Turbojet Nacelle Rear Assembly With Cellular Wall Cooling
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Solution Overview
Problem
Existing cooling systems for turbofan nacelle components, such as damping and stopping devices, require additional manufacturing steps and reduce the acoustic insulation due to through-holes and fixing elements, leading to potential damage from excessive temperatures.
Innovation Solution
A composite wall design with first and second skins separated by a median assembly of cells, featuring through-holes only in the second skin to direct airflow for cooling, eliminating the need for through-drilling and enhancing acoustic insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If through-holes are made in the composite wall for cooling orifices and fixing elements, then cooling function is improved, but acoustic insulation is reduced and manufacturing complexity increases
Solution Approach 1:
The composite wall is segmented into three distinct parts: first skin, median assembly with cells, and second skin. The cooling function is achieved through segmented pathways - cold air enters through the first skin, flows through the cell structures in the median assembly, and exits through the second skin. This segmentation allows cooling without requiring direct through-holes penetrating the entire composite wall structure, thereby preserving acoustic insulation.
Solution Approach 2:
The median assembly with its cell structures acts as an intermediary between the first and second skins. Instead of creating direct through-holes from first to second skin, the cold air flow is directed through this intermediate cellular structure. The fixing elements are also positioned within this intermediary zone, allowing them to be cooled without penetrating the first skin. This intermediary structure enables the cooling function while maintaining the integrity and acoustic insulation properties of the composite wall.
2Ease of operation
If through-holes and fixing elements are added to the composite wall, then cooling and assembly functions are improved, but manufacturing steps increase
Solution Approach 1:
The median assembly with cell structures is pre-configured with internal pathways and features that facilitate the positioning of fixing elements and cold air flow. The fixing elements are designed to be positioned within the cell structures of the median assembly before final assembly, rather than requiring post-assembly drilling and insertion. This preliminary configuration of the median assembly simplifies the overall manufacturing process by integrating the cooling and fixing functions into the structural design from the outset.
Solution Approach 2:
The invention merges multiple functions into the median assembly: structural support, acoustic insulation, cooling air flow pathway, and positioning for fixing elements. By combining these functions into a single integrated component rather than separate elements requiring multiple assembly steps, the manufacturing complexity is reduced. The fixing elements are integrated with the cell structures, and the cooling pathways are built into the median assembly geometry, eliminating the need for separate through-hole drilling and assembly operations.
3Strength
If fixing elements penetrate the first skin for cooling, then attachment strength is improved, but acoustic insulation and manufacturing complexity worsen
Solution Approach 1:
The fixing elements are positioned in a different spatial dimension - within the cell structures of the median assembly rather than penetrating through the first skin from the external side. This dimensional repositioning allows the fixing elements to achieve adequate attachment strength within the internal cellular structure while avoiding the creation of through-holes in the first skin that would compromise acoustic insulation. The cell structures provide sufficient mechanical anchorage without requiring external penetration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves cooling efficiency and simplifies assembly while maintaining maximum acoustic insulation by directing airflow through the median assembly to cool attachment structures without penetrating the first skin layer.
Implementation Method 1
the damping and stopping device 23 is fixed to the composite wall 20 by means of fasteners 36 passing through the first and second skins 30, 32, which allows them to be cooled by contact with the airflow circulating in the cold section 8
Implementation Method 2
The composite wall 20 comprises a first skin 30 extending opposite the cold part 8 and a second skin 32 extending opposite the hot part 12, as well as a median assembly 34 forming a plurality of cells between the first and second skins 30, 32
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Rear assembly for a turbojet engine nacelle, comprising at least one composite wall (20) separating a cold portion (8) from a hot portion (12) comprising an element to be cooled (23), the composite wall (20) comprising first and second skins (30, 32) which extend facing the cold portion (8) and the hot portion (12), respectively, and which are separated from one another by a middle assembly (34) comprising cells delimited by internal walls. The first skin (30) comprises a plurality of through-openings (48) connecting the cold portion (8) and the cells, the internal walls (42) comprising through-openings (44) connecting the cells to one another, and the second skin (32) comprising a through-opening (52) that opens facing the element to be cooled (23).