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Öğe Development of a variable-profile cam to enhance the volumetric efficiency of IC engines(INDERSCIENCE ENTERPRISES LTD, 2017) Sürmen, Ali; Arslan, Ridvan; Kopmaz, Osman; Avci, Atakan; Karagoz, Irfan; Karamangil, M. IhsanIn this study, it is aimed to develop a new concept camshaft for continuously variable valve timing (CVVT). The concept is based on obtaining a curvilinear cam surface by integrating a number of conventional cam contours. Thirteen unworked camshafts, with arbitrary different contours, i. e., valve opening and closing times, were machined and tested on a fourstroke single-cylinder diesel engine to determine their volumetric efficiency at varied engine speeds. Then with suitable axial arrangement of these individual contours on a camshaft and integration of them, a single curvilinear cam surface was obtained. It is expected to get the same volumetric efficiency, with a ball contact follower when it follows a specific contour, as obtained when the specific cam of the same contour individually yielded. By giving an axial motion to the camshaft, allowing the follower to follow different contours, continuous variation of valve timing will be achieved.Öğe Enhancing the heavy load performance of a gasoline engine converted for LPG use by modifying the ignition timings(PERGAMON-ELSEVIER SCIENCE LTD, 2015) Erkus, Baris; Karamangil, M. Ihsan; Sürmen, AliThis paper presents the results of the experiments conducted on a spark-ignition (SI) engine fuelled with liquefied petroleum gas (LPG) by varying the ignition timing at the excess air coefficients of 1.0 and 1.3. Experiments were carried out at wide open throttle (WOT) position and at engine speed of 4300 rpm aiming to determine the lean operation performance of an engine when fuelled with LPG at full load. Performance parameters, namely brake power, brake-specific fuel consumption (BSFC), brake thermal efficiency and exhaust emissions such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx), were studied. It was shown that advancing the ignition timing improved the performance of LPG-fuelled SI engine for excess air coefficients higher than 0.8. The highest brake power and the lowest BSFC were obtained with modified ignition timing at an excess air coefficient of 1.0. The lowest exhaust emissions were obtained with an excess air coefficient of 1.3. In general, advancing the ignition timings caused increase in HC and NO emissions, while the effect of ignition timing on CO emissions was negligible.Öğe Experimental investigation of the effect of E85 on engine performance and emissions under various ignition timings(Elsevier Ltd, 2014) Türköz, Necati; Erkuş, Bariş; Karamangil, M. Ihsan; Sürmen, Ali; Arslanoǧlu, NurullahIn this study, we experimentally investigated the best ignition timing in an SI engine using an E85 ethanol blend by altering the timing angle with respect to gasoline use regarding the output performance parameters such as power and efficiency. We also determined the energy distribution of the engine. The experiments were carried out on a 4-stroke, 4-cylinder spark ignition engine, and the excess air coefficients were almost all maintained at approximately unity. To achieve this, the fuel orifice holes of the carburettor were suitably enlarged for the E85 ethanol blend. The ignition timing was successively delayed in 2° increments up to 6° (denoted as -2, -4, -6, respectively) and then successively advanced by 2° up to 6° (denoted as +2, +4, +6, respectively) with respect to the advance values used with gasoline (called the "original advance values") at full load operation. The best performance and emissions were obtained with +4. Advanced ignition timing resulted in an increase in NOx emissions, while CO and CO2 remained relatively unaffected. Increasing the delay in ignition timing caused poorer combustion and hence more HC emissions and fuel consumption.Öğe MATHEMATICAL MODELING OF HC EMISSIONS RELEASED by OIL FILM for GASOLINE and GASEOUS FUELS(Gazi Universitesi, 2014) Karamangil, M. Ihsan; Yenice, Seckin; Kaynakli, Omer; Sürmen, AliOil film on cylinder liner has been suggested as a major source of engine-out hydrocarbon emissions. In this study, a mathematical modeling for the rate of absorption/desorption of the fuel in the oil film has been developed for gasoline, LPG and methane. It was seen that the absorption/desorption mechanism of LPG and methane into the oil film were lower than gasoline. It was determined that the most dominant parameter of this difference was Henry's constant, which was related to solubility. As interaction time of oil film-fuel vapor was longer at low engine speeds, the quantities of HC absorbed/desorbed increased. The quantities of HC absorbed/desorbed increased with increasing inlet pressure and compression ratio.Öğe Mathematical modeling of hydrocarbon emissions from oil film for different fuels(Elsevier, 2014) Karamangil, M. Ihsan; Sürmen, Ali; Yenice, SeckinOil film on the inner surface of the cylinder liner is one of the major sources of the vehicle-out HC emissions as fuel vapor is absorbed by the oil film under high pressure and then released after late expansion stroke when the pressure is low. This process is extensively affected by type of the fuel and lubricating oil. In this theoretical study, the effect of different engine parameters on oil film HC emissions for various fuels, such as iso-octane, methanol, ethanol, LPG and methane, is investigated. The results show that fewer HCs are released from the oil film when using gaseous fuels, such as LPG and methane, than when using liquid fuels. The fuels can be ranked according to their effect (from greatest to least) on HC emissions as follows: iso-octane, methanol, ethanol, LPG and methane. The most important parameters affecting the HC absorption/release mechanism are found to be Henry's coefficient and the diffusion coefficient. As interaction time of oil film-fuel vapor was longer at low engine speeds, the quantities of HC absorbed/desorbed increased. The quantities of HC absorbed/desorbed increased with increasing inlet pressure and compression ratio.
