The objective of this project is to develop an improved He compressor to be used in conjunction with a cryocooler cold end currently under development. This improved He compressor will be based upon Scroll technology which is becoming the standard for vapor cycle lubricated compressors. Scroll compressors offer higher efficiency and reliability with less noise and fewer parts than other compressor designs. (Scroll freon compressors, in use worldwide for over four years, attest to this standard of excellence.) This project addresses the special problems of compressing high purity He so that these advantages can be realized in cryogenic applications. To adapt to cryocooler application, this technology must be able to operate without lubricating oil which requires special filtration equipment and limits operating time owing to the need to replace filters. To eliminate lubricating oil, a dry Scroll He compressor will be designed that uses gas bearing technology to support the Scroll and control gas leakage. The major design feasibility issues will be investigated and design solutions demonstrated through analysis and experimental verification. The performance of seals, bearings, and critical mechanical elements will be analysed and adapted for He service. The work will provide a sound basis for designing a feasibility demonstration He compressor stage. The long term goal is to provide such a good, reliable, and maintenance-free compressor that closed-cycle cryocoolers will be preferable to the transfer of cryogenic liquids for cooling.Anticipated Results/Potential Commercial Applications as described by the awardee:The successful development of a dry Scroll He compressor will improve the life and reliability of He cryocoolers by eliminating the need for oil lubricated compressors. Present oil lubricated compressors impose limits on sustained cryocooler operating time because of their need for periodic maintenance and oil filter replacement. This work will create the information needed to design a feasibility demonstration high purity He compressor stage. The compressor will be fabricated and tested during Phase II. The test results will lead directly to the design of a compressor for servicing a cryocooler. Cooling by transfer of liquid cryogens will become as dated as iceboxes are now when cryocoolers are not limited in performance by their compressors. This work will have the ultimate result of making cryocoolers more reliable and useful for the many civilian and military applications that already exist.
