نشریه دفاع هوافضایی
پیاپی 2 (تابستان 1401)

In the present study, fuel injection and hydrodynamic behavior of fuel spray has been studied numerically under the cavitation phenomenon inside the injector chamber in the combustion chamber of the diesel engine using AVL-Fire software. Spray simulation involves the phenomenon of two-phase flow and requires the numerical solution of the survival equations for the gas phase and the liquid simultaneously. The cavitation flow inside the nozzle is simulated using the Euler-Eulerian method. In this method, liquid and vapor fuels are considered as continuous two-phase, and the governing equations are solved separately for each phase. Spray development and decomposition are simulated using the Eulerian- Lagrangian method. In this method, the gas inside the combustion chamber is considered in the Eulerian coordinates and fuel droplets in Lagrangian coordinates. In the simulations carried out for compression, two values of 60 and 100 MPa are considered for a pressure of 2 MPa. The results showed that for both injections, the cavitation phenomenon is created, although the cavitation phenomenon continues only for the injection pressure of 100 MPa until the end of the nozzle outlet. Therefore, the high injection pressure causes an increase in fuel velocity in the injector orifice and causes a cavitation phenomenon. At high pressures, cavitation grows rapidly, resulting in better atomization and lower average particle diameter.

Artillery weapons have an important role in low height artilleries. In the first step of these weapons, due to reach a stable and controllable projectile, aerodynamically, finding angle and the initial velocity are very essential. Until now, scientists have obtained these items by modelling based on ordinary differential equations. But, in this paper, fractional differential equations of the projectile motion, which are very efficient in artillery weapons and more compatible with nature, are introduced. Then some of its properties such as trajectory, range, flight time and maximum height are studied. In addition, an inverse projectile motion is considered, i.e., we consider a problem that we know the position of motion in a special time and then we obtain angle and the initial velocity. In this way, the shooting method is applied. This method is an efficient and applicable method for solving boundary value problems. Finally, in order to study the efficiency and accuracy of the method a numerical example is given.

In this work the temperature role on the evolution of the nanoparticle geometrical shape in CoSe nanoparticle arrays have been investigated. The data showed that temperature can affect the optical band gap, surface morphology and shape but the deposition temperature plays a crucial role in the shape controlling. We present a simple solution processed synthesis route for CoSe nanostructure thin films using chemical bath deposition method. The films were characterized by X-ray diffraction (XRD) for structure characterization, UV-visible spectroscopy for band gap determination, EDAX technique for elemental analysis and scanning electron microscopy (SEM). SEM pictures show nanoparticles shape with temperature.

Cyber technologies will have tremendous growth and development in the next ten years, and this growth will have a great impact on all political, economic, social, environmental and military dimensions of the Islamic Republic of Iran. Given the key role of our country in the region and the growing threats of the domination system, it is important to examine the effects of the emergence of new cyber technologies in the military to develop strategic plans and take advantage of opportunities and threats. Therefore, the purpose of this study is to identify opportunities and threats of emerging technologies in the military field. The present study is in terms of the type of research in the field of applied research, in terms of the research project in the field of future research and in terms of research method in the category of descriptive / analytical research with exploratory view. The statistical population of the study includes 7 experts in the field of cyber and 50 experts in the field of cyber and military, who were selected by snowball method. Based on the results of the analysis of research data, the military opportunities and threats of new technologies were identified and presented in three categories: physical, information and cognitive. The characteristics of this research can be used in the strategic planning of the country's military.

In this paper, two points guidance law of a missile is optimized based on the particle swarm search algorithm. To do so, we need to five-degree-of-freedom equations of the missile and the proportional guidance law to track the target. Next, the parameters of the law guidance are optimized using the particle swarm algorithm. As a result, the movement path of the missile and target on the horizon and vertical plane, acceleration commands, as well as the miss distance are shown. Also, the effect of axial acceleration compensation, gravitational compensation, and updated frequency on the acceleration commands and the seeker's range are investigated on the guidance law.

Heat transfer plays a major role in the design and performance of missiles and vehicles that have rocket driving. The main importance of this discussion is related to the safety range missile materials, especially in areas such as the combustion chamber and nozzle, which are under critical heat. Only one failure is enough to interfere with the operation of missiles. It may also be due to excessive heat in the nozzle throat, a portion of the sheet metal locally damaged. In which case the exhaust gas flow becomes asymmetrically, which led to the creation of inappropriate force vector direction. This leads to an error in the missile guidance to the target and a lot of fuel consumed on the spacecraft to correct its path by secondary driving system. In this project the amount of heat transferred to the chamber for different sections of engine during the simulation by software is calculated, also the coolant conditions and temperatures have been calculated in accordance with existing heat and cooling operation performed in each section. For this purpose, the engine divided into four parts, the combustion chamber, the convergent nozzle, throat nozzle and the divergent nozzle. The rate of heat transferred from the gas chamber (according to the conditions of gas in different sections) as well as the chamber temperature in the vicinity of the coolant and coolant temperature calculated for different sections of each section. Notably, in this research, ANSYS software package is used to create geometry, mesh and simulations.