development of control algorithms. The focus will be in this paper on ethanol content estimation in the blend, supported by both simulation and experimental results.

While fuel efficiency has to be improved, future Diesel engine emission standards will further restrict vehicle emissions, particularly of nitrogen oxides. Increased in-cylinder filling is recognized as a key factor in addressing this issue, which calls for advanced design of air and exhaust gas recirculation circuits and high cooling capabilities. As one possible solution, this paper presents a 2-stage boosting breathing architecture, specially dedicated to improving the trade-off between emissions and fuel consumption instead of seeking to improve specific power on a large family vehicle equipped with a 1.6-liter Diesel engine. In order to do it, turbocharger matching was specifically optimized to minimize engine-out NOx emissions at part-load and consumption under common driving conditions. Engine speed and load were analyzed on the European driving cycle. The key operating points and associated upper boundary for NOx emission were identified.

A comprehensive experimental approach has been developed for a Fe-ZSM5 micro-porous catalyst, through a collaborative project between IFP, PSA Peugeot-Citroën and the French Environment and Energy Management Agency (ADEME). Tests have first been conducted on a synthetic gas bench and yielded estimated values for the amount of NH3 stored on a catalyst sample. These data have further been compared to those obtained from an engine test bench, in running conditions representative of the entire operating range of the engine. 15 operating points have been chosen, considering the air mass flow and the exhaust temperature, and tested with different NH3/NOx ratios. Steady-state as well as transient conditions have been studied, showing the influence of three main parameters on the reductant storage characteristics: exhaust temperature, NO2/NOx ratio, and air mass flow.

An unified model with a single set of kinetic parameters has been proposed for modeling laminar flame velocities of several alkanes using detailed kinetic mechanisms automatically generated by the EXGAS software. The validations were based on recent data of the literature. The studied compounds are methane, ethane, propane, n-butane, n-pentane, n-heptane, iso-octane, and two mixtures for natural gas and surrogate gasoline fuel. Investigated conditions are the following: unburned gases temperature was varied from 300 to 600 K, pressures from 0.5 to 25 bar, and equivalence ratios range from 0.4 to 2. For the overall studied compounds, the agreement between measured and predicted laminar burning velocities is quite good.