Mobile-Cowl Thrust Reverser with Independent Flap Actuation
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Solution Overview
Problem
Conventional thrust reversers for aircraft propulsion assemblies face challenges in safely modulating thrust during descent phases, leading to undesirable counterthrust, aerodynamic disturbances, and safety hazards, especially when partially deployed in high-bypass ratio engines.
Innovation Solution
A thrust reverser with a fixed internal structure, a mobile external structure, and independent actuation mechanisms for blocking flaps, allowing for a reduced thrust configuration without unlocking the mobile external structure, thereby maintaining aerodynamic stability and preventing counterthrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional thrust reverser is placed in an intermediate configuration to reduce thrust, then thrust modulation is achieved, but undesirable counterthrust is generated and aerodynamic disturbances occur
Solution Approach 1:
The thrust reverser system is segmented into independent functional components: the mobile cowl that maintains aerodynamic sealing, and the blocking flaps that independently control thrust reduction. This segmentation allows the flaps to modulate thrust without requiring the cowl to move, thereby avoiding aerodynamic disturbances and counterthrust generation while maintaining full thrust capability when needed.
Solution Approach 2:
The blocking flaps are designed with dynamic positioning capability, allowing them to be partially deployed to reduce thrust by blocking a portion of the gas flow. This dynamic adjustment of flap position enables continuous thrust modulation from full thrust to reduced thrust levels without transitioning to reverse jet configuration, preventing undesirable counterthrust.
2Productivity
If the mobile cowl position is modified to reduce thrust, then thrust modulation is achieved, but external aerodynamics are disturbed and lift is lost
Solution Approach 1:
The system separates the aerodynamic sealing function (performed by the stationary mobile cowl in its closed position) from the thrust modulation function (performed by the independently actuated blocking flaps). This allows thrust reduction without moving the cowl, maintaining aerodynamic stability and preventing lift loss.
Solution Approach 2:
The blocking flaps act as an intermediary mechanism between the gas flow and the mobile cowl. They modulate thrust by blocking portions of the flow internally, eliminating the need to move the cowl and thus preserving the external aerodynamic profile and lift characteristics.
3Productivity
If thrust is reduced by reducing gas flow and engine speed, then thrust modulation is achieved, but engine operability constraints are violated
Solution Approach 1:
The thrust modulation function is extracted from the engine control system and transferred to the blocking flaps. This allows the engine to maintain its normal operating regime (fuel flow rate and speed) while the flaps independently control the effective thrust output, ensuring engine operability constraints are not violated.
Solution Approach 2:
The blocking flaps provide multi-functionality: they can be fully retracted to allow full thrust, partially deployed to reduce thrust during descent, or fully deployed to enable reverse jet configuration. This single component handles multiple thrust control scenarios without requiring engine speed or fuel flow adjustments.
Data Source
AI summary
In a thrust reverser for an aircraft propulsion unit, the thrust reverser includes an internal fixed structure, a mobile cowl and blocking flaps. The thrust reverser also includes a first actuation mechanism that is configured to move the mobile cowl between a closing position and an opening position so as to cause the blocking flaps to move respectively between a retracted position and a deployed position, thus causing the thrust reverser to pass respectively between a full-thrust configuration and a thrust-reversal configuration. The thrust reverser also includes a second actuation mechanism that is configured to move the blocking flaps between the retracted position and a partially deployed position when the mobile cowl is in the closing position, so as to cause the thrust reverser to pass respectively between the full-thrust configuration and a reduced-thrust configuration.