A new sliding joint to accommodate recoil of a free-piston-driven expansion tube facility
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This paper describes a new device to decouple free-piston driver recoil and its associated mechanical vibration from the acceleration tube and test section of The University of Queensland’s X3 expansion tube. A sliding joint is introduced to the acceleration tube which axially decouples the facility at this station. When the facility is fired, the upstream section of the facility, which includes the free-piston driver, can recoil upstream freely. The downstream acceleration tube remains stationary. This arrangement provides two important benefits. Firstly, it eliminates nozzle movement relative to the test section before and during the experiment. This has benefits in terms of experimental setup and alignment. Secondly, it prevents transmission of mechanical disturbances from the free-piston driver to the acceleration tube, thereby eliminating mechanically-induced transducer noise in the sensitive pressure transducers installed in this low-pressure tube. This paper details the new design, and presents experimental confirmation of its performance.
KeywordsRecoil Free-piston driver Impulse facility Expansion tube Mechanical vibration
The authors wish to thank Mr. Frans De Beurs for technical support; HMG Hardchrome Pty Ltd for manufacturing support; the Australian Research Council for support and funding; and The Queensland Smart State Research Facilities Fund 2005 for support and funding.
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