Gas Turbine Blade Tip Cooling Passages for Thermal Fatigue and Leakage
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Solution Overview
Problem
Existing gas turbine engine blades face challenges in efficiently converting combustion product expansion to rotation due to temperature and tip clearance issues, with existing cooling technologies not adequately addressing thermal mechanical fatigue and leakage at the blade tips.
Innovation Solution
The implementation of tapered full-length and partial-length wall cooling passages, along with convective cooling pins and investment casting cores, enhances the cooling efficiency of the blade tips, minimizing material and reducing thermal mechanical fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling passages with constant or decreasing cross-section are used, then the cooling structure is simple to manufacture, but the cooling efficiency at the blade tip is insufficient leading to thermal mechanical fatigue
Solution Approach 1:
The cooling passage cross-sectional area is increased along its length from the blade root to the tip, creating a progressively expanding geometry. This parameter change allows more cooling air to reach the blade tip region, improving cooling efficiency where it is most needed without requiring complex manufacturing processes, as the expansion follows the natural blade contour.
Solution Approach 2:
The cooling passage is designed to expand in multiple dimensions (radially outward and circumferentially) as it approaches the blade tip. This multi-dimensional expansion increases the cooling surface area and improves airflow distribution across the blade tip, addressing the thermal fatigue problem while maintaining manufacturability through the investment casting process.
2Productivity
If the blade tip is extended to reduce tip clearance, then the conversion efficiency of combustion expansion to rotation is improved, but thermal leakage at the tip increases
Solution Approach 1:
High-pressure cooling air is channeled through the expanded cooling passages to the blade tip region, creating a protective air barrier that seals the tip clearance gap. This pneumatic sealing effect reduces hot gas leakage past the blade tip, maintaining the efficiency benefits of the extended tip while compensating for the increased leakage tendency.
3Reliability
If cooling air flow is increased to reduce thermal mechanical fatigue, then blade durability is improved, but the complexity of the cooling system increases
Solution Approach 1:
The cooling passages are integrated directly into the blade structure during the investment casting process, merging the cooling system with the blade itself. The passages extend continuously from the blade root through the tip, eliminating the need for separate cooling components or complex assembly procedures, thereby improving durability without proportionally increasing system complexity.
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 solution effectively cools the blade tips, reducing thermal mechanical fatigue and leakage, thereby improving the conversion of combustion energy into rotational energy and enhancing the overall efficiency of the gas turbine engine.
Implementation Method 1
A number of cooling passages extend from the cooling chamber, splits into two a passages, and one passage opens at a rail surface of the turbine blade and the other opens out of a radially and axially extending surface of the blade wall close to the rail surface of the blade
Implementation Method 2
The outer groove which receives the flow of cooling air from the holes tends to trap the air therein so as to form an annular air seal about the outer surface of the squealer tip end wall which impedes leakage of hot gas flow past the squealer tip
Data Source
Figure 1
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AI summary
A gas turbine engine blade includes internal walls defining a blade cooling passage (108) and a tip section (112) at a radially outer end of the blade. The tip section (112) includes a pocket (116) protruding into the tip section (112) from a radially outermost end (120) of the tip section (112) to a pocket floor (124). The blade further includes a pocket wall (128) defined between the pocket floor (124) and the radially outermost end (120) of the tip section (112) and including a tapered wall cooling passage (232).