AiMT Volume 15 (2020), Issue 2

2020 Author Index

The Effect of Biodiesel on Combustion, Performance and Emission Characteristics of DI Diesel Engine

H. Hai Nguyen and Š. Čorňák

Biodiesel fuels play an important role in addressing issues such as food security and environmental pollution. Diesel oil fuel and biodiesel-diesel blends (including B5S, B10S, and B100S which are produced from the rubber seed oil by supercritical methods) are going to be examined in this study. Engine performance, emissions and combustion characteristics of diesel engine were studied. The results of this experimental research show that the oxygen content of biodiesel helps to improve combustion, reduce ignition delay and decrease a significant amount of smoke density emitted from the engine; however, improved combustion has resulted in a slight increase in the amount of NOx. The results from this study have made contribution to the development and use of biodiesel fuel.

Keywords: biodiesel, combustion process, rubber seed oil, supercritical method.

Pages: 221–230  [References]   [Download Citation]

Development of a Method for Boundary Determination of the Noise-resistant Area of the UHF/VHF Band

O. Iohov, K. Tkachenko, V. Maliuk, S. Horielyshev and S. Herasimov

A method is proposed for determining the boundaries of the maximum largest zone of stable radio reception in the UHF/VHF range using beam antenna system under the action of several sources of radio interference located at different altitudes. The increase in the size of the stable radio reception area is ensured by the optimal orientation of the antenna arrangement at each point in azimuth and angular altitude using the radio communication channel model. To determine the coordinates of the map points belonging to the boundary, a modification of the wave algorithm is proposed. The conducted experimental studies for the MototrboTM DP4800 and Kenwood TK-8302 radio equipment allow concluding that the theoretical positions and computer simulation analysis results obtained are reliable.

Keywords: defensive electronic countermeasures, interference immunity, isoline, wavelet algorithm.

Pages: 231–246  [References]   [Download Citation]

Contribution to Compressibility Modelling in the Estimation of Forces Acting on Projectile Fragments

E. Kljuno and A. Catovic

The compressibility model was developed and applied to generalized model for prediction of aerodynamic forces acting on irregularly shaped body, such as HE projectile fragments. Model assumes adiabatic compression of air in front of high-velocity fragment since the motion of the fragment is an extremely fast process relative to the heat transfer process. The equation of the state of the ideal gas is adopted. Analysis of results and comparison with results obtained by numerical simulation (CFD software) and experimental data show this correction model significantly reduces the relative error of aerodynamic force modelling in the relevant area of the high velocity of the fragment, when the air compression is significant.

Keywords: aerodynamic force, aerodynamic moment, compressibility, fragments.

Pages: 247–263  [References]   [Download Citation]

Mathematical Modeling of Shooting from Moving Carrier

A.M. Lipanov, I.G. Rusyak, V.G. Sufiyanov and S.A. Korolev

The work is devoted to the development of software complex for modeling the dynamic characteristics of a moving carrier in burst firing mode and to the study of their impact on shooting accuracy. A mathematical model for mechanical system of moving carrier is given, which allows to take into account the movement and vibrations of the helicopter, as well as the mutual influence of the system “helicopter – rocket-gun armament”. The research results of the dispersion of projectiles and rockets in serial firing, depending on the parameters of the movement of moving carrier and the shooting mode, are presented. The paper gives a description and outlines working principles of the software complex for visualization of simulation results.

Keywords: burst fire, dispersion of projectiles and rockets, external ballistics, mathematical modeling, mechanical system, moving carrier.

Pages: 265–278  [References]   [Download Citation]

Preparation and Characterization of Magnesium/Teflon/Viton Mixtures for Tracking Flares

S. Quang Dam, M. Van Vu and L. Do Duc

This article examines the influence of fuel/oxidizer ratios and particle sizes of the fuel on combustion characteristics of the pyrolant based on magnesium, polytetrafluoroethylene, and Viton such as heat of explosion, the specific volume of gaseous products, burning rate, and IR intensity. Based on the theoretical and experimental analysis, an appropriate ingredient and particle sizes of components were chosen to meet the requirement for tracking flares. The pyrolant has a medium autoignition temperature and a low sensitivity to friction. It means that the pyrolant is quite safe in transportation, storage, and use.

Keywords: combustion, MTV mixtures, infrared radiation, tracking flares.

Pages: 279–286  [References]   [Download Citation]

Evaluation of Retina Exposition by Optical Incapacitating Device

F. Racek, T. Baláž, J. Leuchter, J. Krejčí and J. Bajer

It has turned out that the usage of non-lethal weapons is an effective way of tackling adversaries in many security scenarios. The security staff’s goal is to use the lowest possible level of power needed to manage successfully the situation during the conflicts with adversaries. The security staff can employ a wide spectrum of possible reactions beginning with the voice alert through the physical interaction up to the usage of e.g. firearms. The optical incapacitating device is one of possible realizations of non-lethal weapons. Therefore, the article deals with the description of the designed optical incapacitating device and the evaluation of retina exposition when used.

Keywords: eye model, non-lethal weapon, retina, spot diagram.

Pages: 287–299  [References]   [Download Citation]

Improved Estimation of Air-to-Air Missile Aerodynamic Characteristics with Using CFD Method

D. Vasek, J. Polacek and P. Konecny

The paper describes a solving procedure of the special Finite Volume Method (FVM) problem dealing with calculation of a flow field around air-to-air missile at subsonic, transonic and supersonic velocity range in order to obtain a coefficient of drag (cD). Some emphasis is put on numerical solution and fundamentals of FVM and use of a k-ω turbulence model for simulation of subsonic and supersonic flow fieldsaround air-to-air missile AIM-9 Sidewinder version M. Obtained results of missile aerodynamics characteristics are verified using semi-empirical software and by analysis of flow fields.

Keywords: aerodynamic characteristics, CFD simulation, guided missile, k-ω turbulence model, trimmer mesh.

Pages: 301–315  [References]   [Download Citation]

The Causes of Leakage Deviations from sinc Function in DFT and Ways to Minimize Them

K. Hajek

The article describes a new model for the solution of the instability problem of discrete Fourier transform (DFT) spectra leakage for the incoherent real sinusoidal signal for solving the most accurate estimation of its frequency. This paper shows this phenomenon by a new form of DFT spectrum expression. It consists mainly of the spectrum of the rectangular signal in the form of the sinc function, modulated to the frequency of the tested signal in baseband. To do this, analogous spectra from other neighboring bands formed by the sampling effect are added as aliasing. The analysis shows some ways to minimize or correct it. The paper shows a simpler and substantially lesser effect of aliasing in the DFT spectrum for a complex valued sinusoidal signal.

Keywords: aliasing, DFT, frequency estimation, leakage.

Pages: 317–328  [References]   [Download Citation]

Analysis of Pilot’s Cognitive Overload Changes during the Flight

M. Galant-Gołębiewska, W. Zawada and M. Maciejewska

In this article, the research aimed at determining the impact of the intensification of actions on the pilot’s cognitive load in a simulated flight is presented. The tests were divided into two groups: pre-flight verification tests and flight tests of increasing intensity. The work was carried out at flight simulator CKAS MotionSim5. Based on the collected data, it has been proved that along with the intensification of the tasks imposed on the pilot, the level of his cognitive load also increases. Further inference leads to the conclusion that cognitive overload is one of the main reasons for pilots’ mistakes. The linear relationship between experience and cognitive load has also been proven in the studied group.

Keywords: cognitive overload, flight simulator, flight time.

Pages: 329–342  [References]   [Download Citation]

A Motion Model of a Complex-Shaped Remotely Operated Underwater Vehicle

D. Thai Nguyen, V. Horák, H. Thu Tran, L. The Nguyen and C. Quang Hoang

The knowledge of velocities of a remotely operated underwater vehicle (ROV) is crucial for the study of the ROV motion. The ROV motion equations are complemented by hydrodynamic parameters and forces acting upon the ROV. The matrices of hydrodynamic damping coefficients and external forces acting upon the ROV are considered in this study as well. The computational results obtained by the Runge-Kutta method are compared with the experiment. It appears that the presented model can be useful for the design and investigation of remotely operated underwater vehicles.

Keywords: mathematical model, motion equation, remotely operated underwater vehicle, Runge-Kutta method, water flow.

Pages: 343–353  [References]   [Download Citation]

Influence of Wave Shaper Position on Jet Formation and Penetration Depth

V. Minh Do, M. Thai Le, X. Son Bui, H. Nguyen Pham and P. Linh Nguyen

The article presents the influence of the wave shaper position on the jet formation and penetration depth of a shaped charge, which uses the liner of the PG-7VM warhead by numerical method and experimental method. The results show that, when moving the plexiglass wave shaper position towards the liner apex, the jet tip velocity and the jet velocity gradient increase. In addition, the results of the study also pointed out the existence of the wave shaper position at which the penetration depth is greatest. They indicate a match between the simulation and experimental results. The differences between simulated and experimental penetration depth are less than 15%. The results of the study are the basis for the evaluation of the influence of the wave shaper position on the liner collapse and the reasonable use of the wave shaper in the structure of the shaped charge.

Keywords: jet formation, jet velocity, penetration depth, shaped charge, wave shaper.

Pages: 355–364  [References]   [Download Citation]

The Method of Proactive Risk Assessment for Flight Safety Based on the Rate of Dangerous Events

Y. Honcharenko, O. Martyniuk, O. Radko and P. Open’ko

This publication is devoted to the issues of risk assessment in the safety management system of military aviation. The method of proactive assessment of risks to flight safety based on the number of dangerous events, which is based on correlation-regression analysis, provides an opportunity to predict the conditions that contribute to the occurrence of accidents. Studies conducted with this method have confirmed the dependence of the number of aviation accidents and serious incidents on incidents recorded for different groups of reasons, as well as on the intensity of flight activities. The obtained results can provide initial data for quantitative risk assessment in the safety management system of military aviation. The implementation of such an approach is appropriate in safety management systems in the transition phase from active to proactive approaches, until a sufficient information database on hazards is accumulated.

Keywords: correlation and regression analysis, flight safety, safety management system.

Pages: 365–377  [References]   [Download Citation]

Experimental and Numerical Modal Analysis of the Military Vehicle Hull

Z. Hryciów, A. Wiśniewski and P. Rybak

This paper presents an experimental and numerical modal analysis of the military vehicle hull. Due to its adaptation to various weapon systems, it is necessary to conduct detailed tests. Computer simulations are a very useful tool. To ensure the reliability of the results, it is necessary to validate the models. The modal analysis was used in this work. It was carried out using the roving hammer method. Both natural frequency and mode shape were compared. The Modal Assurance Criterion was used for the comparison. To determine areas of noncompliance, distributions of relative differences between experimental and finite element (FE) mode shapes were prepared. The presented results indicate a large convergence between the results of numerical and experimental analyses.

Keywords: military vehicle, modal analysis, roving hammer, vibration.

Pages: 379–391  [References]   [Download Citation]

Optimization of Non-uniform Planar Antenna Array Topology in Two-dimensional DOA Estimation

X. Luong Tran, , T. Ha Nguyen, J. Vesely, F. Dvorak V. Minh Duong and V. Sang Doan

The paper deals with the optimization of the sparse planar antenna array for direction of arrival (DOA) estimation in two dimensions (azimuth and elevation). The optimization algorithm was proposed on the basis of the peak sidelobe level (SLL) and half-power beamwidth (HPBW) parameters. In empirical validation, we have set up a measurement system to test the efficiency of an optimized array configuration. The array was configured using the patch antennas with frequency band 2.4 GHz. In comparison with several popular array configurations, the experimental results show that the proposed antenna array was optimized, and it provided higher accuracy and resolution in two-dimensional (2D) DOA estimation.

Keywords: direction of arrival estimation, optimization, sparse planar array, 2D MUSIC algorithm.

Pages: 393–403  [References]   [Download Citation]

Effect of Some Disturbance Factors on the Motion Stability of Unguided Rockets

H. Ban Le and P. Konečný

A mathematical model of unguided-rockets’ motion in the air taking into account the deflection of the thrust and the position deviation of the center of gravity has been established. The mathematical model has been solved for a specific unguided-rocket slow spin to predict its standard trajectory and deviation trajectories; calculated results agree well with the corresponding data in the firing table. The effect of the disturbance factors on the motion stability is shown through the deviation of the graph of the angle of attack; sideslip angle and the trajectory falling points compared to the corresponding values of the standard trajectory, which does not contain deviations.

Keywords: deflection of the thrust, deviation of the center of gravity, motion stability, unguided rocket.

Pages: 405–423  [References]   [Download Citation]

Reliability and Maintainability Requirements for Mobility Means of Surface-to-Air Missile Systems

P.V. Open’ko, V.V. Tyurin, M.Y. Mironyuk, P.A. Drannyk and V.V. Kobzev

The article solves the problem of complex substantiation of reliability and maintainability requirements for mobility means of surface-to-air missile (SAM) systems considering hierarchical structure of mentioned systems and appropriate characteristics of their mobility means, minimum configuration of SAM system means for air defense operation and a number of tactical characteristics of operation area. The quantitative characteristics of effectiveness of SAM system mobility means are measured by the coefficient of effectiveness sustainment which is the ratio of initial effect considering reliability and maintainability of mobility means to its value in case of faultless mobility means. The developed mathematical models, which are proposed for further use as a program product, are designed for defining the limit values of such reliability measures as mean range between failures and mean recovery time of combat and technical facilities of SAM system corresponding to given values of coefficient of effectiveness sustainment.

Keywords: maintainability requirements, mobility means, reliability requirements, surface-to-air missile system.

Pages: 425–434  [References]   [Download Citation]

Effect of Target Arrangement and Target Materials Properties on Penetration Depth

T. Sy Ngo, S. Beer and P. Konečný

The article focuses on the development of the new calculation method of jet penetration into the target using ANSYS AUTODYN simulation. The jet formation and its penetration capability dependence on properties of targets are studied. Two kinds of steel armours - Armox 440T and S235JR – in standardized plates of thickness 20 mm are used as materials of the target. The paper contains an analysis of the penetration depth in the targets containing the pure material plates set, combined material plates set and sets of Armox 440T plates with gaps 10 mm and 20 mm among individual plates. The theoretical results of simulation are compared with the results of experiments.

Keywords: ANSYS AUTODYN, Eulerian grid, jet formation, Lagrangian grid, penetration – standoff curve, PG-7V, standoff.

Pages: 435–451  [References]   [Download Citation]

Study of Unmanned Aerial Vehicle Flight Capabilities in the Aspect of Civil and Military Aviation Safety

M. Nowakowski, A. Szelmanowski, A. Pazur, E. Franczuk, D. Rykaczewski and W. Paterek

The article discusses the issues related to the adaptation of flights performed by military unmanned aerial vehicles in Poland (Unmanned Aerial Vehicle – UAV) to the civil aviation requirements. The unmanned aerial vehicles’ flight capabilities were discussed from the perspective of using the automatic flight control system to minimise a threat to civil and military aviation. Owing to the growing interest of the European Union (EU) in unmanned systems, there are many threats related to the broadly understood traffic safety in the European airspace.

Keywords: ERA, law, military aviation, UAV.

Pages: 453–463  [References]   [Download Citation]

Reduction of Corrosion Rate of Aluminium Alloy 6061 through Anodization

M.F.A. Samad and R. Ramle

This paper focuses on reducing the corrosion rate of aluminium alloy 6061 through anodizing. The study involves characterizing corrosion phenomenon that occurs on aluminium alloy 6061 in relation to parameters involved in an anodizing process, in particular the current density of anodizing, and its corrosion environment; specifically, the concentration and pH value of the corrosion accelerator. The experiment samples were anodized in sulphuric acid (H2SO4) at a current density ranging from 0.012 A/mm2 to 0.018 A/mm2. The paper also includes a qualitative analysis of corrosion images obtained from the experiment through scanning electron microscope. It concludes that corrosion rate may be reduced through an increase of current density during anodizing.

Keywords: aluminium alloy, anodizing, corrosion, electrochemical processm.

Pages: 465–475  [References]   [Download Citation]