Fan Outlet Guide Blade Platform Rib Design for Vibration Strength
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Solution Overview
Problem
The increasing diameter and length of fan outlet guide blades in aircraft engines for higher bypass ratios lead to reduced rigidity and natural vibration frequency, making it challenging to maintain vibration strength while reducing weight.
Innovation Solution
The implementation of first and second ribs on the platform of the fan outlet guide blade, extending 8 to 30% of the inter-flange distance from the axial center, to reinforce the platform without reaching the flanges, enhancing vibration strength while minimizing weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the fan outlet guide blade diameter and length are increased for higher bypass ratio, then fuel consumption improves, but platform rigidity and natural vibration frequency decrease
Solution Approach 1:
The platform is segmented by adding discrete first and second ribs that divide the platform structure into multiple reinforced zones. These ribs are positioned at specific locations (8-30% of inter-flange distance from axial center) to create localized stiffening without requiring continuous material addition, thus improving vibration strength while controlling weight increase
Solution Approach 2:
The rib reinforcements are applied locally at critical positions on the platform rather than uniformly across the entire structure. The first rib extends from 8-30% of inter-flange distance toward the upstream end, and the second rib extends from 8-30% of inter-flange distance toward the downstream end, providing targeted rigidity enhancement where vibration stresses are highest while minimizing overall weight penalty
2Strength
If ribs are continuously formed from upstream end to downstream end via axial center of platform, then platform rigidity increases, but blade weight increases
Solution Approach 1:
Instead of a continuous rib structure, the invention uses discrete segmented ribs with specific start and end positions. The first rib starts at 8-30% of inter-flange distance from axial center and extends toward upstream end but does not reach the first flange. The second rib starts at 8-30% of inter-flange distance from axial center and extends toward downstream end but does not reach the second flange. This segmentation reduces material usage and weight while maintaining rigidity through strategic placement at critical stress zones
Solution Approach 2:
The ribs are designed to extend partially toward the flanges rather than spanning the entire platform length. By positioning the ribs to cover only the critical mid-section (8-30% from axial center) and stopping before reaching the flanges, the design provides sufficient rigidity enhancement in the most vulnerable area while avoiding excessive material addition that would occur with full-length continuous ribs
Data Source
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AI summary
A platform (41) of a fan outlet guide blade (37) has a first rib (73) and a second rib (75) in an opposite surface (41d) of a flow passage surface (41f) thereof. The first rib (73) and the second rib (75) are formed in portions excluding a predetermined area separated to an upstream side and a downstream side by 8 to 30% of an inter-flange distance (L) between a first flange (43) and a second flange (53) with respect to an axial center (C) of the platform (41), the portions being located on a ventral surface (39v) side in the opposite surface (41d).