Rotor Blade Cooling Circuit With Offset Rib for Root Stress Relief
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Solution Overview
Problem
Existing turbomachine rotor blades experience high stress concentrations and strain at the intersection of the airfoil and platform due to thermal and mechanical loading, limiting component lifetime.
Innovation Solution
A rotor blade design featuring a serpentine cooling circuit with an offset rib positioned proximate the leading edge, which includes perforations and varies in thickness and angle relative to the camber line, providing enhanced structural compliance and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If geometric discontinuities such as root turns, tip turns, and internal ribs are placed away from the airfoil-platform intersection, then stress concentrations are reduced, but the cooling circuit cannot effectively reach the high-stress region for cooling
Solution Approach 1:
The offset rib is positioned specifically at the airfoil-platform intersection region, creating a localized cooling structure exactly where thermal and mechanical stresses are highest. This local placement allows the cooling circuit to target the critical high-stress zone without requiring geometric discontinuities to be moved away from the intersection.
Solution Approach 2:
The offset rib extends in the spanwise direction (along the camber line) rather than only radially, creating a two-dimensional cooling structure. This spanwise extension allows the cooling circuit to cover the airfoil-platform intersection area more effectively, reaching the high-stress region from a different dimensional approach.
2Temperature
If the offset rib is positioned closer to the leading edge with spanwise extension, then cooling coverage at the airfoil-platform intersection is improved, but the rib structure becomes more complex
Solution Approach 1:
The offset rib is divided into distinct portions: a radially extending outer portion and a spanwise extending offset portion. This segmentation allows each portion to perform its specific function - the outer portion provides radial support while the offset portion extends cooling coverage spanwise, simplifying the overall design compared to a fully complex three-dimensional rib structure.
Solution Approach 2:
The offset rib provides partial spanwise extension rather than full coverage, which is sufficient to achieve the cooling objective at the airfoil-platform intersection without requiring a completely complex rib structure. This partial action achieves the necessary cooling effect while maintaining structural simplicity.
Data Source
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AI summary
A rotor blade (328) for a turbomachine (10) is provided. The rotor blade (328) includes a platform (342), an airfoil (340) extending from the platform (342), and a cooling circuit (372) extending within the platform (342) and the airfoil (340). The cooling circuit (372) includes a plurality of cooling passages (356) defined by a plurality of ribs (374). The plurality of ribs (374) includes an offset rib (380).