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Improving the Performance of Two-Stage Gas Guns By Adding a Diaphragm in the Pump TubeHerein, we study the technique of improving the gun performance by installing a diaphragm in the pump tube of the gun. A CFD study is carried out for the 0.28 in. gun in the Hypervelocity Free Flight Radiation (HFF RAD) range at the NASA Ames Research Center. The normal, full-length pump tube is studied as well as two pump tubes of reduced length (approximately 75% and approximately 33% of the normal length). Significant improvements in performance are calculated to be gained for the reduced length pump tubes upon the addition of the diaphragm. These improvements are identified as reductions in maximum pressures in the pump tube and at the projectile base of approximately 20%, while maintaining the projectile muzzle velocity or as increases in muzzle velocity of approximately 0.5 km/sec while not increasing the maximum pressures in the gun. Also, it is found that both guns with reduced pump tube length (with diaphragms) could maintain the performance of gun with the full length pump tube without diaphragms, whereas the guns with reduced pump tube lengths without diaphragms could not. A five-shot experimental investigation of the pump tube diaphragm technique is carried out for the gun with a pump tube length of 75% normal. The CFD predictions of increased muzzle velocity are borne out by the experimental data. Modest, but useful muzzle velocity increases (2.5 - 6%) are obtained upon the installation of a diaphragm, compared to a benchmark shot without a diaphragm.
Document ID
19980018473
Acquisition Source
Ames Research Center
Document Type
Contractor Report (CR)
External Source(s)
doi:10.1016/0734-743X(95)99837-H
Authors
Bogdanoff, D. W. (Thermoscience Inst. Moffett Field, CA United States)
Miller, Robert J. (NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1995
Publication Information
Publication: International Journal of Impact Engineering
Publisher: Elsevier Science Publishers Ltd.
Volume: 17
ISSN: 0734-743X
Subject Category
Mechanical Engineering
Report/Patent Number
NASA/CR-95-207229
NAS 1.26:207229
Funding Number(s)
CONTRACT_GRANT: NAS2-14031
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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