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EN
The paper presents a method to determine the burning rate law and the progressivity coefficient of the fine-grained propellants shape. To achieve the objective of this paper, a series of tests were performed in a closed vessel. The results obtained from these tests were processed to determine experimentally the burning rate and the progressivity coefficient of the propellant shape starting from the premise that the burning surface has identical values for the same value of the volume fraction of burned propellant in two closed vessel tests at different loading densities. The experimental determination of the progressivity coefficient of the propellant shape shows that irregularities of the shape of the fine-grained propellants and gradual ignition lead to values completely different from the theoretical ones.
EN
The relation between the burning rate, r, of a solid propellant and the pressure, p, of gases surrounding the burning propellant surface is the basic component of the gas inflow equation. The applicability of a linear form of the burning rate law is limited only to those propellants for which the same pressure impulses, Ip, were obtained during closed vessel tests at different loading densities. To determine the values of the power form of the burning rate law it is necessary to know the values of the energetic and ballistic characteristics of the propellant. In this paper, a method is presented for determining the relation r(p) for which the only input data are the pressure, p(t), of the propellant gases recorded during closed vessel tests (only for a single specific loading density) and information on the shape and geometric dimensions of the propellant grains. An analysis of the possibility of applying the proposed method, through examples of single-base, double-base and multi-base propellants with neutral and progressive characteristics of burning surface changes, was carried out for the purposes of the present study. The qualitative and quantitative results of burning rate analyses prove the validity of the assumptions made.
EN
The effect of the initial temperature on the mechanical properties of spherical single base gun propellant was investigated by means of a compression test, which consisted of compression of a propellant bed conditioned at various initial temperatures. Following this mechanical treatment, the pressed grains (after thermal conditioning at ambient temperature) were tested in a closed vessel. The results from the combination of compression and closed vessel tests supported the assumption that there are two phenomena occurring inside the cartridge at low temperatures which compensate each other; the first is a decrease in the burning rate as the initial temperature is decreased, and the second is grain fracturing occurring on ignition. Additionally, a specific parameter, the specific surface area, turns out to be an appropriate parameter for quantifying the mechanical damage to the propellant grain resulting from the compression test. Tests on the aged propellant have also been conducted.
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