Turbine Blade Tip Baffle for Leakage Recovery
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Solution Overview
Problem
The complex 3D flow fields and tip leakage in gas turbine blades lead to inefficiencies in energy extraction and cooling, making it challenging to design blades that balance turbine efficiency, tip leakage, and tip cooling effectively across varying operating conditions.
Innovation Solution
The introduction of a tip baffle that bifurcates the airfoil tip into two pockets, with one pocket laterally open at its aft end to recover leakage flow and the other laterally closed, enhances energy extraction and reduces tip leakage by providing additional surface area for work performance and improving sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the tip clearance is reduced to minimize leakage, then turbine efficiency is improved, but thermal expansion and contraction of blades and shrouds causes rubbing between rotating tips and stationary shroud
Solution Approach 1:
The tip clearance is divided into two separate clearances by the tip baffle: a first clearance between the pressure side tip and shroud, and a second clearance between the suction side tip and shroud. This segmentation allows independent optimization of each clearance zone, enabling the pressure side to maintain smaller clearance for reduced leakage while the suction side accommodates thermal expansion, thereby preventing rubbing.
2Temperature
If combustion gases leak over the airfoil tips, then tip cooling is improved, but useful work from the leakage flow is reduced
Solution Approach 1:
The tip baffle redirects the leakage gases that would otherwise be lost over the suction side back into the inter-blade flow passages where they can perform useful work. The baffle captures the cooling effect on the pressure side tip while simultaneously recovering the kinetic energy of the leakage flow by redirecting it to interact with subsequent airfoils, thus converting what would be a harmful loss into a beneficial dual-function system.
3Loss of energy
If a tip baffle is introduced to reduce leakage and recover flow, then turbine efficiency is improved, but device complexity increases
Solution Approach 1:
The tip baffle serves multiple functions simultaneously: it acts as a flow redirector to recover leakage gases, a cooling surface for the pressure side tip, a structural element dividing the tip clearance into two zones, and an energy extraction surface. By consolidating these multiple functions into a single component, the overall structural complexity is minimized while achieving comprehensive performance improvement.
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 increases turbine efficiency by capturing and redirecting leakage gases, reducing axial and circumferential leakage, and improving tip cooling, leading to enhanced performance and durability across different operating conditions.
Implementation Method 1
the first pocket being laterally open at its aft end to recover leakage flow
Implementation Method 2
the exposed blade tips which are therefore bathed in the combustion gases which leak thereover during operation, and require suitable cooling thereof
Data Source
AI summary
A turbine blade includes an airfoil having first and second tip ribs extending along the opposite pressure and suction sides thereof. A tip baffle bifurcates the airfoil tip into two pockets, with a first pocket being laterally open at its aft end to recover leakage flow, and a second pocket being laterally closed.