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International Journal of Rotating Machinery
Volume 6, Issue 3, Pages 215-226
http://dx.doi.org/10.1155/S1023621X00000208

Swirling Flow Field inside a Hollow Turbine Shaft for an Internal Cooling Air System

1Gas Turbine R&D Center, Hitachi Ltd., Horiguchi 832-2,, Hitachinaka-shi, Ibaraki-ken 312, Japan
2Department of Aeronautics and Astronautics, University of Tokyo, Tokyo, Japan

Received 22 August 1997; Revised 27 August 1998

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The swirling flow field in an internal cooling air system in which the fluid passes through an inducer, a hollow turbine shaft, and a cavity between two disks (referred to as a wheel space) is solved using computational fluid dynamics and the pressure fluctuations on the hollow shaft wall surface are measured.

The three-dimensional compressible Navier-Stokes equations are adopted and discretized by an implicit TVD scheme. The region of the cooling air system is divided into two computational domains: one from the inducer to the hollow shaft, and the other from the hollow shaft to the wheel space. In the analysis of the former computational domain, the roles of components such as inducer blades are shown. In the analysis of the latter, the existence of a rotating spiral vortex at the place where the swirling flow turns radially outward is shown and its characteristics are described.

The main part of the internal cooling air system of a gas turbine is used as an experimental apparatus. Pressure sensors are embedded axially and circumferentially in the hollow turbine shaft to measure unsteady wall pressures. The existence and characteristics of the rotating spiral vortex are confirmed experimentally. The pressure fluctuations due to instability in the rotating wall boundary layer, whose waves propagate both in the positive and negative directions of the shaft rotation, are captured.