Static Back-Up Featherer for Contra-Rotating Propellers
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Solution Overview
Problem
Conventional power transfer methods for propeller blade pitch control mechanisms in contra-rotating engines, such as slip rings and rotating hydraulic couplings, face high maintenance burdens and reliability issues due to high operating speeds and complex fluid line configurations, making them unsuitable for efficient and reliable feathering in power failure scenarios.
Innovation Solution
A back-up featherer system with one or more static back-up hydraulic actuators and load application members that apply a load to the pitch change mechanism across a rotating interface, independent of the primary 'to coarse' fluid line, providing a redundant and physically separated feathering system with optional features like circumferentially spaced load application members and rotating bearings for reduced resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If slip rings are used for power transfer in contra-rotating propeller assemblies, then electrical power can be transferred to rotating components, but maintenance burden increases significantly and reliability decreases due to high operating speeds
Solution Approach 1:
The patent replaces the electrical slip ring system with a hydraulic power transfer system. Hydraulic fluid is used to transmit power from static to rotating components through a rotating hydraulic coupling, eliminating the mechanical contact and electrical arcing issues inherent in slip rings. This substitution significantly improves reliability in high-speed contra-rotating propeller applications.
Solution Approach 2:
The patent implements a hydraulic power transfer system where hydraulic fluid is pumped from a static source and transmitted through rotating hydraulic couplings to drive actuators on the rotating propeller assemblies. This hydraulic approach provides reliable power transfer without the maintenance issues of electrical slip rings, especially in the high-speed environment of contra-rotating props.
2Power
If rotating hydraulic couplings are used with large diameter interfaces, then sufficient hydraulic power can be transferred, but leakage increases and seal life decreases
Solution Approach 1:
The patent changes the operating parameters of the hydraulic system by using multiple smaller diameter rotating interfaces instead of one large interface. This distributes the hydraulic power transfer across multiple couplings, reducing the PV product at each interface and thereby minimizing leakage and extending seal life while maintaining sufficient total power transfer capability.
Solution Approach 2:
The patent divides the hydraulic power transfer function into multiple separate rotating hydraulic couplings distributed around the propeller assembly. Each coupling handles a portion of the total hydraulic power, allowing the use of smaller, more efficient interfaces with lower leakage rates compared to a single large coupling.
3Device complexity
If a single 'to coarse' fluid line is used for the pitch change mechanism, then system complexity is reduced, but common mode failures can occur preventing feathering during power failure
Solution Approach 1:
The patent segments the hydraulic power delivery system into multiple independent fluid lines and rotating hydraulic couplings. Each coupling and its associated fluid line operate independently, so a failure in one does not affect the others. This redundancy ensures that at least one path remains available for feathering operations during power failures, eliminating the single point of failure risk.
Solution Approach 2:
The patent creates local independence in the hydraulic system by distributing multiple fluid lines and couplings throughout the propeller assembly. Each local hydraulic circuit can function independently, providing localized backup capability that ensures feathering can be achieved even if one part of the system fails.
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 back-up featherer system ensures reliable and independent propeller blade feathering, reducing the risk of common mode failures and maintaining propeller control during engine failures, with low leakage and high integrity, even in complex engine configurations like contra-rotating propeller systems.
Implementation Method 1
one or more back-up hydraulic actuators located on a static structure of the engine arrangement
Implementation Method 2
A rotating hydraulic coupling can be provided at one end of the propeller shaft, with hydraulic supply lines running inside the shaft
Data Source
AI summary
A back-up featherer is provided for an engine arrangement having a main hydraulic actuator which operates a pitch change mechanism to angularly displace propellers of a propeller assembly of the engine arrangement, the pitch change mechanism and main hydraulic actuator rotating with the propeller assembly. The back-up featherer has one or more back-up hydraulic actuators located on a static structure of the engine arrangement. The back-up featherer further has one or more load application members which are located on the static structure of the engine arrangement and which are movable by the back-up hydraulic actuators. When moved by the back-up hydraulic actuators, the load application members bear against an engagement portion of the pitch change mechanism across a rotating interface formed therebetween to apply a load to the pitch change mechanism which results in angular displacement of the propellers.