Feasibility of Tapered Roller Bearings for Main-Shaft Engine Applications

A survey of 2-to 10-poundssecond-airflow aircraft gas turbine manufacturers indicated an increase in shaft speed in projected applications. A shaft speed increase results in an increase in the load-carrying requirement, and contact stresses due to centrifugal forces on the rolling elements, in the main-shaft bearings. One approach to reducing the contact stresses in the thrust-loaded bearing is to increase the contact area between the rolling elements and races by using tapered roller bearings in place of angular-contact ball bearings. An analytical study of tapered roller bearings is discussed, and the results of an analysis are given in which the principal design parameters were varied to optimize the design for high speed. This analysis included the standard inner ring flange design and a novel outer ring flange design. The results of tests performed with three different tapered roller bearing designs commercial, aircraft-quality inner ring flange, outer ring flange are presented.