A Heat Transfer Study in Folded Ammunition Gun Tube Chambers.

摘要

Time dependent heat transfer analyses have been performed for folded gun tube chambers in that part of the gun tube that is sandwiched between the folded part of the shell casing and the projectile. The asymmetric configuration was believed to introduce 3-dimensional effects so that peak temperatures could not be determined adequately by 2-dimensional analyses. Calculations performed, however, showed that for the single round firing of a projectile a 1-dimensional representation could adequately estimate the peak temperature except for the interior corner region of the propellant capsule which required a 2-dimensional model. A representative set of time- and space-dependent gas temperatures and heat transfer coefficients for conventional unfolded ammunition was supplied by BRL. Maximum surface temperatures were found to occur at a region (named Location 13) near the origin of rifling. Data from this location was used for a 1-dimensional analysis of a non-corner region and a 2-dimensional analysis of a corner region. The calculated temperature rise for an SAE 4340 steel non-corner surface was 1003 deg C (1836 deg F). When a brass layer was used to simulate the cartridge case, the temperature rise was only 660 deg C (1220 deg F) for a non-corner region. However, for a corner region, the brass-coated surface temperature reached a maximum of 1099 deg C (2010 deg F). The results for the interior corner are only tentative because significant approximations were required to model the geometry and to specify the boundary conditions.