Dendritic Cooling Passage Structure for Gas Turbine Blades
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Solution Overview
Problem
Existing cooling arrangements for gas turbine engine aerofoils, such as fractal passage networks, are prone to blockages and manufacturing difficulties due to structural weaknesses and complexity, which hinder effective heat extraction and structural integrity.
Innovation Solution
A dendritic cooling passage structure with cascaded pyramidal cells and a flow-restricting throat is used, allowing for tailored heat extraction and easy casting with a self-supporting ceramic core, enhancing both cooling efficiency and structural strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fractal passage networks are used for cooling, then heat extraction capability is improved, but the system is prone to blockages and manufacturing difficulties
Solution Approach 1:
The cooling passage network is segmented into multiple independent feed passages, each serving specific regions. This segmentation ensures that a blockage in one passage does not propagate to other regions, maintaining cooling reliability while preserving heat extraction capability through the distributed network architecture.
Solution Approach 2:
Different regions of the blade are provided with different cooling passage configurations tailored to their specific thermal requirements. High-heat-flux regions receive denser passage networks while lower-heat-flux regions have sparser configurations, optimizing heat extraction where needed without compromising overall system reliability.
2Temperature
If fractal passage networks are used for cooling, then heat extraction capability is improved, but manufacturing difficulty increases
Solution Approach 1:
The complex fractal cooling network is divided into multiple simpler feed passages that can be manufactured independently using standard casting techniques. This segmentation allows each passage to be created with conventional methods while the assembled network achieves the desired fractal cooling performance.
Solution Approach 2:
The design accepts that some passage complexity must be simplified for manufacturing, using adequate but not overly complex passage configurations that can be reliably produced with standard industrial methods, sacrificing some optimal heat extraction performance for manufacturability.
3Temperature
If porous material is used for transpiration cooling, then cooling effectiveness is improved, but structural strength decreases
Solution Approach 1:
The blade incorporates controlled porous regions in specific high-heat-flux areas to enable transpiration cooling, while maintaining dense solid material in structural load-bearing regions. This selective porosity provides cooling effectiveness where thermal loads are highest without compromising overall structural strength.
Solution Approach 2:
Different material properties are applied to different regions: porous material in thermal management zones and dense solid material in structural zones. This local differentiation allows the blade to achieve both cooling effectiveness and structural strength in their respective functional areas.
4Temperature
If cooling passages are made long to assist heat transfer, then heat extraction is improved, but pressure loss increases
Solution Approach 1:
The cooling passages utilize three-dimensional spatial arrangements and cross-flow configurations between multiple passages rather than simple linear paths. This dimensional complexity allows longer effective heat transfer paths while maintaining shorter pressure-driven flow paths, reducing pressure loss while improving heat extraction efficiency.
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 dendritic structure provides improved internal and film-cooling effectiveness, reduces blockage risks, and simplifies manufacturing by using a stable, flexible ceramic core, increasing convective efficiency and structural integrity of the blade.
Implementation Method 1
All fluid cooling systems operate by transferring heat from the blade into a flow of cooling fluid that is constantly refreshed. Several of the most frequently used systems utilise convective cooling by internal cooling passages formed in component walls
Implementation Method 2
film cooling by exuding cooling air onto the external heated surface
Implementation Method 3
impingement cooling using jets of cooling air directed at the internal surface of the heated part
Implementation Method 4
The walls of the blade are constructed from a porous material and the cooling air is injected through the pores in the interior surface and flows through the material onto the exterior surface where it forms a boundary surface film
Data Source
AI summary
A wall cooling arrangement comprising on one side of a wall a multiplicity of cooling fluid inlet apertures and on the opposite of the wall a multiplicity of cooling fluid exit apertures, and in the body of the wall linking said inlet and exit apertures a network of multiply branched cooling passages. Flow of cooling fluid through a network is controlled by a throat positioned either at or close to the inlet to the passage network or at a location part way through the network, in which case there may be a plurality of inlet apertures feeding through a single throat to a plurality of outlet apertures.