An Aeromechanical Screening Tool for Turbine Blades

A design tool has been developed to calculate the natural frequencies of shrouded or unshrouded gas turbine blades in seconds to allow designers to perform aeromechanical frequency avoidance checks in the early concept design phase. The tool derives its inputs from a pitch-line aerodynamic calculation and a 1D structural design tool and uses a NACA-based airfoil section generator to create the airfoil sections. It then generates a shell-element based finite element model for the blade and disk sector, performs a pre-stressed modal analysis, and ranks the blades according to their frequency margins with specified aerodynamic drivers. Validation studies comparing this simplified model to high-fidelity solid element FEA models show the frequency error to be below 5% for most cases. The speed of this tool allows for frequency assessment of thousands of designs in a few hours allowing the designer to perform large spacefilling DoEs and select a flow path which minimizes the chances of fundamental mode crossings in later design stages..