Turbine Airfoil Trailing Edge Crossover Cooling Circuit
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Solution Overview
Problem
Gas turbine engine turbine blades experience thermal stresses and high temperatures due to complex combustion gas flow distributions, limiting their service life, and existing cooling circuits do not efficiently provide lower temperature cooling to hotspot areas like the outer tip of the trailing edge region.
Innovation Solution
A novel cooling circuit design for turbine buckets with a serpentine internal cooling circuit that includes radially outward and inward passages, featuring crossover passages to direct cooler air to the hotspot areas at the trailing edge, ensuring efficient cooling by bypassing heated sections of the passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling circuits are used in turbine buckets, then cooling coverage is provided, but lower temperature cooling air cannot reach hotspot areas like the outer tip of the trailing edge region
Solution Approach 1:
The cooling circuit is segmented into multiple independent passages: a first radially outwardly directed passage, a second radially inwardly directed passage, and a third radially outwardly directed passage. This segmentation allows cooler air to reach the trailing edge hotspot area through the first passage without being heated by the time it would travel through a single continuous passage, while the second and third passages handle other cooling zones independently.
Solution Approach 2:
Different portions of the airfoil receive cooling air with different temperatures based on their specific thermal requirements. The first passage delivers cooler air to the trailing edge hotspot area, while other passages deliver air at different temperatures to their respective zones, matching the local heat loads to the local cooling capability.
2Temperature
If cooling air flows through long radial passages, then cooling coverage is extended, but the cooling air temperature increases due to heat absorption from the airfoil
Solution Approach 1:
The long radial cooling path is divided into multiple shorter passages. The first radially outwardly directed passage delivers cool air to the trailing edge area in a shorter distance, preventing excessive heat absorption. The second and third passages handle other portions of the airfoil, each with optimized lengths for their specific cooling zones.
3Reliability
If compressor air is used for cooling, then cooling effectiveness is improved, but efficient utilization of the cooling air is challenging to achieve
Solution Approach 1:
The cooling system matches the temperature and flow characteristics of the compressor air to the specific thermal requirements of different airfoil regions. The first passage delivers cooler air to the high-heat-load trailing edge hotspot, while other passages distribute air to zones with different heat loads, maximizing the utilization efficiency of the available compressor cooling air.
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 stresses by preferentially cooling the targeted hotspot areas, prolonging the service life of turbine blades by efficiently utilizing compressor air and maintaining lower temperatures in critical regions.
Implementation Method 1
Cooling air flowing radially outwardly in a passage adjacent the trailing edge is channeled by multiple crossover holes into a cavity extending along the trailing edge
Implementation Method 2
The airfoils are typically manufactured from superalloy cobalt- or nickel-based materials having sustained strength under high temperature operation
Data Source
AI summary
A cooling circuit for a turbine bucket having an airfoil portion includes a trailing edge cooling circuit portion provided with a first radially outwardly directed inlet passage intermediate leading and trailing edges of the airfoil portion of the bucket, extending from a platform portion of the bucket to a location adjacent a radially outer tip of the bucket, and connecting to a second radially inwardly directed passage extending from a location adjacent the radially outer tip to a location adjacent the platform portion. The second radially inwardly directed passage connects to a third trailing edge region passage, and a plurality of crossover passages connect a radially outer half of the second radially inwardly directed passage to a radially outer half of the third trailing edge region passage.