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

Iterative Methods and Dynamics for Nonlinear Problems

Kim, Y.; Cordero Barbero, A.; Sharma, J.; Soleymani, F.; Torregrosa Sánchez, JR.; Wang, X. (2017). Iterative Methods and Dynamics for Nonlinear Problems. Discrete Dynamics in Nature and Society. 1-1. doi:10.1155/2017/8592140S1

Derivation of the method of characteristics for the fluid dynamic solution of flow advection along porous wall channels

This paper describes in detail a novel formulation of the method of characteristics for its application to solve one-dimensional compressible unsteady non-homentropic flow advected along porous wall channels. In particular, the method is implemented into a wall-flow monolith Diesel particulate filter model whose purpose is the pressure drop prediction. The flow inside the monolith channels is considered to be one-dimensional and the flow through the porous wall treated as a source term agree with the Darcy's law. The flow dynamic behaviour at internal nodes of the channels is solved by means of shock capturing methods, whereas the end nodes, or boundary conditions, are solved applying the method of characteristics. The derived solution in this study of the Riemann variables and the entropy level includes the variation along the space-time plane due to cross-section area changes, friction and heat transfer as traditionally stated, but also takes into account the key influence on every line of the flow leaving or entering to the channels through the porous walls. © 2011 Elsevier Inc.Desantes Fernández, JM.; Serrano Cruz, JR.; Arnau Martínez, FJ.; Piqueras Cabrera, P. (2012). Derivation of the method of characteristics for the fluid dynamic solution of flow advection along porous wall channels. Applied Mathematical Modelling. 36:3134-3152. doi:10.1016/j.apm.2011.09.090S313431523

Experimental theoretical methodology for determination of inertial pressure drop distribution and pore structure properties in wall-flow diesel particulate filters (DPFs)

Wall-flow particulate filters have been placed as a standard technology for Diesel engines because of the increasing restrictions to soot emissions. The inclusion of this system within the exhaust line requires the development of computational tools to properly simulate its flow dynamics and acoustics behaviour. These aspects become the key to understand the influence on engine performance and driveability as a function of the filter placement. Since the pressure drop and the filtration process are strongly depending on the pore structure properties - permeability, porosity and pore size - a reliable definition of these characteristics is essential for model development. In this work a methodology is proposed to determine such properties based on the combination of the pressure drop rement in a steady flow test rig and two theoretical approaches. The later are a lumped model and a one-dimensional (1D) unsteady compressible flow model. The purpose is to simplify the integration of particulate filters into the global engine modelling and development processes avoiding the need to resort to specific and expensive characterisation tests. The proposed methodology was validated against measurements of the response of an uncoated diesel particulate filter (DPF) under different flow conditions as cold steady flow, impulsive flow and hot pulsating flow. © 2011 Elsevier Ltd.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion through grant number DPI2010-20891-C02-02.Payri González, F.; Broatch Jacobi, JA.; Serrano Cruz, JR.; Piqueras Cabrera, 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. https://doi.org/10.1016/j.energy.2011.10.033S67316744361

Semilocal convergence by using recurrence relations for fifth-order method in Banach spaces

In this paper, a semilocal convergence result in Banach spaces of an efficient fifth-order method is analyzed. Recurrence relations are used in order to prove this convergence, and some a priori error bounds are found. This scheme is finally used to estimate the solution of an integral equation and so, the theoretical results are numerically checked. We use this example to show the better efficiency of the current method compared with other existing ones, including Newton's scheme.This research was supported by Ministerio de Ciencia y Tecnologia MTM2011-28636-C02-{01,02}.Cordero Barbero, A.; Hernandez-Veron, MA.; Romero, N.; Torregrosa Sánchez, JR. (2015). Semilocal convergence by using recurrence relations for fifth-order method in Banach spaces. Journal of Computational and Applied Mathematics. 273:205-213. https://doi.org/10.1016/j.cam.2014.06.008S20521327

Application of Global Positioning System and questionnaires data for the study of driver behavior on two-lane rural roads

This paper is a preprint of a paper accepted by IET Intelligent Transport Systems and is subject to Institution of Engineering and Technology Copyright. When the final version is published, the copy of record will be available at IET Digital LibraryMethodologies based on naturalistic observation provide the most accurate data for studying drivers' behaviour. This study presents a new methodology to obtain naturalistic data related to drivers' behaviour in a road segment. It is based on the combination of using global positioning system data and drivers' questionnaires. The continuous speed profiles along a road segment and the characteristics of drivers, of their trips and the type of their vehicles can be obtained for a great amount of drivers. It has already been successfully used for several studies, such as the development of models to estimate operating speed profile in two-lane rural road segments; or the characterisation of driving styles. These operating speed models have been the key for the development of a new geometric design consistency model, allowing an easier road safety evaluation. Besides, knowledge on the human factors that influence speed choice may be useful for road safety media campaigns and education programs designers, and also for the improvement of intelligent driver assistance systems.The authors thank 'Centre for Studies and Experimentation of Public Works (CEDEX)' of the 'Spanish Ministry of Public Works' that partially subsidizes the research. We also wish to thank to the 'General Directorate of Public Works, Urban Projects and Housing' of the 'Infrastructure, Territory and Environment Department' of the 'Valencian Government', to the 'Valencian Provincial Council' and to the 'General Directorate of Traffic' of the 'Ministry of the Interior' for their cooperation in field data gathering.Pérez Zuriaga, AM.; Camacho Torregrosa, FJ.; Campoy Ungria, JM.; García García, A. (2013). Application of Global Positioning System and questionnaires data for the study of driver behavior on two-lane rural roads. IET Intelligent Transport Systems. 7(2):182-189. doi:10.1049/iet-its.2012.0151S18218972Fourie, M., Walton, D., & Thomas, J. A. (2011). Naturalistic observation of drivers’ hands, speed and headway. Transportation Research Part F: Traffic Psychology and Behaviour, 14(5), 413-421. doi:10.1016/j.trf.2011.04.009Gibreel, G. M., Easa, S. M., & El-Dimeery, I. A. (2001). Prediction of Operating Speed on Three-Dimensional Highway Alignments. Journal of Transportation Engineering, 127(1), 21-30. doi:10.1061/(asce)0733-947x(2001)127:1(21)Fitzpatrick, K., & Collins, J. M. (2000). Speed-Profile Model for Two-Lane Rural Highways. Transportation Research Record: Journal of the Transportation Research Board, 1737(1), 42-49. doi:10.3141/1737-06Bella, F. (2008). Driving simulator for speed research on two-lane rural roads. Accident Analysis & Prevention, 40(3), 1078-1087. doi:10.1016/j.aap.2007.10.015Van Nes, N., Houtenbos, M., & Van Schagen, I. (2008). Improving speed behaviour: the potential of in-car speed assistance and speed limit credibility. IET Intelligent Transport Systems, 2(4), 323. doi:10.1049/iet-its:20080036Warner, H. W., & Åberg, L. (2006). Drivers’ decision to speed: A study inspired by the theory of planned behavior. Transportation Research Part F: Traffic Psychology and Behaviour, 9(6), 427-433. doi:10.1016/j.trf.2006.03.004Goldenbeld, C., & van Schagen, I. (2007). The credibility of speed limits on 80km/h rural roads: The effects of road and person(ality) characteristics. Accident Analysis & Prevention, 39(6), 1121-1130. doi:10.1016/j.aap.2007.02.012Zuriaga, A. M. P., García, A. G., Torregrosa, F. J. C., & D’Attoma, P. (2010). Modeling Operating Speed and Deceleration on Two-Lane Rural Roads with Global Positioning System Data. Transportation Research Record: Journal of the Transportation Research Board, 2171(1), 11-20. doi:10.3141/2171-02Ottesen, J. L., & Krammes, R. A. (2000). Speed-Profile Model for a Design-Consistency Evaluation Procedure in the United States. Transportation Research Record: Journal of the Transportation Research Board, 1701(1), 76-85. doi:10.3141/1701-10Park, P. Y., Miranda-Moreno, L. F., & Saccomanno, F. F. (2010). Estimation of speed differentials on rural highways using hierarchical linear regression models. Canadian Journal of Civil Engineering, 37(4), 624-637. doi:10.1139/l10-002Wasielewski, P. (1984). Speed as a measure of driver risk: Observed speeds versus driver and vehicle characteristics. Accident Analysis & Prevention, 16(2), 89-103. doi:10.1016/0001-4575(84)90034-4Williams, A. F., Kyrychenko, S. Y., & Retting, R. A. (2006). Characteristics of speeders. Journal of Safety Research, 37(3), 227-232. doi:10.1016/j.jsr.2006.04.001Lajunen, T., Karola, J., & Summala, H. (1997). Speed and Acceleration as Measures of Driving Style in Young Male Drivers. Perceptual and Motor Skills, 85(1), 3-16. doi:10.2466/pms.1997.85.1.3Af Wåhlberg, A. E. (2006). Speed choice versus celeration behavior as traffic accident predictor. Journal of Safety Research, 37(1), 43-51. doi:10.1016/j.jsr.2005.10.01

Analysis of shock capturing methods for chemical species transport in unsteady compressible flow

This paper presents a chemical species transport model to account for variable composition and gas properties along the flow path in internal combustion engines. The numerical solution to adapt the gas dynamic model to chemical species transport in boundary conditions by means of the Method of Characteristics and in volumes by means of a filling and emptying model is described. The performance for chemical species transport in 1D elementsof shock-capturing methods, such as the two-step Lax Wendroff method and the Sweby s TVD scheme considering several flux limiter definitions, is carried out by means of shocktube tests. The influence of the fluid modelling as perfect or non-perfect gas on the numerical methods features and the flow characteristics on shock-tube results are analysed.This work has been partially supported by the Spanish Ministerio de Ciencia e Innovacion through grant number DPI2010-20891-C02-02.Serrano Cruz, JR.; Climent, H.; Piqueras, P.; García Afonso, Ó. (2013). Analysis of shock capturing methods for chemical species transport in unsteady compressible flow. Mathematical and Computer Modelling. 57(7-8):1751-1759. https://doi.org/10.1016/j.mcm.2011.11.026S17511759577-

Pre-DPF water injection technique for pressure drop control in loaded wall-flow diesel particulate filters

Wall-flow type diesel particulate filter (DPF) is a required aftertreatment system for particle emission abatement and standards fulfilment in Diesel engines. However, the DPF use involves an important flow restriction, especially as the substrate gets soot and ash loaded. It gives as a result the increase of the exhaust back-pressure and hence a fuel consumption penalty. The increasing damage of fuel consumption with DPF soot loading leads to the need of the regeneration process. Usually based on active strategies, this process involves an additional fuel penalty but prevents from excessive DPF pressure drop and ensures secure soot burnt out. Under this context, new solutions are required to improve the state of the art DPF soot loading to pressure drop ratio. This paper presents a novel technique based on pre-DPF water injection to reduce the DPF pressure drop under soot loading conditions by disrupting its dependence on soot/ash loading. It provides benefits to engine fuel economy and also higher flexibility for DPF regeneration and maintenance. The work covers a test campaign performed in a passenger car turbocharged Diesel engine equipped with a wall-flow DPF. The main objective is to describe the technique, to provide a figure of its potential for pressure drop control and fuel consumption reduction. The results of the experiments also confirm soot and ash loading capacity increase and demonstrate the lack of negative effects on filtration efficiency and active and passive regeneration.This work has been partially supported by the Spanish Ministry of Economy and Competitiveness through Grant No. TRA2013-40853-R.Bermúdez Tamarit, VR.; Serrano Cruz, JR.; Piqueras Cabrera, P.; García Afonso, Ó. (2015). Pre-DPF water injection technique for pressure drop control in loaded wall-flow diesel particulate filters. Applied Energy. 140:234-245. https://doi.org/10.1016/j.apenergy.2014.12.003S23424514

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02