Fan Platform Radial Retention Offset for Hub Ratio Reduction
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Solution Overview
Problem
Existing fan blade platforms in aeronautical turbomachines face challenges in achieving a low hub ratio while minimizing stresses on the tooth and socket of the disc, as conventional upstream retention methods lead to high hub ratios and potential over-stresses at the connection points.
Innovation Solution
The platform design features a radial retention surface offset relative to the bottom wall, combined with an inclined surface that connects the radial retention surface and the main surface of the bottom wall, allowing for a reduced hub ratio and optimized shape to improve fan performance, and an assembly with radially offset axial projections on the disc to reduce stresses and facilitate machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If upstream retention is achieved above the disc tooth with a ferrule, then the platform is securely retained, but the hub ratio increases and excessive stresses are generated on the tooth and disc cavity
Solution Approach 1:
The patent applies dimensionality change by offsetting the radial retention surface from the principal surface of the bottom wall along the radial direction. This creates a stepped configuration where the radial retention surface is positioned at a different radial coordinate than the main bearing surface, effectively using a new dimensional arrangement to separate the retention function from the bearing function, thereby reducing stress concentration on the disc tooth and cavity while maintaining secure platform retention
Solution Approach 2:
The platform is segmented into distinct functional zones: a principal surface for bearing loads on the disc, and a radially offset retention surface for securing the platform upstream. This segmentation allows each surface to optimize its specific function without compromising the other, reducing stress on critical disc components while maintaining reliable retention
2Reliability
If upstream retention is achieved above the disc tooth with a ferrule, then the platform is securely retained, but the hub ratio increases
Solution Approach 1:
By introducing a radial offset between the retention surface and the principal bearing surface, the patent utilizes the radial dimension to achieve retention without extending the axial height of the platform. This dimensional strategy allows the platform to be retained securely while maintaining a compact hub ratio, as the retention function is achieved through radial positioning rather than axial extension
3Productivity
If the platform shape is modified to reduce hub ratio, then fan performance improves, but stresses at connection points may increase
Solution Approach 1:
The patent applies local quality by creating a specific stepped geometry at the upstream end of the platform where the radial retention surface is offset from the principal surface. This localized geometric modification allows the platform to achieve an optimized aerodynamic shape for reduced hub ratio and improved fan performance, while the retained stepped structure at the connection point distributes stresses favorably, preventing stress concentration despite the shape modification
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
This design reduces the hub ratio, enhances fan performance, and minimizes stresses at critical connection points, leading to a more efficient and durable turbomachine assembly.
Implementation Method 1
The bottom wall holds the flow wall in position and also limits its deformation under the effect of centrifugal forces
Implementation Method 2
The bottom wall with a principal surface to bear on a blower disk; and Axial and radial retention surfaces disposed on two axial ends of the platform, characterized in that the radial retention surface disposed on the upstream axial end of the platform is radially offset
Data Source
Figure 1~2
Figure 3A~3B
Figure 4~5
AI summary
The invention relates to a platform (30) to be inserted between two adjacent blades (20) of a fan (2), and comprising a flow passage wall (34), a base wall (36), and axial and radial retaining surfaces. The flow passage wall (34) defines a passage for the flow of air from the fan (2), the base wall (36) includes a main surface (36a) bearing on a fan disk (40), and the axial and radial retaining surfaces are disposed at two axial ends of the platform (30). The radial retaining surface (38), disposed at the upstream axial end of the platform (30), is offset radially in the direction in which the base wall (36) bears on the disk (40), relative to the main surface (36a) of the base wall (36).