Segmented Nacelle Lipskin for Ripple-Free Aerodynamic Forming
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Solution Overview
Problem
Conventional lipskins for engine nacelles are costly and time-consuming to produce due to multi-stage forming processes, often resulting in ripples or waves that cause premature transition from laminar to turbulent airflow, increasing fuel consumption and requiring close-out panels.
Innovation Solution
A lipskin assembly comprising separately formed first and second segments, coupled at the hilite, using superplastic or non-superplastic stretch-forming to reduce or eliminate ripples and waves, with a linear facesheet and concentric cores for noise attenuation and structural rigidity, eliminating the need for close-out panels and complex forming processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a unitary lipskin is formed through multi-stage spin-forming and stretch-forming, then the need for transverse weld lines is reduced, but the manufacturing cost and time increase significantly
Solution Approach 1:
The lipskin is divided into multiple segments that are formed separately and then joined together. This allows each segment to be formed using simpler, faster processes while maintaining overall airflow continuity through careful design of the segmentation locations and joining methods.
2Shape
If stretch-forming is performed on a unitary lipskin with curvature around the hilite, then the lipskin shape is achieved, but complex fixtures and jaws are required
Solution Approach 1:
By segmenting the lipskin, each segment can be formed using simpler fixtures without the need for complex bull nose fixtures and jaws. The segmentation breaks the complex curved geometry into manageable portions that can be formed with standard equipment.
Solution Approach 2:
The segmentation approach changes the problem from forming a complex 3D curved shape in one piece to forming multiple simpler shapes that are then assembled, effectively moving part of the complexity resolution to the assembly dimension rather than the forming dimension.
3Strength
If a unitary lipskin is formed through multi-stage forming, then the lipskin structure is created, but ripples or waves appear on the outer barrel portion
Solution Approach 1:
Segmenting the lipskin allows each segment to be formed with better surface control, avoiding the accumulation of forming errors that lead to ripples and waves in unitary forming. The segmentation breaks the long forming process into shorter stages with better dimensional control.
Solution Approach 2:
By changing the forming parameters through segmentation, each segment can be formed with optimized parameters for its specific geometry, resulting in better overall surface finish and reduced ripples compared to attempting to form the entire lipskin in one piece.
4Shape
If the lipskin extends from the first edge to the second edge as a unitary structure, then the inlet and outer barrel are defined, but close-out panels are required downstream of the second edge
Solution Approach 1:
The lipskin is segmented such that the second segment extends sufficiently downstream to eliminate the need for separate close-out panels. This segmentation strategy integrates the close-out function into the lipskin structure itself, reducing overall assembly complexity.
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
The solution results in a lightweight, efficient, and less expensive engine nacelle with reduced noise and fuel consumption, improved structural integrity, and simplified manufacturing, while maintaining airflow stability and noise attenuation.
Implementation Method 1
using superplastic or non-superplastic stretch-forming to reduce or eliminate ripples and waves
Data Source
AI summary
A lipskin for a nacelle includes a generally annular first lipskin segment that extends generally upstream from a first lipskin edge to a forward edge. The forward edge is proximate to a hilite of the nacelle. The lipskin also includes a generally annular second lipskin segment that extends generally downstream from the forward edge to a second lipskin edge. The second lipskin segment is oriented generally concentrically about the first lipskin segment. The first lipskin segment and the second lipskin segment are coupled together at the forward edge.