Hollow Rotor Core Cooling for Superconducting Machines
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Solution Overview
Problem
Conventional superconducting rotating machines face challenges in uniformly cooling superconducting coils without causing cold brittleness at extremely low temperatures, and existing cooling methods are inefficient, costly, and impractical due to the need for complex facilities and rotating seal mechanisms.
Innovation Solution
A rotor core with cryogen passages and turbulence promoters, made from non-magnetic materials like SUS316, that efficiently guides cryogen flow to uniformly cool superconducting coils, preventing cold brittleness and reducing weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the rotor core is made of heavy solid magnetic material like iron, then the heat capacity is high which provides thermal stability, but the cooling time becomes excessively long and cold brittleness occurs at extremely low temperatures
Solution Approach 1:
The rotor core is divided into multiple cooling passages that extend through its length, with cryogen flowing through these segmented channels to distribute cooling uniformly. This segmentation reduces the effective thermal mass that needs cooling while maintaining structural integrity.
Solution Approach 2:
A cryogen (such as liquid nitrogen or helium) is introduced as an intermediary cooling medium that flows through the cooling passages. This intermediary transfers heat away from the rotor core material, enabling rapid cooling without requiring the material itself to have low heat capacity.
2Strength
If the rotor core is made of iron-based magnetic material, then magnetic field strength is improved, but cold brittleness occurs at superconducting temperatures
Solution Approach 1:
The material composition of the rotor core is changed from iron-based magnetic material to non-magnetic materials such as aluminum alloys, copper alloys, or composite materials. This parameter change eliminates cold brittleness while the superconducting coils mounted on the rotor core provide the necessary magnetic field strength.
Solution Approach 2:
The rotor core utilizes composite material structures, such as aluminum alloys with embedded cooling channels or composite laminates, that combine mechanical strength with thermal conductivity properties suitable for cryogenic operation without exhibiting cold brittleness.
3Temperature
If conventional cooling methods using cryogen immersion are used, then cooling effectiveness is improved, but facility complexity and cost increase significantly
Solution Approach 1:
The cooling passages are integrated directly into the rotor core structure itself, extracting the cooling function from separate external facilities. The cryogen flows through channels embedded in the rotor core, eliminating the need for separate cryogen storage tanks, pumping systems, and insulation infrastructure.
Solution Approach 2:
The rotor core structure serves multiple functions simultaneously: it provides mechanical support for the superconducting coils, acts as a magnetic shield, and functions as the cooling system conduit. This multi-functionality reduces the number of separate components and simplifies the overall system.
4Weight of moving object
If the rotor core structure is simplified to reduce weight, then rotational inertia is reduced improving dynamic performance, but cooling uniformity deteriorates
Solution Approach 1:
The cooling passages are strategically positioned and dimensioned with asymmetric configurations optimized for uniform heat extraction. The passage distribution, cross-sectional areas, and lengths are carefully designed to compensate for varying heat generation rates in different rotor regions, achieving uniform cooling despite the lightweight structure.
Solution Approach 2:
Cooling passages are arranged in three-dimensional configurations including axial, radial, and circumferential orientations. This multi-dimensional arrangement ensures that cooling reaches all regions of the rotor core uniformly, maintaining thermal stability while keeping the structure lightweight.
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 enables effective and uniform cooling of superconducting coils at -243°C without cold brittleness, reducing weight and facility complexity, while enhancing heat transfer efficiency and maintaining superconductivity.
Implementation Method 1
the superconducting coils are cooled down to approximately -243°C (30K), for example, through a conduction cooling
Implementation Method 2
the superconducting coils are cooled down to approximately -243°C (30K)
Implementation Method 3
A rotor core with cryogen passages and turbulence promoters
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Provided are a rotor core, a method for cooling a rotor core, and a superconducting rotating machine, capable of effectively and uniformly cooling superconducting coils without causing cold brittleness in an extremely low temperature. The rotor core 10, which is made of a substantially hollow cylindrical member of nonmagnetic material, has a cylindrical cavity 13 defined therein and extending in the longitudinal axis of the member. Helium gas 300 is delivered in the rotor core 10 from the proximal to distal sides and vice versa, which ensures a uniform cooling of the rotor core 10. This also ensures a uniform and effective cooling of the superconducting coils.