Multi-Stage Cyclic Symmetry Analysis of an Industrial High Pressure Turbine Assembly – Comparing Structural, Modal, and Solve Statistics

Structural analysis of rotating turbomachinery geometry typically can take advantage of cyclic symmetry reduction to facilitate faster solve times and reduced result file size requirements. Historically, these analyses have been limited to decomposing the geometry to a single cyclic sector that shares a common sector count. Concessions are often made in these analyses (eliminating features that do not share a common sector count, artificially changing airfoil counts to force sector counts that are factors of each other, or modelling multiple sector that share a common factor together in a large segment — i.e. model a 1/3 sector) because the savings in solve time and file size reduction are invaluable versus trying to solve a full 360° representation of the geometry. Multi-stage cyclic symmetry is a theoretical technique to create and analyze geometric models that consist of multiple cyclically symmetric structures that have different sector counts. This technique has been demonstrated on many simpler academic cases and has been shown to provide accurate results for a properly setup analysis model. The aim of this paper is to use the multi-stage cyclic symmetry approach on a full two row high pressure turbine assembly (consisting of non-proprietary geometry representative of an industrial assembly) to analyze both a static structural analysis for stress, as well as a modal analysis for natural frequencies and mode shapes. The paper will compare the results from running the same geometry as a full 360° reference case to check the multi-stage analysis for accuracy. Solve times, memory usage, and result file sizes will also be compared to show the benefits of using the multi-stage cyclic symmetry technique.