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 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 Open Access ADVANCED NUMERICAL AND EXPERIMENTAL STUDIES ON CI ENGINE EMISSIONS(YILDIZ TECHNICAL UNIV, 2018-06-14) GÜL, MEHMET ZAFER; Gul, M. Z.; Koten, H.; Yilmaz, M.; Savci, I. H.In these studies, three important works examined to get ultra-low emission for a single cylinder diesel engine. The first study was performed for single fuel and compression ratio (CR), intake and exhaust valve timings, mass flow rate were optimized for a range of engine speed. Then for the same engine injection parameters such as start of injection (SOI), injector cone angle, and split injection structures were examined to get optimum parameters for the diesel engine. In CR studies, different combustion chambers were tested according to injector cone angles and fuel-wall interaction. In the second study, in addition to the above studies, dual fuel compressed biogas (CBG) and diesel combustion were analyzed under different engine loads both experimentally and computationally. Optimized single fuel diesel cases were compared with CBG + Diesel dual fuel cases which employed port injection for CBG fuel. In dual fuel engine applications, CBG fuel and air mixture is induced from intake port and this air-fuel mixture is ignited by pilot diesel fuel near top dead center (TDC). In dual fuel engine mode, exhaust emissions reduced considerably especially in NOx and particulate matter (PM) because of methane (CH4) rate and optimized engine parameters. The third study is focused on aftertreatment systems to minimize residual exhaust emissions. The emissions of the diesel engines consist of various harmful exhaust gases such as carbon monoxide (CO), particulate matter (PM), hydrocarbon (HC), and nitrogen oxides (NOx). Several technologies have been developed to reduce diesel emissions especially NOx reduction systems in last decades. The most promising NOx emission reduction technologies are exhaust gas recirculation (EGR) system to reduce peak cylinder temperature that reduces NOx form caused by combustion and active selective catalyst reduction (SCR) system using reducing agent such as urea-water-solution for exhaust aftertreatment system. In this study, computational fluid dynamic (CFD) methodology was developed with conjugate heat transfer, spray, deposit and chemical reaction modeling then emission prediction tool was developed based on the CFD results with deposit prediction mechanism. CFD and deposit results were correlated with image processing tool in flow test bench.