Unsteady Aerodynamic Analysis of a Bird-Damaged Turbofan

The unsteady aerodynamic behavior of a bird-damaged fan stage at the inlet of a highbypass turbofan engine is examined with a computational fluid dynamics (CFD) aerodynamic model suitable for use in an aeroelastic response calculation. ANSYS CFX, a commercially available CFD solver, is utilized to perform the steady-state and unsteady CFD calculations for the undamaged and damaged fan. The damaged fan sector consists of 5 damaged blades that correspond to the geometry resulting from a bird strike. An automated mesh deformation scheme using radial basis function interpolation is developed to generate a high quality computational mesh for the damaged geometry. The steadystate calculations of the undamaged fan are verified against those from an industry CFD solver. The steady-state calculations of the damaged fan predict a flow loss of 14.7% with the operating point being near the stall point of the characteristic curve. Furthermore, significant separation and recirculation of the flow results from the damaged blades. The unsteady calculations of the damaged fan exhibit a periodic behavior in which the mass flow rate and total pressure ratio oscillate due to the progression and regression of a region of stalled flow emanating from the damaged sector.