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This paper touches on the mass transport phenomenon in the exhaust gas recirculation (EGR) of a gasoline engine air path. It presents the control-oriented model and control design of the burned gas ratio (BGR) transport phenomenon, witnessed in the intake path of an internal combustion engine (ICE), due to the redirection of burned gases to the intake path by the low-pressure EGR (LP-EGR). Based on a nonlinear AMESim® model of the engine, the BGR in the intake manifold is modeled as a state-space (SS) output time-delay model, or alternatively as an ODE-PDE coupled system, that take into account the time delay between the moment at which the combusted gases leave the exhaust manifold and that at which they are readmitted in the intake manifold. In addition to their mass transport delay, the BGRs in the intake path are also subject to state and input inequality constraints.

Reducing NOx tailpipe emissions is one of the major challenges when developing automotive Diesel engines which must simultaneously face stricter emission norms and reduce their fuel consumption/CO2 emission. In fact, the engine control system has to manage at the same time the multiple advanced combustion technologies such as high EGR rates, new injection strategies, complex after-treatment devices and sophisticated turbocharging systems implemented in recent diesel engines. In order to limit both the cost and duration of engine control system development, a virtual engine simulator has been developed in the last few years. The platform of this simulator is based on a 0D/1D approach, chosen for its low computational time. The existing simulation tools lead to satisfactory results concerning the combustion phase as well as the air supply system. In this context, the current paper describes the development of a new NOx emission model which is coupled with the combustion model.

An innovative alternative to overcome the load limits of the early injection highly premixed combustion concept consists of taking advantage of the intrinsic characteristics of two-stroke engines, since they can attain the full load torque of a four-stroke engine as the addition of two medium load cycles, where the implementation of this combustion concept could be promising. In this frame, the main objective of this investigation focuses on evaluating the potential of the early injection HPC concept using a conventional diesel fuel combined with a two-stroke poppet valves engine architecture for pollutant control, while keeping a competitive engine efficiency. On a first stage, the HPC concept was implemented at low engine load, where the concept is expected to provide the best results, by advancing the start of injection towards the compression stroke and it was confirmed how it is possible to reduce NOX and soot emissions, but increasing HC and CO emissions.

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.

Lean NOx trap (LNT) and Selective Catalytic Reduction catalysts (SCR) are two leading candidates for diesel NOx after-treatment. Each technology exhibits good properties to reduce efficiently diesel NOx emissions in order to match the forthcoming EURO 6 standards. NOx reduction in LNT is made through a two-step process. In normal (lean) mode, diesel engine exhausts NOx is stored into the NOx trap; then when necessary the engine runs rich during limited time to treat the stored NOx. This operating mode has the benefit of using onboard fuel as NOx reducer. But NOx trap solution is restrained by limited active temperature windows. On the other hand, NH₃-SCR catalysts operate in a wider range of temperature and do not contain precious metals. However, NH₃-SCR systems traditionally use urea-water solution as reducing agent, requiring thus additional infrastructure to supply the vehicles with enough reducer. These pros and cons are quite restrictive in classical LNT or NH₃-SCR architecture.

This paper presents an after-treatment architecture combining a close coupled NOx trap and an under floor NOx trap. Instead of simply increasing the volume of the catalyst, we propose to broaden the active temperature window by splitting the LNT along the exhaust line. In order to design this architecture, a complete 1D model of NOx trap has been developed. Validated with respect to experimental data, this model has been useful to define the two volumes of LNT, making significant savings on the test bench exploitation. However, one of the main difficulties to operate the proposed architecture is the NOx purge and sulfur poisoning management. In order to optimize the NOx and sulfur purge launches, we have developed a control strategy based on an embedded reduced LNT model. These strategies have been validated on different driving cycles, by the means of simulation and of vehicle tests using rapid prototyping tools.

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.

The Particulate Measurement Programme (PMP) works on the identification of a method to replace or complete the existing particle mass (PM) measurement method. The French PMP subgroup, composed by IFP, PSA Peugeot-Citroën, Renault and UTAC, proposes an improved gravimetric method for the measurement of emitted particles, and conducted an inter-laboratory test to evaluate its performances. The technical programme is based on tests carried out on a Euro3 Diesel passenger car (PC), tested on the New European Driving Cycle (NEDC). To achieve low particulate matter (PM) emissions, the EGR is disconnected and a paraffinic fuel is used. The regulated pollutants are also measured. It is shown that the multiple filter weighing and a 0.1 μg balance instead of a 1 μg one are not necessary, as the first weighing and the 1 μg balance performances are satisfactory for type-approval purposes.

An extensive research program involving the French passenger car and heavy-duty (HD) vehicles manufacturers, sponsored by ADEME and realized by IFP, aimed to characterize in terms of size and composition the particulate emitted by the different engine technologies currently or soon available. The impact of engine settings and fuel composition was also studied. Numerous information was collected in this HD study revealing that fuel composition and particularly non-conventional fuels and engine settings strongly impact the particulate concentration and size distribution. Nucleation is likely to occur when there is less adsorption matter, for instance when post-injection is used or EGR is removed. Particulate composition, particularly PAH and sulfates content, is weakly bound to the size. Mineral elements distribution depends on their origin, lubrication oil or engine wear.

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.

No efficient catalyst presently exists for deNOx in lean burn conditions. Furthermore, actual catalysts generally deactivate during reaction. A cylindrical DBD non-thermal plasma reactor was coupled with a stable three-function catalyst in order to verify the nature of the effect of the plasma on the catalytic process. A mixture of NO/O2/C3H6 in N2 was used as a lean model exhaust. The plasma was found to perform two of the three functions: NO oxidation to NO2 and propene activation through the partial oxidation of the hydrocarbon to aldehyde or alcohol. A complete catalyst containing the first two previous functions and the associative chemisorption of NO (third function) was used, as well as a simplified catalyst containing only the third function. Results suggest an advantageous plasma-catalyst coupling effect on NOx remediation in accordance with the proposed catalytic model.

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.

Laboratory and vehicle tests were carried out to investigate behaviour and potentiality of NOx-trap catalytic system in Diesel conditions. Three main aspects were studied. The first one deals with the NOx storage capacity of adsorber under laboratory and vehicle conditions, especially regarding the influence of driving conditions. The second one focuses on the regenerability of different materials. At length, special attention is devoted to the sulphur poisoning rate. A representative laboratory test method was built up, to evaluate NOx storage capacity under Diesel conditions. It is shown that NOx adsorption occurs from 100 to 400°C. Low temperature activity (100 to 250°C) is conditioned by low NOx flow emission, mainly due to the use of high EGR rate. Higher temperatures lead to an increase in the intrinsic NOx Storage capacity of the material, but are also accompanied by high NOx concentration and space velocity.

This presented paper deals with NOx trap sulphur poisoning and its regeneration. Sulphur poisoning has been studied with different SO2 gas concentrations under laboratory and engine test bench conditions. The sulphur poisoning studies have shown that the different NOx-traps available in the market have different behaviours toward SO2 poisoning and are all very sensitive to it. The results outline a non linear relationship of the NOx trap sulphur poisoning as a function of SO2 concentration. For instance, engine bench tests show that with a 50 and a 110ppm sulphur containing gasoline, a decrease of 50% in the NOx-trap storage capacity is respectively observed after 20 and 15 hours. With a gasoline containing 20ppm of sulphur, the same deactivation level is observed after 90 hours.

Laboratory and engine tests were carried out to describe the sulphur effect on the NOx adsorbers catalysts efficiency for gasoline lean burn engines. Two main aspects were studied. The first one deals with the NOx storage efficiency of the adsorber under laboratory conditions, especially regarding the SO2 gas phase concentration. The rate of sulfur storing is greatly affected by the SO2 gas concentration. While 6.5 hours are required to get from 70 % NOx reduction to only 35 % when the gas mixture contains 10 ppm SO2, it takes 20 hours with 5 ppm SO2 and more than 60 hours with the 2 ppm SO2 condition. The relationship between the loss in NOx trap performance and SO2 concentration appears to have an exponential shape. The same amount of sulphur (0.8 % mass) is deposited onto the catalyst within 10 hours with the feed gas containing 10 ppm of SO2 and within 50 hours with 2 ppm SO2. Nevertheless, It was shown that the loss in NOx-Trap efficiency is not the same in these two cases.

The emissions performance of catalytic converters under different conditions of flow distribution was investigated. Computational Fluid Dynamics methods were utilised to model the maldistribution effects of different inlet cones. The effects of maldistribution on ageing, light-off and conversion were investigated using steady state tests on an engine bench. Emission testing was also conducted on a vehicle throughout ECE and EUDC test cycles. Maldistribution was found to have a significant effect on the efficiency of the catalyst during the early stages of the ECE cycle for both fresh and aged catalysts. The effects were less significant over later stages of the ECE cycle and throughout the EUDC except NOx where maldistribution did have an effect on the conversion at higher flow rates during the later stages of the test.

Studies using a bi-fuelled (autogas/gasoline) Renault Laguna vehicle meeting °the 1996 European exhaust emission legislation has demonstrated that over the European test cycle at 25°C the LPG operated vehicle provides substantial benefits of reduced emissions compared to unleaded reference gasoline. At lower test temperatures (i.e. 5°C) even larger reduction in emissions have been observed. Lower CO (up to 95% at -5°C and 65% at 25°C), HC (90% at -5°C and 40% at 25°C) emissions and lower ozone HC reactivity have been observed and could all offer significant environmental air-quality benefits for LPG. Various autogas mixtures have been tested including 70/30, 30/70 and 49/30/21 (% mass propane / butane / propene). Results show that NOx emissions for this vehicle appear dependent on autogas composition. The two gas mixtures containing only 30% butane gave about 50% more NOx at +25°C than the 70% butane autogas mixture.