جستجوی مقالات مرتبط با کلیدواژه "گرین" در نشریات گروه "مواد و متالورژی"

After several years, Solid rockets in storage, due to physical and chemical process have been aged and under these conditions performance will largely fall. Because of the risks of keeping aged rockets in depot, solid propellants must be removed and using safe and green methods disposal them. Discharge and disposal of these aged propellants using traditional methods has hazards and environmental pollution. In this article have been investigated safe methods for remove and disposal grain of propellant and other hand some components recovery.

In this paper, production of a double base propellant grains embedded with continuous metal wires by the screw extruder is investigated. The factors effecting the burning rate of the grains are analyzed and selection of suitable metal wires are discussed. Also, manufactured propellants with embedded metal copper, brass and steel wires (diameter=0.25 mm) were tested by Crawford Bomb method. By this process, the continuous metal wires embedded in grain are made straight and arranged properly to meet the design demands. The results showed that axial burning rate of the end-burning grain embedded with one continuous metal wires of 0.25mm diameter is 3.9 times as great as that of the propellant matrix. Also the torsion and rupture in the grains don’t occurred using embedded metal wire.

Numerical simulation of grain burn back has been done in three dimensions. For numerical grain burn back analysis, a numerical code based on level set method has been developed and in order to increase accuracy, cut cell method was implemented for elements which capture interfaces. The accuracy of the code was validated by grains which have analytical solutions. It was seen that the code has acceptable accuracy. Then, the results of burn back analysis for some grain configuration were depicted. Also, an internal ballistic code in zero dimensional was generated to predict the pressure inside the motor, and was linked by burn back analysis code. The simulation results were compared with experimental ones and high accuracy was achieved.

There are different methods for enhancing burning rate of double base propellants. One of this methods is changing composition of the propellant, but if we want enhance burning rate without changing the propellant composition, we must use special methods such as using embedded metal wires. By this method we can increase the burning rate for 400 to 500 percent. This enhancement in burning rate is influenced by wire type and wire diameter. This article discusses about methods of embedded wire in double base propellants and parameters such as material, diameter, thermal conductivity, thermal diffusivity of wire and the gap of wire and propellant.

In this paper, the solid rocket motor’s grain starting process is simulated numerically by solving Navier-Stockes equations in an axisymmetric, transient laminar mode. Explicit maccormack technique is used for solving the equations. Also, to reach the actual state of grain surface burning and to predict its temperature a suitable heat transfer model is used. So that the preheating of the fuel by the flame can be modeled. By solving the conservative equations of mass, momentum, and energy along with related boundary conditions, one can predict the burning time of the first element of the fuel, its place, and the direction of flame propagation. In addition, the time required for the burning of all the surfaces of the fuel and the time in which the motor burning reaches to a steady state condition could be estimated. Results show that a two-dimensional axisymmetric model is suitable for predicting the transient combustion process in solid fuel motors. Also, a motor designer can design the best igniter based on grain type and size. The numerical results are compared with the results of the experimental tests and their accuracy is evaluated.