Stepped Spanwise Thickness Airfoil for Gas Turbine Blades

Solution Overview

Problem

Gas turbine engine airfoils deform at high operating speeds, leading to 'closing' at the leading edges, which restricts airflow and increases blade root stresses due to centrifugal loads, causing imbalance and potential air flow restrictions.

Innovation Solution

The airfoil design features a spanwise distribution of maximum thicknesses with a stepped or marked transition, decreasing from the root to the tip, comprising three sections with distinct slope changes to reduce bending stresses and maintain aerodynamic efficiency, characterized by a first portion with a gentle slope, a second portion with a higher slope, and a third portion with an even higher slope, distributing weight and thickness to alleviate stress and improve airflow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the airfoil has a uniform thickness distribution from root to tip, then the manufacturing is simpler, but the blade root stresses increase due to centrifugal loads causing closing at the leading edges

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidblade root stress resistance

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The airfoil employs a stepped spanwise thickness distribution where different sections have different thickness characteristics. The root portion has greater thickness to resist bending stresses from centrifugal loads, while the tip portion has reduced thickness. This non-uniform distribution optimizes structural strength at each location rather than applying a uniform thickness throughout the span.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The airfoil span is divided into multiple sections with distinct thickness characteristics. The stepped distribution creates discrete segments along the span, each optimized for its specific structural requirements. This segmentation allows the root section to handle higher stresses while the tip section is optimized for aerodynamic performance.

Inventive Principle:

Principle #1Segmentation

2Strength

If the airfoil thickness decreases gradually from root to tip, then the structural integrity is maintained, but the airflow restriction increases due to closing at the leading edges

Engineering Contradiction:

Improvestructural integrityVSAvoidairflow efficiency

Core Design Contradiction:

StrengthVSProductivity

Solution Approach 1:

The airfoil employs a stepped spanwise thickness distribution where different sections have different thickness characteristics. The root portion has greater thickness to resist bending stresses from centrifugal loads, while the tip portion has reduced thickness. This non-uniform distribution optimizes structural strength at each location rather than applying a uniform thickness throughout the span.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The airfoil span is divided into multiple sections with distinct thickness characteristics. The stepped distribution creates discrete segments along the span, each optimized for its specific structural requirements. This segmentation allows the root section to handle higher stresses while the tip section is optimized for aerodynamic performance.

Inventive Principle:

Principle #1Segmentation

3Strength

If the airfoil has a stepped spanwise thickness distribution, then the blade root stresses are reduced and airflow is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improveblade root stress resistanceVSAvoidairfoil geometry complexity

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The airfoil span is divided into multiple sections with distinct thickness characteristics. The stepped distribution creates discrete segments along the span, each optimized for its specific structural requirements. This segmentation allows the root section to handle higher stresses while the tip section is optimized for aerodynamic performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The airfoil employs discrete changes in the thickness parameter along the span rather than continuous variation. This stepped approach modifies the geometric parameters at specific locations to optimize performance while remaining manufacturable through standard aerospace fabrication techniques.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10718215B2Airfoil with stepped spanwise thickness distribution

Publication Date: 2020.07.21 PRATT & WHITNEY CANADA CORP

AI summary

An airfoil for a gas turbine engine comprises at least three successive sections defined between a root and a tip. A first decrease of maximum thickness-to-chord ratios defined by a difference between a maximum thickness-to-chord ratio at the root and a maximum thickness-to-chord ratio at a first spanwise position, a second decrease of the maximum thickness-to-chord ratios defined by a difference between the maximum thickness-to-chord ratio at the first spanwise position and a maximum thickness-to-chord ratio at a second spanwise position, a third decrease of the maximum thickness-to-chord ratios defined by a difference between the maximum thickness-to-chord ratio at the second spanwise position and a maximum thickness-to-chord ratio at the tip, the second decrease being greater than the corresponding first and third decreases.