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
GT-Power Report
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics.ORCID iD: 0000-0002-6603-0099
2013 (English)Report (Other academic)
Abstract [en]

Presently in the vehicle industry full engine system simulations are performedusing dierent one-dimensional software programs in order to assess the eectof dierent geometrical and part changes on the system as a whole. Thesesimulations are usually fast and multiple parameters can be monitored andanalysed.In this report GT-Power simulations have been performed on a completeengine designed by Volvo Car Corporation. The investigation was performedin order to gain basic knowledge about the internal combustion engine andspecically about the gas exchange system and the turbocharger. A parameterstudy was performed and the responses on the turbine eciency and breaktorque were analysed.The trends in the simulation results follow the background theory well, i.e.increasing the turbine eciency increases the engine eciency and reduces thetime to torque. The eect of the valve opening times and durations on thebreak torque and the turbine eciency can be studied. There is an intricaterelationship where the optimal conguration is dependent on the engine speedas well as the opening angles and times.GT-Power is a very powerful tool for simulating complete engines. Howevercare must be taken when analysing the results. The code only uses one directionand time, meaning that the ow will always be uniform in the cross sections.Whereas in many parts of the real engine the ow eld is three dimensional andfar from uniform in the cross-sections.

Place, publisher, year, edition, pages
2013.
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-123083OAI: oai:DiVA.org:kth-123083DiVA: diva2:624472
Note

QC 20130603

Available from: 2013-05-31 Created: 2013-05-31 Last updated: 2014-09-19Bibliographically approved
In thesis
1. Unsteady simulations of the turbulent flow in the exhaust system of an IC-engine for optimal energy utilization
Open this publication in new window or tab >>Unsteady simulations of the turbulent flow in the exhaust system of an IC-engine for optimal energy utilization
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This licentiate thesis deals with the ow in pipe bends and radial turbines inan internal combustion engine environment. Looking into the engine bay of apassenger car one cannot avoid noticing all the pipe bends and splits. Duringthe development of internal combustion engines the engine manufacturers arestarting to focus more on simulations than on experiments. This is partly becauseof the reduction in cost but also the reduction in turn around time. This isone of the reasons for the need of more accurate and predictive simulations.By using more complex computational methods the accuracy and predictivecapabilities are increased. The downside is that the computational time isincreasing so the long term goal of the project is to use the results to improvethe predictive capability of the lower order methods used by the industry.By comparing experiments, Reynolds Averaged Navier-Stokes (RANS)simulations, and Large Eddy Simulations (LES), the accuracy of the simulationmethods can be established. The advantages of using LES over RANS for the ows under consideration stems from the unsteadiness of the ow in the enginemanifolds. When such unsteadiness overlaps the natural turbulent spectrum,general RANS models cannot handle the problem specic ow. The thesisconsiders this eect on the chosen numerical model. The LES results have beenshown to be more accurate than the RANS simulations both for global meanvalues and for the uctuating components. The LES calculations have provento predict the mean

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. 116 p.
Series
Trita-MEK, ISSN 0348-467X ; 2013:11
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-123086 (URN)978-91-7501-782-2 (ISBN)
Presentation
2013-06-14, E3, Osquarsbacke 14, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20130603

Available from: 2013-06-03 Created: 2013-05-31 Last updated: 2013-06-03Bibliographically approved
2. 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

GT-Power Report(1182 kB)2308 downloads
File information
File name FULLTEXT01.pdfFile size 1182 kBChecksum SHA-512
55a6a1ce6a6afbccd36470d407fdd2f8d5cb8de2cd91c07dee92075162b4edcd505c6c87bd542472fe168460f3dea30b76e6a1c9bba0eec94fd425fd5d5aadeb
Type fulltextMimetype application/pdf

Authority records BETA

Fjällman, Johan

Search in DiVA

By author/editor
Fjällman, Johan
By organisation
Fluid Physics
Fluid Mechanics and Acoustics

Search outside of DiVA

GoogleGoogle Scholar
Total: 2308 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 310 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