Mistuning with Aero-coupling II (Mistuning of Aerodynamically and Structurally Coupled Bladings)

• Applicants: Dr.-Ing. Lars Panning-von Scheidt; Professor Dr.-Ing. Jörg Seume; Professor Dr.-Ing. Jörg Wallaschek
• Subject Area: Mechanics ; Hydraulic and Turbo Engines and Piston Engines
• Term: from 2013 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 239841452

The project "Mistuning with aerodynamic coupling II" aims at providing an experimentally verified simulation method for the numerical prediction of mistuned bladed disk vibrations in turbomachinery. The reduced order model (ROM), developed in a previous project, is validated by experimental vibration measurements of various bladeddisk assemblies. The developed program ROMI (Reduced Order Models for Mistuned Turbine Blades) allows numerically efficient vibration simulations under consideration of aerodynamic and nonlinear couplings by shrouds and underplatform dampers. Anaerodynamically coupled compressor blisk and a compressor rotor with nonlinear blade root coupling (dovetail joint) rotating in vacuum are used as experimental demonstrators. The forced vibrations of the blisk, excited by the fluid flow and acoustic speaker excitation, are measured by means of a tip timing system. The experimental invacuostudy of nonlinear blade-disk joints is performed with magnetic excitation and strain gauges. The comparability of numerical and experimental results is ensured by complementing the reduced order model with boundary conditions which are specific to the installed test rigs and their operation conditions (blade root coupling, centrifugalloads, fluid pressure and temperature) and which so far have not been considered in the model. To enable the efficient modelling of geometrically complex fir-tree roots, the reduction method is extended by an additional step to reduce the number of degrees of freedom related to contact interfaces. In addition, the dependence of aerodynamic coupling coefficients on the vibration frequency is studied for different mode shapes. Based on the outcome of this study, an aerodynamic surrogate model is developed for thenumerically efficient approximation of frequency-dependent aerodynamic coupling coefficients.

• DFG Programme: Research Grants