SDG 7 · Erişilebilir ve Temiz Enerji · SDG · Erzincan Binali Yıldırım Üniversitesi

Yazarlar

Yayınlar

Yeniden eskiye Eskiden yeniye

ArticleYalnız künye2021/r/ebyu/14454
Evaluation of the al/, cu/, si/, ag/water nanofluid effects on heat transfer characteristics in vver-1200 loaded with plutonium-thorium-based fuel
Genc, Yasin; Uzun, Sinem; Acir, Adem
This study is aimed at investigation of the potential effects of various nanoparticles used in certain properties and ratios in the coolant of VVER-1200 power plant on thermal hydraulic performance. Criticality and thermal hydraulic analysis have been performed by using MCNP and COBRA-IV/PC code, respectively. The fuel ratio has been selected as 90% ThO2 + 10% reactor grade (RG)-PuO2. Al, Cu, Si, and Ag nanoparticles in proportions of 0.01% and 0.1% by volume have been mixed with reactor coolant water. The effects of adding nanoparticles into the coolant at two different ratios on the reactor criticality, departure from nucleate boiling ratio (DNBR), and thermal hydraulic performance have been investigated. It is observed that by adding nanoparticles into the coolant, the temperature rise along the hottest channel is higher compared to the case when only water is used as the coolant, whereas the criticality and DNBR have shown a decreasing trend. It can be concluded that combination of fuel made up of 90% ThO2 + 10% RG-PuO2 and nanofluid containing 0.1% volumetric ratio of Si nanoparticle could be used in VVER-1200 nuclear power plant and this combination could contribute to augmentation of thermal efficiency of the plant.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14439
Effects of MWCNTs/graphene nanoflakes/MXene addition to TiO2 thick film on hydrogen gas sensing
Chachuli, Siti Amaniah Mohd; Hamidon, Mohd Nizar; Ertugrul, Mehmet; Mamat, Md Shuhazlly; Coban, Omer; Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Shamsudin, N.H.
Various doping materials, such as MWCNTs, graphene nanoflakes and MXene, have been doped into TiO2 and the hydrogen sensing properties investigated. Using a similar volume, MWCNTs (5 wt.%) and graphene nanoflakes (5 wt.%) and MXene (10 wt.%) were added to TiO2 and prepared in a paste form by mixing the sensing material with the organic binder. The sensing film was deposited on an alumina substrate using a screen-printing technique and annealed at 500 °C for 30 min in ambient air. The crystallinity of TiO2 and the doped material in the sensing film after the annealing treatment were verified using FESEM, EDX, XRD and Raman Spectroscopy. By depositing an interdigitated electrode at the bottom of the sensing film, the thick film gas sensors (TiO2/MWCNT, TiO2/Gr, TiO2/MXene) were exposed to 100–1000 ppm of hydrogen at an operating temperature of 100–250 °C. The responses showed that the addition of MWCNTs and MXene to TiO2 reduced the operating temperature of the TiO2 gas sensor from 150 °C to 100 °C, while the addition of graphene nanoflakes did not affect the operating temperature of the TiO2 gas sensor. The TiO2/MWCNT gas sensor showed linear sensitivity as hydrogen concentrations increased for operating temperatures of 100–250 °C. The optimal operating temperature for TiO2/MXene occurred at 100 °C, while the optimal operating temperature for the TiO2/Gr gas sensor occurred at 200 °C. The highest sensitivity for 100–500 ppm hydrogen was generated by the TiO2/MXene gas sensor, and for 600–1000 ppm hydrogen was generated by the TiO2/MWCNT gas sensor at an operating temperature of 250 °C. The TiO2/MWCNT gas sensor produced the highest sensitivity to hydrogen at the operating temperature of 250 °C with sensitivity values of approximately 6.36, 33.61, 67.64, 102.23 and 159.07 for 100, 300, 500, 700 ppm and 1000 ppm of hydrogen, respectively.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2021/r/ebyu/14360
Swirler geometry effects (Dh /do ratio) on synthetic gas flames: Part 1: Combustion and emission characteristics; [Suktuvo geometrijos (Dh /do ) poveikis sintetinių dujų liepsnoms. 1 dalis: degimo ir emisijų charakteristikos]
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker
Swirling flows increase combustion performance via favour-ing flame stability, pollutant emissions, and combustion in-tensity. The strength of a swirling flow is characterized by a parameter known as swirl number, which is highly related to the dh /do ratio. In this study, effects of the swirler dh /do ratio on combustion and emission characteristics of the synthetic gas flames of premixed 20%CNG/30%H2 /30%CO/20%CO2 mix-ture were experimentally investigated in a laboratory-scale swirl stabilized combustor. For this purpose, twelve different swirl generators were designed and manufactured. dh /do ratios of these swirlers were set as 0.30 and 0.50, and the geometric swirl number was varied between the values of 0.4 and 1.4 (at 0.2 intervals). All experiments were conducted at a fuel-lean equivalence ratio (ϕ = 0.6), room temperature, and local at-mospheric conditions of the city of Kayseri, Turkey. A data logger was utilized to plot axial and radial temperatures and NOx, CO, and CO2 profiles, which were exploited to assess combustion and emission performance. Results showed that the dh /do ratio had a non-monotonic effect on the behaviour of combustion and emission of the tested synthetic gas mix-ture. Depending on the swirl number, increments and dec-rements were observed in temperature and emission values. ENERGETIKA. 2021. T. 67. Nr. 1–2. P. 48–54
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2021/r/ebyu/14288
A new boost converter-based soft switched active snubber cell for power factor correction
Ting, N. Suleyman; Sahin, Y.; Yetgin, H.
This paper introduces a new boost converter-based soft switched active snubber cell for power factor correction. In this particular converter, the main switch is turned on through Zero Voltage Transition (ZVT) and is turned off with the aid of Zero Voltage Switching (ZVS). The main diode is turned on using ZVS and is turned off using Zero Current Switching (ZCS). In the active snubber cell, the auxiliary switch is turned on by means of ZCS and is turned off using Zero Current Transition (ZCT). No semiconductor device is exposed to additional voltage stress. In this paper, theoretical analysis of the proposed converter is exhibited and validated by both simulation and experimental studies while operating at 100 kHz switching frequency and 600 W output power. It is demonstrated that the proposed converter is of 95.7% efficiency and 0.99 unit power factor in the soft-switching operation.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14237
Architecture design and performance analysis of a hybrid hydrogen fuel cell system for unmanned aerial vehicle
Ozbek, Emre; Yalin, Gorkem; Karaoglan, Mustafa Umut; Ekici, Selcuk; Colpan, C. Ozgur; Karakoc, T. Hikmet
The flight endurance of UAV systems is an important issue that restricts the operational capabilities. Thus, different energy systems and alternative onboard energy generation systems have been tested for the UAVs. Within these systems, fuel cells provide high energy density that can increase flight endurance greatly. In this study, a PEM fuel cell – Li-Po battery hybrid system has been developed by evaluating three architecture models. In the guide of the experimental power demand data of a fixed-wing UAV, modeling and testing procedures were performed. Battery voltage and fuel cell current variations observed during the ground tests were evaluated. It has been observed that approximately 160–170 W of the 250 W power is met by the fuel cell since no preconditioning has been applied and the temperature values at which the fuel cell exhibits its optimum performance. In the case where the fuel cell could provide 7.8 An under conditions where the humidification effects were not included in the model, the required current was over 7.8 A between approximately 400-1200 s. The fuel cell and battery behavior in response to the sudden power changes and to the uncertainties corresponding to the changes in the motor power during the flight are also detailed.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14229
THERMAL ANALYSIS OF THE VVER-1000 REACTOR WITH THORIUM FUEL AND COOLANT CONTAINING Al2O3, CuO, AND TiO2 NANOPARTICLES
Acır, Adem; Uzun, Sinem; Genç, Yasin; Asal, Şulenur
The use of nanofluids has recently gained importance in studies carried out on increasing reactor efficiency with attention paid on safety factors in nuclear technology. Nanofluids used in reactor cooling water at certain properties and ratios generally use enriched UO2 as fuel. Through the discovery of thorium reserves and its use in nuclear technology, thorium has also become a candidate for being used as a fuel material in reactors. In this study, using ThO2 fuel and Al2O3, CuO, and TiO2 nanoparticles of the coolant in different ratios, the neutronic and thermal properties of the reactor, especially the criticality and temperature of coolant and DNBR as three leading parameters, were investigated. For the analyses, 5%, 10%, 15%, and 20% ThO2 was added to the reactor core containing 3.7% enriched UO2 fuel, and the analyses were performed adding 0.01%, 0.05%, and 0.1% volume of nanoparticles to the coolant water. Neutronic calculations were carried out with the help of MCNP code and COBRA-IV PC code was used for thermal analysis. The obtained results showed that by adding nanoparticles to coolant and using thorium as an additive to fuel the rise of coolant temperature can be augmented by 4.67 K compared to traditional combination of UO2 fuel and water while reactor remained within safety limits.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14219
Homogenized pouch cell material modelling and a comparison study
Orhan, Osman; Özel, Adnan
Simulation of the mechanical response of lithium-ion battery cells is preferably over experimental due to the explosive nature of them. There are several mechanical modelling methods for representing pouch cells; this study introduces a modified homogenized model. The model uses mechanical responses of layers from literature to establish an average behavior of a pouch cell. Data is normalized, then unified tension and compression stress-strain curves are gathered. These properties are used to build a homogenized pouch cell model by using a tension and compression plasticity model. A stress state dependent failure model (GISSMO) is utilized to demonstrate the damage of cell. Finally, experimental studies from literature are employed for validation. As a result, the model simulates peak forces of all experimental studies with a very low deviation. Homogenizing pouch cell with the proposed approach eliminates modeling detail without compromising the overall mechanical response of the cell. The model is seen to be suitable for applications that do not require a precise mechanical response, such as a battery module or pack analysis.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14187
Experimental Investigation of Flame Characteristics of H2/CO/CH4/CO2 Synthetic Gas Mixtures
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker
Chemical composition of synthetic gas and concentration of its components depend on gasification process and feedstock. Synthetic gas mainly consists of hydrogen (H2) and carbon monoxide (CO), and may contain trace amounts of carbon dioxide (CO2) and methane (CH4). In this study, combustion and emission characteristics of H2/CO/CH4/CO2 blending syngas mixtures with high H2/CO ratio were experimentally investigated in a swirl-stabilized premixed combustor. Furthermore, stable operating ranges (flashback and blowout equivalence ratios) of such mixtures and flame response of 67.5%H2-22.5%CO-5%CO2-5%CH4 mixture to acoustic forcing were also detected. During the experiments, CH4 amount in tested gas mixtures varied between 5% and 20% by volume (at intervals of 5%), and H2/CO ratio and CO2 concentration were kept constant at the values of 3 and 5%, respectively. As a consequence, mixtures of 67.5%H2-22.5%CO-5%CO2-5%CH4, 63.75%H2-21.25%CO-5%CO2-10%CH4, 60%H2-20%CO-5%CO2-15%CH4 and 56.25%H2-18.75%CO-05%CO2-20%CH4 were derived and tested under the same boundary and physical conditions. All experiments were conducted at 0.4 equivalence ratio (Φ) and 0.2 geometric swirl number (SN). Preliminarily, stable operating ranges of respective gas mixtures were determined to find an equivalence ratio at which all gas mixtures could be tested without causing any flame instability and then, CH4 addition effects on combustion and emission characteristics of such mixtures were evaluated via utilizing axial and radial temperature, CO and O2 profiles. Lastly, flame behavior of 67.5%H2-22.5%CO-5%CO2-5%CH4 mixture was evaluated under externally modified acoustic conditions. Acoustic field in the combustor was mechanically altered by using side-mounted loudspeakers in the frequency range of 30–200 Hz. To identify flame instabilities and to evaluate the degree of coupling between heat release and pressure oscillations, pressure sensors and photodiodes installed on combustion chamber and burner were utilized. Results of this study showed that CH4 addition to synthetic gas mixtures improves rich flammability limits, and increases flame temperature, flame height and emissions. Under externally modified acoustic conditions, flame behavior slightly alters (flashback and blowout does not occur). Additionally, pollutant emissions improve in an environment-friendly manner under such conditions.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2021/r/ebyu/14169
Swirler geometry effects (Dh/do ratio) on synthetic gas flames. part 2: Dynamic flame behaviour at externally altered acoustic conditions; [Suktuvo geometrijos (Dh/do ) poveikis sintetinių dujų liepsnoms. 2 dalis: dinaminė liepsnos elgsena veikiant išorėje pakeistomis akustinėmis sąlygomis]
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker
In a combustion device, unsteady heat release causes acoustic energy to increase when acoustic damping (energy loss) is not that effective, and, as a result, thermo-acoustic flame instabilities occur. In this study, effects of the swirler dh/do ratio (at different swirl numbers) on dynamic flame behaviour of the premixed 20%CNG/30%H2/30%CO/20%CO2 mixture under externally altered acoustic boundary conditions and stability limits (flashback and blowout equivalence ratios) of such mixture were investigated in a laboratory-scale var-iable geometric swirl number combustor. Therefore, swirl generators with different dh/do ratios (0.3 and 0.5) and geometric swirl numbers (0.4, 0.6, 0.8, 1.0 1.2 and 1.4) were designed and manufactured. Acoustic boundary conditions in the combustion chamber were altered using loudspeakers, and flame response to these conditions was perceived using photodiodes and pressure sensors. Dynamic flame behaviour of respective mixture was evaluated using luminous intensity and pressure profiles. Results showed that the dh/do ratio has a minor impact on dynamic flame behaviour.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2021/r/ebyu/14160
Zero-voltage switching half-bridge pulse width modulation DC–DC converter with switched capacitor active snubber cell for renewable energy applications
Bodur, Haci; Yesilyurt, Huseyin; Ting, Naim Suleyman; Sahin, Yakup
In this paper, soft switching isolated half-bridge converter with a new active snubber cell that uses switched capacitor for renewable energy applications is proposed. The proposed snubber cell does not consist any magnetic element so that its structure is quite simple. Furthermore, the auxiliary switches in the proposed active snubber cell are exposed to only half of the input voltage. There is no additional voltage and current stress on any semiconductor devices. All semiconductor power devices in the proposed converter are operated by soft switching. The proposed converter is analyzed thoroughly, and the theoretical analyzes are affirmed by an implementation having 300-VDC input, 20-VDC output, 75-W output power, and 150-kHz switching frequency. The overall hard switching efficiency of the converter is increased from 86.4% to 92.9% by aid of the proposed soft switching snubber cell.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2021/r/ebyu/14115
Application of BiFeO3 and Au/BiFeO3 decorated kaolinite nanocomposites as efficient photocatalyst for degradation of dye and electrocatalyst for oxygen reduction reaction
Caglar, Bulent; Guner, Eda Keles; Özdokur, Kemal Volkan; Özdemir, Agah Oktay; İçer, Fatih; Caglar, Sema; Doğan, Bilge; Beşer, Burcu Meryem; Çırak, Çağrı; Tabak, Ahmet
To improve the photocatalytic performance and solve the aggregation problem of BiFeO3 nanoparticles, kaolinite-BiFeO3 photocatalyst was successfully prepared for the first time by decoration of ferromagnetic BiFeO3 nanoparticles onto kaolinite surface. Comparative characteristics of kaolinite, bare BiFeO3 and kaolinite-BiFeO3 photocatalyst were investigated in detail by XRD, TEM, SEM-EDX, XPS, FTIR, VSM, UV-DRS, PL, zeta potential and BET techniques. The photocatalytic activities of the samples were also evaluated by photodegradation of rhodamine B as a model reaction under different irradiations like UVA, visible and sunlight. The kaolinite-BiFeO3 exhibited more superior photocatalytic activity as compared with other samples, which is best fitted to pseudo-first-order kinetic. The reactive species trapping experiments indicated that photogenerated-holes play major roles in the degradation process whereas superoxide radicals possess a secondary effect. Enhanced photocatalytic activity of kaolinite-BiFeO3 is attributed to its kaolinite platform that reduces the recombination opportunities of the photogenerated holes and electrons as well as increases the surface area, decreases the particle size and aggregation of nanoparticles. In addition, we also designed a novel electrocatalytic platform based on gold nanoparticles loaded on kaolinite-BiFeO3 modified carbon paste electrode surface for the examination of electrocatalytic activity for oxygen reduction reaction in alkaline medium. Electrochemical characterizations of the Au/BiFeO3/kaolinite modified carbon paste electrode and other bare surfaces were comparatively carried out with the aid of cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Au/BiFeO3/kaolinite modified carbon paste electrode exhibited 15-fold current enhancement together with 100 mV anodic potential shift compared with bare carbon paste electrode.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/22162
Design, Producing and Testing of 12-Step Three-Phase Voltage Source Inverter with Flexible Independent PWM Current Control for Brushless Direct Current Motor
Özgenel, Mehmet
Brushless motors are used in wide areas in the industrial and domestic applications owing to their superior advantages over other type electric motors such as induction and brushed direct current motors. Owing to fact that the brushless direct current motors and their drivers are cheaper and easier to design than drives of permanent magnet synchronous motors, brushless direct current motors are preferred a large application areas. But BLDC motor drivers are still run classical three-phase six- step inverter. Because of that the BLDC motors are run classical three-phase six-step inverter, the BLDC motor does not show its real dynamic performance. If BLDC motor is run via 12-step inverter, it gives a better dynamic performance than that of six-step inverter. The aim of this study, to manufacture 12-step inverter which controls phase currents using pulse width modulation (PWM) technique and to analyze the dynamic performance of BLDC motor running under purposed 12-step inverter. In the 12-step inverter, two or three transistors are on conduction mode at each time interval alternatively and in order to keep switching losses minimum only one transistor runs PWM mode in this study. The experimental results show that purposed flexible independent PWM 12-step inverter works perfectly and this proposed inverter provides the BLDC motor generating high dynamic performance than that of six-step one.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/20934
Two-step synthesis of MnCo2S4 nanowires for supercapacitor electrode
Yeşilbağ, Yaşar Özkan
In this study, MnCo2S4 nanowires were synthesized on 3D-Ni foam by the hydrothermal process in two-step and investigated as supercapacitor electrode material. Crystal structure and morphology analyzes of MnCo2S4 nanowires were performed. Electrochemical measurements were taken in 1 M of a potassium hydroxide aqueous electrolyte solution. The specific capacitance value calculated from GCD measurement taken at a current density of 0.5 A g−1 from the sample was 450 F g−1 . Furthermore, the sample have good cycling stability by keeping 46% of the initial specific capacitance after 3000 cycles.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/20933
Investigation of Flower-like ZnCo2O4 Nanowire Arrays Growth on 3D-Ni Foam as Supercapacitor Electrode Material
Yesilbag, Fatma Nur Tuzluca
As a supercapacitor electrode material, flower-like ZnCo2O4 nanowire (NW) arrays were directly grown on 3D-Ni foam using the hydrothermal method. Structural and morphological analysis of the electrode material was characterized by XRD, FE-SEM, and EDS, while its electrochemical analysis was characterized by CV, GCD, and EIS. The electrode material demonstrated excellent electrochemical performance with a maximum areal capacitance of 1.01 F cm-2 at a current density of 0.5 mA cm-2 . After 2.000 charge-discharge cycles, the electrode showed excellent cycle stability, having 72% of the initial areal capacitance.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/18416
Investigation of Criticality and Relative Power Density Distribution in VVER-1000 Nuclear Power Reactor
Genç, Yasin; Uzun, Sinem; Acir, Adem
One of the most important elements of the design and safe operation of nuclear power reactors is the examination of the criticality and relative power density distribution. In this study, the neutronic performance analysis of the VVER-1000 containing the critical and relative power density distribution was calculated with the help of the MCNP neutronic code. Neutronic calculations were performed for four different fuel types. As a result of the calculations for each fuel assembly, criticality and relative power density distributions were obtained in the reactor core. The results obtained in this study were compared with the literature and it was seen that the critical and relative power density distribution values were similar.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/17960
Selection of solar energy supply facility location with robust optimization and an application
Karabulut, Turgut; Yavuz, Selahattin
Energy is a constant need and this need is a growing resource. Renewable energy, which is one of these energy sources, is very important for our world to be both clean and sustainable. One of the central belt countries in the world, Turkey is a very fortunate country in terms of renewable energy sources. In this study, a model for solar energy source installation and energy efficiency has been proposed for Erzurum, Erzincan, and Sivas. This model has been solved by deterministic and robust optimization. Pursuant to the results obtained from the solutions with these methods, the most suitable location has been determined. At the end of the study, it has been found out that Erzurum is the most suitable city for the selection of the location according to both solutions. According to deterministic solution for Erzurum, the efficiency has been observed between 83950724.1 and 87591854.81 while it has been between 83416034.92 and 87065524.19 according to robust solution. There has been an approximately 0.618% difference between these two solutions.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2020/r/ebyu/15209
Fabrication and characterization of transparent Cr-decorated TiO2 nanoporous electrode for enhanced photo-electrocatalytic performance
Çırak, Burcu Bozkurt
A Cr-decorated TiO2 nanoporous transparent electrode was fabricated by DC sputtering, anodization, and thermal evaporation methods, respectively. Ti films were deposited on fluorine-doped tin oxide (FTO) coated glass and anodized to obtain a transparent TiO2 nanoporous film (TN). The fabricated electrodes were characterized using a field emission scanning electron microscope (FESEM), atomic force microscope (AFM) and X-Ray diffraction (XRD). Photoelectrochemical activity of prepared films was investigated by photo-electrocatalytic degradation of RhB dye under constant voltage and UVA light irradiation. The Cr-decorated TiO2 nanoporous film (CTN) served as an electrode and exhibited better photo-electrocatalytic performance than a TN electrode. Results show that Cr decoration increased photoelectrochemical activity significantly due to more efficient charge separation and lower recombination rate.
RDL Kalıcı Kaydıİncele
ArticleYalnız künye2020/r/ebyu/15171
Experimental investigation of flame instability in a premixed combustor
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker
In this study; effects of fuel composition, equivalence ratio and swirl number on flame behavior (dynamic and static) of premixed 100% CNG, CNG-H2, CNG-H2-CO and CNG-H2-CO2-CO mixtures under externally altered acoustic conditions were experimentally investigated in a laboratory scale swirl stabilized combustor. During experiments, the amount of CNG in all gas mixtures tested was set as 20% and 40% by volume except for the CNG-H2 mixture. Moreover, H2/CO ratios of CNG-H2-CO mixtures were arranged to be able to provide low, medium or high heating value. To better represent synthetic gas, CNG-H2-CO mixture was then diluted with the same amount of CO2, and mixtures of CNG-H2-CO2-CO with varying H2/CO ratios were achieved to evaluate effects of CO2 dilution (in addition to flame behavior) on flame characteristics (i.e. performance metrics such as flame temperature and emissions). Acoustic field of the combustor was altered via side mounted loudspeakers to trigger combustion instabilities, and under these circumstances, flame behavior was evaluated by examining instantaneous flame images, pressure and luminous intensity profiles. Data obtained from pressure transducers and photodiodes was also utilized to detect whether dynamic instabilities, i.e. thermoacoustic instabilities, excite static instabilities such as blowout, flashback, and flame liftoff etc. or not. Results of this study showed that fuel composition, equivalence ratio and swirl intensity are determinant parameters on flame behavior. Two main inferences of this study are: swirl number has a monotonic impact on flame stability characteristics (1); under externally excited acoustic conditions, CO2 presence in gas mixtures makes flames more resistant to dynamic instabilities (less axial and radial oscillations) and blowout but it increases flashback tendency (2).
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/15032
Energy transformation without using filter on high resistive load
Can, Erol
In this paper, 9-level, 17-level, 19-level, 21-level, 27-level, and 39- level inverters with SPWM are presented. According to a switching function, the high-multilevel inverter design has been described since a new multi-level inverter structure is considered. The multilevel inverter structure is designed with placing switches and sources on levels. Pulse width modulation, controlling switches in the inverter structure, is also produced by comparison between triangles and sinus signals. Operating sequences of the switches are given in the table in order to demonstrate the inverter operation characteristic with the produced signals. Then, mathematical equations are formed by considering an operation of switches on the load. In simulations and experiments, the 9-level, 17-level, 19-level, 21-level, 27-level, and 39-level inverters are performed on the resistance (R) and inductance (L) loads with different resistance, because it is difficult to generate current and voltage with an acceptable harmonic distortion on the impedances which have high ohmic values. After applications of experimentation and simulation, the obtained results are compared with other published papers of results and the international IEEE standard, which is 5% for harmonic distortions of creating currents and voltages.
RDL Kalıcı Kaydıİncele
ArticleAçık Erişim2020/r/ebyu/15030
Graphene/polyaniline nanocomposite as platinum-free counter electrode material for dye-sensitized solar cell: its fabrication and photovoltaic performance
Bayram, Ozkan; Igman, Erdal; Guney, Harun; Demir, Zeynep; Yurtcan, Mustafa Tolga; Cirak, Cagri; Hasar, Ugur Cem; Simsek, Onder
In this study, it was aimed to produce graphene/polyaniline nanocomposite thin films as counter electrode materials by PECVD system and to determine the photovoltaic performances of these counter electrodes in dye-sensitized solar cells (DSSCs). Graphene/polyaniline counter electrode (GPCE) material was produced in two different steps. Firstly, a single-layer and multilayer graphene thin films were produced on the fluorine-doped tinoxide (FTO) substrates. Then, polyaniline (PANI) thin films were grown on each graphene thin films using plasma polymerization technique, and eventually the production of the graphene/PANI nanocomposite was completed. The fabricated graphene/PANI nanocomposites were used in place of platinum (Pt)-counter electrode which is widely used in DSSCs and the photovoltaic performance of these counter electrodes was investigated. The DSSCs consisted of titanium dioxide (TiO2) nanotube photoanode, N719 dye, iodolyte liquid electrolyte, and graphene/PANI nanocomposite counter electrode. I–V measurements were carried out in order to calculated photoconversion efficiency (PCE) and it was found that the these efficiency of GPCEs changed between 0.56 and 1.36% according to the number of graphene layers. The photovoltaic performance of DSSC, consisting of TiO2 nanotube photoanode and Pt-counter electrode was 1.1%.
RDL Kalıcı Kaydıİncele