Aeroelastic Response of Bird-Damaged Fan Blades Using a Coupled CFD/CSD Framework

Abstract

The aeroelastic response of a bird-damaged fan stage at the inlet of a high-bypass ratio turbofan engine is examined using a combined CFD/CSD model. ANSYS CFX is used for the computational fluid dynamic (CFD) calculations combined with the ANSYS Multifield (MFX) solver that couples ANSYS CFX with ANSYS Mechanical APDL to perform aeroelastic response calculations. The damaged fan sector consists of 5 blades that represent the geometry resulting from a numerical bird strike simulation. The forced response of the undamaged blades downstream of the damaged sector exhibits the highest level of structural response. The structural response of these undamaged blades is dominated by the first bending mode and increases in amplitude with time. The aeroelastic response shows a similar behavior, with the downstream undamaged blades exhibiting a growing structural response that is dominated by the first bending mode. The aeroelastic response of the damaged blades also contains contributions from the second torsion mode. An examination of the work exerted by the aerodynamic forces suggests that the growth in blade response for the upstream damaged blade is due to an aeroelastic behavior that may be indicative of a potential instability. Nomenclature D Number of RBF driver pointṡ mMass flow ratė m R Referred mass flow rate q m

Forced and Aeroelastic Response of Bird-Damaged Fan Blades - A Comparison and Its Implications

“…28, and it was concluded that the "coarse" mesh identified in Ref. 28 is sufficiently accurate for the objectives of the current study. The ANSYS TurboGrid ATM topology is not applicable for full wheel geometries that include a set of damaged blades.…”

“…Mesh sensitivity studies were conducted in Ref. 28, and it was concluded that the "coarse" mesh identified in Ref. 28 is sufficiently accurate for the objectives of the current study.…”

“…A mesh sensitivity was conducted in Ref. 28 to identify the mesh resolution suitable for the objectives of this study. The structural mesh consists of 5,712 nodes and 4,020 elements per blade for a total of 137,088 nodes and 96,480 elements for the full wheel model.…”

“…Further details of the coupled fluid-structure framework, including the aerodynamic load transfer and mesh deformation scheme, is available in Ref. 28. Information regarding the coupling algorithm and mesh mapping scheme is available in the ANSYS MFX documentation.…”

“…In Ref. 24, the authors presented an aerodynamic model that is capable of capturing the behavior of a damaged fan sector of a commercial turbofan engine and is suitable for modeling both the forced and aeroelastic response of the bird damaged blades. Subsequently in Ref.…”