Cryogenic refrigerator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cryogenic refrigerators face challenges in reducing working gas leakage at the sliding surfaces of rotary valves, which affects performance, and increasing the pressing force to improve sealing leads to higher valve drive torque, an undesirable outcome.
Innovation Solution
The design of a cryogenic refrigerator incorporates a rotary valve with a specific configuration where the distance of closest approach between channels is optimized to reduce gas leakage without increasing valve drive torque, by ensuring the centroid of the first channel is closer to the center than the second channel, and the first sealing length is greater than the second sealing length to enhance sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressing force between the first member and the second member is increased to improve sealing performance, then working gas leakage is reduced, but the valve drive torque increases
Solution Approach 1:
The patent applies different pressing forces to different regions of the rotary valve by positioning channels at different radial distances from the center. The first channel (connected to discharge side) is positioned closer to the center than the second channel (connected to expansion space), creating a local quality difference in the sealing requirement. This allows the first member and second member to be pressed together with optimized force distribution, improving sealing where needed while reducing overall drive torque.
Solution Approach 2:
The patent introduces asymmetry in the channel positioning within the rotary valve structure. The first channel and second channel are deliberately positioned at different radial positions, breaking the symmetric arrangement. This asymmetric configuration creates different sealing lengths for different channels, allowing optimized pressing force application that reduces the torque required to operate the valve while maintaining adequate sealing performance.
2Reliability
If the sealing length is increased to reduce working gas leakage, then sealing performance improves, but the valve structure becomes more complex and larger
Solution Approach 1:
The patent implements local quality by providing different sealing lengths for different channels based on their specific requirements. The first channel has a first sealing length while the second channel has a second sealing length, with the ratio optimized to reduce gas leakage. This localized optimization avoids the need to increase the sealing length uniformly across the entire valve structure, thereby reducing overall structural complexity and size.
Solution Approach 2:
The patent changes the geometric parameters of the valve structure by optimizing the ratio between the first sealing length and the second sealing length. By establishing that the first sealing length is greater than the second sealing length and controlling their ratio, the patent achieves reduced working gas leakage without proportionally increasing the overall valve size or structural complexity.
Data Source
AI summary
A cryogenic refrigerator includes a compressor, an expansion space where a high-pressure working gas discharged from a discharge side of the compressor is caused to expand, and a valve. The valve includes a first member including a first channel connecting to the discharge side and a second member including a second channel connecting to the expansion space. The first and second members are configured to rotate relative to and in contact with each other to connect or disconnect the first and second channels. In a plane where the first and second members are in contact, a first distance that is a distance of closest approach between the first channel and a valve circumference defined by a circumference of one of the first and second members having a smaller diameter is greater than a second distance that is a distance of closest approach between the second channel and the valve circumference.