فصلنامه مواد پر انرژی
سال هفتم شماره 4 (پیاپی 17، زمستان 1391)

The most important indicator of dynamic optimization of system design in open cycle engines is known, minimize of the maximum amount of start transient regime parameters. How decreasing the maximum amount of transient regime parameters; that is one of the most important factors in defect of this kind of Engines, is the main objective of this paper.The procedure is based on two different simulation models; the software program C++ and Matlab Simulink. By regard to considered Engine condition; at first we present important factors in decreasing of maximum amount of transient regime parameters, and then will show their effects by comparing of simulation prediction and hot test results. Finally, results of engine hot test are compared with model and shows acceptable accuracy of simulator code.

In this research, a computer code is developed to predict the interior ballistic parameters (variation of pressure and temperature of propellant gases, location and velocity of projectile versus time) based on Baer&Frankle zero dimensional method. Nonlinear burning rate equation has been used. Volume term in the equation of state has been modified considering co-volume of propellant and igniter gases and the overlap between projectile, cartridge and recoil. Results obtained from this method are improved by correcting heat loss relations and considering energy losses due to recoiling parts of the gun and projectile spin. The calculated results are in good agreement with experimental data as well as the data reported from other interior ballistic codes. Investigation was performed to reveal the effect of co-volume of propellant gases, engraving force and shot-start pressure on the breech pressure. Also effect of igniter properties on the temperature and pressure history of burnt gases has been studied.

In this research the effect of the tumbling perforation of blunt-faced cylindrical projectiles in moderately thick aluminum plates is presented. The perforation process – depend on the impact angle in normal and oblique impact – consists of four stages: erosion, plugging, hole enlargement and petaling. The modeling in the plugging stage consists sequentially of cratering, plug formation, plug separation, plug slipping and post perforation deformation. In this analytical model, the target material is considered to be rigid perfectly plastic, while the projectile is regarded as adeformable. material Projectile deformation depend on relative velocity of projectile occurs in three mode: erosion, flattening and rigid projectile. The effect of the frictional force is considered too. The new analytical results were found to be in good agreement with experimental results.

1,3,5-Triamino-2,4,6-Trinitrobenzene (TATB) is an explosive that possesses excellent thermal stability and sensitivity characteristics. These properties make TATB an attractive candidate for military and civilian applications. The aim of this study is the synthesis of TATB using available reagents and equipment. Thus, TNT was used as starting material in the synthesis of TATB following six steps including the oxidation of TNT to Trinitrobenzoic acid with Sodium dichromate and concentrated Sulfuric acid (yield 60%), decarboxylation to Trinitrobenzene (yield 68%), reduction to Triaminobenzene with metal powder and Hydrochloric acid or Hydrazine hydrate (yield 55%), protection of the Amine groups to synthesize Triacetamidobenzene and finally the nitration and deprotection reaction by hydrolysis reaction (yield 55%).

Fiber-Reinforced Plastic (FRP) laminates have received more and more attention due to their high specific strength and high specific stiffness. They are used vastly in various industries such as aerospace, naval, automotive and body armor. Numerous studies have been conducted to identify the deformation mechanisms which occur during dynamic penetration and perforation of FRP laminates. Wen presented an analytical model to predict depth of penetration, residual velocity and ballistic limit for projectiles with different noses. He neglected friction between nose of projectile and target. In this paper, wen's model is investigated with friction between nose of projectile and target, so new correlations are derived. A new model is presented for projectile with ogive and semi-spherical nose. Newton second law is used to predict perforation of FRP laminate. Several experimental tests performed for ogive nose projectile and carbon/epoxy laminate. According to experimental results an equation for empirical constant β is derived. Analytical results for new model and Wen's model was compared with experimental result. Analytical results in the new model are in good agreement with experimental ones. This indicates that new model is more accurate than the Wen's model.

In this work, a two dimensional CFD model has been used to investigate both hydrodynamics and mass transfer and their effects on hydrogen solubility in a hydrocarbon fuel. This work has been done based on two fluid (Eulerian-Eulerian) model and finite volume method, along with standard k-e model to address turbulent behavior of both phases. The bubble rise velocity obtained using the present model has been compared with the experimental results and showed a good agreement with experimental data. The CFD model correctly exhibited the general behavior expected from hydrodynamics of the system. For gas superficial velocities up to 3.0 cm/s, the gas volume fraction and volumetric mass transfer coefficient were obtained up to 0.091 and 0.054 s-1, respectively. Results of mass transfer run showed that hydrogen concentration in liquid fuel is increased progressively until reaching its equilibrium value. For hydrogen mass transfer coefficient of 0.0004, 0.0008 and 0.002, the time required to reaching the equilibrium liquid concentration is about 120, 60 and 25 sec. respectively. Therefore, through selection of an appropriate system geometry and gas velocity, an appropriate mass transfer and gas distribution in liquid for hydrogen solubility in liquid fuel can be achieved.

In this article, dynamic response of the thick cylindrical shell subjected to mechanical moving pressure has been investigated. The temperature distribution varies with respect to the thickness and moving along the length of the thick shell. First, the equations of motion have been derived using the Hamilton’s principle and the first order shear deformation theory. These equations are the systems of partial differential equations with constant variables. They have been solved using the converted ordinary differential equations under various load conditions. The Results of the present analytical method have been verified by comparing with finite element results using the ABAQUS software. The Comparison of the results with the finite element method shows that the first order shear deformation theory can predict the dynamic response of the thick cylindrical shell successfully.