Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Analysis of Secondary Flow Induced by a 90 Bend in a Pipe Using Mode Decomposition Techniques
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.ORCID iD: 0000-0002-6603-0099
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.ORCID iD: 0000-0001-7330-6965
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In this study unsteady simulations of the flow through and after a 90 pipe bend has been performed by Large Eddy Simulations (LES). In the passenger car engine there is an abundance of pipes and pipe bends. Since pipes and bends are often situated upstream of important engine components the flow in these needs to be well predicted. This entails that there is a need for accurate pipe flow simulations in order to ensure that the inflow conditions, to the e.g. cylinders or turbocharger, are as close to the experimental values as possible. The flow field is further studied by the use of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD). It has been found that there is a low frequency oscillation in the strength of the alternately dominant dean vortex at the exit of the pipe bend. This phenomenon is analysed and the mechanism for it is discussed.

Place, publisher, year, edition, pages
2013.
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-151397OAI: oai:DiVA.org:kth-151397DiVA: diva2:748453
Conference
4th International Conference on Jets, Wakes and Separated Flows, ICJWSF2013
Note

QC 20140919

Available from: 2014-09-19 Created: 2014-09-19 Last updated: 2014-09-19Bibliographically approved
In thesis
1. Large Eddy Simulations of Complex Flows in IC-Engine's Exhaust Manifold and Turbine
Open this publication in new window or tab >>Large Eddy Simulations of Complex Flows in IC-Engine's Exhaust Manifold and Turbine
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis deals with the flow in pipe bends and radial turbines geometries that are commonly found in an Internal Combustion Engine (ICE). The development phase of internal combustion engines relies more and more on simulations as an important complement to experiments. This is partly because of the reduction in development cost and the shortening of the development time. This is one of the reasons for the need of more accurate and predictive simulations. By using more complex computational methods the accuracy and predictive capabilities are increased. The disadvantage of using more sophisticated tools is that the computational time is increasing, making such tools less attractive for standard design purposes. Hence, one of the goals of the work has been to contribute to assess and improve the predictive capability of the simpler methods used by the industry.

By comparing results from experiments, Reynolds Averaged Navier-Stokes (RANS) computations, and Large Eddy Simulations (LES) the accuracy of the different computational methods can be established. The advantages of using LES over RANS for the flows under consideration stems from the unsteadiness of the flow in the engine manifold. When such unsteadiness overlaps the natural turbulence the model lacks a rational foundation. The thesis considers the effect of the cyclic flow on the chosen numerical models. The LES calculations have proven to be able to predict the mean field and the fluctuations very well when compared to the experimental data. Also the effects of pulsatile exhaust flow on the performance of the turbine of a turbocharging system is assessed. Both steady and pulsating inlet conditions are considered for the turbine case, where the latter is a more realistic representation of the real flow situation inside the exhaust manifold and turbine. The results have been analysed using different methods: single point Fast Fourier Transforms (FFT), probe line means and statistics, area and volume based Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD).

Abstract [sv]

Denna avhandling behandlar flödet i rörkrökar och radiella turbiner som vanligtvis återfinns i en förbränningsmotor. Utvecklingsfasen av förbränningsmotorer bygger mer och mer på att simuleringar är ett viktigt komplement till experiment. Detta beror delvis på minskade utvecklingskostnader men även på kortare utevklningstider. Detta är en av anledningarna till att man behöver mer exakta och prediktiva simuleringsmetoder. Genom att använda mer komplexa beräkningsmetoder så kan både nogrannheten och prediktiviteten öka. Nackdelen med att använda mer sofistikerade metoder är att beräkningstiden ökar, vilket medför att sådana verktyg är mindre attraktiva för standardiserade design ändamål. Härav, ett av målen med projektet har varit att bidra med att bedöma och förbättra de enklare metodernas prediktionsförmåga som används utav industrin.

Genom att jämföra resultat från experiment, Reynolds Averaged Navier-Stokes (RANS) och Large Eddy Simulations (LES) så kan nogrannheten hos de olika simuleringsmetoderna fastställas. Fördelarna med att använda LES istället för RANS när det gäller de undersökta flödena kommer ifrån det instationära flödet i grenröret. När denna instationäritet överlappar den naturligt förekommande turbulensen så saknar modellen en rationell grund. Denna avhandling behandlar effekten av de cykliska flöderna på de valda numeriska modellerna. LES beräkningarna har bevisats kunna förutsäga medelfältet och fluktuationerna väldigt väl när man jämför med experimentell data. Effekterna som den pulserande avgasströmning har på turboladdarens turbin prestanda har också kunnat fastställas. Både konstant och pulserande inlopps randvillkor har används för turbinfallet, där det senare är ett mer realistiskt representation av den riktiga strömningsbilden innuti avgasgrenröret och turbinen. Resultaten har analyserats på flera olika sätt: snabba Fourier transformer (FFT) i enskilda punkter, medelvärden och statistik på problinjer, area och volumsbaserade metoder så som Proper Orthogonal Decomposition (POD) samt Dynamic Mode Decomposition (DMD).

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. viii, 68 p.
Series
TRITA-MEK, ISSN 0348-467X ; 2014:20
Keyword
Large Eddy Simulations, Reynolds Averaged Navier-Stokes, Turbocharger, Turbine, Curved Pipes, Pulsatile Flow, Proper Orthogonal Decomposition, Large Eddy Simulations, Reynolds Averaged Navier-Stokes, Turboladdare, Turbin, Rörkrök, Pulserande Flöde, Proper Orthogonal Decomposition
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
urn:nbn:se:kth:diva-151399 (URN)978-91-7595-270-1 (ISBN)
Public defence
2014-10-03, D1, Lindstedtsvägen 17, 5tr, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

QC 20140919

Available from: 2014-09-19 Created: 2014-09-19 Last updated: 2014-09-19Bibliographically approved

Open Access in DiVA

No full text

Authority records BETA

Fjällman, JohanMihaescu, Mihai

Search in DiVA

By author/editor
Fjällman, JohanMihaescu, MihaiFuchs, Laszlo
By organisation
Fluid Physics
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 540 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf