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An Assessment of CFD Applied to Steady Flow in a Planar Diffuser Upstream of an Automotive Catalyst Monolith

SAE International Journal of Engines

Coventry Univ.-Sophie Porter, Svetlana Aleksandrova, Stephen Benjamin, Carol A. Roberts, Jonathan Saul
Universiti Teknikal Malaysia Melaka-Ahmad Kamal Mat Yamin
  • Journal Article
  • 2014-01-2588
Published 2014-10-13 by SAE International in United States
Flow maldistribution across automotive exhaust catalysts significantly affects their conversion efficiency. Flow behaviour can be predicted using computational fluid dynamics (CFD). This study investigates the application of CFD to modelling flow in a 2D system consisting of a catalyst monolith downstream of a wide-angled planar diffuser presented with steady flow. Two distinct approaches, porous medium and individual channels, are used to model monoliths of length 27 mm and 100 mm. Flow predictions are compared to particle image velocimetry (PIV) measurements made in the diffuser and hot wire anemometry (HWA) data taken downstream of the monolith. Both simulations compare favourably with PIV measurements, although the models underestimate the degree of mixing in the shear layer at the periphery of the emerging jet. Tangential velocities are predicted well in the central jet region but are overestimated elsewhere, especially at the closest measured distance, 2.5 mm from the monolith. The individual channels model is found to provide a more consistently accurate velocity profile downstream of the monolith. Maximum velocities, on the centre line and at the secondary peak…
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Methodology for Modelling a Combined DPF and SCR Catalyst with the Porous Medium Approach in CFD

SAE International Journal of Engines

Coventry Univ.-S. F. Benjamin, C. A. Roberts
  • Journal Article
  • 2014-01-2819
Published 2014-10-13 by SAE International in United States
In an attempt to reduce particulate and NOx emissions from Diesel exhaust, the combined DPF and SCR filter is now frequently chosen as the preferred catalyst. When this device functions effectively it saves valuable packaging space in a passenger vehicle. As part of its development, modelling of its emissions performance is essential. Single channel modelling would seem to be the obvious choice for an SCRF because of its complex internal geometry. This, however, can be computationally demanding if modelling the full monolith. For a normal flow-through catalyst monolith the porous medium approach is an attractive alternative as it accounts for non-uniform inlet conditions without the need to model every channel. This paper attempts to model an SCRF by applying the porous medium approach. The model is essentially 1D but as with all porous medium models, can very easily be applied to 3D cases once developed and validated. The model is described in full in this paper and values for all the key parameters are presented. The filter is assumed to collect soot in the inlet…
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Using Vehicle Simulation to Investigate Controllability

SAE International Journal of Alternative Powertrains

Coventry Univ.-Damian Harty, Teena Gade
Protean Electric Ltd.-Michael Ellims, Helen Elizabeth Monkhouse
  • Journal Article
  • 2013-01-0180
Published 2013-04-08 by SAE International in United States
All functional safety standards have some definition of “risk” and the automotive standard ISO 26262 is no exception. Risk is related to the exposure, the severity of the outcome, and in the case of ISO 26262, the controllability in relation to a specific vehicle hazard or hazards associated with the behavior of the vehicle or part of the vehicle. Thus hazards are central to understanding the risk associated with systems.When considering traditional power train systems, based on internal combustion engines or centralized electric motors, hazards are most usually limited to unintended acceleration and deceleration. The situation is complicated somewhat with the introduction of electronically controlled differentials, which can induce limited amounts of induced yaw, as can ABS and ESC. In a similar manner, replacing the centralized driveline system with in-wheel electric motors brings with it a similar set of issues.In this paper we describe the work undertaken to qualitatively identify the hazards associated with in-wheel motors and to quantify the vehicle level effects that could be expected. With this being done to ensure that, when…
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Experimental Study of SCR in a Light-Duty Diesel Exhaust to Provide Data for Validation of a CFD Model Using the Porous Medium Approach

Coventry Univ.-C. A. Roberts, S. F. Benjamin
Univ. Teknikal Malaysia Melaka-N. Tamaldin
Published 2010-04-12 by SAE International in United States
Removal of NOx from a light-duty diesel automotive exhaust system can be achieved by SCR reactions using aqueous urea spray as the reductant. Measurements of emissions from such a system are necessary to provide data for CFD model validation. A test exhaust system was designed that featured an expansion can, nozzle and diffuser arrangement to give a controlled flow profile to define an inlet boundary for a CFD model and to approximate to one-dimensional flow. Experiments were carried out on the test exhaust using injection of either ammonia gas in nitrogen or aqueous urea spray. Measurements were made of NO, NO₂ and NH₃ at inlet to and exit from the SCR using a CLD analyzer. The NO and NO₂ profiles within the bricks were found by measuring at the exit from different length bricks. The spray and gas measurements were compared, and insights into the behavior of the droplets upstream and within the bricks were obtained. Approximately half to three-quarters of the droplets from the spray remained as droplets at entry to the first brick.…
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An analysis methodology for the simulation of vehicle pedestrian accidents

Coventry Univ.-N. Le Glatin, M. V. Blundell, G. Blount
  • Technical Paper
  • 2002-04-0090
Published 2002-09-24 by Institution of Mechanical Engineers in United Kingdom
This paper outlines an analysis methodology for the validation of pedestrian accident simulations to help engineers and designers to apply simulation is the area with increasing confidence. The research undertaken will support the automotive industry and the coming requirement to design future vehicles that offer improved protection to the pedestrian on impact. The simulations performed aim to represent more realistic pedestrian accidents, as they occur in the real world. The work presents particular problems in terms of validation of the individual components of the system. In particular the modelling of the pedestrian presents challenges in terms of establishing the biofidelity of the model. To facilitate the analysis of real- world, pedestrian-to-vehicle accidents, a Design of Experiments (DoE) methodology has been adopted to manage a wide range of accident scenarios. The DoE statistical model has been used to provide conclusions on predictive pedestrian post-impact kinematics and injury criteria.

Design of experiments simulation of real-world pedestrian accidents

Coventry Univ.-N. Le Glatin, M. V. Blundell, S. Thorpe, G. Blount
Motor Industry Research Association-G. Brown, B. Allan-Stubbs
  • Technical Paper
  • 2002-04-0075
Published 2002-05-28 by Institution of Mechanical Engineers in United Kingdom
This paper describes a study carried out to develop and apply computer analysis tools to simulate accidents between vehicles and pedestrians. The work is timely due to coming proposed regulation and will support the automotive industry and the requirement to design future vehicles that afford pedestrians more protection. The simulations performed aim to represent pedestrian accidents as they occur in the real world. The problems of validating computer models of a humanoid, a vehicle and the mechanics of impact are discussed. To facilitate the analysis of a wide range of impact events a Design of Experiment (DOE) methodology has been adopted to represent the critical variables. The DOE statistical model has been used to provide conclusions on predictive pedestrian injury criteria and compare them to real-world accident data.

Investigation into the use of adaptable car structures concepts for pedestrian impact protection

Coventry Univ.-M. V. Blundell
Siemens Restraint Systems GmbH-J. Hoffman, A. Kretzschmar
  • Technical Paper
  • 2002-04-0073
Published 2002-05-28 by Institution of Mechanical Engineers in United Kingdom
This paper describes the initial findings from a program of research undertaken to investigate pedestrian protection in terms of vehicle design concepts. The work is considered to be timely as new European legislation will require car manufacturers to pass a series of tests considered representative of a frontal impact between the vehicle and a pedestrian. The work has been carried out by Siemens Restraint Systems GmbH in collaboration with Benteler Automobiltechnik, Festo, Peguform and Coventry University.Findings from an initial literature study are presented that provide statistical evidence for pedestrian injuries and fatalities on the road. Publications in this area indicate that while there has been improvement over the previous decades the level of injuries and deaths amongst pedestrians is still not tolerable, hence the impetus to develop new legislation and to carry out programs of work such as this.The work presented is based on a study in which active- reversible bumper and bonnet concepts were designed, built and subsequently tested. The material contained here is based primarily on the bonnet concepts at this stage. It…
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Design Opportunities Given Zero Failure Eelectronics

Coventry Univ.-M. Blundell, S. Bush
Mayflower Vehicle Systems Ltd.-S. Buckley, T. King
Published 2002-03-04 by SAE International in United States
This paper describes a program of work that aims to demonstrate the potential benefits in vehicle body design and construction resulting from the availability of zero failure electrical and electronic systems. Thereby creating a technology “pull” rather than the more normal technology “push”.The work undertaken by the consortium involved a comparative analysis of an existing benchmark vehicle structure and a modified structure incorporating novel features which exploit the concept of zero failure electronics. The body was nominally divided into three compartments and each of these separately analysed for reduced number of parts, reduced costs and simplified manufacture and assembly. The overriding criteria was that the structural performance could not be compromised. Changes that were not specifically due to the advent of zero failure electronics were also not allowed. Software tools, such as Design For Assembly (DFA) and Finite Element Analysis (FEA) were used in the process.The results were very encouraging and estimates of the overall weight saving, reduced component count, reduced manufacture and assembly time have all been calculated and will be presented. The reduction…
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A Comparison of Steady, Pulsating Flow Measurements and CFD Simulations in Close Coupled Catalysts

Coventry Univ.-A. Arias-García, S. F. Benjamin, H. Zhao
ArvinMeritor Ltd.-S. Farr
Published 2001-09-24 by SAE International in United States
Performance improvements of automotive catalytic converters can be achieved by improving the flow distribution of exhaust gases within the substrate. The flow distribution is often assumed to be adequately described by measurements obtained from steady flow rigs. An experimental study was carried out to characterise the flow distribution through the substrate of a close-coupled catalytic converter for both steady and pulsating conditions on a flow rig and on a motored engine. Computational fluid dynamic (CFD) simulations were also performed. On the flow rig, the flow from each port was activated separately discharging air to different regions of the substrate. This resulted in a high degree of flow maldistribution. For steady flow maldistribution increased with Reynolds number. Pulsating the flow resulted in a reduction in flow maldistribution. Different flow distributions were observed on the motored engine when compared to composite maps derived from the rig. For the engine study significantly more flow activity was observed at the periphery of the substrate, each port contributing to the net flow. The results suggest that strong port interactions occur.…
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A Study of the Effect of Flow Pulsations on the Flow Distribution within Ceramic Contoured Catalyst Substrates

Coventry Univ.-S. F. Benjamin, C. A. Roberts, J. Wollin
Published 2001-05-07 by SAE International in United States
This study examines the effect of pulsating flow on the flow distribution through contoured substrates. Three ceramic contoured substrates of equal volume were assessed. Two of the substrates were cone shaped with different cone angles and one had a dome shaped front face. The flow distribution was measured for a range of flow rates and pulsation frequencies. Computational Fluid Dynamics (CFD) simulations were also performed. It is shown how a contoured substrate can provide improvements in flow uniformity and that they are less sensitive to changes in flow rate and pulsation frequency when compared to the case of a standard substrate. Improvements in the prediction of flow distribution are reported when substrate “entrance effects” are accounted for.
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