High speed interaction between an abradable coating and a labyrinth seal in turbo-engine application

Abstract

The design of gas turbine aims to enhance the engine efficiency by developing new materials able to work at higher temperatures, or to promote new technologies, fuel management and airflow direction. One solution is the reduction of clearance between rotary parts in turbomachinery air systems. This clearance reduction causes direct interactions in the secondary air system of a turbo-engine when a rotary seal, called labyrinth seal, rubs on the turbo-engine as a result of successive starts and stops, thermal expansions and vibrations. The purpose of the present paper is to study interaction phenomena between an abradable material (Al-Si 6%) and a nickel alloy (718 alloy) during high speed contacts. A high speed test rig has been designed to simulate interactions between labyrinth seals and abradable coatings in similar operating conditions of turbo-engine in terms of geometries, rotational and linear velocities. A series of experiments has been carried out in order to get a first assessment under different turbo-engine operating conditions. Experimental results are presented using visual observations of test samples, quantitative approaches of interacting forces and micrographic observations. This work provides new basic data for a preliminary study of the interaction between a labyrinth seal teeth tips and its casing for turbo-engine applications.