Study On The Formation Character Of Propellant Charge Residue

As the firing energy source, propellant charge is critical to weapons performance. Against background of modern information warfare, residue caused by combustion of propellant charge can not only lower the firing accuracy and increase the combat-service works, but also be easy to exposure own position, and then weaken own fighting and existence capability. How to reveal the formation mechnism of residue and eliminate or inhibit the generation of charge residue has become one of the key problems demanding urgent solution. Therefore, the main purpose of the work was to investigate the formation mechanism of residue caused by the key propellant charge elements, in which propellant, ignition system and additional charge components are included, through theoretical and experimental research works. The main works are as follows.(1) Formation of propellant residueBased on the thermodynamics and dynamics of propellant combustion reaction, the generation law of propellant residue was studied from oxygen balance, grain thickness and cold wall effects of propellant.(a) Effect of oxygen balance on the formation of propellant residueThe combustion products of propellant were estimated by computational method of minimum free energy, and the relationship between oxygen balance and carbon residue was established, then it was varified by closed vessel experiments. The results show that the combustion of propellant can generate carbon residue when the oxygen balance of propellant lower than a critical value, and the carbon residue will increase gradually with the descent of oxygen balance. In addition, the function of the oxygen balance and the nitroglycerine content, nitrogen content of nitrocellulose, combustion pressure is established based on the computational results.(b) Effect of grain thickness on the formation of propellant residueThe grain thickness distribution of propellant was experimentally measured and statistically analyzed, and the effect of grain thickness distribution on the formation of propellant residue was investigated based on the classic interior ballistic theory. The results show that the deviation of grain thickness exists in active propellant. The propellant with large grain thickness can not burn out in chamber when firing, then form residue. The expectation value or deviation of grain thickness can affect the formation of residue, and the ammount of residue increases with increasing of expectation value or deviation of grain thickness.(c) Effect of cold wall effects on the formation of propellant residueThe possibility and character of propellant residue formed under cold wall effects were investigated by normal-pressure and constant-volume combustion experiments, in which spray water and bronze pillar were used as combustion matrix respectively, and it was varified through firing tests using 5.8mm catridge. In addition, the adhesion of residue was measured by put-off test method. The results show that the combustion of propellant at normal pressure or constant volume can generate residue under cold wall effects, and the adhension of residue is apparently higher than that of original propellant. It indicates that propellant residue is formed under cold wall effects when firing, and it has been confirmed by the firing tests.(2) Formation of ignition system residueThe combustion products of charge in ignition system were estimated by computational method of minimum free energy. The residue was collected through shooting test and normal pressure combustion experiments, and it was characterized by scanning electronic microscopy (SEM) and Xray energy dispersive analysis (EDS). Then the generation law of igniter charge was studied on the basis of theoretical computation and experiments. The results show that the residues are mainly composed of inorganic metal salts, which are the combustion product of the metal elements in the ignition system charge. For firearm, the amount of residue is small and derived from primer mixture in ignition cap. For small carliber gun, the amount of residue is superior and derived from black powder in artillery primer, while for medium or large carliber gun, the residues are mainly from black powder, and the amount of residues are high and increasing with increasing of gun's caliber.(3) Formation of residue from additional charge componentsUsing computational method of minimum free energy, the combustion products of additional charge elements were simulated, and it was varified by closed vessel experiments. The results show that bore-wear reducing additive and flame inhibitor can result in residue in the combustion of propellant charge. The inorganic components of bore-wear reducing additive and flame inhibitor can survive directly or react to form residue in the combustion process, while the organic components (such as olefin and ozocerite) are hard to participate in the combustion reaction and mainly form residue directly.