As the demands for lower emissions and increased economic efficiency in today’s aviation market 
get stricter, methods to reduce engine weight and part count, as well as to increase fuel efficiency 
continue to be of prominent interest. One way of realizing weight reductions, is the combination of 
assembly groups in order to jointly fulfill aerodynamic and systemic, as well as structural, tasks 
with a new component. Turbine vane frames (TVF) are one example of such an assembly, realized 
by combining capabilities, that are usually provided by turbine center frames (TCF) and the first 
stator row of the low-pressure turbine. Here, a large, vane-shaped strut can be utilized to fulfill the 
structural demands imposed on the inter turbine casing and, combined with smaller airfoils, 
generate the required swirl for the first low-pressure turbine rotor. This results in a system 
consisting of differing airfoil shapes and chord lengths within the same blade row, which lends 
itself to optimization concerning aerodynamic and structural tasks. 
A suitable parametric representation of this configuration necessitates one parameter set for each 
airfoil type involved. In contrast to a homogeneous blade cascade (e.g. compressor or turbine blade 
rows), the parameter space of such a heterogeneous cascade must typically account for each blades’ 
own parameter values and the geometric shapes of the neighboring, potentially different, blade 
types. 
Hence, an optimization employing such a parameter set requires a robust and efficient consideration 
of the entire permissible parameter space. 
Within the scope of the present work, a full geometric parameterization of a TVF is presented. It 
aims to minimize the number of parameters required to automatically and flexibly represent all 
blade types involved in a TVF row in all three dimensions. A procedure is presented, which sets the 
parameters within their permissible ranges according to the imposed constraints using an internally 
developed code. The workflow subsequently passes the proposed parameter set to a commercially 
available CAD package for full geometry generation. 
Additionally, the investigation discusses interdependencies between parameters and details their 
respective significance for the adjustment process. Furthermore, the capability of the chosen 
parameterization and the adjustment process to rebuild an exemplary reference TVF geometry is 
demonstrated. The results are verified by comparing not only geometrical profile data, but also 
validated CFD simulation results between the rebuilt and original geometries. Measures taken to 
ensure the robustness of the method are highlighted and evaluated, relying on an optimal space 
filling Design of Experiment (DoE) model to explore the available design space and demonstrate 
the robustness. 
Finally, the embedding of the proposed method within the framework of an automated, gradient free 
numerical optimization is discussed. Herein implications of the proposed method on response 
surface modeling in combination with the optimization method are highlighted. However, the main 
focus is placed on improvements in terms of optimization efficiency, which are achieved by a-priori 
excluding unsuitable blade combinations while keeping restrictions to the design space as limited as 
possible.

Adaptive Geometry Representation of Turbine Vane Frames for Use in Optimization

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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