Finite Element Transient Modelling for Aero-Thermo-Mechanical Analysis of Whole Gas Turbine Engine

Abstract

Abstract It is here proposed a numerical procedure aimed to perform transient aero-thermo-mechanical calculations of large power generation gas turbines. Due to the frequent startups and shutdowns that nowadays these engines encounter, procedures for multi-physics simulations have to take into account the complex coupled interactions related to inertial and thermal loads, and seal running clearances. In order to develop suitable secondary air system configurations, guarantee structural integrity and maintain actual clearances and temperature peaks in pre-established ranges, the overall complexity of the structure has to be reproduced with a whole engine modelling approach, simulating the entire machine in the real operating conditions. In the proposed methodology the aerodynamic solution providing mass flows and pressures, and the thermo-mechanical analysis returning temperatures and material expansion, are performed separately. The procedure faces the aero-thermo-mechanical problem with an iterative process with the aim of taking into account the complex aero-thermo-mechanical interactions actually characterizing a real engine, in a robust and modular tool, combining secondary air system, thermal and mechanical analysis. The heat conduction in the solid and the fluid-solid heat transfer are computed by a customized version of the open source FEM solver CalculiX®. The secondary air system is modelled by a customized version of the embedded CalculiX® one-dimensional fluid network solver. In order to assess the physical coherence of the presented methodology the procedure has been applied to a test case representative of a portion of a real engine geometry, tested in a thermal transient cycle for the assessment of the interaction between secondary air system properties and geometry deformations.