Turbine Blade Tip Cavity Ejector Cooling
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Solution Overview
Problem
Turbine blades in gas turbine engines face inefficiencies and degradation due to mechanical and thermal stresses, particularly in thin portions like the trailing edge of the airfoil, where internal cooling circuits are ineffective and cooling medium leakage occurs, leading to hot spots.
Innovation Solution
A turbine blade design featuring a unique tip cavity with a pocket opening and a cooling hole that communicates with the internal cooling circuit, allowing high-velocity ejection of the cooling medium to enhance convection cooling and reduce leakage by creating a pressure differential, drawing the medium towards the pocket opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If an internal cooling circuit is used to cool turbine blades, then cooling capacity is improved, but cooling effectiveness in thin portions (trailing edge) deteriorates due to inability to form effective internal circuits
Solution Approach 1:
The cooling system is segmented into two distinct components: an internal cooling circuit for bulk cooling and a tip cavity with cooling hole for targeted cooling of the trailing edge. This segmentation allows each component to address specific cooling needs without requiring complex integration throughout the entire blade structure.
Solution Approach 2:
The cooling approach transitions from two-dimensional internal circuit cooling to three-dimensional cooling by introducing a tip cavity that extends to the blade surface. The cooling hole penetrates through the trailing edge thickness, creating a third dimension for heat dissipation that directly addresses the thin portion cooling problem.
2Temperature
If cooling medium is expelled into the blade tip, then cooling capacity is improved, but cooling medium leakage over sidewalls increases reducing effectiveness
Solution Approach 1:
The harmful leakage phenomenon is extracted and redirected through the pocket opening. Instead of allowing uncontrolled leakage over the sidewalls, the design extracts the excess cooling medium and channels it through a defined path at the trailing edge, converting waste into useful cooling flow.
Solution Approach 2:
Different regions of the blade tip are given different cooling qualities: the main tip area receives cooling from the internal circuit, while the trailing edge corner receives concentrated cooling through the cooling hole and pocket opening. This local differentiation optimizes cooling efficiency in the most critical thermal zone.
3Temperature
If high-velocity cooling medium ejection is used, then convection cooling is improved, but pressure differential requirements increase
Solution Approach 1:
The design merges the internal cooling circuit flow with the tip cavity flow through the cooling hole. The high-velocity jet from the internal circuit combines with the ambient tip cavity atmosphere, creating an effective convection current that enhances cooling without requiring the full pressure differential to act alone over a large area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces thermal loads on difficult-to-cool portions of the turbine blade, including the blade tip, by increasing cooling efficiency and minimizing leakage, thereby reducing or eliminating hot spots.
Implementation Method 1
Ejecting the cooling medium in this manner provides increased cooling to this extreme corner of the airfoil, a notoriously difficult portion of the airfoil to cool, through convection as the cooling medium moves from the cooling hole and out of the pocket opening
Implementation Method 2
ejecting the cooling medium at high velocity from the cooling hole draws (e.g., by creating a pressure differential) cooling medium present in the tip cavity towards and through the pocket opening
Data Source
AI summary
A turbine blade for a gas turbine engine. The turbine blade includes an airfoil having a tip cavity. The tip cavity has a floor bounded by a wall. A pocket opening is formed in the wall proximate a trailing edge of the turbine blade. A passageway communicates cooling medium from an internal cooling circuit to a cooling hole formed in part through the floor and in part through the trailing edge.