Aeroelastic Effects In A Transonic Compressor With Nonaxisymmetric Tip Clearance

Future axial compressor designs tend to be built with larger relative tip gaps and increased eccentricity, since the core engines are reduced in size. There is considerable uncertainty of the influence of tip clearance non - uniformity on non - synchronous blade vibration amplitudes. The 1.5 stage Darmstadt Transonic Compressor is representative of the front stage of a high pressure compressor. Data is obtained for varying concentric and eccentric tip gap s at design speed. For this study, t he concentric tip gap is increased from 1.25% to 2.5% tip chord length. The investigated non - uniform configurations are 60 % and 96% eccentric. These variations are quite common during engine operation. A modern rotor in blade integrated disc design is used for this research, which is susceptible to vibration due to low mechanical damping. The redistribution of mass flow at the inlet of an eccentric casing influences stall inception. Locally , the compressor is operating unstable, which results in pre - stall disturbances with high count and large amplitude in the sector with a large clearance. The other part of the annulus operates stable and is less disturbed. This aerodynamic diversity results in decreased interaction between fluid and structure. For an eccentric casing, rotor blade vibration amplitudes are lower compared to an equivalent concentric configuration. These results are a novel approach to aerodynamic mistuning