Extended Nacelle Front Lip for Turbojet Engine Maintenance Access
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Solution Overview
Problem
The existing nacelle designs for aircraft turbojet engines face challenges in extending the front lip for aerodynamic benefits while maintaining mechanical rigidity and facilitating maintenance, as a single-piece front lip and outer envelope configuration complicates access and reduces rigidity.
Innovation Solution
The extended front lip is secured over the upstream partition wall with a downstream edge between the upstream and downstream partition walls, allowing access to the attachment flange while maintaining aerodynamic continuity, and features removable fastening means to dismountable panels for maintenance, reducing the need for access hatches and enhancing rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the front lip is lengthened for aerodynamic reasons to extend laminar airflow, then aerodynamic performance is improved, but mechanical rigidity deteriorates due to increased deformations under stress
Solution Approach 1:
The front lip is divided into multiple segments or sections that can be independently supported. Each segment is reinforced with internal stiffeners or ribs that provide local structural support, allowing the overall lip to be longer while maintaining rigidity through distributed reinforcement rather than a single continuous structure.
Solution Approach 2:
The front lip incorporates composite material construction with varying fiber orientations and material properties along its length. The root portion near the nacelle uses higher strength materials for rigidity, while the extended portions use optimized composite layups that maintain aerodynamic performance while reducing weight and improving resistance to deformation.
2Ease of manufacture
If the front lip and outer envelope are constituted by separate parts, then ease of manufacture and maintenance is improved, but device complexity increases
Solution Approach 1:
The front lip and outer envelope are merged into a single integrated structure formed as one piece during manufacturing. This eliminates the need for separate fastening systems, joints, and assembly steps, thereby reducing device complexity while maintaining ease of manufacture through streamlined production processes for monolithic structures.
3Strength
If access hatches are added to maintain a single-piece front lip and outer envelope configuration, then mechanical rigidity is maintained, but device complexity and mass increase
Solution Approach 1:
The fastening system is extracted and made removable, allowing the front lip and outer envelope to be separated for maintenance without requiring access hatches. This extraction of the permanent fastening system eliminates the need for hatch structures while maintaining the option for rigid assembly during operation, thereby reducing device complexity and mass.
4Strength
If heavy fastening systems are used to secure the front lip, then mechanical rigidity is improved, but device mass increases
Solution Approach 1:
The fastening system uses thin, flexible fastening elements such as clips, snap-fits, or bonded joints instead of heavy mechanical fasteners. These thin film-like fastening components provide sufficient holding strength while minimizing added mass, allowing the front lip to be securely attached without significant weight penalty.
Data Source
AI summary
A nacelle for an aircraft turbojet engine includes: a substantially cylindrical internal envelope, a substantially cylindrical external envelope, a downstream partition wall and an upstream partition wall secured to the cylindrical internal envelope and a front lip disposed forward of the upstream partition wall. The cylindrical internal envelope includes an upstream portion including an acoustic shroud connected, by an attachment flange, to a downstream portion including a fan casing. In particular, the front lip is extended and disposed over the upstream partition wall by presenting a downstream edge between the upstream and downstream partition walls in order to be secured to a homologous edge of the cylindrical external envelope so as to arrange a maintenance access to the attachment flange.