Gas Turbine Cooling Hole With Lobed Diffuser
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Solution Overview
Problem
Conventional diffusion film cooling holes in gas turbine engines face issues with flow separation and increased cooling fluid requirements, leading to reduced efficiency and increased stress on components due to high gas path temperatures.
Innovation Solution
The implementation of multiple diffusing sections in cooling holes, including a metering section, a first diffusing section, and a second diffusing section with two lobes, which helps in reducing flow separation and improving film coverage by allowing a wider spanwise distribution of cooling air, thereby minimizing the need for excessive cooling fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diffusion film cooling holes are used, then cooling function is provided, but flow separation occurs and excessive cooling fluid is required
Solution Approach 1:
The cooling hole is divided into multiple functional sections: a metering section with constant cross-sectional area, a first diffusing section with expanding area, and a second diffusing section with lobes. This segmentation allows each section to perform its specific function optimally, controlling flow rate and reducing separation
Solution Approach 2:
The second diffusing section introduces a lateral dimension with lobes that spanwise-distribute the cooling air. This dimensional expansion improves film coverage across the surface while reducing the need for excessive cooling fluid quantity
2Reliability
If conventional diffusion film cooling holes are used, then cooling is provided, but flow separation increases
Solution Approach 1:
The cooling hole is divided into multiple functional sections: a metering section with constant cross-sectional area, a first diffusing section with expanding area, and a second diffusing section with lobes. This segmentation allows each section to perform its specific function optimally, controlling flow rate and reducing separation
Solution Approach 2:
The metering section provides partial diffusion with a constant cross-sectional area, creating a controlled intermediate state before the final diffusing section. This partial action prevents excessive flow expansion that would cause separation
3Power
If high gas path temperatures are present, then engine power is maintained, but component stress increases
Solution Approach 1:
Cooling air acts as an intermediary substance, introduced through the multi-section cooling holes to create a protective thermal barrier between the hot gas path and the component structure, reducing thermal stress while maintaining power
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 configuration enhances film cooling effectiveness, reduces flow separation, and maintains engine efficiency while extending the service life of components by optimizing the distribution of cooling fluid across hot surfaces.
Implementation Method 1
a metering section, adjacent to and downstream from the inlet, having a substantially constant cross-sectional area from the inlet to the first diffusing section
Implementation Method 2
a first diffusing section downstream from the metering section, allowing expansion of the cooling air flow
Implementation Method 3
a second diffusing section between the first diffusing section and the outlet, having lobes that diverge laterally and/or longitudinally relative to the metering section
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A gas turbine engine component includes a wall having first and second wall surfaces and a cooling hole extending through the wall. The cooling hole includes an inlet located at the first wall surface, an outlet located at the second wall surface, a metering section extending downstream from the inlet, a first diffusing section extending downstream from the metering section, and a second diffusing section extending downstream from the first diffusing section to the outlet. The second diffusing section includes first and second lobes, each lobe diverging longitudinally and laterally relative to the metering section, and a trailing edge.