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  • 1.
    Bradley, Andreas
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Utriainen, Esa
    Kinell, Mats
    Towards Efficient CFD-Simulations of Engine LikeTurbine Guide Vane Film Cooling2011Conference paper (Other academic)
    Abstract [en]

    It is well known that the efficiency of a gas turbine can be increased by using higher combustion temperatures and that this demands improved cooling. This study focuses on strategies to decrease the turnaround time for numerical predictions of film cooling while keeping the ability to resolve details of the flow. Simulations have been carried out for a real vane geometry at close to engine-like conditions and results are compared with corresponding experiments. The investigation includes an un-cooled situation for aerodynamic validation and to determine baseline heat transfer coefficent. Simulations and experiments of film effectiveness and heat transfer coefficient and their dependence of blowing ratio are investigated.

  • 2.
    Kinell, Mats
    et al.
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Barabas, Botond
    University of Duisburg-Essen, Duisburg, Germany.
    Comparison of Gas Turbine Vane Pressure Side and Suction Side Film Cooling Performance and the Applicability of Superposition2012In: In Proceedings of ASME, ASME Press, 2012, Vol. 4, p. 1479-1489Conference paper (Refereed)
    Abstract [en]

    In order to protect a solid surface exposed to high temperature gaseous flows, e.g. gas turbines and rocket engines, a second gas at lower temperature may be introduced into the hot boundary layer, i.e. one obtains a three temperature problem. The impact of the film cooling on a prototype vane due to variation in blowing ratio, the shape of the hole-outlet and position has been experimentally investigated. The semi-infinite and low conductive test object, initially at a uniform temperature, was exposed to a sudden step change in main flow temperature and a time-resolved surface temperature was measured using an IR camera. By assuming constant values of the heat transfer coefficient and the film cooling effectiveness over time, the heat equation was solved using least squares.

    The prototype vane was tested for different film cooling row positions on the pressure and suction side. Both cylindrical as well as fan shaped holes were investigated with and without showerhead cooling.

    The resulting heat transfer coefficient and film cooling effectiveness on the pressure side is compared to flat plate studies and to the results from the suction side. Also, the applicability of using superposition on showerhead cooling and on single/double rows is investigated. Furthermore, the results are compared to other published airfoil film cooling experiments and to CFD analysis for which conclusions are drawn on quantitative and qualitative capabilities of this tool.

  • 3.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    On Film Cooling of Turbine Guide Vanes: From Experiments and CFD-Simulations to Correlation Development2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To achieve high thermal efficiency in modern gas turbines, the turbine-inlet temperature has to be increased. In response to such requisites and to prevent thermal failure of the components exposed to hot gas streams, the use of different cooling techniques, including film cooling, is essential. Finding an optimum film cooling design has become a challenge as it is influenced by a large number of flow and geometrical parameters. This study is dedicated to some important aspects of film cooling of a turbine guide vane and consists of three parts.

    The first part is associated with an experimental investigation of the suction and pressure side cooling by means of a transient IR-Thermography technique under engine representative conditions. It is shown that the overall film cooling performance of the suction side can be improved by adding showerhead cooling if fan-shaped holes are used, while cylindrical holes may not necessarily benefit from a showerhead. According to the findings, investigation of an optimum cooling design for the suction side is not only a function of hole shape, blowing ratio, state of approaching flow, etc., but is also highly dependent on the presence/absence of showerhead cooling as well as the number of cooling rows. In this regard, it is also discussed that the combined effect of the adiabatic film effectiveness (AFE) and the heat transfer coefficient (HTC) should be considered in such study. As for the pressure side cooling, it is found that either the showerhead or a single row of cylindrical cooling holes can enhance the HTC substantially, whereas a combination of the two or using fan-shaped holes indicates considerably lower HTC. An important conclusion is that adding more than one cooling row will not augment the HTC and will even decrease it under certain circumstances.

    In the second part, computational fluid dynamics (CFD) investigations have shown that film cooling holes subjected to higher flow acceleration will maintain a higher level of AFE. Although this was found to be valid for both suction and pressure side, due to an overall lower acceleration for the pressure side, a lower AFE was achieved. Moreover, the CFD results indicate that fan-shaped holes with low area ratio (dictated by design constraints for medium-size gas turbines), suffer from cooling jet separation and hence reduction in AFE for blowing ratios above unity. Verification of these conclusions by experiments suggests that CFD can be used more extensively, e.g. for parametric studies.

    The last part deals with method development for deriving correlations based on experimental data to support engineers in the design stage. The proposed method and the ultimate correlation model could successfully correlate the laterally averaged AFE to the downstream distance, the blowing ratio and the local pressure coefficient representing the effect of approaching flow. The applicability of the method has been examined and the high level of predictability of the final model demonstrates its suitability to be used for design purposes in the future.

    List of papers
    1. Film Cooling Performance of a Turbine Vane Suction Side: The Showerhead Effect on Film Cooling Hole Placement for Cylindrical and Fan-Shaped Holes
    Open this publication in new window or tab >>Film Cooling Performance of a Turbine Vane Suction Side: The Showerhead Effect on Film Cooling Hole Placement for Cylindrical and Fan-Shaped Holes
    2015 (English)In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 137, no 9, article id 091005Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the transient IR-thermography method is used to investigate the effect of showerhead cooling on the film-cooling performance of the suction side of a turbine guide vane working under engine-representative conditions. The resulting adiabatic film effectiveness, heat transfer coefficient (HTC) augmentation, and net heat flux reduction (NHFR) due to insertion of rows of cooling holes at two different locations in the presence and absence of the showerhead cooling are presented. One row of cooling holes is located in the relatively high convex surface curvature region, while the other is situated closer to the maximum throat velocity. In the latter case, a double staggered row of fan-shaped cooling holes has been considered for cross-comparison with the single row at the same position. Both cylindrical and fan-shaped holes have been examined, where the characteristics of fan-shaped holes are based on design constraints for medium size gas turbines. The blowing rates tested are 0.6, 0.9, and 1.2 for single and double cooling rows, whereas the showerhead blowing is maintained at constant nominal blowing rate. The adiabatic film effectiveness results indicate that most noticable effects from the showerhead can be seen for the cooling row located on the higher convex surface curvature. This observation holds for both cylindrical and fan-shaped holes. These findings suggest that while the showerhead blowing does not have much impact on this cooling row from HTC enhancement perspective, it is influential in determination of the HTC augmentation for the cooling row close to the maximum throat velocity. The double-row fan-shaped cooling seems to be less affected by an upstream showerhead blowing when considering HTC enhancement, but it makes a major contribution in defining adiabatic film effectiveness. The NHFR results highlight the fact that cylindrical holes are not significantly affected by the showerhead cooling regardless of their position, but showerhead blowing can play an important role in determining the overall film-cooling performance of fan-shaped holes (for both the cooling row located on the higher convex surface curvature and the cooling row close to the maximum throat velocity), for both the single and the double row cases.

    Place, publisher, year, edition, pages
    ASME Press, 2015
    Keywords
    Film cooling, Showerhead cooling, Cylindrical holes, Fan-shaped holes, Gas Turbine
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-116936 (URN)10.1115/1.4029966 (DOI)000377794200005 ()
    Projects
    Turbo Power Program
    Note

    Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Sweden AB; Royal Institute of Technology through the Swedish research program TURBO POWER

    Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2017-12-04Bibliographically approved
    2. Film Cooling Performance of Multiple Arrays of Cylindrical and Fan-Shaped Holes
    Open this publication in new window or tab >>Film Cooling Performance of Multiple Arrays of Cylindrical and Fan-Shaped Holes
    Show others...
    2015 (English)In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 31, no 6, p. 1621-1630Article in journal (Refereed) Published
    Abstract [en]

    Experimental investigations are performed on the suction side of a cooled turbineguide vane. Transient IR thermography is used to evaluate film cooling performanceof cylindrical and fan-shaped holes in a test facility representing engine conditions.Adiabatic film effectiveness (AFE) and net heat flux reduction (NHFR) results due tocoolant injection through double and multiple rows in the presence and absence of anupstream showerhead are presented. Two double staggered rows at different positionshave been cross-compared; one at a relatively high convex curvature region and theother close to the maximum throat velocity. A combination of the two double rowsis considered to be multiple rows. The tested blowing ratios are in the interval of[0.6 – 1.2] and [0.3 – 1.2] for double and multiple rows, respectively. The showerheadcooling is maintained at nominal blowing ratio. The findings suggest that the choice ofbest cooling hole shape for film cooling design can be highly influenced by the numberof cooling rows to be used and also the presence (or absence) of showerhead cooling.It is worth noting that the outcome may differ depending on the quantity of interest, i.e. AFE or NHFR.

    Place, publisher, year, edition, pages
    American Institute of Aeronautics and Astronautics, 2015
    Keywords
    Film Cooling, Gas Turbine, Film Effectiveness, Net Heat Flux Reduction, Cylindrical Holes, Fan-shaped Holes
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-117030 (URN)10.2514/1.B35618 (DOI)000368248000011 ()
    Projects
    Turbo Power Program
    Note

    Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery, AB; GKN Aerospace Sweden, AB; Royal Institute of Technology through the Swedish research program TURBO POWER

    Vid tiden för disputationen förelåg publikationen endast som manuskript

    Available from: 2015-04-11 Created: 2015-04-11 Last updated: 2017-12-04Bibliographically approved
    3. Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane
    Open this publication in new window or tab >>Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane
    2014 (English)In: ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, American Society of Mechanical Engineers , 2014, Vol. 5B, p. Paper No. GT2014-26055-Conference paper, Published paper (Refereed)
    Abstract [en]

    Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge.

    The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

    Place, publisher, year, edition, pages
    American Society of Mechanical Engineers, 2014
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-111022 (URN)10.1115/GT2014-26055 (DOI)000362139100038 ()978-0-7918-4572-1 (ISBN)
    Conference
    ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, Düsseldorf, Germany, June 16–20, 2014
    Available from: 2014-10-03 Created: 2014-10-03 Last updated: 2016-03-14Bibliographically approved
    4. CFD Based Sensitivity Analysis of Influencing Flow Parameters for Cylindrical and Shaped Holes in a Gas Turbine Vane
    Open this publication in new window or tab >>CFD Based Sensitivity Analysis of Influencing Flow Parameters for Cylindrical and Shaped Holes in a Gas Turbine Vane
    2012 (English)In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, Volume 4: Heat Transfer, Parts A and B Copenhagen, Denmark, June 11–15, 2012, ASME Press, 2012, Vol. 4, p. 1501-1509Conference paper, Published paper (Refereed)
    Abstract [en]

    In this study a CFD based sensitivity analysis is performedincluding the flow parameter blowing ratio, the geometrical parametercooling hole shape and the effect of approaching flow(hole position), investigating the film cooling performance of areal vane configuration working at engine like conditions. Forthis purpose numerical results from the commercial CFD codeFLUENT using the Spalart-Allmaras turbulence model has beenvalidated versus experimental results on the same vane includingthe film cooling hole configurations. Blowing ratios ranging from(0.2-1.8) have been considered. In addition, film cooling performanceof rows of cooling holes at six different positions locatedaround the suction and pressure side of the vane are investigatedfor studying the influence of flow acceleration present in turbinevanes. These flow parameters are investigated for both cylindricaland fan-shaped holes. Investigations are performed at afixed unity density ratio. It has been found that for fan-shapedholes film cooling performance is higher for cooling holes locatedat positions whit a high accelerated flow. On the otherhand, film cooling performance of cylindrical holes are found tobe affected less by acceleration. Due to the low velocity and lowacceleration on the pressure side the hole position seems to haverelatively low influence on the cooling performance.

    Place, publisher, year, edition, pages
    ASME Press, 2012
    Keywords
    Computational Fluid Dynamics, Film Cooling, Fan-shaped Holes, Cylindrical Holes
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-116938 (URN)10.1115/GT2012-69023 (DOI)978-0-7918-4470-0 (ISBN)
    Conference
    ASME Turbo Expo 2012, June 11-12, Copenhagen, Denmark
    Projects
    Turbo Power Program
    Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2016-03-14Bibliographically approved
    5. Film Effectiveness Correlations for Cylindrical and Fan-Shaped Holes, Introducing Local Pressure Coefficient
    Open this publication in new window or tab >>Film Effectiveness Correlations for Cylindrical and Fan-Shaped Holes, Introducing Local Pressure Coefficient
    2012 (English)In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, Volume 4: Heat Transfer, Parts A and B, Copenhagen, Denmark, June 11–15, 2012, ASME Press, 2012, Vol. 4, p. 1491-1500Conference paper, Published paper (Refereed)
    Abstract [en]

    Most of the proposed correlations for prediction of gas turbinefilm cooling performance in the open literature rely on experimentsconducted on flat plates. These correlations neglectadverse pressure gradient effects present in the flow field for airfoillike configurations. The continuous change in flow characteristicsin the main flow field from leading edge to trailingedge that will affect the film cooling performance is also neglected.In this study correlations are derived from measurementsconducted on a gas turbine vane working at engine likeconditions. This will take into account the effect of hole positionand the local flow situation. Indeed, cooling holes locatedat three (five) different positions with blowing ratio ranges from0.3-2.5 (0.9-6) have been considered along the suction (pressure)sides. The non-dimensional pressure coefficient CP, at the exitlocation of each hole has been introduced as a new variable toderive a single correlation for either suction or pressure sides.Three main variables: downstream distance, blowing ratio, andlocal CP together with the two way interaction between thesevariables are introduced into a commercial statistical analysisprogram, Minitab. Stepwise regression analysis has been performedto highlight factors with greatest influence on the correlationmodel. Appropriateness of the derived model is measuredbased on the adjusted coefficient of determination, R2ad j. Correlationsare derived for eight different configurations: for suctionand pressure sides, cylindrical and fan-shaped holes and in thepresence and absence of showerhead cooling. Despite the complexity of the flow due to high blowing ratio (existence of lift off)and also variation of film cooling performance from one positionto another, the calculated R2adj values indicate a high predictabilityof the proposed correlation model. The suggested correlationmodel can be useful for optimizing the location of one or severalrows of cooling holes around the vane and also one single rowperformance.

    Place, publisher, year, edition, pages
    ASME Press, 2012
    Keywords
    Film Cooling, Gas Turbine, Film effectiveness, Correlation, Fan-shaped Holes, Cylindrical Holes
    National Category
    Fluid Mechanics and Acoustics
    Identifiers
    urn:nbn:se:liu:diva-116987 (URN)10.1115/GT2012-69021 (DOI)000335868900132 ()978-0-7918-4470-0 (ISBN)
    Conference
    ASME Turbo Expo 2012, June 11–15, Copenhagen, Denmark
    Projects
    Turbo Power Program
    Available from: 2015-04-10 Created: 2015-04-10 Last updated: 2017-03-07Bibliographically approved
  • 4.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Bradley, Andreas
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Wren, Joakim
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Kinell, Mats
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    CFD Simulations Using Reduced Models for Film Cooling Design2011In: 49th AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2011, American Institute of Aeronautics and Astronautics, 2011, p. AiAA 2011-710-Conference paper (Other academic)
    Abstract [en]

    Film cooling technologies are widely used for attaining high efficiency in gas turbine engines. In this study we have investigated the potential for reduced models to capture different aspects of film cooling by means of CFD at low turn-around time while maintaining the accuracy at a reasonable level. CFD simulations and experiments were carried out for an engine-like setting. Subsequently, the computational domain was reduced in two steps in order to decrease the simulation time. Results for all models are compared with experimental data, including aerodynamic validation, heat transfer coefficient and film effectiveness. The aerodynamic results are very similar for experiments and simulations, and the heat transfer coefficient and film cooling effectiveness showed similarities within the expected range. Thus, this strategy could be very useful for e.g. early vane and film cooling design.

  • 5.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Kinell, Mats
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB, Finspång, Sweden.
    Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane2014In: ASME Turbo Expo 2014: Turbine Technical Conference and Exposition, American Society of Mechanical Engineers , 2014, Vol. 5B, p. Paper No. GT2014-26055-Conference paper (Refereed)
    Abstract [en]

    Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge.

    The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

  • 6.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Kinell, Mats
    Siemens Industrial Turbomachinery AB.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB.
    Film Cooling Performance of a Turbine Vane Suction Side: The Showerhead Effect on Film Cooling Hole Placement for Cylindrical and Fan-Shaped Holes2015In: Journal of turbomachinery, ISSN 0889-504X, E-ISSN 1528-8900, Vol. 137, no 9, article id 091005Article in journal (Refereed)
    Abstract [en]

    In this paper, the transient IR-thermography method is used to investigate the effect of showerhead cooling on the film-cooling performance of the suction side of a turbine guide vane working under engine-representative conditions. The resulting adiabatic film effectiveness, heat transfer coefficient (HTC) augmentation, and net heat flux reduction (NHFR) due to insertion of rows of cooling holes at two different locations in the presence and absence of the showerhead cooling are presented. One row of cooling holes is located in the relatively high convex surface curvature region, while the other is situated closer to the maximum throat velocity. In the latter case, a double staggered row of fan-shaped cooling holes has been considered for cross-comparison with the single row at the same position. Both cylindrical and fan-shaped holes have been examined, where the characteristics of fan-shaped holes are based on design constraints for medium size gas turbines. The blowing rates tested are 0.6, 0.9, and 1.2 for single and double cooling rows, whereas the showerhead blowing is maintained at constant nominal blowing rate. The adiabatic film effectiveness results indicate that most noticable effects from the showerhead can be seen for the cooling row located on the higher convex surface curvature. This observation holds for both cylindrical and fan-shaped holes. These findings suggest that while the showerhead blowing does not have much impact on this cooling row from HTC enhancement perspective, it is influential in determination of the HTC augmentation for the cooling row close to the maximum throat velocity. The double-row fan-shaped cooling seems to be less affected by an upstream showerhead blowing when considering HTC enhancement, but it makes a major contribution in defining adiabatic film effectiveness. The NHFR results highlight the fact that cylindrical holes are not significantly affected by the showerhead cooling regardless of their position, but showerhead blowing can play an important role in determining the overall film-cooling performance of fan-shaped holes (for both the cooling row located on the higher convex surface curvature and the cooling row close to the maximum throat velocity), for both the single and the double row cases.

  • 7.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Kinell, Mats
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB, Finspong, Sweden.
    Film Effectiveness Correlations for Cylindrical and Fan-Shaped Holes, Introducing Local Pressure Coefficient2012In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, Volume 4: Heat Transfer, Parts A and B, Copenhagen, Denmark, June 11–15, 2012, ASME Press, 2012, Vol. 4, p. 1491-1500Conference paper (Refereed)
    Abstract [en]

    Most of the proposed correlations for prediction of gas turbinefilm cooling performance in the open literature rely on experimentsconducted on flat plates. These correlations neglectadverse pressure gradient effects present in the flow field for airfoillike configurations. The continuous change in flow characteristicsin the main flow field from leading edge to trailingedge that will affect the film cooling performance is also neglected.In this study correlations are derived from measurementsconducted on a gas turbine vane working at engine likeconditions. This will take into account the effect of hole positionand the local flow situation. Indeed, cooling holes locatedat three (five) different positions with blowing ratio ranges from0.3-2.5 (0.9-6) have been considered along the suction (pressure)sides. The non-dimensional pressure coefficient CP, at the exitlocation of each hole has been introduced as a new variable toderive a single correlation for either suction or pressure sides.Three main variables: downstream distance, blowing ratio, andlocal CP together with the two way interaction between thesevariables are introduced into a commercial statistical analysisprogram, Minitab. Stepwise regression analysis has been performedto highlight factors with greatest influence on the correlationmodel. Appropriateness of the derived model is measuredbased on the adjusted coefficient of determination, R2ad j. Correlationsare derived for eight different configurations: for suctionand pressure sides, cylindrical and fan-shaped holes and in thepresence and absence of showerhead cooling. Despite the complexity of the flow due to high blowing ratio (existence of lift off)and also variation of film cooling performance from one positionto another, the calculated R2adj values indicate a high predictabilityof the proposed correlation model. The suggested correlationmodel can be useful for optimizing the location of one or severalrows of cooling holes around the vane and also one single rowperformance.

  • 8.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB.
    Kinell, Mats
    Siemens Industrial Turbomachinery AB.
    CFD Based Sensitivity Analysis of Influencing Flow Parameters for Cylindrical and Shaped Holes in a Gas Turbine Vane2012In: ASME Turbo Expo 2012: Turbine Technical Conference and Exposition, Volume 4: Heat Transfer, Parts A and B Copenhagen, Denmark, June 11–15, 2012, ASME Press, 2012, Vol. 4, p. 1501-1509Conference paper (Refereed)
    Abstract [en]

    In this study a CFD based sensitivity analysis is performedincluding the flow parameter blowing ratio, the geometrical parametercooling hole shape and the effect of approaching flow(hole position), investigating the film cooling performance of areal vane configuration working at engine like conditions. Forthis purpose numerical results from the commercial CFD codeFLUENT using the Spalart-Allmaras turbulence model has beenvalidated versus experimental results on the same vane includingthe film cooling hole configurations. Blowing ratios ranging from(0.2-1.8) have been considered. In addition, film cooling performanceof rows of cooling holes at six different positions locatedaround the suction and pressure side of the vane are investigatedfor studying the influence of flow acceleration present in turbinevanes. These flow parameters are investigated for both cylindricaland fan-shaped holes. Investigations are performed at afixed unity density ratio. It has been found that for fan-shapedholes film cooling performance is higher for cooling holes locatedat positions whit a high accelerated flow. On the otherhand, film cooling performance of cylindrical holes are found tobe affected less by acceleration. Due to the low velocity and lowacceleration on the pressure side the hole position seems to haverelatively low influence on the cooling performance.

  • 9.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Utriainen, Esa
    Kinell, Mats
    Multi-variable Correlation for Cylindrical Holes at Suction and Pressure sides of A Turbine Vane2012Conference paper (Other academic)
    Abstract [en]

    Reliable correlations for predicting film cooling performance is one of the major considerations in the cooling analysis of today's gas turbine engines. In this study correlations have been derived for cylindrical holes positioned at three different positions on both the suction and pressure sides of a vane configuration at engine like settings. The blowing ratio ranges between 0.3-2.2 for the suction side and 0.9-6.55 for the pressure side. The density ratio is one. The correlation model derived here is inspired from Bunker with modifications in definition of the variables and adding extra terms. The extra terms obtained from the main variables are introduced into a stepwise regression method (statistical analysis) to find predictors with the highest contribution percentage. These variables are then utilized in the correlation for increasing model predictability. The proposed correlation is compared with existing correlations in terms of adjusted coefficient of determination R2 adj , where significant improvement is obtained. The applicability of the model to shaped holes is also discussed. Copyright © 2012 American Institute of Aeronautics and Astronautics, Inc.

  • 10.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Utriainen, Esa
    Kinell, Mats
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    A Modified Correlation for Film Effectiveness Prediction of Cylindrical Holes at the Suction Side of A turbine Guide Vane2011In: Proceedings of the 6th Baltic Heat Transfer Conference, Tampere Convention Bureau , 2011Conference paper (Other academic)
  • 11.
    Nadali Najafabadi, Hossein
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Utriainen, Esa
    Siemens Industrial Turbomachinery AB, Sweden.
    Kinell, Mats
    Siemens Industrial Turbomachinery AB, Sweden.
    Wang, Lieke
    Siemens Industrial Turbomachinery AB, Sweden.
    Film Cooling Performance of Multiple Arrays of Cylindrical and Fan-Shaped Holes2015In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 31, no 6, p. 1621-1630Article in journal (Refereed)
    Abstract [en]

    Experimental investigations are performed on the suction side of a cooled turbineguide vane. Transient IR thermography is used to evaluate film cooling performanceof cylindrical and fan-shaped holes in a test facility representing engine conditions.Adiabatic film effectiveness (AFE) and net heat flux reduction (NHFR) results due tocoolant injection through double and multiple rows in the presence and absence of anupstream showerhead are presented. Two double staggered rows at different positionshave been cross-compared; one at a relatively high convex curvature region and theother close to the maximum throat velocity. A combination of the two double rowsis considered to be multiple rows. The tested blowing ratios are in the interval of[0.6 – 1.2] and [0.3 – 1.2] for double and multiple rows, respectively. The showerheadcooling is maintained at nominal blowing ratio. The findings suggest that the choice ofbest cooling hole shape for film cooling design can be highly influenced by the numberof cooling rows to be used and also the presence (or absence) of showerhead cooling.It is worth noting that the outcome may differ depending on the quantity of interest, i.e. AFE or NHFR.

  • 12.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Ghavami Nejad, Mehdi
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Loyd, Dan
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Skoog, Pontus
    SAPA Heat Transfer AB.
    Abrahamsson, David
    SAPA Heat Transfer AB.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Conduction and convection heat transfer for aluminum ingot in preheating furnace2011In: Proceedings of 6th Baltic Heat Transfer Conference 2011 / [ed] Reijo Karvinen & Matti Lindstedt, 2011Conference paper (Refereed)
    Abstract [en]

    Aluminium is a widely used material, which is found in a number of products e.g. thin aluminium bands that is the base material in many heat exchangers. Rolling processes are used to produce these thin aluminium bands, in order to get the right properties and to get the aluminium easier to roll, heat treatment is needed. This heat treatment of aluminium ingots prior to the rolling is in focus in this work, where computational fluid dynamics and computational heat transfer techniques is used to predict the heating process in a hot air pre-heating furnace. The used approach includes steady state computational fluid dynamics simulations combined with transient computational heat transfer simulations. The simulation results in form of spatial and temporal distributed aluminium ingot temperature was compared with temperature measurement in a thermocouple prepared ingot in the actual pre-heating furnace. Simulation results correspond well with the measurements and there are small differences. Results of the described simulation approach open the possibility to predict spatial and temporal temperature distribution in these kinds of pre-heating processes.

  • 13.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Thoracic and Vascular Surgery. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Subject-specific aortic wall shear stress estimations using semi-automatic segmentation2012In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 6, p. 481-491Article in journal (Refereed)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such an entity in-vivo in humans, image-based computational fluid dynamics (CFD) is a useful tool. In this study, we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method, a number of steps are included. One important step is the interpretation of images into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparing WSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of eight healthy male volunteers. The different segmentation methods give slightly different geometrical depictions of the human aorta (difference in the mean thoracic Aorta lumen diameter were 0.7% Pandlt;0.86). However, there is a very good agreement between the resulting WSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time point indicating that the WSS is more sensitive to local geometric differences in these parts of the cardiac cycle (correlation coefficient is 0.96 at peak systole and 0.68 at early diastole). We can conclude that the results show that the semi-automatic segmentation method can be used in future to estimate relevant aortic WSS.

  • 14.
    Renner, Johan
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
    Modin, Daniel
    Linköping University, Department of Medicine and Health Sciences. Linköping University, Faculty of Health Sciences.
    Länne, Toste
    Linköping University, Department of Medicine and Health Sciences, Physiology. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Thoracic and Vascular Surgery in Östergötland.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    Wall Shear Stress Estimations using Semi-Automatic SegmentationManuscript (preprint) (Other academic)
    Abstract [en]

    Atherosclerosis development is strongly believed to be influenced by hemodynamic forces such as wall shear stress (WSS). To estimate such entity in-vivo in humans, is image based computational fluid dynamics (CFD) a powerful tool. In this paper we use a combination of magnetic resonance imaging (MRI) and CFD to estimate WSS. In such method a number of steps is included. One important step is the image interpretation into 3D models, named segmentation. The choice of segmentation method can influence the resulting WSS distribution in the human aorta. This is studied by comparingWSS results gained from the use of two different segmentation approaches: manual and semi-automatic, where the manual approach is considered to be the reference method. The investigation is performed on a group of 8 healthymale volunteers. The different segmentation methods give slightly different geometrical descriptions of the human aorta. However there is a very good agreement between the resultingWSS distribution for the two segmentation approaches. The small differences in WSS between the methods increase in the late systole and early diastolic cardiac cycle time position indicating that theWSS is more sensitive to local geometry differences in these parts of the cardiac cycle. We can conclude that the results show that the semi-automatic segmentation method can be used in the future to estimate WSS with relevant accuracy.

  • 15.
    Schminder, Jörg
    et al.
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Gårdhagen, Roland
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Learning by teaching: Student developed material for self-directed studies2016In: The 12th International CDIO Conference: Proceedings - Full Papers, Turku: Turku University of Applied Sciences , 2016, p. 750-759Conference paper (Refereed)
    Abstract [en]

    The objective of the presented paper is to demonstrate how e-learning course material developed by the students can enhance active learning for self-directed studies outside the classroom in a flipped classroom concept. A method which merges different learning activities such as learning by teaching, video based teaching etc. was developed to improve the students’ personal and interpersonal engineering skills in relation to CDIO standards. In an effort to assess the students’ satisfaction and practical use of the students’ created material, a survey was conducted. Statistics, the students’ feedback, and observations show an increase in learning motivation, deepened understanding, and expanded communication skills.

  • 16.
    Wang, Lieke
    et al.
    Siemens Ind Turbomachinery AB, Sweden.
    Kinell, Mats
    Siemens Ind Turbomachinery AB, Sweden.
    Nadali Najafabadi, Hossein
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    Karlsson, Matts
    Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, Faculty of Science & Engineering.
    A THREE-REGIME BASED METHOD FOR CORRELATING FILM COOLING EFFECTIVENESS FOR CYLINDRICAL AND SHAPED HOLES2015In: ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2015, VOL 5B, AMER SOC MECHANICAL ENGINEERS , 2015, no UNSP V05BT12A004Conference paper (Refereed)
    Abstract [en]

    To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

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