Turbine Nozzle Impingement Cooling With Thermal Flex Elements
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Solution Overview
Problem
Additive manufacturing of turbine nozzles or blades as a single piece introduces thermally driven low cycle fatigue (LCF) challenges due to the integration of airfoil bodies and impingement inserts exposed to different temperature gradients.
Innovation Solution
Incorporation of an impingement cooling structure with elongated thermal flex elements and integral material layers, providing thermal compliance to mitigate thermally induced strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the airfoil body and impingement insert are formed as separate parts that are mechanically coupled together, then each part can undergo its respective thermal cycles without causing significant thermal stress, but the manufacturing cost and assembly complexity increase
Solution Approach 1:
The patent merges the airfoil body and impingement insert into a single integrally formed component through additive manufacturing. This eliminates the mechanical coupling interface between separate parts, thereby eliminating the source of thermal stress while reducing assembly complexity. The single-piece construction allows both components to undergo thermal cycles uniformly without differential expansion or contraction at interfaces.
2Ease of manufacture
If the airfoil body and impingement insert are formed as a single piece through additive manufacturing, then manufacturing cost and assembly complexity are reduced, but thermally driven low cycle fatigue occurs due to differential thermal expansion
Solution Approach 1:
The patent applies local quality by creating a non-uniform wall thickness distribution within the integrally formed component. The impingement insert region has a greater thickness than the airfoil body region, providing additional thermal mass and compliance in the region experiencing the most severe thermal gradients. This localized thickness variation allows differential thermal expansion to occur within the material itself rather than at interfaces, mitigating thermal stress and preventing low cycle fatigue while maintaining the benefits of single-piece manufacturing.
3Reliability
If the impingement insert wall thickness is increased to accommodate thermal expansion, then thermal compliance improves, but the structural integrity and cooling efficiency may be compromised
Solution Approach 1:
The patent implements local quality through spatially varying wall thickness: the impingement insert region has increased thickness for thermal compliance, while the airfoil body regions maintain optimized thinner walls for structural strength and cooling efficiency. This localized thickness variation ensures that thermal expansion accommodation occurs only where needed, without compromising the overall structural integrity or cooling performance of the component.
Solution Approach 2:
The patent applies dynamics by designing the impingement insert with a compliant, flexible structure that can dynamically adjust to thermal expansion and contraction cycles. The increased thickness in the impingement region provides the necessary compliance to absorb thermal stresses, while the overall structure maintains its structural integrity through the integrated design that distributes stresses appropriately throughout the component.
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 enhances the robustness against high cycle fatigue (HCF) while flexibly addressing LCF, enabling cost-effective additive manufacturing despite temperature gradients.
Implementation Method 1
the plurality of elongated thermal flex elements provide thermal compliance for the integrally formed airfoil body and impingement cooling structure. Notably, the flex elements greatly reduce the thermally induced strain on the components exposed to large thermal differences.
Data Source
AI summary
A turbine nozzle or blade includes an airfoil body defined by a concave pressure side outer wall and a convex suction side outer wall that connect along leading and trailing edges and, therebetween, form a radially extending chamber. The airfoil body has an inner surface facing the radially extending chamber. An impingement cooling structure is within the radially extending chamber. The impingement cooling structure includes: a wall spaced from the inner surface of the airfoil body; a plurality of holes defined through the wall; and a plurality of elongated thermal flex elements defined in the wall. Because the nozzle or blade is made by additive manufacturing, the airfoil body and the impingement cooling structure include a plurality of integral material layers.