Cable-Pulley Thrust Reverser Flap Kinematics
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Solution Overview
Problem
Existing thrust reversers for aircraft engines with high bypass ratio turbojets face challenges due to the lack of sufficient space for connecting rods, leading to inadequate opening kinematics of flaps and increased pressure during transitional phases, causing aerodynamic and mechanical issues.
Innovation Solution
A thrust reverser design utilizing a cable-pulley system to drive the flaps, eliminating the need for connecting rods within the annular channel, ensuring controlled opening kinematics and maintaining a constant air section during thrust reversal, with features like a torsion spring and hooking mechanism for safety and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If connecting rods are used to pivot the flaps, then the flap opening kinematics can be controlled, but the rods cross the vein causing aerodynamic disturbances and acoustic performance degradation
Solution Approach 1:
The patent removes the connecting rods that crossed the vein and replaces them with a cable-pulley system. The cables are routed through guides and pulleys attached to the flap and cowl, eliminating the need for rods to traverse the annular channel, thus removing the source of aerodynamic disturbances while preserving flap control capability
Solution Approach 2:
The patent replaces the rigid mechanical connecting rod system with a flexible cable-pulley system. This substitution allows for smoother airflow through the vein while maintaining the mechanical advantage needed for controlled flap opening, addressing both aerodynamic and acoustic performance issues
2Ease of operation
If connecting rods are used to pivot the flaps, then the flap opening kinematics can be controlled, but the fixed articulation points reduce the surface area available for acoustic treatment
Solution Approach 1:
The patent eliminates the fixed articulation points created by connecting rods attached to the fairing. Instead, the cable-pulley system uses guides and pulleys that can be integrated into existing structures or positioned to minimize impact on acoustic treatment surface area, preserving more of the internal structure for acoustic purposes
3Strength
If connecting rods are used to pivot the flaps, then the mechanical connection between thrust reverser and internal structure is established, but mechanical problems occur due to the connection through the vein
Solution Approach 1:
The patent introduces cables as intermediaries to transmit the opening force from the sliding cowl to the flap. The cables pass through guides and pulleys that are attached to the cowl and flap respectively, avoiding direct mechanical connections through the vein. This intermediary system maintains mechanical stability while eliminating the reliability issues associated with rod connections through the high-velocity flow path
Solution Approach 2:
The patent uses flexible cables instead of rigid rods to connect the cowl and flap. The cables can accommodate the relative motion and deformation without creating rigid constraints that would lead to mechanical failures, thereby improving the reliability of the mechanical connection while maintaining structural integrity
4Speed
If the flap opens faster than the cowl retracts during transition phase, then the annular channel is partially obstructed, but this increases the pressure in the engine
Solution Approach 1:
The cable-pulley system provides a mechanical feedback mechanism that links the flap opening speed to the cowl retraction speed. As the cowl slides back, the cable gradually releases tension, controlling the flap opening rate to match the cowl movement. This feedback control prevents the flap from opening too quickly and obstructing the annular channel, thereby avoiding engine pressure increases during the transition phase
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 cable-pulley system provides reliable and efficient control over flap deployment, maintaining a constant air section and reducing pressure fluctuations, thus enhancing the thrust reverser's performance and structural integrity.
Implementation Method 1
a cable-pulley system for driving the flap
Implementation Method 2
with features like a torsion spring and hooking mechanism for safety and stability
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3A~3B
AI summary
Thrust reverser (10) for a jet engine nacelle (1) comprising means (13; 13'; 13'') for deflecting at least a part of the air flow (F) in the jet engine, and at least one cover (14) that is movable in translation with respect to an external fixed structure (11) of the reverser, the reverser having at least one rotationally articulated flap (15), said movable cover (14) being able to pass alternately from a closed position, in which it ensures the aerodynamic continuity of the nacelle (1) with the flap (15) and covers the deflecting means (13; 13'; 13''), the flap (15) being in a retracted position, to an open position, in which it opens a passage in the nacelle (1) and uncovers the deflecting means (13; 13'; 13''), the flap (15) shutting off a part of an annular duct (7) in the nacelle (1), characterized in that it comprises a cable-pulley system (20-25; 20'-25'; 20''-25'') for driving the flap (15).