Volumetric velocimetry measurements of purge-mainstream interaction in a one-stage turbine

Artur Joao Carvalho Batista Soares De Figueiredo, Neys Schreiner, Alex Mesny, Oliver Pountney, James Scobie, Yan Sheng Li, David Cleaver, Carl Sangan

Research output: Contribution to journalArticlepeer-review

Abstract

Air-cooled gas turbines employ bleed air from the compressor to cool vulnerable components in the turbine. The cooling flow, commonly known as purge air, is introduced at low radius, before exiting through the rim-seal at the periphery of the turbine discs. The purge flow interacts with the mainstream gas path, creating an unsteady and complex flowfield. Of particular interest to the designer is the effect of purge on the secondary-flow structures within the blade passage, the extent of which directly affects the aerodynamic loss in the stage. This paper presents a combined experimental and computational fluid dynamics (CFD) investigation into the effect of purge flow on the secondary flows in the blade passage of an optically accessible one-stage turbine rig. The experimental campaign was conducted using volumetric velocimetry (VV) measurements to assess the three-dimensional interblade velocity field; the complementary CFD campaign was carried out using unsteady Reynolds- A veraged Navier-Stokes (URANS) computations. The implementation of VV within a rotating environment is a world first and offers an unparalleled level of experimental detail. The baseline flow-field, in the absence of purge flow, demonstrated a classical secondary flow-field: The rollup of a horseshoe vortex, with subsequent downstream convection of a pressure-side and suction-side leg, the former transitioning in to the passage vortex. The introduction of purge, at 1.7% of the mainstream flowrate, was shown to modify the secondary flow-field by enhancing the passage vortex, in both strength and span-wise migration. The computational predictions were in agreement with the enhancement revealed by the experiments.

Original languageEnglish
Article number041011
JournalJournal of Turbomachinery: Transactions of the ASME
Volume143
Issue number4
Early online date24 Mar 2021
DOIs
Publication statusPublished - 1 Apr 2021

Keywords

  • Cavity flows
  • Computational fluid dynamics
  • Purge flow
  • Purge-mainstream interaction
  • Turbine aerodynamics
  • Volumetric velocimetry

ASJC Scopus subject areas

  • Mechanical Engineering

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