Gas Turbine Nozzle Fillet Design for Stress Reduction
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Solution Overview
Problem
Stress, particularly thermal stress, on the thinned trailing edge portion of gas turbine nozzle segments leads to reduced lifespan due to undesirable issues at the connection to platforms, affecting the aerodynamic performance and durability.
Innovation Solution
The nozzle segment design incorporates a taller trailing edge fillet blending into the inner platform, with a height greater than the inner fillet, and a bowed trailing edge structure to maintain throat dimensions, reducing stress and secondary flows, and increasing the cross-sectional area at junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the trailing edge portion is thinned to improve aerodynamic performance, then the aerodynamic efficiency is improved, but the stress concentration and cracking risk increase significantly
Solution Approach 1:
The patent applies different fillet heights at different locations: a first fillet height at the trailing edge connection to the inner platform, and a second fillet height at the trailing edge connection to the outer platform. This local differentiation allows the trailing edge to maintain thinning for aerodynamic efficiency while providing enhanced stress distribution through varied fillet dimensions at critical connection points.
Solution Approach 2:
The fillets are designed with predetermined heights during the manufacturing stage to preemptively address stress concentration issues. The first fillet height is specifically designed to be greater than the second fillet height, creating a stress-distributing geometry before thermal stress occurs during operation, thereby preventing cracking in advance.
2Ease of manufacture
If a standard fillet design is used to simplify manufacturing, then the manufacturing complexity is reduced, but the stress distribution and component lifespan are significantly reduced
Solution Approach 1:
The patent specifies different fillet heights at different locations along the trailing edge. The first fillet height at the inner platform connection is greater than the second fillet height at the outer platform connection, creating localized stress distribution optimization that extends component lifespan without requiring complex manufacturing processes.
3Strength
If the fillet height is increased to reduce stress concentration, then the stress distribution is improved, but the cross-sectional area and aerodynamic performance are reduced
Solution Approach 1:
The patent applies fillet height differentiation strategically: the first fillet height is greater than the second fillet height, concentrating the stress-mitigating geometry where it is most needed at the inner platform connection, while maintaining smaller fillet dimensions elsewhere to preserve aerodynamic efficiency.
Solution Approach 2:
The patent applies fillet enhancement partially rather than uniformly across the entire trailing edge. By concentrating the greater fillet height at the critical inner platform connection and using a smaller second fillet height elsewhere, the design achieves sufficient stress resistance without the excessive material addition that would compromise aerodynamic performance.
Data Source
AI summary
A nozzle segment for a gas turbine engine has a turbine airfoil bound on a first side by an arcuate inner endwall having an inner platform and on a second side by an arcuate outer endwall having an outer platform. The airfoil extends outwardly from the inner platform toward the outer platform. The airfoil body includes opposed pressure and suction sidewalls extending between a leading edge and a trailing edge of the airfoil body. The airfoil body includes a first trailing edge fillet blending into the inner platform at a trailing edge of the airfoil body.