Authors: Ryan Hill and Logan McLeod

This work presents a method for simulating the heating of machine gun barrels during burst firings. The method utilizes a two-dimensional axisymmetric finite element model which solves the highly transient convection input on the bore wall, conduction through the barrel, and convective and radiative cooling on the outside wall. The transient input is derived from a coupling of a lumped-parameter interior ballistics code with a one-dimensional compressible flow model which includes the discharge of the combustion product gas behind the projectile. This transient convective boundary condition can be repeated as desired for arbitrary firing schedules. Finally, an example simulation is performed on a small caliber machine gun and compared with experimental data.

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Authors: Ryan Hill and Logan McLeod
Two assumptions are often made by lumped-parameter codes in the analysis of dual-chamber guns: (1) that the gas enters the large chamber at the propellant flame temperature, and (2) that the flow between the chambers is that of an ideal gas. An investigation on the effects of these two assumptions was performed by creating three lumped-parameter codes: one that maintains the two assumptions above, and two that conserve flow energy of the gas instead of maintaining a constant temperature. Of the latter two models, one uses an ideal gas and the other uses a noble-abel gas for the flow calculations. In this work, the noble-abel gas equation of state will be discussed in detail as well as its implications to the gas flow. Then, descriptions of the three approaches to the gas flow model will be presented, followed finally by a comparison of simulation results from the three models.

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