Optimisation by behaviour modelling of a protective porous material

Abstract

During the friction between rotating gas turbine blades and internal body envelope on which is sprayed by the “Atmospheric Plasma Spraying” process a protective porous sacrificial material, there is a blades wear or material displacement. These phenomena which appear during the thermal dilation of the turbine rotor cause a gap between the body casing and the blades top. This clearance lets the combustion gases which do not take part in the power production to pass. There are then reduction in the efficiency and loss of turbine power. Four factors influence the behaviour of the turbine blades and the porous material filled in certain places by boron nitride, which behaves as a lubricant solid. The aim of this work is to investigate the behaviour of a particular sacrificial porous material, the BN–AlCrNi–polyester during inter-reaction with the blades, and the blades’ behaviour under experimental conditions of operating machine. It is then necessary to determine which of these four parameters is dominating and to describe by model the behaviour of each one of them, and the interaction between them. Tests are done with different blade incursion velocities within the coating, as well as with different linear blade speeds and incursion depths. The obtained results are shown in the form of graphs that describe how do the material transfer or blades’ wear occurs, and are the different phenomena observed on the coating. These results help us to appoint the parameters’ values for which we do not have these phenomena.