مجله تحقیق و توسعه مواد پرانرژی
سال هشتم شماره 1 (پیاپی 16، بهار و تابستان 1391)

One of the difficulties in the liquid fuels is theirs shelf life. These fuels, like other chemicals, dont meet the military specifications after a period of time due to their destructive reactions. This variation from the specifications, changes the chemical and physical properties of the fuel and its combustion performance. This subject is significant because of the fuel long time storage requirements. Thus, it is necessary to specify, control, and decrease the effective parameters and increase the fuel shelf life. One of the important fuels used in aerospace industries, is unsymmetrical dimethyl hydrazine. Studies show that oxygen, temperature, and storage material of construction are parameters affecting the fuel shelf life. Regarding shelf life conditions, presence of oxygen is the most important parameter affecting the storage shelf life of the fuel. Thus, the effect of oxygen on shelf life of unsymmetrical dimethyl hydrazine was investigated empirically. Results show that the shelf life of this fuel strongly depends on the molecular oxygen. The major products of this oxidation are formaldehyde dimethyl hydrazine, dimethyl amine, ammonia, and water. Assuming the zero and first order reactions, the oxidation rate constants were determined at storage temperature (25 °C) to be 0.021mol.lit-1.min-1 and 0.00023 min-1, respectively.

Gel propellant are new ones that have the same properties as solid and liquid propellants. Inhibited red fumed nitric acid is a common oxidizer that because of acceptable properties like high density and acceptable boiling and freezing points is a good oxidizer for gel formation. Different kind of gallant have been used for gellation of IRFNA among which, the fumed silica has most application. Hydrocarbon bonds between IRFNA and the gallant is known as the principal factor of gel formation. In this paper the different kind of gallant for gellation of IRFNA and also suitable additives for improving the gel properties are investigated.

The formulation of the composite propellant is constituted of solid particles of (ammonium perchlorate) as well as metal fuel such as aluminum particles which are all dispersed homogenously within the Binder matrix. The availability of these solid particles affects the combustion mechanism of the composite propellant and causes the betterment in the performance parameters of rocket such as: increasing in specific impulse and burning time. The very accentuation of this paper is upon the acceleration effect and the derived phenomena of its (including agglomeration, pit formation by means of solid particles within propellant matrix, heat feedback, heat transferring -made of agglomerates- unto the surface of propellant which is being burnt) on the combustion mechanism of composite solid fuels which is conducive to increase in the burning rate of propellant. The rest of the paper is devoted to effects of miscellanies of factors such as pressure, static burning rate, and Al content upon increasing the burning rate of propellant.

Environmental pollution from the use of lead compounds and their adverse effects on employees, users and consumers of ammunitions is a serious problem in the military industries. Primary explosives such as lead azide and lead styphnate are essential portions of initiators and have wide consumption in military industries for producing initiators, tinder and detonators. These leaded compounds have been listed to replace with other alternatives. This article is reviews of the green primary explosives that are compatible with the nature and are suitable replacements for leaded compounds.

One of the effective factors in choosing a combination of rocket propulsion is ignition delay. In propulsion applications, optimizing the ignition delay time is very important. In liquid rocket, spontaneous combustion or hypergolic ignition is a very useful property to makes sure that the engine is turned on. Excessive delay leads the accumulation of non-reacted propellant in the combustion chamber before ignition and caused combustion instability which results in mechanical stresses imposed on the body and rocket hardware. On the other hand, the short ignition delay can damage the injector. In this paper, after definition of the ignition delay, its range and relation with hypergolic propellants, the importance of ignition delay and its measuring methods is investigated and the parameters affecting the ignition delay is presented.

In this Article the use of nanoaluminum particles in solid propellant based on ammonium perchlorate (AP) have been reviewed. The effect of aluminum nanoparticles as metallic fuels in solid propellants on performance parameter such as burning rate, initiation temperature combustion and residual ash particle size reduction are investigated. Significant increases in propellant burning rates, shorter ignition delays and shorter agglomerates burning times were recently obtained for composite solid propellant formulations containing nanoaluminum particles. As Al particle size is decreased, the Al combustion takes place closer to the propellant burning surface, with a corresponding large increase in burning rate.

In the present study a method for investigation of possibility of detonation in high speed flows based on available experimental data have been described. For this purpose, different kind of important parameters that were needed for possibility of detonation were evaluated. These parameters are included; detonability limit of the mixture and effect of neutral additives, kind of confinement, geometry and dimensions, type of initiation including direct and DDT initiation and special properties of the mixture like; pressure, temperature and velocity. The information and how to use these parameters for analysis of problem was presented. This method is specifically used in discharging of a supersonic jet containing hydrogen in three different modes of operation. the results show the limit area of danger is located 2 to 8 meters in area outlet. On the other hand, considering of experimental data was demonstrated that the presence of water vapor can decrease the possibility of detonation and The maximum permitted percentage of water vapor has been determined about 30% for detonability of the mixture. With considering high percentage of water wapor in the area of danger it is determined that this region is not detonable.