Journal of Aeronautics and Space Technologies

Optimization of Induction Heating Coil in the Surface Hardening Process

Yalın Yamaç, Beril Özçelik — Tue, 31 Jan 2023 00:00:00 +0300

Induction surface hardening, which is used in various fields in the aerospace industry, is an important technology due to its accuracy, repeatability and energy efficiency. By modeling this heat treatment, the process parameters and efficiencies will be understood and its effective use in critical aircraft application areas will be expanded by contributing to the development of this technology. In this study, the induction surface hardening process of the cylindrical sample from AISI 4340 steel was simulated using couple field analysis. The coil geometry was optimized using two approaches to achieve homogeneous temperature distribution on the heated sample surface. One is to change the diameter of the coil rings and the other is to change the interval of the coil rings. After the diameters of the coil rings optimization, uniformity was achieved at the sample surface temperature, with deviations up to ±4°C from the austenitizing temperature. After the interval of the coil rings optimization, homogenous temperature distribution was achieved at the sample surface temperature, and deviations from the austenitizing temperature were up to ±3°C. The current value required for heating the sample surface to the austenitization temperature in 2s has been reduced, and energy savings have been achieved.

The Generalized Tensor Model for Numerical Investigation of Combustion and Flow Processes in Liquid Rocket Engine Chamber

Nijat Abdulla, Parviz Shahmurad Abdullayev — Tue, 31 Jan 2023 00:00:00 +0300

Combustion and flow thermogasdynamics is one of the most sophisticated computational stages in liquid rocket engine (LRE) design. A considerable amount of different methodologies used to conduct the thermogasdynamic analysis of the combustion and flow process and obtain the accurate estimates of the parameters of the LRE chamber is known, currently, in rocket and space sciences. However, the development of a generalized mathematical model that would have a capability of being applied for any unique combustion case by, hence, yielding reliable results and, nevertheless, be efficient in any application still remains to be an issue. The following paper considers the development of a generalized tensor model the application of which for any desired propellant configuration yields unique results. In addition considered the application of the mentioned model at significant nozzle sections. Moreover the current paper, also, considers an approach based on the specific area in order to compute the parameters at the nozzle throat. The uniqness of this approach is based on the fact, that the outcoming results appear to be more accurate than the ones obtained using convential approaches. The paper accurately summarizes the application of the generalized tensor model based on an example problem which involves the combustion of liquid methane with liquid oxygen.

Performance of Multi-Service Telecommunication Systems Using the Architectural Concept of Future Networks

Bayram Ganimatoglu Ibrahimov, Yalchin Sabiroglu Isayev, Mustafa Emre Aydemir — Tue, 31 Jan 2023 00:00:00 +0300

In this study, the performance indicators of multiservice telecommunication systems (MTS) based on Future FN networks (FN, Future Networks) using SDN (Software-Defined Networking) technologies are analyzed. Based on the study of MTS using the architectural concepts of Future networks, a mathematical model of software-defined networks is proposed (SDN). Analytical expressions have been obtained that make it possible to evaluate the indicators of service quality, information security and fault tolerance of the system in the provision of multimedia services.

Equivalence Ratio Effect on Helium Diluted Methane Jet Flame Temperature and Pollutant Emission for a Swirl Assisted Gas Turbine Burner

Buğrahan Alabaş, Adem Altınay — Tue, 31 Jan 2023 00:00:00 +0300

Temperature distribution and post-combustion emissions in gas turbine combustion chambers have attracted the attention of researchers in recent years. In this study, the combustion chamber temperature distribution and flue gas emission values at different equivalence ratios were determined by diluting the methane flame with Helium at the rate of 20% by volume. A high swirl number (1.6) swirl generator was placed at the burner outlet and the combustor power was kept constant at 3 kW. In this way, the equivalence effect in a swirled combustion was investigated. The following results emerged in the study, in which 0.7, 0.8, 0.9, 1.0, 1.1 values were tested as the equivalence ratio. With the increase in the equivalence ratio, the flame temperature and brightness at the burner outlet increased, especially up to 0.9 equivalence ratio. After this critical value, there was a tendency to decrease in temperature and luminous intensity again. As the distance from the burner axially in the combustion chamber increased, the average temperatures increased with the increase in the equivalence ratio. On the other hand, as the CO value in flue gas emissions was increased from 0.7 to 1.0 equivalence ratio, it decreased by half.

Leading-Edge Vortex Characteristics of Surging-Translating Flexible Wings

Mahdi Yazdanpanah, Mustafa Perçin — Tue, 31 Jan 2023 00:00:00 +0300

This study experimentally investigates the flow fields and properties of the leading-edge vortex (LEV) around rigid and chordwise-flexible wings performing rectilinear translational motion starting from rest. A rigid wing and two flexible wings with an intermediate degree of flexibility and a high degree of flexibility are considered in this study in order to explore the influence of wing deformation on the behaviour of the LEV. Phase-locked planar particle image velocimetry measurements are performed at the 75% span position of the wings at the Reynolds number of 7360. The results reveal the presence of similar flow structures for all wings in the acceleration phase: a coherent LEV and a series of vortices shedding from the trailing edge of the wing (i.e., trailing edge vortices). At the late stages of the constant-speed phase, the LEV moves away from the wing surface and bursts into smaller flow structures in the case of the rigid wing and the wing with an intermediate degree of flexibility. In the case of the wing with a high degree of flexibility, a coherent LEV which is positioned close to the wing surface is present throughout the motion. In this case, a smaller geometric angle of attack is attained due to a larger chordwise deformation of the wing. Accordingly, the flow reattaches downstream of the LEV and leaves the trailing edge smoothly. A stable LEV and the associated low-pressure region, and the increased size of the horizontal surface area may elevate the resultant lift force despite the fact that the relatively small LEV circulation level is achieved in the wing with a high degree of flexibility.

Outage Probability Analysis of UAV-Assisted Wireless Communication System with Reconfigurable Intelligent Surfaces Over Weibull Fading Channels

Emre Hanbay, Gökhan Altın — Tue, 31 Jan 2023 00:00:00 +0300

Offering a low-cost but practical solution for next-generation communication technologies, reconfigurable intelligent surfaces (RIS) aim to direct the incoming signal with adjustable phase shift using too many low-cost passive elements. In this paper, we analyze the outage probability performance in RIS-assisted unmanned aerial vehicle (UAV) communication networks based on the reflective role of the UAV equipped with RIS between command-and-control center on the ground and another aerial vehicle to improve coverage area. Inspired by the promising potential of RIS-assisted UAV communication system, we investigate the scenario in which the UAV equipped with RIS acts as a reflective relay in order to prevent obstacles between the ground-based command and control system and another aerial vehicle and to ensure uninterrupted communication. Channel modeling of the RIS supported UAV communication network is designed with double Weibull fading and the outage probability of proposed system is analyzed by presenting closed form expressions to enhance total system performance of the communication framework supported by the UAV. Performance of the communication network according to the position parameters of the UAV and the number of RIS reflective surface elements is investigated using Monte-Carlo simulations. Furthermore, the presented scheme is compared with traditional cooperative communication systems (amplify-and-forward, decode-and-forward). The obtained results showed that coverage of the proposed RIS-UAV supported architecture is improved efficiently and the RIS-UAV scheme is a rewarding candidate for the future communication networks.