Yazar "Yontar, Ahmet Alper" seçeneğine göre listele
Listeleniyor 1 - 7 / 7
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Atomization and combustion behavior of nanofuel droplets containing perovskite-type nanoparticles(Elsevier Ltd, 2023) Küçükosman, Rıdvan; Akçay, Aleyna; Yontar, Ahmet Alper; Ünlü, Cumhur Gökhan; Ocakoglu, KasımMetal and metal oxide nanoparticles (NPs) are promising agents for reducing energy consumption and pollution in applications where combustion power generation is provided. This study focuses on the production of new generation perovskite-type metal oxide NPs with enhanced catalytic activity customized for combustion and investigation of their catalytic performance for gasoline. The droplet scale combustion experiments were carried out at ambient temperature, atmospheric pressure and under normal gravity, the experimental processes were recorded with an optical system consisting of a high-speed camera and a thermal camera with a spectral range of 7.5–14 μm, and the combustion and atomization behavior of the nanofuel droplets were characterized. Perovskite-type NPs were produced by sol-gel technique in varying stoichiometric ratios (LaMnO3, La1- XNdXMnO3, La1-XBaXMnO3, Nd1-XBaXMnO3, La0.5NdXBa0.5-XMnO3, x = 0, 0.3) to confirm their catalytic activity’s effect on gasoline droplets’ combustion behavior. Structural characterization of the obtained five different NPs was carried out by SEM and XRD techniques. Chemical analysis, surface area measurements, and spectral properties of the samples were determined by XPS, BET, and UV–Vis spectroscopy, respectively. The results showed that all perovskite-type NPs have particle size range of 25–40 nm. La0.7Nd0.3MnO3 NPs had the highest oxygen adsorption ability and La0.5Nd0.3Ba0.2MnO3 NPs had the largest surface area (393.4898 m2 /g). Perovskite type NPs tended to increase ignition delay and extinction times. The maximum flame temperature of fuel droplets loaded with La0.5Nd0.3Ba0.2MnO3 NPs was 469 ◦C. This temperature was 274 ◦C higher than the maximum flame temperature of the pure gasoline droplet. The outcomes demonstrated that, with the right catalyst design, perovskite-type NPs can perform better as powerful oxidizers and high energy combustion catalysts.Öğe Combustion and secondary atomization behavior of nanofuel droplets laden with hematite, magnetite and lanthanum orthoferrites nanoparticles(John Wiley and Sons Inc, 2023) Küçükosman, Rıdvan; Yontar, Ahmet Alper; Gökhan Ünlü, Cumhur; Ocakoğlu, KasımCurrent research concerns the droplet combustion behavior of gasoline-based nanofuel droplets containing hematite (Fe2O3), magnetite (Fe3O4) and lanthanum orthoferrites (LaFeO3, La0.5Fe1.5O3 and La0.75Fe1.25O3) perovskite type nanoparticles (NPs) at 2.5 % wt. particle loadings. The results showed that the size distribution of hematite and magnetite NPs is on the 90–100 nm scale, while the lanthanum orthoferrites NPs have a particle size distribution of 25–40 nm. The particles with the largest surface area (78,5098 m2/g) and enhanced oxygen adsorbing ability were La0.5Fe1.5O3 NPs. Droplet combustion experiments were recorded with a high speed camera and a 7.5–14 μm spectral area thermal camera. Fe3O4 and LaFeO3 NPs high agglomerate tendency allowed only a single microexplosion event in nanofuel droplets towards the end of the experiment. Only the G/La0.5Fe1.5O3 fuel droplets trended to obey the D2-law. Nanofuel droplets containing La0.5Fe1.5O3 NPs exhibited the highest maximum flame temperature of 264 °C. The catalytic activity of lanthanum orthoferrite perovskite-type NPs during combustion was improved due to the decrease in the La ratio in the A-site and the increase in the Fe ratio in the B-site.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 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 gasoline. The fabrication of r-GO/g-C3N4/LaFeO3 nanohybrid structures was carried out by a two-step hydrothermal method. The structural characterizations 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 containing 0.2 wt.% g-C3N4/LaFeO3 nanohybrid structures had the highest maximum flame temperature of 519 K, and the nanofuel droplets containing 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 hydrocarbon fuels can be increased and soot formation can be reduced at the same time with the new generation of graphene-based functional materials to be created, and thus, many combustion problems can be solved simultaneously with these functional particles.Öğe Combustion characteristics of trimethyl borate, diesel, and trimethyl borate-diesel blend droplets(Elsevier, 2022) Yontar, Ahmet Alper; Özgüner, Ayşe Gizem; Adıgüzel, Mehmet Ali; Üstün, DenizIn this study, droplet tests were carried out for pure and blended forms of diesel fuel, which is the traditional fuel, and trimethyl borate fuel, which is new generation fuels. In this context, the evolution of fuel droplet diameter, flame structure, and flame temperature over time was observed using a high-speed camera and a thermal camera simultaneously. Measurements were made for the addition of 20%, 40%, 60%, and 80% trimethyl borate fuel to diesel fuel in fuel blends. The curves of the time-dependent change of the dimensionless square of the droplet diameter (D/D0)2 of the fuel droplets considered in the study, in general, have been determined to comply with the D2-law. Also, as the amount of diesel rose, there were high changes in droplet distortion and high deviations from the hemispherical geometry, and also elongation in the dominant shape droplet shape changed times. While the highest flame temperature was monitored by the thermal camera in the flame formed by the trimethyl borate droplet, as the amount of diesel fuel in the mixture increased, the maximum flame temperature decreased, but the burning time of the droplet was prolonged. On the other hand, the shortest ignition delay was measured for trimethyl borate, while the longest ignition delay time was detected for diesel fuel droplet. In general, it has been observed that the addition of trimethyl borate reduces the ignition delay, shortens the extinction time, and increases the temperature during combustion compared to diesel.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.
