Modeling of Transition Geometry

Problem Statement 

 

For most turbine and compressor blades, the transition from the 3D blade surface to the root or shroud is achieved through a type of transition geometry. Depending on the application, this transition geometry can exhibit various forms. It is typically well-defined but geometrically arbitrary, and it can significantly impact the performance and flow capacity of a turbine stage. Consequently, it should be accounted for in numerical computations.

Large rotor or casing pitch angles, thin trailing edge thicknesses, and highly curved 3-dimensional surfaces make the description of the transition geometry a challenging task.

• Commercial meshing generators often cannot create the transition geometry between the blade and the root/shroud at all or cannot do so with sufficient quality.
• Commercially available CAD programs are similarly unable to generate a surface description of the transition geometry in a way that meets the requirements of the meshing algorithms used by commercial mesh generators.

Objectives

 

The aim of the project is to develop a mathematical algorithm that calculates a surface description of the 3D blade, including the transition geometry, and outputs this surface description as a unique set of surface coordinates for further processing. Using datasets that exhibit typical as well as challenging characteristics of real blades, it is tested if and assured that the transition geometry can be successfully and standardized calculated for more complex settings.

 

Methods

 

• Surface description using splines, NURBS, etc.
• Iterative methods for calculating optimal cross-sections, intersection points and lines
• Fitting of transition radii to given blade and root or shroud data
• Implementation in MATLAB and C++

Challenges

 

The transition geometry must be adaptable to an arbitrary 3D blade geometry. Blades with a very small curvature radius at the thus extremely thin trailing edges and/or specific geometric boundary conditions at the root and shroud impose particularly high demands on the stability of the method. Therefore, constraints on the continuity of transitions, relative pitch angles, and similar requirements must be strictly met. The algorithm to be developed must handle a wide range of geometric boundary conditions while still producing a transition geometry that is manufacturable and can be uniformly used in other software applications, such as in computational fluid dynamics (CFX) simulations.

Assignment to the HRW Key Theme 

 

•  Energy and Resources