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Experimental and Theoretical Investigations of Heat Transfer in Closed Gas-Filled Rotating Annuli II FREE

[+] Author Affiliations
D. Bohn, R. Emunds, V. Gorzelitz, U. Krüger

Technical University of Aachen, Aachen, Germany

Paper No. 94-GT-175, pp. V004T09A027; 11 pages
doi:10.1115/94-GT-175
From:
  • ASME 1994 International Gas Turbine and Aeroengine Congress and Exposition
  • Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration
  • The Hague, Netherlands, June 13–16, 1994
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-7886-6
  • Copyright © 1994 by ASME

abstract

Increasing the thermal efficiency by higher turbine inlet temperatures is one of the most important aims in the area of gas turbine development. Because of the high temperatures not only the turbine vanes and blades have to be cooled, but also the knowledge of the mechanically and thermally stressed parts in the hottest zones of the rotor are of great interest. The prediction of the temperature distribution in a gas turbine rotor containing closed, gas-filled cavities, for example in between two discs, has to account for the heat transfer conditions encountered in these cavities. In an entirely closed annulus forced convection is not present, but a strong natural convection flow exists, induced by a non uniform density distribution in the centrifugal force field.

In /3/ experimental and numerical investigations on rotating cavities with pure centripetal heat flux had been carried out. The present paper deals with investigations on a pure axially directed heat flux. An experimental set-up was designed to realize a wide range of Ra-numbers (2·108<Ra<5·1010) usually encountered in cavities of gas turbine rotors.

Parallel to the experiments numerical calculations have been conducted. The numerical results are compared with the experimental data. The numerical scheme is also used to account for the influence of Re-numbers on heat transfer without changing the Ra-number. This influence could not be pointed out by experiments, because a variation of the Re-Ra characteristic of the employed annuli was not possible.

It was found that the numerical and experimental data are in quite good agreement, with exception of high Ra-numbers, where the numerical scheme predicts higher heat transfer than the experiments show. One reason may be that in the experiments the inner and outer cylindrical walls were not really adiabatic, an assumption used in the numerical procedure. Moreover the assumption of a 2-D flow pattern may become invalid for high Ra-numbers. The influence of 3-D effects was studied with the 3-D-version of the numerical code.

In opposite to the radial directed heat transfer it was found that the Nu-number is much smaller and depends strongly on the Re-number — whereas the radial heat transfer is only weakly influenced by the Re-number.

Copyright © 1994 by ASME
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