Open Rotor Variable-Pitch Blade With Retractable Gap-Blocking Edge

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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 edge member in the variable pitch blades and stator vanes that moves 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 variable pitch blades with wide chord are used, then thrust levels and power settings can be varied, but gaps open between the inner diameter edge of the blade and the end wall causing airflow distortion and bypass

Engineering Contradiction:

Improvepower settings rangeVSAvoidairflow bypass

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The trailing edge of the blade is made dynamically adjustable through a retractable mechanism that can extend or retract based on the pitch angle. This dynamic adjustment allows the blade to maintain optimal positioning relative to the end wall across different power settings, preventing airflow bypass while enabling full range of pitch variation from reverse thrust to maximum power.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The blade trailing edge is segmented into a fixed portion and a retractable portion that can move independently. This segmentation allows the retractable section to adjust its position to close gaps with the end wall at different pitch angles, while the fixed portion maintains the overall blade structure and aerodynamic profile.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If variable pitch blades are used, then reverse thrust can be achieved, but significant gaps open between the blade and end wall impacting engine performance

Engineering Contradiction:

Improvethrust levels rangeVSAvoidgap control

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The retractable trailing edge mechanism provides dynamic adjustment capability that adapts to different pitch angles in real-time. This dynamic system maintains precise gap control throughout the full range of motion, from reverse thrust positions where maximum gap closure is needed to forward thrust positions where the gap naturally minimizes.

Inventive Principle:

Principle #15Dynamics

3Loss of energy

If retractable edge members are added to close 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 mechanism is employed to balance the retractable trailing edge, using centrifugal force generated during rotation to automatically drive the trailing edge toward the end wall. This passive counterbalancing system reduces the complexity of active control mechanisms while maintaining effective gap closure throughout the operating range.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The retractable trailing edge mechanism is designed to utilize the rotational motion and centrifugal forces already present in the operating environment to drive its own adjustment. The system self-regulates its position based on rotational speed and pitch angle, eliminating the need for complex external actuation systems.

Inventive Principle:

Principle #25Self-service

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 propulsor efficiency and reducing performance losses across various pitch angles.

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

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

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

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 3

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

PatentEP4682050A1Open rotor variable pitch blade with retracting inboard trailing edge

Publication Date: 2026.01.21 RTX CORP

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Figure 4A~4C

AI summary

An apparatus comprises a variable pitch blade (204) configured to connect with an endwall (206) of an open rotor engine (20). The variable pitch blade (204) defines a chamber (506) therein on a bottom edge (202) thereof. A retractable edge member (502) pivotally connects within the chamber (506) to move between a first position (510) wherein at least a portion of the retractable edge member (502) is located within the chamber (506) and a second position (512) wherein a portion of the retractable edge member (502) extends downward from the bottom edge (202) of the variable pitch blade (204) to block a gap between the bottom edge (202) of the variable pitch blade (204) and the endwall (206).