Automotive Science and Engineering

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In this study, a numerical simulation using the CFD software, FLUENT, has been conducted to examine the effect of various shapes of the venturi component sections in order to find the optimum venturi specifications to increase the EGR rate with minimum pressure loss at the part load operation range. The CFD results reveal that the venturi should be precisely optimized to introduce the required amount of EGR to the engine manifold. Then, the optimum venturi was manufactured, and it was installed on the engine intake system. By using the optimum Venturi EGR system instead of original system the 26% increase in EGR flow rate to the engine manifold is observed. In the second part of the paper, an experimental investigation was carried out on a “Lister 8-1” dual fuel (diesel – natural gas) engine to examine the simultaneous effect of inlet air pre-heating and EGR on performance and emission characteristics of a dual fuel engine. The use of EGR at high levels seems to be unable to improve the engine performance at part loads, however, it is shown that EGR combined with pre-heating of inlet air can slightly increase thermal efficiency, resulting in reduced levels of both UHC and NOx emissions. CO and HC emissions were reduced by 24% and 31%, respectively. The NOx emissions were decreased by 21% because of the lower combustion temperature due to the much inert gas brought by EGR and decreased oxygen concentration in the cylinder.

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Nitrogen oxides (NOx) contribute to a wide range of environmental effects including the formation of acid rain and destroy ozone layer. In-cylinder high temperature flame and high oxygen concentration are the parameters which affect the NOx emissions. The EGR system is a very effective way for reducing NOx emission from a diesel engine (via reduction of these parameters), particularly at the high load of engine operation condition. In this study, the influence of EGR on diesel engine combustion, NOx/PM emissions, brake specific fuel consumption (BSFC), engine thermal efficiency, cylinder pressure and heat release rate (HRR) are analyzed and presented. The experiments have been conducted on a turbocharged DI diesel engine under full load condition at two different injection timings in order to distinguish and quantify some effects of Hot and Cooled EGR with various rates on the engine parameters. Experimental results showed that increase of EGR rate has a negative effect on air-fuel ratio. For a premixed combustion at constant boost pressure, ignition delay is increased leading to retardation of all combustion process, a low HRR peak and reduce of in-cylinder peak temperature. Using of Hot EGR reduces NOX emissions whereas PM emissions are increased. The advance of injection timing resulted in the reduction PM while both NOX emissions and fuel consumption were increased. The use of cooled EGR was more effective compared to the hot EGR. As a result, the EGR temperature has no significant impact on NOx emissions. With increasing EGR rate, unequal EGR distribution was increased in inlet port of cylinders while the reducing EGR temperature (cooled EGR) improved its distribution among the engine cylinders and decreased the EGR cylinder-to-cylinder variations.

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Global air pollution is a serious threat caused by excessive use of fossil fuels for transportation. Despite the fact that diesel fuel is a big environmental pollutant as it contains different hydrocarbons, sulphur and crude oil residues, it is yet regarded as a highly critical fuel due to its wide applications. Nowadays, biodiesel as a renewable additive is blended with diesel fuel to achieve numerous advantages such as lowering CO2, and CO emissions as well as higher lubricity. However, a few key drawbacks including higher production cost, deteriorated performance and likelihood to increase nitrogen oxide emissions have also been attributed to the application of diesel-biodiesel blends. Expanded polystyrene (EPS), known as a polymer for packaging and insulation, is an ideal material for energy recovery as it holds high energy value (1 kg of EPS is equivalent to 1.3 liters of liquid fuel). In this study, biodiesel was applied as a solvent of expanded polystyrene (EPS) during a special chemical and physical treatment. Various percentages of EPS in biodiesel blended diesel were tested to evaluate the fuel properties, emissions and performance of CI engine. The results of the variance analysis revealed that the addition of the additive improved diesel fuel properties by increasing the flash point as well as the reduction of density and viscosity. Despite a 3.6% reduction in brake power, a significant decrease in brake specific fuel consumption (7.26%) and an increase in brake thermal efficiency (7.83%) were observed at the full load and maximum speed of the engine. Additionally, considerable reductions of CO, CO2, NOx and smoke were achieved.

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Porous media has interesting features in compared with free flame combustion due to the extended of the lean flammability limits and lower emissions. Advanced new generation of internal combustion (IC) engines are expected to have far better emissions levels both gaseous and particulate matter, at the same time having far lower fuel consumption on a wide range of operating condition. These criteria could be improved having a homogeneous combustion process in an engine. Present work considers simulation of direct fuel injection in an IC engine equipped with a chemically inert porous medium (PM), having cylindrical geometry that is installed in cylinder head to homogenize and stabilize the combustion process. A numerical study of a 3D model, PM engine is carried out using a modified version of the KIVA-3V code. Since there is not any published material for PM-engines in literature, the numerical results for combustion waves propagation within PM are compared with experimental data available in the literature for a lean mixture of air and methane under filtration in packed bed, the accuracy of results are very promising. For PM-engine simulation the methane fuel is injected directly through a hot PM which is mounted in cylinder head. Therefore volumetric combustion occurs as a result within PM and in-cylinder. The effects of injection timing on mixture formation, pressure and temperature distribution in both phases of PM and incylinder fluid together with combustion emissions such as CO and NO are studied in detail for an important part of the cycle.

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Running the industrial components at a proper temperature is always a big challenge for engineers. Internal combustion engines are among these components in which temperature plays a big role in their performance and emissions. With the development of new technology in the fields of ‘nano-materials’ and ‘nano-fluids’, it seems very promising to use this technology as a coolant in the internal combustion engines. In this study, a nano-fluid (Al2O3-Water/Ethylene Glycol (EG)) is used as an engine coolant along with an optimized heat exchanger to reduce the warm-up timing. The effect of nano-fluid concentration is considered here by using their corresponding governing equations, such as momentum and energy. The engine coolant thermal behavior calculation is carried out based on the lumped method. The obtained results indicated that using different percentage of nano-fluid mixtures (by volume), such as Al2O3- Water/EG as engine coolant enhances the heat transfer coefficient and reduces the warm-up timing which, in turn, results in reduced emissions and fuel consumption.

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Air pollution is one of the major issues about the diesel engines in todays' world. It is a special concern in those areas that have difficulty meeting health-based outdoor air quality standards. Natural gas has low emission and resource abundance and also conventional compression ignition engine can be easily converted to a dual fuel mode to use natural gas as main fuel and diesel as pilot injection. The main object of this work is to investigate the effect of number of injector nozzle hole on the combustion and exhaust emission in a gas engine ignited with diesel fuel. We use one and three-dimensional simulation in parallel way in order to analyze the performance and combustion process of a dual fuel engine. The experimental results have also reported and compared with the simulated data.

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Cooled exhaust gas recirculation is emerging as a promising technology to address the increasing demand for fuel economy without compromising performance in turbocharged spark injection engines. The objectives of this study are to quantify the increase in knock resistance and to decrease the enrichment and emission at high load. For this purpose four stroke turbo charged Spark Ignition engine (EF7-TC) including its different systems such as inlet and exhaust manifold, exhaust pipe and engine geometry are modeled using GT Power Software. As predicted, using cooled EGR at high load enabled operation at lambda near to one with the same serial engine performances, which offers substantial advantages Such As BSFC reduction (up to 14%), and emission reduction (CO, NOx).

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Artificial neural network was considered in previous studies for prediction of engine performance and emissions. ICA methodology was inspired in order to optimize the weights of multilayer perceptron (MLP) of artificial neural network so that closer estimation of output results can be achieved. Current paper aimed at prediction of engine power, soot, NOx, CO2, O2, and temperature with the aid of feed forward ANN optimized by imperialist competitive algorithm. Excess air percent, engine revolution, torque, and fuel mass were taken into account as elements of input layer in initial neural network. According to obtained results, the ANN-ICA hybrid approach was well-disposed in prediction of results. NOx revealed the best prediction performance with the least amount of MSE and the highest correlation coefficient(R) of 0.9902. Experiments were carried out at 13 mode for four cases, each comprised of amount of plastic waste (0, 2.5, 5, 7.5g) dissolved in base fuel as 95% diesel and 5% biodiesel. ANN-ICA method has proved to be selfsufficient, reliable and accurate medium of engine characteristics prediction optimization in terms of both engine efficiency and emission.

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The effects of unleaded gasoline and unleaded gasoline–ethanol blends on engine performance and pollutant emissions were investigated experimentally in a single cylinder, four-stroke spark-ignition engine with variable engine speeds (2600–3500 rpm). Four different blends on a volume basis were applied. These are E0 (0% ethanol + 100% unleaded gasoline), E3 (3% ethanol + 97% unleaded gasoline), E7 (7% ethanol + 93% unleaded gasoline) and E10 (10% ethanol + 90% unleaded gasoline). Results of the engine test indicated that using ethanol–gasoline blended fuels improve output torque, power, volumetric efficiency and fuel consumption of the engine it was also noted that fuel consumption depends on the engine speed rather than the ethanol content for ethanol less than 10% blended ratio. CO and unburned hydrocarbons emissions decrease dramatically as a result of the leaning effect caused by the ethanol addition CO2 emission increases because of the improved combustion.

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Modern diesel engines should have higher pollutant emissions standards with better performance and by using split injection strategies which could optimize the air – fuel mixture, this purpose could be achieved. After achieving the successful validation between modeling and experimental results for both single and double injection strategies, for the first time and in this paper, double injection strategies with new nozzle configuration were used in which number of nozzle holes were doubled and located below the previous holes and then double injection strategies were implemented in a case that for each pulse of injections upper or below holes were used, then this study focused on the effects of the new nozzle configuration holes angle in each pulse of injections. This study confirms that split injection could decrease Nox emission, because it has lower maximum in-cylinder temperature than single injection case due to its separate second stage of combustion, also results showed that using new nozzle configuration with two rows of holes could be more effective in decreasing pollutant emissions without any significant effects on engine performance.

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To improve the engine performance and reduce emissions, factors such as changing ignition and injection timing along with converting of port injection system to direct injection in SI(spark-ignited) engines and hydrogen enrichment to CNG fuel at WOT conditions have a great importance. In this work, which was investigated experimentally (for CNG engine) and theoretically (for combustion Eddy Break-Up model and turbulence model is used) in a single- cylinder four-stroke SI engine at various engine speeds (2000-6000 rpm in 1000 rpm intervals), injection timing (130-210 crank angle(CA) in 50 CA intervals), ignition timing (19-28 CA in 2 degree intervals), 20 bar injection pressure and five hydrogen volume fraction 0% to 50% in the blend of HCNG. The results showed that fuel conversion efficiency, torque and power output were increased, while duration of heat release rate was shortened and found to be advanced. NOx emission was increased with the increase of hydrogen addition in the blend and the lowest NOx was obtained at the lowest speed and retarded ignition timing, hence 19° before top dead center. 

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Pollutant emissions from diesel engines are significantly affected by fuel injection strategies that could reduce NOx and Soot emissions. For the first time and in this study, numerical simulations were performed to consider the influences of changing the injection duration in each pulse of the double injection strategies on in-cylinder parameters and pollutant emissions. Results confirmed that double injection strategies could influence the in-cylinder temperature, which leads to a reduction in NOx and soot emissions. Additionally, it is seen that decreasing the injection duration could increase the in-cylinder peak pressure and temperature. It could also reduce the soot emission owing to the better fuel atomization. Moreover, RATE+0.5CA case, which injection duration for each pulse increases 0.5 CA, was selected to be the optimum case in reduction of pollutant emissions.
 

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According to the global air pollution Crisis, it seems necessary to finding a way for cars pollutions. The Combination of alcoholic fuels with gasoline is one of the methods to reduce pollutions. For optimizing engine performance, fuel availability, toxicity and political advantage, a blend of ethanol, methanol and gasoline is likely to be preferable to using any of these individual substances alone. So the purpose of this paper is studying methanol, ethanol and gasoline blend effect on engine emissions at different engine speed. The simulated model was validated in different RPMs of gasoline engine at full load condition. The effect of combined fuel injection in the simulated model was investigated and compared with the experimental results. The results of simulation have good agreement with experiments. The results show that by ethanol and methanol with gasoline blend CO and HC emissions are lower than gasoline mode, but the NOx and CO2 pollutants increases.
 

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Changing various parts of different types of engines in the maintenance phase was always a remarkable question. Purpose of the present study is identifying the performance and emissions of a diesel-fueled engine (OM457) before and after replacing connecting rod and crankshaft with another engine (OM444) in the same engine family.

At the first step, a solid model was made then some CFD analyses were done and, results were compared with previous studies for validation after that in the CFD modeling the impact of these parts replacement were observed, and the performance and emissions of this engine were compared with data before replacements.

As the result of these replacements, compression ratio and performance were decreased. HC and CO were increased due to lower air-fuel ratio, and NO_X was decreased because of the lower temperature of in cylinder. Lowering the CR of a diesel engine will reduce the NOx emission numerously but the increase in other emissions will be slight. So for the environment issues lowering the CR will be a practical and low cost method.

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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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In this research, the separate and simultaneous effects of pilot-main injection dwell time, pilot fuel quantity, and hydrogen gas addition on combustion characteristics, emissions formation, and performance in a heavy-duty diesel engine were investigated. To conduct the numerical study, valid and reliable models such as KH-RT for the break-up, K-Zeta-F for turbulence, and also ECFM-3Z for combustion were used. The effects of thirty-one different strategies based on two variables such as pilot-main injection dwell time (20, 25, 30, 35, and 40 CA) and pilot fuel quantity (5, 10, and 15% of total fuel per cycle) on NDC and DHC were investigated. The obtained results showed that by decreasing pilot-main injection dwell time due to shorter combustion duration and higher MCP, MCT, and HRRPP, amounts of CO and soot emissions decreased at the expense of high NOx formation. Also, increasing pilot fuel quantity due to higher combustion temperature and less oxygen concentration for the main fuel injection event led to an increase of NOx and soot emissions simultaneously. The addition of H2 due to significant heating value has increased IP and improved ISFC at the expense of NOx emissions but considerably decreased CO and soot emissions simultaneously.

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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.