Back-up Featherer for Contra-Rotating Propellers
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Solution Overview
Problem
Conventional power transfer methods for propeller pitch change 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 routing, making them unsuitable for contra-rotating propeller assemblies.
Innovation Solution
A back-up featherer system with electro-mechanical brakes and input gears that operate independently of the primary hydraulic system, allowing for angular displacement of propellers without relying on the 'to coarse' primary line, providing a redundant and physically separate feathering mechanism.
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 the rotating field, but maintenance burden increases significantly and component life is reduced due to high operating speeds
Solution Approach 1:
The patent replaces the electrical slip ring system with a hydraulic power transfer system. Instead of using electrical contacts that wear at high speeds, the invention uses hydraulic fluid transmission through rotating couplings and flexible hoses, eliminating the mechanical electrical contact problem while maintaining power transfer capability to the rotating propeller assembly.
Solution Approach 2:
The patent introduces hydraulic fluid as an intermediary medium to transfer power from the static engine section to the rotating propeller assembly. The hydraulic fluid carries mechanical energy through flexible hoses and rotating couplings, avoiding direct mechanical electrical contacts and reducing wear at high operating speeds.
2Use of energy by moving object
If rotating hydraulic couplings are used for power transfer, then hydraulic power can be transmitted from static to rotating field, but the product PV of velocity and pressure must be kept within limits to maintain seal life
Solution Approach 1:
The patent divides the hydraulic power transfer system into multiple segments: static hydraulic pumps, flexible hoses, rotating couplings, and remote actuators. This segmentation allows each component to operate within acceptable PV limits, with the flexible hoses accommodating speed variations and the rotating couplings maintaining sealed connections while reducing overall system complexity.
Solution Approach 2:
The patent employs dynamic elements including flexible hoses and rotating couplings that can adapt to speed variations. The flexible hoses allow the system to accommodate changes in rotational speed without compromising seal integrity, while the rotating couplings maintain dynamic sealed connections that preserve hydraulic power transfer capability across varying operating conditions.
3Loss of substance
If a small diameter rotating interface is used in the hydraulic coupling, then leakage is reduced, but the complexity of routing hydraulic lines increases
Solution Approach 1:
The patent nests the hydraulic line routing within the engine architecture by utilizing existing hollow shafts and conduits. The hydraulic lines are routed through the hollow propeller shaft and engine mounting structures, eliminating the need for external routing and reducing overall system complexity while maintaining small diameter rotating interfaces that minimize leakage.
Solution Approach 2:
The patent makes existing structural elements multi-functional by using hollow shafts and engine conduits as both structural components and hydraulic line pathways. This universal approach eliminates dedicated hydraulic routing, reduces the number of separate components, and simplifies the overall system while maintaining effective hydraulic power transfer with minimal leakage.
4Device complexity
If the propeller shaft is used as a hollow conduit for hydraulic lines, then routing is simplified, but the PV value at the rotating interface increases
Solution Approach 1:
The patent extracts the hydraulic power transfer function from the propeller shaft by using separate hollow conduits and hoses that run parallel to or within the shaft structure. This separation allows the propeller shaft to operate at high speeds without transmitting hydraulic pressure, while the dedicated hydraulic conduits handle the PV product, reducing the rotating interface PV value.
Solution Approach 2:
The patent introduces intermediate hollow conduits and flexible hoses as mediators between the static hydraulic pump and the rotating actuator. These intermediate elements carry the hydraulic fluid through the engine structure, isolating the high-speed rotating propeller shaft from the hydraulic pressure transmission and reducing the PV product at the rotating interface while maintaining simplified routing.
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 propeller control and reduced risk of common mode failures, maintaining propeller efficiency and stability even in power failure scenarios, with low mass addition and no requirement for drive signals across static-rotating interfaces.
Implementation Method 1
A back-up featherer system with electro-mechanical brakes and input gears that operate independently of the primary hydraulic system
Implementation Method 2
one or more input gears rotatable about respective axes, which axes rotate with the propeller assembly, the input gears being operatively connected to the brakes such that, when the brakes are activated, the input gears rotate about their axes
Implementation Method 3
one or more load application members which rotate with the propeller assembly and which are operatively connected to the input gears such that, when the input gears rotate about their axes, the load application members bear against respective engagement portions of the pitch change mechanism to apply a load to the pitch change mechanism which results in angular displacement of the propellers
Data Source
AI summary
A back-up featherer is provided for an engine arrangement. The engine arrangement has 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 brakes located on a static structure of the engine arrangement. The back-up featherer further has one or more input gears rotatable about respective axes, which axes rotate with the propeller assembly. The input gears are operatively connected to the brakes such that, when the brakes are activated, the input gears rotate about their axes. The back-up featherer further has one or more load application members which rotate with the propeller assembly and which are operatively connected to the input gears such that, when the input gears rotate about their axes, the load application members bear against respective engagement portions of the pitch change mechanism. This applies a load to the pitch change mechanism which results in angular displacement of the propellers.