Gas turbine efficiency deterioration due to particulate deposition is a well known phenomenon especially in industrial machines which operate on “heavy” fuels. The result is the need for frequent blade surface cleaning after certain hours of operation. The present study investigates the flowfield modification and the corresponding aerodynamic losses due to the progressive particle deposition on the aerofoil surfaces of a representative turbine stator cascade.

The flowfield is calculated with the Katsanis (TSONIC) code coupled to the STAN5 one for the boundary layer. The losses are calculated by momentum scanning - Stewart’s method. The problem is quasi-steady since the time scale in turbine blade flows is of the order of milliseconds, while in the deposition the data indicate slow growth rates with time scales of the ordr of hours. The particle deposition calculation is based on a turbulent diffusion model proposed by Yau and Young (18) and the particle characteristics refer to ash. The main parameters calculated are the new thickness distribution, the throat blockage, the aerodynamic losses and the transition point. The paper comments on the cleaning process based on these results.

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