Turbojet Nacelle Centering Device for Flush Panel Alignment
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Solution Overview
Problem
Manufacturing and assembling tolerances in aeronautical nacelles can lead to radial recesses between the cowl of the fan casing and the panels of the thrust reversers, causing aerodynamic performance losses, erosion, and delamination, while also affecting the appearance of the nacelle.
Innovation Solution
A centering device with a sub plate, a first positioning arm for guiding the cowl, and a second positioning arm for guiding the outer downstream panel, allowing for precise alignment and flush positioning of the panels, reducing the radial distance between them and eliminating the need for strict manufacturing or assembling tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional manufacturing and assembling methods are used, then the assembly process is simple, but radial recesses appear between the cowl and thrust reverser panels causing aerodynamic performance losses
Solution Approach 1:
A centering device is introduced as an intermediary tool during assembly. This device includes positioning arms that extend from the cowl to the thrust reverser panel, providing a mechanical reference that ensures precise radial alignment. The centering device acts as a mediator between the cowl and panel components, eliminating the need for extremely tight manufacturing tolerances while preventing the formation of radial recesses that would compromise aerodynamic performance.
Solution Approach 2:
The centering device is positioned and secured to the cowl before the thrust reverser panel is installed. This preliminary positioning action establishes a precise reference framework in advance, allowing the panel to be aligned correctly relative to the cowl. By performing this centering and positioning operation before final assembly, the system ensures that radial alignment precision is achieved without requiring complex manufacturing processes.
2Manufacturing precision
If strict manufacturing tolerances are enforced, then radial recesses are eliminated, but manufacturing cost and complexity increase
Solution Approach 1:
The centering device serves as a mechanical intermediary that translates loose manufacturing tolerances into precise final positioning. Instead of requiring each component to be manufactured within tight tolerances, the centering device provides a reference surface that ensures accurate alignment during assembly. This approach maintains radial alignment precision while significantly easing the manufacturing process and reducing overall complexity.
Solution Approach 2:
The positioning function is segmented into separate components: the centering device with its positioning arms, the cowl mounting structure, and the thrust reverser panel. This segmentation allows each component to be manufactured with standard tolerances while the centering device assembles them into the precise radial alignment required to prevent recesses. The segmentation of the positioning function reduces the stringency requirements for individual component manufacturing.
3Manufacturing precision
If multiple separate positioning components are used, then alignment precision can be achieved, but the dimension chain and assembly complexity increase
Solution Approach 1:
Multiple positioning functions are merged into a single integrated centering device. The device combines the cowl mounting function, the positioning arm extensions, and the reference surface provision into one unified component structure. This merging reduces the number of separate parts and connections required, thereby shortening the dimension chain while maintaining radial alignment precision through the integrated design of the positioning arms and reference surfaces.
Data Source
AI summary
The present disclosure relates to a centering device for a nacelle of a turbojet engine providing the flush centering of an outer downstream panel of a thrust reverser with respect to a cowl of a fan casing. The centering device includes, in one single piece: a sub plate allowing the fixing of the centering device to the fan casing; a first positioning arm integrally formed with the sub plate, protruding upstream, in such a manner as to form, with respect to a directing axis (A) of the nacelle; a first radial abutment designed for guiding the cowl of the fan casing; and a second positioning arm, integrally formed with the sub plate, protruding downstream, in such a manner as to form, with respect to the directing axis (A) of the nacelle, a second radial abutment designed for guiding the outer downstream panel.