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Öğe CFD Analysis Of Jet Flows Ejected From Different Nozzles(Oxford University Press [University Publisher], 2021) Kosa, Ergin; Ezgi, Cüneyt; Berkay, Çetin; Atmaca, MustafaNozzles are widely used to control the rate of flow, speed, direction, mass, shape and pressure of the stream in connection with many different engineering applications. This paper presents the performance predicted by a computational fluid dynamic (CFD) model, which are 3D models that utilize parametric analysis, realizable k-epsilon turbulence models and experimental measurement for a jet. Jet flows are ejected from three different slot nozzles: round-shaped nozzle, rectangular-shaped nozzle and 2D-contoured nozzle. In this numerical study, velocities of free jets have been predicted for different axial distances from the nozzle exit in the range of 0.2?z/B?12 when center velocity at the nozzle exit. CFD simulation results are compared to experimental results from literature. These results are consistent with the existing experiments.Öğe Determination of the Effective Fused Deposition Modeling Process Parameters on the Mechanical Properties of Carbon Fiber-Reinforced Polypropylene Parts(Amer Soc Testing Materials, 2024) Eryildiz, Meltem; Kosa, Ergin; Yavuzer, Bekir; Akgun, Ismail CemAdditive manufacturing is gaining popularity for producing components in industries such as automotive, aerospace, and medicine due to its potential to minimize material waste. Because the strength of the 3-D-printed part is so important, it's crucial to do research and optimize process parameters to make the printed parts as strong as possible. This work focuses on the experimental investigation and discussion of the tensile and impact strength of parts made from carbon fiber-reinforced polypropylene (PP-CF) using the fused deposition modeling (FDM) technique. Various process parameters, including infill pattern, infill density, layer thickness, and build orientation, are examined on three different levels to determine their influence on the tensile and impact strength of the printed part. The outcomes of the analysis of variance (ANOVA) analysis reveal that infill density primarily affects impact strength, whereas layer thickness significantly influences tensile strength. The optimal combination of parameters leading to the maximum tensile and impact strength consists of a grid infill pattern, 60 % infill density, 0.36-mm layer thickness, and a 45 degrees build orientation. Furthermore, fracture surface analysis is consistent with mechanical test results.Öğe Dynamic And Steady-State Analysis Of Steam Reforming Of Methane To Hydrogen İn A Reformer For Electric-Powered Unmanned Aerial Vehicle(Oxford University Press [University Publisher], 2021) Kosa, ErginHydrogen-fueled combustion systems are becoming popular in recent years. Methane is one of the significant hydrogen supplier in nature. Thus, in the study, the natural gas-fueled reactor-assisted solid oxide fuel-cell system is configured to provide a current to load the battery to turn the propeller of an unmanned aerial vehicle in the large-scale hydrogen-onboard system. The methane-fueled reactor has not been studied under a large-scale case in literature yet. To investigate the amount of products, this paper presents about the steam-reforming performance of natural gas in steady state and transient in the reactor. The influence of vital parameters such as steam/carbon, gas feed temperatures, the amount of heat transferred to the reactor in methane steam reforming for a plug flow reactor, and a continuous stirred tank-type reactor is investigated respectively. Methane conversion, yield of hydrogen gas and H2 gas generation for different medium conditions along the reactor are studied on by using the COMSOL Multiphysics program. The steady-state and time-dependent characteristics of the steam reforming of natural gas are focused on. The high conversion ratio of methane gas is obtained by ranking the steam/carbon ratio. The released hydrogen gas molar flow rate is increasing according to the reactor volume. The achieved power provided by produced gas of H2 is 97 hp supplying the thrust force for an unmanned aerial vehicle. © 2020 The Author(s) 2020. Published by Oxford University Press.Öğe An experimental comparison of the effects of jet fuel (F-34) and diesel (F-54) on the wear of fuel system components and fuel consumption of an internal combustion diesel engine(Canadian Science Publishing, 2022) Durmusoglu, Senol; Kosa, ErginThe logistics of maintaining a fuel supply is a significant consideration for the military. Members of the North American Treaty Organization (NATO) prefer to use a single fuel to avoid problems with fuel transport and storage. Thus, we chose the kerosene-based F-34 jet fuel as the single fuel for testing on a land-based vehicle. We examined the feasibility of using F-34 jet fuel in a diesel engine and compared the performance of the jet fuel with a conventional F-54 diesel fuel. We compared the power and torque characteristics of an M52 diesel engine, as well as fuel consumption as a function of engine speed and torque using F-34 jet fuel and F-54 diesel fuel. Moreover, wear of the fuel pumps in Magirus Unimog and MAN trucks was measured during long-term tests operating with F-34 and F-54 fuels, respectively. We found that there was no obvious difference in engine power and torque using F-34 or F-54 fuel.Öğe An experimental investigation of formability of inconel sheet plate for different die angles and rolling directions in press brake bending(2023) Kosa, Ergin; Hayrat, Koray; Durmusoglu, SenolThe formability of Inconel materials is important to be used in engineering applications such as in fields of aircraft and maritime. The aim of study is to investigate bending characteristic and formability of Inconel 625 material having a property of corrosion resistance and high strength. In the paper, spring-back phenomena of Inconel 625 sheets are focused on experimentally. The 4 specimens for each different die angle are prepared to be bent. The press brake is used for forming Inconel 625 sheets. The die angle is altered from 90? to 150?. The different rolling direction such as 0? and 90? is chosen to investigate the effect of grain orientation on spring-back of Inconel sheets. The bending radius is constant and set as 2 mm for all bending tests. The spring-back angles and amounts are measured. Results show that as the bending angle is increased, the spring-back amount in units of angle is decreased averagely from 3.35? to 2.58? for 0? rolling direction and maximum spring-back angle is obtained at a die angle of 120? for rolling direction of 90?. Finally, Erichsen cupping test is also applied to determine the deformability of Inconel sheets. It is demonstrated that cup height value has been found as 17.20 mm.Öğe Hibrid Motorlu “Tuzla Jeep Willys Markalı” Aracın Tasarımı Ve Karakteristiği(Beykent Üniversitesi, 2019) Simav, Osman; Büyükkarcı, Buket; Kosa, ErginOtomobiller hiç kuşkusuz günümüzün en önemli araçları arasındadır. Birbirinden farklı teknolojiye sahip pek çok çeşidiyle hayatımızda yer almaktadırlar. Özellikle son dönemlerde sıkça gündeme gelen fosil akıtların rezervlerinin ilerleyen yıllarda tükenmekle karşı karşıya olması ve bunun dışında fosil yakıtlar nedeniyle doğaya verilen zararın en aza düşürülmesi için alternatif yakıtlar ve bunların uygulanabileceği teknolojiye sahip otomobillerin üretimi konusunda çalışmalar yapılmaktadır. Bunlar arasında günümüzde oldukça yaygınlaşan elektrikli ve hibrid araçlar dikkat çekmektedir. Bu çalışmada Türkiye’nin ilk motorlu aracı olarak 1955 yılında İstanbul Tuzla’da özel sektör yatırımı olarak kurulan ve 1970’de Kara Kuvvetleri Komutanlığı’na devredilen Jeep Willys aracı ele alınmıştır. Bu araç kullanıldığı dönemlerde büyük ilgi görmüş ve yolu olmayan köylerde ulaştırmada, traktör olarak tarımda ve çekici olarak yollarda gerçek çok amaçlı kullanım imkânı sunmuştur. 2006’da imalatına son verilen bu araçtan trafkte dolaşan binlerce adedinin bulunduğu bilinmektedir. Bu aracın hibrid elektrikli bir modelinin tasarımının sonuçları bu çalışmada işlenmiştir.Öğe A mathematical model for erosive abrasive wear analysis by using abrasive size and material hardness(Emerald Group Publishing Ltd, 2023) Kosa, Ergin; Goksenli, AliPurpose - Erosion and abrasion are the prominent wear mechanisms reducing the lifetime of machine components. Both wear mechanisms are playing a role meanwhile, generating a synergy, leading to a material removal on the target. The purpose of study is to create a mathematical expression for erosive abrasive wear.Design/methodology/approach - -Many factors such as environmental cases and material character have an influence in erosive abrasive wear. In the work, changes in abrasive size and material hardness have been analyzed. As an abrasive particle, quartz sand has been used. All tests have been done in 20 wt.% slurry. Heat treatment has been applied to different steel specimens (steel grades C15, St 37 and Ck45) to change hardness value, which ranged from 185 to 880 Vickers hardness number.Findings - After the four-hour test, it is determined that by an increase in abrasive size and decrease in material hardness, wear rate increases. Worn surfaces of the targets have been examined to figure out the wear mechanisms at different conditions under scanning electron microscopy. The results indicate that by an increase in material hardness, the number and diameter of micro-craters on the worn surfaces decrease. The diameters of micro-craters have been about 3-8 mu m in hard materials and about 120-140 mu m in soft materials.Research limitations/implications - It is determined that by an increase in abrasive size and decrease in material hardness, wear rate increases. The results indicate that by an increase in material hardness, the number and diameter of micro-craters on the worn surfaces decrease.Practical implications - The study enables to indicate the dominant factor in worn steel used in mechanical components.Originality/value - After analyzing the test results, a novel mathematical expression, considering both abrasive size and material hardness, has been developed.Öğe Modeling Study and Performance Investigation of a Thermoelectric Refrigerator(2021) Kosa, Ergin; Kepekçi, Haydar; Ezgi, CüneytThermoelectric refrigerators are widely used in electronics, medical, and food industry application areas. A refrigeration effect can also be achieved without using any moving parts by merely passing a small current through a closed circuit made up of two dissimilar materials. This effect is called the Peltier effect, and a refrigerator that works on this principle is called a thermoelectric refrigerator. They consist of several thermoelectric legs sandwiched between two thermally conductive plates, one cold and one hot. Thermoelectric refrigerators presently cannot compete with the vapor-compression refrigeration system because of their low- coefficient of performance (COP). However, some applications have been preferred because of their small size, simplicity, quietness, and reliability. In this study, a thermoelectric cooler having a maximum cooling power of 50 W, having a dimension of 40mmx40mmx3.6 mm, is modeled in multi-physics software. Also, the performance of a thermoelectric refrigerator is investigated. It is computed the temperature difference between ceramics plates versus electric current and COP for a temperature difference between ceramics plates. The simulation results are compared with experimental data. The data obtained from the analyses have been compared with the experimental results and found to agree with each other. For the surface temperatures of 25 oC and 50 oC, the maximum coefficients of performance have been computed to be 1.091 and 1.445, respectively. In general, as the temperature of hot surfaces has increased for the same temperature differences, the COP of the thermoelectric cooler has increased.Öğe Numerical Modeling of Hydrogen-Rich Gas Production From Gasoline Autothermal Reforming in a Plug Flow Reactor for Electric Vehicles(Asme, 2021) Kosa, Ergin; Ezgi, CuneytDue to the increase in the greenhouse effect, lowering emissions is becoming a certain issue all over the world. It is a concern to develop alternative options to minimize the spread of exhaust gases. For this purpose, in this study, the plug flow reactor in the system consisting of solid oxide fuel cell, reactor, electric motor, battery, burner, and the heat exchanger is considered. Numerical modeling of hydrogen gas generation in a plug flow reactor is studied. The reactor indicated on-board hydrogen gas generation for an electric motor automobile has not been modeled in the literature yet. Autothermal reforming of isooctane is simulated in the comsol multiphysics software program in the reactor particularly. Conversion of isooctane and H2O is examined at different overall heat transfer coefficients, input temperatures, and steam/carbon ratios. Also, there are certain differences between adiabatic and non-adiabatic conditions. The produced synthesis gas of hydrogen drastically increases in the non-adiabatic case. The obtained results from the model are compared with experimental data obtained from the literature. H-2 production at the end of the autothermal reforming process indicates that the power provided from the reactor can operate a motor of an automobile. In this study, the achieved power is 65.8 kW (88 HP) and is sufficient for an automobile. Simulation results show that the reactor volume of 75 L supplies 0.18 mol(-1) of H-2 and 0.08 mol(-1) of CO in the non-adiabatic case.Öğe Three-Dimensional Cfd Modeling Of Thermal Behavior Of A Disc Brake And Pad For An Automobile(Oxford University Press, 2020) Kosa, Ergin; Kepekci, Haydar; Ezgi, Cüneyt; Cihan, AhmetThe brake system of an automobile is composed of disc brake and pad which are co-working components in braking and accelerating. In the braking period, due to friction between the surface of the disc and pad, the thermal heat is generated. It should be avoided to reach elevated temperatures in disc and pad. It is focused on different disc materials that are gray cast iron and carbon ceramics, whereas pad is made up of a composite material. In this study, the CFD model of the brake system is analyzed to get a realistic approach in the amount of transferred heat. The amount of produced heat can be affected by some parameters such as velocity and friction coefficient. The results show that surface temperature for carbon-ceramic disc material can change between 290 and 650 K according to the friction coefficient and velocity in transient mode. Also, if the disc material gray cast iron is selected, it can change between 295 and 500 K. It is claimed that the amount of dissipated heat depends on the different heat transfer coefficient of gray cast iron and carbon ceramics.
