Defence Science Journal
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Analysis the Unpowered Freewheeling Propeller Impact in Quadcopter for Energy Harvesting Process
Get PDFThis research investigates the impact of freewheeling propellers in the Quadcopter for the purpose of harvesting energy. The main part of the Quadcopter is the propeller. In the arm of the Quadcopter, if the Unpowered freewheeling propeller is connected along with the main propeller at the time of Energy Harvesting (EH) process, the induced-flow caused by both propellers may interfere with the Quadcopter’s aerodynamics. Consideration of the aerodynamic point of view to place the freewheeling propeller at a particular distance and place from the main propeller is very important. In this study, in terms of propeller diameter, two different types of freewheeling propeller designs are taken to investigation: Case 1- same size propellers and Case 2- different size propellers. Three distances between the main and freewheeling propellers are defined using the primary test setup as 8, 10, and 12 cm are taken to the software analyses using Computational Fluid Dynamics (CFD) ANSYS 18.1 / FLUENT simulation. The propeller airflow characteristics of pressure, force, and velocity variation between both cases are analysed using the graphical contour representation and measured values. The CFD simulation result showed that, Case 2-different size propellers got better force variation compared with the Case1-Same size propellers and 10 cm distance between the propellers in both the Cases seems good results compared with the other distances of 8 cm and 12 cm. This is an interesting design feature that can be used to locate the freewheeling propeller in the Quadcopter for Energy Harvesting purpose
Wideband Antennas of Passive Seekers for Anti Radiation Missiles
Get PDFSuppression of Enemy Air Defence (SEAD) is a fundamental element of Air Power application by means of in protecting friendly air attackers and destroying the enemy’s ability to defend against air attack. Most of the SEAD operation even today relies on Anti-radiation missile (ARM) which is an air-to-surface tactical missile designed to detect, seek, attack and destroy opponent’s radar. Passive seeker of ARM is a miniaturized ESM receiver which is capable of extracting the necessary angular data from the enemy radar emissions. Single head passive seeker covering wide frequency range from L to Ku band is the preferred choice. Wideband antennas have been designed and utilized for Direction Finding applications of ESM/ELINT receivers for ground, air and ship borne platforms. Unlike these platforms, there are several restrictions for passive seeker based compact ESM receiver for missile borne platform specially air to surface missile where lesser diameter is one of the preferred design parameter. This review paper mainly discusses the existing wideband antennas such as spiral, log-periodic, printed circuit vivaldi and all-metal vivaldi antennas and the comparison of their various parameters for passive seeker. The paper also suggests their suitability with respect to their placement on the missile for three configurations: concealed inside the radome, flush-mounted and conformal antenna based. The paper also brought about the specific test facility required for testing and evaluation of passive seeker to characterize it with missile radome which is the most challenging and time consuming task. Among the three passive seeker configuration discussed, conformal antenna based passive seeker using all-metal Vivaldi is the best option avoiding radome aberration correction which is being utilized in the present third generations of ARM. The second commonly and established passive seeker configuration is concealed inside the radome using spiral antennas where handling radome aberration correction is a limitation. 
Effect of Localised Pressure Depression and Rain on Aerodynamic Characteristics of MALE UAV
Get PDFThis paper presents the effect of the local low-pressure region in the atmosphere and rain on aerodynamiccharacteristics of medium altitude long endurance unmanned aerial vehicle (MALE-UAV) configuration duringcruise/loiter. Computations are performed using CFD++, a commercial CFD software suite. A large low-pressuredepression past the MALE UAV (symmetrically and asymmetrically) with pressure 10 – 15 % lower than the freestream pressure and a widespread rainfall type with a rainfall rate of 1195 mm/hr., are considered for CFD simulation.A large low pressure that spans the whole MALE-UAV results in a decrement in both lift and drag, but does not affect the yawing and rolling moments significantly. However, a low-pressure region that engulfs only one-half of MALE UAV causes sudden/abrupt changes in rolling and yawing moments. The effect of rain causes a significant decrease in a lift at higher alpha, accompanied by a decrease in stall angle of 2 degrees, and a significant increase in drag. From the study, a Standard Operating Procedure (SOP) was adopted to fly UAVs in adverse weather effects,such that the aircraft can be operated with a velocity higher than 1.3Vstall and at a power setting not less than 75% of max power capacity
Experimental Investigation and Thermophysics Analysis of Joule Thomson Cooler Applicable to Infrared Imaging
Get PDFRecuperative type of heat exchanger (H-E) based miniature Joule-Thomson (J-T) cooler operated in the steady-state condition is employed extensively in applications towards infrared detectors cooling, thermal imaging cameras, and homing guidance devices in a wide variety of defence projectile systems. In this study, a theoretical thermal design of recuperative H-E for determining a viable geometry using iterative methodology is discussed. A steady-state numerical analysis for the developed geometrical model of the H-E is also reported, along with the experimental studies for typical operating conditions. A custom numerical code using the Runge-Kutta method has been developed in MATLAB, and the results from the code compared with predictions of COMSOL multi-physics are in good agreement. Further, results have been validated proving the efficacy of the theoretical model and custom numerical code developed
Studies of Jet A1 Fuel Atomization Through Non Circular Orifices
Get PDFThe performance of the liquid rocket engine depends on the atomization behavior of the fluid being injected into the combustion chamber. Generally, a plain injector with a circular orifice has been used in the injector, but it has the disadvantage of having a low spray cone angle. The breakup length, mean droplet diameter, and Sauter mean diameter is also higher. Thus, to overcome these drawbacks, non-circular orifices have been utilized in the present study. The shapes used for non-circular orifices are semi-circular and plus. The results obtained with the non-circular orifice is compared with the circular orifices of the same area ratio. The working fluid used for the studies is Jet A1 fuel. Studies were also conducted with different L/D ratios by choosing an effective orifice length to reduce the upstream losses. The axis-switching phenomena were observed with the semi-circular as well as with the plus jets. The mean droplet size of the circular jets was more prominent compared to non-circular jets, and the Sauter mean diameter of non-circular jets droplets was smaller than that of the circular jet droplet. The spray cone angle has increased by 290% for plus jets and 30% for semi-circular jets compared to circular jets
Effect of Aging on the Ballistic Performance of AA 7017 Alloy
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This study presents the effect of aging on microstructure, texture, mechanical and ballistic properties of AA-7017 aluminium alloy. AA-7017 alloy is subjected to three different aging namely under-aging, peak-aging and over-aging. Significant difference is observed in the mechanical properties after aging. The alloy exhibits maximum strength and hardness in the peak-aged condition. From texture measurements, it is noticed that the overall intensity of orientation distribution function increases from under-aged to peak-aged condition. The AA-7017 aged plates are impacted with 7.62 mm steel core projectiles at 820±10 m/s to evaluate the ballistic performance. It is noticed that AA-7017 alloy displays best ballistic resistance in peak-aged condition. Distorted material flow lines and adiabatic shear band induced cracking is detected in post ballistic microstructure. The ballistic performance of AA-7017 alloy is correlated with the variations in the microstructure and mechanical properties with aging
 
Digital Twin Framework for Lathe Tool Condition Monitoring in Machining of Aluminium 5052
Get PDFDigital Twin (DT) is a virtual representation of a product system that exhibits the properties and analyzes the system’s functions. The significant impact of DT extends to several fields, which increases productivity and reduces wastage. This article focuses on developing a Digital twin model of a Lathe machine for Tool Condition Monitoring (TCM). DT implementation in industries is challenging due to simulating online cutting forces and wear. Even though several pieces of research have been carried out in the prediction of tool conditions using machine learning, Artificial Neural network models, only a few pieces of research have been made in digital twins for TCM. This article provides the technique for implementing the DT model of a lathe tool. The feasibility of the DT Model framework is verified by a case study of the turning process with a CNC Lathe machine while machining of Aluminium 5052 workpiece using Titanium Nitride coated tool inserts. The sensor’s data are acquired and fed to the microcontroller for real-time data acquisition. The real-time dataset is processed in the DT model for monitoring and predicting the tool conditions. The tool wear classification using the DT model is achieved. Developing the Digital Twin model in machining increases productivity and assists in predictive maintenance
Construction of New Hadamard Matrix Forms to Generate 4X4 and 8X8 Involutory MDS Matrices over GF (2m) for Lightweight Cryptography
Get PDFIn this paper, we present the construction of two Hadamard matrix forms over GF(2m) to generate 4×4 and 8×8 involutory MDS (IMDS) matrices. The first form provides a straightforward way to generate 4×4 IMDS matrices, while the second is an efficient way to generate 8×8 IMDS matrices using a hybrid (combination of search-based methods and direct construction) approach. In addition, we propose an algorithm for computing the branch number of any non-singular matrix over GF(2m) and improve its computational complexity for Hadamard matrices. Using this algorithm and the proposed Hadamard matrix form, we obtain 2k ×2k lightweight involutory and non-involutory Hadamard MDS matrices with low XOR counts for k=2,3. Finally, we carry out a comparative study based on the XOR count to demonstrate that MDS matrices created using our Hadamard matrix forms have lower XOR counts than MDS matrices available in the literature as of today
Investigation of the Effect of Various Types and Features of Grooved Barrels on the Range of Firearms
Get PDFThe research has focused on the innovations which can be performed in order to increase the range of cannons and howitzers. The most important parameter affecting the range of a weapon system is the velocity distribution in the barrel and finally the initial muzzle velocity. On the other hand, the most important parameters affecting the initial muzzle velocity of the bullet are the internal barrel pressure, internal barrel friction, mass of the bullet and weight of the bullet. Taking these parameters into consideration, it has been revealed that improvements could be made by designing and manufacturing new types of barrels, ammunition and certain parts. The advantages and disadvantages experienced after such changes have been determined and studied theoretically and experimentally
Investigation of the Mechanical Properties of the Barrel After Geometric Changes on the Mortar
No full textThe area close to the firing part as of the muzzle of a 120 mm mortar consists of trapezoidal threads. In order for the 120 mm mortar to hit the target, the target is aimed by giving the required angle with the help of these trapezoidal screw threads. Since it takes a lot of time to set the target in this way, the aim is to develop a hydraulic mechanism that automatically gives an angle to the system by lifting the trapezoidal screw threads instead of mechanically setting the angle to be adjusted easily in the shortest time. Thus, it is intended to convert the mortar into a full-automatic system that can rotate 360° around itself and can be adjusted to the desired angle in a short time and very precisely. The present study is conducted in two steps. At first, thermo-mechanical analyzes for the stresses affecting during firing of the currently used 120 mm mortar with a screw thread were investigated by ANSYS Workbench finite elements method. Then, the status of the mortar after removing the screw threads was examined in the ANSYS Workbench program under the effect of the same stresses and the results were compared between the two mortars and it was examined whether it is safe to remove the screw threads