Consideration of Simplified Structural Models for Turbine Vane Modal Analysis

Modal analysis of jet engine hardware is a necessary analytical tool utilized by engineers to understand and predict the vibrational risks to the system. Whereas blades and disks are critically analyzed due to their failure modes and effects, turbine vanes also need to be evaluated with respect to their design modal criteria to minimize potential risks to the engine. Although full hoop models of the entire system are most accurate, the time required for modeling and solution processing is typically prohibitive. Through cyclic symmetry and the use of commercial contact techniques, an analytical model may be created that provides the behavior of the entire system with a fraction of the computing time. However, methods for model simplification, including vane-only models, have not been addressed, and the potential for simplified models to accurately predict system modes is of particular interest. Accordingly, this paper studies the finite element modeling procedures for turbine vane modal analysis using multiple contact methods and cyclic symmetry applied to a turbine vane. An emphasis is placed on evaluating vane-only modeling techniques and an abbreviated turbine casing model. Additional comparisons with a traditional assembly model assess finite element model solution accuracy and efficiency. Ultimately, formal recommendations are offered for structural modeling of turbine vanes, including assessments of accuracy, reduction of frequency prediction capability, and computational efficiency gain.