Technological approaches to improve the engine efficiency and to reduce pollutant emissions of automotive diesel engines.

The research work was mainly focused on the technological approach to improve engine efficiency and reduce pollutant emissions applicable to diesel engines which are very often incompatible were assessed through a set of full- scale tests on a real diesel engine in order to satisfy the new emissions limits. (1) The first strategy evaluated in this work to improve the engine efficiency was the reduction of the mechanical losses: through the incorporation of nanomaterials in the lubricant formulation. The effect of the lubricant oil additivated with MoS2 nanopowders was assessed through a set of full - scale tests on a real diesel engine – several engine points and cooling water temperatures were investigated for both a reference oil and a MoS2-additivated one. (2) Other strategy to reduce pollutant emissions included in this PhD thesis was the effects of using a 30% by volume blend of a renewable fuel, called Farnesane, and fossil diesel in a small Euro 5 displacement passenger car diesel engine. (3) And finally, the CeO2/BaO/Pt system was selected in order to perform an NO2-assisted soot oxidation, as a aftertreatment strategy to reduce pollutant emissions. The aim of such catalytic system is to couple the catalytic functionality for soot abatement during DPF regeneration, namely CeO2, and an embedded lean NOx trap (LNT) functionality given by BaO, for NOx storage, whose oxidation over Pt to form adsorbed nitrates is facilitated by the presence of CeO2 itself

Control-oriented modelling and diagnostics of diesel after-treatment catalysts

[ES] Esta tesis doctoral abarca el desarrollo de algoritmos orientados a mejorar el sistema de control de emisiones en motores Diesel. Para este propósito, la inclusión en el vehículo de sensores embarcados como los de temperatura, los de NOx o el de NH3 permite realizar diagnóstico a bordo de los sistemas de post-tratamiento foco de este trabajo, los cuales son el DOC y el SCR. Así pues, el objetivo es el de satisfacer las normativas de diagnóstico a bordo para mantener las emisiones por debajo del umbral permitido por la normativa a lo largo del tiempo. Los tests experimentales, incluyendo las medidas con analizador de gases, permiten tener una visión más amplia de las especies en la línea de escape. Complementariamente, se utilizan unidades nuevas y envejecidas para tener el efecto experimental del envejecimiento en los catalizadores. De esta manera, se analiza el efecto de la temperatura, el gasto de escape, las concentraciones de las especies y el envejecimiento en el DOC y en el SCR, así como la evaluación de algunas de las medidas relevantes realizadas por los sensores. Las temperaturas tienen una influencia destacada en el funcionamiento de los catalizadores, por lo que se requiere la evaluación de las medidas de los sensores de temperatura, junto con el desarrollo de modelos de transmisión de calor, para alimentar las funciones a continuación desarrolladas. En este sentido, la medida lenta del sensor aguas arriba del DOC se mejora en condiciones transitorias mediante una técnica de fusión de la información basada en un filtro de Kalman. Luego, se presenta un modelo de transmisión de calor 1D y un modelo agrupado 0D, en los cuales se evalúan las entradas aguas arriba según el uso del modelo. Por otra parte, se presenta una técnica para estimar el incremento de temperatura debido a la oxidación de los pulsos de post-inyección en el DOC. Se proponen modelos para ambos DOC y SCR para estimar el efecto del envejecimiento en las emisiones, en los cuales el factor de envejecimiento es modelado como un parámetro sintonizable que permite variar desde estados nuevos a envejecidos. Por una parte, un modelo agrupado 0D es desarrollado para el DOC con el propósito de estimar el desliz de HC y CO, el cual es validado en un WLTC para después ser usado en simulación. Por otra parte, un modelo 1D y un modelo 0D se desarrollan para el SCR, los cuales se usan a continuación para alimentar la estrategia de diagnóstico y para simulación. Finalmente, las estrategias de diagnóstico se presentan para fallo total o retirada de DOC, así como para la estimación de la eficiencia en DOC y SCR. Por una parte, la primera estrategia se divide en pasiva y activa, en la que se usan post-inyecciones en la activa para excitar el sistema y confirmar el fallo total si es el caso. A continuación, la eficiencia del DOC se estima a través de una técnica indirecta en la que la temperatura de activación se detecta y se relaciona con el incremento de emisiones a través del modelo. Por otra parte, se desarrolla un observador para estimar el estado de envejecimiento del SCR, el cual está basado en un filtro de Kalman extendido. Sin embargo, para evitar asociar baja eficiencia del catalizador debido a pobre calidad de la urea inyectada, a envejecimiento del SCR, un indicador de la calidad de la urea se ejecuta en paralelo.[CA] Esta tesi doctoral abasta el desenvolupament d'algoritmes orientats a millor el sistema de control d'emissions en motors Diesel. Per a este propòsit, la inclusió en el vehicle de sensor embarcats com els de temperatura, els de NOx o el d'NH3 permet realitzar el diagnòstic a bord dels sistemes de post-tractament focus d'este treball, els quals són el DOC i el SCR. Així doncs, l'objectiu és el de satisfer les normatives de diagnòstic a bord per a mantindre les emissions per baix de l'umbral permés per la normativa al llarg del temps. Els tests experimentals, incloent les mesures amb analitzador de gasos, permeten obtindre una visió més àmplia de les espècies en la línia d'escapament. Complementàriament, s'utilitzen unitats noves i envellides per tal de tindre l'efecte experimental de l'envelliment en els catalitzadors. D'aquesta manera, s'analitza l'efecte de la temperatura, la despesa d'escapament, les concentracions de les espècies i l'envelliment en el DOC i en el SCR, així com l'avaluació d'algunes mesures rellevants realitzades pels sensors. Les temperatures tenen una influència destacada en el funcionament dels catalitzadors, pel que es requerix l'avaluació de les mesures dels sensors de temperatura, junt amb el desenvolupament de models de transmissió de calor, per a alimentar les funcions a continuació desenvolupades. En este sentit, la mesura lenta del sensor a l'entrada del DOC es millora en condicions transitòries mitjançant una tècnica de fusió de la informació basada en un filtre de Kalman. Després, es presenta un model de transmissió de calor 1D i un model agrupat 0D, en els quals s'avaluen les entrades a l'entrada segons l'ús del model. Per altra banda, es presenta una tècnica per a estimar l'increment de temperatura degut a l'oxidació dels polsos de post-injecció en el DOC. Es proposen models per a DOC i SCR per a estimar l'efecte de l'envelliment en les emissions, en els quals es modela el factor d'envelliment com un paràmetre sintonitzable, que permet variar des d'estats nous a envellits. Per altra banda, un model agrupat 0D _es desenvolupat per al DOC amb el propòsit d'estimar la relliscada de HC i CO, el qual és validat en un WLTC per a després ser usat en simulació. Per altra banda, un model 1D i un model 0D es desenvolupen per al SCR, els quals s'usen a continuació per a alimentar l'estratègia de diagnòstic i per a simulació. Finalment, les estratègies de diagnòstic es presenten per a la fallada total o retirada del DOC, així com per a l'estimació de l'eficiència en DOC i SCR. Per altra banda, la primera estratègia es divideix en passiva i activa, en la que s'utilitzen post-injeccions en la activa per a excitar el sistema i confirmar la fallada total si es dona el cas. A continuació, l'eficiència del DOC s'estima a través d'una tècnica indirecta en la que la temperatura d'activació es detecta i es relaciona amb l'increment d'emissions a través del model. Per altra banda, es desenvolupa un observador per a estimar l'estat d'envelliment del SCR, el qual està basat en un filtre de Kalman extés. No obstant això, per a evitar associar baixa eficiència degut a pobre qualitat de l'urea injectada a l'envelliment del SCR, un indicador de la qualitat de l'urea s'executa en paral·lel.[EN] This dissertation covers the development of algorithms oriented to improve the emission control system of Diesel engines. For this purpose, the inclusion of on-board sensors like temperature, NOx and NH3 sensors allows performing on-board diagnostics to the after-treatment systems focus of this work, which are the DOC and the SCR system. Then, the target is to meet on-board diagnostics regulations in order to keep emissions below a regulation threshold over time. Experimental tests, including gas analyzer measurements, allow having a wider view of the species in the exhaust line. Complementary, new and aged units are used in order to have the experimental effect of ageing on the catalysts. Then, the effect of temperature, exhaust mass flow, species concentrations and ageing is analyzed for DOC and SCR, in combination with the assessment of some relevant sensors measurements. As a result, the characteristics, opportunities and limitations extracted from experimental data are used as the basis for the development of models and diagnostics techniques. The assessment of temperature sensors measurements, along with the development of heat transfer models is required to feed temperature dependent functions. In this sense, the slow measurement of the DOC upstream temperature sensor is improved in transient conditions by means of a data fusion technique, based on a fast model and a Kalman filter. Then, a 1D and a 0D lumped heat transfer models are presented, in which the upstream inputs are assessed in relation to its use. On the other hand, a technique to estimate the temperature increase due to post-injection pulses oxidation is also presented. Both DOC and SCR models are proposed in order to estimate the effect of ageing on emissions, in which an ageing factor is modelled as a tunable parameter that allows varying from new to aged states. On the one hand, a 0D lumped model is developed for DOC in order to estimate the HC and CO species slip, which is validated in a WLTC and is then used for simulation. On the other hand, a 1D and a 0D models are developed for SCR, which are then used to feed the diagnostics strategy and for simulation. Finally, diagnostics strategies are presented for total failure or removal of DOC, as well as for efficiency estimation of DOC and SCR. On the one hand, the former strategy is separated into passive and active diagnostics, in which post-injections are used in active diagnostics in order to excite the system and confirm a total failure, in case. Then, the DOC efficiency estimation is done by means of an indirect technique in which the light-off temperature is detected and an emissions increase is related by means of the DOC ageing model. On the other hand, an observer to estimate the SCR ageing state is developed, which is based on an extended Kalman filter. However, in order to avoid associating low SCR efficiency to ageing, an indicator of the injected urea quality is developed to run in parallel.Mora Pérez, J. (2018). Control-oriented modelling and diagnostics of diesel after-treatment catalysts [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115937TESI

The Impact of Biodiesel-based Na on the Durability of Cu-Zeolite SCR Catalysts and Other Diesel Aftertreatment Devices

Biodiesel fuel has increased in popularity in recent years as an alternative fuel choice, but there are concerns related to the impact it will have on diesel engines and aftertreatment systems relative to conventional diesel fuel. One major concern is the presence of sodium (Na) in finished biodiesel fuel due to the use of Na-hydroxyl as a liquid-phase catalyst during biodiesel synthesis. The current study focuses on determining the impact of biodiesel-based Na on the performance and materials characterization of diesel aftertreatment devices including lean NOx traps (LNT), diesel oxidation catalysts (DOC), diesel particulate filters (DPF), and Cu-zeolite selective catalytic reduction (SCR) catalysts. Long-term engine aged LNT, DOC, and DPF samples are provided by research partners, while a 517 cc single-cylinder Hatz diesel engine is used to perform accelerated Na-aging of aftertreatment systems consisting of a DOC, SCR, and DPF in either the light-duty (DOC-SCR-DPF) or heavy-duty (DOC-DPF-SCR) configuration. Bench-flow reactor (BFR) evaluations reveal that the performance of LNT and DOC catalysts is negligibly affected by exposure to Na, but that Cu-zeolite SCR in the light-duty configuration suffers a drastic reduction in nitrogen oxide (NOx) performance. The performance loss can be avoided by placing the SCR downstream of the DPF in the heavy-duty aftertreatment configuration, but electron microprobe analysis (EPMA) of the DPF from this configuration identifies excessive Na ash buildup and migration of Na into the DPF substrate. v EPMA analysis of the Na-aged SCR determined that the contamination pattern is similar to that observed in the long-term engine-aged DOC and LNT samples, providing credibility to the accelerated Na-aging process. Materials characterization techniques including diffuse-reflective infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and BET surface area measurements determined that loss of catalyst surface area and a decrease in the number of active Cu sites for ammonia (NH3) adsorption and SCR reactions are the most likely cause of the reduced nitrogen oxides (NOx) performance in the light-duty configuration accelerated Na-aged SCR. Finally, mathematical modeling successfully predicts the performance of fresh SCR catalysts, but is less accurate for catalysts exposed to elevated levels of Na

Catalysis in Diesel engine NOx aftertreatment: a review

AbstractThe catalytic reduction of nitrogen oxides (NOx) under lean-burn conditions represents an important target in catalysis research. The most relevant catalytic NOx abatement systems for Diesel engine vehicles are summarized in this short review, with focus on the main catalytic aspects and materials. Five aftertreatment technologies for Diesel NOx are reviewed: (i) direct catalytic decomposition; (ii) catalytic reduction; (iii) NOx traps; (iv) plasma-assisted abatement; and (v) NOx reduction combined with soot combustion. The different factors that can affect catalytic activity are addressed for each approach (e.g. promoting or poisoning elements, operating conditions, etc.). In the field of catalytic strategies, the simultaneous removal of soot and NOx using multifunctional catalysts, is at present one of the most interesting challenges for the automotive industry

Synthesis and Characterization of Support-Modified Nanoparticle-Based Catalysts and Mixed Oxide Catalysts for Low Temperature CO Oxidation

Heterogeneous catalysts are responsible for billions of dollars of industrial output and have a profound, if often understated, effect on our everyday lives. New catalyst technologies and methods to enhance existing catalysts are essential to meeting consumer demands and overcoming environmental concerns. This dissertation focuses on the development of catalysts for low temperature carbon monoxide oxidation. CO [carbon monoxide] oxidation is often used as a probe reaction to test overall oxidation activity of a given catalyst and is an important reaction in the elimination of toxic pollutants from automotive exhaust streams. The work included here presents three new heterogeneous catalysts developed over the last 4 years in our group. The first type Au/SiO2 [gold/silica] catalyst synthesized using a new method for the deposition of Au nanoparticles onto SiO2 via a nitrogen-containing polymer, C3N4 [carbon nitride]. C3N4-modification of SiO2 allows us to ignore unfavorable electrostatic effects that hinder standard Au deposition onto this support. While removal of the C3N4 is necessary for good CO oxidation, this new method is an improvement over the standard deposition-precipitation procedure for supports with low isoelectric point that enables the successful deposition of Au nanoparticles onto SiO2. The second type includes precious metal catalysts deposited on an “inert” silica support but promoted by the addition of an “active” metal oxide. Here we present a Au/FeOx/SiO2 [gold/iron oxide/silica] and a Pd/ZrO2/SiO2 [palladium/zirconia/silica] catalyst which show increased activity and stability effects due to the presence of the metal oxide promoter. They are synthesized by a C3N4-deposition and sol-gel methods, respectively. These catalysts were also tested in simulated automotive exhaust streams. The results show that inhibition effects play a major role in the activity of these catalysts. The third type of catalyst is a mixed oxide catalyst, CuO-Co­3O4-CeO2 [copper oxide-cobalt oxide-cerium oxide], developed with the goal of overcoming the inhibition effects seen in the previous precious metal catalysts. The catalyst was synthesized by co-precipitation method and shows exceptional activity for CO oxidation under simulated exhaust conditions. Also noteworthy is the observation that this catalyst also shows a lack of inhibition by a common exhaust component, propene

Catalytic processes for the control of nitrogen oxides emissions in the presence of oxygen.

The emissions of nitrogen oxides (NOx) from power plant and vehicles are known to cause damages to human health and environmental safety. The introduction of the EURO 6 regulations has imposed new limits on emissions of different types of pollutants present in the flue gases of diesel engines. In particular, the emission limits of autovehicles are different between stoichiometric oxygen-to-fuel ratios and oxygen-lean engine conditions: the latter ones are responsible of large amounts of particulate matter (PM) and nitrogen oxides (NOx), which are very dangerous air pollutants. Conversely, since under stoichiometric conditions PM emissions are quite negligible and NOx can be fruitfully removed by catalytic abatement, the former have been regulated by more stringent legislation. However, emissions limits are becoming stricter and stricter in recent years also for lean engines, although in the presence of oxygen the abatement of NOx results in a much harder task. Also for stationary plant, such as coffee roasters, the NOx emissions will be limited and the new regulations will be enforced from April 2016, and also in these applications the presence of oxygen in the pollutants-containing gas will make any abatement process very difficult. For these reasons, to fulfil the requests of the more stringent regulations, it is important to develop more efficient technologies which result in prevention of pollutants formation, together with improved abatement process for the pollutants emitted in the flue gases. NOx emission levels from autovehicles have been reduced by 66% from Euro 5, requiring the use of NOx after-treatment devices in addition to in-cylinder measures such as cooled EGR (Exhaust gas recirculation). LNTs (Low NOx Trap) have shown good NOx reduction performance and durability while SCR (Selective Catalytic Reduction), while offering also good NOx reduction performance, offers more flexibility for fuel economy and reduction of CO2 emissions. Manufacturers will likely choose the NOx after-treatment technology based on a combination of cost, reliability, fuel economy, and consumer acceptance. In large stationary applications (power plants, chemical industry, etc.), the issue of the NOx removal is often accomplished through the post-treatment of the exhaust gases by means of the selective catalytic reduction (SCR) method. The main advantages got from the exploitation of this technology are its high efficiency and its reliability as well as stability of the catalytic reaction, but the high cost represents a considerable drawback as well as the need to have a proper temperature range of effective performances that obliges to place SCR unit. In addition to these general limits, a further drawback of ammonia SCR process lies in the low acceptability of such a technology in some different contexts, such as the food industry, due to the unpleasant smell and danger of the reactant molecule employed. The extension to vehicle exhausts is very interesting too, provided that a proper catalytic system is developed in ordered to answer to the different requests of mobile NOx sources. The most important difference in the operating conditions can be represented by the range temperature of interest for the process. Hence, SCR devices could be even employed in mobile applications after adequate and calibrated system revision and modification in order to give effectiveness at lower light-off temperature (120 °C), since no solution seems to be viable with non-specific reducers (CO, HCs) mainly in the presence of O2, for instance in diesel engines. In particular, the development of ―Low Temperature‖ NH3-SCR catalysts that work in the range of temperature from 120 to 300 °C is considered an ideal way to control NOx emissions also from stationary sources besides being an unavoidable necessity for vehicles. As a matter of fact, the reduction of the nitrogen oxides by means of ammonia in an oxidizing atmosphere has raised the need of the development of new catalysts, characterized by low cost and capability of ensuring high conversions, even at relatively low temperatures. On the other hand, such a solution appears to be not viable for specific applications such as coffee roasters in food engineering, due to the unacceptance of ammonia, costs and safety reasons. Much more interesting could appear the attempt to prevent pollutant formation by developing intrinsically clean upstream processes. In the present PhD, I focused my attention on the research of lower cost, versatility, environment-friendly nature and, of course, performer catalysts. The work was devoted to synthesize, characterize and testing of MnOx and MnOx-CeO2 catalysts proposed as innovative LT SCR catalysts, and a series of other catalytic systems for the selective oxidation of the organic compound emitted by an industrial roaster of coffee, in order to prevent the NOx formation in such devices. Generally, Mn is used in both reduction and oxidation reactions due to its various types of labile oxygen as well as to the presence of different structures and morphologies. To the best of our knowledge, the optimal oxidation state of the metal has not been assessed for the SCR reaction, despite numerous studies dealing with the role of MnOx and the deactivation of the catalysts. Manganese oxides were investigated as catalysts for low-T SCR. Different MnOx catalysts were prepared by means of different operating conditions and characterized, as well as tested in the SCR process under lab-scale conditions. The goal was thereafter to understand the suitable Mn oxidation state necessary for SCR performances and to study the nature of active sites, which does not seem to be well clarified to date although a great research effort in this field has been made in the last two decades. The contribute of CeO2 with MnOx was investigate so the solution combustion route was chosen for synthesizing MnOx-CeO2 catalysts. The Mn/Ce molar ratio as well as quality and quantity of organic fuel in the reaction were investigated as key parameters and their influence on the structural, microstructural and superficial properties was studied. Moreover, the redox property of MnOx-CeO2 samples and the synergistic effect of Ce4+ and Mnn+ ions were analysed. All these properties were correlated to the catalytic activity in order to optimize the parameters for the best catalytic performance. We have already tried to correlate some chemical properties of the surface with the performances in the NH3-SCR of pure MnOx samples prepared by the SCS technique and in this paper a direct comparison among those results and the evidences obtained for the Mn-Ce catalysts will be performed. On the other hand, and also in connection with a project sponsored by a coffee-maker company, the issue of removal of NOx from roasting effluent was faced by studying catalysts and reactor conditions/configuration to prevention of the formation of nitrogen oxides itself. The attention was given to catalysts consisting of nanoparticles of transition metals, such as copper, nickel, iron and manganese, which replace in part or in full the platinum group catalyst, usally used in industrial context to abate the large mass of VOC emitted in the process. A homogenous dispersion and control the size of the nanoparticles on the substrate was necessary to develop the most effective catalysts and with a higher yield. The total or partial replacement of the platinum group with nanoparticles of transition metal catalysts leads to a considerable reduction in costs and also to the strengthening of sustainability and a secure supply of raw materials for EU producers. The replacement of the catalyst with an oxidative catalyst active and selective at low temperature allows both to reduce VOCs (Volatile Organic Compounds) and the CO is to reduce the nitrogen compounds to molecular nitrogen

Durability Demonstration Procedures of Emission Control Devices for Euro 6 Vehicles

The implementation of increasingly demanding vehicle emissions standards fostered the improvement of existing aftertreatment technologies and the development of innovative solutions. However, new vehicle standards are only beneficial if effectively lead to emissions reduction; this implies assuring compliance with emissions limits not only for new registrations but also throughout vehicles’ useful life. With this aim, current legislation introduced emissions durability requirements; alternatively to actual in-use driving, the normative also proposes tailored accelerated aging procedures for PI and CI vehicles (Standard Bench Cycle and Standard Diesel Bench Cycle respectively) or the application of assigned deterioration factors. Whereas the fast aging protocol for vehicles with PI engine had already been successfully applied, the newly introduced approach for CI vehicles fast aging still has to prove its validity. The present report aims at contributing to a deeper understanding of aftertreatment system aging mechanisms and methods in order to assess Euro-6 vehicles durability approach. An overview on the legislative background is given before introducing an investigation on deterioration mechanisms that could critically affect most commonly implemented aftertreatment devices. The current accelerated aging procedure is then presented in greater detail, with focus on differences between gasoline and diesel vehicles approach; differences between European and American fast aging strategies are also discussed. The Standard Diesel Bench Cycle is examined in detail and focus is brought on potential deficiencies to match real diesel aftertreatment system aging mechanisms; open issues are discussed and complemented with the proposal for suitable solutions which are being jointly developed by US Research Institutes and Industries. Finally, a review of deterioration factors currently available for Euro-6 like vehicles is presented, in order to evaluate the variability of performance degradation for latest aftertreatment technologies.JRC.F.8-Sustainable Transpor

Nanoparticle-based electrochemical sensors for the detection of lactate and hydrogen peroxide

In the present study, electrochemical sensors for the detection of lactate and hydrogen peroxide were constructed by exploiting the physicochemical properties of metal ad metal oxide nanoparticles. This study can be divided into two main sections. While chapter 2, 3, and 4 report on the construction of electrochemical lactate biosensors using CeO2 and CeO2-based mixed metal oxide nanoparticles, chapter 5 and 6 show the development of electrochemical hydrogen peroxide sensors by the decoration of the electrode surface with palladium-based nanoparticles. First generation oxidase enzyme-based sensors suffer from oxygen dependency which results in errors in the response current of the sensors in O2-lean environments. To address this challenge, the surface of the sensors must be modified with oxygen rich materials. In this regard, we developed a novel electrochemical lactate biosensor design by exploiting the oxygen storage capacity of CeO2 and CeO 2-CuO nanoparticles. By the introduction of CeO2 nanoparticles into the enzyme layer of the sensors, negative interference effect of ascorbate which resulted from the formation of oxygen-lean regions was eliminated successfully. When CeO2-based design was exposed to higher degree of O2 -depleted environments, however, the response current of the biosensors experienced an almost 21 % decrease, showing that the OSC of CeO2 was not high enough to sustain the enzymatic reactions. When CeO2-CuO nanoparticles, which have 5 times higher OSC than pristine CeO2, were used as an oxygen supply in the enzyme layer, the biosensors did not show any drop in the performance when moving from oxygen-rich to oxygen-lean conditions. In the second part of the study, PdCu/SPCE and PdAg/rGO-based electrochemical H2O2 sensors were designed and their performances were evaluated to determine their sensitivity, linear range, detection limit, and storage stability. In addition, practical applicability of the sensors was studied in human serum. The chronoamperometry results showed that the PdCu/SPCE sensors yielded a high sensitivity (396.7 µA mM -1 cm-2), a wide linear range (0.5 -11 mM), and a low limit of detection (0.7 µM) at the applied potential of -0.3 V. For PdAg/rGO sensors, a high sensitivity of 247.6 ± 2.7 µA˙mM -1˙cm-2 was obtained towards H2O 2 in a linear range of 0.05 mM to 28 mM

Advanced DOC-DPF Model to Predict Soot Accumulation and Pressure Drop in Diesel Particulate Filters

Diesel Particulate Filters (DPFs) are regarded as the most effective technology to reduce particulate matter (PM) emissions from modern diesel engines. PM mass collected inside the filter needs to be periodically oxidized to clean the porous walls in order to avoid excessive backpressure that could negatively affect engine and turbocharger performances leading to higher fuel consumption. Diesel Oxidation Catalysts (DOCs), on the other hand, represent an effective means to reduce hydrocarbon (HC) emissions and set the proper chemical conditions at the inlet of the DPF to enhance soot oxidation during filter regeneration. Due to the impact that these devices have on tailpipe emissions, monitoring functions aimed at assessing the health of these systems need to be implemented in the engine on-board diagnostics (OBD) system. Further, in-depth understanding of filtration and regeneration mechanisms, together with the ability of predicting actual DPF loading conditions, could play a key role in optimizing regeneration strategies adopted to keep the particulate filter within safe operating conditions. Hence, the use of real-time, yet accurate models is of primary importance to face with advanced control challenges, such as the integration of DOCs and DPFs with the engine or other critical aftertreatment components, or to properly develop model-based OBD monitors.;This study aims at addressing the challenges related with real-time modeling of both DOCs and DPFs with special regard to the calibration of key parameters. At first, the development of a 1-D model for the diesel oxidation catalyst is presented;: two different approaches representing two different trade-offs in terms of model complexity/speed are discussed and analyzed. A 1-D model of a DPF is then presented, addressing the coupling of filtration and regeneration over cake, washcoat and wall thicknesses. Moreover, the approach followed to develop the DPF model is innovative as it is directly integrated via analytical functions, thus improving the discretized approach used in similar models. Finally, an innovative model tuning methodology called Virtual Conditioning is presented and applied to generate robust model calibrations.;Numerical results are compared with experimental data gathered at West Virginia University\u27s (WVU) Engine and Emissions Research Laboratory (EERL) using a Mack heavy-duty diesel engine coupled to a Johnson Matthey C-CRT aftertreatment system. The study shows that: a) DOC model is capable of predicting outlet emissions concentrations with an accuracy within 15% and minimal computational requirements over both steady-state and transient operating conditions; b) DPF wall and washcoat layer present different regeneration and collection dynamics, whose behavior is important to capture filter pressure drop and temporal evolution of the collected mass; c) Advanced filtration and regeneration process treatment in the wall together with a robust calibration process allow for the use of constant model parameters to replicate combinations of steady-state and transient engine cycles; and d) the model can be used to track back pressure and mass history of DPFs under subsequent regeneration and loading processes with an accuracy of 20%