Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths

[EN] Gas dynamic codes are computational tools applied to the analysis of air management in internal combustion engines. The governing equations in one-dimensional elements are approached assuming compressible unsteady non-homentropic flow and are commonly solved applying finite difference numerical methods. These techniques can also be applied to the calculation of flow transport in complex systems such as wallflow monoliths. These elements are characterized by alternatively plugged channels with porous walls. It filters the particulates when the flowgoes through thewall from the inlet to the outlet channels. Therefore, this process couples the solution of every pair of inlet and outlet channels. In this study, the adaptation of the two-step Lax and Wendroff method and the space-time Conservation Element and Solution Element method is performed to be applied in the solution of flow transport in wall-flow monolith channels. The influence on the prediction ability is analysed by a shock-tube test and experimental data obtained under impulsive flow conditions.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion through grant number DPI2010-20891-C02-02.Serrano, JR.; Arnau Martínez, FJ.; Piqueras, P.; García Afonso, Ó. (2014). Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths. International Journal of Computer Mathematics. 91(1):71-84. https://doi.org/10.1080/00207160.2013.783206S718491

Experimental and computational approach to the transient behaviour of wall-flow diesel particulate filters

[EN] The implementation of tight vehicle emission standards has forced manufactures to use aftertreatment systems extensively. In addition to pollutant emissions abatement, these devices have a noticeable impact on the wave pattern. This fact affects the muffler design criteria. All monolithic aftertreatment devices produces a damping effect because of the honeycomb structure and the narrow channels. However, this response is more marked in wall-flow diesel particulate filters (DPF) because of the alternatively plugged ends and the dissipative properties of the porous substrate. The main goal of this paper is to assess the transient fluid-dynamic behaviour of wall-flow DPFs using experimental and modelling techniques. The experimental data were gathered in clean and loaded conditions. The DPF was subjected to a variety of pressure excitations to characterise its transient behaviour in the time and frequency domains. Afterwards, the DPF response was evaluated under engine-like operating conditions in an unsteady flow gas stand. Once the main characteristics of the response were known, a non-linear gas-dynamics model was proposed for analysis and prediction. The model accounts for space and time gradients, combining the thermo-and fluid-dynamic solution with a model based on a packed bed of spherical particles that defines the meso-structure of the loaded substrate. (C) 2016 Elsevier Ltd. All rights reserved.This work has been partially supported by the Spanish Ministerio de Economia y Competitividad through Grant No. TRA2013-40853-R.Torregrosa, AJ.; Serrano, J.; Piqueras, P.; García Afonso, Ó. (2017). Experimental and computational approach to the transient behaviour of wall-flow diesel particulate filters. Energy. 119:887-900. https://doi.org/10.1016/j.energy.2016.11.051S88790011

On the Impact of Particulate Matter Distribution on Pressure Drop of Wall-Flow Particulate Filters

[EN] Wall-flow particulate filters are a required exhaust aftertreatment system to abate particulate matter emissions and meet current and incoming regulations applying worldwide to new generations of diesel and gasoline internal combustion engines. Despite the high filtration efficiency covering the whole range of emitted particle sizes, the porous substrate constitutes a flow restriction especially relevant as particulate matter, both soot and ash, is collected. The dependence of the resulting pressure drop, and hence the fuel consumption penalty, on the particulate matter distribution along the inlet channels is discussed in this paper taking as reference experimental data obtained in water injection tests before the particulate filter. This technique is demonstrated to reduce the particulate filter pressure drop without negative effects on filtration performance. In order to justify these experimental data, the characteristics of the particulate layer are diagnosed applying modeling techniques. Different soot mass distributions along the inlet channels are analyzed combined with porosity change to assess the new properties after water injection. Their influence on the subsequent soot loading process and regeneration is assessed. The results evidence the main mechanisms of the water injection at the filter inlet to reduce pressure drop and boost the interest for control strategies able to force the re-entrainment of most of the particulate matter towards the inlet channels' end.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2016-79185-R. Additionally, the Ph.D. student Enrique Jose Sanchis has been funded by a grant from Universitat Politecnica de Valencia with the reference FPI-2016-S2-1355.Bermúdez, V.; Serrano, J.; Piqueras, P.; Sanchis-Pacheco, EJ. (2017). On the Impact of Particulate Matter Distribution on Pressure Drop of Wall-Flow Particulate Filters. Applied Sciences. 7(3):1-21. https://doi.org/10.3390/app7030234S12173Johnson, T. V. (2015). Review of Vehicular Emissions Trends. SAE International Journal of Engines, 8(3), 1152-1167. doi:10.4271/2015-01-0993Bermúdez, V., Serrano, J. R., Piqueras, P., & García-Afonso, O. (2011). Assessment by means of gas dynamic modelling of a pre-turbo diesel particulate filter configuration in a turbocharged HSDI diesel engine under full-load transient operation. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 225(9), 1134-1155. doi:10.1177/0954407011402278Subramaniam, M. N., Joergl, V., Keller, P., Weber, O., Toyoshima, T., & Vogt, C. D. (2009). Feasibility Assessment of a Pre-turbo After-Treatment System with a 1D Modeling Approach. SAE Technical Paper Series. doi:10.4271/2009-01-1276Luján, J. M., Bermúdez, V., Piqueras, P., & García-Afonso, Ó. (2015). Experimental assessment of pre-turbo aftertreatment configurations in a single stage turbocharged diesel engine. Part 1: Steady-state operation. Energy, 80, 599-613. doi:10.1016/j.energy.2014.05.048Luján, J. M., Serrano, J. R., Piqueras, P., & García-Afonso, Ó. (2015). Experimental assessment of a pre-turbo aftertreatment configuration in a single stage turbocharged diesel engine. Part 2: Transient operation. Energy, 80, 614-627. doi:10.1016/j.energy.2014.12.017Lee, J. H., Paratore, M. J., & Brown, D. B. (2008). Evaluation of Cu-Based SCR/DPF Technology for Diesel Exhaust Emission Control. SAE International Journal of Fuels and Lubricants, 1(1), 96-101. doi:10.4271/2008-01-0072Watling, T. C., Ravenscroft, M. R., & Avery, G. (2012). Development, validation and application of a model for an SCR catalyst coated diesel particulate filter. Catalysis Today, 188(1), 32-41. doi:10.1016/j.cattod.2012.02.007Marchitti, F., Nova, I., & Tronconi, E. (2016). Experimental study of the interaction between soot combustion and NH3-SCR reactivity over a Cu–Zeolite SDPF catalyst. Catalysis Today, 267, 110-118. doi:10.1016/j.cattod.2016.01.027Konstandopoulos, A. G., & Kostoglou, M. (2014). Analysis of Asymmetric and Variable Cell Geometry Wall-Flow Particulate Filters. SAE International Journal of Fuels and Lubricants, 7(2), 489-495. doi:10.4271/2014-01-1510Bollerhoff, T., Markomanolakis, I., & Koltsakis, G. (2012). Filtration and regeneration modeling for particulate filters with inhomogeneous wall structure. Catalysis Today, 188(1), 24-31. doi:10.1016/j.cattod.2011.12.017Iwata, H., Konstandopoulos, A., Nakamura, K., Ogiso, A., Ogyu, K., Shibata, T., & Ohno, K. (2015). Further Experimental Study of Asymmetric Plugging Layout on DPFs: Effect of Wall Thickness on Pressure Drop and Soot Oxidation. SAE Technical Paper Series. doi:10.4271/2015-01-1016Bermúdez, V., Serrano, J. R., Piqueras, P., & García-Afonso, O. (2015). Pre-DPF water injection technique for pressure drop control in loaded wall-flow diesel particulate filters. Applied Energy, 140, 234-245. doi:10.1016/j.apenergy.2014.12.003Serrano, J. R., Bermudez, V., Piqueras, P., & Angiolini, E. (2015). Application of Pre-DPF Water Injection Technique for Pressure Drop Limitation. SAE Technical Paper Series. doi:10.4271/2015-01-0985Wang, Y., Wong, V., Sappok, A., & Munnis, S. (2013). The Sensitivity of DPF Performance to the Spatial Distribution of Ash Inside DPF Inlet Channels. SAE Technical Paper Series. doi:10.4271/2013-01-1584Sappok, A., Govani, I., Kamp, C., Wang, Y., & Wong, V. (2013). In-Situ Optical Analysis of Ash Formation and Transport in Diesel Particulate Filters During Active and Passive DPF Regeneration Processes. SAE International Journal of Fuels and Lubricants, 6(2), 336-349. doi:10.4271/2013-01-0519Torregrosa, A. J., Serrano, J. R., Arnau, F. J., & Piqueras, P. (2011). A fluid dynamic model for unsteady compressible flow in wall-flow diesel particulate filters. Energy, 36(1), 671-684. doi:10.1016/j.energy.2010.09.047CMT-Motores Tèrmicos (Universitat Politècnica de València)www.openwam.orgLax, P. D., & Wendroff, B. (1964). Difference schemes for hyperbolic equations with high order of accuracy. Communications on Pure and Applied Mathematics, 17(3), 381-398. doi:10.1002/cpa.3160170311Serrano, J. R., Arnau, F. J., Piqueras, P., & García-Afonso, O. (2013). Application of the two-step Lax and Wendroff FCT and the CE-SE method to flow transport in wall-flow monoliths. International Journal of Computer Mathematics, 91(1), 71-84. doi:10.1080/00207160.2013.783206Desantes, J. M., Serrano, J. R., Arnau, F. J., & Piqueras, P. (2012). Derivation of the method of characteristics for the fluid dynamic solution of flow advection along porous wall channels. Applied Mathematical Modelling, 36(7), 3134-3152. doi:10.1016/j.apm.2011.09.090Serrano, J. R., Arnau, F. J., Piqueras, P., & García-Afonso, Ó. (2013). Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions. Energy, 58, 644-654. doi:10.1016/j.energy.2013.05.051Murtagh, M. J., Sherwood, D. L., & Socha, L. S. (1994). Development of a Diesel Particulate Filter Composition and Its Effect on Thermal Durability and Filtration Performance. SAE Technical Paper Series. doi:10.4271/940235Fino, D., Russo, N., Millo, F., Vezza, D. S., Ferrero, F., & Chianale, A. (2009). New Tool for Experimental Analysis of Diesel Particulate Filter Loading. Topics in Catalysis, 52(13-20), 2083-2087. doi:10.1007/s11244-009-9393-zKonstandopoulos, A. G., & Johnson, J. H. (1989). Wall-Flow Diesel Particulate Filters—Their Pressure Drop and Collection Efficiency. SAE Technical Paper Series. doi:10.4271/890405Lapuerta, M., Ballesteros, R., & Martos, F. J. (2006). A method to determine the fractal dimension of diesel soot agglomerates. Journal of Colloid and Interface Science, 303(1), 149-158. doi:10.1016/j.jcis.2006.07.066Serrano, J. R., Climent, H., Piqueras, P., & Angiolini, E. (2016). Filtration modelling in wall-flow particulate filters of low soot penetration thickness. Energy, 112, 883-898. doi:10.1016/j.energy.2016.06.121Logan, B. E., Jewett, D. G., Arnold, R. G., Bouwer, E. J., & O’Melia, C. R. (1995). Clarification of Clean-Bed Filtration Models. Journal of Environmental Engineering, 121(12), 869-873. doi:10.1061/(asce)0733-9372(1995)121:12(869)Koltsakis, G. C., & Stamatelos, A. M. (1997). Modes of Catalytic Regeneration in Diesel Particulate Filters. Industrial & Engineering Chemistry Research, 36(10), 4155-4165. doi:10.1021/ie970095mBissett, E. J. (1984). Mathematical model of the thermal regeneration of a wall-flow monolith diesel particulate filter. Chemical Engineering Science, 39(7-8), 1233-1244. doi:10.1016/0009-2509(84)85084-8Galindo, J., Serrano, J. R., Piqueras, P., & García-Afonso, Ó. (2012). Heat transfer modelling in honeycomb wall-flow diesel particulate filters. Energy, 43(1), 201-213. doi:10.1016/j.energy.2012.04.044Payri, F., Broatch, A., Serrano, J. R., & Piqueras, P. (2011). Experimental–theoretical methodology for determination of inertial pressure drop distribution and pore structure properties in wall-flow diesel particulate filters (DPFs). Energy, 36(12), 6731-6744. doi:10.1016/j.energy.2011.10.033Konstandopoulos, A. G., Skaperdas, E., & Masoudi, M. (2002). Microstructural Properties of Soot Deposits in Diesel Particulate Traps. SAE Technical Paper Series. doi:10.4271/2002-01-1015Bermúdez, V., Serrano, J. R., Piqueras, P., & Campos, D. (2015). Analysis of the influence of pre-DPF water injection technique on pollutants emission. Energy, 89, 778-792. doi:10.1016/j.energy.2015.05.14

Filtration modelling in wall-flow particulate filters of low soot penetration thickness

A filtration model for wall-flow particulate filters based on the theory of packed beds of spherical particles is presented to diagnose the combined response of filtration efficiency and pressure drop from a reliable computation of the flow field and the porous media properties. The model takes as main assumption the experimentally well-known low soot penetration thickness inside the porous wall. The analysis of soot loading processes in different particulate filters shows the ability of the proposed approach to predict the filtration efficiency as a function of the particle size distribution. Nevertheless, pressure drop and overall filtration efficiency are determined by the mode diameter of the raw particulate matter emission. The results reveal the dependence of the filtration efficiency in clean conditions on the sticking coefficient. However, the dynamics of the pressure drop and filtration efficiency as the soot loading varies is governed by the soot penetration thickness. This parameter is closely related to the porous wall Peclet number, which accounts for the porous wall and flow properties influence on the deposition process. The effect of the transition from deep bed to cake filtration regime on the pressure drop is also discussed underlying the importance of the macroscale over microscale phenomena.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2013-40853-R. Additionally, the Ph.D. student E. Angiolini has been funded by a grant from Conselleria de Educacio, Cultura i Esport of the Generalitat Valenciana with reference GRISOLIA/2013/036. These supports are gratefully acknowledged by the authors.Serrano Cruz, JR.; Climent, H.; Piqueras, P.; Angiolini, E. (2016). Filtration modelling in wall-flow particulate filters of low soot penetration thickness. Energy. 112:883-898. https://doi.org/10.1016/j.energy.2016.06.121S88389811

Contribution to the understanding of filtration and pressure drop phenomena in wall-flow DPFs

From the last decades of the 20th century, internal combustion engines have undergone a continuous improvement process aimed to the increase of their efficiency and decrease of the pollutants emissions. The reduction of the availability of fossil fuel and the increase of human-made pollution observed in the last decades is leading worldwide to more stringent emission standards that make the engine manufacturers to constantly look for fuel consumption and emission reductions while keeping engine performance. To comply with current and incoming emission regulations, the exhaust line of internal combustion engines has been gradually complicated by the presence of aftertreatment systems. Among them, the particulate filter is the device in charge of abating the emission of soot in the atmosphere. Concerning compression ignition engines, diesel particulate filters (DPF) were first commercially utilized in significant numbers in passenger car and heavy-duty engines since the beginning of the 21st century. Euro 6 emission standards limits the emitted particulate matter from direct injection engines, thus extending the use of particulate filters also to direct injection gasoline engines. A deep knowledge of the phenomena happening inside the DPF is required for the correct understanding of the behaviour of this system and its interaction with the engine. The precise knowledge of the filtration and pressure drop processes is mandatory for the design of the particulate filter and is also essential to wisely think up and analyse solutions aimed to limit the negative impact of the filter on the fuel consumption maintaining its capability of retaining soot particles. Thus, the present work pretends to provide a contribution to the understanding of these phenomena in wall-flow DPFs. The problem has been faced on a computational and experimental basis. A notable part of the work was dedicated to the development and validation of a one-dimensional DPF filtration model to be coupled with the existing pressure drop model. The model was implemented in OpenWAM¿, the open-source gas dynamics software for internal combustion engines and components computation developed at CMT - Motores Térmicos. The developed computational tool was applied to the assessment of the aftertreatment (DOC&DPF) volume downsizing potential in post- and pre-turbo aftertreatment configuration. The study is completed with experimental analysis to support theoretical insights discussing how the soot deposition profile and the particulate layer properties impact on the DPF pressure drop.Desde las últimas décadas del siglo XX, se ha producido un proceso de mejora continua de los motores de combustión interna alternativos con el fin de aumentar su eficiencia y reducir las emisiones contaminantes. La reducción de la disponibilidad de combustibles fósiles y el incremento de la polución de origen antropogénico observados en las ultimas décadas ha provocado el progresivo endurecimiento de las normativas anticontaminación a nivel mundial obligando a los fabricantes de motores a buscar la reducción continua del consumo de combustible y emisiones, manteniendo las prestaciones del motor. El cumplimiento de las actuales y futuras normativas anticontaminación requiere de la instalación de diversos sistemas de postratamiento de gases en la línea de escape de los motores de combustión interna alternativos, aumentando su complejidad. Entre estos sistemas, el filtro de partículas es el equipo encargado de la reducción de la emisión de hollín a la atmósfera. Con respeto a los motores de encendido por compresión, los filtros de partículas diésel se implementaron por primera vez de forma masiva en vehículos de pasajeros y vehículos pesados a principio del siglo XXI. La normativa anti contaminación Euro 6 limita las emisiones de partículas de los motores de inyección directa, extendiendo el uso de filtros de partículas a los motores de inyección directa de gasolina. Es necesario tener un conocimiento profundo de los fenómenos que tienen lugar en el DPF para comprender el comportamiento de este sistema y su interacción con el motor. El conocimiento de los procesos de filtrado y perdida de presión es vital para el diseño del filtro de partículas y resulta esencial para encontrar y analizar soluciones que ayuden a limitar el impacto negativo del DPF sobre el consumo de combustible sin perder la capacidad de retener partículas de hollín. En este contexto, este trabajo pretende aportar una contribucción a la comprensión de estos fenómenos en filtros de partículas de flujo de pared. Esta tarea se ha planteado desde un punto de vista computacional y experimental. Parte importante de este trabajo ha consistido en el desarrollo y validación de un modelo de filtrado unidimensional de DPF que se ha acoplado con el modelo de caida de presión ya existente. El modelo se ha implementado en OpenWAM¿, el software de libre acceso para el cálculo fluidodinámico de motores de combustión interna y sus componentes desarrollado en CMT - Motores Térmicos. La herramienta computacional desarrollada se ha aplicado a la evaluación del potencial de reducción de volumen de sistemas de postratamiento (DOC&DPF) en configuraciones post- y pre-turbo. Este estudio se ha completado con un análisis experimental para dar respaldo a los conceptos teóricos empleados discutiendo como el perfil de deposición del hollín y las propiedades de la capa de partículas afectan a la perdida de presión del DPF.Des les últimes dècades del segle XX, s'ha produït un procés de millora contínua dels motors de combustió interna alternatius amb l'objectiu d'augmentar la seua eficiència i reduir les emissions contaminants. La reducció de la disponibilitat de combustibles fòssils i l'increment de la polució d'origen antropòlogic observats en les últimes dècades ha provocat que les normatives anticontaminació s'han fet més rígides a nivell mundial, obligant als fabricants de motors a buscar la reducció contínua del consum de combustibles i emissions, mantenint les prestacions dels motors. El cumpliment de les normes anticontaminació actuals i futures, requereixen de l'instalació de diversos sistemes de post-tractament de gasos a l'eixida dels motors de combustió interna alternatius, llavors augmentant la complexitat. Entre aquestos sistemes, el filtre de partícules es l'equip encarregat de la reducció de les partícules de sutge a l'atmosfera. Respecte als motors d'encès per compressió, els filtres de partícules van instalar-se de manera massiva als vehicles de passatgers i vehicles pesats al principi del segle XXI. La normativa anti contaminació Euro 6 limita les emissions de partícules dels motors d'inyecció directa, estenent l'ús del filtre de partícules als motors d'injecció directa de gasolina. És necessari tindre un coneixement dels fenòmens que tenen lloc al DPF per a comprendre el comportament del sistema i la seua interacció amb el motor. El coneixement dels processos de filtrat i la pèrdua de pressió és vital per al diseny del filtre de partícules i resulta essencial per a trobar i analitzar les solucions que ajuden a limitar l'impacte negatiu del DPF sobre el consum de combustible sense perdre la capacitat de retenir partícules de sutge. En aquest context, el projecte pretén aportar una contribució a la comprensió d'aquestos fenòmens en els filtres de partícules de flux de paret. Aquesta feina s'ha plantejat des d'un punt de vista computacional i experimental. Part important d'aquest treball ha consistit en el desenvolupament i validació d'un model de filtrat unidimensional de DPF que s'ha acoplat a un model de pèrdua de pressió existent. El model s'ha implementat en OpenWAM¿, el software de lliure accés per al cálcul fluidodinámic de motors de combustió interna i els seus components desenvolupats al CMT - Motores Térmicos. La ferramenta computacional desenvolupada s'ha aplicat a la evaluació del potencial de reducció del volum de sistemes de post tractament (DOC&DPF) en les configuracions post- i pre-turbo. Aquest estudi s'ha completat amb una anàlisi experimental per a donar suport als concepts teòrics emprats discutint com el perfil de la disposició de sutge i les propietats de la capa de partícules que afecten a la pèrdua de pressió del DPF.Angiolini, E. (2017). Contribution to the understanding of filtration and pressure drop phenomena in wall-flow DPFs [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86157TESI

Phenomenological methodology for assessing the influence of flow conditions on the acoustic response of exhaust aftertreatment systems

[EN] The increasing limits of standards on aerosol and gaseous emissions from internal combustion engines have led to the progressive inclusion of different exhaust aftertreatment systems (EATS) as a part of the powertrain. Regulated emissions are generally abated making use of devices based on monolithic structures with different chemical functions. As a side effect, wave transmission across the device is affected and so is the boundary at the exhaust line inlet, so that the design of the latter is in turn affected. While some models are available for the prediction of these effects, the geometrical complexity of many devices makes still necessary in many cases to rely on experimental measurements, which cannot cover all the diversity of flow conditions under which these devices operate. To overcome this limitation, a phenomenological methodology is proposed in this work that allows for the sound extrapolation of experimental results to flow conditions different from those used in the measurements. The transfer matrix is obtained from tests in an impulse rig for different excitation amplitudes and mean flows. The experimental coefficients of the transmission matrix of the device are fitted to Fourier series. It allows treating the influence of the flow conditions on the acoustic response, which is manifested on changes in the characteristic periods, separately from the specific properties of every device. In order to provide predictive capabilities to the method, the Fourier series approach is coupled to a gas dynamics model able to account for the sensitivity of propagation velocity to variations in the flow conditions. (C) 2017 Elsevier Ltd. All rights reserved.This work has been partially supported by the Spanish Ministerio de Economia y Competitividad through Grant no. TRA2013-40853-R. Additionally, the Ph.D. student E.J. Sanchis has been funded by a grant from Universitat Politecnica de Valencia with reference FPI-2016-S2-1355. These supports are gratefully acknowledged by the authors. Finally, the authors wish also to acknowledge the suggestions of the referees, which have resulted in a considerable improvement of the text.Torregrosa, AJ.; Arnau Martínez, FJ.; Piqueras, P.; Sanchis-Pacheco, EJ.; Tartoussi, H. (2017). Phenomenological methodology for assessing the influence of flow conditions on the acoustic response of exhaust aftertreatment systems. Journal of Sound and Vibration. 396:289-306. https://doi.org/10.1016/j.jsv.2017.02.03328930639

Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions

The soot loading process in wall-flow DPFs (diesel particulate filters) affects the substrate structure depending on the filtration regime and produces the increase of pressure drop. Deep bed filtration regime produces the decrease of the porous wall permeability because of the soot particulates deposition inside it. Additionally, a layer of soot particulates grows on the porous wall surface when it becomes saturated. As soot loading increases, the pressure drop across the DPF depends on the porous wall and particulate layer permeabilities, which are in turn function of the substrate and soot properties. The need to consider the DPF pressure drop influence on engine performance analysis or DPF regeneration processes requires the use of low-computational effort models describing the structure of the soot deposition and its effect on permeability. This paper presents a model to describe the micro-scale of the porous wall and the particulate layer structure assuming them as packed beds of spherical particles. To assess the model s capability, it is applied to predict the DPF pressure drop under different experimental conditions in soot loading, mass flow and gas temperature.This work has been partially supported by the Vicerrectorado de Investigacion de la Universitat Politecnica de Valencia through grant number SP20120340-UPPTE/2012/96 and by the Conselleria de Educacio, Cultura i Esport de la Generalitat Valenciana through grant number GV/2013/043.Serrano Cruz, JR.; Arnau Martínez, FJ.; Piqueras Cabrera, P.; García Afonso, Ó. (2013). Packed bed of spherical particles approach for pressure drop prediction in wall-flow DPFs (diesel particulate filters) under soot loading conditions. Energy. 58:644-654. https://doi.org/10.1016/j.energy.2013.05.051S6446545

Modelado de la oxidación del hollín en filtros de partículas diésel

[ES] El continuo endurecimiento de las normativas que regulan las emisiones contaminantes de los motores de combustión ha obligado a su desarrollo ininterrumpido, buscando mejorar su consumo y reducir su impacto medioambiental. Esto ha provocado la introducción progresiva de sistemas de post-tratamiento de gases de escape en los motores de combustión a fin de limitar la emisión de sustancias contaminantes a la atmósfera. En el caso concreto de la emisión de partículas, se ha estandarizado el empleo de filtros de partículas de flujo de pared como solución tecnológica para el cumplimiento de las normativas vigentes tanto en motores diésel (DPF) como gasolina (GPF). Por el propio mecanismo de funcionamiento de estos filtros se produce una acumulación de hollín dentro y sobre sus paredes porosas. Esta acumulación tiene un gran efecto sobre el comportamiento fluidodinámico del filtro, afectando a la pérdida de presión y, de ahí, aumentando el consumo específico del motor. Por este motivo, y dada la limitada capacidad de acumulación del filtro, se realizan procesos de regeneración para eliminar las partículas de hollín almacenadas. Se recurre para ello a dos estrategias complementarias. Por un lado, se tienen las estrategias de regeneración activa, que se realizan de forma periódica, mediante un aporte externo de energía. De entre estas estrategias, el método más habitual es el uso de post-inyecciones de combustible. Por otro lado, existen estrategias pasivas, que conducen a la oxidación del hollín sin fuentes de energía externa y reducen la frecuencia de los eventos de regeneración activa. La definición de dichas estrategias, así como su control, requieren del uso de herramientas computacionales para lograr una mayor comprensión y permitir la optimización de estos procesos. En este contexto, la presente tesis doctoral ofrece una contribución al modelado de los procesos de regeneración. Parte importante de este trabajo ha consistido en el desarrollo y validación de un modelo de regeneración que se ha implementado en un modelo termofluidodinámico 1D de DPF ya existente. Esta herramienta se ha desarrollado proponiendo una definición detallada del mecanismo de oxidación de hollín, presentándose un análisis del efecto de las etapas que lo componen. El modelo propuesto también se ha adaptado para su uso en un modelo de valor medio de DPF, que junto al modelo de reactividad química de catalizadores de oxidación desarrollado en el contexto de esta tesis, ha sido empleado en el análisis de la influencia de la variación de los parámetros básicos de la estrategia de post-inyección sobre la regeneración del DPF. Por otra parte, es sabido que el balance entre las etapas de carga y regeneración del filtro determina la distribución de las partículas en su interior. Así, esta tesis se completa con un estudio acerca del efecto de la distribución de las partículas sobre el comportamiento del DPF y cómo la distribución no homogénea de las partículas en el filtro condiciona el proceso de regeneración activa, afectando también a las hipótesis a considerar para su correcto modelado. Como consecuencia de estos trabajos se ha definido un conjunto de herramientas computacionales que facilitan la comprensión de los procesos de regeneración y que son aplicables al amplio rango de casos de estudio considerados.[CA] El continu enduriment de les normatives que regulen les emissions contaminants dels motors de combustió ha obligat al seu desenvolupament ininterromput, buscant millorar el seu consum i reduir el seu impacte mediambiental. Açò ha provocat la introducció progressiva de sistemes de post-tractament de gasos de fuga en els motors de combustió a fi de limitar l'emissió de substàncies contaminants a l'atmosfera. En el cas de l'emissió de partícules, s'ha estandarditzat l'utilització de filtres de partícules de flux de paret com a solució tecnològica per al compliment de les normatives vigents tant en motors dièsel (DPF) com gasolina (GPF). Pel propi mecanisme de funcionament estos filtres es produïx una acumulació de sutja dins i sobre les seues parets porosas. Esta acumulació té un gran efecte sobre el comportament fluidodinàmic del filtre, afectant la pèrdua de pressió i, d'aci, augmentant el consum específic del motor. Per este motiu, i per la limitada capacitat d'acumulació del filtre, es realitzen processos de regeneració per a eliminar les partícules de sutja emmagatzemades. Es recorre per a això a dos estratègies complemetaries. Per una banda, es tenen les estratègies de regeneració activa, que es realitzen de forma periòdica, per mitjà d'una aportació externa d'energia. D'entre estes estratègies, el mètode més habitual es l'ús de post-injeccions de combustible. D'altra banda, hi ha estratègies passives, que conduïxen a l'oxidació de la sutja sense fonts externes d'energia i reduïxen la freqüència dels esdeveniments de regeneració activa. La definició de les estratègies, així com el seu control, requerixen de l'ús de ferramentes computacionals per a aconseguir una mitjor comprensió i permetre l'optimització d'estos proccesos. En este context, la present tesi doctoral oferix una contribució al modelatge dels processos de regeneració. Part important d'este treball ha consistit en el desenvolupament i validació d'un model de regeneració que s'ha implementat en un model termofluidodinàmic 1D de DPF ja existent. Esta ferramenta s'ha desenvolupat proposant una definició detallada del mecanisme d'oxidació de sutja, presentant-se una anàlisi de l'efecte de les etapes que ho componen. El model proposat també s'ha adaptat per al seu ús en un model de valor mitjà de DPF, que junt amb el model de reactivitat química de catalitzadors d'oxidació desenvolupat en el context d'esta tesi, ha sigut empleat en l'anàlisi de la influència de la variació dels paràmetres bàsics de l'estratègia de post-injecció sobre la regeneració del DPF. D'altra banda, és sabut que el balanç entre les etapes de càrrega i regeneració del filtre determina la distribució de les partícules en el seu interior. Així, esta tesi es completa amb un estudi sobre l'efecte de la distribució de les partícules sobre el comportament del DPF i com la distribució no homogènia de les partícules en el filtre condiciona el procés de regeneració activa, afectant també les hipòtesis a considerar per al seu correcte modelatge. Com a conseqüència d'estos treballs s'ha definit un conjunt de ferramentes computacionals que faciliten la comprensió dels processos de regeneració i que són aplicables a l'ampli rang de casos d'estudi considerats.[EN] The continuous tightening of emission regulations for internal combustion engines has forced their uninterrupted development, seeking to improve their fuel consumption and reduce their environmental impact. This fact has led to the progressive introduction of exhaust aftertreatment systems in combustion engines in order to limit the emission of polluting substances into the atmosphere. In the specific case of particle emission, the use of wall flow particle filters has been standardized as a technological solution to comply with current regulations both in diesel (DPF) and gasoline (GPF). The operating principle of these filters results in an accumulation of soot inside and on their porous walls. This accumulation has an important effect on the fluid-dynamic behavior of the filter, affecting the pressure drop and, hence, increasing the specific consumption of the engine. For this reason, and due to the limited accumulation capacity of the filter, regeneration processes are carried out to remove the stored soot particles, where two main strategies can be found. On the one hand, there are active regeneration strategies, that are performed periodically, through an external supply of energy. Among these strategies, the most common method is the use of post-injections. On the other hand, there are passive strategies that lead to soot oxidation without external energy sources and reduce the frequency of active regeneration events. The definition of the strategies, as well as their control, require the use of computational tools to achieve a comprehensive understanding and optimization of these processes. In this context, this doctoral thesis offers a contribution to the modeling of regeneration processes. An important part of this work was dedicated to the development and validation of a regeneration model that was implemented in an existing DPF thermofluid dynamic 1D model. This tool proposes a detailed definition of the soot oxidation mechanism, presenting an analysis of the effect of the steps that comprise it. The proposed model was also adapted for its use in a DPF mean value model and, together with the oxidation catalysts chemical reactivity model developed in the context of this thesis, has been used in the analysis of the influence of variation in the basic parameters of the post-injection strategy. Furthermore, it is known that the balance between the filter loading and regeneration stages determines the soot distribution. Thus, this thesis is completed with a study about the effect of the particle distribution on the behavior of the DPF and how the non-homogeneous distribution of the particles determines the active regeneration process, also affecting the hypotheses to be considered for its correct modeling. As a result of these studies, a set of computational tools was defined to allow the understanding of regeneration processes that are applicable in the wide range of case studies considered.Sanchis Pacheco, EJ. (2019). Modelado de la oxidación del hollín en filtros de partículas diésel [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120455TESI

Development of advanced methods for the simulation of the reacting mixture formation in internal combustion engines with the use of machine learning algorithms

Besides increasing the share of electric and hybrid vehicles, in order to comply with more stringent environmental protection limitations, in the mid-term the auto industry must improve the efficiency of the internal combustion engine and the well to wheel efficiency of the employed fuel. To achieve this target, a deeper knowledge of the phenomena that influence the mixture formation and the chemical reactions involving new synthetic fuel components is mandatory, but complex and time intensive to perform purely by experimentation. Therefore, numerical simulations play an important role in this development process, but their use can be effective only if they can be considered accurate enough to capture these variations. The most relevant models necessary for the simulation of the reacting mixture formation and successive chemical reactions have been investigated in the present work, with a critical approach, in order to provide instruments to define the most suitable approaches also in the industrial context, which is limited by time constraints and budget evaluations. To overcome these limitations, new methodologies have been developed to conjugate detailed and simplified modelling techniques for the phenomena involving chemical reactions and mixture formation in non-traditional conditions (e.g. water injection, biofuels etc.). Thanks to the large use of machine learning and deep learning algorithms, several applications have been revised or implemented, with the target of reducing the computing time of some traditional tasks by orders of magnitude. Finally, a complete workflow leveraging these new models has been defined and used for evaluating the effects of different surrogate formulations of the same experimental fuel on a proof-of-concept GDI engine model.Besides increasing the share of electric and hybrid vehicles, in order to comply with more stringent environmental protection limitations, in the mid-term the auto industry must improve the efficiency of the internal combustion engine and the well to wheel efficiency of the employed fuel. To achieve this target, a deeper knowledge of the phenomena that influence the mixture formation and the chemical reactions involving new synthetic fuel components is mandatory, but complex and time intensive to perform purely by experimentation. Therefore, numerical simulations play an important role in this development process, but their use can be effective only if they can be considered accurate enough to capture these variations. The most relevant models necessary for the simulation of the reacting mixture formation and successive chemical reactions have been investigated in the present work, with a critical approach, in order to provide instruments to define the most suitable approaches also in the industrial context, which is limited by time constraints and budget evaluations. To overcome these limitations, new methodologies have been developed to conjugate detailed and simplified modelling techniques for the phenomena involving chemical reactions and mixture formation in non-traditional conditions (e.g. water injection, biofuels etc.). Thanks to the large use of machine learning and deep learning algorithms, several applications have been revised or implemented, with the target of reducing the computing time of some traditional tasks by orders of magnitude. Finally, a complete workflow leveraging these new models has been defined and used for evaluating the effects of different surrogate formulations of the same experimental fuel on a proof-of-concept GDI engine model

Proceedings of the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008

This volume contains full papers presented at the 10th International Chemical and Biological Engineering Conference - CHEMPOR 2008, held in Braga, Portugal, between September 4th and 6th, 2008.FC