Hybrid Ceramic Bearing Development for Gas Turbine Engines

Abstract

Over the past seven years, an extensive hybrid bearing development program has been conducted at Textron Lycoming. This paper will report the details of testing and the extraordinary results which can be obtained with silicon nitride balls as applied in hybrid bearings on gas turbine engines. This paper describes the analytically predicted advantages which low mass silicon nitride balls offer at speeds over 2.0MDN. Rig testing comparing hybrid bearings to standard bearings is reported. Testing included heat generation evaluation which showed that hybrid bearings generate an average of 40% less heat than standard bearings. Rig simulation of the AGT1500 mission duty cycle demonstrated that the hybrid silicon nitride bearing system is robust enough to handle the most severe operating conditions. Testing under severe slipping/skidding conditions demonstrated good resistance to skid failure. Under conditions selected to produce high wear, no wear was induced in a hybrid bearing while severe wear was induced in the M50 steel bearing. These preliminary successes lead to active engine testing on the AGT1500 and a new test program to demonstrate operation at 4.0 MDN. As a result of these programs Textron Lycoming now considers hybrid ceramic bearings as a viable design to be used in high speed development applications. This paper provides design detail and test data covering the work outlined above.