Due to strong motivation to reduce costs and increase performances of stationary diesel after-treatment systems, computational modeling has become a necessary step in system design and improvement. A unique mixing duct typified by significant changes in scale and strong flow curvature was evaluated for its potential to improve flow distribution across the SCR catalyst inlet face. The flow dynamics were investigated with a steady three-dimensional turbulence model and detailed chemistry was studied separately using a one-dimensional channel reactive flow model. Aqueous urea injection was modeled using Discrete Phase Modeling. The mixing duct performance relative to reactor dimensions and engine loads is discussed. The Impact of injector positions was studied using massless particle tracking. A total of three geometries were evaluated using a Uniformity Index of the ammonia-to-NOx feed ratio. It was found that a higher mixing duct height to inlet diameter ratio yielded better mixing.

Due to strong motivation to reduce costs and increase performances of stationary diesel after-treatment systems, computational modeling has become a necessary step in system design and improvement. A unique mixing duct typified by significant changes in scale and strong flow curvature was evaluated for its potential to improve flow distribution across the SCR catalyst inlet face. The flow dynamics were investigated with a steady three-dimensional turbulence model and detailed chemistry was studied separately using a one-dimensional channel reactive flow model. Aqueous urea injection was modeled using Discrete Phase Modeling. The mixing duct performance relative to reactor dimensions and engine loads is discussed. The Impact of injector positions was studied using massless particle tracking. A total of three geometries were evaluated using a Uniformity Index of the ammonia-to-NOx feed ratio. It was found that a higher mixing duct height to inlet diameter ratio yielded better mixing.

Diesel engines are widely used in automotive sector due to their high fuel efficiency, distinguished durability and great reliability. However, NOx and particulate matters (PM) are main concerns of the Diesel engines due to their lean burn conditions. To reduce these emissions, Diesel engines are usually coupled with state-of-the-art Diesel aftertreatment systems including a Diesel Oxidation Catalyst (DOC), a Diesel Particulate Filter (DPF), and a Selective Catalytic Reduction system (SCR). With increasingly stringent regulations, the estimation and control strategies of Diesel after-treatment systems for NOx and PM reduction are becoming more and more critical and challenging, especially under transient conditions with unknown system dynamics including disturbances and model uncertainties. To address these problems, this thesis focuses on advanced strategies based on disturbance estimation and compensation for improving the performance of Diesel after-treatment systems. Urea injection and ammonia storage ratio are critical for the SCR system to achieve high NOx reduction efficiency and low NH3 slip. Nevertheless, unknown system dynamics including input (urea injection) disturbances and model uncertainties of SCR system make it challenging to achieve high NOx reduction efficiency and low NH3 slip. To deal with these obstacles, Paper 1, Paper 2 and Paper 3 (Chapter 2, 3, and 4 respectively) proposed active disturbance estimation and compensation methods for enhancing the SCR performance. Paper 1 (Chapter 2) introduces two different methods to accurately detect urea injection and correct for urea dosing control. Paper 2 (Chapter 3) depicts a robust Nonlinear Disturbance Observer (robust NDO) to effectively estimate the ammonia storage ratio in a cost-effective way. Paper 3 (Chapter 4) presents a compound control strategies based on active disturbance rejection control (ADRC) to precisely keep NH3 slip low and achieve high NOx reduction efficiency. DOC thermal management is critical to effectively burn the soot during DPF regeneration (PM reduction). But unknown system dynamics including DOC inlet emissions and model uncertainties make it difficult for DOC mean temperature estimation and DOC outlet temperature control during DPF regeneration. To deal with these challenges, Paper 4 and Paper 5 (Chapter 5 and 6 respectively) developed active disturbance estimation and compensation strategies for improving DOC thermal management during DPF regeneration. Paper 4 (Chapter 5) introduces a robust filter based on Smooth Variable Structure Filter (SVSF) with augmented disturbance states to estimate the mean temperature of DOC. Paper 5 (Chapter 6) presents a composite controller combining a feedforward controller and an modified Active Disturbance Rejection Controller (mADRC) with time delay compensation for the DOC outlet temperature control. The proposed methods in the 5 papers are either validated by the calibrated GT-power model or experiments with Diesel after-treatment systems. / Thesis / Doctor of Philosophy (PhD)

The NOx health and environmental problems make necessary to reduce this gaseous emission from different sources. Furthermore, its increase in the last years and the difficulties to remove it with after-treatment systems already in the market make more urgent the development of new techniques. The purpose of this investigation is to study the low temperature catalytic oxidation of NO to NO2 and its adsorption over a renewable activated carbon (AC) from coconut shell. The present research presents the results of experimental work carried out using a laboratory scale reactor to investigate the low temperature catalytic oxidation of NO. Activated carbon was housed in the reactor and tests were carried out with different reactor sizes, different activated carbon forms and shapes, different gas mixtures at different temperatures and different levels of humidity to simulate dry and wet particulate-free diesel engine exhaust gas. The effects of addition of ozone in the gas on the NO oxidation were also explored. Gas analysis upstream and downstream of the catalytic reactor was carried out in all cases during the charge and regeneration of the AC. An extensive literature review in conjunction with measurement of some properties of the activated carbon helped to understand better its characteristics and behaviour. The results of this study indicate that in the case of dry gas, the activated carbon initially acts as an adsorber and only after operation of several hours, the NO oxidation that takes place in the reactor results in increased NO2 levels in the product gas. The NO conversion is affected by the activated carbon form and reaction conditions including temperature, humidity, oxygen, NO, CO2 content in the inlet gas, temperature, space velocity, linear gas velocity, residence time, reactor shape, AC pretreatment and lifespan. Water vapour has a detrimental effect on the conversion of NO to NO2 before the AC reaches the steady-state conditions. On the other hand, ozone is effective in converting NO to NO2 at room temperature. This research has developed some findings not studied or reported by other researches before and confirms and/or complements results reported in the literature review by other groups, which will benefit the development of a renewable after-treatment system of NOx emissions.

Tougher environmental legislations are a driving force for development of aftertreatment technologies for truck and car exhaust gases. In particular, the emission requirements are high on nitrogen oxides (NOx) and particulate matter. Focus of this thesis work is to develop a component in the exhaust system, a NOx level reduction system. The currently used technology with urea evaporator has problem with formation of urea crystals due to delayed urea evaporation. Crystalline urea causes reduced exhaust flow and thus build up a pressure in the system that has negative impact on the performance of the engine. Feasibility study was done to understand function, advantage and disadvantages of current design and the need for a new design. The main task of this project was to investigate and propose a new design of the helix-rotary evaporator and to present it in the form of parametric model. Material selection needed for urea injection arrangement, 3D printed model for visualization of the concept and integration of the model to next generation aftertreatment system (NGA) are examples of sub-tasks that was performed to reach the main objective. Several generations of selected concept were developed in 3D design which later was 3D printed to visualize the ideas. The parametric 3D model was designed so that it later serves as input model for a later phase in the development project, where computational fluid dynamics is utilized. Parametric modelling is used to provide wide range of possibility to generate different models for simulation and reduce pre-simulation works. Selected concept parametric model has six different parameters that can be analysed. Material selection carried out to injection manifold thought CES Edupack and consultancy of material engineers. Three different austenitic stainless steels were recommended.

No description available.

Yes / This paper provides a critical review and discussion of major challenges with automotive aftertreatment systems from the viewpoint of the reliability of complex systems. The aim of this review is to systematically explore research efforts towards the three key issues affecting the reliability of aftertreatment systems: physical problems, control problems and fault diagnostics issues. The review covers important developments in technologies for control of the system, various methods proposed to tackle NOx sensor cross-sensitivity as well as fault detection and diagnostics methods, utilized on SCR, LNT and DPF systems. This paper discusses future challenges and research direction towards assured dependability of complex cyber-physical systems. / InPowerCare Project - JLR (Jaguar Land Rover)

<div>Strict emissions regulations are mandated by the environmental protection agency (EPA) to reduce emission of greenhouse gases and criteria air pollutants from diesel engines, which are widely used in commercial vehicles. A ten-fold reduction in allowable heavy-duty on-road oxides of nitrogen (NOx) emissions are projected to be enforced by 2024. The need to meet these emission regulations, along with consumer demand for better fuel efficiency, has resulted in greater effort towards cleaner and more efficient diesel engines.</div><div><br></div><div><div>Diesel engine aftertreatment systems are effective in reducing engine-out emissions, but only at catalyst bed temperatures above 200°C. The aftertreatment system needs to be quickly warmed up to its efficient operating temperatures, and maintain elevated temperatures in a fuel-efficient manner, which is a challenge using conventional engine strategies. This study details the use of advanced gas-exchange management, via variable valve actuation, to improve both `warm-up' and `stay-warm' aftertreatment thermal management.</div></div><div><br></div><div><div>Fast initial warm-up of the aftertreatment system, following a cold engine start, is enabled by strategies such as early exhaust valve opening (EEVO), internal exhaust gas recirculation (iEGR) and late intake valve closure (LIVC). Steady state and drive cycle results of a combination of EEVO and iEGR at idle operation, and a combination of EEVO and LIVC at off-idle conditions below 7.6 bar BMEP, are presented. It is demonstrated that ~ 150°C higher steady state temperatures are achieved at idle, and up to 10.1% reduction in predicted tailpipe-out NOx is achieved at 3.1% fuel penalty over the heavy-duty federal test procedure (HD-FTP) drive cycle.</div></div><div><br></div><div><div>Fuel-efficient `stay-warm' aftertreatment thermal management is demonstrated to be effectively achieved via cylinder deactivation (CDA), to reduce fuel consumption, elevate engine-outlet temperatures and reduce exhaust flow rates at idle and low load engine operation. Implementation of CDA at idle and low loads below 3 bar BMEP is demonstrated to achieve fuel savings of 4% over the HD-FTP drive cycle, while maintaining similar levels of tailpipe-out NOx emissions. It is demonstrated that lower air flow during CDA at, and near, idle operation does not compromise the transient torque/power capabilities of the engine- a key nding in enabling the practical implementation of CDA in diesel engines.</div></div><div><br></div><div><div>Some of the practical challenges expected with CDA are studied in detail, and alternate strategies addressing the challenges are introduced. Dynamic cylinder activation (DCA) is introduced as a means to enable greater control over the torsional vibration characteristics of the engine, via selection of appropriate ring patterns, while maintaining similar performance and emissions as xed CDA. A generic strategy to use CDA and an appropriate DCA strategy to operate away from driveline resonant frequencies at different engine speeds is described. Ventilated cylinder cutout (VCC) is introduced as a means to potentially mitigate oil accumulation concerns during CDA, by ventilating the non-ring cylinders to the intake/exhaust manifold(s) by opening the intake/exhaust valves during all the four strokes of the engine cycle. The fuel efficiency and thermal management performance of VCC is assessed for different ventilation congurations and compared with CDA and baseline engine operation.</div></div>

Producing more fuel efficient vehicles as well as lowering emissions are of high importance among heavy duty vehicle manufactures. One functionality of lowering fuel consumption is to use a so called \emph{look-ahead control strategy}, which uses the GPS and topography data to determine the optimal velocity profile in the future. When driving downhill in slopes, no fuel is supplied to the engine which lowers the temperature in the aftertreatment system. This results in a reduced emission reduction capability of the aftertreatment system. This master thesis investigates the possibilities of using preheating look-ahead control actions to heat the aftertreatment system before entering a downhill slope, with the purpose of lowering fuel consumption and $NO_x$ emissions. A temperature model of a heavy duty aftertreatment system is produced, which is used to analyse the fuel consumption and $NO_x$ reduction performance of a Scania truck. A Dynamic Programming algorithm is also developed with the purpose of defining an optimal control trajectory for minimizing the fuel consumption and released $NO_x$ emissions. It is concluded that the Dynamic Programming optimization initiates preheating control actions with results of fuel consumption reduction as well as $NO_x$ emissions reductions. The best case for reducing the maximum amount of fuel consumption results in 0.14\% lower fuel consumption and 5.2\% lower $NO_x$ emissions.

[ES] A pesar de la tendencia actual hacia la electrificación del transporte por carretera, los motores de combustión interna alternativos han sido esenciales en este sector y se espera que sigan siendo una tecnología con notable presencia durante las próximas décadas. Los vehículos de pasajeros actuales basados en motores de combustión interna son más ecológicos que los utilizados hace años, aunque todavía queda trabajo por hacer. Los sistemas de postratamiento están enfocados a minimizar tanto como sea posible el impacto de los motores de combustión interna en términos de emisiones contaminantes. En el caso de los motores de encendido provocado, los catalizadores de tres vías representan la tecnología más extendida en las últimas décadas, debido a su compacidad y buena relación precio-prestaciones. Estos convertidores son capaces de oxidar hidrocarburos y monóxido de carbono al mismo tiempo que reducen los óxidos de nitrógeno. No obstante, para lograr su mejor eficiencia, el dosado debe controlarse con precisión en torno a condiciones estequiométricas. En este sentido, los sistemas electrónicos de gestión del motor son esenciales para aprovechar las características de estos convertidores. En particular, las estrategias de control y diagnóstico desempeñan un papel clave para lograr una reducción efectiva de las emisiones en el amplio rango de condiciones de operación que se dan en condiciones de funcionamiento reales. El desarrollo de estas estrategias es fundamental, especialmente teniendo en cuenta el bajo nivel de emisiones permitido por las normativas de emisiones actuales y la tendencia hacia cero emisiones. El propósito de esta tesis doctoral es analizar el comportamiento del sistema de postratamiento en condiciones específicas pero a la vez muy comunes en conducción real, y desarrollar estrategias que proporcionen una reducción adicional de las emisiones en sistemas basados en catalizador de tres vías. Con la popularización de pequeños motores turboalimentados de encendido provocado, ha aumentado el uso de estrategias de barrido de la cámara de combustión para mitigar los típicos problemas de falta de par a bajo régimen. Esta tesis analiza el impacto de los pulsos de cortocircuito en el catalizador y en las sondas ¿. El proceso de cortocircuito de aire fresco al escape tiene un impacto importante en la dinámica intraciclo de la composición de los gases de escape. En particular, los pulsos de monóxido de carbono e hidrógeno seguidos por los pulsos de aire fresco perturban el normal funcionamiento del sensor de oxígeno. Por lo tanto, se ha propuesto un nuevo método para estimar la tasa de cortocircuito abordo. Este método permite corregir la desviación sufrida por el sensor y, por lo tanto, ayuda a reducir la penalización en emisiones de este tipo de estrategias. Para mejorar la eficiencia del catalizador en condiciones transitorias, no solo se requiere un control preciso del dosado aguas arriba del catalizador, sino que también resulta imprescindible considerar el comportamiento dinámico del convertidor en sí mismo. Por ejemplo, el almacenamiento de oxígeno es un buen indicador del estado del catalizador, pero no se puede medir directamente mediante sensores. Por lo tanto, el desarrollo de modelos es clave en las estrategias de control actuales, para poder estimar abordo diferentes parámetros relacionados con el estado del catalizador. Varios modelos de catalizador se han desarrollado en esta tesis doctoral para lidiar con diferentes cuestiones, desde la predicción de los efectos de la condensación de agua en la evolución de la temperatura del catalizador justo después del arranque en frío, a la cuantificación del nivel de envejecimiento, pasando por el control óptimo de purga del catalizador. / [CAT] Malgrat la tendència actual cap a l'electrificació del transport per carretera, els motors de combustió interna alternatius han sigut essencials en aquest sector i s'espera que continuen sent una tecnologia amb notable presència durant les pròximes dècades. Els vehicles de passatgers actuals basats en motors de combustió interna són més ecològics que els utilitzats fa anys, encara que hi ha treball per fer. Els sistemes de post-tractament estan enfocats a minimitzar tant com siga possible l'impacte dels motors de combustió interna en termes d'emissions contaminants. En el cas dels motors d'encés provocat, els catalitzadors de tres vies representen la tecnologia més estesa en les últimes dècades, pel fet que són compactes i posseeixen bona relació preu-prestacions. Aquests convertidors són capaços d'oxidar hidrocarburs i monòxid de carboni al mateix temps que redueixen els òxids de nitrogen. No obstant això, per a aconseguir la seua millor eficiència, el dosatge ha de controlar-se amb precisió entorn de condicions estequiomètriques. En aquest sentit, els sistemes electrònics de gestió del motor són essencials per a aprofitar les característiques d'aquests convertidors. En particular, les estratègies de control i diagnòstic exerceixen un paper clau per aconseguir una reducció efectiva de les emissions en l'ampli rang de condicions d'operació que es donen en condicions de funcionament reals. El desenvolupament d'aquestes estratègies és fonamental, especialment tenint en compte el baix nivell d'emissions permès per les normatives actuals i la tendència cap a zero emissions. El propòsit d'aquesta tesi doctoral és analitzar el comportament del sistema de post-tractament en condicions específiques però alhora molt comunes en conducció real, i desenvolupar estratègies que proporcionen una reducció addicional de les emissions en sistemes basats en catalitzador de tres vies. Amb la popularització de xicotets motors amb sobrealimentació d'encés provocat, ha augmentat l'ús d'estratègies de curtcircuit per a mitigar els típics problemes de falta de parell a baix règim. Aquesta tesi analitza l'impacte dels polsos de curtcircuit en el catalitzador i en les sondes ¿. El procés de curtcircuit d'aire fresc té un impacte important en la dinàmica intra-cicle de la composició dels gasos. En particular, els polsos de monòxid de carboni i hidrogen seguits pels polsos d'aire fresc pertorben el normal funcionament del sensor d'oxigen. Per tant, s'ha proposat un nou mètode per a estimar la taxa de curtcircuit del motor. Aquest mètode permet corregir la desviació patida pel sensor i, per tant, ajuda a reduir la penalització en emissions d'aquest tipus d'estratègies. Per a millorar l'eficiència del catalitzador en condicions transitòries, no solament es requereix un control precís del dosatge aigües amunt del catalitzador, sinó que també resulta imprescindible considerar el comportament dinàmic del convertidor en si mateix. Per exemple, l'emmagatzematge d'oxigen és un bon indicador de l'estat del catalitzador, però no es pot mesurar directament mitjançant sensors. Per tant, el desenvolupament de models és clau en les estratègies de control actuals, per poder estimar els diferents paràmetres relacionats amb l'estat del catalitzador. Diversos models de catalitzador s'han desenvolupat en aquesta tesi doctoral per a tractar diferents qüestions, des de la predicció dels efectes de la condensació d'aigua en l'evolució de la temperatura del catalitzador just després de l'arrencada en fred, a la quantificació del nivell d'envelliment, passant pel control òptim de porga del catalitzador. / [EN] In spite of the current tendency towards the electrification of the road transport, internal combustion engines have been essential in this sector and it is expected to continue being a technology with a noticeable presence during next decades. Current passenger cars based on internal combustion engines are greener than those used years ago, although it is still a developing process. Aftertreatment systems are aimed to minimize as much a possible the impact of internal combustion engines in terms of pollutant emissions. In case of spark-ignited engines, three-way catalytic converters represent the most widespread technology during last decades, due to their compactness and cost-performance. These converters are capable to oxidise hydrocarbons and carbon monoxide while simultaneously reducing nitrogen oxide. Nonetheless, to achieve their best efficiency, the air-to-fuel ratio must be accurately controlled close to stoichiometric conditions. In this sense, electronic engine management systems are essential to take advantage of the features of these converters. In particular, control and diagnosis strategies play a key role to achieve an effective emissions reduction under the wide range of operating conditions that arise in real driving conditions. The further development of this strategies is fundamental, especially taking into account the low emissions level allowed by current regulatory procedures and the trend towards zero emissions. The purpose of this dissertation is to analyse the behaviour of the aftertreatment system under very specific but at the same time very common conditions, and developing strategies that provide a further emissions reduction for systems based on three-way catalyst. With the popularization of small turbocharged spark-ignited engines, the use of scavenging strategies to solve the typical low-end torque issues has increased. This dissertation analyses the impact of the short-circuit pulses on both three-way catalyst and ¿ sensors. The short-circuit process has an important effect on the in-cycle dynamics of the exhaust gas composition. In particular, the carbon monoxide and hydrogen pulses followed by fresh air pulses cause a sensor bias. Thus a new method to on-line estimate the short-circuit rate has been proposed. This method allows to correct the sensor bias and, therefore, help to reduce the emissions penalty. To improve the TWC efficiency under transient conditions, not only an accurate air-to-fuel ratio control upstream of the converter is required, but also to consider the dynamic behaviour of the converter itself. For example, the oxygen storage is the main responsible for the converter dynamics, and thus, a good indicator of the catalyst state, but it cannot be directly measured. Hence the development of models is key in current control strategies, to on-line track different parameters related with the state of the converter. Several models have been derived in this dissertation in order to fulfil different requirements, from the prediction of water condensation effects on the temperature evolution inside the converter just after cold-start, to the quantification of the ageing level, through the optimal catalyst purge control, or the air-to-fuel ratio disturbances rejection. / Real Minuesa, M. (2020). Modelling, control and diagnosis of aftertreatment systems based on three-way catalyst in spark-ignited engines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/137040 / TESIS