A stress analysis of a compressor blade in partially blocked inlet condition

Abstract

A full two-way coupling aeroelasticity analysis of rotating machinery and their main components requires considerable computational analysis and central processing unit time. This is why the most common methodology for this type of problem is a one-way coupling between fluid and structure. In this case, forces acting on rotor blades that result from a flow are introduced into a structural model of a blade as a local spot load in the centre of gravity or a series of local spot points deployed along the blade length. However, this method does not take into account how the forces change in a chordwise direction (along chord). An alternative way is to use the method of directly transferring the pressure field as a surface load from the computational fluid dynamics analysis to a structural model of a blade. In this case, various interpolation methods are needed to transfer the results from the computational fluid dynamics mesh on to the structural mesh nodes. In this paper, the authors compare how both methods of load transfer affect rotor blade stress and displacement levels during one period of rotation. Calculations were carried out for the first-stage compressor blade of an aircraft engine. Ansys 12.1 was used to calculate the entire structure. Unsteady computational fluid dynamics calculations were carried out using Fluent for a 1.5-stage axial compressor model. For the numerical calculations a non-viscous flow was used. The unsteady forces were calculated on 10 control cross-sections of a rotor blade. The transient results obtained from the computational fluid dynamics calculations were transferred onto a structural rotor blade model using APDL - an ANSYS language script. For both methods of load transference, transient displacements and transient stresses for the rotor blade were calculated. The harmonic analysis results were compared. Mesh sensitivity analysis was also carried out for the structural model. In the last part of the paper, based on described above methodology a study involved to bird strike was shown in the way of how foreign object debris affects the dynamic stress level of a rotor blade. A comparison between an undisturbed engine inlet and one with an ingested foreign object was carried out. The analysis focused on the first-stage compressor blade of an aircraft engine with a partially blocked radial inlet and will be based on pressure method transferring described earlier.