Evaluation of Reduced‑Order Modeling of a Gas Turbine Structure : Using Abaqus Substructures

Sammanfattning

This thesis investigates the use of substructuring techniques to reduce the computationalcost of large-scale finite element analyses of an industrial gas turbine system. A detailedFE model provided by Siemens Energy, including the gas turbine, gearbox, generator shaft,and supporting base frame, is used as the reference model. Selected components are mod-elled as substructures in Abaqus using Guyan reduction and modal reduction with varyingnumbers of retained eigenmodes under fixed, mixed, and free interface boundary conditions.Static gravity load analyses and modal analyses are performed to evaluate the accuracy ofthe reduced models relative to the full FE model. The comparison focuses on displacements,stresses, reaction forces, natural frequencies, effective mass representation, and computationalperformance. The results show that the static gravity load response is reproduced exactlyfor all substructure configurations. For modal analyses, the accuracy of the reduced modelsdepends on the number of retained eigenmodes, with good agreement obtained up to fre-quencies corresponding to the highest retained mode. The use of substructures significantlyreduces CPU time for both static and modal analyses compared to the full finite elementmodel, demonstrating that substructuring provides an efficient and accurate approach whenthe retained modal basis is selected based on the frequency range of interest.