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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.

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 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 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.

In the context of modern engine control, one important variable is the individual Air Fuel Ratio (AFR) which is a good representation of the produced torque. It results from various inputs such as injected quantities, boost pressure, and the exhaust gas recirculation (EGR) rate. Further, for forthcoming HCCI engines and regeneration filters (Particulate filters, DeNOx), even slight AFR unbalance between the cylinders can have dramatic consequences and induce important noise, possible stall and higher emissions. Classically, in Spark Ignition engine, overall AFR is directly controlled with the injection system. In this approach, all cylinders share the same closed-loop input signal based on the single λ-sensor (normalized Fuel-Air Ratio measurement, it can be rewritten with AFR as they have the same injection set-point.

Lean-burn combustion in SI engines can significantly reduce fuel consumption but NOx reduction becomes challenging because classic three-way catalyst (TWC) is no more efficient. Urea-SCR is then an interesting alternative solution because of its high NOx conversion efficiency without any additional fuel consumption. The coupling between two SI lean-burn engines (stratified and homogeneous combustion) and a urea-SCR catalyst was simulated on the NEDC cycle. Simulation results showed that the SCR efficiency would comply with the limits required by future Euro 5/6 regulations. Associated urea solution consumptions were estimated thanks to a simplified model. Finally, a comparison with a Diesel application was also made. It showed that the required amount of reducing agent remained significantly higher for SI lean-burn engines than for Diesel engine.

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.

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.

The purpose of the European « SPACE LIGHT » (Whole SPACE combustion for LIGHT duty diesel vehicles) 3-year project launched in 2001 is to research and develop an innovative Homogeneous internal mixture Charged Compression Ignition (HCCI) for passenger cars diesel engine where the combustion process can take place simultaneously in the whole SPACE of the combustion chamber while providing almost no NOx and particulates emissions. This paper presents the whole project with the main R&D tasks necessary to comply with the industrial and technical objectives of the project. The research approach adopted is briefly described. It is then followed by a detailed description of the most recent progress achieved during the tasks recently undertaken. The methodology adopted starts from the research study of the in-cylinder combustion specifications necessary to achieve HCCI combustion from experimental single cylinder engines testing in premixed charged conditions.

Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have explored development issues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by the French Ministry of Industry, IFP, PSA-Peugeot-Citroën, Renault and RVI (Renault Véhicules Industriels), has been built to study this point. It is based on a three years program with different steps focused on new engine technologies which will be available in the next 20 years in order to answer to more and more severe pollutant and CO2 emission regulations. This program is divided into three main parts: the first one for Diesel car engines, the second for Diesel truck engines and the third for spark ignition engines.

Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have been exploring development avenues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by FSH (Fonds de Soutien aux Hydrocarbures), IFP, PSA-Peugeot-Citroën, Renault and Renault VI (Véhicules Industriels), has been built to study this point. It is a four years programme with different steps which will focus on new engine technologies: some of them are going to be marketed very soon (gasoline direct injection car engine, and diesel common rail injection car and truck engines) to anticipate the Euro 3 (2000) and the Euro 4 (2005) emissions specifications. The original work reported here is part of this research.

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.

In the context of low consumption and low emissions engines development, combustion processes modeling is a challenging subject as the requirements for accurately controlled pollutant emissions are becoming more stringent. From a scientific point of view, it is a major source of in-depth investigations as the chemical processes involved are strongly coupled to the flow characteristics. Among the various approaches developed recently to account for these processes in realistic configurations, tabulated techniques appear to be a promising way. They induce a good compromise between the accuracy of detailed chemistry and the computational time necessary to calculate complex configurations. Tabulation approaches were firstly developed to address the modeling of species concentrations in stationary combustors. They consist basically of pre-computed chemical kinetics using detailed mechanisms.

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.

Planar laser-induced fluorescence (LIF) imaging of formaldehyde (CH2O) and OH has been performed to investigate the homogeneous charge, compression ignition (HCCI) combustion process inside the piston bowl of an optically-accessible, direct injection Diesel-fueled HCCI engine. In particular, the effects of charge dilution and the adoption of single and split injection strategies on the two-stage HCCI combustion have been studied. Results obtained show that the level of exhaust gas recirculation (EGR) significantly affects the pre-combustion or so called cool flame phase during which formaldehyde is detected. The cool flame phasing as indicated by the formation of this intermediate species is unaffected by the EGR level however, auto-ignition timing which marks the start of main combustion is inevitably advanced following a reduction in EGR and this ultimately determines the formaldehyde lifetime and consequently the degree of homogeneity attained.

The purpose of the 4-SPACE (4-Stroke Powered gasoline Auto-ignition Controlled combustion Engine) industrial research project is to research and develop an innovative controlled auto-ignition combustion process for lean burn automotive gasoline 4-stroke engines application. The engine concepts to be developed could have the potential to replace the existing stoichiometric / 3-way catalyst automotive spark ignition 4-stroke engines by offering the potential to meet the most stringent EURO 4 emissions limits in the year 2005 without requiring DeNOx catalyst technology. A reduction of fuel consumption and therefore of corresponding CO2 emissions of 15 to 20% in average urban conditions of use, is expected for the « 4-SPACE » lean burn 4-stroke engine with additional reduction of CO emissions.

NOx adsorbers are very sensitive to sulfur poisoning and future fuel standards are unlikely to be sufficient to prevent the system from requiring periodic desulfation procedures. The purpose of this paper is to present the effects of low fuel sulfur content such as 50 ppm and 10 ppm on the NOx adsorber efficiency for a diesel application. Through this study, the influence of the substrate cell geometry has also been assessed. The use of a 10 ppm sulfur fuel is not enough to maintain, at a high level, the NOx adsorber performance during a 40,000 km aging test. The desulfation criterion (efficiency loss of 30%) is reached after the first 16,000 km. However, the desulfation operation is not enough to recover the initial catalyst performance and the poisoning velocity increases as the catalyst ages. The hexagonal cell substrate catalyst is less sensitive to sulfur poisoning than a square cell substrate catalyst so that its desulfation frequency is much lower.

Latest emissions standards impose very low NOx and particle emissions that have led to new Diesel combustion operating conditions, such as low temperature combustion (LTC). The principle of LTC is based on enhancing air fuel mixing and reducing combustion temperature, reducing raw nitrogen oxides (NOx) and particle emissions. However, new difficulties have arisen. LTC is typically achieved through high dilution rates and low CR, resulting in increased auto-ignition delay that produces significant noise and deteriorates the combustion phasing. At the same time, lower combustion temperature and reduced oxygen concentration increases hydrocarbon (HC) and carbon oxide (CO) emissions, which can be problematic at low load. Therefore, if LTC is a promising solution to meet future emission regulations, it imposes a new emissions, fuel consumption and noise trade-off. For this, the injection strategy is the most direct mean of controlling the heat release profile and fuel air mixture.

Three dimensional CFD tools are commonly used to simulate spray injection and combustion in DI Diesel engines. However typical computations are strongly mesh dependent. By now it is not possible to enhance grid resolution since it would violate the underlying assumptions for the Lagrangian liquid phase description. Besides, a full Eulerian approach with an adapted mesh is not practical at the moment mainly because of prohibitive computer requirements. Based on the Lagrangian-Eulerian approach, new approaches have been developed: the Coupled Lagrangian-Eulerian (CLE) model for the two-way coupling between the spray and the air flow and a new combustion model (CFM3Z) which allows a description of the fuel-oxidizer sub-grid mixing. The previously introduced CLE model consists in retaining vapor and momentum along parcel trajectories as long as the mesh is insufficient to resolve the steep gradients created by the spray.