Browsing by Author "Koca, Kemal"

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Measurements of Flow Characterization Revealing Transition to Turbulence Associated With the Partial Flexibility-Based Flow Control at Low Reynolds Number
(Springer Heidelberg, 2025) Koca, Kemal; Keskin, Sinem; Sahin, Rumeysa; Veerasamy, Dhamotharan; Genc, Mustafa Serdar
In order to comprehend the flow characteristics of both controlled and uncontrolled SD7062 wind turbine airfoils with local flexible membrane material throughout a variety of angles of attack at a Reynolds number of 1.05 x 105, an experimental investigation was conducted. The time-dependent force measurement, the hot-wire experiment with a boundary layer and glue-on probes, and the oil-flow visualization technique were all utilized in the present study to measure the flow over the airfoil and examine the laminar-turbulent transition, laminar separation bubble, and the impact of a special flow control method that uses flexibility. A comprehensive intermittency analysis by utilizing hot-wire results was employed to obtain the flow physics effects of the local flexibility the first in the literature. The key results of the experiment demonstrated that the stall was delayed from alpha = 10 degrees to 12 degrees by the local flexibility. The hot-wire results are dedicated to laminar, transitional and turbulent regions and the transition phenomena at different locations over the suction surface of the airfoil in the analysis graphs. As demonstrated by the results of the oil-flow visualization experiment, in the uncontrolled case, the laminar separation bubble formed over the airfoil at alpha = 8 degrees between x/c = 0.16 and x/c = 0.42. The use of flexible membrane material over the airfoil provided that the oscillation of this material triggered the transition to turbulence and a bypass transition, which resulted in the reattached flow.
Citation - WoS: 18
Citation - Scopus: 19
Passive Flow Control Application Using Single and Double Vortex Generator on S809 Wind Turbine Airfoil
(MDPI, 2023) Ozden, Mustafa; Genc, Mustafa Serdar; Koca, Kemal
The current study is aimed at investigating the influences of vortex generator (VG) applications mounted to the suction and pressure surfaces of the S809 wind turbine airfoil at low Reynolds number flow conditions. Both single and double VG applications were investigated to provide technological advancement in wind turbine blades by optimizing their exact positions on the surface of the airfoil. The results of the smoke-wire experiment for the uncontrolled case reveal that a laminar separation bubble formed near the trailing edge of the suction surface, and it was moved towards the leading edge as expected when the angle of attack was increased, resulting in bubble burst and leading-edge flow separation at & alpha; = 12 & DEG;. The u/U-& INFIN;, laminar kinetic energy and total fluctuation energy contours obtained from the numerical study clearly show that both the single and double VG applications produced small eddies, and those eddies in the double VG case led the flow to be reattached at the trailing edge of the suction surface and to gain more momentum by energizing. This situation was clearly supported by the results of aerodynamic force; the double VG application caused the lift coefficient to increase, resulting in an enhancement of the aerodynamic performance. A novel finding is that the VG at the pressure surface caused the flow at the wake region to gain more energy and momentum, resulting in a reattached and steadier flow condition.
Hybrid Renewable Energy to Greener and Smarter Cities: A Case Study of Kayseri Province
(Springer Science and Business Media Deutschland GmbH, 2024) Bekçi, Eyüp; Koca, Kemal
In this study, a hybrid energy system was implemented to fulfill the electricity requirements of the trams operating in Kayseri province. The tram's annual electricity consumption data was acquired on a monthly basis from the local electricity company in Kayseri. Utilizing the obtained data, energy and cost simulations were conducted employing the Homer-Pro program. The primary objective of this investigation is to enhance sustainability while satisfying electricity demands with minimal carbon emissions. Consequently, the established hybrid energy system incorporates renewable energy sources, specifically wind, solar, and biomass energy, with the inclusion of batteries for energy storage. Furthermore, generators and converters are integrated for energy conversion purposes. The study encompasses a detailed cost analysis to identify the most economically efficient hybrid energy system, determined through optimization studies. Through this research, it is anticipated that the implementation of such a system will significantly diminish carbon emissions in Kayseri, contributing to a substantial increase in sustainability. © 2024 Elsevier B.V., All rights reserved.
Citation - WoS: 14
Citation - Scopus: 18
Convenient Site Selection of a Floating PV Power Plant in Türkiye by Using GIS-Fuzzy Analytical Hierarchy Process
(Springer Heidelberg, 2024) Karipoglu, Fatih; Koca, Kemal; Ilbahar, Esra
Floating photovoltaics (FPVs) are appearing as a promising and an alternative renewable energy opinion in which PV panels are mounted on floating platforms in order to produce electricity from renewable energy on water such as seas, dams, rivers, oceans, canals, fish farms, and reservoirs. So far, such studies related to the body knowledge on financial, technical, and environmental aspects of installation of FPV have not been performed in Turkey while expanding steadily in other countries. In this study, suitable site selection for installation of FPV power plants on three lakes in Turkey was studied by performing geographic information system (GIS) and the fuzzy analytic hierarchy process (FAHP) as multi-criteria decision-making (MCDM) method. This detailed study revealed that the criterion of global horizontal irradiance (GHI) was determined as the most crucial criterion for the installation of FPV on Beysehir Lake, Lake of Tuz, and Van Lake. Additionally, it was clearly seen that the Beysehir Lake had the highest value approximately 52% among other lakes for installation, that is why Beysehir Lake is selected as the best option for installation of an FPV system with this multi-criteria approach.
Citation - WoS: 14
Citation - Scopus: 16
Investigation of the Effect of Hidden Vortex Generator-Flap Integrated Mechanism Revealed in Low Velocities on Wind Turbine Blade Flow
(Pergamon-Elsevier Science Ltd, 2023) Ozden, Mustafa; Genc, Mustafa Serdar; Koca, Kemal
In this study, the flap and vortex generator (VG) mechanisms which were employed separately in aircraft were used as integrated first in literature. In this mechanism, the flap motion triggered and activated the VGs when it was needed at low speeds. Thus, this flap mechanism eliminated the unnecessary drag force generation when VGs were not needed. Numerical simulations which were validated with experimental data were employed in the study. In the first step, the flow characteristics formed on the S809 airfoil with 4 different flap angles ( beta = 30 degrees, 20 degrees, 10 degrees, 0 degrees) were investigated without the VG. Then, those flow structures formed on the S809 airfoil with both flap and VG were examined under the same conditions. According to the results, utilizing flap and VGs together had a positive impact at low wind speeds. Moreover, due to the flap and vortex generator integrated mechanism closed up to be not unnecessary drag formation at high wind speeds, thus those structures increased further to the positive effect with the increasing wind velocity. In terms of energy output, it was shown that this novel idea provided more energy output in this study.
Citation - WoS: 44
Citation - Scopus: 43
Nuclear Energy Consumption, Energy Access and Energy Poverty: Policy Implications for the COP27 and Environmental Sustainability
(Elsevier Sci Ltd, 2023) Bashir, Muhammad Farhan; Ma, Beiling; Sharif, Arshian; Ao, Tong; Koca, Kemal
The ever-increasing energy resource demand and subsequent environmental challenges mean that policymakers have shifted their focus to nuclear energy to address energy and environmental issues due to its unlimited potential. The current study investigates the role of nuclear energy consumption to unveil contextual information and report novel evidence concerning the significance of energy and environmental policies. This research is a novel attempt to outline methodological and topical contributions, thematic analysis, co-citation analysis, and country-collaboration analysis. As energy and environmental solutions have been prioritized within sustainable development goals, our research approach would allow policymakers and researchers to understand the extent to which nuclear energy can provide solutions towards environmental sustainability and identify research limitations to overcome by future studies. Moreover, our extensive analysis allows us to argue that nuclear energy impacts energy demand and is the most critical factor in fulfilling environmental commitments under regional and international environmental agreements.
Citation - WoS: 1
Citation - Scopus: 1
Role of Partial Flexibility on Flow Evolution and Aerodynamic Power Efficiency Over a Turbine Blade Airfoil
(MDPI, 2024) Koca, Kemal; Genc, Mustafa Serdar
In this study, the aerodynamic performance of a cambered wind turbine airfoil with a partially flexible membrane material on its suction surface was examined experimentally across various angles of attack and Reynolds numbers. It encompassed physical explanation at the pre/post-stall regions. The results of particle image velocimetry revealed that the laminar separation bubble was diminished or even suppressed when a local flexible membrane material was employed on the suction surface of the wind turbine blade close to the leading edge. The results of the deformation measurement indicated that the membrane had a range of flow modes. This showed that the distribution of aerodynamic fluctuations due to the presence of LSB-induced vortices was reduced. This also led to a narrower wake region occurring. Aerodynamic performance improved and aerodynamic vibration significantly lowered, particularly at the post-stall zone, according to the results of the aerodynamic force measurement. In addition to the lift force, the drag force was enormously reduced, corroborating and matching well with the results of PIV and deformation measurements. Consequently, significant benefits for a turbine blade were notably observed, including aerodynamic performance enhancement, increased aerodynamic power efficiency, and reduced aerodynamic vibration.
Citation - WoS: 1
GIS-AHP Approach for a Comprehensive Framework to Determine the Suitable Regions for Geothermal Power Plants in Izmir, Turkiye
(Konya Teknik Univ, 2024) Koca, Kemal; Karipoglu, Fatih; Ozturk, Emel Zeray
Geothermal energy is gaining more reputation and importance around the world. Correspondingly, suitable location selection is a critical step and has become necessary for the successful installation and operation of geothermal power plants. This study investigated suitability of & Idot;zmir region, located in the Aegean part of T & uuml;rkiye, in terms of geothermal power plants applications by using the combination of Geographical Information System and Analytic Hierarchy Process. Based on the request of power plants, thirteen important criteria were evaluated under three main categories named as physical (C1), environmental (C2) and technical (C3). Moreover, expert's opinions were taken into consideration to calculate the importance of these criteria. Key results showed that & Idot;zmir was suitable for geothermal power plants. The final suitability map layer pointed out that %8.73 (1.037 km2) of total area were determined as highly suitable regions in terms of installation. In addition, the obtained suitability map layer was compared with actual geothermal power plants. Based on the comparison study, power plants in Seferihisar were moderately suitable for geothermal power plants while the location of Bal & ccedil;ova power plant was highly suitable. Regarding the suitability assessment in the present study, the location of Dikili power plants had the least suitability score.
Citation - WoS: 21
Citation - Scopus: 22
Experimental Flow Control Investigation Over Suction Surface of Turbine Blade With Local Surface Passive Oscillation
(Pergamon-Elsevier Science Ltd, 2022) Koca, Kemal; Genc, Mustafa Serdar; Veerasamy, Dhamotharan; Ozden, Mustafa
Impact of the local flexible membrane (LFM) on aerodynamic phenomena including the formation of a laminar separation bubble (LSB) and transition to turbulence was experimentally investigated over the suction surface of a Clark-Y airfoil first time in literature. The experiments such as aerodynamic force measurement, smoke-wire flow visualization and hot-film tests were carried out at the free-stream velocity of U infinity = 3.2 m/s, U infinity = 6.4 m/s, U infinity = 9.6 m/s, U infinity = 12.8 m/s, and Reynolds number based upon on the chord length was Rec = 3.5 x 104, Rec = 7.0 x 104, Rec = 1.05 x 105 and Rec = 1.4 x 105, respectively. The experimental angle of attack was set at 0 degrees = alpha <= 20 degrees. In detailed intermittency analysis by the hot-film sensor over the uncontrolled airfoil, it was seen that the LSB and transition to turbulence formed close to the trailing edge at a lower angle of attack, and it moved towards the leading edge when increasing the angle of attack simultaneously. Employing LFM on the suction surface obviously affected the progress of these flow phenomena. In the results of smoke-wire flow visualization, either the size of the laminar separation bubble (LSB) was reduced or its presence was suppressed at lower in-cidences. The aerodynamic force measurement results also supported those behaviors. In particular, at lower incidences, the negative effects of LSB were mitigated, resulting in the presence of a more stable lift curve. Additionally, it was clearly observed that utilizing LFM ensured positive effects, especially at the pre-and the post-stall regions in terms of fewer fluctuations at the CL curve, meaning that less aerodynamic vibration and noise on wind/hydro turbine could be obtained.
Citation - WoS: 11
Citation - Scopus: 11
Biogas Intake Pressure and Port Air Swirl Optimization to Enhance the Diesel RCCI Engine Characteristics for Low Environmental Emissions
(Elsevier, 2024) Dalha, Ibrahim B.; Koca, Kemal; Said, Mior A.; Rafindadi, Aminu D.
Exhaust emission and combustion control in RCCI (reactivity-controlled compression ignition) focused mainly on the direct-injected fuel parameters, urging to investigate the advantages of port-fuel intake parameters. The engine was modified for port injection of Biogas at the valve and RCCI mode. The influence of port swirl ratio (PSR, 0 - 80%) and biogas injection pressure (BIP, 1 - 4 bar) on the diesel RCCI combustion and emissions was tested and optimized at varied loads and 1600 rpm in a port injection at the valve (PIVE) approach. Established kinetic mechanisms were combined with multi-objective optimization to further investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The results show that the radiation absorption triggered by increased CO2 lowers combustion temperature, resulting in prolonged ignition. Setting the airflow to swirl lowers the in-cylinder pressure at elevated BIP while raising the heat generated across the BIPs. Increasing the PSR slows the combustion while BIP speeds up the process. BIP and PSR show great trade-off reduction ability among all emission parameters. The optimum unburned hydrocarbon, nitrogen oxide, particulate, and carbon monoxide emissions for the injection at the valve were found to be 109.58, 0.577, and 2.336 ppm, and 0.103%, respectively, at low-load, low-BIP, and high-PSR. The emissions were lowered by 6.58, 91.26, 80.65, and 13.45% compared to the premixed RCCI mode, respectively. Therefore, introducing lowpressure biogas amid high swirling air at the valve elevates the in-cylinder condition while lowering the emissions, mitigating their environmental implications.
Citation - WoS: 7
Citation - Scopus: 9
Compensating Energy Demand of Public Transport and Yielding Green Hydrogen With Floating Photovoltaic Power Plant
(Elsevier, 2024) Koca, Kemal
The last three decades have seen a dramatic increase in the renewable energy sector as a result of increased human energy consumption and environmental concerns about fossil fuels. Offshore renewable energy sources are the most alluring and promising technologies because of more energy potential, less space, and visual restrictions than onshore ones. Among those, floating solar photovoltaic (FPV) has a remarkable reputation. The present study focuses on a viable way to replace energy resources derived from fossil fuels with renewable solar energy. In this regard, electrical energy demand is investigated where a floating photovoltaic system and integrated hydrogen production unit are employed on water surface of Yamula Dam. Energy demand of public trams would be compensated with electricity generated by FPV and rest of energy would be utilized for hydrogen production. Key results illustrated that in various scenarios, the energy generation amounts were around 31x10 6 kW, 32x10 6 kW, and 39x10 6 kW, while the energy consumption amounts were approximately 24x10 6 kW. It was evident that the energy created more than offset the amount consumed. It was also note that the total costs of entire system were $94.1 M, $78.5 M and $71.2 M according to the different cases. It was also observed that in October and November, the remaining energy from the Bozankaya tram produced the most hydrogen with 125 kg, whereas in September and October, the remaining energy from the Sirio tram produced approximately 70 kg.
Citation - WoS: 10
Citation - Scopus: 12
Investigating the Best Automatic Programming Method in Predicting the Aerodynamic Characteristics of Wind Turbine Blade
(Pergamon-Elsevier Science Ltd, 2023) Arslan, Sibel; Koca, Kemal
Automatic programming (AP) is a subfield of artificial intelligence (AI) that can automatically generate computer programs and solve complex engineering problems. This paper presents the accuracy of four different AP methods in predicting the aerodynamic coefficients and power efficiency of the AH 93-W-145 wind turbine blade at different Reynolds numbers and angles of attack. For the first time in the literature, Genetic Programming (GP) and Artificial Bee Colony Programming (ABCP) methods are used for such predictions. In addition, Airfoil Tools and JavaFoil are utilized for airfoil selection and dataset generation. The Reynolds number and angle of attack of the wind turbine airfoil are input parameters, while the coefficients CL, CD and power efficiency are output parameters. The results show that while all four methods tested in the study accurately predict the aerodynamic coefficients, Multi Gene GP (MGGP) method achieves the highest accuracy for R2Train and R2Test (R2 values in CD Train: 0.997-Test: 0.994, in CL Train: 0.991-Test: 0.990, in PE Train: 0.990-Test: 0.970). By providing the most precise model for properly predicting the aerodynamic performance of higher cambered wind turbine airfoils, this innovative and comprehensive study will close a research gap. This will make a significant contribution to the field of AI and aerodynamics research without experimental cost, labor, and additional time.
Citation - WoS: 13
Citation - Scopus: 14
Predicting the Effects of Direct-Injected Fuels Co-Powered by High-CO2 Biogas on RCCI Engine Emissions Using Kinetic Mechanisms and Multi-Objective Optimization
(Elsevier, 2024) Dalha, Ibrahim B.; Koca, Kemal; Said, Mior A.; Rafindadi, Aminu D.
High inert gas content in biogas resulted in poor burning and emissions attributes, though scarcely investigated in reactivity controlled compression ignition (RCCI). Established kinetic mechanisms were combined with multiobjective optimization to investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The work examined the impact of direct-injected high reactivity fuels (HRF) and portinjected Biogas at various inert gas (carbon dioxide, CO2) rates (25 - 45% vol), biogas fractions (40 - 70%), speeds (1600 - 2000 rpm), and loads (4.5 - 6.5 bar IMEP) on emissions of RCCI engine, experimentally. The findings revealed that while engine speeds greatly decreased CO (carbon monoxide) and NOx (nitrate oxide) emissions with rising unburned hydrocarbon (UHC) regardless of HRF employed, higher engine load significantly reduced UHC emissions. Diesel-biogas reduces NOx emissions and performs better in reducing CO and UHC emissions at lower speeds than B5-biogas, except in low-level loads. Although increasing CO2 impact led to a reduction in UHC and CO emissions, the biogas proportion was the most significant variable. The main factor influencing increased NOx emissions was engine load, which is inversely correlated with reduced NOx and increased particulate emissions owing to high CO2 content and biogas proportion. The premixed mode's optimisation outcome confirms the trade -off reduction at 5.5 bar IMEP, 35.586% CO2, and 50% fraction. As a result, running the RCCI engine with direct-injected diesel co-powered in equal proportion with high-CO2 biogas cuts the emissions trade -off dramatically, limiting the environmental repercussions of the emissions.
Flow Properties of an Ahmed Body with Different Passive Flow Control Methods
(2024) Koca, Kemal; Ozden, Mustafa
Ahmed Gövdesinin eğimli yüzeyinde ve iz bölgesinde oluşan akış topolojisini pasif akış kontrol teknikleri ile ve pasif akış kontrol teknikleri olmadan incelemek amacıyla FloEFD yazılımı kullanılarak sayısal bir simülasyon gerçekleştirilmiştir. Bu akış kontrolörlerinin akış topolojisini ve aerodinamik sürükleme katsayısını etkileyerek eğik yüzey ve iz bölgesindeki akış üzerindeki etkileri dikkatle incelenmiştir. Sayısal bulgular, sürükleme azaltımı açısından en iyi performansın, Ahmed Gövdesinin eğimli yüzeyinin arka kısmında küre ve yarı küresel şekilli akış kontrol teknikleri uygulandığında elde edildiğini açıkça ortaya koymuştur. Eğimli yüzeyin arka kısmında konumlandırılan küresel ve yarı küresel şekilli akış kontrolörleri, sırasıyla %6 ve %7 oranında sürtünme azalmasına yol açtı. Ayrıca mevcut çalışmanın sonuçları literatürde yayınlanmış çalışmalardan elde edilen sonuçlarla karşılaştırılmıştır. Farklı yazılımlarla bulunsalar da birbirleriyle tutarlı oldukları açıkça görüldü.
Citation - WoS: 9
Citation - Scopus: 11
Design Analysis of a Wave Energy Converter for Hydrogen Generation Near Shoreline of Black Sea
(Elsevier, 2024) Bekci, Eyuep; Koca, Kemal; Bashir, Muhammad Farhan
The generation of electricity from waves has attracted a lot of attention from researchers lately. Despite the vastness and accessibility of wave energy across the majority of the planet, there is a dearth of literature on the production of electricity and hydrogen from wave power. In this paper, a comprehensive simulation related to hydrogen production with an oscillating wave surge converter (OWSC) system was employed for the Black Sea region. The simulations were performed by means of Homer-Pro software and the data were provided thanks to European Marine Observation and Data Network (EMODnet) as well as a novel web-based tool with regards to wave resources. Initial results of web-based tool showed that the hydrogen generation was directly impacted by considerable wave height and wave energy period. As a result, it may change based on the days and months. May had the lowest monthly energy production (3 MWh), while December had the highest monthly energy production (27 MWh). Moreover, the electrolyzers with different efficiencies were investigated with Homer-Pro. The electrolyzer with an efficiency of 85% at 100 kW produced 3301 kg annually, whereas the electrolyzers with 90% and 95% efficiency at 100 kW produced 3419 kg annually and 3422 kg annually, respectively. Apart from those findings, when more efficient electrolyzers were employed in the system, both the capital and replacement costs dropped at the same time.