The Effect of Variable Composition Equilibrium Thermochemistry in Constant Breech Pressure (CBP) Gun Simulations

Report No. ARL-RP-473
Authors: Anthony J. Kotlar
Date/Pages: January 2014; 14 pages
Abstract: The limiting case of the constant breech pressure (CBP) gun is often invoked to predict the maximum velocity or efficiency of a gun system. Typically this calculation is done using a Lagrange pressure gradient and by considering the chamber composition to be chemically inert. In this study, CBP gun calculations are performed with full equilibrium chemistry obtaining throughout the ballistic cycle. The three well-defined thermodynamic states that completely characterize the energetics of this gun system are identified. This method represents an "exact" calculation of the optimized CBP (before burnout), Lagrange pressure gradient, no-loss gun system. A comparison of predicted-to-measured muzzle velocities is made for a number of fielded and experimental guns, and several hypothetical systems are examined. The comparison of calculated muzzle velocities permits an assessment to be made of the importance of chemical reactivity throughout the ballistic cycle.
Distribution: Approved for public release
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Last Update / Reviewed: January 1, 2014