Counter-Rotating Propeller Pitch Limiting via Hydraulic Pressure Equalization
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Solution Overview
Problem
Existing aircraft turbine engine propeller pitch adjustment systems, particularly in counter-rotating propellers, face reliability issues and high maintenance costs due to mechanical safety devices that limit blade pitch angles, which can lead to involuntary adjustments and safety risks.
Innovation Solution
A propeller system with double-acting hydraulic actuators and hydraulic connection means that communicate both chambers of the actuator cavity when the pitch angle reaches a predetermined limit, preventing further displacement and reducing mechanical interactions, thereby enhancing reliability and reducing maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical safety devices are used to limit blade pitch angles, then blade pitch can be limited to prevent unsafe positions, but reliability decreases and maintenance costs increase
Solution Approach 1:
The patent replaces mechanical safety devices with a hydraulic limitation system. The hydraulic connection means use fluid pressure to limit piston stroke and blade pitch angle, eliminating the need for mechanical abutments and retractable stops. This substitution of hydraulic control for mechanical limitation resolves the contradiction by improving reliability while reducing device complexity.
Solution Approach 2:
The patent employs a hydraulic actuator with a piston divided into two chambers by a separator. Hydraulic connection means communicate these chambers to limit piston displacement and thereby limit blade pitch angle. This hydraulic approach replaces complex mechanical safety devices, improving reliability and reducing maintenance requirements.
2Reliability
If mechanical limitation devices are installed in counter-rotating propeller systems, then pitch angle safety is improved, but maintenance costs increase due to multiple devices
Solution Approach 1:
The patent merges the safety limitation function directly into the hydraulic actuator system itself. The hydraulic connection means are integrated with the actuator chambers and piston, combining the actuation and safety limitation functions into a single system. This eliminates the need for separate mechanical safety devices on each propeller, reducing maintenance costs while maintaining pitch angle safety.
Solution Approach 2:
The hydraulic limitation system is self-regulating through fluid pressure equality. When the piston reaches the position corresponding to the predetermined minimum pitch angle, the hydraulic connection automatically equalizes pressure between chambers, preventing further displacement. This self-limiting mechanism eliminates the need for external mechanical stops, reducing maintenance requirements.
3Adaptability or versatility
If hydraulic actuators allow full range of motion, then adaptability is improved, but safety risks increase due to involuntary adjustments
Solution Approach 1:
The hydraulic connection means provide continuous feedback on piston position through fluid pressure. As the piston approaches the position corresponding to the predetermined minimum pitch angle, the hydraulic system automatically equalizes chamber pressures, providing a natural stopping point. This feedback mechanism prevents involuntary adjustments beyond the safe pitch angle while maintaining adaptability within the safe range.
Solution Approach 2:
The hydraulic connection means are pre-configured to equalize chamber pressures at the position corresponding to the predetermined minimum pitch angle. This preliminary hydraulic arrangement prevents the piston from reaching positions that would cause unsafe pitch angles, proactively eliminating the risk before involuntary adjustments can occur.
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
The solution effectively prevents involuntary blade adjustments to unsafe pitch angles, improving reliability and reducing maintenance costs by ensuring fluid pressure equality across the actuator chambers, thus maintaining safe blade positions and reducing operational risks.
Implementation Method 1
hydraulic connection means allowing both chambers of each cavity of each aforementioned actuator to be put into fluidic communication with each other as soon as the pitch angle of said blades becomes equal to said predetermined limiting pitch angle
Data Source
AI summary
A propeller for an aircraft turbine engine, comprising means for adjusting the pitch of the blades comprising a hydraulic actuator borne by the rotor and including a cavity and a piston displaceable in said cavity and dividing said cavity into two chambers, as well as means for limiting the stroke of the piston in order to prevent displacement of said blades in a predetermined direction beyond a predetermined limiting pitch angle, and comprising hydraulic connection means with which both chambers may be put into communication with each other as soon as the pitch angle of the blades becomes equal to said predetermined limiting pitch angle during the displacement of said blades in said predetermined direction, these hydraulic connection means being borne by said rotor of the propeller.