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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.

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.

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.

In order to asses the durability of DPF, a study has been performed in order to study the evolution of several taxis (Peugeot 607) and the performance of this after-treatment systems over 80,000 km mileage in hard urban driving conditions, which corresponds to the recommended mileage before the first DPF maintenance (this periodicity is applied on the first generation of DPF technology launched in 2000). More specifically, the following evaluations are being performed at regular intervals (around 20 000 km): Regulated gaseous pollutant emissions on NEDC cycle (New European Driving Cycle) Particulate emissions, by mass measurement on NEDC but also by particle number and size measurement with SMPS (Scanning Mobility Particle Sizer) technique on NEDC and on unconventional steady-state running points.

The use of Diesel engines has strongly increased during the last years and now represents 30% of the sales in Europe and up to 50% of the number of cars in circulation for some countries. This success is linked not only to the economical aspect of the use of such vehicles, but also to the recent technological improvements of these engines. The new technical solutions (high pressure direct injection, turbocharging…) have indeed allowed the increase of these engine performances while decreasing their fuel consumption, pollutant emissions and noise level. From an environmental point of view, Diesel engines are nevertheless penalized by their particulate and NOx emissions. The study and the treatment of the particulate, highly criticized for their potential impact on health, are the subject of numerous works of characterization and developments. PSA Peugeot-Citroën has recently launched its particulate filter technology on several types of vehicles.

This paper presents an overview of the results on light duty vehicles collected in the “PARTICULATES” project which aimed at the characterization of exhaust particle emissions from road vehicles. A novel measurement protocol, developed to promote the production of nucleation mode particles over transient cycles, has been successfully employed in several labs to evaluate a wide range of particulate properties with a range of light duty vehicles and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The vehicle sample consisted of 22 cars, including conventional diesels, particle filter equipped diesels, port fuel injected and direct injection spark ignition cars. Four diesel and three gasoline fuels were used, mainly differentiated with respect to their sulfur content which was ranging from 300 to below 10 mg/kg.

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.

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.

To ensure overall optimisation of heavy duty engine performance (with the respect of NOx&PM future European and US emissions standards), the use of a high efficiency NOx after-treatment system such as a NOx trap appears to be necessary. But running in rich conditions, even for a short time, leads to a large increase of particulate emissions so that a particulate filter is required. A first investigation with a NOx-trap only has been carried out to evaluate and optimise the storage, destorage and reduction phases from the NOx conversion efficiency and fuel penalty trade-off. The equivalence ratio level, the fuel penalty and the temperature level of the NOx-trap have been shown as a key parameter. Respective DPF and LNA locations have been studied. The configuration with the NOx-trap upstream provides the best NOx / fuel penalty trade-off since it allows NOx slip reduction and does not disturb the rich pulses.

Electrical Low Pressure Impactor (ELPI) is often employed to measure the particle number and size distribution of internal combustion engines exhaust gas. If appropriate values of particle density are available, the particle mass can be estimated by this method. Exhaust particles of three Euro3 passenger cars (one gasoline operating under stoichiometric conditions, one Diesel and one Diesel equipped with Diesel Particulate Filter) are measured using the current European regulations (gravimetric method on the are New European Driving Cycle) and estimated by ELPI particle number and size distribution. Different values for particle density are used to estimate the particle mass using all ELPI stages or only some of them. The results show that the particle mass estimated by ELPI is well correlated with the mass determined by filters for PM emissions higher than 0.025 g/km. This correlation is not very good at lower emissions.

Facing the stringent constraints on fuel consumption and pollutant emissions, the automotive manufacturers have to produce vehicles with an increasing number of complex systems working together. Numerical simulation for the system design, set-up and control strategies, helps to reduce the development cycle and the global cost. Existing simulation tools usually do not address, with a high level of details, the various physical domains involved in a vehicle powertrain. To overcome this challenge, IFP and IMAGINE, settled a partnership to develop detailed simulation tools dedicated to performance, consumption and emissions for conventional and hybrid vehicles [1]. These tools are integrated in a multi-domain simulation platform (AMESim®) where several levels of detail can be easily reached for each sub-element.

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.