Rotordynamic Analysis and Redesign of High-Pressure Turbine Test Rig

The high-speed test rigs pose several operational problems originating from rotordynamics, bearings, lubrication and thermal gradients. When the critical speeds exist within the design speed, it is possible to accelerate the rotor through resonant speed zones in many applications. However, in very few cases, the resonance crossovers pose serious problems resulting from operational schedules and demand major modifications to rotor-bearing system. The design modifications, driven by rotordynamic considerations, carried out for an existing high-speed test rig with serious operability issues are presented in this paper. During operation, one of the bearings supporting the rotor has failed twice causing significant damages. On both occasions, the bearing failure took place when the rotor was approaching the first critical speed. Considering the difficulty experienced to pass the first critical speed quickly, the rotor-bearing system of the rig is completely redesigned with safe separation margin away from the design speed. Designer’s challenges arising from overall layout, manufacturing, imported hardware, assembly and operation are highlighted while addressing the problem. The turbine stage could be tested successfully up to its design speed after implementing all design modifications.