SINOPSIS

This work investigates the relationship between the oxygen balance (OB) and carbon residue of gun propellant. The OB (or OB%) is an expression that is used to indicate the degree to which energetic materials can be oxidized. For single- or double-base propellants, it is almost always composed of carbon, hydrogen, oxygen and nitrogen elements, and the OB value is usually designed negatively. If the OB value is very low, there may not even be enough oxygen to form at least carbon monoxide from the carbon such that carbon residue may be released, which can lead to gun muzzle smoke. In this study, the combustion products of a double-base propellant with different OB values were calculated by a method based on the minimum free-energy principle. Dibutyl phthalate (DBP) was selected as the agent to adjust the OB of the propellant; the OB value was changed from −29 to −103%. The results show that the combustion of propellant can generate carbon residue when the OB of the propellant is lower than a critical value. The amount of carbon residue will increase with the descent of the OB. For a double-base propellant, the critical OB value can be decreased by increasing the nitroglycerin (NG) content or combustion pressure. Based on the computational results, the critical OB value is established as a function of both the combustion pressure and NG content. In addition, the experimental confirmation on the computational results was carried out by closed vessel experiments, and the results of the computations are basically consistent with those of the experiments.