Airfoil Shielding CMC Rib From Cooling Air

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Solution Overview

Problem

Ceramic matrix composite (CMC) airfoils in gas turbine engines face challenges due to high thermal gradients and thermally induced stresses, which can be exacerbated by cooling methods, affecting durability.

Innovation Solution

A shield is disposed in the internal cavity of the airfoil, partially or fully enclosing the rib to shield it from cooling air, using a spring clip for securement, thereby reducing thermal gradients and stresses on the CMC rib.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If cooling air is introduced into the internal cavity to cool the airfoil, then temperature resistance is improved, but thermal gradients and thermally induced stresses increase, worsening durability

Engineering Contradiction:

Improvetemperature resistanceVSAvoiddurability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The shield is positioned to selectively block cooling air from contacting the rib while allowing the airfoil wall to be cooled. This creates different thermal conditions in different locations - the wall experiences cooling while the rib is protected from thermal gradients, resolving the contradiction between temperature resistance and durability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The shield acts as an intermediary element between the cooling air and the rib. It mediates the thermal interaction by blocking the cooling air from directly contacting the rib, thereby preventing the development of harmful thermal gradients while still allowing the cooling system to function for the airfoil wall

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the rib is exposed to cooling air to maintain structural integrity, then strength is improved, but thermal gradients increase, worsening reliability

Engineering Contradiction:

Improvestructural integrityVSAvoiddurability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The shield creates localized thermal protection for the rib while maintaining overall structural integrity. The rib remains strong because it is protected from the thermal shocks and gradients that would otherwise compromise its strength, thus simultaneously achieving both strength and reliability

Inventive Principle:

Principle #3Local quality

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 shield maintains the rib at lower thermal gradient levels relative to the airfoil wall, enhancing durability by reducing thermally induced stresses and maintaining structural integrity.

Implementation Method 1

A shield is disposed in the internal cavity and at least partially enclosing the rib to shield the rib from the cooling air

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 2

The shield includes a spring clip that pinches onto the rib, securing the shield to the rib

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP3789585B1Airfoil with metallic shield

Publication Date: 2023.06.21 RTX CORP

Figure 1~2A
Figure 2B~6
Figure 3~10

AI summary

A gas turbine engine airfoil (60) includes an airfoil section (61) that has an airfoil wall (62) and a rib (70) that are formed of a ceramic matrix composite ("CMC"). The airfoil wall (62) circumscribes an internal cavity (66) for receiving cooling air. The airfoil wall (62) defines leading and trailing ends (62a, 62b) and first and second sides (62c, 62d) that join the leading and trailing ends. The rib (70) connects the first and second sides (62c, 62d). A metallic shield (72) is disposed in the internal cavity (66) and at least partially encloses the rib (70) to shield the rib (70) from the cooling air.