Ceramic/Metal-Shaft/Hub Connection for Applications in Small High Temperature Ceramic Gas Turbine Rotors

Abstract

The paper provides a synopsis of the research activities currently pursued at the Technical University Berlin, Hahn-Meitner-Institut Berlin and Honeywell Engines & Systems with respect to ceramic/metal joining concept for small ceramic high temperature gas turbine rotors. The objective was to design an interference fit type joint that can be cost effectively produced and reliably transmit torque at elevated temperatures (up to 800°C). Experimental and numerical investigations have been carried out to examine two slightly different designs which both utilize the same basic principle of a shrink fit connection that is able to compensate the thermal expansion mismatch between ceramic and metal and therefore is capable of keeping the contact pressure at the ceramic/metal interface nearly constant over a wide operating temperature range. The joints have been tested under torsional load at isothermal conditions in order to determine the static coefficient of friction and the torque carrying capability, as well as to optimize the joint geometry. The stress distribution inside the joint has been determined by FEA and subsequently evaluated by measuring the residual stress state of the joint in the ceramic by neutron diffraction.