CROR Pitch Control via Mechanical Linkage

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Solution Overview

Problem

Counter-Rotating Open-Rotor (CROR) gas turbine engines face challenges in aerodynamics, aeroacoustics, and structural dynamics due to rotor/rotor interactions, particularly in controlling the pitch of forward and aft rotors positioned close together outside the nacelle structure.

Innovation Solution

Mechanical linkage of pitch change systems between the forward and aft rotors, with a linear relationship between the commanded and actual blade angles of the forward rotor, and a non-linear relationship between the aft rotor's blade angles, allowing for effective control and reduced complexity in feedback signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If independent pitch change systems are used for forward and aft rotors, then each rotor can be controlled independently for optimal performance, but the control system complexity and feedback requirements increase significantly

Engineering Contradiction:

ImproveIndependent rotor control capabilityVSAvoidPitch change control system complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent combines the pitch change control of forward and aft rotors through a mechanical linkage system. The aft rotor pitch change system is mechanically coupled to the forward rotor pitch change system, allowing synchronized control while reducing the need for independent feedback signals for the aft rotor. This merging approach maintains adaptability while significantly reducing control system complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The mechanical linkage system serves multiple functions: it transmits pitch change commands from the forward rotor to the aft rotor, provides structural support, and eliminates the need for separate feedback mechanisms for the aft rotor. This multi-functionality reduces overall system complexity while maintaining independent control capability when needed.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Volume of moving object

If the aft rotor is positioned close to the forward rotor outside the nacelle, then the CROR achieves compact design and high bypass ratio, but rotor/rotor interactions increase causing aerodynamic and aeroacoustic challenges

Engineering Contradiction:

ImproveEngine compactnessVSAvoidRotor/rotor interactions

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent employs dynamic blade pitch control where the blade pitch angles of both rotors are continuously adjusted based on operational conditions. This dynamic control allows optimization of rotor/rotor interactions in real-time, reducing aerodynamic interference and aeroacoustic noise while maintaining the compact close-spaced configuration.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes operational parameters including blade pitch angle, rotational speed, and phase relationship between the two rotors to minimize harmful interactions. By adjusting these parameters, the system optimizes performance while reducing aerodynamic interference and noise generation in the compact CROR configuration.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If mechanical linkage is used between pitch change systems, then control precision and stability are enhanced while reducing feedback complexity, but the mechanical system complexity increases

Engineering Contradiction:

ImproveBlade angle control precisionVSAvoidMechanical linkage system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The mechanical linkage acts as an intermediary between the forward rotor pitch change system and the aft rotor pitch change system. It transmits control commands mechanically, ensuring synchronized and precise blade angle control without requiring complex electronic feedback systems for the aft rotor. This intermediary mechanism enhances control precision while managing system complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Speed

If linear relationship is maintained between commanded and actual blade angles of forward rotor, then control responsiveness is improved, but the non-linear relationship required for aft rotor control becomes more complex

Engineering Contradiction:

ImproveControl responsivenessVSAvoidNon-linear control relationship complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent segments the control relationships by applying different control strategies to each rotor. The forward rotor maintains a linear relationship between commanded and actual blade angles for responsive control, while the aft rotor uses a non-linear relationship optimized for its specific aerodynamic requirements. This segmentation allows each rotor to operate optimally with appropriate control characteristics.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9718536B2Counter-rotating open-rotor (CROR)

Publication Date: 2017.08.01 HAMILTON SUNDSTRAND CORP

AI summary

A method of controlling a Counter-Rotating Open-Rotor (CROR) includes mechanically linking a pitch change system of a first rotor with a pitch change system of a second rotor and commanding a Blade Angle (Beta1 commanded) of the first rotor such that a Blade Angle (Beta2 Actual) of the second rotor is a function of the commanded Blade Angle (Beta1 commanded) to provide a linear relationship between an actual Blade angle (Beta1 Actual) and Beta1 commanded of the first rotor and a non-linear relationship between Beta2 Actual and Beta1 commanded.