Automotive Science and Engineering

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Changing the compression ratio and presence of turbocharger are two important issues, affecting on performance, and exhaust emissions in internal combustion engines. To study the functional properties and exhaust emissions in regards to compression ratio at different speeds, the numerical solution of the governing equations on the fluid flow inside the combustion chamber and the numerical solution of one-dimensional computational fluid dynamics with the GT-Power software carried out. The diesel engine was with a displacement of 6.4 Lit and Turbocharged six-cylinder. In this engine was chosen, the compression ratio between 15: 1 and 19: 1 with intervals of one unit and the range of engine speed was from 800 to 2400 rpm. The results showed that by the presence of a turbocharger and changing the compression ratio from 17: 1 to 19: 1, the braking power and torque increased by about 56.24% compared to the non-turbocharged engine. In addition, was reduced the brake specific fuel consumption due to higher power output. The amount of CO and HC emissions decreases based on the reduction of the compression ratio compared to the based case, and the NOX value increases due to the production of higher heat than turbocharged engines. The overall results showed that the turbocharged engine with a 19: 1 compression ratio has the best performance and pollution characteristics.

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Nowadays, with increasing environmental pollution and damages that threaten the health of the community, a lot of research is being conducted on reducing the emission from transportation sector as one of the main sources of total worldwide emissions. It is confirmed that one of the ways to reduce emission is to switch from fossil-based fuels to more environmentally benign fuels. Among the options, electric vehicles (EVs) have proven themselves as one of the best options. In this research study, a solar-based EV which is developed and built at University of Tehran is studied.  The environmental impacts assessment along with the energy consumption of this solar-electric vehicle is investigated

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One of the most significant issues of recent decades is pollution and dangers that may threat the environment. Different approaches were presented to protect the environment and target various sources of pollution. Old vehicles are one of the major sources of pollution in megacities as they consume and emit a lot of emissions. Therefore governments in different countries try to levy tax on pollution to motivate people to drive environment friendly and more efficient vehicles.
Tehran is one of the cities suffering rigorously from poor air quality. As a result, approximately 44 days in each year the air quality reckons as unhealthy for all residents. One of the suggested solutions is replacing conventional taxis across the city with hybrid electric vehicles. In this article this solution for the city of Tehran, Iran will be discussed and its feasibility will be evaluated using life cycle assessment.  
In order to conduct this, first data associated with air quality, pollution and taxis distribution in the city were presented. Then different designated vehicles were evaluated based on their technical performance and the emission they generate in different stages. Using the proposed model a comprehensive cost is defined and different vehicles were compared and the most viable choices by various considerations is introduced.

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This study uses real driving cycles of a city bus and a standard driving cycle “WLTP” to implement a full comparison for energy demand and fuel consumption for different propulsion systems (i.e., Diesel ICE, Fuel cell and Electric engines). To better understand the comparison, a life cycle assessment is conducted using “GREET” and “GHGenius” software, which represents a clear demonstration of side effects and emissions of each engine on the environment. The results show that for “WLTP” cycle the bus needs 2423kJ energy for traveling each kilometer while the averaged amount of energy for traveling one kilometer of real driving cycle reaches to 1708kJ. By computing total energy use of  an electric bus we conclude, electric buses use almost 58% of electric energy for driving and the rest is lost. Then fuel cell and internal combustion engine buses have energy efficiency of 36% and 24% respectively. Concerning LCA analysis, it becomes apparent that unlike efficiency, electric buses are not environmentally benign as fuel cell buses. LCA analysis showed that fuel cell buses that use steam reforming hydrogen production process are a cleaner option than electric buses. Finally, since diesel buses produce the most emission, especially CO2, and consume the most energy in the total life cycle, they have no advantage for public transportation fleet.

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In internal combustion engines, the turbocharger and alternative fuels are two important factors affecting engine performance and exhaust emission. In this investigation, a one-dimensional computational fluid dynamics with GT-Power software was used to simulate a six-cylinder turbocharged diesel engine and the naturally aspirated diesel engine to study the performance and exhaust emissions with alternative fuels. The base fuel (diesel), methanol, ethanol, the blend of diesel and ethanol, biodiesel and decane was used. The results showed that decane fuel in the turbocharged engine has more brake power and torque (about 3.86%) compared to the base fuel. Also, the results showed that the turbocharger reduces carbon monoxide and hydrocarbon emissions, and biodiesel fuel has the least amount of carbon monoxide and hydrocarbon among other fuels. At the same time, the lowest NO_X emission was obtained by decane fuel. As a final result can be demonstrated that the decane fuel in the turbocharged engine and the biodiesel fuel in the naturally aspirated engine could be a good alternative ratio to diesel fuel in diesel engines.

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This paper introduces a novel powertrain system composed of a liquid ammonia internal combustion engine, a dissociation and separation unit, and a PEM fuel cell system developed for vehicular applications. Using a carbon-free fuel for the ICE and producing hydrogen on board for PEMFC use significantly enhance this novel systemchr('39')s environmental effects. The thermodynamic analyses are conducted using EES and MATLAB software. The results show that while this hybrid powertrain system produces 120 kW output power, energy and exergy efficiencies are 45.2% and 43.1%, respectively. The overall exergy destruction rate of the system becomes 237.4 kW.The fuel consumption, engine speed, and battery state of charge (SoC) analyses are calculated using three driving cycles. These vehicles consume 7.9, 5.7, and 7.7 liters of liquid ammonia per 100 km in FTP-75, NEDC, and HWFET driving cycles, respectively. The battery state of charge differentiation in these three cycles shows the practicality of this novel powertrain system specially in inner-city driving cycles as the battery does not confront any intense decline of SOC to the minimum level. HWFET results show the great dependence of the vehicle on ICE and low PEM fuel cell function, which results in releasing decomposed hydrogen to the environment.

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