Modern gas turbines are subjected to very high thermal loading. This leads to a need for aggressive cooling to protect components from damage. Endwalls are particularly challenging to cool due to a complex system of secondary flows near them that wash and disrupt the protective coolant films. This highly three-dimensional flow not only affects but is also affected by the momentum of film cooling flows, whether injected just upstream of the passage to intentionally cool the endwall, or as combustor cooling flows injected further upstream in the engine. This complex interaction between the different cooling flows and passage aerodynamics has been recently studied in a first stage nozzle guide vane. The present paper presents a detailed study on the sensitivity of aero-thermal interactions to endwall film cooling MFR (cooling mass flow to mainstream flow ratio). The test section represents a first stage nozzle guide vane with a contoured endwall and endwall film cooling injected just upstream of it. The test section also includes an engine-representative combustor-turbine interface geometry with combustor cooling flows injected at a constant rate. The approach flow conditions represent flow exiting a low-NOx combustor. Adiabatic surface thermal measurements and in-passage velocity and thermal field measurements are presented and discussed. The results show the dynamics of passage vortex suppression and the increase of impingement vortex strength as MFR changes. The effects of these changes of secondary flows on coolant distribution are presented.
|Original language||English (US)|
|Title of host publication||Heat Transfer|
|Publisher||American Society of Mechanical Engineers (ASME)|
|State||Published - 2020|
|Event||ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition, GT 2020 - Virtual, Online|
Duration: Sep 21 2020 → Sep 25 2020
|Name||Proceedings of the ASME Turbo Expo|
|Conference||ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition, GT 2020|
|Period||9/21/20 → 9/25/20|
Bibliographical noteFunding Information:
results in high mixing due to positive cross-pitch flows and a stronger passage vortex. Higher-MFR cases (e.g. MFR=2.5%) result in an overwhelming impingement vortex strength. This results in more than necessary coolant advection toward the pressure side, with lower coolant in the mid-pitch region and a strong pressure-side corner vortex. Also, strong impingent vortex is a source of dispersion. From these data, it can be confirmed that nozzle guide vane passage secondary flows, particularly the impingement vortex-passage vortex system are sensitive to endwall film cooling injection rates. The sensitivity of this system of secondary flows to various combustor cooling parameters, film cooling and cascade geometry (including endwall contouring) are topics for future work. ACKNOWLEDGEMENTS The authors would like to acknowledge Solar Turbines Incorporated for their financial support and would like to thank Alex Li for his assistance in the laboratory. REFERENCES  R. Sedney, and C. W. Jr. Kitchens, “The Structure of Three-Dimensional Separated Flows in Obstacle, Boundary Layer Interactions,” AGARD-CP-168 on Flow Separation, 1975.  R. J. Goldstein and J. Karni, “The Effect of a Wall Boundary Layer on Local Mass Transfer from a Cylinder in Crossflow,” Journal of Heat Transfer, vol. 106, no. 2, p. 260, May 1984.  L. S. Langston, M. L. Nice, and R. M. Hooper, “Three-Dimensional Flow Within a Turbine Cascade Passage,” J. Eng. Power, vol. 99, no. 1, p. 21, Jan. 1977.  H. P. Wang, S. J. Olson, R. J. Goldstein, and E. R. G. Eckert, “Flow Visualization in a Linear Turbine Cascade of High-Performance Turbine Blades,” J. Turbomach., vol. 119, no. 1, p. 1, Jan. 1997.  M. H. Alqefl, K. Nawathe, P. Chen, R. Zhu, Y. W. Kim, T. W. Simon, “Aero-Thermal Aspects of Film Cooled Nozzle Guide Vane Endwalls-Part I: Aerodynamics,” Proceedings of ASME Turbo Expo 2020, London, U.K., GT2020-15926  M. H. Alqefl, K. Nawathe, P. Chen, R. Zhu, Y. W. Kim, T. W. Simon, “Aero-Thermal Aspects of Film Cooled Nozzle Guide Vane Endwalls-Part II: Thermal Measurements,” GT2020-15076, Proceedings of ASME Turbo Expo 2020, London, U.K., GT2020-15076  M. F. Blair, “Experimental study of heat transfer and film cooling on large-scale turbine endwalls,” ASME Journal of Heat Transfer, 96:524–529, 1974.  L. J. Goldman, and K. L. McLallin, “Effects of Endwall Cooling on Secondary Flows in Turbine Stator Vanes,” AGARD, CPP-214, 1977.  R. P. Dring, M. F. Blair and H. D. Joselyn, “An Experimental Investigation of Film Cooling on a Turbine Rotor Blade”, Journal of Engineering for Power, vol. 102, p.81, Jan. 1980.  A. A. Thrift, K. A. Thole, and S. Hada, “Effects of Orientation and Position of the Combustor-Turbine Interface on the Cooling of a Vane Endwall,” J. Turbomach., vol. 134, no. 6, p. 061019, Nov. 2012.
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- Film Cooling
- Impingement Vortex
- Passage Vortex
- Secondary Flows
- Turbine Aerodynamics