Fan Rotor Hub Interference Fit for Air Cycle Machine
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Solution Overview
Problem
Existing fan rotor designs for air cycle machines face challenges in achieving a secure and balanced co-rotation with compressor and turbine rotors, leading to potential imbalance and dynamic issues due to improper fit and stress distribution.
Innovation Solution
The fan rotor design features a rotor body with specific ratios of cylindrical hub portions and a central hub bore, along with circumferential grooves and a hub body that provides a tight interference press-fit with the thrust shaft, ensuring a unitary rigid operation and minimizing stress on components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fan rotor uses a conventional hub design with standard dimensional ratios, then the manufacturing and assembly process is simpler, but the fit with the thrust shaft is improper leading to imbalance and dynamic issues
Solution Approach 1:
The patent applies parameter changes by specifying precise dimensional ratios for the hub portions relative to the shaft bore diameter. The first cylindrical hub portion has an outer diameter ratio of 1.002-1.007 to the shaft bore diameter, while the second cylindrical hub portion has ratios of 1.996-2.007 and 2.051-2.063 to the central hub bore diameter. These controlled parameter variations create an interference press-fit that ensures reliable co-rotation while maintaining manufacturing feasibility through defined tolerance ranges.
2Strength
If the fan rotor hub is designed with tight interference press-fit ratios, then the fit with the thrust shaft is secure minimizing stress, but the manufacturing tolerance requirements become more stringent
Solution Approach 1:
The patent defines specific parameter ranges for the hub outer diameters relative to the shaft bore and central hub bore. The first cylindrical hub portion maintains an outer diameter 1.002-1.007 times the shaft bore diameter, creating a controlled interference fit. The second cylindrical hub portion has outer diameters 1.996-2.007 and 2.051-2.063 times the central hub bore diameter. These parameter specifications provide secure mechanical connection while establishing clear manufacturing tolerance boundaries.
3Reliability
If the fan rotor uses asymmetric hub portion ratios, then the dynamic balance and stress distribution are optimized, but the manufacturing complexity increases
Solution Approach 1:
The patent employs asymmetry by designing the two cylindrical hub portions with different outer diameter ratios relative to the central hub bore. The first cylindrical hub portion has an outer diameter ratio of 1.996-2.007, while the second cylindrical hub portion has an outer diameter ratio of 2.051-2.063. This asymmetric configuration optimizes dynamic balance and stress distribution during rotation, while the ratios remain within controlled ranges to manage manufacturing 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 design ensures a proper fit and reduces imbalance and dynamic issues, allowing the fan rotor to operate securely and efficiently with the compressor and turbine rotors, maintaining stability and performance across various operating conditions.
Implementation Method 1
The first cylindrical hub portion of the hub body is configured to receive into the thrust shaft and the second cylindrical hub portion of the hub body is configured to receive into the fan rotor ring, such that the fan rotor, the thrust shaft, and the fan rotor ring are secured together for co-rotation with minimal stress on the components
Implementation Method 2
The ratios of the outer diameters of the first cylindrical hub portion and the second cylindrical hub portion to the shaft bore diameter and the fan rotor ring bore diameter, respectively, provide a tight interference press-fit
Data Source
AI summary
A fan rotor includes a rotor body that has plurality of fan blades for rotation about a central axis. An annular wall extends radially inward from the rotor body. A hub body extends axially from the annular wall and defines a central hub bore with a hub bore diameter Db. The hub body further defines a first cylindrical hub portion on one axial side of the annular wall and a second cylindrical hub portion on an opposite side of the annular wall. A ratio of the outer diameter of the first cylindrical hub portion to a diameter of the central hub bore is 1.996-2.007, and a ratio of the second cylindrical hub portion outer diameter to the hub bore diameter is 2.051-2.063.