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International Symposium on Heat Transfer in Turbomachinery
August, 24-28, 1992 , Marathon, Greece

DOI: 10.1615/ICHMT.1994.IntSympHetatTransTurb


ISBN Print: 1-56700-016-9

ISBN Print: 978-1-56700-016-0

Thermal Barrier Coatings for the Protection of Coal Fired Gas Turbines

pages 131-140
DOI: 10.1615/ICHMT.1994.IntSympHetatTransTurb.110
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ABSTRACT

The influence of gas turbine blade coating characteristics on the mechanism of heat and mass transfer, coupled with deposition and erosion hazards is presented. Tests were carried out on a small turbine model and a full scale experimental turbine. Experiments performed on the model showed that using only submicron particles (mean diameter .06 micrometers) thick coatings, up to 1 mm, were obtained. Supermicron particles (mean diameter 50 micrometers) did not form deposits, while different mixtures of both size particles allowed to obtain coatings reaching an equilibrium thickness between 50 and 500 micrometers after 5-6 hours. The coating formed changed the heat transport and the temperature at the blade surface. Formation of a protective coating with a thickness of 500 micrometers reduced the blade temperature by 120±20 K.
The full scale gas turbine for the study of thermoprotective coatings is part of an experimental facility, which comprises an external compressor, a counter-current combustion chamber, supply systems for coal, liquid and gaseous fuels and a main compressor.
The results show that it is possible to control the coating thickness by changing the relative amount and size of the particles injected. Natural and artificial defects created in the coating were self-repaired by accelerated deposit progression at the local spots of the removed layer. In conclusion it has been shown that self-regulating thermoprotective coatings are feasible for real coal fired turbines.

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