Turbojet Intermediate Case Removable Panels with Retaining Elements
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Solution Overview
Problem
The existing bleed lines in turbojet intermediate cases are difficult to remove and reassemble due to maintenance constraints, which complicates access to components located between the core engine flow stream and the fan flow stream, potentially leading to damage from overpressurization and surging phenomena.
Innovation Solution
The intermediate turbojet case features a hub with removable panels and obliquely oriented bleed lines, where each bleed line has a downstream end fixed to a base plate that is preinstalled and secured to the panel using screws, allowing for easier assembly and disassembly by utilizing a retaining element that supports the base plate along the internal face of the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bleed lines are permanently fixed to panels, then structural reliability is improved, but ease of maintenance and access to components deteriorates
Solution Approach 1:
The intermediate case is divided into multiple removable panels that can be independently detached from the hub. Each panel can be removed to access components located between the core engine flow stream and the fan flow stream, while maintaining structural integrity when assembled. This segmentation allows maintenance personnel to access and repair components without removing the entire intermediate case.
Solution Approach 2:
The panels are designed with dynamic attachment mechanisms using retaining elements and screw connections that allow easy assembly and disassembly. The retaining elements provide temporary holding during assembly, while the screw connections enable secure attachment when needed, and quick release when maintenance is required. This dynamic design transforms the static structure into a maintainable system.
2Ease of repair
If bleed lines are easily removable, then ease of maintenance is improved, but assembly complexity increases
Solution Approach 1:
Retaining elements are pre-installed on the panels before the final screw attachment is made. These retaining elements hold the bleed lines in place during assembly operations, allowing technicians to position and secure components more easily. The preliminary installation of retaining elements simplifies the overall assembly process by providing intermediate holding points.
Solution Approach 2:
Retaining elements serve as intermediary components between the panels and bleed lines. These retaining elements facilitate the assembly process by providing temporary secure attachment, allowing the bleed lines to be positioned correctly before final screw fixation. The retaining elements act as mediators that simplify the connection process and reduce assembly complexity.
3Ease of repair
If panels are made removable, then ease of maintenance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The retaining elements are designed with specific local geometries that match corresponding features on the panels and hub. By optimizing the local attachment interfaces with precise but manageable dimensional tolerances, the design achieves easy maintenance while controlling manufacturing precision requirements to practical levels.
Data Source
AI summary
An intermediate turbojet case comprises a hub that supports removable panels and bleed lines, the hub comprising a flank provided with openings, each bleed line having an upstream end engaged in an opening in the flank and a downstream end terminated by a base plate through which it is fixed to an internal face of a removable panel by way of screws, each removable panel having a front edge at which it is fixed to an external lip of the hub by screws. At least one removable panel comprises a downstream edge supporting a retaining element close to the internal face to hold the base plate in contact with the internal face during a phase in which the removable panel is fixed to the hub by screwing, this phase preceding attachment of the base plate to the removable panel by screwing.