New Bearing Concepts for Gas Turbines

This paper surveys two bearing approaches that may be considered for gas turbine applications. The first is the hybrid bearing which uses a fluid film in parallel or in series with the rolling-element bearing, and whose objective is to increase the L₁₀ life of the rolling-element bearing in high-load and/or high-speed applications. In the parallel arrangement this objective is sought by load sharing between the fluid-film and rolling-element bearing components. In the series arrangement, the objective is sought by achieving a decrease in the effective speed of the rolling-element bearing. The series approach also provides radial, viscous, damping, and this paper derives the relationships necessary for such design. The second approach is the use of gas bearings as a solution to problems of high-temperature operation. The merits and potential problem areas of gas bearings in advanced gas turbine applications are discussed and some appropriate gas bearing types are described.