Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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
Aerodynamic Investigations of a High Pressure Turbine Vane with Leading Edge Contouring at Endwall in a Transonic Annular Sector Cascade
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.ORCID iD: 0000-0001-5162-2289
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Efficiency improvement is an important aspect to reduce the use of fossil-based fuel in order to achieve a sustainable future. Gas turbines are mainly fossil-fuel based turbomachines, and, therefore, efficiency improvement is still the subject of many on-going research activities in the gas turbine community. This study is incorporated into a research project that investigates design possibilities of efficiency improvement at the high pressure turbine (HPT) stage.

In the search for HPT-stage efficiency gains, leading edge (LE) contouring near the endwall is one of the methods found in the published literature that has shown a potential to increase the efficiency by decreasing the amount of secondary losses. The overall objective of the thesis is to contribute to the development of gas turbine efficiency improvements in relation to the HPT stage. Particularly, the influence of the LE fillet on losses and flow structure is investigated concentrating on the secondary flow. The core investigation is of an experimental nature. Detailed investigations of the flow field in an annular sector cascade (ASC) are presented with and without the LE fillet, using a geometric replica of a modern gas turbine nozzle guide vane (NGV) with a contoured tip endwall. Furthermore, a separate investigation is performed on a hub-cooled NGV, which focuses on endwalls, specifically the interaction between the hub film cooling and the mainstream (MS).

The experimental investigations indicate that the LE fillet has no significant effect on the flow and energy losses of the investigated NGV. The reason why the LE fillet does not affect the losses might be due to the use of a three-dimensional vane with an existing typical fillet over the full hub and tip profile. Findings also reveal that the complex secondary flow depends heavily on the incoming boundary layer. Oil flow visualisation for the baseline case displays a clear saddle point, with a separation line where the horseshoe (HS) vortex separates into the suction side (SS) and the pressure side (PS), whereas for the filleted case, the saddle point is not noticeable. The investigation of a cooled vane, using a tracer gas carbon dioxide (CO2), reveals that the upstream platform film coolant is concentrated along the SS surfaces and does not reach the PS of the hub surface, leaving it less protected from the hot gas.

Abstract [sv]

För att åstadkomma en uthållig kraftproduktion i framtiden och en minskning i användandet av fossila bränslen är effektivitetsförbättringar av central betydelse. Gasturbiner är i grund och botten fossilbaserade turbomaskiner och därför bedrivs forsknings- och utvecklingsarbete kring verkningsgradsförbättringar. Den här studien ingår i ett forskningsprojekt som undersöker designmodifieringar med målet att höja verkningsgraden för ett högtrycksturbinsteg.

Förändringar av bladets eller ledskenans framkantsgeometri nära ändväggarna har i den öppna litteraturen funnits vara en lovande metod för att minska ändväggsförlusterna. Det övergripande målet med denna studie är att bidra till utvecklingen av effektiva högtrycksturbinsteg för gasturbiner. Kärnan i undersökningen är experimentell. Särskilt påverkan från förändring av framkanten på förluster och flödesstruktur undersöks, med fokus på det sekundära flödet. Detaljerade strömningsundersökningar i ett bågformat statorgitter bestående av en geometrisk replika av en stator från en modern gasturbin presenteras, med och utan geometrisk förändring av framkanten. Vidare så genomförs en separat undersökning av en filmkyld ledskena utan framkantsförändring med fokus på interaktionen mellan filmkylningen vid inre ändväggen och huvudflödet.

De experimentella undersökningarna visar att den undersökta geometriska förändringen av framkanten inte är av signifikant betydelse för strömningsförlusterna med den studerade ledskenan. Anledningen till att designförändringen inte påverkar förlusterna kan bero på användandet av en tredimensionell ledskena med en existerande typisk kärlradie mellan ledskenan och ändväggarna. Observationerna visar också att den komplexa ändväggsströmningen är starkt beroende av det inkommande gränsskiktets egenskaper. Oljevisualisering för referensledskenan visar en tydlig stagnationspunkt på ändväggen där gränsskiktet delas upp likt en hästskoformation i virvlar på sug- respektive trycksidan av ledskenan. För den modifierade framkanten har ingen tydlig stagnationspunkt på ändväggen observerats. Spårgasundersökningar med den filmkylda ledskenan visar att filmkylningen på den inre plattformen är koncentrerad längs sugsidan och når inte trycksidan på plattformen som därmed är mindre skyddad mot den varma gasströmningen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xx, 93 p.
Series
Trita KRV Report, ISSN 1100-7990 ; 12/02
Keyword [en]
high pressure turbine, secondary flow, leading edge contouring, endwall, experimental investigations, losses, flow field, hub cooling flow
Keyword [sv]
högtrycksturbinen sekundärströmning, framkantsmodifiering, ändvägg, experimentell undersökning, förluster, strömningsfält, filmkylning av inre platform
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:kth:diva-92204ISBN: 978-91-7501-293-3 (print)OAI: oai:DiVA.org:kth-92204DiVA: diva2:512682
Presentation
2012-04-13, M3, Brinellvägen 64, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120330Available from: 2012-03-30 Created: 2012-03-28 Last updated: 2012-04-17Bibliographically approved
List of papers
1. Experimental studies of leading edge contouring influence on secondary losses in transonic turbines
Open this publication in new window or tab >>Experimental studies of leading edge contouring influence on secondary losses in transonic turbines
Show others...
2012 (English)In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, ASME Press, 2012, 1109-1119 p.Conference paper, Published paper (Refereed)
Abstract [en]

An experimental study of the hub leading edge contouring using fillets is performed in an annular sector cascade to observe the influence of secondary flows and aerodynamic losses. The investigated vane is a three dimensional gas turbine guide vane (geometrically similar) with a mid-span aspect ratio of 0.46. The measurements are carried out on the leading edge fillet and baseline cases using pneumatic probes. Significant precautions have been taken to increase the accuracy of the measurements. The investigations are performed for a wide range of operating exit Mach numbers from 0.5 to 0.9 at a design inlet flow angle of 90°. Data presented include the loading, fields of total pressures, exit flow angles, radial flow angles, as well as profile and secondary losses. The vane has a small profile loss of approximately 2.5 % and secondary loss of about 1.1%. Contour plots of vorticity distributions and velocity vectors indicate there is a small influence of the vortex-structure in endwall regions when the leading edge fillet is used. Compared to the baseline case the loss for the filleted case is lower up to 13 % of span and higher from 13% to 20 % of the span for a reference condition with Mach no. of 0.9. For the filleted case, there is a small increase of turning up to 15 % of the span and then a small decrease up to 35 % of the span. Hence, there are no significant influences on the losses and turning for the filleted case. Results lead to the conclusion that one cannot expect a noticeable effect of leading edge contouring on the aerodynamic efficiency for the investigated 1st stage vane of a modern gas turbine.

Place, publisher, year, edition, pages
ASME Press, 2012
Series
Proceedings of the ASME Turbo Expo, 8
Keyword
Aerodynamic efficiency, Aerodynamic loss, Experimental studies, Reference condition, Transonic turbine, Turbine guide vane, Velocity vectors, Vorticity distribution
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-92183 (URN)10.1115/GT2012-68497 (DOI)000335720900101 ()2-s2.0-84881178157 (Scopus ID)978-079184474-8 (ISBN)
Conference
ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, GT 2012; Copenhagen; Denmark; 11 June 2012 through 15 June 2012
Note

QC 20130115

Available from: 2012-03-28 Created: 2012-03-28 Last updated: 2014-10-09Bibliographically approved
2. Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade
Open this publication in new window or tab >>Measurements of Hub Flow Interaction on Film Cooled Nozzle Guide Vane in Transonic Annular Cascade
2012 (English)In: Proceedings of the ASME Turbo Expo, ASME Press, 2012Conference paper, Published paper (Refereed)
Abstract [en]

An experimental study has been performed in a transonic annular sector cascade of nozzle guide vanes to investigate the aerodynamic performance and the interaction between hub film cooling and mainstream flow. The focus of the study is on the endwalls, specifically the interaction between the hub film cooling and the mainstream. Carbon dioxide (CO2) has been supplied to the coolant holes to serve as tracer gas. Measurements of CO2 concentration downstream of the vane trailing edge can be used to visualize the mixing of the coolant flow with the mainstream.

Flow field measurements are performed in the downstream plane with a 5-hole probe to characterize the aerodynamics in the vane. Results are presented for the fully cooled and partially cooled vane (only hub cooling) configurations. Data presented at the downstream plane include concentration contour, axial vorticity, velocity vectors, and yaw and pitch angles. From these investigations, secondary flow structures such as the horseshoe vortex, passage vortex, can be identified and show the cooling flow significantly impacts the secondary flow and downstream flow field. The results suggest that there is a region on the pressure side of the vane trailing edge where the coolant concentrations are very low suggesting that the cooling air introduced at the platform upstream of the leading edge does not reach the pressure side endwall, potentially creating a local hotspot.

Place, publisher, year, edition, pages
ASME Press, 2012
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-92186 (URN)10.1115/GT2012-68088 (DOI)2-s2.0-84881132398 (Scopus ID)978-079184474-8 (ISBN)
Conference
ASME Turbo Expo 2012 - Turbine Technical Conference and Exposition, Copenhagen, June 11-15, 2012
Note

QC 20150706

Available from: 2012-03-28 Created: 2012-03-28 Last updated: 2015-07-06Bibliographically approved
3. Influence of pre-history and leading edge contouring on aero-performance of a 3D nozzle guide vane
Open this publication in new window or tab >>Influence of pre-history and leading edge contouring on aero-performance of a 3D nozzle guide vane
Show others...
2013 (English)In: Proceedings of the ASME Gas Turbine India Conference -2013- ; presented at ASME 2013 Gas Turbine India Conference, December 5-6, 2013, Bangalore, India, ASME Press, 2013Conference paper, Published paper (Refereed)
Abstract [en]

Experiments are conducted to investigate the effect of the pre-history in the aerodynamic performance of a threedimensional nozzle guide vane with a hub leading edge contouring. The performance is determined with two pneumatic probes (5 hole and 3 hole) concentrating mainly on the endwall. The investigated vane is a geometrically similar gas turbine vane for the first stage with a reference exit Mach number of 0.9. Results are compared for the baseline and filleted cases for a wide range of operating exit Mach numbers from 0.5 to 0.9. The presented data includes loading distributions, loss distributions, fields of exit flow angles, velocity vector and vorticity contour, as well as, mass-averaged loss coefficients. The results show an insignificant influence of the leading edge fillet on the performance of the vane. However, the pre-history (inlet condition) affects significantly in the secondary loss. Additionally, an oil visualization technique yields information about the streamlines on the solid vane surface which allows identifying the locations of secondary flow vortices, stagnation line and saddle point.

Place, publisher, year, edition, pages
ASME Press, 2013
Keyword
Aero-dynamic performance, Gas turbine vanes, Loading distribution, Loss coefficients, Loss distribution, Nozzle guide vanes, Three-dimensional nozzles, Visualization technique, Aerodynamics, Gas turbines, Mach number, Nozzles
National Category
Energy Engineering
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-92190 (URN)000349928500021 ()2-s2.0-84896678919 (Scopus ID)
Conference
ASME 2013 Gas Turbine India Conference, GTINDIA 2013; Bangalore, Karnataka; India; 5 December 2013 through 6 December 2013
Note

QC 20140625

Available from: 2012-03-28 Created: 2012-03-28 Last updated: 2017-11-29Bibliographically approved

Open Access in DiVA

Saha_TekLic(4503 kB)2306 downloads
File information
File name FULLTEXT01.pdfFile size 4503 kBChecksum SHA-512
61383c0acffa9dff1a3a99a1794f35b4fbe335ad0e7c46af93bea34dae6cd6173575a403fb3a40dbfc0d2c6cfe3bd54670975d4a101a251568537e9d24b97e30
Type fulltextMimetype application/pdf
errata(127 kB)195 downloads
File information
File name ERRATA01.pdfFile size 127 kBChecksum SHA-512
283ccfea7ff256c0119908130b1d331a3aa47493ba736065e0e6d1797873a0f9b77f8568a4ce2154b4b232052447b47d5fd33e6f7aee758df180a4b40c845ca5
Type errataMimetype application/pdf

Search in DiVA

By author/editor
Saha, Ranjan
By organisation
Heat and Power Technology
Energy Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 2306 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

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 1075 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • 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