Cryocooler Rotary Joint Sealing With Staged Pressure Sections
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Solution Overview
Problem
Existing cryocoolers face challenges in maintaining efficient seals for high-pressure working gases, leading to leaks into the atmospheric environment due to the pressure differential between the cryocooler and ambient pressure.
Innovation Solution
A cryocooler design featuring a rotary joint with a rotor and stator configuration that divides the clearance into multiple pressure sections, utilizing a working gas seal portion with annular seals and buffer sections to manage pressure differentials and reduce leakage, including a rotor with an annular flat surface and a stator with a semi-enclosed section to enhance sealing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single O-ring is used to seal helium gas in the rotary joint, then the structure is simple, but helium gas leaks to the atmospheric environment due to high pressure differential
Solution Approach 1:
The single O-ring seal is segmented into multiple seals: a first O-ring for sealing helium gas at high pressure, a second O-ring for sealing helium gas at lower pressure, and a buffer gas seal. This segmentation divides the sealing function into multiple stages, with each seal handling a specific pressure range, thereby preventing helium leakage while maintaining structural feasibility
Solution Approach 2:
A buffer gas (such as nitrogen or air) is introduced as an intermediary substance between the high-pressure helium and the atmospheric environment. The buffer gas creates an intermediate pressure zone that reduces the pressure differential across each seal, making the sealing task more manageable and effective
2Reliability
If multiple O-rings and buffer sections are added to improve sealing, then gas leakage is reduced, but the device complexity increases
Solution Approach 1:
The rotary joint structure is designed to perform multiple functions simultaneously: the clearance space serves as both a rotational gap and a buffer gas chamber; the seal portion divides the clearance into multiple pressure sections while also providing sealing surfaces; the buffer gas section acts as both a pressure transition zone and a secondary seal. This multi-functionality reduces the need for additional separate components
Solution Approach 2:
Multiple sealing functions are merged into a single integrated seal portion structure. The first and second O-rings are positioned within the same seal portion, along with the buffer gas seal, creating a unified sealing assembly that handles multiple pressure zones simultaneously rather than requiring separate sealing mechanisms for each zone
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 significantly improves the seal efficiency of the cryocooler, reducing gas leakage from high-pressure sections to the ambient environment by creating intermediate pressure regions that mitigate pressure differentials, thereby maintaining effective cryogenic cooling.
Implementation Method 1
a first high pressure flow path which is a flow path for a first high pressure working gas having a first high pressure higher than an ambient pressure of the cryocooler, and extends from the stator to the rotor through the clearance
Implementation Method 2
a second high pressure flow path which is a flow path for a second high pressure working gas having a second high pressure which is higher than the ambient pressure and is lower than the first high pressure, and extends from the rotor to the stator through the clearance
Implementation Method 3
a working gas seal portion which divides the clearance into a first high pressure section which communicates with the first high pressure flow path, a second high pressure section which is adjacent to the first high pressure section and communicates with the second high pressure flow path, and a pressurization section which is adjacent to the first high pressure section on a side opposite to the second high pressure section. The pressurization section has an intermediate pressure which is higher than the ambient pressure and is lower than the first high pressure
Data Source
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AI summary
A cryocooler (10) includes a compressor (12) which is installed on a stationary portion (50), an expander (14) which is installed on a rotating portion (52), and a rotary joint (100) which performs fluid connection between the compressor (12) and the expander (14). The rotary joint (100) includes a rotor (106) which is fixed to the rotating portion (52) to be coaxial with a rotation axis of the rotating portion (52), a stator (108) which is disposed to be adjacent to the rotor (106) to form a clearance (110) between the rotor (106) and the stator (108) and is fixed to the stationary portion (50), a first high pressure flow path (102) and a second high pressure flow path (104) which extend from the stator (108) to the rotor (106) through the clearance (110), and a working gas seal portion (120) which divides the clearance (110) into a first high pressure section (126) which communicates with the first high pressure flow path (102) and a second high pressure section which communicates with the second high pressure flow path (104).