Wavy Mate-Face Turbine Endwall for Secondary Loss Control
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Solution Overview
Problem
Existing turbine designs face challenges in implementing non-axisymmetric contoured endwalls due to mechanical and thermal issues at the mate faces of adjacent platforms, which hinder the realization of performance benefits and increase secondary losses from horseshoe vortices.
Innovation Solution
The endwall contouring incorporates bulges and depressions with controlled elevation variations, limiting the maximum elevation difference at mate faces to 15-60% of the axial chord length, ensuring mechanical feasibility and thermal stability while maintaining aerodynamic performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If non-axisymmetric contoured endwalls are implemented to reduce secondary losses, then aerodynamic efficiency is improved, but mechanical integrity and thermal stability deteriorate due to issues at mate faces
Solution Approach 1:
The endwall contouring is applied locally in specific regions rather than uniformly across the entire endwall surface. Contoured regions are positioned selectively to target horseshoe vortex formation zones while leaving other areas with simpler geometry, thereby maintaining mechanical integrity in critical mate face regions while achieving aerodynamic benefits in flow-critical regions.
Solution Approach 2:
Non-axisymmetric contoured regions are introduced to the endwall surface to disrupt the symmetric horseshoe vortex structure. The contoured regions feature asymmetric elevation variations with peaks and valleys positioned at specific angular locations to optimize flow control and reduce secondary losses while maintaining overall structural stability.
2Loss of energy
If complex contoured endwalls are used to improve aerodynamic performance, then secondary losses are reduced, but manufacturing complexity increases
Solution Approach 1:
The endwall surface is divided into distinct segments: contoured regions with complex geometry and non-contoured regions with simpler geometry. This segmentation allows the complex contoured features to be concentrated in areas where they provide maximum aerodynamic benefit while leaving other areas simpler for manufacturing purposes.
Solution Approach 2:
Rather than applying complex contoured geometry to the entire endwall surface, the invention applies contoured regions only partially to specific areas where horseshoe vortex formation occurs. This partial action approach achieves the necessary aerodynamic performance while significantly reducing overall manufacturing complexity compared to full-surface contouring.
3Loss of energy
If elevation variations at mate faces are increased to optimize aerodynamic contouring, then flow control improves, but mechanical feasibility and thermal stability deteriorate
Solution Approach 1:
Elevation variations are applied locally within contoured regions rather than across the entire endwall surface. The contoured regions have controlled elevation variations optimized for flow control, while mate face regions maintain more moderate geometry suitable for mechanical assembly and thermal management.
Solution Approach 2:
The elevation variation parameters are carefully controlled and constrained within specific ranges to balance aerodynamic performance with manufacturing feasibility. By optimizing the magnitude and distribution of elevation variations, the invention achieves effective horseshoe vortex control while maintaining mechanical integrity and thermal stability.
Data Source
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AI summary
A turbine stage (100) includes a first and a second airfoil (10a, 10b) extending respectively from a first and a second platform (12a, 12b) that form an endwall (40) for a flow passage. The endwall (40) has a nominal surface (60) that is axisymmetric about an axis of the turbine stage. The endwall (40) further includes at least one contoured region (42, 46) that is non-axisymmetric with respect to the axis. The at least one contoured region (42, 46) extends from the first (12a) to the second platform (12b) across a platform splitline (30). The global maximum variation in elevation AEW of the endwall (40) is at least 3% of an axial chord length L of the airfoils (10a, 10b) on the endwall (40). The maximum variation in elevation AMF at the mate faces (26, 28) of the platforms (12a, 12b) lies in the range 15-60% AEW.