Person: YANGAZ, MURAT UMUT
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YANGAZ
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MURAT UMUT
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Publication Metadata only Effects of injection strategy and combustion chamber modification on a single-cylinder diesel engine(ELSEVIER SCI LTD, 2020) GÜL, MEHMET ZAFER; Sener, Ramazan; Yangaz, Murat Umut; Gul, Mehmet ZaferThe diesel engine is widely used due to its thermal efficiency, reliability and fuel economy, while diesel engine emissions are harmful to the environment and human health. Therefore, the standards (EPA, Tier, NRE-v/c standards, etc.) limit the exhaust emission of engines around the world. The most successful method of reducing emissions is to optimize the combustion chamber and the fluid motion inside the engine. In this study, experimental and numerical methods were used in a diesel engine to analyze fluid motion, spray, combustion process, and exhaust emissions. A new type of swirl piston bowls and a reentrant piston bowl were utilized on a baseline diesel engine. Different spray angles and injection pressures were applied and results were compared with the baseline design. Results show that the piston bowl shape has a critical influence on engine performance and emissions. Since the multi-swirl piston bowl (MSB) and double-swirl piston bowl (DSB) design increases in-cylinder swirl and turbulence, it contributes to reducing emissions and improving the combustion process. Increasing spray angle and injection pressure and using of DSB can reduce the soot emissions by 81%. DSB and MSB improve the combustion process but also increase NOx emissions due to increased in-cylinder temperature. On the other hand, NOx emissions may also be reduced if the injection parameters of the engine are optimized to provide the same power with the new swirl bowls.Publication Metadata only Influence of piston bowl geometry on combustion and emission characteristics(SAGE PUBLICATIONS LTD, 2019) ÖZDEMİR, MEHMED RAFET; Sener, Ramazan; Ozdemir, Mehmed R.; Yangaz, Murat U.Together with the global energy concerns, the norms are getting stringent to prevent the emission threat. There are on-going studies on systems working with both fossil and renewable energy sources aiming to create more efficient and less emissive processes and devices. Accordingly, a set of numerical simulations was performed to examine the effect of the bowl shape of a piston on the performance behaviour, emission rates and combustion characteristics in a four-cylinder, four strokes, water-cooled compression ignition engine using n-heptane (C7H16) as fuel. Six different piston bowl geometries, five from the literature and proposed one, were utilized having different length-to-diameter ratio, curvature and sidewall radius. The study was conducted at 1750 r/min engine speed and a constant compression ratio with a full performance condition. The intake and exhaust valves have been considered as closed during the analysis to provide the variation of crank angle from 300 CA to 495 CA. The results showed that the piston bowl geometry has a significant impact on the rate of heat release, in-cylinder pressure, in-cylinder temperature, and emission trends in the engine. Among the piston bowl geometries studied, design DE and design DF exhibited better combustion characteristics and relatively lower emission trends compared to other designs. The observed rate of heat release, in-cylinder pressure and in-cylinder temperature magnitudes of these two geometries was higher in comparison to other geometries. Moreover, the trade-off for NOx emission was also observed higher for these piston bowl designs.Publication Metadata only Energy, Exergy and Exergo-Economic Characteristics of Hydrogen Enriched Hydrocarbon-Based Fuels in a Premixed Burner(TAYLOR & FRANCIS INC, 2021) YILMAZ, İLKER TURGUT; Ozdemir, Mehmed Rafet; Yangaz, Murat Umut; Yilmaz, Ilker TurgutThe enrichment of conventional fuels by hydrogen is quite popular owing to positive environmental aspects compared to the main fuel. In most of the studies, the entropy analysis was not examined in detail. In this research, exergy (second law) analysis of hydrogen-enriched methane, natural gas, propane, LPG, and biogas were analyzed using the numerical model in a premixed burner due to their wide usage in the industry as well as in the household appliances. In the numerical model, the discrete ordinates radiation and Realizable k- epsilon turbulence models were coupled with the premixed combustion model. The rate of increase for hydrogen of each fuel is considered as 10%. The premixed burner exhibited better performance in terms of energy and exergy with the rise of hydrogen enrichment. The most improvement was observed at biogas tests. The results showed that the chemical composition of the base fuel is a significant parameter that affects the exergy and energy capability of the burner due to chain reactions of radicals in the base fuel with hydrogen. It can be concluded that the hydrogen enrichment of biogas in premixed burners is promising in comparison with other tested fuels from both energy and exergy perspective.Publication Open Access Effect of air pressure on nanofiber production in solution blowing method(GAZI UNIV, FAC ENGINEERING ARCHITECTURE, 2020-07-21) EKİCİ, BÜLENT; Polat, Yusuf; Yangaz, Murat Umut; Calisir, Mehmet Durmus; Gul, Mehmet Zafer; Demir, Ali; Ekici, Bulent; Kilic, AliIn this study, effect of air pressure on nanofiber diameter and morphology was studied for solution blowing technique. A computational fluid dynamics (CFD) analysis was realized via ANSYS (R) Fluent software, and the results were compared with experimental solutions. The results showed that an increase in air inlet pressure from 100 kPa to 300 kPa has significant effect on nanofiber diameter and morphology. In contrast, as the air inlet pressure increases above 300 kPa to 600 kPa, both nanofiber diameter increases, and the fiber agglomerations are observed due to high turbulence intensity. The droplets were observed at 100 kPa air inlet pressure due to low driving force applied to the polymer solution. The effects of air pressure on nanofiber diameter and morphology have been investigated by using finite volume method, and the results are compared with the experimental results.Publication Open Access Comparison of Conventional and Modified Burners in Performance with Different Fuels using a Linear and a Non-linear Eddy-viscosity Turbulence Model(ISFAHAN UNIV TECHNOLOGY, 2019-11-01) ÇİFTÇİOĞLU, GÖKÇEN ALEV; Yangaz, M. U.; Ciftcioglu, G. A.; Kadirgan, M. A. N.Energy sources must be used efficiently to provide the sufficient amount of energy for the still-growing population in the world, already threatened by the effects of global warming. The significant increase in the use of natural resources causes serious problems due to its unsustainable situation. Therefore, exhaust gases/emissions must be reduced to prevent more damage on the environment. This study aims to provide solutions for a sustainable ecosystem by lowering emissions such as CO, unburnt HC, NOx, and enhancing the combustion efficiency in a certain type/scale industrial burner. In that way, some geometric modifications (on furnace design and the connected burner) have been applied on the conventional type burners to benefit the effects of preheating of combustion air. Modified geometries have been analyzed numerically and compared with the conventional design's results. Moreover, the comparison between a linear and non-linear turbulence model has been given in terms of simulation results. Major findings indicate that Burner-1 has significantly lower emissions compared to the others. Preheating effect coupled with the flue gas recirculation (FGR) seems to work well in terms of performance and emissions. Also, a significant difference between linear and non-linear turbulence model appeared on the emission characteristics for the same simulations.Publication Metadata only Combustion performance of hydrogen-enriched fuels in a premixed burner(TAYLOR & FRANCIS LTD, 2020) ÖZDEMİR, MEHMED RAFET; Yangaz, Murat Umut; Ozdemir, Mehmed Rafet; Sener, RamazanPremixed burners have been widely used in many applications for both industrial and household appliances. For this reason, it is very important to enhance the combustion and emission efficiency of premixed burners because of their strong position in the global dimension. On the other hand, the addition of hydrogen to various fuels has been a research topic in the last decade due to its environmental and economic positive effects. In this study, the effect of hydrogen addition to different gaseous fuels at different rates has been investigated in a premixed burner. A numerical parametric study has been carried out using a commercial CFD code. The gaseous fuels namely; methane, propane, LPG and natural gas have been enriched by different hydrogen addition rates with a 10% increment. Moreover, the results of pure hydrogen have been presented. The results reveal that the combustion efficiency for all fuels has been affected positively with hydrogen enrichment except for certain gas compositions. Furthermore, this study has shown that the hydrogen addition in general, decreases the unburnt HC and CO emissions.Publication Open Access Farklı Uygulama ve Tasarımların Bir Gaz Yakıcıdakı Emisyonların Düşürülmesine Etkileri(2018-09-30) ÇİFTÇİOĞLU, GÖKÇEN ALEV; MURAT UMUT YANGAZ;GÖKÇEN ALEV ÇİFTÇİOĞLU;Mehmet Arif Neşet KADIRGANVerimsiz enerji kullanımı, kaynakların hızla tükenmesinin ve aynı zamanda tam yanmanın gerçekleşmediğine işaret edebilecek, yüksek orandaki emisyonlara bağlı küresel ısınmanın ana nedenlerinden biridir. Genel olarak, toplu sistemler ya da büyük ölçekli sistemler yukarda belirtilen problemlerin en büyük pay sahibidirler. Endüstriyel yakıcılar metal şekillendirme sanayisinde ve büyük ölçekli elektrik üretim süreçlerinde yaygın bir şekilde kullanılmaktadır. Bu alanlarda, hem karbon hem de azot bazlı emisyonlar için katı kurallar vardır. Buradan yola çıkarak, bu çalışma, çevresel kirleticilerin minimize edilmesi için oksi-yakıt yanması, yanmış gazların iç devirdaimi ya da ön karışımlama gibi konsept ve tasarımları içeren farklı teknikler kullanarak, yanma verimi ve emisyon düşüşü açısından iyileştirme sağlamayı amaçlamaktadır. Bütün sonuçlar birbiriyle karşılaştırılmış ve birçok parametreyi içeren tablolar ile sıcaklık konturları şeklinde verilmiştir. Bazı konseptlerin diğerlerinden performans ve emisyonlar açısından daha etkin olduğu gösterilmiştir.Publication Open Access A Two-Time-Scale Turbulence Model and Its Application in Free Shear Flows(2024-02-01) GÜL, MEHMET ZAFER; YANGAZ, MURAT UMUT; GÜL M. Z., YANGAZ M. U., Sen S.A novel three-equation turbulence model has been proposed as a potential solution to overcome some of the issues related to the k–ε models of turbulence. A number of turbulence models found in the literature designed for compressed turbulence within internal combustion engine cylinders tend to exhibit limitations when applied to turbulent shear flows, such as those occurring through intake or exhaust valves of the engine. In the event that the flow is out of equilibrium where Pk deviates from ε, the turbulence models require a separate turbulence time-scale determiner along with the dissipation, ε. In the current research, this is accomplished by resolving an additional equation that accounts for turbulence time scale, τ. After presenting the rationale behind the model, its application to three types of free shear flows were given. It has been shown that the three-equation k–ε–τ model outperforms the standard k–ε model as well as a number of two-equation models in these flows. Initially, the k–ε–τ model handles the issue of the plane jet/round jet anomaly in an effective manner. Secondly, it outperforms the two-equation models in predicting the flow behavior in the case of plane wake, one that is distinguished by its weak shear form.