LEE- Otomotiv-Yüksek Lisans
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ÖgeInvestigation of regenerative braking efficiency in different drive cycles(Graduate School, 2023-06-23) Barın, Berkay ; Şen, Osman Taha ; 503201705 ; AutomotiveAs being an important fact, climate change threatens the world population and its impact has become crucial recently. Thus, the world is being prepared for a very fresh era: green energy and electrification era. The European Union proposes the EU7 emission regulation, which has lower limits compared to prior regulations; and net zero emission policies are already adopted by several governments throughout the world. These developments increase the importance of electric vehicles (EVs), which have already start to replace the conventional vehicles due to their zero tailpipe emissions. Furthermore, the high efficiency, quiet operation and improved performance characteristics of EVs make them more preferable, and the recent advancements in battery technology bring this preference to the fore. Though, EVs still have significant disadvantages such as limited driving range and long charging time. The concept of regenerative braking becomes crucial in increasing the battery state of charge, which improves the driving range and reduces the required charging duration. Thus, the optimization of the regenerative braking system operation becomes critical. The chief objective of this study is to investigate the utilization rate of regenerative braking in different drive cycles, which depends on braking rate and road conditions. Consequently, seven well-known different drive cycles are selected, which vary with distance, urban / highway scenario, traction per kilometres, etc. An E class sport utility battery electric vehicle is selected for modelling purposes and it is subjected to all drive cycles. The driving resistances are calculated and the instantaneous electric motor torque demand is obtained for all drive cycles. Furthermore, the total braking and traction force ratios are evaluated for all drive cycles. It is observed that the comparison of these drive cycles based on total braking and traction force values does not provide reasonable conclusions due to the variation of drive cycle range. Thus, results are compared by normalizing the traction and braking forces by the range of each drive cycle. Finally, a braking to traction ratio is determined for all drive cycles, and the tendency of regenerative braking utilization rate change is investigated. Based on the results, it is observed that the braking to traction ratio of the vehicle significantly reduces when the vehicle moves from urban to highway drive cycle. Furthermore, the utilization rate of the regenerative braking also drops down to %13 from %53, when the drive cycle transition from urban to highway occur. The low braking to traction ratio shows that the recovered energy begins to be insufficient in highway driving conditions, and enough energy cannot be provided for the charging of the battery pack. In addition, the test vehicle's weight has increased to its gross weight. Subsequently, results were reanalyzed in the view of weight change. Finally, it is observed that weight change has not a significant effect on utilization rate in city conditions, whereas it increases the efficiency around %6 in highway conditions.
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ÖgeOptimization design parameter of dual mass flywheel coupled with a non-linear elastic path(Graduate School, 2023) Karakuş, Gökay ; Şen, Osman Taha ; 807252 ; Automotive ProgrammeToday, expectations from automotive industry are high in the fields of performance, comfort, economy and environmental protection. That is why, the automotive industry must have a knowledge, experience, development processes, and strong research. Hence, the design of the components that transmit power from the internal combustion engine to the wheels via axes in a vehicle are crucial research topics. The flywheel, which is the primary element in power transmission system, works in engine in order to reduce the speed fluctuations on the crankshaft. Along with the studies in the field of flywheel development, dual-mass flywheels have been started to be used as an alternative to the single-mass flywheel. Briefly, the dual mass flywheel can be defined as the combination of two single mass flywheels. The spring damper system is combined with these two single mass flywheels. The dual-mass flywheel, which is used in diesel engines, is thought to have favorable effects on the dynamics of the power transmission system compared to the single-mass flywheel. In 1985, the first dual mass flywheel (DMF) was manufactured in automotive sector. In begin, dampers in flywheel were not lubricated and the springs are stand away from outside and created some wear problems. In 1987, DMF is lubricated with grease oil for the first time. Service life problem was no longer an issue thanks to grease oil application. Around 1989, arc spring damper was innovation for the DMF, and it had pretty much solved all resonance problems. Alson manufacturing costs were continually reduced. The primary mass of flywheel was made by casting or forged steel at first production batches. Over time, the primary mass was formed from sheet metal parts by metal-forming specialists. In 1995, folded masses were developed from sheet metal in order to increase inertia moment of primary mass of flywheel. This development led to the widespread use of the DMF. However, there is some disadvantages such as cost, the achievable improvements are seen clearly, therefore, DMF are used widespread in vehicles. There are some advantages of dual mass flywheel such as isolation from torsional vibration, relief of transmission and crankshaft. Within the scope of this study, firstly, give information about flywheel, parts of dual mass flywheel and its advantages. Then, while engine is running, the working principles of dual mass flywheel is mentioned. Also, the single mass flywheel and dual mass flywheel are compared and it has been observed that the resonance regions are reduced below the engine idle speed with the use of dual-mass flywheel. After all crucial information was explained, mathematical model of DMF is built. The model was solved in Matlab for all optimization. Sensitivity analysis was done in order to determine the parameter effects on system. The design parameters were determined as stiffness ratio, damping ratio and inertia ratio. Also, the system was running on non-linear cubic path, that is why, non-linear stiffness ratio is also important parameter to examine system correctly. The primary body represent not only primary flywheel itself but also engine side dynamic properties.
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ÖgeParallel hybrid electric truck design(Graduate School, 2022-05-06) Darıcı, Onurcan ; Şen, Osman Taha ; 503171719 ; AutomotiveAutomotive industry has been developed since years by beginning of first patent of it. In those years automotive companies has been dealt with different type of issues. One of the biggest challenge is fuel consumption and CO2 emissions for the automobiles. Nowadays CO2 emissions are one of the trend topics in the era. CO2 is harmful for human body besides it creates green gases effect and due to that the average temperature of the planet increases which is called "global warming" in other terms. CO2 emissions have a direct relation with fuel consumption of the engine. After reactions in the engine gasoline or diesel create CO2 as a result. To decrease CO2 emissions of the vehicle one of the key element is to decrease fuel consumption. To decrease fuel consumption there are different methods. On of the common solution is hybridization. Hybridization can be done by including two different energy sources into the specific vehicle. In the common sense, modern-day vehicles are equipped with gasoline or diesel engines. The appropriate way to hybridize a gasoline/diesel engine can be done by adding an electrical source to the vehicle. Hybridization has different types and each type has its own advantage and disadvantage. One of the common hybrid electric vehicle type is parallel hybrid electric. In this thesis, a heavy-duty parallel hybrid electric truck has been investigated. The conventional model is selected as an 18t 4x2 heavy-duty commercial vehicle, Mercedes – Benz Actros. It is one of the most sold truck in 2020 Turkey truck market. 18t 4x2 Mercedes-Benz Actros truck is modelled in AVL Cruise system to compute conventional vehicle's fuel consumption. After that, conventional truck is hybridized by electric motor that is coupled to its transmission exit. Model B parallel hybrid truck is computed again on the same VECTO cycles and fuel consumptions and CO2 emission of the vehicles are compared. The last model is selected which is equipped with a downsized engine. Parallel hybrid+downsized, Model C, is computed and compared with other models. All these three models are created in AVL Cruise and simulations are done in the programme. At the end of the results, advantages and disadvantages are noted in the conclusion chapter.