Method for Coupled Partitioned Fluid-Structure Interaction in Heat Transfer for Transient and Steady State Analysis of Aero Engines Applications

Authors

Ute Israel  - MTU Aero Engines AG, Germany
Francois Cottier - MTU Aero Engines AG, Germany
Danice Monteiro - MTU Aero Engines AG, Germany
Christopher Hartmann - University of Stuttgart, Germany

Abstract

Fluid-Structure interaction has a significant impact on heat transfer in aero engines. Thermal interaction of solid and gas appears e.g. for secondary flow cavities in compressor and turbines. Coupled multiphysics simulations including three systems CFD, structure analysis and gas network can significantly improve quality and efficiency of conjugate heat transfer analysis. A method for fluid-structure coupling for special purpose demands of aero engines heat transfer is presented. It is based on a partitioned approach designed to guarantee for standard processes, methods and tools (like mapping methods and solvers) for industrial applications and implemented as central coupling control software (Cosmix) flexible in embedding respective modules on demand. Fluid temperatures show much faster reaction than material temperatures and time scales differ for the respective domains. Typically a thermal flight mission analysis of solid material is resolved in very fine time steps to optimally represent the transient behavior during a flight cycle. An implicit fluid-structure coupling approach delivers transient mission temperatures, which are prerequisites for an elaborated lifing analysis. It is an efficient approach to take the interaction with fluids into account is to embed steady state or stationary CFD analyses for much fewer steps at characteristic operational points. Since those point are irregularly spread over the mission subiterations over time periods with several solid time steps are realized. To improve the prediction within these time periods the method is enhanced by using transition curves for prediction and fluid load scaling. Transitions curves results from engineering approaches like test data, analytical studies and further experience. Within this method the solid model prescribes the time. Thermal analysis of aero engines is often based on 2D rotational symmetric finite element models. Therefore not only mapping on non-matching grids interfaces of 3D models but also mapping from 3D to 2D models and back is implemented including averaging methods. The multiphysics method includes the coupling of the advective system representing the secondary air system with mapping of interface data and global convergence control respectively. The coupling method is validated with experimental data for conjugate heat transfer. A V-ripped channel has been transiently measured and simulated. Comparisons are carried out for different CFD coupling time strategies. Applications of academic and industrial type will be presented. The method has been used for thermal coupling of a typical engine low-pressure turbine inner air seal and further secondary flow cavities in compressor and turbines.