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GÜL, MEHMET ZAFER

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MEHMET ZAFER

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Subject: Combustion ×

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Now showing 1 - 3 of 3
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    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 Zafer
    The 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.
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    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. Zafer
    Combustion 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.
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    PublicationOpen Access
    Zero-dimensional modelling of a four-cylinder turbocharged diesel engine with variable compression ratio and its effects on emissions
    (SPRINGER INTERNATIONAL PUBLISHING AG, 2019-10) GÜL, MEHMET ZAFER; Khan, Daniyal; Gul, M. Zafer
    With emission legislation becoming ever more stringent, declining fossil resources and an increase in greenhouse effect caused by CO2 emissions, manufacturers are exploring new ways to match the emissions regulations without compromising on the performance of the engine. This study included development of zero-dimensional model of a 2.0 L turbocharged diesel engine and then study the effects of changing its compression ratio in the numerical model. This paper gave a framework in determining the effect of compression ratios in different operational conditions of the engine. Implementation of variable compression ratio technology on a numerical model proved to be very cost-effective, time saving and validated the fact that numerical models can be used to study different parameters of the engines during the development stage. The main effect of an increase in compression ratio, was found to be as expected, a decrease in brake specific fuel consumption and an increase in thermal efficiency with a greater impact at low rpm-low load regions. Assuming, that the variable compression ratio technology can be utilized in the engine, this work found the best combination of compression ratios around the engine map, giving a best fit of trade-offs between the emissions and performance of the engine. This study also validates the fact that variable compression ratio technology, if implemented in the engine could not only reduce emissions of the engine but can be given as an option to the end-user to switch to more economic fuel consumption values during idling or cruising at long distant journeys.