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Analysis of 3 Dimensional Turbine Flow by 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.
2014 (English)In: Proceedings of the ASME Turbo Expo, 2014, GT2014-26963- p.Conference paper, Published paper (Refereed)
Abstract [en]

 Today one of the most popular ways of lowering the fuel consumption and emissions of the Internal Combustion Engine (ICE) is by downsizing the engine. Downsizing means that the swept volumes of the cylinders are decreased; this lowers the frictional and thermal losses. By combining the downsizing with a well matched turbocharger system the performance is preserved while the advantages are retained. Since more and more of the development work is being performed by simulations there is an increasing need for more accurate methods. These methods are more complex and require more resources than the simpler, faster and more robust models used today. In this study Large Eddy Simulations (LES) of the unsteady flow in a radial turbine designed for a gasoline ICE has been performed and analysed. The flow inside the turbine is highly 3 dimensional, pulsating and characterized by secondary flow motions and high curvatures. All these are reasons for which the method of choice should be LES. LES is able to resolve a large range of scales and capture the flow dynamics. The considered case concerns a non-pulsating flow condition but with engine like mass flow and temperature. Post-processing tools based on Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) are used to analyse the large amount of LES based flow data. The POD method is used to investigate the energy content of the dominant, large structures present in the flow. The DMD method on the other hand is used to reveal the flow structures responsible for specific frequencies found in the flow field. Preliminary data show a fair agreement between experimental data and LES results in terms of predicting the turbine performance parameters.

Place, publisher, year, edition, pages
2014. GT2014-26963- p.
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-151390DOI: 10.1115/GT2014-26963ISI: 000361923800084Scopus ID: 2-s2.0-84922265228ISBN: 9780791845639 (print)OAI: oai:DiVA.org:kth-151390DiVA: diva2:748448
Conference
ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, GT 2014; Dusseldorf; Germany; 16 June 2014 through 20 June 2014
Note

QC 20140919

Available from: 2014-09-19 Created: 2014-09-19 Last updated: 2015-10-29Bibliographically 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

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Fjällman, JohanMihaescu, Mihai

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