As temperatures in jet engine combustion chamber and turbine increase, the relevance of heat transfer between structure and secondary airflow is increasing. Secondary air properties greatly influence material temperatures, which control the thermal expansion of engine parts. Redefining tip clearances and seal gaps, this modifies considerably pressure losses and mass flow rates in the air system, impacting flow and material temperatures. The coupling effect, estimated strong, must be accurately addressed to obtain an optimized secondary air system design. The aerodynamic calculations yielding mass flows and pressures, and thermal analysis providing temperatures and the material expansion are performed separately. In reality, there are interactions currently not considered which would require a lot of time-consuming iterations. The present investigation aims at taking this mutual interaction into consideration in a robust and modular analysis tool, combining secondary air system, thermal and mechanical analysis. For air system calculations, a network representation with nodes, chambers, connected by pressure loss devices is used. This network is coupled with a thermomechanical model of the engine secondary air system in the free finite element software CalculiX® [1]. This paper presents the first module implemented in CalculiX®, dedicated to solve typical Secondary Air System problems and gives an insight on the implementation of the coupling process currently under development.

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