Multi-lobed Cooling Hole Geometry for Gas Turbine Film Cooling
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Solution Overview
Problem
Conventional cooling techniques for gas turbine engine components face challenges in maintaining efficiency and service life due to high gas path temperatures, leading to increased stress and wear, and existing cooling holes suffer from issues like flow separation and blow-off, which reduce film cooling effectiveness.
Innovation Solution
The implementation of multi-lobed cooling holes with specific inlet, metering, diffusing, and outlet geometries, along with a transition region, to improve film cooling coverage and reduce the likelihood of flow separation, thereby enhancing the spread of cooling fluid across hot surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling holes are used, then cooling function is provided, but flow separation and blow-off occur reducing film cooling effectiveness
Solution Approach 1:
The cooling hole is divided into multiple functional sections: inlet section, metering section, diffusing section, and outlet section. Each section performs a specific function to control the cooling flow progressively, preventing flow separation and blow-off while maintaining effective film cooling along the hot surface.
Solution Approach 2:
The cooling hole transitions from a simple cylindrical structure to a multi-dimensional geometry with varying cross-sectional areas along its length. The diffusing section specifically expands the flow in a controlled manner, adding a dimensional aspect to the cooling hole design that enables better flow attachment and distribution.
2Reliability
If more cooling fluid is used, then film cooling coverage is improved, but engine efficiency is reduced due to increased cooling requirements
Solution Approach 1:
The metering section is designed with specific dimensional parameters (diameter, length, orientation) that precisely control the cooling flow rate and distribution. By optimizing these parameters, the system achieves uniform flow distribution and effective film cooling coverage while minimizing the total cooling fluid required, thus preserving engine efficiency.
3Ease of manufacture
If simple cooling hole geometry is used, then manufacturing is easier, but cooling performance is insufficient due to kidney vortices and thermo-mechanical fatigue
Solution Approach 1:
The transition region is designed to prepare the cooling flow in advance before it exits the hole. This preliminary action smooths the flow profile and reduces turbulence, preventing the formation of harmful kidney vortices downstream and reducing thermo-mechanical fatigue on the hot surface, while still being manufacturable using standard techniques.
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 multi-lobed cooling holes provide improved film cooling effectiveness, reduce flow requirements, and maintain engine efficiency by minimizing detrimental effects such as kidney vortices and thermo-mechanical fatigue, thus extending service life and reliability.
Implementation Method 1
a diffusing section (114) between the metering section and the outlet, wherein the diffusing section expands laterally from the metering section
Implementation Method 2
Cooling holes deliver cooling fluid to cool the outer wall surface
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 at the first wall surface, an outlet at the second wall surface, a metering section extending downstream from the inlet and a diffusing section extending from the metering section to the outlet. The diffusing section includes a first lobe diverging longitudinally and laterally from the metering section, a second lobe adjacent the first lobe and diverging longitudinally from the metering section, a third lobe adjacent the second lobe and diverging longitudinally and laterally from the metering section, and a transition region having an end adjacent the outlet and a portion that extends between the lobes and the outlet. The first and third lobes each include a curved outer portion.