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YANGAZ, MURAT UMUT

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End date: 2019 × Subject: SWIRL ×

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    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.
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    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.