Hughes Long-Life Linear Stirlings: A Status Report
An update is provided of the reliability growth program for twin-piston linear drive Stirling coolers which has been underway at Hughes for the past six years. Particular interest is drawn to a compressor life test initiated in August 1992. Two teardowns of this hardware have taken place for wear evaluation; these results are included in this report. An initial teardown after 10,600 hours of operation in a horizontal orientation indicated an average wear rate of 17.3 to 25.7 millionths of an inch per thousand hours of operation; this extrapolated to a wear out life in excess of 25,000 hours. A second teardown, after accumulation of an additional 5,100 hours of operation in a vertical orientation, exhibited an accelerated wear rate of 99 to 135 millionths of an inch per thousand hours of operation attributed to cross-bearing wear not associated with orientation. Performance at the end of 15,700 hours of operation was still within acceptable limits. Results and observations of these teardowns are included.
Performance characteristics of the miniature linear twin-piston family of Stirling coolers, embodying the design of the life test unit, are summarized. This small compressor, with a weight of approximately one pound, has been successfully mated with 0.196 inch diameter coldfingers as well as with 0.26 inch diameter coldfingers for those applications where higher performance at elevated ambients is required. Either coldfinger is compatible with slip-in configuration Dewars or with integrated detective assemblies. Cooling capacity of approximately 0.5 Watts has been demonstrated at elevated ambient operation.
KeywordsWear Rate Life Test Reliability Growth Power Draw Linear Cooler
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