Flared Tip Turbine Blade Leakage Control
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Solution Overview
Problem
The complex 3D flow fields over turbine blade tips in gas turbine engines lead to inefficiencies in energy extraction, tip leakage, and cooling, making it challenging to optimize turbine blade design for efficiency and longevity.
Innovation Solution
The introduction of flared ribs on the pressure and suction sides of the turbine blade tips, with the suction side rib flared outwardly, creates additional overhangs to restrict gas flow and reduce leakage, while maintaining aerodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the tip clearance between blade tips and turbine shrouds is reduced to minimize gas leakage, then energy loss is reduced, but thermal expansion and contraction of blades and shrouds causes rubbing between rotating tips and stationary shroud
Solution Approach 1:
The squealer tip ribs extend the blade tip in the radial dimension, creating an overhang structure that separates the tip floor from the shroud. This dimensional extension allows the blade to accommodate thermal expansion in the radial direction without contacting the shroud, while maintaining a reduced clearance between the tip floor and shroud to minimize gas leakage.
Solution Approach 2:
The squealer tip ribs are pre-formed as integral structures on the blade tips during manufacturing. This preliminary structuring provides built-in thermal expansion compensation capability before the blade enters service, allowing the blade to safely expand and contract without risking tip rubbing during operation.
2Reliability
If squealer tip ribs are added to protect the tip floor and internal cooling circuit from tip rub, then blade reliability is improved, but the complexity of combustion gas flow field increases affecting turbine efficiency and flow leakage
Solution Approach 1:
The squealer tip ribs are implemented as localized structures only at the blade tips where protection is needed, rather than modifying the entire blade structure. The ribs are positioned specifically to create the protective overhang while minimizing interference with the main combustion gas flow paths through the turbine stages.
Solution Approach 2:
The squealer tip ribs feature curved and filleted transitions between the rib surfaces and the blade airfoil surfaces. These smooth curved transitions reduce flow separation and minimize disturbances to the combustion gas flow field, thereby reducing the negative impact on turbine efficiency while maintaining the protective function.
3Ease of manufacture
If the blade airfoils have thin sidewalls formed by casting, then manufacturing efficiency is improved, but cooling requirements become more critical for ensuring long useful life during operation
Solution Approach 1:
The squealer tip ribs enclose a tip cavity that contains the internal cooling circuit within the blade structure. This nested arrangement integrates the cooling system within the protective rib structure, allowing efficient cooling of the thin-walled airfoil while maintaining the manufacturing advantages of casting. The tip floor acts as a containment structure for the cooling passages.
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 flared ribs significantly reduce tip leakage and improve aerodynamic efficiency, with the suction side flare being particularly effective in reducing leakage without adversely affecting turbine efficiency.
Implementation Method 1
The introduction of flared ribs on the pressure and suction sides of the turbine blade tips, with the suction side rib flared outwardly, creates additional overhangs to restrict gas flow and reduce leakage
Data Source
AI summary
A turbine blade includes an airfoil terminating in a tip. The tip includes a first rib conforming with a concave pressure side of the airfoil, and a second rib conforming with a convex suction side of the airfoil. The second rib is flared outwardly from the suction side.