Airfoil Tip Flag Cooling Circuit for Low-Flow Tip Heat Transfer
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Solution Overview
Problem
Existing gas turbine engine airfoils face challenges in achieving high internal heat transfer and cooling effectiveness, particularly in the tip region, where thermal mechanical fatigue cracks occur due to poor film cooling and low flow rates in serpentine cooling channels.
Innovation Solution
A cooling circuit design incorporating a serpentine channel with a dedicated tip flag channel and a metering orifice that connects radially and axially extending passages, enhancing heat transfer by directing cooling fluid flow away from the tip region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a serpentine cooling channel is used in the airfoil, then the cooling coverage is improved, but the internal heat transfer in the last passage is reduced due to flow separation and low flow rate
Solution Approach 1:
The cooling circuit is segmented into a serpentine channel and a separate tip flag channel, with the tip flag channel specifically addressing the heat transfer deficiency in the last passage of the serpentine channel by providing an additional cooling path to the tip region
Solution Approach 2:
The tip flag channel acts as an intermediary cooling path that connects to the last passage of the serpentine channel, mediating the cooling fluid flow to improve heat transfer in regions where the serpentine channel alone is insufficient
2Temperature
If cooling fluid flow is increased in the tip region, then tip temperatures are reduced, but thermal mechanical fatigue cracks occur due to mismatch between outboard airfoil wall thickness and tip cap thickness
Solution Approach 1:
The tip flag channel provides localized cooling specifically to the tip region, allowing increased cooling fluid flow precisely where needed without subjecting the entire airfoil structure to high thermal stresses that could cause fatigue cracks
3Area of stationary object
If the serpentine channel length is increased to improve cooling coverage, then more areas are cooled, but flow rate and internal heat transfer are reduced due to extended travel distance
Solution Approach 1:
The cooling circuit is divided into the serpentine channel for general cooling coverage and the tip flag channel for targeted tip region cooling, allowing the serpentine channel to maintain adequate flow rate while the tip flag channel addresses the tip region that would otherwise require excessive serpentine length
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
The design increases internal heat transfer and reduces tip temperatures, improving the lifespan of airfoils by minimizing thermal mechanical fatigue and maintaining efficient cooling.
Implementation Method 1
Hollow airfoils of a turbine section include internal cooling circuits or cores configured to achieve a higher cooling effectiveness and to reduce airfoil metal temperatures
Implementation Method 2
A blade core design that reduces cooling air heat pick-up and increases the internal heat transfer coefficient
Data Source
AI summary
A cooling circuit of an airfoil for a gas turbine engine includes a serpentine channel having a plurality of fluidly connected radially extending flow passages and a tip flag channel disposed adjacent to the serpentine channel. The tip flag channel includes a first tip flag passage extending radially and a second tip flag passage extending axially from a terminal end of the first tip flag passage, the second tip flag passage disposed radially outward of the serpentine channel. The second tip flag passage is in direct fluid communication with each of the first tip flag passage and a final passage of the serpentine channel.