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

In the current research work, a zero-dimensional code for the internal ballistic of gun analysis has been developed with a deterrent layer propellant. Today, the driving of the deterrent layer is widely used in small and medium-caliber weapons. The deterrent layer is in the form of a thin coating on the surface of a single base or double base gun propellants. The main purpose of this type of propellants is to increase the muzzle velocity by observing the maximum allowable pressure for the weapon. It has been developed for internal ballistic analysis of the thermodynamic model or the next zero-based on Badr software relations. In order to validate the analysis results, experimental results and results of other valid codes related to 20 mm weapon and 30 mm laboratory weapons were used. The code is able to analyze the combustion of two-layers propellants with a variety of conventional geometries for a grain. The effect of the engraving force on the accuracy of the examined results and the impact of deterrent layer on internal ballistic of gun performance has been discussed. The results show that in case of using the deterrent layer with increasing the load density can be reach to higher muzzle velocities with maintaining maximum allowable pressure. The investigation on M55A2 ammunition demonstrated 9.5% increasing in muzzle velocity by using of deterred propellants rather than undeterred propellants.

When dealing with research and development of the gun propellants, a less expensive, quicker and safer process of the closed vessel evaluation adopted can be used rather than the gun firing test. In the current research work, a computer program (BRCBADR) has been developed for in order to obtain the burning rate reduction coefficients from the closed vessel test data. Correct The correct determination of the thermo-chemical properties of the propellants provides accurate results of interior ballistics analysis. The BRCBADR code has been developed based on a zero dimensional model for evaluating pressure history of burning propellants in a the closed chamber. A new curve fitting method based on the shooting Shooting algorithm is used to calculate burning rate coefficients. In this program, the experimental values of impetus and co-volume have determined from the Noble-Able equation of state. The results of present code are in well agreed agreement with the results of other validated codes. Using of burning rate calculation method has resulted in accurate muzzle velocity prediction (less than one percent error) from 122 mm gun firing. The results of This this research showed that,exhibited the regardless of slivering effects during the burning of seven perforated cylindrical grains, while resulted tothe additional unreal impulse is applied to the projectile.

In the current research, 3D simulation of the projectile movement with a diameter of 5.56 mm, has been considered in the barrel with 48.26 cm length. The ideal gas and Abel-Nobel equations of state have been used to solve the gas phase equations. 6DOF solver has been applied to evaluate the projectile- fluid interaction and solved in the coupled manner with continuity, momentum, and energy equations. To reduce the computational time, the projectile initial position was considered 15cm farther from the breech and initial conditions have been obtained from Quickload software and introduced into Fluent. In the experimental study, two light screens and an electrically insulated firing pin have been used to measure the muzzle velocity and projectile exiting time. The relative deviations of the ideal gas and Abel-Nobel equations of state were almost 6.38, 0.76 percent in muzzle velocity, and 1.1, 0.21 percent in residence time computations respectively. The simulated transient velocity of the projectile was also compared with Quickload software results and the close agreement was achieved. Simulation results include temperature, velocity, and pressure contours inside and outside of the barrel during the projectile movement. Temperature-time, pressure-time, displacement-time, and velocity-time curves of projectile were reported using ideal and Abel-Nobel gas equations of states and compared. Also, one of the important results of the simulation was the computation of force exerted on breech which was obtained 5341 N in the present study.

In this study, different flow analysis models in solid rocket motor are presented. Amongst these models, some are not capable of predicting the effects of significant phenomena such as erosive burning and longitudinal acceleration. In order to consider these effects on the internal ballistic, a quasi-one-dimensional model was developed which employs generalized flow equations. A non-viscous and incompressible quasi-one-dimensional flow with friction, mass injection and flow crosssection variation were taken into account in the governing equations. Then, assuming quasi unsteady flow and considering pressure drop and variation of nozzle throat diameter, and also neglecting the heat transfer in the walls, the governing equations were integrated along the engine length at each time increment. Finally, the flow characteristics inside the engine including the distribution of pressure, temperature, and Mach number along the engine as well as functional characteristics of the engine such as chamber pressure during the burning process were determined as a function of time. Erosive burning effects on the burning rate are of great importance at various conditions. Therefore,, the results of the model were compared with the experimental data of Saderholm model

In this study, effects of longitudinal and rotational accelerations on the Internal Ballistic Solid Propellant Rocket are investigated. First, a quasi one-dimensional flow is considered to drive governing equations. By assuming semi- permanent flow and neglecting heat transfer through the walls, at each time increment the governing equations are integrated along the length of motor. Then, using burning rate equations in Greatrix model, variation of different parameters ofInternal Ballisticalong length of motor are obtained at each burning time. Results reveal that the acceleration increases only if the rotational acceleration is negative (towards the propellant). By applying the rotational acceleration, the burning rate increases and the burning time decreases. Also, it is shown that by increasing the rotational acceleration the pressure in the chamber increases. The steady burning rate is the most important factor by which the acceleration affects the burning rate. While the effects of longitudinal acceleration reduces the effects of rotational acceleration, it has negligible effects on the internal ballistic solid propellant rocket. Finally, it can be concluded that for designing solid rocket motor the rotational acceleration is of greater importance than the longitudinal acceleration.

The presently available tear gas grenades used for controlling riot, have certain disadvantages like ability to re launching from rioters due to combustion at low temperature. More over on account of their considerable weight and volume, it was found difficult to transport sufficient number of them. In this regard, making a small grenade free from such disadvantages and to be mobile or gliding on the ground was the main topic of this paper, which includes description of chemical reaction in grenade for designing a nozzle in which the trust of output gases create movement in the grenade. Such a design can include determination of characteristics like throat diameter, nozzle length and its situation on the grenade in a way to provide the expected goals of the grenade. Modeling of the nozzle has been provided by ANSYS CFX software, the required calculations for choosing the body material specifications has been discussed and at the end, analysis of the grenade motion was presented. Due to the unavailability of the burning rate relation of tear material, a new algorithm is proposed to solve the problem.

Grenade launchers renew the interest for the interior ballistic principle of high/low pressure chambers which is applied in them. In this paper for the sake of optimization in the specific grenade launcher the theoretical investigations are carried out. In theoretical modeling special attention is paid to flow of two- phase mixture of propellant gases and unburned propellant from the high -pressure chamber and to continuation of propellant combustion in the low – pressure chamber and the launcher barrel. The system of equations which describes physical processes in the system is improved by using of thermal variation effects of propellant gases in low pressure chamber. To verify the model theoretical results obtained with the aid of interior ballistics software and experimental data from reference [1] are compared. Through theoretical investigations we consider influence of affecting factors on the interior ballistic characteristics of modified concept.

Interior ballistic analysis is very important because ballistic cycle is extremely rapid and measuring process into the gun tube is very difficult. In this article, effect of co-volume considering have been investigated by analytical solution. This parameter is related to interaction between molecules in gaseous phase at high pressure and high temperature. The present model is based on Corner method with linear burning rate. Noble-Able equation of state was used at this model instead ideal gas equation of state. Available volume for propellant gases is reduced as a result of considering co-volume. Therefore pressure and muzzle velocity increased. In this research work, new formulations for analyzing spherical propellant grains have been developed.

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.

In this research, internal ballistics of solid rocket motor (SRM) has been simulated numerically including two phase flow phenomena. The flow field is consisting of combustion chamber, cylindrical grain, and converging-diverging conic nozzle. One-dimensional transient Euler equations has been solved through Jameson method. The mentioned equations are discretized using fourth order Runge-Kutta integration, and spatial discretization resulted to a central difference scheme. The effect of erosive burning, propellant type, two phase flow, and particle diameter are considered. It is seen that pressure is increased at starting of the motor because of erosive burning. Two phase flow decrease efficiency of the motor, and decrease total and specific impulse by changing propellant type from composite two double bases. The results are compared with other references for validation.

In this paper, general grains of solid propulsion systems such as cylindrical grains, multilateral grains and star grains are designed by new method. This method is more rapid in comparison with the others that act base on geometrical breakdown and boundary condition definition. In this method, geometrical definition point and grain production are defined and then the burning surface and geometrical burn back are calculated by analytical method. Benefits of this method are detection of surface and points joints without definition of type breakdown or grain type and direct calculation of burn back by solution of Cartesian equation. Mentioned method is a general technique to model the various types of grains. New geometrical configurations can be reached by this method which haven’t existed yet, so the code have less volume with more processing speed in comparison with the previous code. Visual FORTRAN code is developed which is able to calculate the geometrical burn back and zero dimension internal ballistic for every grain. Erosional burning velocity and temperature variation are modeled in this paper. Thrust, total pressure and temperature are illustrated vs. web burned variations. Finally, results of the burn back analysis code and the internal ballistic simulation code are evaluated by some other existent codes and real cylindrical grain test.

In a large caliber gun, charge determination has vital significance for gaining maximum muzzle velocity. Geometry and material of grains and charge weight (or number of grains) are important variables for charge determination. using internal ballistic software, we can determine the appropriate values of these variables. Determining the shape and material of the grain, makes the charging of a projectile possible. In this simulation program, the changes of the shape of the grain and the changes of its material are applied through shape function and changing the burning rate and special force ratios of the propellant respectively. In this article, an internal ballistic model is explained and evaluated. Then, the appropriate charge for a large caliber APFSDS projectile is determined. Finally, by using determined charge, the experimental results are compared against three sets of predictions obtained with the software to show the simulation accuracy.