Split Doublet Turbine Nozzle Thermal Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Turbine nozzles cast in a doublet configuration experience high stress/strain leading to cracking, necessitating costly repairs or replacement, while singlet configurations reduce stress but are more expensive to produce.
Innovation Solution
Modifying a conventional vane doublet turbine nozzle by splitting one or both of the inner and outer bands along a split line between the airfoils and securing a seal to alleviate thermal stress, effectively mimicking a singlet configuration without the high production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a doublet configuration is used to lower production cost, then manufacturing cost is reduced, but stress/strain increases leading to cracking
Solution Approach 1:
The doublet vane is segmented by introducing a split line that divides the structure into separate sections. This segmentation allows the bands to move independently, reducing stress concentration while maintaining the cost-effective doublet configuration.
Solution Approach 2:
The split line introduces dynamic capability to the previously static doublet structure. The bands can now expand and contract independently in response to thermal cycling, adapting to stress conditions and preventing crack formation.
2Strength
If a singlet configuration is used to reduce stress/strain, then cracking is eliminated, but production cost increases
Solution Approach 1:
Rather than completely redesigning to a singlet configuration, the invention segments the doublet structure strategically. This partial segmentation achieves the stress reduction benefits of singlet design while retaining the manufacturing efficiency of doublet casting.
Solution Approach 2:
The split is applied locally at critical stress zones rather than redesigning the entire structure. This localized modification provides stress relief where needed while maintaining the overall doublet configuration and its manufacturing advantages.
3Device complexity
If the doublet structure is kept intact to maintain structural integrity, then manufacturing is simpler, but thermal stress causes cracking
Solution Approach 1:
The structure is segmented into sections separated by the split line, allowing each section to maintain its integrity while the overall structure gains flexibility to accommodate thermal expansion without cracking.
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
The solution reduces thermally induced stress on airfoils, delaying cracking and extending service intervals by allowing radial movement and using seals and thermal coatings to minimize leakage and stress, thus reducing maintenance costs.
Implementation Method 1
a seal is secured between or adjacent to facing edges of the split line
Implementation Method 2
using seals and thermal coatings to minimize leakage and stress
Data Source
AI summary
A vane doublet for a turbine nozzle includes a radially inner band; a radially outer band; and a pair of airfoils extending between the inner band and the outer band. One of the inner and outer bands is split in a generally axial direction along a split line passing between the pair of airfoils, and a seal is secured between or adjacent to facing edges of the split line.