Contra-Rotating Fan Locking and Pitch Control
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Solution Overview
Problem
Existing aircraft propulsion systems with contra-rotating fans face challenges in safely managing a malfunctioning fan, requiring a method to efficiently shut down the affected rotor while maintaining optimal operating conditions for landing.
Innovation Solution
The integration of a device that locks the rotation of the fan, modifies the pitch of the blades to operate as a guide vane assembly, and employs braking means to rigidly connect the power turbine rotor to an immovable casing, along with accelerometer-based imbalance detection for informed decision-making.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan is shut down by stopping the rotor, then the malfunctioning fan is isolated, but the aircraft loses propulsion capability and cannot return to airport safely
Solution Approach 1:
The patent converts the harmful effect of a malfunctioning fan into a beneficial configuration by repositioning its blades to act as guide vanes. This allows the disabled fan to contribute positively to thrust generation and flow management, transforming a safety hazard into a functional component that aids aircraft return-to-base capability
Solution Approach 2:
The patent introduces dynamic adaptability by making the fan blade pitch adjustable between two states: operational mode for normal flight and guide vane mode for malfunction scenarios. This dynamic reconfiguration allows the system to optimize performance based on operational status, maintaining propulsion capability during abnormal conditions
2Productivity
If the fan continues to operate with imbalance or blade loss, then propulsion is maintained, but the aircraft safety is compromised
Solution Approach 1:
The patent implements preliminary action by providing advance detection means (accelerometers and other sensors) that identify fan imbalance or blade loss conditions before they become critical safety hazards. This early detection triggers preventive reconfiguration, allowing the system to transition to guide vane mode before catastrophic failure occurs, thus maintaining safety while preserving propulsion
3Reliability
If the rotor is locked rigidly to the casing, then the fan is securely shut down, but the ability to resume operation is lost
Solution Approach 1:
The patent employs dynamic braking means that can be activated selectively rather than permanently engaged. The braking system allows the rotor to be locked when needed for secure shutdown, but can be released to restore operational capability. This dynamic control mechanism provides both secure shutdown when required and operational flexibility when conditions permit
Solution Approach 2:
The patent implements feedback control through detection means that monitor fan condition and trigger appropriate responses. When imbalance or malfunction is detected, the system activates braking and repositions blades to guide vane configuration. Once the situation is resolved or stabilized, the system can reverse the braking action and restore normal operation, creating a closed-loop control system that adapts to changing conditions
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
This solution enables efficient and controlled shutdown of a malfunctioning fan, optimizing thrust and ensuring safe landing conditions by converting the shut-down rotor into a stator-like role, while maintaining propulsion through the other fan.
Implementation Method 1
a locking device (27) having braking means which make it possible to rigidly connect the rotor of the power turbine driving the corresponding fan to an immovable casing of the turbine engine
Data Source
AI summary
An aircraft comprising a fuselage and propelled by a turbine engine having two coaxial and contrarotating fans, the turbine engine comprising a power turbine having two contrarotating rotors, one of which drives a fan upstream from the turbine, the other a fan downstream from the turbine, each fan comprising a ring of blades, and the assembly of the fans and the power turbine being incorporated at the rear of the fuselage, in the extension of same. The aircraft comprises, for at least one of the fans, a device for blocking the rotation of the fan and a device configured to modify the pitch of the blades of the fan in such a way as to make it operate as a flow straightener with respect to the other fan.