Person: SÜRMEN, ALİ
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SÜRMEN
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ALİ
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Publication Combustion characteristics and performance of a wankel engine for unmanned aerial vehicles at various altitudes(Elsevier Sci Ltd, 2023-08-16) Küçük, Merve; Şener, Ramazan; Sürmen, Ali; SÜRMEN, ALİ; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0001-6108-8673This study investigates the effects of altitude on the combustion, emissions, and performance of a Wankel engine for unmanned aerial vehicles (UAVs). The main motivation behind the presented study is to contribute to the Wankel engine designs used as a power source in UAVs by revealing the operating conditions at various altitudes. For these purposes, a gasoline fueled Wankel engine was simulated at sea level conditions for different equivalence ratios and results were validated with their experimental counterparts. Then, CFD simulations were carried out at various altitudes (6000 ft, 10,000 ft, and 15,000 ft). The simulation results show that decreasing ambient air temperature, and pressure at higher altitudes reduces the fresh charge density, hence combustion efficiency and heat release rate (HRR). As a result, the performance characteristics such as the indicated mean effective pressure (IMEP), the indicated torque, and indicated power decrease and exhaust emissions increase. For 6000 rpm, IMEP decreases by 39.11%, 53.79%, and 69.22%, and the indicated power reduces by 35.51%, 52.47%, and 65.05% at the altitudes of 6000 ft, 10,000 ft, and 15,000 ft, respectively, compared to those obtained at the sea level conditions. As for exhaust emissions, CO and CO2 are lowest at sea level conditions and increase with altitude.Publication Effectiveness of hydrogen enrichment strategy for wankel engines in unmanned aerial vehicle applications at various altitudes(Pergamon-elsevier Science Ltd, 2023-12-17) Küçük, Merve; Şener, Ramazan; Sürmen, Ali; SÜRMEN, ALİ; Mühendislik FakültesiThis study investigates the effectiveness of the hydrogen-enrichment strategy on a Wankel engine for unmanned aerial vehicles (UAVs). The primary motivation behind this study is to contribute to the Wankel-type rotary engine designs by revealing the influences of the hydrogen enrichment method on the Wankel engine performance at various altitudes. To achieve these objectives, CFD simulations were conducted by applying a hydrogen enrichment method to a neat gasoline Wankel engine model at sea level, 5000 ft and 15,000 ft altitudes. The hydrogen energy fraction at the intake was gradually increased from 0% to 10%. The decrease in ambient air temperature, pressure, density, and insuffi-cient fresh charge with the increase in altitude leads to the reduced reference chamber temperature and pressure of the Wankel engine. Thus, the combustion worsens, the heat release rate (HRR) and performance decrease, also emissions deteriorate in these colder operating conditions. On the other hand, the unique physicochemical properties of hydrogen such as wide flammability limits, high homogeneity, relatively small quenching distance and high flame speed allow hydrogen-enriched mixture flames to propagate to-ward the narrower gaps in the combustion chamber and make up for some drawbacks of Wankel engines. As a result, flame propagation is accelerated and fuel burning rate, peak pressure and temperature values in the reference chamber are increased by hydrogen addition. For the cases at sea level with 5% and 10% hydrogen energy fraction, IMEP is increased by 6.59%, 8.50%, and the indicated power is increased by 35.51% and 52.47%. In the cases with the same energy fraction at 15,000 ft, IMEP is increased by 26.61% and 48.75%, and the indicated power is reduced by 26.61% and 48.75%, respectively. It has been proven that a small amount of hydrogen by energy fraction improves combustion effi-ciency and performance. The findings show that hydrogen has excellent compatibility with Wankel engines and hydrogen enrichment is a very practical concept for the improvement of the performance of these engines for UAVs. Thus, Wankel engines, which are already a very favorable power source for UAVs, become even more favorable by the hydrogen -blending strategy.Publication Influence of hydrogen enrichment strategy on performance characteristics, combustion and emissions of a rotary engine for unmanned aerial vehicles (uavs)(Mdpi, 2022-12-01) Küçük, Merve; Şener, Ramazan; KÜÇÜK, MERVE; Sürmen, Ali; SÜRMEN, ALİ; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; JCN-8081-2023In recent years, there has been great interest in Wankel-type rotary engines, which are one of the most suitable power sources for unmanned aerial vehicle (UAV) applications due to their high power-to-size and power-to-weight ratios. The purpose of the present study was to investigate the potential of a hydrogen enrichment strategy for the improvement of the performance and reduction of the emissions of Wankel engines. The main motivation behind this study was to make Wankel engines, which are already very advantageous for UAV applications, even more advantageous by applying the hydrogen enrichment technique. In this study, hydrogen addition was implemented in a spark-ignition rotary engine model operating at a constant engine speed of 6000 rpm. The mass fraction of hydrogen in the intake gradually increased from 0% to 10%. Simulation results revealed that addition of hydrogen to the fuel accelerated the flame propagation and increased the burning speed of the fuel, the combustion temperature and the peak pressure in the working chamber. These phenomena had a very positive effect on the performance and emissions of the Wankel engine. The indicated mean effective pressure (IMEP) increased by 8.18% and 9.68% and the indicated torque increased by 6.15% and 7.99% for the 5% and 10% hydrogen mass fraction cases, respectively, compared to those obtained with neat gasoline. In contrast, CO emissions were reduced by 33.35% and 46.21% and soot emissions by 11.92% and 20.06% for 5% and 10% hydrogen additions, respectively. NOx emissions increased with the application of the hydrogen enrichment strategy for the Wankel engine.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 Modelling and performance analysis of an electric vehicle powered by a PEM fuel cell on new european driving cycle (NEDC)(Springer, 2021-03-17) Işıklı, Fırat; Sürmen, Ali; Gelen, Ayetül; IŞIKLI, FIRAT; SÜRMEN, ALİ; Mühendislik Fakültesi; Otomotiv Mühendisliği Bölümü; 0000-0003-1662-5649; HNS-2001-2023; JCN-8081-2023Modelling of a complete polymer electrolyte membrane fuel cell (PEMFC) power systems and performance of the models when subjected to common driving cycle are important research issues. In this study a complete PEMFC system, including air and hydrogen supply equipment, fuel cell stack, electrical system and a 75 kW car, is modelled. An efficiency map of a brand new electric motor is directly imported into the model for it. MATLAB & Simulink tools, based on this mathematical model of PEMFC, are used to establish a dynamic model for a vehicle which is electrically supplied by the fuel cell according to cruise characteristics of New European Driving Cycle (NEDC). Model results show significant instabilities during transient operation regarding the late response of the air supply system. Obtained stack characteristics are similar to those obtained in similar studies conducted previously. Performance results of the car based on energy consumption shows perfect agreement with the results of another model developed for an electric vehicle of the same weight and run also on NEDC.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.