Turbojet Nacelle Linkage Relocation for Thrust Reverser
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Solution Overview
Problem
Conventional cascade thrust reversers for turbojet engines occupy significant volume, compromising the aerodynamic shape and soundproofing of the nacelle's annular flow path due to the placement of tie-rods below the cascades, which limits the optimization of airflow and soundproofing.
Innovation Solution
The nacelle design features thrust reverser cascades with movable cowls and linkage systems in a tangential plane, allowing for a larger stroke of the cowls compared to the cascades, and tilting flaps controlled by a single actuating system, which clears space below the cascades for improved aerodynamics and soundproofing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If tie-rods are disposed below the cascades to control the thrust reverser mechanism, then the cascades can be actuated to redirect airflow, but the volume below the cascades is occupied which compromises the aerodynamic shape and soundproofing of the annular flow path
Solution Approach 1:
The patent relocates the linkage system from a vertical arrangement (below the cascades) to a horizontal/tangential arrangement (above the cascades in a tangential plane). This dimensional change moves the mechanism out of the problematic vertical space, clearing the area below cascades for aerodynamic optimization and soundproofing while maintaining the actuation function through the lever and connecting rod mechanism disposed radially outside the cascades
2Ease of operation
If tie-rods are disposed below the cascades to control the thrust reverser mechanism, then the cascades can be actuated, but the space below the cascades is occupied which limits the lining with soundproofing panels
Solution Approach 1:
The patent extracts the linkage mechanism (levers, connecting rods, articulations) from the space below the cascades and relocates it to the tangential plane above the cascades. This extraction clears the previously occupied volume, enabling uninterrupted installation of soundproofing panels on the annular flow path surfaces while preserving the thrust reverser actuation capability through the relocated mechanism
3Shape
If the linkage system is disposed radially outside the cascades in a tangential plane, then the space below the cascades is cleared for aerodynamic optimization, but the mechanism complexity increases with levers and articulations
Solution Approach 1:
The patent resolves the complexity issue by organizing the linkage components (levers, connecting rods, articulations) in a two-dimensional tangential plane rather than distributing them in three-dimensional space below the cascades. This planar arrangement simplifies the overall system architecture, enables modular assembly, and maintains actuation efficiency while clearing the vertical space for aerodynamic optimization
4Volume of moving object
If the connecting system imparts a larger stroke to the movable cowl than to the cascades, then the air passage is largely cleared, but the differential movement mechanism requires additional linkage components
Solution Approach 1:
The patent employs curved or articulated linkage paths through the lever and connecting rod arrangement with multiple articulations. This allows the movable cowl to traverse a larger arc or path length compared to the linear displacement of the cascades, achieving differential stroke without requiring complex variable-ratio mechanisms. The curved motion path naturally produces the desired differential movement
Data Source
AI summary
A nacelle for a turbojet includes a thrust reverser having cascades, movable cowls adjacent to the cascades in a closed position, linkage systems for connecting the cowls and the cascades, and tilting closure flaps. Each linkage system is arranged radially outside the cascades, and includes, in a tangential plane, a lever, connecting rods, and pivots allowing a movement substantially in this plane. The pivots include a fixed pivot connected to a fixed element of the nacelle, a pivot connected to the cascades and a pivot connected to the cowls. The lever, termed first lever, includes two arms forming a “V,” and two connecting rods are fixed to the end of an arm by a pivot.