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GÜL, MEHMET ZAFER

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MEHMET ZAFER

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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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    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.