Application of Abrasive Coatings to Clearance Control in the Gas Turbine

Abstract

Efficiency of a gas turbine is reduced by vane tip losses in the compressor section; also, vane tip/rotor rubs can produce catastrophic failure of a gas turbine engine. This paper describes a test rig and experimental data obtained evaluating abrasive coatings for clearance control between the vanes and the rotor in a gas turbine compressor. Plasma/flame sprayed oxides, carbides and bonded abrasives were tested under conditions duplicating those encountered in the compressor section. The effectiveness of the coatings in grinding away the vane tips to provide minimum clearance without damage to the vane or rotor was determined. Coatings with rough, sharp abrasive grains were most effective. The laboratory tests were confirmed in engine development tests and by application to a compressor rotor now in operation.