Thrust Reverser Cascade Nacelle Radial Thickness Reduction
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Solution Overview
Problem
Modern airplane nacelles aim to reduce aerodynamic losses by minimizing the radial thickness of the rear support frame of thrust reverser cascades, as traditional designs require radial bulk due to actuating cylinders passing through the rear frame.
Innovation Solution
A cascade thrust reverser design where the cylinders are mounted on a stationary portion of the nacelle and their downstream ends are attached to an inner diaphragm, eliminating the need for the cylinders to pass through the rear support frame, thus reducing the frame's thickness and allowing for a more compact structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If cylinders are fastened on the stationary part of the nacelle and attached to the moving cowl, then the thrust reversal function is achieved, but the radial thickness of the rear frame increases due to traditional mounting methods
Solution Approach 1:
The invention changes the mounting dimension of the cylinders from radial mounting (passing through the rear frame) to axial mounting (on the upstream edge of the diaphragm). This dimensional change allows the cylinders to be positioned without increasing the radial thickness of the rear frame, while still achieving the required thrust reversal function through the same actuating mechanism.
Solution Approach 2:
The invention uses an annular diaphragm as a copying element that transfers the actuating force from the cylinders to the moving cowl. The diaphragm acts as an intermediary structure that replicates the force transmission function while enabling a different spatial arrangement that reduces radial thickness.
2Loss of energy
If the rear frame is made thinner to reduce aerodynamic losses, then aerodynamic efficiency improves, but the structural support for actuating mechanisms becomes insufficient
Solution Approach 1:
By relocating the cylinder mounting from the radial direction (through the rear frame) to the axial direction (on the upstream edge of the diaphragm), the invention removes the structural load requirements from the rear frame in the radial direction. This allows the rear frame to be made thinner for aerodynamic efficiency while the diaphragm structure handles the actuating forces in the axial direction.
3Device complexity
If cylinders pass through the rear support frame to actuate the moving cowl, then the actuating mechanism is simplified, but the radial bulk of the rear frame increases
Solution Approach 1:
The invention extracts the cylinder mounting function from the rear frame structure and relocates it to the upstream edge of the diaphragm. This separation allows the rear frame to be optimized for aerodynamic efficiency (thinner radial thickness) while the diaphragm structure assumes the actuating mechanism support function.
Solution Approach 2:
The annular diaphragm serves as an intermediary structure between the cylinders and the moving cowl. It provides a mounting surface for the cylinders on its upstream edge and transfers their actuating force to the moving cowl, enabling the cylinders to function without passing through the rear frame.
Data Source
AI summary
A cascade thrust reverser for an airplane dual flow jet engine nacelle is provided that includes a front frame holding a plurality of cascades, a cowling slidably mounted between a direct jet position and a reverse jet position. The cowl includes a substantially annular diaphragm that is placed edge-to-edge with the front frame and radially inside said cascades when said cowl is located in the direct jet position. Thrust reversal flaps are pivotably mounted onto the diaphragm, and cylinders for actuating the cowl are also provided. Upstream ends of the cylinders are mounted on a stationary portion of the nacelle, and the downstream ends of the cylinders are mounted on an upstream edge of the diaphragm.