Yazar "Yilmaz, Emre" seçeneğine göre listele

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    An Experimental Research on the Effects of Negative Valve Overlap on Performance and Operating Range in a Homogeneous Charge Compression Ignition Engine With RON40 and RON60 Fuels
    (Asme, 2020) Polat, Seyfi; Solmaz, Hamit; Uyumaz, Ahmet; Calam, Alper; Yilmaz, Emre; Yucesu, H. Serdar
    In this study, the effects of negative valve overlap (NVO) on homogenous charge compression ignition (HCCI) combustion and engine performance were experimentally investigated. A four stroke, single cylinder, port injection HCCI engine was operated at -16 deg crank angle (CA), -8 deg CA, and +8 deg CA valve overlap values and different lambda values and engine speeds at wide open throttle. RON40 and RON60 were used as test fuels in view of combustion and performance characteristics in HCCI mode. The variations of indicated mean effective pressure (IMEP), residual gas, CA50, indicated thermal efficiency (ITE), indicated specific fuel consumption (ISFC), maximum pressure rise rate (MPRR) and ringing intensity (RI) were observed on HCCI combustion. The results showed that NVO caused to trap residual gases in the combustion chamber. Hot residual gases showed heating and dilution effect on HCCI combustion. Combustion was retarded with the presence of residual gas at -16 deg CA NVO. Test results showed that higher imep and maximum in-cylinder pressure were obtained with RON60 according to RON40. As expected, CA50 was obtained later with RON60 compared to RON40 due to more resistance of auto-ignition. RON60 residual gas prevented the rapid and sudden combustion due to higher heat capacity of charge mixture. RI decreased with the usage of RON60 compared to RON40. Significant decrease was seen on RI with RON60 especially at lower lambda values. It was seen that HCCI combustion can be controlled with NVO and operating range of HCCI engines can be extended.
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    Effects of intake air temperature on combustion, performance and emission characteristics of a HCCI engine fueled with the blends of 20% n-heptane and 80% isooctane fuels
    (Elsevier, 2015) Cinar, Can; Uyumaz, Ahmet; Solmaz, Hamit; Sahin, Fatih; Polat, Seyfi; Yilmaz, Emre
    In this study, the effects of intake air temperature on the cylinder pressure, heat release rate, start of combustion, combustion duration, engine performance and exhaust emissions were investigated in a HCCI gasoline engine fueled with the blends of 20% n-heptane and 80% isooctane fuels. Intake air temperature was changed from 40 degrees C to 120 degrees C. The experiments were performed with a single-cylinder, four-stroke HCCI gasoline engine at two different excessive air coefficients at 1200 rpm. The results showed that in-cylinder pressure and heat release rate increased with the increase of intake air temperature. The increase of intake air temperature caused combustion to advance and the combustion duration to decrease. At 70 degrees C intake air temperature, brake torque decreased by 3.1% when the engine operated with lambda = 0.6 compared to lambda = 0.7. The specific fuel consumption and NO emissions tend to increase at higher intake air temperatures of 100 degrees C and 120 degrees C. It was also found that CO and HC emissions firstly increased and then started to decrease after the 90 degrees C intake air temperature. (C) 2014 Elsevier B.V. All rights reserved.
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    Estimation of the COVIMEP Variation in a HCCI Engine
    (Gazi Univ, 2020) Polat, Seyfi; Solmaz, Hamit; Calam, Alper; Yilmaz, Emre
    In this study, variation of the COVIMEP was tried to be predicted by using the artificial neural network method for 4-stroke, 4-cylinder, direct injection and supercharged HCCI engine experimental data obtained by using n-heptane fuel at 60 degrees C intake air temperature, 1000 rpm engine speed at different inlet air intake pressure. Intake air inlet pressure and lambda were used as input data in artificial neural network model. The COVIMEP value was used as the target. Three layers and five neurons were used to construct the network using the Levenberg-Marquardt algorithm. Correlation between targets and outputs for teaching, accuracy and testing were obtained as 0.97989, 0.9504 and 0.91644, respectively. Total correlation factor was found as 0.96983. As a result of the study, it was seen that the stored data and the estimated COVIMEP data were compatible.
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    Experimental examination of the effects of military aviation fuel JP-8 and biodiesel fuel blends on the engine performance, exhaust emissions and combustion in a direct injection engine
    (Elsevier Science Bv, 2014) Uyumaz, Ahmet; Solmaz, Hamit; Yilmaz, Emre; Yamik, Hasan; Polat, Seyfi
    Biodiesels are the most popular fuels which can be used as an alternative fuel instead of diesel fuel in diesel engines. Low emission characteristics and high cetane numbers are the most significant advantages of biodiesels. However, JP-8 military aviation fuel which is a kerosene based fuel has a low viscosity, high lower heating value and very low freezing point. The usage of the fuel blends of biodiesel and JP-8 may be effective in improving the characteristics of biodiesel. In this study, JP-8 aviation fuel and sunflower methyl ester blends were tested at 7.5, 1125, 15 and 18.75 Nm engine loads and at maximum torque speed (2200 min(-1)) in a single cylinder, naturally aspirated, and direct injection diesel engine. In-cylinder pressure, ignition delay period, engine performance and exhaust emissions have been examined. As the engine load increases the specific fuel consumptions decrease for all test fuels. It was seen that NOx emissions increased with the increase of the amount of biodiesel in the test fuels. CO emissions decreased as the amount of biodiesel fuel increased in the test fuels. Consequently, it was observed that JP-8 and biodiesel fuel mixtures can easily and efficiently be used in diesel engine. (C) 2014 Elsevier B.V. All rights reserved.
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    Thermodynamic comparison of crank-drive and rhombic-drive mechanisms for a single cylinder spark ignition engine
    (Gazi Univ, Fac Engineering Architecture, 2020) Yilmaz, Emre; Polat, Seyfi; Solmaz, Hamit; Aksoy, Fatih; Cinar, Can
    In internal combustion engines, power is taken from a shaft and motor movement is defined by the angular motion of this shaft. This movement refers to the angle of the gear in rhombic drive mechanism engines while taking the name of the crank angle in crankshaft engines. In this study, thermodynamic comparison was performed in a single cylinder, four-stroke spark ignition engine with crank-drive and alternative rhombic drive mechanisms. Maximum cylinder pressure was obtained at 371 degrees for both rhombic drive and crank mechanism. The maximum cylinder pressure of the crank mechanism is 63.1 bar while the maximum cylinder pressure of the rhombic drive mechanism is 64.5 bar. While in the rhombic drive mechanism engine, the amount of heat lost from the cylinder wall is 15.27 J in one cycle, this value is calculated as 13.68 J with a crank mechanism for a cycle.