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Numerical Investigations of Flow Pattern and Heat Transfer in a Rotating Cavity Between Two Discs of the Compressor of a Siemens KWU V84.3 Gas Turbine FREE

[+] Author Affiliations
Dieter Bohn, Uwe Krüger

Aachen University of Technology, Germany

Klaus Nitsche

Siemens AG KWU, Mülheim a. d. Ruhr, Germany

Paper No. 95-GT-144, pp. V001T01A035; 8 pages
doi:10.1115/95-GT-144
From:
  • ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition
  • Volume 1: Turbomachinery
  • Houston, Texas, USA, June 5–8, 1995
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-7878-1
  • Copyright © 1995 by ASME

abstract

The rotor of modern gas turbines often consists of single discs forming air-filled rotating cavities. During stationary operation each disc in the compressor section is of nearly uniform temperature. This results from the radial heat conduction in the disc material and from the negligible axial temperature gradients between surface and air in the adjacent cavities. The situation changes rapidly during cold start-ups of the engine. The disc rims respond quickly to the temperature of the mainstream (500 to 600 K), whereas the average temperature of the massive hub section follows with some delay thus forming a radial thermal gradient. This induces a buoyancy-driven flow inside the cavity, which is superimposed by a controlled hot gas ingress. A defined amount of hot air flows radially inwards through the Hirth-type serration at the head of the discs, causes increased convection within the cavity and speeds up the thermal equilibration process in the discs.

Numerical investigations of the very complex flow situation have been carried out to get a better knowledge of both the flow-physics and the heat transfer from the hot fluid to the cold rotating wall.

A modern numerical Finite-Volume-Code with multiblock and body-fitted grid-options has been used to calculate three different cases: one cavity without hot gas ingress and two cases with two different mass flow parameters. The boundary conditions have been chosen in such a way that they cover real gas turbine conditions at the very beginning of the start-up. The most stringent case has been investigated, i. e. the head of the discs and the hot gas mass flow having the mainstream temperature while the discs in the hub region remain at ambient temperature.

It has been found that in the case without throughflow the core-region rotates approximately with the speed of a solid body. In the case of superimposed hot gas flow directed radially inwards, the flow has the character of a potential-vortex-flow, with exception of the regions near the wall. The hot gas is transported to the hub-region so that the heat transfer in this region is very large in the first period of the start-up-procedure.

Some aspects are presented which should be investigated in more detail in future work, especially the 3-D effects and the conjugate heat transfer. First results of a 3-D calculation are shown.

Copyright © 1995 by ASME
This article is only available in the PDF format.

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