Gas Turbine Blade Platform Shell Asymmetry for Centrifugal Load

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Solution Overview

Problem

Gas turbine engine blades made from ceramic matrix composites face challenges in transmitting centrifugal loads due to low interlaminar properties, leading to potential bond loss and increased structural loads, which can cause distortions and further load increases.

Innovation Solution

The design incorporates a platform shell with a flared neck region that intersects the platform region at a varying thickness perimeter, positioning the center of gravity outboard of the contact width to create a net moment that rotates the platform shell platform region toward the inner ply layer group, ensuring the neck region operates in compression and minimizing rolling moments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If the platform shell is designed with a traditional symmetric structure, then the manufacturing is simpler, but the centrifugal load transmission is insufficient due to low interlaminar properties

Engineering Contradiction:

Improvecentrifugal load transmissionVSAvoidplatform shell structure

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The patent applies asymmetry by positioning the center of gravity outboard of the contact width center point, creating an asymmetric mass distribution. This generates a beneficial rolling moment that rotates the platform shell platform region toward the inner ply layer group, ensuring the neck region operates in compression to improve centrifugal load transmission.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by varying the thickness of the platform shell at different locations. The platform shell has a first thickness inboard of the neck region perimeter and a second thickness outboard of the neck region perimeter, with the first thickness being greater than the second thickness. This localized thickness variation optimizes stress distribution and load transmission in critical regions.

Inventive Principle:

Principle #3Local quality

2Reliability

If the platform shell neck region operates in tension, then the structure appears simpler, but bond loss occurs leading to distortions and cascading structural load increases

Engineering Contradiction:

Improvebond integrityVSAvoidinterlaminar stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies preliminary anti-action by designing the platform shell with an outboard center of gravity that creates a pre-compression rolling moment. This preliminary compressive action counteracts tensile stresses that would otherwise develop in the neck region, preventing bond loss and maintaining bond integrity between the platform shell and inner ply layer group.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The patent inverts the conventional approach by ensuring the neck region operates in compression rather than tension. The outboard center of gravity creates a rolling moment that rotates the platform shell to place the neck region in compression, reversing the typical stress state and thereby improving reliability by preventing bond failure.

Inventive Principle:

Principle #13The other way round (Inversion)

3Stress or pressure

If the platform shell center of gravity is positioned at the center point of contact width, then the structure is balanced, but rolling moments are not minimized leading to increased stress concentrations

Engineering Contradiction:

Improvestress concentrationVSAvoidplatform shell balance

Core Design Contradiction:

Stress or pressureVSStability of the object's composition

Solution Approach 1:

The patent deliberately introduces asymmetry by positioning the center of gravity outboard of the contact width center point. This asymmetric positioning creates a controlled rolling moment that minimizes stress concentrations in the neck region by ensuring compressive operation, while the overall structural balance is maintained through the vortex shell geometry and support on the inner ply layer group.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS11280202B2Balanced composite root region for a blade of a gas turbine engine

Publication Date: 2022.03.22 RTX CORP

AI summary

A rotor blade for a gas turbine engine including an inner ply layer group includes a flared region and an airfoil region, a neck region between the flared region and the airfoil region; and a platform shell that comprises a platform shell root region, a platform shell platform region, and a platform shell neck region between the platform shell root region and the platform shell platform region, the platform shell root region sheathes the flared region, and the platform shell neck region flares outwardly away from the neck region to intersect the platform shell platform region at a platform shell neck region perimeter around an airfoil opening perimeter.