Turbojet Rear Nacelle Cradle for Thrust Reverser Kinematic Alignment
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Solution Overview
Problem
Modern turbojet engine nacelles with thrust reverser devices face issues due to deformation forces on mobile grids and relative displacement of rails, leading to structural stresses and compromised kinematics, particularly in large and flexible propulsion units, which complicates maintenance and operation.
Innovation Solution
A rear nacelle assembly with a cradle that includes longitudinal spars and connecting means to guide the thrust reverser device, allowing it to follow the turbojet engine's movements, reducing stress and facilitating installation and removal, while interconnected crosspieces enhance mechanical strength and guide rail alignment ensures smooth sliding operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the mobile grids are fixed to the mast in a rigid configuration, then the thrust reverser structure is simple, but the grids are subjected to deformation forces and significant stresses when the turbojet engine moves relative to the mast
Solution Approach 1:
The patent applies the dynamics principle by making the cradle movable rather than fixed. The cradle can move with the turbojet engine relative to the mast, allowing the mobile grids to follow the engine's motion dynamically. This eliminates the rigid connection that causes deformation forces, while maintaining operational simplicity through the guided movement mechanism.
2Volume of moving object
If the mobile grids are made with reduced section to limit bulk, then the inertia and mechanical resistance are reduced, but the grids become more vulnerable to deformation forces and kinematic errors
Solution Approach 1:
The patent applies the intermediary principle by introducing the cradle as a mediator between the mast and the mobile grids. The cradle provides a flexible yet guided connection that allows the grids to move with the engine while maintaining structural support. This intermediary structure protects the lightweight grids from direct deformation forces without requiring the grids themselves to be bulky.
3Manufacturing precision
If the rails are rigidly fixed to ensure geometric stability, then the kinematics are precise, but the assembly becomes complex and difficult to maintain
Solution Approach 1:
The patent applies the segmentation principle by dividing the rail system into modular sections that can be independently assembled and maintained. The rails are configured as separate components within the cradle structure, allowing for easier inspection, replacement, and adjustment without affecting the entire thrust reverser assembly. This maintains geometric precision while improving maintainability.
4Ease of manufacture
If the thrust reverser is designed as a fixed assembly, then the installation is simple, but the relative movement of the turbojet engine causes deformation forces and compromised operation
Solution Approach 1:
The patent applies the dynamics principle by transitioning from a fixed assembly to a movable cradle that follows the engine's motion. The cradle is designed to move with the turbojet engine relative to the mast, allowing the thrust reverser to maintain proper kinematic alignment during engine movement. This dynamic design ensures reliable operation while remaining relatively simple to install as a complete assembly.
Data Source
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AI summary
The present disclosure provides a rear nacelle assembly for a turbojet having at least one thrust reversal device to redirect air circulating from upstream to downstream in a flow path of a turbojet and a mast that connects the nacelle to a structure of an aircraft. In one form, the thrust reverser device includes a cradle having a first longeron and a second longeron extending longitudinally opposite sides of the mast. The first and second longeron each include a device for slideably guiding the cowl and the cascade. In another form, a rear portion and a front portion of the cradle connects to the mast by a rear connecting device and front connecting device, respectively, such that the cradle is adapted to follow the movements of the turbojet.