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Edward F. James and Stuart Banks
McDonnell Douglas Aerospace
Seabrook, Md. USA
Stephen Castles
NASA, GSFC
Greenbelt, Md. USA
ABSTRACT
NASA/Goddard Space Flight Center (GSFC) has been evaluating Stirling cycle coolers produced by Sunpower, Inc. The particular coolers being evaluated are two versions of the Model M77 with active counterbalancers. This paper reports on an investigation into the residual vibration characteristics of these machines using several different techniques for activating the counterbalancer.
The two versions of the M77 cryocooler are nearly identical except that the counterbalancer on the latest generation is adjustable to allow both axial and lateral vibration levels to be minimized. A comparison of the residual vibration levels of the two versions of the M77 is provided.
The relative change in the vibration signature (for the lowest 6 harmonics) is measured over time for both versions of the M77 cryocoolers, with the counterbalancer driven by a set, characteristic waveform chosen to initially minimize the residual vibration. These measurements are made as a function of heat sink temperature, power level, and load. Also, the effect that machine run time has on the vibration signature is determined. In addition, possible low cost and simplified methods for driving the counterbalancer will be discussed. These techniques result in various levels of vibration reduction. Typical results are presented.
Cryocoolers 9, p. 697 (Plenum Press, 1997)