Two-Stage Compressor with Metal Bellows for Oil-Free Helium Cooling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional compressor devices used in cooling systems, such as pulse tube refrigerators and Gifford-McMahon coolers, face contamination issues due to oil ingress and have inefficiencies, particularly with helium as the working gas, leading to high helium loss and short service life.
Innovation Solution
A two-stage compressor device utilizing metal bellows to separate gas and liquid volumes, with a pump that compresses the working gas in alternating directions through each stage, enhancing efficiency and preventing oil contamination, and incorporating check valves and heat exchangers for effective gas management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screw or piston compressors are used, then compression function is achieved, but oil from the compressor gets into the working gas and contaminates the cooling device
Solution Approach 1:
The harmful element (oil) is extracted from the system by using a compressor type (screw compressor with oil separator or piston compressor with oil-free operation) that prevents oil from entering the working gas stream, thereby protecting the cooling device from contamination
Solution Approach 2:
An oil separator acts as an intermediary component that prevents oil from the compressor from entering the working gas, serving as a barrier between the compression mechanism and the cooling device
2Power
If balloons are used as compressor elements, then gas compression is achieved, but the balloon casing can scrape or rub on the inner surface of the compressor chamber causing perforations or fissures
Solution Approach 1:
The patent uses a flexible membrane instead of a balloon, providing the necessary compliance for compression while maintaining structural integrity and preventing scraping or rubbing against the chamber walls that would lead to perforations
Solution Approach 2:
The solution avoids using disposable or short-lived components by replacing the balloon with a more durable membrane system that maintains reliability throughout the service life
3Power
If balloons are used as compressor elements, then gas compression is achieved, but the permeability of the balloon casing is too high causing substantial quantities of helium to be quickly lost
Solution Approach 1:
The patent employs a membrane with controlled permeability properties that prevents substantial helium loss while maintaining the flexibility needed for compression operation, unlike the high-permeability balloon casing
Solution Approach 2:
The membrane likely uses composite material construction that combines flexibility with low permeability to helium, resolving the contradiction between compliance and gas retention
4Reliability
If metal bellows are used as compressor element, then oil-free operation is achieved, but the efficiency of the compensation container is unsatisfactory due to interaction with working liquid
Solution Approach 1:
The patent extracts the metal bellows from direct contact with the working liquid by introducing a liquid-tight membrane as an intermediate barrier, allowing the metal bellows to maintain oil-free compression while the membrane prevents efficiency-reducing interactions with the liquid
5Power
If elastic membranes are used in working chamber, then gas compression is achieved, but the airtight, liquid-tight and pressure-resistant seal is comparatively expensive and heavily loaded
Solution Approach 1:
The patent segments the sealing function from the compression function by using a dedicated liquid-tight membrane that handles the sealing requirements, allowing the metal bellows to focus on compression without bearing the full load of sealing requirements
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 improves the efficiency of the compressor device by ensuring oil-free operation and reducing helium loss, thereby extending the service life and maintaining the purity of the cooling system.
Implementation Method 1
a metal bellows (36, 37) which separates a gas volume from a liquid volume
Implementation Method 2
A pump (16) is provided which compresses a working gas (12) present in the gas volume by pumping a working liquid (15) into the liquid volume
Implementation Method 3
The first high-pressure working gas connection (19) is connected to a first heat exchanger (23), and the second high-pressure working gas connection (20) is connected to a second heat exchanger (24)
Implementation Method 4
The first low-pressure working gas connection (21) is provided with a first check valve (18) and the second low-pressure working gas connection (22) is provided with a second check valve (18), wherein the check valves (17, 18) allow working gas (12) to flow in only one direction
Data Source
AI summary
Pulse tube coolers and Gifford-McMahon coolers are used to cool nuclear spin tomographs and cryopumps. To supply cooled working gas, gas compressors and in particular helium compressors are used with rotational or rotary valves. The rate at which compressed helium is introduced into the cooling device and let out again lies in the range of 1 Hz. A problem of conventional screw or piston processors is that oil from the compressor mixes with the working gas and thus contaminates the cooling device. By providing a second compressor stage, a common pump device can be used to pump in both directions, which results in a two-stage compressor device. The working gas is compressed in each flow direction of the working liquid, in one flow direction in the first compressor stage and in the opposite flow direction in the second compressor stage. Thus, the efficiency of the compressor device is improved.