A Full Parametric Model for Turbomachinery Blade Design and Optimisation

This paper presents a full parametric model of a turbomachinery blade. The model forms the geometric backbone of a new aerodynamic design suite, which aims at speeding up the coupled 2D/3D aerodynamic design process. The approach employed here follows the basic design concepts of turbomachinery blades, which are typically defined by a series of cross-sectional aerofoils stacked at their radial location to a three-dimensional blade. Unlike the geometry management in current design systems, the paradigm of a CAD based Master Model has been incorporated in the geometry definition and the corresponding software architecture. Therefore all blade features have been modelled as computational components in the flexible object-oriented software environment. The blade parameterisation enables the 2D aerofoil construction either from the common superposition of the camber line and thickness distribution or the direct control of the suction and pressure side. The sensitivity of the aerofoil aerodynamic performance with respect to a design parameter can be quickly assessed with a fast 2D flow solver. The parameters of the radial stacking line define the axial and tangential shift of each section. The parametric concept facilitates the inclusion of specific shape control techniques such as curvature manipulation and surface smoothing. Furthermore the use of optimisation methods is greatly simplified by the modular program structure, which allows to access single modules of the blade design tool in a batch job. Since the blade design process involves different coordinate systems, unique mapping functions are essential for a consistent update of the blade geometry during a design cycle. The interface to the CAD system is based on the standard data exchange format STEP. The CFD interface makes use of the NetCDF data format for automatic grid generation.