Thrust Reverser Movable Cowl and Cascade Configuration
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Solution Overview
Problem
Conventional aircraft bypass turbomachines face challenges in generating sufficient thrust during low-speed phases of flight, such as landing and taxiing, due to the limitations of thrust reversers, which can re-ingest gas streams and debris, leading to potential damage and inefficient braking.
Innovation Solution
A nacelle for an aircraft bypass turbomachine featuring a thrust reverser with an annular movable cowl and cascades that can switch between reverse thrust and partial or total thrust-cancelling modes, allowing the gas stream to be directed either upstream or downstream to manage thrust effectively across various flight phases without re-ingestion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the thrust reverser directs the gas stream upstream of the nacelle to create counter-thrust, then the braking effectiveness is improved, but the risk of re-ingesting the gas stream and debris increases, leading to potential damage to the turbomachine
Solution Approach 1:
The patent implements a movable cowl that can dynamically change its position between a closed configuration (during normal operation) and an open configuration (during thrust reversal). This dynamic adjustment allows the system to adapt to different operational phases, enabling effective counter-thrust generation while preventing re-ingestion of exhaust gases and debris by opening the cowl to direct the flow away from the intake.
Solution Approach 2:
The thrust reverser system is divided into distinct functional components: the movable cowl that controls flow direction, the cascades that redirect the gas stream, and the fixed annular envelope. This segmentation allows each component to perform its specific function independently, with the cowl managing the harmful flow direction issue while the cascades handle the thrust reversal function.
2Loss of time
If the thrust reverser is used at low speeds below the predefined limit, then the braking distance can be reduced, but the turbomachine may ingest debris thrown up by the gas stream, causing damage
Solution Approach 1:
The movable cowl provides dynamic control over the exhaust flow direction. During low-speed braking operations, the cowl is positioned in the open configuration to direct the gas stream away from the ground and intake area, preventing debris ingestion while still enabling effective thrust reversal to reduce braking distance.
Solution Approach 2:
The system changes the flow direction parameter by adjusting the cowl position. This parameter change allows the same thrust reverser mechanism to safely operate across different speed ranges, enabling low-speed braking without debris ingestion risks.
3Force
If the movable cowl and first cascade are moved together to the open position, then reverse thrust mode is achieved, but the device complexity increases due to the actuating mechanism required to coordinate their movement
Solution Approach 1:
The actuating mechanism merges the control of the movable cowl and the first cascade into a single coordinated system. By combining their actuation, the system reduces the number of independent control mechanisms needed, simplifying the overall device complexity while maintaining the ability to achieve effective reverse thrust through synchronized movement of both components.
4Power
If the secondary gas stream is bypassed through the thrust reverser, then the total thrust is increased during flight, but the ability to effectively brake during landing is reduced due to thrust reverser limitations
Solution Approach 1:
The thrust reverser system dynamically switches between two operational states: during normal flight, the movable cowl remains closed and the secondary gas stream contributes to forward thrust; during landing, the cowl opens to redirect the flow for effective braking. This dynamic adaptability resolves the contradiction between maximizing thrust during flight and enabling effective braking during landing.
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
Enables efficient thrust management during low-speed phases by allowing the thrust reverser to operate in partial or total thrust-cancelling modes below predefined speed limits, reducing braking distance and increasing turbomachine reliability, while preventing re-ingestion and debris-related damage.
Implementation Method 1
the movable cowl being able to slide relative to the annular envelope along the longitudinal axis
Implementation Method 2
the first cascade extends across the opening, such that at least a part of the secondary stream is capable of passing through the first cascade in the extended position in order to emerge outside the nacelle with a velocity that is oriented so as to generate a negative thrust
Implementation Method 3
the opening being occupied by at least one second thrust-reducing cascade of the thrust reverser, in said thrust-cancelling configuration, in such a way that the secondary stream passing through the opening emerges outside the nacelle with a velocity that is oriented so as to generate a substantially zero or positive thrust
Data Source
AI summary
A nacelle for an aircraft bypass turbomachine, including: an annular envelope extending about a longitudinal axis, a thrust reverser including: an annular movable cowl situated downstream of the annular envelope and able to slide with respect to the annular envelope along the longitudinal axis between a closed position and an open position in which the cowl and the nacelle casing define an opening between one another, at least one first thrust reverser cascade, an actuating mechanism designed to allow a partial or total thrust-cancelling configuration of the thrust reverser, in which configuration the movable cowl is moved into its open position while maintaining the or each first cascade in its retracted position, the opening being occupied by at least one second thrust-attenuating cascade of the thrust reverser, in such a way that the secondary flow passing through the opening exits to the outside of the nacelle with a speed oriented so as to generate a substantially zero or positive thrust along the longitudinal axis.