Open Rotor Variable Pitch Blade Retracting Edge Gap Sealing

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Solution Overview

Problem

Open rotor architectures face efficiency losses due to gaps between variable pitch blades and endwalls, causing airflow distortions and bypass, which reduce overall engine performance.

Innovation Solution

Incorporation of a retractable trailing edge member in the variable pitch blades and stator vanes that pivots between positions to block gaps with the endwall, using actuators or passive mechanisms like springs and counterweights to manage centrifugal forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If wide chord variable pitch blades are used with contoured inner diameter endwalls, then the gaps between the blade ID edge and end wall open up, but this causes airflow distortion and bypass that reduces engine efficiency

Engineering Contradiction:

Improvevariable pitch rangeVSAvoidairflow efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The trailing edge member is designed to move dynamically between retracted and extended positions based on blade pitch angle. During variable pitch operation, the member extends to seal gaps. At specific pitch angles, it retracts to allow blade rotation. This dynamic adjustment resolves the contradiction by providing gap sealing only when needed for efficiency while allowing full pitch range adaptability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The sealing function is localized to the trailing edge region where gaps form during pitch variation. The retractable trailing edge member provides targeted gap sealing at the critical interface between blade and end wall, while leaving other blade regions unchanged. This localized approach maintains airflow efficiency without compromising overall blade adaptability.

Inventive Principle:

Principle #3Local quality

2Loss of energy

If a retractable trailing edge member is added to seal gaps, then airflow efficiency improves, but device complexity increases

Engineering Contradiction:

Improveairflow efficiencyVSAvoidblade structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

A counterweight is attached to the trailing edge member to balance its weight and centrifugal forces during rotation. This passive counterbalancing mechanism allows the member to move freely between positions without requiring active actuators, significantly reducing system complexity while maintaining the gap sealing function.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The trailing edge member is designed to move automatically based on centrifugal forces and spring tension during blade rotation. The system uses the rotational motion itself to drive the sealing action, eliminating the need for external actuators or control systems. The spring provides the restoring force, and centrifugal force drives the extension, creating a self-actuating mechanism.

Inventive Principle:

Principle #25Self-service

3Power

If retractable trailing edge members are used to block gaps, then thrust performance improves, but the actuation mechanism adds weight

Engineering Contradiction:

Improvethrust performanceVSAvoidblade weight

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The counterweight serves dual purposes: it balances the trailing edge member during rotation (reducing bearing loads) and provides the driving force for gap sealing through centrifugal force. This eliminates the need for separate actuators, motors, or heavy spring mechanisms, minimizing added weight while maintaining thrust performance through effective gap sealing.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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

Minimizes airflow disruptions and maintains efficient airflow into the core inlet, enhancing overall engine efficiency and thrust performance across various pitch settings.

Implementation Method 1

The actuator may include a spring configured to overcome centrifugal loading of the retractable edge member to move the retractable edge member from the first position to the second position. The actuator may include a counterweight configured to overcome centrifugal loading of the retractable edge member to move the retractable edge member from the first position to the second position.

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS12352185B1Open rotor variable pitch blade with retracting inboard trailing edge

Publication Date: 2025.07.08 RTX CORP

AI summary

An apparatus comprises a variable pitch blade configured to connect with an endwall of an open rotor engine. The variable pitch blade defines a chamber therein on a bottom edge thereof. A retractable edge member pivotally connects within the chamber to move between a first position wherein at least a portion of the retractable edge member is located within the chamber and a second position wherein a portion of the retractable edge member extends downward from the bottom edge of the variable pitch blade to block a gap between the bottom edge of the variable pitch blade and the endwall.