Testing, analysis, and CFD modeling of a profiled leading edge groove tilting pad journal bearing

Abstract

Testing and analysis of a profiled leading edge groove tilting pad journal bearing developed for light load operation is described. This bearing was designed for a generic, small, high speed steam turbine operating at projected loads of less than 25 psi. (172.4 kPa) and journal surface speeds to 400 Ws (122 m/s). On the second turbine application, a rotor instability was experienced with the oil flowrate reduced to optimize bearing steady state performance. This instability was eliminated by machining a taper on the exit side of the feed groove on each pad. At the reduced flowrate, the profiled groove bearing greatly improved the operating characteristics of the rotor system by reducing vibration amplitudes and stabilizing operation at speed. This paper is divided into two sections. The first section compares the rotordynamics analysis with test data that shows improved unbalance response and operating stability with the profiled groove bearing. The second section provides original insight of the effect of the profiled geometry on the bearing flow field using computational fluid dynamics models.