Person: GÜL, MEHMET ZAFER
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GÜL
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MEHMET ZAFER
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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 Experimental investigation of granular flow through an orifice(ELSEVIER, 2008) GÜL, MEHMET ZAFER; Ahn, Hojin; Basaranoglu, Zafer; Yilmaz, Mustafa; Bugutekin, Abdulcelil; Guel, M. ZaferThe characteristics of continuous, steady granular flow through a flat-plate orifice have been experimentally investigated. In particular, the normal stress exerted on the orifice plate has been measured by the normal stress gauge which consists of a strain gauge attached to a cantilever beam. The cantilever beam supports the orifice plate which is freely hanging, and thus normal stresses on the orifice plate have been measured by strains developed in the beam due to normal forces on the plate by particles. Discharge rates of granular particles through the orifice have, therefore, been studied as a function of the average normal stress on the orifice plate. The results show that granular flows through the orifice are characterized by three regimes. When the flow is not choked, the discharge rate increases with the increasing normal stress (Regime I). With the further increase of the normal stress, the discharge rate reaches a maximum, at which the flow appears to start choking. Once the flow becomes choked, the discharge rate starts decreasing (Regime II) for further increase of the normal stress and then becomes independent of the normal stress on the orifice plate (Regime III). The transitional Regime II where the discharge rate decreases with the increasing normal stress is observed to be unstable. The asymptotic discharge rates at Regime III for various orifice sizes and particle sizes are in good agreement with results available in the literature. The maximum discharge rates, which are observed when choking just starts, exceed the asymptotic discharge rates by approximately 20-30%. (c) 2007 Elsevier B.V. All rights reserved.Publication Metadata only Optimization of the combustion chamber geometry and injection parameters on a light-duty diesel engine for emission minimization using multi-objective genetic algorithm(ELSEVIER SCI LTD, 2021) GÜL, MEHMET ZAFER; Sener, Ramazan; Gul, M. ZaferCombustion efficiency and exhaust emission of the compression-ignition engines are highly dependent on the combustion chamber design. In this study, shape optimization was performed to reduce the emissions and maximize the combustion efficiency of a compression ignition engine with the guidance of computational fluid dynamics (CFD). The aim was to optimize diesel combustion efficiency while maintaining engine power and torque. A double-swirl piston bowl is used, and the bowl depth, bowl diameter, and other dimensions of the piston bowl are optimized to minimize the soot and NOX emission while meeting the IMEP target. The spray angle of the injector, SOI, and injector protrusion were parametrized to meet the optimization targets. The numerical model was developed using Converge software. CAESES software and multi-objective genetic algorithm (MOGA) were used to automatically change the chamber design parameters and to optimize the piston bowl geometry. A total of 104 different combustion chamber designs and 23 varied injection parameters were determined parametrically and the optimum case was decided with the MOGA. A comprehensive optimization study was carried out using experimental, CFD, and MOGA methods. Compared to the baseline design, the optimized new piston bowl design has provided enhanced in-cylinder air utilization and rapid mixing-controlled combustion, resulting in enhanced fuel efficiency. The optimized design emits remarkably lower NOX and soot emissions.Publication Metadata only An experimental and numerical study of fluidized bed drying of hazelnuts(PERGAMON-ELSEVIER SCIENCE LTD, 2004) GÜL, MEHMET ZAFER; Topuz, A; Gur, M; Gul, MZThe fluidized bed drying of hazelnuts was performed and a laboratory scaled fluidized bed was constructed to obtain experimental data. A mathematical model for the simulation of simultaneous unsteady heat and mass transfer in fluidized bed drying of large particles was performed. Solution of the equation set was carried out by using Crank-Nicholson implicit method within finite volume frame work. A good agreement between the numerical and the experimental results was observed. (C) 2004 Elsevier Ltd. All rights reserved.Publication Metadata only Microwave-assisted pilot-scale biodiesel production and engine tests(ICE PUBLISHING, 2019) GÜL, MEHMET ZAFER; Demir, Veli Gokhan; Yuksel, Hayrettin; Koten, Hasan; Gul, M. Zafer; Soyhan, Hakan S.A pilot-scale microwave-assisted biodiesel reactor (60 I) was designed, manufactured and utilised to produce biodiesel from sunflower, canola and soybean oils. In addition, the engine performance and exhaust emissions of sunflower-based biodiesel and its blend with petroleum diesel (BO, B5, B10, B20 and B100) were tested using a single-cylinder, direct-injection diesel engine under constant speed and partial loads. The results carried out under microwave irradiation showed that 5 min transesterification in the presence of 1.0% potassium hydroxide and 6:1 methanolto-oil molar ratio was adequate for converting pilot scales of sunflower, canola and soybean oils to biodiesel having >95.95% ester yield, >96.5% ester content, 15-5 mm(2)/s kinematic viscosity and 0.860-0.900 g/cm(3) density values. The engine test data indicated that under experimental conditions, brake thermal efficiency, exhaust temperature and emissions of carbon monoxide and hydrocarbons were reduced with increase in concentration of biodiesel in the blend while emissions of nitrogen oxides and brake-specific fuel consumption were getting worse. As a result of this study, microwave technology could be adapted to a pilot-scale biodiesel batch reactor, and biodiesel suitable for use in diesel engines has been manufactured more efficiently and accomplished faster than conventional systems.