Composite Turbine Nozzle Support Frame Assembly
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Solution Overview
Problem
Composite turbine nozzle segments made of plies face challenges with shear-based support loads, leading to inter-laminar tension and potential delamination due to uneven load distribution and relative movement between supports, which is detrimental to their structural integrity.
Innovation Solution
A support frame assembly that engages a hook on the composite nozzle segment with a rail contact surface normal to the plies, allowing axial load transfer through a central body and frame pin, and utilizing a clamped assembly with a load spreader to distribute loads compressively, reducing shear stress between plies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If composite turbine nozzle segments are simply supported at both inner and outer ends, then the nozzle segment can rock and slide relative to supports to maintain contact, but concentrated stresses occur in the segment due to high pressure drop across contact areas
Solution Approach 1:
A support rail is introduced as an intermediary element between the composite nozzle segment and the support structure. The rail features a chordal seal surface that contacts the nozzle band, distributing the support loads across a larger area rather than concentrating them at discrete points. This intermediary structure allows the nozzle to rock and slide while maintaining distributed load transfer, preventing stress concentration in the composite material.
2Shape
If arc shaped contact between band and support is used, then the nozzle can conform to the annulus, but uneven load distribution occurs and large leakage areas are created
Solution Approach 1:
The support rail introduces an asymmetric contact geometry where a chordal (straight) seal surface contacts the arcuate nozzle band. This asymmetric arrangement allows the nozzle to maintain its arcuate shape for annulus conformance while the chordal contact surface provides uniform load distribution. The mismatch between the arcuate nozzle geometry and the straight rail contact surface creates a stable, distributed contact pattern that prevents both uneven loading and excessive leakage.
3Adaptability or versatility
If a chordal hinge or chordal seal is used in metal turbine nozzles, then the vane segment can rock without changing load distribution or increasing leakage, but in composite nozzles this results in shear loads between plys and inter-laminar tension
Solution Approach 1:
The support rail is specifically designed to interface with composite material construction. By providing a broad, distributed contact surface rather than a line contact, the rail transfers loads in a manner that avoids shear stresses between composite plies and inter-laminar tensions. The rail's geometry and contact approach are optimized for composite materials, allowing rocking motion while maintaining load paths that align with the composite structure's strength characteristics.
Data Source
AI summary
A support frame includes a rail engaging a hook of a composite article having plys. The rail included a rail contact surface generally conformal to and contacting a hook contact surface of the hook. The rail and hook contact surfaces being substantially normal to the plys beneath the hook contact surface. One embodiment of the article is a composite nozzle segment including one or more airfoils extending radially between arcuate radially outer and inner band segments having plys curved about a centerline axis and the rail engages a hook of the radially inner band segment. The hook and the rail may be straight or arcuate. The frame includes a central body extending axially aftwardly from the rail to an aft frame flange. A frame pin may be mounted on the frame, engage the inner band segment or one of the airfoils, and may extend into a cavity in the airfoil.