Gas Turbine Stator Vane Scarf Angle Circumferential Locking
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Solution Overview
Problem
Existing gas turbine engines face challenges in thermal expansion management, leading to rotational movement of stator vanes within the compressor casing, which can result in axial locking issues and increased manufacturing costs due to the need for combining multiple vanes to restrict rotation.
Innovation Solution
The solution involves a casing assembly with stator vanes having a non-zero scarf angle between 12 and 30 degrees, specifically between 18 and 21 degrees, and a single aerofoil extending from the platform, which is pivotally connected to the compressor casing, allowing for circumferential locking without axial locking, thereby managing thermal expansion and reducing manufacturing complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If stator vanes are spaced apart using circumferential locking method with axial gap, then thermal expansion is allowed, but rotational movement occurs within the slot
Solution Approach 1:
The invention changes the geometric parameter of the stator vane platform by introducing a non-zero scarf angle (between 12-30 degrees, preferably 18-21 degrees). This angular parameter modification enables the platform to lock circumferentially against the slot edges while maintaining axial clearance for thermal expansion, thus resolving the contradiction between allowing thermal expansion and preventing rotational movement.
2Stability of the object's composition
If multiple vanes are combined together to increase circumferential width, then rotational locking is improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of combining multiple vanes to achieve rotational locking (the conventional approach), the invention inverts the solution by modifying the geometry of a single vane platform with a non-zero scarf angle. This single-vane approach achieves the same rotational locking effect that previously required multiple combined vanes, thereby reducing manufacturing complexity while maintaining stability.
3Stability of the object's composition
If multiple vanes are combined together to increase circumferential width, then rotational locking is improved, but manufacture time increases
Solution Approach 1:
The invention segments the functional requirements: a single stator vane platform with a non-zero scarf angle performs the rotational locking function that previously required multiple vanes working together. This segmentation of the locking function into a single optimized component reduces assembly time and manufacturing complexity while maintaining the necessary circumferential locking capability.
Data Source
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AI summary
There is disclosed a casing assembly for a gas turbine engine 10. The casing assembly comprises a casing 24 comprising a slot 32 defined by a front surface and a rear surface, the front surface and the rear surface being spaced apart by an axial casing gap. The casing assembly further comprises a plurality of stator vanes 30 each comprising a platform 42 and at least one aerofoil 38, 40 extending from the platform, the platform being received within the slot and having an axial length and a circumferential length. The circumferential lengths of the platforms define a total circumferential length which is less than the circumference of the casing at an outer radial surface of the platforms and so defines a circumferential clearance. The axial length of each of the platforms is less than the axial casing gap and so defines an axial clearance. The circumferential and axial clearances allow the platforms of the stator vanes to rotate within the slot, with rotation of the platforms from an unrotated position reducing the circumferential and axial clearance. The front and rear surfaces of the casing and the platforms of the stator vanes are configured such that rotation of the platforms from the unrotated position entirely consumes the circumferential clearance so that adjacent platforms abut against one another and prevent further rotation of the platforms while maintaining an axial clearance. There is also disclosed a method of manufacturing a casing assembly for a gas turbine engine.