Curved Tooth Coupling for Miniature Gas Turbine Rotor Alignment
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Solution Overview
Problem
Miniature gas turbine engines face reliability and manufacturing cost challenges due to the instability caused by thermal expansion and centrifugal growth in conventional radial interference fits between compressor and turbine components, leading to potential misalignment and balance issues.
Innovation Solution
A rotor assembly with a centrifugal compressor wheel and turbine wheel interconnected via a curved tooth coupling and a tie bolt, which maintains axial engagement and radial torque transmission, enhancing alignment and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a radial interference fit is used to couple the compressor wheel and turbine shaft, then the coupling is simple in structure, but the reliability deteriorates due to thermal expansion and centrifugal growth causing misalignment and separation
Solution Approach 1:
The curved tooth coupling allows dynamic adjustment of the compressor wheel position relative to the turbine shaft. The teeth can slide along the curved surfaces to accommodate thermal expansion and centrifugal growth, maintaining proper alignment and engagement throughout operation. This dynamic capability resolves the contradiction by enabling the coupling to adapt to changing dimensional conditions while maintaining reliability.
Solution Approach 2:
The curved tooth coupling changes the geometric parameters of the coupling interface through its curved tooth surfaces. This curvature allows for variable engagement angles and positions, enabling the coupling to maintain proper fit and alignment despite thermal and centrifugal effects. The parameter change in the coupling geometry resolves the reliability issue while keeping the structure relatively simple.
2Ease of manufacture
If a radial interference fit is used to couple the compressor wheel and turbine shaft, then the manufacturing process is simple, but the manufacturing precision deteriorates due to difficulty in achieving consistent torque transmitting capabilities
Solution Approach 1:
The curved tooth coupling provides dynamic tolerance compensation that reduces sensitivity to manufacturing variations. The curved surfaces allow for self-adjustment during operation, compensating for minor dimensional variations in the manufactured components. This reduces the stringency of manufacturing precision requirements while maintaining reliable torque transmission.
Solution Approach 2:
The curved tooth coupling creates a composite engagement system where the curved tooth surfaces work together to distribute and transmit torque. This composite action across multiple tooth contacts provides more consistent torque transmitting capabilities compared to a single-point interference fit, improving manufacturing precision outcomes.
3Device complexity
If a radial interference fit is used to couple the compressor wheel and turbine shaft, then the coupling mechanism is simple, but the stability deteriorates due to potential separation and misalignment during high-speed operation
Solution Approach 1:
The curved tooth coupling enables dynamic adaptation to thermal expansion and centrifugal growth during high-speed operation. The teeth can slide and adjust their engagement positions along the curved surfaces, maintaining stable alignment between the compressor wheel and turbine shaft despite dimensional changes. This dynamic capability prevents separation and misalignment, resolving the stability issue.
Solution Approach 2:
The curved tooth geometry provides built-in compensation capacity before separation or misalignment occurs. The curved surfaces create a cushioning effect that absorbs dimensional changes and prevents abrupt loss of engagement. This beforehand cushioning capability maintains stability during high-speed operation while keeping the coupling mechanism relatively simple.
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 provides a robust, cost-effective, and reliable coupling mechanism that reduces manufacturing costs and improves the reliability of miniature gas turbine engines by maintaining precise engagement and stability under high-speed and temperature conditions.
Implementation Method 1
the tie bolt extends between the shaft and the turbine wheel to bring the first curved tooth coupling into compression with the second curved tooth coupling
Implementation Method 2
a first curved tooth coupling on the compressor wheel and a second curved tooth coupling on the turbine wheel interconnected with the first curved tooth coupling
Data Source
AI summary
A rotor assembly for a miniature gas turbine propulsion system comprises a centrifugal compressor wheel, a turbine wheel, a shaft and a tie bolt. The centrifugal compressor wheel includes a first curved tooth coupling, and the turbine wheel includes a second curved tooth coupling interconnected with the first curved tooth coupling. The shaft extends from the centrifugal compressor wheel, and the tie bolt extends between the shaft and the turbine wheel to bring the first curved tooth coupling into compression with the second curved tooth coupling. As such, the compressor wheel and the turbine wheel are assembled and remain, over the operational envelope of the propulsion system, in a reliably robust aligned configuration.