Counterweighted Pawl Ratchet for Reverse Windmilling Control

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Solution Overview

Problem

Turbine engines often windmill in reverse due to reverse wind, which is undesirable as it increases wear and prevents proper lubrication of rotating components, and existing solutions are either complex or non-existent, limiting the ability to control windmilling direction effectively.

Innovation Solution

An anti-rotational system featuring a pawl carrier with radially positioned counterweights and ratchet teeth, where the pawl carrier is mounted coaxially with a ratchet, and a torsion spring exerts a radial force to prevent rotation in the undesired direction by adjusting contact with the ratchet teeth based on angular velocity, utilizing materials like stainless steel and chromium-nickel-tungsten martensitic alloy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a complex anti-rotational system is implemented, then reverse windmilling is prevented, but device complexity increases

Engineering Contradiction:

Improveprevention of reverse windmillingVSAvoidcomplexity of anti-rotational system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pawl is designed with dynamic characteristics where its contact with the ratchet tooth changes based on rotational speed. At low speeds, the pawl engages the ratchet to prevent reverse rotation. At high speeds, centrifugal force causes the pawl to lift off the ratchet tooth, allowing free rotation. This speed-dependent engagement resolves the contradiction by providing protection only when necessary.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The counterweight portion of the pawl creates centrifugal force during rotation that opposes the pawl's engagement with the ratchet tooth. This centrifugal effect naturally disengages the pawl at high rotational speeds without requiring additional control mechanisms, simplifying the overall system while maintaining reliability.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Reliability

If reverse windmilling is prevented, then wear on engine components is reduced, but forward windmilling capability is restricted

Engineering Contradiction:

Improvereduction of component wearVSAvoidwindmilling capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system dynamically adapts its behavior based on rotational speed. The pawl engages to prevent reverse rotation at low speeds where wear is a concern, but disengages at high speeds to allow forward windmilling for engine restart. This resolves the contradiction by providing direction-selective protection rather than complete rotation restriction.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The pawl's engagement and disengagement occurs periodically based on rotational speed thresholds. During normal operation at low speeds, the pawl engages to prevent reverse motion. During restart scenarios at high speeds, the pawl disengages to permit forward rotation, creating a periodic on/off protection pattern that satisfies both wear reduction and windmilling needs.

Inventive Principle:

Principle #19Periodic action

3Reliability

If lubrication system operates during forward windmilling, then rotating components are lubricated, but reverse windmilling causes unlubricated rotation and wear

Engineering Contradiction:

Improvelubrication of rotating componentsVSAvoidwear from reverse windmilling

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The system converts the harmful effect of reverse windmilling into a useful indicator. By allowing reverse rotation to occur naturally and detecting it through the pawl-ratchet interaction, the system triggers the lubrication system to activate, ensuring components are lubricated regardless of rotation direction. This resolves the contradiction by using the harmful reverse motion as a signal to provide protective lubrication.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

Effectively prevents reverse windmilling by limiting rotation in the counter-clockwise direction at higher angular velocities, reducing mechanical contact and wear, while allowing forward windmilling to facilitate engine restart and proper lubrication of components.

Implementation Method 1

the counterweight portion is configured to be radially outward of the contact portion in response to rotation of the pawl carrier at an angular velocity greater than a predetermined angular velocity

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

a torsion spring is disposed proximate the pivot joint and configured to exert an outward radial force on the contact portion of the pawl

Methodology Applied

Scientific EffectElastic force: Spring

Data Source

PatentEP2930333B1Anti-rotational systems and methods

Publication Date: 2021.06.02 UNITED TECH CORP

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AI summary

An anti-rotational system (200) is provided comprising a pawl carrier (212) mounted for rotation within a ratchet (202), the pawl carrier (212) having an axis of rotation, a pawl (206,208,210) pivotably mounted to the pawl carrier (212) on a pivot joint (302), the pawl (206,208,210) having a contact portion (314) and a counterweight portion (304), wherein the pivot joint (302) is between the contact portion (314) and the counterweight portion (304), wherein the counterweight portion (304) is configured to be radially inward of the contact portion (314) in response to rotation of the pawl carrier (212) in a first rotational direction at an angular velocity less than a predetermined angular velocity.