Les contextes climatique et énergétique mondiaux encouragent les pays de l'Union Européenne à améliorer leurs impacts environnementaux. Un des objectifs consiste à diminuer les émissions de CO2 en développant les énergies renouvelables. En France, la filière bois énergie représente la première source d'énergie renouvelable avec une production s'élevant à 10 MTep par an. Toutefois, il est indispensable de ne pas se limiter aux émissions de CO2 pour déterminer l'impact global d'une source d'énergie. En effet, la combustion de bois dans les appareils de chauffage domestique tels que les poêles, les inserts, les foyers ouverts, est à l'origine d'une part non négligeable de certains polluants atmosphériques tels que le CO, les COV, les HAP et les particules fines. L'objectif de ce projet est de réaliser un système efficace de dépollution capable de traiter l'ensemble des polluants à la sortie de ces appareils de chauffage. Des technologies sont déjà disponibles pour la dépollution des fumées issues de différentes sources de combustion, néanmoins nous devons intégrer les problématiques liées au fonctionnement de ces appareils ainsi que des critères de coût, de fonctionnalité et de développement durable définis dans un cahier des charges réalisé avec le partenaire industriel. Le travail réalisé nous à permis de concevoir et de tester un système complet capable de traiter tant les composants gazeux à l'aide d'un catalyseur à base de fer imprégné sur de la cérine, que les particules grâce à un lit filtrant régénéré par microondes. Le système décrit dans ce manuscrit présente une réduction faible des émissions, mais a permis de mettre en lumière les contraintes et les espoirs d'un futur système de traitement efficient. / The global energy and climate contexts encourage EU countries to improve their environmental impacts. One goal is to reduce CO2 emissions by developing the use of renewable energies. In France, wood is the first renewable energy source with an equivalent of 10 Mtoe produced each year. However, it is essential to study the global environment impact of on this energy source including CO2 emissions but also the different pollutants emitted. Indeed, the combustion of wood in small home heating units as stoves, open and closed fireplaces, is responsible for a significant part of typical air pollutants such as CO, VOCs, PAHs and fine particles. The objective of this project is to develop an effective system able to treat both pollutants emittedfrom those heaters. Few technologies are already available for smoke after treatment. However, we must incorporate in our study constraints related to the operation of these wood heating devices as well as criteria of cost, functionality and sustainability defined in the specifications set with the industrial partner of this project. The result of the work performed in this project was the conception of a complete prototype tested for emissions reduction. The system is composed of ceria impregnated iron catalyst for gaseous compounds oxidation and a microwave regenerated bed filter for particles elimination. The tests performed on the prototype showed weak emissions abatement. Nevertheless, this project highlighted constraints and hopes for a future efficient after treatment system.

The exhaust after treatment system is responsible for removing particulates and contaminants from the exhaust gases. The flow entering the SCR, a catalyst utilizing ammonia to reduce NOx emissions, was studied. The quality and distribution of flow entering the SCR plays an important role in the efficiency of the systems. A CFD study was completed initially investigating the impact on solution accuracy of different modeling approaches with respect to pressure drop and flow uniformity entering SCRs. Next, multi-species simulations were completed to analyze different modeling approaches impact on ammonia distribution and flow rates through SCRs. RANS, URANS, and DES simulations were compared in both stages. An in depth analysis of the current methodology utilized at Scania to investigate pressure drop and velocity uniformity index concluded that there is minimal benefit in changing the current methodology. DDES and URANS simulations yielded results containing less than 2% difference when compared with the current methodology. Expanding the investigation to include ammonia mixing yielded interesting disparities between simulation methods with respect to multispecies flow characteristics. This difference was attributed to disparities between the initial mixing of ammonia within the domain. The RANS and URANS simulations contained a much larger dispersion of ammonia, accredited to an increased false diffusion. DDES simulations are very computationally costly but by following time reducing processes, DDES simulations could be used early in the design and analysis phase of exhaust after treatment systems to analyze ammonia distribution and mixing.

NOx sensors have become salient components in the development of efficient exhaust after treatment system for heavy duty vehicles in the past few years. When the accumulated water inside the silencer splashes on to the NOx sensor, it can cause permanent cracks in the sensor. To protect the sensor from this mode of failure, a dew point strategy is developed at Scania. This is important to predict when it is safe to switch on the NOx sensor without causing any harm to it. But the strategy currently includes only the phase transfer phenomena and neglects the effect of the water blow out phenomena inside the silencer. To investigate the effect of water blow out, an experimental test method is designed and the experiments are conducted at different locations in the silencer. The results from the experiments shows that the effect of water blow out is certainly an important factor to develop a better dew point strategy model. For a selected location, the quantity of water remaining after blow out and the time taken for the blow out phase are collected as data from the experiments. A mathematical model for the water blow out phenomena is developed in MATLAB. The model estimates the maximum amount of water which could be present in all the subvolumes of the silencer considering the effect of water blow out. The model is verified with the experimental data for a Scania CAS1 silencer. Calibration guidelines for the developed blow out model are also documented in this report. / NOx sensorer har blivit viktiga komponenter i utvecklingen av ett effektivt avgassystem för tunga fordon under de senaste åren. När det ackumulerade vattnet i ljuddämparen stänker på NOx-sensorn kan det orsaka permanenta sprickor i sensorn. För att skydda sensorn från detta misslyckande utvecklas en daggpunktsstrategi på Scania. Detta är viktigt att förutsäga när det är säkert att slå på NOx-sensorn utan att skada den. Men strategin innehåller för närvarande endast fasöverföringsfenomenen och försummar effekten av att vatten blåser ut fenomen inuti ljuddämparen. För att undersöka effekten av utblåsning av vatten utformas en experimentell testmetod och experimenten utförs på olika platser i ljuddämparen. Resultaten från experimenten visar att effekten av vattenblåsning verkligen är en viktig faktor för att utveckla en bättre daggpunktsstrategimodell. För en vald plats samlas mängden vatten kvar efter utblåsning och den tid det tar för utblåsningsfasen som data från experimenten. En matematisk modell för fenomen för vattenblåsning utvecklas i MATLAB. Modellen uppskattar den maximala mängden vatten som kan finnas i ljuddämparens undervolymer med tanke på effekten av vatten som blåser ut. Modellen verifieras med experimentdata för en Scania CAS1 ljuddämpare. Kalibreringsriktlinjer för den utvecklade utblåsningsmodellen dokumenteras också i denna rapport.