Person: TEKİN, MERVE
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TEKİN
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MERVE
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Publication Forming evolution of titanium grade2 sheets(Walter De Gruyter Gmbh, 2022-01-27) Tekin, Merve; ERTAN, RUKİYE; TEKİN, MERVE; Ertan, Rukiye; GÜLER ÖZGÜL, HANDE; Özgül, Hande Güler; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-2831-3175; KIH-2391-2024; GWU-9651-2022; AAG-8571-2021Titanium and its alloys take attention, especially in aerospace, automotive, and biomedical applications because of their strength, corrosion resistance, and biocompatibility. Titanium components, in general, are produced by sheet metal forming. However, the springback effect is a critical problem in the forming process due to difficult formability of titanium sheets. In the present study, the hot forming process was applied to sheets to investigate the effect of deformation temperature on microstructure, mechanical properties, and springback behavior of commercially pure grade 2 titanium sheets. The springback angles were measured at the CAD model after the sheets were scanned by the 3D scanner. The tensile test, hardness measurements, and microstructural analysis were examined by using specimens that were cut from the sidewall and the bottom of the deformed sheet as U-profile. The results reveal that the microstructure is substantially changed, and the springback is reduced with increasing temperature; thus, optimum results were obtained compared to the data obtained at room temperature.Publication Electronic driver design of a piezo-actuated valve mechanism for continuously variable valve timing(Ieee, 2019-01-01) Dirim, B.; Sürmen, A.; Karamangil, M. I.; Avcı, A.; İkli, F. I.; Tekin, M.; Türköz, N.; Dirim, Bayazit; SÜRMEN, ALİ; KARAMANGİL, MEHMET İHSAN; AVCI, AYFER; TEKİN, MERVE; Türköz, N.; IŞIKLI, FIRAT; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-1662-5649; 0000-0003-2831-3175; 0000-0002-9009-8069; AAH-8619-2019; KFR-7212-2024; JCN-8081-2023; AAG-8571-2021; HNS-2001-2023; EBD-3489-2022; EJZ-3309-2022Volumetric efficiency is the main parameter that characterizes the increase in power of an engine at the same speed. A group of design parameters that affects the volumetric efficiency are opening-closing characteristics of the valves (opening and closing times, valve lift and shape of cam lobe). But the same values of these parameters in various speeds yield different volumetric values which make the problem much more difficult. The solution is to develop techniques that change these parameters with changing engine speed. The most ideal one is to achieve this variation continuously together with speed variation which is called continuously variable valve timing (CVVT). To achieve this goal piezo actuator driven hydraulic displacement magnifier has been used. To drive the piezo actuator an electronic control unit and high voltage power amplifier designed and then fully digital solution is developed and explained in this study.Publication Development and comparative analysis of a pure fuel cell configuration for a light commercial vehicle(Springer, 2022-11-07) Tekin, Merve; Karamangil, Mehmet İhsan; TEKİN, MERVE; KARAMANGİL, MEHMET İHSAN; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-2831-3175; AAG-8571-2021; AAH-8619-2019Fuel cell electric vehicles help hybrid and battery electric vehicles to reduce vehicle emissions. Fuel cells are more appealing since, like internal combustion engines, they provide energy as long as fuel is supplied while doing so with less energy conversion and little or no emissions. In this study, the energy and fuel consumption values of a vehicle's internal combustion engine and fuel cell configurations were compared on a tank-to-wheel basis. First of all, a fuel consumption model was created for the conventional vehicle with 1.3 diesel engine. Subsequently, the fuel cell configuration of the same vehicle was designed by selecting a suitable fuel cell, electric motor, battery, and transmission. Then, the fuel cell vehicle configuration's hydrogen and energy consumptions were calculated. The equivalent diesel consumption of the fuel cell vehicle was determined to be 3.38 L/100 km at the end of the study, which is 32% better than an Internal Combustion Engine vehicle. Also, with theoretical regenerative braking in the fuel cell electric vehicle, consumed traction energy can be reduced by 27%, while with practical regenerative braking, 55% of the braking energy can be recovered, and the traction energy can be reduced by 15%. On the other hand, since there is no regenerative braking system in the conventional vehicle, all of the braking energy is lost as heat.Publication Investigation of the contribution of deceleration fuel cut-off and start/Stop technologies to fuel economy by considering new european driving cycle(Sage Publications, 2022-01-06) Tekin, Merve; Karamangil, Mehmet İhsan; TEKİN, MERVE; KARAMANGİL, MEHMET İHSAN; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-2831-3175; AAH-8619-2019; AAG-8571-2021Greenhouse gas (GHG) emissions released into the atmosphere cause climate change and air pollution. One of the main causes of GHG emissions is the transportation sector. The use of fossil fuels in internal combustion engine vehicles leads to the release of these harmful gases. For this reason, since 1992, several standards have been introduced to limit emissions from vehicles. Technologies such as reducing engine sizes, advanced compression-ignition or start/stop, and fuel cut-off have been developed to reduce fuel consumption and emissions. In this study, the contribution of deceleration fuel cut-off and start/stop technologies to fuel economy has been examined considering the New European Driving Cycle. Therefore, the fuel consumption values were calculated by creating a longitudinal vehicle model for a light commercial vehicle with a diesel engine. At the end of the study, by using the two strategies together, fuel economies of 17.5% in the urban driving cycle, 3.7% in the extra-urban cycle, and 10% in total were achieved. CO2 emissions decreased in parallel with fuel consumption, by 10.1% in total.Publication Comparison of fuel consumption and recoverable energy according to nedc and wltp cycles of a vehicle(Ecopetrol Sa, 2022-12-01) Karamangil, M-İhsan.; KARAMANGİL, MEHMET İHSAN; Tekin, Merve; TEKİN, MERVE; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0003-2831-3175; AAG-8571-2021Since 1997, the NEDC (New European Driving Cycle) has been used to measure CO2 emissions. However, because this cycle is unable to accurately replicate real-world driving conditions, a new procedure has been developed. The WLTP (Worldwide Harmonised Light Vehicles Test Procedure), which is 10 minutes longer and more dynamic than NEDC, has been used since late 2017. In this paper, fuel consumption, CO2 emissions, and energy demand of these two cycles are compared. The vehicle mathematical model was created in a MATLAB program using vehicle longitudinal motion equations for a light commercial vehicle with a diesel engine. The speed profiles of the commonly used NEDC and WLTP cycles were defined in the model, and the fuel consumption, CO2 emission values, and the total energy values required for each cycle were calculated. Furthermore, the recoverable energy potential of the cycle has been revealed. According to the WLTP cycle, the vehicle's fuel consumption and CO2 emission values were calculated at approximately 11% more than the NEDC cycle. The recoverable energy potential is 2.64 times higher in the WLTP cycle compared to the NEDC cycle. Thus, for vehicle designers, it is a very useful tool that can calculate the fuel and CO2 consumption of a vehicle in 100 km according to certain cycles, based on vehicle parameters.Publication Experimental analysis of the volumetric and thermal efficiency performance of a novel direct piezo-acting cvvt mechanism(Taylor & Francis Inc, 2023-06-22) Sürmen, Ali; SÜRMEN, ALİ; Karamangil, M., I; KARAMANGİL, MEHMET İHSAN; Avcı, A.; AVCI, ATAKAN; Dirim, B.; DİRİM, MEHMET SABRİ; Işıklı, F.; IŞIKLI, FIRAT; Tekin, M.; TEKİN, MERVE; Türköz, N.; Mühendislik Fakültesi; Makine Mühendisliği Bölümü; 0000-0003-1662-5649; 0000-0003-2831-3175; 0000-0002-9009-8069; AAH-8619-2019; AAG-8571-2021; JCN-8081-2023; HNS-2001-2023In this study, a specifically designed direct-acting continuously variable valve timing mechanism was used to determine speed optimised valve timings for best volumetric efficiency of an engine. This mechanism basically consists of a piezo stack and a hydraulic magnifier integrated into it. To avoid effects of excessive vibrations on the piezo-stack, the engine was operated in a non-combustion mode. An electric motor was used to power the engine. Some system limitations of the hydraulic magnifier and the piezo-stack were the main challenges to a non-stop operation. A valve lift of approximately 4 mm, obtained with maximum applicable voltage of 600V to the piezo-stack, was referred to for comparison instead of the 7.6 mm original value. Tests were conducted for 30 inlet valve timing combinations at four different engine speeds from 1500 to 3000 rpm with 500 rpm increments. Timing pairs for the best VE were determined. They yielded 11.5% to 19.4% better volumetric efficiencies at 4mm lift than those obtained with the original valve timing of the cold engine. We also predicted 5-11.5% overall efficiency improvement, depending on engine type and operating conditions. Despite some practical challenges, better VE values have been obtained for a specific engine at varied speeds.