Investigation of the Flutter Stability of a Transonic Fan with Inlet Distortion

Abstract

Flutter is a self-excited aeroelastic instability phenomenon which can cause material fatigue and, even worse leads to blade failure. The risk of flutter has to be avoided over the whole operating range especially near operating limits. This paper looks at the prediction of flutter instability of the transonic fan under inlet distortion. The flutter stability analysis with an inhouse unsteady Reynolds-average Navier-Stokes (URANS) solver is performed by applying the so-called energy method. The phase-shifted boundary condition based on direct-store method is used, which enables reducing the computational domain to a one/two passages for all inter-blade phase angles (IBPAs), thus providing considerable saving in computing time. The more efficient double passage method is also adopted in our solver. The solver based on phase-shift boundary condition is first validated by the unsteady aerodynamic force prediction of standard configuration 4 (STCF4) turbine. The results are compared with that by multi-passage solver. Then the flutter boundary of NASA Rotor 67 vibrating in its first natural mode is calculated and the influence of inlet distortion on flutter instability is investigated.