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Flow decomposition methods applied to the flow in an IC engine manifold
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).ORCID iD: 0000-0001-7330-6965
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
2014 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 65, no 1-2, 57-65 p.Article in journal (Refereed) Published
Abstract [en]

Large Eddy Simulation (LES) of the flow and mixing in an engine manifold of a six cylinder Diesel engine is carried out. Proper Orthogonal Decomposition (POD) and Dynamical Mode Decomposition (DMD) are applied to sets of LES data from these computations. The engine manifold under consideration includes a pipe-junction used for Exhaust Gas Recirculation (EGR). The methods of analysis, POD and DMD, are applied to the velocity field and the exhaust concentration field. It is found that POD facilitates the analysis of the pulsating, complex and turbulent flow field as compared to instantaneous fields. The flow field is dominated by the EGR pulses and their interaction with other pulses originating from the cylinder valves. The maldistribution of EGR concentration among the first cylinder ports can clearly be linked to the EGR pulsations. DMD is able to extract flow structures at certain frequencies. Using these properties of DMD, the motion of the EGR pulses can be extracted and visualized. The combination of LES and flow decomposition is found to give a rational for the interpretation of the flow phenomena, which might facilitate the optimization of engine manifolds in terms of EGR non-uniformity.

Place, publisher, year, edition, pages
2014. Vol. 65, no 1-2, 57-65 p.
Keyword [en]
Engine Flow, IC engine, flow decomposition, POD, DMD
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-117926DOI: 10.1016/j.applthermaleng.2013.12.082ISI: 000335099100007Scopus ID: 2-s2.0-84893039564OAI: oai:DiVA.org:kth-117926DiVA: diva2:603915
Note

QC 20140305. Updated from manuscript to article in journal.

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Computation and Analysis of EGR Mixing in Internal Combustion Engine Manifolds
Open this publication in new window or tab >>Computation and Analysis of EGR Mixing in Internal Combustion Engine Manifolds
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis deals with turbulent mixing processes occurring in internal combustion engines, when applying exhaust gas recirculation (EGR). EGR is a very efficient way to reduce emissions of nitrogen oxides (NOx) in internal combustion engines. Exhaust gases are recirculated and mixed with the fresh intake air, reducing the oxygen con- centration of the combustion gas and thus the peak combustion temperatures. This temperature decrease results in a reduction of NOx emissions. When applying EGR, one is often faced with non-uniform distribution of exhaust among and inside the cylinders, deteriorating the emission performance. The mixing of exhaust gases and air is governed by the flow in the engine intake manifold, which is characterized by unsteadiness due to turbulence and engine pulsations. Moreover, the density cannot be assumed to be constant due to the presence of large temperature variations.Different flow cases having these characteristics are computed by compressible Large Eddy Simulations (LES). First, the stationary flows in two T-junction type geometries are investigated. The method is validated by comparison with experimental data and the accuracy of the simulations is confirmed by grid sensitivity studies. The flow structures and the unsteady flow modes are described for a range of mass flow ratios between the main and the branch inlet. A comparison to RANS computations showed qualitatively different flow fields.Thereafter, pulsating inflow conditions are prescribed on the branch inlet in or- der to mimic the large pulsations occurring in the EGR loop. The flow modes are investigated using Dynamical Mode Decomposition (DMD).After having established the simulation tool, the flow in a six-cylinder engine is simulated. The flow is studied by Proper Orthogonal Decomposition (POD) and DMD. The mixing quality is studied in terms of cylinder-to-cylinder non-uniformity and temporal and spatial variances. It was found that cycle-averaging of the concentration may give misleading results. A sensitivity study with respect to changes in the boundary conditions showed that the EGR pulsations, have large influence on the results. This could also be shown by POD of the concentration field showing the significance of the pulses for the maldistribution of exhaust gases.Finally, the flow in an intake manifold of a four-cylinder engine is investigated in terms of EGR distribution. For this geometry, pipe bends upstream of the EGR inlet were found to be responsible for the maldistribution.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. vi, 62 p.
Series
Trita-MEK, ISSN 0348-467X ; 2013:02
Keyword
Turbulent Mixing, Large Eddy Simulation, URANS, Internal Combustion Engines, Intake Manifolds, T-junction, Exhaust Gas Recirculation
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-117911 (URN)978-91-7501-639-9 (ISBN)
Public defence
2013-02-22, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20130207

Available from: 2013-02-07 Created: 2013-02-07 Last updated: 2013-07-03Bibliographically approved

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Mihaescu, Mihai

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