Cryogenic Coil Assembly With Non-Bonded Compression Fit
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Solution Overview
Problem
Integrated motor-pumps and turbines (IMPs and IMTs) face significant thermal stress challenges when operating at cryogenic temperatures due to unequal dimensional shrinkage of materials, which can lead to structural degradation and inefficiencies, especially when handling low-viscosity liquids like liquid hydrogen.
Innovation Solution
A coil assembly design that layers materials with differing coefficients of thermal expansion (CTE) to form compression fits, using non-metallic spools and non-bonded barrier materials to minimize thermal stress, allowing components to expand and contract independently, and incorporates non-bonded wired connections and key-stock pieces for structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional bonded coil assemblies are used at cryogenic temperatures, then structural integrity is maintained at ambient temperature, but thermal stress causes structural degradation and material failure at cryogenic temperatures
Solution Approach 1:
The coil assembly is segmented into modular units with independent winding packs that can expand and contract independently. Each winding pack is separated from others and from the core by non-bonded barriers, allowing differential thermal contraction without transmitting stress across the entire assembly. This segmentation prevents the propagation of thermal stress that would otherwise cause structural degradation at cryogenic temperatures.
Solution Approach 2:
The invention changes the bonding parameter from fully bonded to non-bonded or partially bonded interfaces. By eliminating rigid bonds between coil windings, barriers, and cores, the assembly allows for parameter changes in dimensional relationships during thermal cycling. The non-bonded interfaces act as compliant joints that accommodate thermal contraction differential between copper windings, ferromagnetic cores, and insulating barriers.
2Stability of the object's composition
If materials with different CTE are rigidly bonded together, then structural stability is achieved at ambient temperature, but thermal contraction differential causes stress and potential failure at cryogenic temperatures
Solution Approach 1:
Non-bonded barrier materials serve as intermediaries between components with different coefficients of thermal expansion. These barriers include insulating materials positioned between copper windings and ferromagnetic cores, and between adjacent winding packs. The intermediaries decouple the thermal contraction of dissimilar materials, preventing direct stress transmission while maintaining electrical insulation and structural organization.
Solution Approach 2:
The invention explicitly accounts for thermal expansion/contraction differences between materials by designing non-bonded interfaces that accommodate dimensional changes. The coil assembly allows copper windings, ferromagnetic cores, and insulating barriers to contract at their respective rates during cryogenic cooling without generating excessive stress. This is achieved through compliant, non-rigid connections that maintain structural stability while tolerating thermal contraction differential.
3Stress or pressure
If non-bonded interfaces are used to reduce thermal stress, then thermal stress is minimized at cryogenic temperatures, but structural integrity and electrical insulation may be compromised
Solution Approach 1:
The coil assembly uses composite material structures where non-bonded barriers combine multiple functions: electrical insulation, mechanical support, and thermal stress accommodation. The barriers are constructed from materials with appropriate mechanical properties that maintain structural integrity while being compliant enough to tolerate thermal contraction. This composite approach allows non-bonded interfaces to simultaneously reduce thermal stress and maintain reliability.
Solution Approach 2:
The non-bonded barrier materials perform multiple functions simultaneously: they provide electrical insulation between windings and cores, maintain structural organization of the coil assembly, accommodate thermal contraction differential, and prevent direct mechanical contact between dissimilar materials. This multi-functionality ensures that eliminating rigid bonds does not compromise structural or electrical integrity, as the barriers compensate for the lost rigid connection.
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 reduces thermal stress and maintains electrical and magnetic properties, ensuring reliable operation and reduced maintenance of IMPs and IMTs at cryogenic temperatures.
Implementation Method 1
layers materials with differing coefficients of thermal expansion (CTE) to form compression fits, using non-metallic spools and non-bonded barrier materials to minimize thermal stress, allowing components to expand and contract independently
Implementation Method 2
unequal dimensional shrinkage of materials, which can lead to structural degradation and inefficiencies
Data Source
AI summary
A coil assembly of a seal-less pump or turbine comprises materials having differing coefficients of thermal expansion that are layered but not bonded together, thereby reducing thermal stresses at cryogenic temperatures. Differences in shrinkage upon cooling provides compressive structural support. Coils are wound on hollow, non-magnetic spools, and a resin is applied for mechanical support, for example by vacuum impregnation. A release agent prevents bonding of the resin to the coils. The hollow spools are then placed over winding cores, such as laminated iron cores, without bonding. During cooling, the non-metallic spools shrink more than the cores, thereby providing compression fits. At ambient temperature, the spools can be held in place by interferences fits, and/or by key-stock pieces. Wired interconnections between the coils can be located within a wire harness cavity, which can be filled with a resin to provide mechanical support, while a release agent prevents bonding.