Multi-Lobed Cooling Holes for Gas Turbine Blades
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Solution Overview
Problem
Gas turbine engine components exposed to hot working fluid flow face increased cooling loads due to higher gas path temperatures, leading to reduced service life and efficiency, as traditional cooling methods require significant cooling fluid flow, which can decrease engine efficiency.
Innovation Solution
The method involves forming multi-lobed cooling holes with improved metering and diffusive geometries using electrical discharge machining (EDM) to reduce flow requirements and enhance the spread of cooling fluid across hot surfaces, thereby minimizing flow separation and corner effects, and using EDM to create specific geometries in the cooling holes that optimize the delivery of cooling fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional cooling methods are used in gas turbine engine components, then cooling effect is achieved, but cooling fluid flow requirements increase significantly
Solution Approach 1:
The cooling hole is divided into multiple functional sections: metering section with restricted flow area, diffusing section with expanding cross-section, and outlet section. This segmentation allows the cooling fluid to be metered, diffused, and distributed efficiently, reducing the total quantity of cooling fluid needed while maintaining effective cooling
Solution Approach 2:
Different sections of the cooling hole are given different geometric properties optimized for their specific function: the metering section has a restricted flow area for flow control, the diffusing section has an expanding cross-section for fluid distribution, and the outlet has specific orientation. This local optimization of geometry ensures each section performs its function efficiently, reducing overall cooling fluid requirements
2Quantity of substance
If traditional cooling holes are used, then cooling fluid delivery is achieved, but flow separation and corner effects occur reducing efficiency
Solution Approach 1:
The diffusing section is designed with curved surfaces and smooth transitions instead of sharp corners, eliminating flow separation. The rounded geometry promotes smooth fluid flow through the cooling hole, preventing energy losses associated with flow separation and corner effects while maintaining effective cooling fluid delivery
3Manufacturing precision
If multi-lobed cooling holes with optimized geometry are formed using EDM, then cooling fluid distribution is improved, but manufacturing complexity increases
Solution Approach 1:
Traditional mechanical drilling or machining methods are replaced with electrical discharge machining (EDM). EDM uses electrical discharges to erode material and form the complex multi-lobed cooling hole geometry, enabling precise control of the metering section, diffusing section, and outlet geometry without the limitations of mechanical tool access, thereby achieving high manufacturing precision for complex geometries
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 approach reduces the need for cooling fluid flow while maintaining or increasing engine efficiency by effectively distributing cooling fluid across components, thus extending service life and improving reliability.
Implementation Method 1
forming a metering section extending from the diffusing section to an inlet by electrical discharge machining
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A method for forming a cooling hole extending from an inlet on a first surface of a wall to an outlet on a second surface of the wall includes forming a diffusing section of the cooling hole, and a trailing edge on the outlet by electrical discharge machining, and forming longitudinal lobes in the diffusing section. The metering section extends from the inlet on a first surface of the wall towards the second surface of the wall. The diffusing section extends from the outlet to one end of a metering section located between the inlet and the outlet. The outlet is substantially linear or convex at the trailing edge and the lobes are separated by longitudinal ridges.