Abstract
The results of numerical simulations of transient heat transfer in the barrel wall of a 35 mm caliber cannon for a single shot and the sequences of seven shots and sixty shots for chosen barrel steels are presented. It was assumed that the cannon barrel was made of one of the three types of steel: 38HMJ (1.8509), 30HN2MFA and DUPLEX (1.4462). To model the thermal phenomena in the barrel, the barrel wall material was assumed to be homogeneous and the inner surface of the barrel had no protective chromium or nitride layer. The calculations were made for temperature-dependent thermophysical parameters, i.e., thermal conductivity, specific heat and thermal expansion (in the range from RT up to 1000 °C) of the selected barrel steels. A barrel with a total length of 3150 mm was divided into 6 zones (i = 1, …, 6) and in each of them, the heat flux density was calculated as a function of time q˙i(t) on the inner surface of the barrel. Using lumped parameter methods, an internal ballistic code was developed to compute in each zone the heat transfer coefficient as a function of time hi(t) and bore gas temperature as a function of time Tg(t) to the cannon barrel for given ammunition parameters. A calculation time equaling 100 ms per single shot was assumed. The results of the calculations were obtained using FEM implemented in COMSOL Multiphysics ver. 5.6 software.
Highlights
It is well known that modern anti-aircraft artillery systems consist of a number of guns, some of which fire at the designated target, while the remaining guns follow the target without firing a shot. This is due to the timing of the single cannon being fired, which is chosen because the high temperatures in the barrel prevent the gun from being fired
The protective coating is corroded by the structural transformations in the steel layer, which are directly related to the phase transition between ferrite and austenite [3,12,14]
In order to reach the temperature of 800 ◦C of the inner barrel surface, it is often necessary to carry out numerical simulations of the heat transfer in the barrel after firing several dozen shots [14,18,19]
Summary
It is well known that modern anti-aircraft artillery systems consist of a number of guns, some of which fire at the designated target, while the remaining guns follow the target without firing a shot. Since the density ρ and velocity w of the gunpowder gases are functions of time, we have different values of the time-dependent heat transfer coefficient h in the cross-section P1 to P6 of the 35 mm cannon barrel. The calculation results of the heat transfer coefficient as a function of time hi(t) in the six cross-sections P1 to P6 and the gas temperature as a function of time Tg(t) for the 35 mm anti-aircraft cannon barrel are shown, and so the values of hi(t) in the section P1 are valid in the zone S0 and S1, P2 in the zone S2, P3 in the zone S3, etc. In numerical simulations of heat transfer in the cannon barrels, the energy related to the phase transition was included only in the material density and thermal conductivity, while in the specific heat this energy was ignored. Phase transition energy should not be taken into account multiple times, e.g., both in thermal conductivity and specific heat [12]
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