Validation and Verification of Flutter CFD Tools for Steam Turbines with Cascade Measurements
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
This work has been commissioned by Alstom Power with the scope of assessing the validity of a new flutter calculation method to be integrated in the current stream turbines blade design process.
Flutter is universally defined as an aeroelastic unstable phenomenon which occurs when energy is transferred to a structure from the flow surrounding it. If the structure’s mechanical damping is not sufficient to dissipate the added energy, vibration in the blade can escalate until material failure is reached. It is the task of engineers to ensure that a blade design will not encounter a flutter condition during its normal operation. Numerical methods offer today the most cost- and time-effective approach to the problem.
In the present study three different tools are considered: ANSYS CFX 12.1 (periodic boundary conditions), ANSYS CFX 14.0 (phase-shifted boundary conditions) and AU3D (phase-shifted boundary conditions). Two test cascade profiles, the FUTURE-EPFL and the Standard Configuration 11, are analysed. The first features subsonic, attached flow and the latter a transonic separated flow. The influence of simulation parameters and numerical discretisation on steady and unsteady results is assessed. For each case, the numerical solution is compared to experimental measurement data covering a comprehensive range of inter-blade phase angles.
It is concluded that the periodic boundary conditions method generally offers a more consistent approach, at the cost of a greater computational time. Phase-shift methods, on the other hand, showed a potential for calculating aerodynamic damping in a time- effective way; although a greater time step dependency was revealed.
A new method for computing aerodynamic damping in CFX is described in this document. The method consists in performing the Fourier transform on pressure coefficients in the solver, so that the periodicity of the solution can directly be monitored during the run.
Place, publisher, year, edition, pages
2012. , 105 p.
Turbomachinery Steam Turbine Flutter CFD Validation CFX
IdentifiersURN: urn:nbn:se:kth:diva-102999OAI: oai:DiVA.org:kth-102999DiVA: diva2:558057
Master of Science - Turbomachinery Aeromechanic University Training
2012-09-05, M263, Brinellvägen 68, Stockholm, 16:02 (English)
Vogt, Damian, Dr
Vogt, Damian, Dr