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

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Book ChapterYalnız künye2018/r/ebyu/15440
Numerical simulation of building wall integrated with phase change material: A case study of a Mediterranean City Izmir, Turkey
Asker, Mustafa; Alptekin, Ersin; Tokuç, Ayça; Ezan, Mehmet Akif; Ganjehsarabi, Hadi; Nizetic, S; Papadopoulos, A
Nowadays, improving the energy efficiency of buildings without decreasing the comfort of its occupants is of great importance in the whole world. The most widespread passive energy control strategy is the utilization of insulation materials with low thermal transmittance. This chapter proposes an alternative control strategy that would help to create more stable temperatures inside a room. This is changing the thermal capacity of a common wall with the integration of phase change material (PCM). To evaluate the performance of the PCM, user-defined scripts are coded in commercial CFD solver ANSYS FLUENT to simulate one-dimensional heat transfer through a wall within a detached cabin in a city with Mediterranean climate for 1 day in the hot season. The placement and amount of PCM in the building element are changed and analyzed. The results show a decrease in the indoor wall temperature up to 6 °C, which is promising for further research.
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ArticleYalnız künye2018/r/ebyu/15370
A soft switching with reduced voltage stress ZVT-PWM full-bridge converter
Sahin, Yakup; Ting, Naim Suleyman; Acar, Fatih
This paper introduces a novel active snubber cell for soft switching pulse width modulation DC-DC converters. In the proposed converter, the main switch is turned on under zero voltage transition and turned off under zero voltage switching (ZVS). The auxiliary switch is turned on under zero current switching (ZCS) and turned off under zero current transition. The main diode is turned on under ZVS and turned off under ZCS. All of the other semiconductors in the converter are turned on and off with soft switching. There is no extra voltage stress on the semiconductor devices. Besides, the proposed converter has simple structure and ease of control due to common ground. The detailed theoretical analysis of the proposed converter is presented and also verified with both simulation and experimental study at 100 kHz switching frequency and 600 W output power. Furthermore, the efficiency of the proposed converter is 95.7% at nominal power.
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ArticleYalnız künye2018/r/ebyu/15355
Assessment of different bio-inspired flow fields for direct methanol fuel cells through 3D modeling and experimental studies
Ouellette, David; Ozden, Adnan; Ercelik, Mustafa; Colpan, C. Ozgur; Ganjehsarabi, Hadi; Li, Xianguo; Hamdullahpur, Feridun
The performance impact of using bio-inspired interdigitated and non-interdigitated flow fields (I-FF and NI-FF, respectively) within a DMFC is investigated. These two flow fields, as well as a conventional serpentine flow field (S-FF, used as a reference), were examined as possible anode and cathode flow field candidates. To examine the performance of each of these candidates, each flow field was manufactured and experimentally tested under different anode and cathode flow rate combinations (1.3 mL/min [methanol] and 400 mL/min [oxygen], as well as 2 and 3 times these flow rates), and different methanol concentrations (0.50 M, 0.75 M, and 1.00 M). To help understand the experimental results and the underlying physics, a three dimensional numerical model was developed. Of the examined flow fields, the S-FF and the I-FF yielded the best performance on the anode and cathode, respectively. This finding was mainly due to the enhanced under-rib convection of both of these flow fields. Although the I-FF provided a higher mean methanol concentration on the anode catalyst layer surface, its distribution was less uniform than that of the S-FF. This caused the rate of methanol permeation to the cathode to increase (for the anode I-FF configuration), along with the anode and cathode activation polarizations, deteriorating the fuel cell performance. The NI-FF provided the lowest pressure drops of the examined configurations. However, the hydrodynamics within the flow field made the reactants susceptible to traveling directly from inlet to outlet, leading to several low concentration pockets. This significantly decreased the reactant uniformity across its respective catalyst layer, and caused this FFs performance to be the lowest of the examined configurations.
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ArticleYalnız künye2018/r/ebyu/15319
Synthesis of In 2 O 3 nanostructures with different morphologies as potential supercapacitor electrode materials
Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Ertugrul, Mehmet
In this study performed using a chemical vapor deposition (CVD) system, one-dimensional (1-D) single crystal indium oxide (In 2 O 3 ) nanotowers, nanobouqets, nanocones, and nanowires were investigated as a candidate for a supercapacitor electrode material. These nanostructures were grown via Vapor–Liquid–Solid (VLS) and Vapor–Solid (VS) mechanisms according to temperature differences (1000–600 °C). The morphologies, growth mechanisms and crystal structures of these 1-D single crystal In 2 O 3 nanostructures were defined by Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HR-TEM), X-Ray Diffraction (XRD) and Raman Spectroscopy analyses. The elemental analyses of the nanostructures were carried out by energy dispersive X-Ray Spectroscopy (EDS); they gave photoluminescence (PL) spectra with 3.39, 2.65, and 1.95 eV band gap values, corresponding to 365 nm, 467 nm, and 633 wavelengths, respectively. The electrochemical performances of these 1-D single crystal In 2 O 3 nanostructures in an aqueous electrolyte solution (1 M Na 2 SO 4 ) were determined by Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) analyses. According to GCD measurements at 0.04 mA cm −2 current density, areal capacitance values were 10.1 mF cm −2 and 6.7 mF cm −2 for nanotowers, 12.5 mF cm −2 for nanobouquets, 4.9 mF cm −2 for nanocones, and 16.6 mF cm −2 for nanowires. The highest areal capacitance value was observed in In 2 O 3 nanowires, which retained 66.8% of their initial areal capacitance after a 10000 charge-discharge cycle, indicating excellent cycle stability.
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ArticleYalnız künye2018/r/ebyu/15300
Interfacial engineering of CuO nanorod/ZnO nanowire hybrid nanostructure photoanode in dye-sensitized solar cell
Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Gur, Emre; Kocak, Yusuf
Developing efficient and cost-effective photoanode plays a vital role determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Here, we demonstrate DSSCs that achieve relatively high power conversion efficiencies (PCEs) by using one-dimensional (1D) zinc oxide (ZnO) nanowires and copper (II) oxide (CuO) nanorods hybrid nanostructures. CuO nanorod-based thin films were prepared by hydrothermal method and used as a blocking layer on top of the ZnO nanowires’ layer. The use of 1D ZnO nanowire/CuO nanorod hybrid nanostructures led to an exceptionally high photovoltaic performance of DSSCs with a remarkably high open-circuit voltage (0.764 V), short current density (14.76 mA/cm2 under AM1.5G conditions), and relatively high solar to power conversion efficiency (6.18%). The enhancement of the solar to power conversion efficiency can be explained in terms of the lag effect of the interfacial recombination dynamics of CuO nanorod-blocking layer on ZnO nanowires. This work shows more economically feasible method to bring down the cost of the nano-hybrid cells and promises for the growth of other important materials to further enhance the solar to power conversion efficiency.
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ArticleAçık Erişim2018/r/ebyu/15282
Fabrication of Pt/Pd nanoparticles/polyoxometalate/ionic liquid nanohybrid for electrocatalytic oxidation of methanol
Medetalibeyoglu, Hilal; Manap, Sevda; Yokus, Özlem Aktaş; Beytur, Murat; Kardas, Faruk; Akyıldırım, Onur; Ozkan, Vildan; Yüksek, Haydar; Yola, Mehmet Lütfi; Atar, Necip
Fuel cells have important applications in recent decades due to high-energy demands, fossil fuel depletions, and environmental pollution throughout world. Pt/Pd nanoparticles/polyoxometalate/ionic liquid (ILs) nanohybrid synthesized for the first time and characterized by transmission electron microscope, scanning electron microscope, X-ray photo electron spectroscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction method. A cost-effective catalyst has been developed on Pt/Pd nanoparticles/polyoxometalate/ionic liquid nanohybrid. The developed catalyst based on bimetallic nanoparticle demonstrates effective methanol oxidation in comparison with catalysts on monometallic nanoparticle and polyoxometalate/ionic liquid nanohybrid.
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Conference ObjectYalnız künye2018/r/ebyu/15264
Entropy generation analysis of multilayer PCM slabs integrated with fins
Asker, Mustafa; Alptekin, Ersin; Ezan, Mehmet Akif; Ganjehsarabi, Hadi
In this study, the utilisation of composite phase change materials (PCMs) slabs with fins in a thermal energy storage (TES) system is numerically analysed. The storage system consists of three PCM layers at different melting temperatures. First, the predicted results are verified against the analytical solution that is taken from literature. Afterwards, the influence of the design parameters such as fin length and fin spacing on time for complete melting of the multi-layer TES are examined. Custom field functions are integrated into the ANSYS-FLUENT software to assess the local and volume averaged entropy generation within the system. The results show that at constant fin spacing, that increasing fin length from 20 mm to 80 mm enhances the melting rate up to 50%. In addition, when the fin spacing is doubled, the elapsed time for complete melting decreased about 37%. Moreover, the fin arrangement has a considerable effect on entropy generation.
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ArticleYalnız künye2017/r/ebyu/16388
Effect of different turbulence models on combustion and emission characteristics of hydrogen/air flames
Yilmaz, Harun; Cam, Omer; Tangoz, Selim; Yilmaz, Ilker
This paper aims to present modeling results of hydrogen/air combustion in a micro-cylindrical combustor. Modeling studies were carried out with different turbulence models to evaluate performance of these models in micro combustion simulations by using a commercially available computational fluid dynamics code. Turbulence models implemented in this study are Standard k-ε, Renormalization Group k-ε, Realizable k-ε, and Reynolds Stress Transport. A three-dimensional micro combustor model was built to investigate impact of various turbulence models on combustion and emission behavior of studied hydrogen/air flames. Performance evaluation of these models was executed by examining combustor outer wall temperature distribution; combustor centerline temperature, velocity, pressure, species and NOx profiles. Combustion reaction scheme with 9 species and 19 steps was modeled using Eddy Dissipation Concept model. Results obtained from this study were validated with published experimental data. Numerical results showed that two equation turbulence models give consistent simulation results with published experimental data by means of trend and value. Renormalization Group k-ε model was found to give consistent simulation results with experimental data, whereas Reynolds Stress Model was failed to predict detailed features of combustion process.
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ArticleYalnız künye2017/r/ebyu/16345
Designing, modeling and performance investigation of bio-inspired flow field based DMFCs
Ozden, Adnan; Ercelik, Mustafa; Ouellette, David; Colpan, C. Ozgur; Ganjehsarabi, Hadi; Hamdullahpur, Feridun
In an attempt to improve upon conventional flow fields (e.g., serpentine flow field), Murray's Law was applied to design two different bio-inspired, leaf-shaped flow fields. This law governs the dimensions of natural networks, such as: the veins within plant leaves and human lungs. In this study, the serpentine, the lung, and the two leaf-shaped flow fields were used to form seven different anode–cathode combinations. The experiments focused on the effects of methanol concentration (0.50 M, 0.75 M, and 1.00 M) and the combined effect of methanol and oxygen flow rates (1.3 ml/min methanol and 400 ml/min oxygen, as well as 2 and 3 times both of these flow rates). An analytical model was also developed to help understand the experimental results. The results show that the highest performance could be achieved when the bio-inspired configurations were used on the cathode. The best configuration was the serpentine (anode) – second leaf design (cathode), with a peak power density of 888 W/m2. For comparison, a peak power density of 824 W/m2 was achieved when the serpentine flow field was used on the anode and cathode. Furthermore, of all the tested configurations, the lung-based flow field provided the lowest performance in all tests.
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ArticleYalnız künye2017/r/ebyu/16303
Novel high multilevel inverters investigated on simulation
Can, Erol
This paper presents a novel high multilevel inverter topology which is based on the created DC voltage levels at loads of the inverter. The circuit model is demonstrated by explaining the relationship between switches, sources and loads. According to the proposed inverter topology, the number of power switches connected to negative side of DC source is constant on inverter, while the number of power switches connected to positive side of DC sources is increasing. Therefore, linear pulse-width modulation (LPWM) is described for operating switches after pulse-width modulation method is developed to generate the PWM signals. Then, mathematical equations are given when resistive (R), inductive (L) and capacitive (C) loads are connected in series on a 9-level inverter. Finally, the performances of the proposed inverters are observed through MATLAB/SIMULINK simulations after the designed multilevel inverters are simulated. So, 6-level, 9-level and 11-level inverters are compared with voltages, currents and harmonic distortions. Harmonic distortions reduce with increasing level of inverter, while three multilevel inverters are investigated on different modulation indexes. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of a novel high multilevel inverter topology.
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ArticleYalnız künye2017/r/ebyu/16235
Design and application of a novel high precision and low cost electronic tachogenerator for sensor-based brushless direct current motor drivers
Ozgenel, Mehmet Cihat; Bal, Gungor; Uygun, Durmus
This study presents a precise speed control method for Brushless Direct Current (BLDC) Motors using an electronic tachogenerator (ETg) instead of an electro-mechanical tachogenerator. Most commonly used three-phase BLDC motors have three position sensors for rotor position data to provide commutation among stator windings. Aforementioned position sensors are usually Hall-effect sensors delivering binary-high and binary-low data as long as the motor rotates. These binary sets from three Hall-effect sensors can be used as an analogue rotor speed signal for closed loop applications. Each position sensor signal is apart from 120 electrical degrees. By using an electronic circuitry, a combination of position sensor signals is converted to the analogue signal providing an input to a PI speed controller. To implement this, a frequency to voltage converter has been used in this study. Then, the analogue speed signal has been evaluated as rotor speed data in comparison with the reference speed. So, an ETg system has been successfully achieved in place of an electro-mechanical tachogenerator for BLDC motor speed control. The proposed ETg has been tested under various speed conditions on an experimental setup. Employed tests and obtained results show that the proposed low-cost speed feedback sub-system can be effectively used in BLDC motor drive systems. Through the proved method and designed sub-system, a new motor controller chip with a speed feedback capability has been aimed.
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ArticleYalnız künye2017/r/ebyu/16206
Design, implementation, and application of 150-degree commutation VSI to improve speed range of sensored BLDC motor
Ozgenel, Mehmet Cihat
Permanent magnet brushless dc (BLDC) motors are very convenient for many applications such as industrial, medical, robotic, aerospace, small electric vehicles, and home applications because of their inherent satisfying dynamic characteristics. There are numerous studies about these motors and their control schemes such as sensorless control and different speed and torque control schemes. All electric motors need commutation in order to produce speed and torque. Commutation in brushed DC motors is performed by means of a brush and collector. In BLDC motors, commutation is provided electronically in contrast to the brushed dc motors. In BLDC motors, motor phase windings are energized according to the information of the rotor position by inverter transistors. Rotor position information is used for commutation. Therefore, rotor position information is required to produce speed and torque for BLDC motors. The easiest and cheapest way to obtain rotor position information is to use Hall-effect or optical sensors. BLDC motor manufacturers generally produce BLDC motors equipped with three Hall-effect position sensors. Having three position sensors on BLDC motors provides six-step commutation which ensures two phase windings are energized in each moment. The third phase is empty. In this study, all phase windings are energized in the same time. This commutation method is twelve-step or 150 degrees commutation. So that more speed can be achieved from the same BLDC motor by comparison with six-step commutation. In this paper, both six-step and twelve-step commutation methods applied to the same BLDC motor and obtained experimental results from this study were presented, examined, and discussed.
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ArticleYalnız künye2017/r/ebyu/16186
Graphene-based copper oxide thin film nanostructures as high-efficiency photocathode for p-type dye-sensitized solar cells
Kilic, Bayram; Turkdogan, Sunay; Astam, Aykut; Baran, Sümeyra Seniha; Asgin, Mansur; Cebeci, Hulya; Urk, Deniz
Graphene-based p-type dye-sensitized solar cells (p-DSSCs) have been proposed and fabricated using copper oxide urchin-like nanostructures (COUN) as photocathode with an FeS2 counter electrode (CE). COUN composed of Cu2O core sphere and CuO shell nanorods with overall diameters of 2 to 4μm were grown by a simple hydrothermal method with self-assemble nucleation. It was figured out that the formation of copper oxide core/shell structures could be adjusted by an ammonia additive leading to pH change of the precursor solution. In addition to a photocathode, we also demonstrated FeS2 thin films as an efficient CE material alternative to the conventional Pt CEs in DSSCs. FeS2 nanostructures, with diameters of 50 to 80 nm, were synthesized by a similar hydrothermal approach. FeS2 nanostructures are demonstrated to be an outstanding CE material in p-DSSCs. We report graphene/COUN as photocathode and Pt/FeS2 as CE in p-DSSCs, and results show that the synergetic combination of electrodes in each side (increased interconnectivity between COUN and graphene layer, high surface area, and high catalytic activity of FeS2) increased the power conversion efficiency from 1.56% to 3.14%. The excellent performances of COUN and FeS2 thin film in working and CEs, respectively, make them unique choices among the various photocathode and CE materials studied.
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ArticleYalnız künye2017/r/ebyu/16161
Evaluation of Waste Loquat Kernels as Substrate for Lipid Production by Rhodotorula glutinis SO28
Ortucu, Serkan; Yazici, Aysenur; Taskin, Mesut; Cebi, Kadir
This study was performed to produce lipids from the isolated oleaginous yeast Rhodotorula glutinis SO28 using loquat kernel extract (LKE) as substrate. LKE was prepared using acid hydrolysis and alkaline neutralization steps. Lipid production was performed in shaking flaks culture. Even if LKE was used as a sole source of nutritional substances, it could support cell growth and lipid synthesis in the yeast. Additional carbon, nitrogen and phosphorus sources were found to significantly alter the lipid accumulation potential of the yeast. Optimal concentrations of additional carbon (glucose) and nitrogen (ammonium sulphate) sources for lipid accumulation were determined as 15 and 0.5 g/L, respectively. On the other hand, all the concentrations of additional phosphorus source were found to significantly reduce the lipid accumulation. Optimal incubation time was determined as 132 h. Under the optimized culture conditions, the lipid concentration and lipid content of the yeast were determined as 7.82 g/L and 62 %, respectively. Fatty acid methyl ester analysis exhibited that this yeast strain could produce high proportions of C16:0 and C18 fatty acids, which are ideal for biodiesel production. This is the first report on the use of waste loquat kernels as substrate for microbial lipid production.
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ArticleYalnız künye2017/r/ebyu/16049
Synthesis, surface properties, crystal structure and dye sensitized solar cell performance of TiO2 nanotube arrays anodized under different voltages
Bozkurt Çırak, Burcu; Karadeniz, Sibel Morkoç; Kılınç, Tuba; Caglar, Bulent; Ekinci, Ali Ercan; Yelgin, Hüseyin; Kürekçi, Mehmet; Çırak, Çağrı
In this study, anodic TiO2 nanotube (TNT) arrays with average nanotube diameter from 26 nm to 115 nm and length from 1.3 μm to 6.4 μm were grown by electrochemical method. Anodization process were performed under different voltages from 10 to 50 V in ethylene glycol – ammonium fluoride – water electrolyte. Formation mechanism of TNTs was summarized. Surface morphology, crystal structure, roughness, wettability and elasticity of TNT arrays were characterized by using field emission scanning electron microscope (FESEM), X-Ray diffraction (XRD), atomic force microscope (AFM), optical tensiometer and universal mechanical tester, respectively. Water contact angle measurements and nanoindentation tests proved that water contact angle and elastic modulus of TNT arrays decrease with increasing anodization voltage. Photocurrent-photovoltage curves and electrochemical impedance spectroscopy (EIS) measurements of dye sensitized solar cells (DSSC) were made to investigate the effects of anodization voltages on photoanode performance. The light conversion efficiency and photocurrent density of TNT photoanodes was increased with increasing anodization voltage due to larger nanotube length and surface area. The results show that anodization voltage is significant parameter for the surface properties and dye sensitized solar cell (DSSC) performance TNT arrays.
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ArticleYalnız künye2017/r/ebyu/16000
Hydrogen Gas Sensing Characteristics of Nanostructured NiO Thin Films Synthesized by SILAR Method
Karaduman, Irmak; Çorlu, Tugba; Yıldırım, M. Ali; Ateş, Aytunç; Acar, Selim
Nanostructured NiO thin films have been synthesized by a facile, low-cost successive ionic layer adsorption and reaction (SILAR) method, and the effects of the film thickness on their hydrogen gas sensing properties investigated. The samples were characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD) analysis, and energy-dispersive x-ray analysis. The XRD results revealed that the crystallinity improved with increasing thickness, exhibiting polycrystalline structure. SEM studies showed that all the films covered the glass substrate well. According to optical absorption measurements, the optical bandgap decreased with increasing film thickness. The gas sensing properties of the nanostructured NiO thin films were studied as a function of operating temperature and gas concentration. The samples showed good sensing performance of H2 gas with high response. The maximum response was 75% at operating temperature of 200°C for hydrogen gas concentration of 40 ppm. These results demonstrate that nanostructured NiO thin films synthesized by the SILAR method have potential for application in hydrogen detection.
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ArticleYalnız künye2017/r/ebyu/15988
Exergoeconomic analysis and multi objective optimization of a solar based integrated energy system for hydrogen production
Khanmohammadi, S.; Heidarnejad, P.; Javani, N.; Ganjehsarabi, H.
In the current study, an integrated renewable based energy system consisting of a solar flat plate collector is employed to generate electricity while providing cooling load and hydrogen. A parametric study is carried out in order to determine the main design parameters and their effects on the objective functions of the system. The outlet temperature of generator, inlet temperature to organic Rankine cycle turbine, solar irradiation intensity (I), collector mass flow rate (m˙col) and flat plate collector area (AP) are considered as five decision variables. The results of parametric study show that the variation of collector mass flow rate between 3 kg/s and 8 kg/s has different effects on exergy efficiency and total cost rate of the system. In addition, the result shows that increment of inlet temperature to the ORC evaporator has a negative effect on cooling capacity of the system. It can lead to a decrease the cooling capacity from 44.29 kW to 22.6 kW, while the electricity generation and hydrogen production rate of the system increase. Therefore, a multi objective optimization is performed in order to introduce the optimal design conditions based on an evolutionary genetic algorithm. Optimization results show that exergy efficiency of the system can be enhanced from 1.72% to 3.2% and simultaneously the cost of the system can increase from 19.59 $/h to 22.28 $/h in optimal states.
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ArticleYalnız künye2017/r/ebyu/15982
Effect of micro combustor geometry on combustion and emission behavior of premixed hydrogen/air flames
Yilmaz, Harun; Cam, Omer; Yilmaz, Ilker
In this study, effect of micro combustor geometry on combustion and emission behavior of premixed hydrogen/air mixtures is numerically investigated. An experimentally tested micro combustor geometry is varied by establishing a cavity or a backward facing step or micro channels inside the combustor. Considering effect of combustor geometry on the amount of heat transferred through wall based on outer wall and combustor centerline temperature distributions, combustion behavior is analyzed. Emission behavior is examined by means of mixing conditions, combustion efficiency and maximum temperature value which are highly bound to geometric properties of a micro combustor. Turbulence model used in this study is Renormalization Group k-ε. For turbulence chemistry interaction, Eddy Dissipation Concept model is used. Multistep combustion reaction scheme includes 9 species and 19 steps. Numerical results obtained from this study are validated with published experimental data. Results of this study revealed that combustion in such combustors can be improved by means of quality of mixing process, residence time, combustor centerline and outer wall temperature distributions, conversion rate of input chemical energy to utilizable heat and emanated NOx levels from combustor outlet with proposed geometric variations.
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Conference ObjectYalnız künye2017/r/ebyu/15907
A soft switching single phase power factor correction AC-DC boost converter with passive snubber
Ting, Naim Suleyman; Altintas, Nihan
This paper introduces a new soft switching single phase power factor correction (PFC) boost converter with passive snubber. In the proposed converter, the main switch is turned on under zero current switching (ZCS) and turned off under zero voltage switching (ZVS) owing to the proposed passive snubber. Besides, the main diode is turned on under ZVS and turned off under ZCS. The proposed converter has features such as low cost, simple control, low number of element and high power density. Also, the output current and voltage are controlled by the proposed PFC converter in wide line and load range. The operating modes of the proposed converter are presented in detail. Also, the simulation results of converter are obtained for 1 kW and 100 kHz. It is observed that the new proposed converter has 0.99 power factor with sinusoidal current shape. So, power factor quality is fairly high.
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ArticleYalnız künye2017/r/ebyu/15832
A numerical study on combustion and emission characteristics of premixed hydrogen air flames
Cam, Omer; Yilmaz, Harun; Tangoz, Selim; Yilmaz, Ilker
Main challenges for micro power generators that utilize combustion process for energy production are inadequate residence time, destructive radical wall interactions and intensified heat loss which are mainly rooted from size limitation of such devices. To achieve high and uniform energy output, and bring in a solution to these challenges in an environment friendly manner without any kind of fundamental modification, effect of equivalence ratio on combustion and emission behavior of premixed hydrogen/air flames is numerically investigated in this study. For this purpose, an experimentally tested micro cylindrical combustor model is constructed and premixed hydrogen/air combustion in this model is simulated by varying equivalence ratio between 0.5 and 1.2 to find an optimal equivalence ratio with respect to drawbacks of micro power generators. Combustion and turbulence models implemented in this study are Eddy Dissipation Concept and Standard k-ε models, respectively. A detailed hydrogen/air reaction mechanism which consists of 9 species and 19 steps is employed to accurately gain insight into combustion process. Simulation results show that as the equivalence ratio decreases; centerline temperature distribution gets a lower value and the place where chemical reactions take place moves downstream. The most uniform temperature distribution is achieved between 0.8 and 1.0 equivalence ratios. The highest NOx formation is at 0.9 equivalence ratio and its mass fraction decreases sharply when the equivalence ratio reduces from 0.9 to 0.5.
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