Turbomachine Fan Hub Ratio Reduction via Titanium Alloy and Spline Drive
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Solution Overview
Problem
Current turbomachine fan designs for small turbomachines, particularly in business aviation, face limitations in reducing the external diameter of the hub while maintaining mechanical strength and performance, due to constraints on radial mechanical strength, torsional resistance, and manufacturing considerations, which restrict the hub ratio below a certain diameter.
Innovation Solution
The design incorporates a fan disk with a spline connection between the disk and the drive shaft, eliminating bolted flanges for torque transmission, and uses a titanium alloy for the fan disc, reducing the radial height of the grooves to enhance mechanical strength and allow a smaller hub ratio, while maintaining axial retention of blades through an upstream flange and balancing profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the external diameter of the hub is reduced to lower the hub ratio and improve performance, then the air flow and performance gain, but the radial mechanical strength and torsional strength deteriorate
Solution Approach 1:
The patent changes the material parameter from conventional alloys to titanium alloy, which has superior strength-to-weight ratio. This allows the hub external diameter to be reduced (improving air flow) while maintaining adequate mechanical strength through the superior properties of titanium alloy
Solution Approach 2:
The patent employs titanium alloy as a composite material solution that provides both the strength required for reduced hub dimensions and the weight reduction necessary for performance improvement. The material's inherent properties enable simultaneous optimization of structural integrity and aerodynamic efficiency
2Productivity
If the external diameter of the hub is reduced to lower the hub ratio, then the performance gain, but the weight reduction is limited by manufacturing constraints
Solution Approach 1:
The patent merges the hub structure with the fan disc into an integrated component. This consolidation eliminates the need for separate manufacturing and assembly of the hub, allowing the external diameter to be reduced to optimize performance while the integrated structure simplifies manufacturing constraints
Solution Approach 2:
By changing the material to titanium alloy with superior mechanical properties, the patent enables reduced hub dimensions that would otherwise be制造ually constrained. The material's properties allow for thinner, smaller structures that can be manufactured while maintaining performance and strength requirements
3Ease of manufacture
If conventional bolted flanges are used for torque transmission, then the assembly is simple, but the risk of deformation and rupture increases
Solution Approach 1:
The patent extracts and eliminates the bolted flange connection system from the torque transmission mechanism. By removing this weak link, the design achieves both higher reliability (no deformation/rupture risk at flange joints) and maintains assembly simplicity through the direct spline connection between shaft and hub
4Productivity
If the hub ratio is reduced by radial reduction, then the suction section increases and air flow improves, but the weight gain occurs due to material requirements
Solution Approach 1:
The patent uses titanium alloy's superior strength-to-weight ratio to enable hub dimensional reduction for improved air flow while simultaneously achieving weight reduction. The material properties allow thinner, smaller hub structures that improve suction section and air flow without the weight penalty that would normally accompany such dimensional reductions
Data Source
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AI summary
The invention proposes a fan, in particular for a turbomachine of small size such as a jet engine, having a hub ratio which corresponds to the ratio of the diameter of the inner limit of the incoming air stream (26) at the radially inner ends of the leading edges of the fan blades (10), divided by the diameter of the circle around which the outer ends of the fan blades pass, having a value of between 0.20 and 0.265.