Gas Turbine Rotor Blade Midspan Shroud Wear Reduction
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Solution Overview
Problem
Conventional midspan shrouds in gas turbine rotor blades face issues with rapid wear due to misalignment, leading to harmful tension and shear forces, and aerodynamic losses, while also increasing the risk of component failure under high mechanical loads.
Innovation Solution
The design incorporates a midspan shroud with wing-like projections that include pressure and suction wings, configured to form an interface with neighboring blades, featuring a predetermined offset to ensure proper alignment and reduce stress, and a downstream narrowing step to maintain aerodynamic alignment during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional midspan shrouds are used with contact wear surfaces to mechanically engage neighboring airfoils, then structural stability and vibration damping are improved, but the contact surfaces wear quickly due to misalignment causing tensional and shear forces
Solution Approach 1:
The patent applies preliminary action by pre-positioning the contact surface at a location and orientation that anticipates the misalignment tendency. The contact surface is positioned on the inboard portion of the shroud at a specific angle relative to the shroud surface, preparing it in advance to accommodate the expected misalignment during operation and prevent harmful tensile forces from developing
Solution Approach 2:
The patent changes the geometric parameters of the contact surface by defining its position at a specific distance from the shroud surface and its orientation at a specific angle. This parameter optimization ensures that the contact surface maintains proper engagement despite misalignment, converting the harmful tensile and shear forces into manageable contact pressures
2Stress or pressure
If the shroud is positioned lower on the airfoil (midspan) to reduce stress on the rotor blade, then the pull loads on the blade base are reduced, but misalignment causes rapid wear of contact surfaces
Solution Approach 1:
The patent applies local quality by concentrating the contact function at a specific localized area on the inboard portion of the shroud. Rather than relying on the entire shroud surface, a specific contact zone is created with optimized geometry to handle the misalignment, allowing the rest of the shroud to maintain its stress-reducing position while the localized contact area prevents wear
3Adaptability or versatility
If non-integral pads are affixed to the midspan shroud to provide contact surfaces, then mechanical engagement with neighboring blades is enabled, but harmful wear quickly degrades the component due to tension and shear forces
Solution Approach 1:
The patent merges the contact surface function directly into the shroud structure itself rather than using separate non-integral pads. The contact surface is formed as an integral part of the shroud, combining the structural support function with the contact function, which eliminates the harmful wear that occurs with separate pads subjected to tension and shear forces
Data Source
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AI summary
A rotor blade 16 for a gas turbine 10 configured for use within a row of samely configured rotor blades. The rotor blade may include an airfoil 25 defined between pressure 26 and suction 27 faces and a midspan shroud 75. The midspan shroud 75 may include pressure 76 and suction 77 wings. The pressure wing 76 and suction wing 77 of the midspan shroud 75 may be configured so to cooperatively form an interface 85 between neighboring ones of the rotor blades 16 within the row of samely configured rotor blades 16. The interface 85 may include: a pressure wing contact face 86 disposed on the pressure wing 76 that opposes across a gap 88 a suction wing contact face 87 disposed on the suction wing 77; and a predetermined offset 98 between the pressure wing contact face 86 and suction wing contact face 87. The predetermined offset 98 may be configured for desirably aligning the contact faces 86, 87 when an expected operating condition closes of the gap 88.