Numerical Investigation of Vortex Structures in the Rim Cavities of Gas Turbines


Authors : Ulvi Fatullayev

Volume/Issue : Volume 10 - 2025, Issue 6 - June

Google Scholar : https://tinyurl.com/3kvwb9c8

DOI : https://doi.org/10.38124/ijisrt/25jun048

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Abstract : This study presents a computational investigation of vortex structures forming within the rim cavities of gas turbines. Utilizing computational fluid dynamics (CFD), both steady-state and transient simulations were conducted on simplified cavity models derived from a 1.5-stage experimental turbine. A range of cavity widths and boundary conditions, including surface-averaged and profile-based inlets and outlets, were explored. The emergence of large-scale rotating structures and Kelvin-Helmholtz instabilities was evaluated under varying non-dimensional purge flow rates at a low non- dimensional purge flow rate. Time-resolved simulations showed the importance of realistic profile boundary conditions in capturing the unsteady flow phenomena. The analysis confirmed the sensitivity of vortex formation to geometric and flow conditions, particularly the boundary specification and purge flow magnitude. Transient simulations using profile inlet velocity and outlet pressure distributions yielded results closely matching experimental observations. These findings contribute to optimizing secondary air systems and improving turbine cooling efficiency while reducing unnecessary purge air usage.

Keywords : Gas Turbines, Rim Cavity, CFD, Vortex Structures, Hot Gas Ingestion, Purge Flow, Kelvin-Helmholts Instabilities.

References :

  1. Rolls-Royce: The Jet Engine, ISBN 0-902121-04-9
  2. Cao, C., Chew, J.W., Millington: “Interaction of Rim Seal and Annulus Flow in an Axial Flow Turbine J. of Eng. for Gas Turbines and Power”, 126(4),October, pp.786-793.
  3. Jakoby, R., Zierer, T., Lindblad, K., Larsson, J., deVito, L., Bohn, D.E., Funcke, J., and Decker: “Numerical Simulation of the Unsteady Flow Field in an Axial Gas Turbine Rim Seal Configuration” ASME Paper GT2004-53829.
  4. Steve Julien, Julie Lefrancois, Guy Dumas,Guillaume Boutet-Blais, Simon Lapointe: “Simulations of flow ingestion and related structures in a turbine disc cavity”
  5. M.Rabs, F.-K. Benra, H. J. Dohmen . “Investigation of the flow instabilities near the rim cavity of a 1.5 stage gas turbines” ASME Paper GT2009-59965
  6. Lars Ellermann: Studienarbeit, “Numerische Untersuchung der rotierenden Niedrigdruckfeldern in Radseitenräumen von Gasturbinen”
  7. Hills, N.J., Chew, J.W. and Turner: “Computational and mathematical modelling of turbine rim seal ingestion”, ASME Turbo Expo paper 2001-GT-204 (Also ASME J. Turbomachinery, 2002, vol. 124, pp 306-315).
  8. Chen, J-X: Alstom internal report, Whetstone,U.K.
  9. King, M., Wilson, M. and Owen, M., 2005, “Rayleigh-Bénard Convection in Open and Closed Rotating Cavities” ASME Turbo Expo 2005, paper No. GT 2005-68948
  10. David Apsley: Lecture scripts “Introduction to CFD

This study presents a computational investigation of vortex structures forming within the rim cavities of gas turbines. Utilizing computational fluid dynamics (CFD), both steady-state and transient simulations were conducted on simplified cavity models derived from a 1.5-stage experimental turbine. A range of cavity widths and boundary conditions, including surface-averaged and profile-based inlets and outlets, were explored. The emergence of large-scale rotating structures and Kelvin-Helmholtz instabilities was evaluated under varying non-dimensional purge flow rates at a low non- dimensional purge flow rate. Time-resolved simulations showed the importance of realistic profile boundary conditions in capturing the unsteady flow phenomena. The analysis confirmed the sensitivity of vortex formation to geometric and flow conditions, particularly the boundary specification and purge flow magnitude. Transient simulations using profile inlet velocity and outlet pressure distributions yielded results closely matching experimental observations. These findings contribute to optimizing secondary air systems and improving turbine cooling efficiency while reducing unnecessary purge air usage.

Keywords : Gas Turbines, Rim Cavity, CFD, Vortex Structures, Hot Gas Ingestion, Purge Flow, Kelvin-Helmholts Instabilities.

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