Experimental and Numerical Flutter Investigation of the 1^st Stage Rotor in 4-Stage High Speed Compressor

Experimental tests were performed to investigate flutter behaviour of the transonic rotor in a high-speed multistage compressor test facility. Besides the acquisition of overall performance parameters the rig was equipped with special instrumentation such as strain gauges, tip-timing system and dynamic pressure transducers. The 4-stage compressor comprises 3 variable vanes. The instrumentation was able to measure stall and flutter and forced responses of the rotor blades. The experimental data was used to validate the in-house aeroelastic solver. During testing flutter was triggered intentionally at part speed conditions with malscheduled variable vanes. The malschedule changed the flow incidences for the relevant rotor and induced flutter. An aeroelastic simulation was set up according to the flutter conditions found during the experiment. The measured boundary conditions were used to set up the aeroelastic simulation. The calculation shows the torsion mode with a negative aerodynamic damping which confirms the test results. The only difference between test and prediction is the nodal diameter, at which the flutter occurs.