A Differentiated Geometry Bladeparameterization Methodology for Gasturbines

The present paper is about the turbomachinery blade geometry parameterization, which has been developed at the DLR institute for propulsion technology for the last two decades. It was implemented into the software BladeGen, which is used to design blades and vanes for axial and radial compressors as well as for turbines. The parameterization uses typical geometric variables such as characteristic angles and lengths in combination with B-spline parameters like control points and knot vectors to generate a variable number of two-dimensional profile-sections, which are transformed into three-dimensional space and connected via NURBS surfaces to form blade surfaces and solids. BladeGen is written in C but it also enables its integration into other workflows by C++ and Python bindings. It uses an in-house NURBS library and additionally utilizes the OpenCASCADE Technology framework as an open-source CAD library to enable various output formats like Step, IGES or BRep. To facilitate its use for design optimization, BladeGen is algorithmically differentiated using ADOL-C.