The Fan Rig Darmstadt: Phase-Resolved Aeroelastic Investigation of Transonic Fan Flutter

Abstract This paper introduces the Fan Rig Darmstadt as a high-speed aeromechanics test facility for experimental investigations on modern transonic fan stages and proposes a novel approach for phase-resolved fluid–structure interaction analysis. The facility layout, instrumentation, and results from the baseline campaign are presented. A fan stage was tested under representative conditions across its operating range, including transient throttle maneuvers at the stability limit. For all investigated speeds, the upper operating boundary was limited by flutter. Established methods are applied for performance, aerodynamic, and aeroelastic characterization. The fan map and selected steady-state aerodynamic results demonstrate representative transonic fan characteristics, including tip-shock structures, shock–tip-leakage interaction, blade wakes, and spanwise pressure ratio distributions. Three flutter events are characterized using spectral and correlation-based methods. The results reveal first bending mode flutter with speed-dependent nodal diameters and no evidence of a convective mechanism. In addition, a post-processing approach is proposed and demonstrated to determine fluid–structure phase values near the blade tip in the rotating frame of reference from conventional casing-mounted instrumentation. Casing wall pressure is extracted close to the blade pressure and suction sides using pressure-based blade time of arrival and is related in phase to capacitive blade-tip-timing deflection using least-squares fitting. Application to a representative flutter event shows convergent phase values during flutter onset. The approach provides an experimentally accessible quantity for experimental–numerical comparison and validation of casing-pressure-based fluid–structure phase during fan flutter.