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Öğe Bor katkılı yakıtların yanma karakteristiklerinin farklı yakma sistemlerinde incelenmesi(2022) Değirmenci, HüseyinBu yüksek lisans tez çalışmasında ülkemizin enerji bağımsızlığı konusunda statejik öneme sahip bir bor türevi araştırılmıştır. Deneysel çalışmalarda bor katkılı yakıtların yanma davranışları ve yanma sonunda oluşan emisyonlar farklı yakma yöntemleriyle incelenmiştir. Tez kapsamında incelenen yakıtlar bir bor türevi olan TMB (trimetil borat) ile benzin yakıtı ve bunların karışımlarıdır. Saf ve karışımlı yakıtlar sırasıyla; damlacık testi, Bunsen yakıcı testi, enjektör yardımıyla difüzyon alev testi ve kanal akışı ile yanma hızı testlerinde incelenmiştir. Yakıt karışımları benzin ve TMB’nin kütlece karışımları ile ultrasonik karıştırma sonrasında elde edilmiştir. Damlacık testleri sonucunda; %0TMB’nin alev boyu uzun olacak şekilde sarı kırmızı beyaz ışıma gösterdiği, %100TMB’nin daha kısa alev boyunda yeşil ışıma davranışı sergilediği tespit edilmiştir. Bütün karışımlı yakıtlarda önce TMB’nin kendi yanma davranışını sergileyerek yandığı daha sonra ise benzinin benzer şekilde yandığı gözlenmiştir. %100TMB’nin çok kısa sürede yandığı görülürken, karışımlı yakıtlarında ise TMB konsantrasyonunun %80’nin altına düştükten sonra yanma sürelerinin arttığı tespit edilmiştir. Saf benzin içerisine az miktarda TMB ilavesinin bile tutuşma gecikmesinin ciddi oranda azalttığı görülmüştür. Damlacık boyutunda ki maksimum sıcaklıklar TMB miktarı ile doğru orantılı biçimde artış gösterdiği ölçülmüştür. Bunsen yakıcılarda alınan sonuçlarda TMB oranı artıkça yeşil ışıma yoğunluğunun, alev salınımlarının ve alev kopmalarının artığı gözlenmiştir. TMB yoğunluğunun artmasıyla alev boyunun uzadığı ve karışımın zengin karışım olmasından dolayı laminer alev hızının düştüğü tespit edilmiştir. Bunsen yakıcıda gerçekleştirilen ön karışımlı testlerde TMB ilavesinin CO (karbonmonoksit) emisyonunu azaltığı ölçülmüştür. Kanal akışı ile yanma hızı ölçümlerinde de TMB’nin benzinden daha yavaş bir hızla ile yandığı belirlenmiştir. Enjeksiyon ile yapılan difüzyon alevi deneylerinde yakıta TMB katkısının enjektör açısına bağlı kalarak yanma davranışı sağladığı tespit edilmiştir. Ayrıca Bunsen yakıcılarda ve enjeksiyon yöntemiyle yapılan deneyler sonucunda maksimum sıcaklıkların %5TMB ve %10TMB karışımlı yakıtlarda olduğu gözlenmiştir. Yapılan deneyler sonucunda alternatif yakıt arayışında TMB'nin ana yakıt ve/veya katkılı yakıt için iyi bir hidrokarbon olduğu görülmüştür.Öğe Combustion Behavior of Fuel Droplets with Metallic, Non-Metallic and Organo-Metallic Boron Additives(Taylor and Francis Ltd., 2024) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Yontar, Ahmet Alper; Ocakoğlu, KasımThere is considerable interest in the utilization of fuels derived from boron materials, with their high calorific value, in various applications ranging from propellants to pyrotechnics. Conversely, their impact on the combustion behavior of conventional hydrocarbon fuels remains largely unclear. In this study, ignition, combustion, micro-explosion and simultaneous atomization behaviors of gasoline-based alternative fuels containing metallic (28–35 µm MgB2), nonmetallic (1 µm amorphous boron, 10 µm AlB12 with 86–88% and 95–97% purity) and organo-metallic boron derivatives (triethyl borate (TEB) containing C2H5 groups and trimethyl borate (TMB) containing CH3 groups) were investigated. The experiments were carried out at droplet scale and recorded using a high-speed camera and a thermal camera. The findings revealed a systematic reduction in ignition delay for each gasoline fuel enriched with boron derivatives. 2.5%AlB12/G and pure TMB droplets were the fastest extincting fuel droplets (0.9678 s and 1.245 s, respectively). The highest maximum flame temperature was recorded as 626 K and 610 K for pure TMB and 80%TEB/G, respectively. Droplet diameter regression analyses showed that the diameters of fuel droplets containing predominantly metallic and nonmetallic boron derivatives decreased in accordance with the d2-law. This study demonstrated that cost-effective and easily producible amorphous boron and organometallic boron derivatives are promising energy carriers for hydrocarbon fuels.Öğe Combustion Characteristics of r-GO/g-C3N4/LaFeO3 Nanohybrids Loaded Fuel Droplets(Taylor and Francis Ltd., 2023) Küçükosman, Rıdvan; Değirmenci, Hüseyin; Sert, Buse; Yontar, Ahmet Alper; Harputlu, Ersan; Ocakoğlu, KasımGraphene oxide (GO), reduced graphene oxide (r-GO) and graphitic carbon nitride (g-C3N4) are two-dimensional carbon-based nanosheets that show promise in reducing emissions with their superior catalytic activity in capturing species such as NOx and CO2 thanks to their oxygen- based functional groups and active edges on their surfaces. These active surfaces also provide a scheme for the substitution of materials with high calorific value or high catalytic activity for combustion. This study focuses on the fabrication of functional nanohybrid structures customized for combustion with LaFeO3 metal oxide nanoparticles substituted on these nanosheets and their effect on the combustion behavior of gaso-line. The fabrication of r-GO/g-C3N4/LaFeO3 nanohybrid structures was carried out by a two-step hydrothermal method. The structural character-izations of the samples were confirmed by SEM and XRD analyses and their chemical states were confirmed by Raman and XPS techniques. Combustion experiments were carried out by droplet scale combustion of gasoline-based nanofuel droplets containing dilute (0.2 wt.%) and high (0.7 wt.%) concentrations of GO, r-GO, g-C3N4, g-C3N4/LaFeO3 and r-GO/g- C3N4/LaFeO3 nanoparticles. The experimental process was recorded with a high-speed camera and a thermal camera. The nanofuel droplets con-taining 0.2 wt.% g-C3N4/LaFeO3 nanohybrid structures had the highest maximum flame temperature of 519 K, and the nanofuel droplets con-taining 0.7 wt.% r-GO/g-C3N4/LaFeO3 particles had the highest maximum aggregate temperature of 1177 K. The ignition delay time decreased for all droplets with 0.2 wt.% and 0.7 wt.% particle loadings. At 0.2 wt.% concentration, g-C3N4 doped fuel droplets exhibited the lowest extinction time, while at 0.7 wt.% concentration, the lowest extinction time was measured for r-GO/g-C3N4/LaFeO3 doped fuel droplets. Fuel droplets containing g-C3N4 particles had the highest burning rate and were the fastest extinguishing fuel droplets in the electric field. In this study, it has been demonstrated that the combustion rate and energy value of hydro-carbon fuels can be increased and soot formation can be reduced at the same time with the new generation of graphene-based functional mate-rials to be created, and thus, many combustion problems can be solved simultaneously with these functional particles.Öğe Investigation of combustion characteristics on triethyl borate, trimethyl borate, diesel, and gasoline droplets(Pergamon Elsevier Science Ltd., 2023) Değirmenci, Hüseyin; Yontar, Ahmet Alper; Sofuoğlu, Duygu; Değirmenci, Hüseyin; Ayaz, Tahir; Üstün, DenizIn this study, the evolution of fuel droplet diameter, flame structure, and maximum flame temperature over time was observed using a high-speed camera and a thermal camera at the same time. Traditional fuels (diesel and gasoline) and new generation fuels (triethyl borate and trimethyl borate) fuels were investigated within the droplet experiments. It has been shown that the flame structure of diesel and gasoline fuel droplets has a large non-luminous region that is seen during the combustion process, unlike triethyl borate and trimethyl borate fuels. The curves of the time-dependent variation of the dimensionless square of the droplet diameter (D/D0) 2 of the fuel droplets considered in the study generally exhibited curve properties conforming to the D2-law. In the flame formed by the trimethyl borate droplet, the highest flame temperature was observed by the thermal camera, while the shortest burning time was detected. According to the experimental conditions in the study, the shortest ignition delay was measured for trimethyl borate, while the longest ignition delay time was observed for diesel fuel droplet. Also, it was determined that the lowest burn rate constant was detected for the gasoline droplet, while the highest burn rate constant was seen for diesel fuel.Öğe Investigation of combustion properties of triethyl borate, gasoline and triethyl borate-gasoline mixture(Turkish Energy Nuclear and Mining Research Institute, 2024) Sofuoğlu, Duygu; Değirmenci, Hüseyin; Yontar, Ahmet AlperIn recent years, the search for alternative fuels to replace traditional fuels has been of increasing importance and in this context, boron-derived fuels are considered as a promising alternative for next generation energy sources. Accordingly, this study investigates the combustion characteristics of pure and mixed droplets of triethyl borate (TEB), a new generation fuel, and petrol, a conventional fuel. In the study, the evolution of the fuel droplet diameter, flame structure and flame temperature over time were observed with high-speed camera and thermal camera devices. In the experiments, petrol fuel was used as a reference and 20%TEB, 40%TEB, 60%TEB and 80%TEB fuel blends were prepared by adding TEB on a mass basis. Analysis of high-speed camera images showed that TEB-containing fuel droplets have a large non-luminous region during the combustion process, unlike gasoline fuel. In the flames obtained from pure and mixed fuels, the highest flame temperature was recorded in droplets of 80%TEB mixture. In addition, the shortest extinction time was again observed in the 80%TEB mixture. As a result of the experiments, it was found that the shortest ignition delay was observed in 60%TEB fuel droplets and the longest ignition delay was observed in pure gasoline. In general, it was reported that the addition of TEB decreased the ignition delay, increased the total extinction time and increased the temperature during combustion compared to gasoline. The curves of the time-dependent variation of the dimensionless square droplet diameter (D/D0)² of the fuel droplets examined in the study generally exhibited characteristics in accordance with the D²-law. © 2024, Turkish Energy Nuclear and Mining Research Institute. All rights reserved.Öğe INVESTIGATION OF FLOW CHARACTERISTICS FOR A MULTI-STAGE TESLA VALVE AT LAMINAR AND TURBULENT FLOW CONDITIONS(2021) Yontar, Ahmet Alper; Sofuoğlu, Duygu; Değirmenci, Hüseyin; Bicer, Mert Sevket; Ayaz, TahirTesla valve is a passive type check valve that empowers flow in one direction without moving parts used for flow control in mini or microchannel systems. It is a system that can be used for a long time with low fatigue and low wear due to the lack of moving parts in its structure. Besides the cost of production is cheap due to its simple geometry. Also, the Tesla valve differs from all other valves with these features. Allowing or preventing the movement of the fluid is due to the specific design of the profiles inside the valve. In addition, the fluid that encounters obstacles at high velocities continues on its way by gaining thermodynamic properties. The efficiency of the Tesla valve is measured by diodicity, which can be managed by small losses due to direction during forward or reverse flows, primarily along with the flow inlet speed and flow line design. In this study, the variation of the velocities of methane gas in the specially designed Tesla valve has been investigated in detail via numerical analysis. Tesla valve structure with eleven flow control segments was used in the analysis. Moreover, the fluid motion behaviors in both directions were investigated for laminar and turbulent velocities. As a result of the study, the turbulence kinetic energy change and diodicity were determined for methane use in the Tesla valve. Also, different characteristic features of laminar and turbulent flow have been revealed in the tesla valve.
