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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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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In this paper, a method based on binary-coded genetic algorithm is proposed to explore an optimization method, for obtaining an optimal elliptical tank. This optimization method enhances the rollover threshold of a tank vehicle, especially under partial filling conditions. Minimizing the overturning moment imposed on the vehicle due to c.g. height of the liquid load, lateral acceleration and cargo load shift are properly applied. In the process, the width and height of tanker are assumed as constant parameters. Additionally, considering the constant cross-sectional area, an optimum elliptical tanker of each filling condition is presented to provide more roll stability. Moreover, the magnitudes of lateral and vertical translation of the cargo within the proposed optimal cross section under a constant lateral acceleration field are compared with those of conventional elliptical tank to demonstrate the performance potentials of the optimal shapes. Comparing the vehicle rollover threshold of proposed optimal tank with that of currently used elliptical and circular tank reveals that the optimal tank is improved approximately 18% higher than conventional one.

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The purpose of present paper is simulation a direct injection stratified charge natural gas engine. The KIVA-3V code was used for gaseous fuel injection simulation. Compression and expansion stroke of engine cycle is simulated using KIVA-3V code. In cylinder fuel equivalence ratio distribution criterion is used for studying mesh independency. The results show that 550000 cells number is sufficient. The amount of NO emission in the end of closed cycle simulation was found equal 674.875 ppm and In cylinder pressure versus engine crank angle degree was simulated that maximum value found in 366 oCA that equal to 27.3222 bar.

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The dissipated energy from periodic deformation is regarded as the main reason for heat generation and temperature rise inside the tire domain. However, the mechanical behavior of rubber parts is highly temperature dependent. In most performed investigations, the influence of thermal effects on stress/ deformation fields of pneumatic tires is ignored and just temperature distribution is considered. Hence in this study, using a series of 2D and 3D finite element models, a robust and efficient numerical study is presented for thermo-mechanical analysis of pneumatic tires specially 115/60R13 radial tire. Finally, the effects of loading condition s and ambient temperature on the thermo-mechanical properties of tire are investigated in detail. Comparing the obtained results with the available results in literature, shows a good agreement of the presented studies with related published works.

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Among human activities, motor vehicles play the most important role in air pollution. Air pollution has negative impacts on people and on the environment. In this paper the effect of oxygen-enriched air (20.8%, 21.8%, 22.8%, 23.8% and 24.8%) and different bioethanol-gasoline blends (zero, 5%, 10%, 15%, 20% and 25%) in different engine speeds (1000 rpm, 2000 rpm and 3000 rpm) on the amount of pollutants, particles, and fuel consumption were studied. To do so, a four-cylinder, four-stroke gasoline engine with Siemens fueling system was used. The results showed that when oxygen percentage in the inlet increased from 20.8% to 24.8%, the average amount of UHC, CO, fuel consumption and the number of fine and coarse particles decreased 126.75%, 11.25%, 17.02%, 77.37% and 243.25%, respectively, while the amount of CO2 and NOX increased 5.36% and 113.27%, respectively. Also the results showed that when bioethanol percentage in the mixture increased from zero to 25%, the average amount of UHC, CO2, CO and the number of fine and coarse particles decreased 104.53%, 3.45%, 34.57%, 41.42% and 96.09%, respectively, while the amount of NOX and fuel consumption increased 163.41% and 15.75%, respectively.

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Accurate and correct performance of controller in cruise control systems is important. Hence, in such systems, controller should optimize itself against noise and probable changes in system dynamic. As a matter of fact, in this article three approaches have been conducted to-ward this purpose: MIT, direct estimation and indirect estimation. These approaches are used as controllers to track reference signal. First the performance of each of these three controllers is checked. comparison of performances indicated better behavior for indirect estimation than others. Also, it has less sensitivity against external noise. Finally, by using indirect estimation method as an adaptive control approach, two parallel separate controllers are designed for two inputs, gas and braking, and their performances are compared with recent studies. It shows improvement in performance of adaptive cruise control system to track reference signal.

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In cruise control systems, the performance of the controller is important. Hence, in order to have accurate results, the nonlinear behavior of a vehicle model should also be considered. In this article, a vehicle with a nonlinear model is controlled by using a nonlinear method. The nonlinear term of the model is the generated torque of engine, which is a polynomial equation. In addition, feedback linearization is used as a nonlinear method in order to design two parallel controllers to control the movement of the vehicle. These two parallel controllers are used to control braking and gas pedals which are in charge of the angular velocity of the wheels. To check the performances of controllers, first, each controller is used separately. Finally, two parallel controllers are used to track the reference signal. Comparison between results shows that the designed controller is able to reduce the convergence time of about 10 seconds. This improvement is near 35% in comparison with near studies. In addition, it can reduce the error between the velocity of the vehicle and the values of the reference signal that results in more safety for passengers.

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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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In this article, the procedure of series hybridizing is fulfilled on the O457 city bus that is produced in Irankhodro Diesel Company. For simulation validation the bus with base diesel engine is simulated in European and Tehran compound urban–highway driving cycle and fuel consumption results compared. First the ECE_EUDC_LOW driving cycle  simulation results compared with the results of the advisor software that was some difference between two software results. For deep validation bus with base engine was simulated in Tehran driving cycle and fuel consumption calculated 53.26 Lit/100Km that was near actual value that is 59.48 Lit/100Km. After verification, a bus with series hybrid electric-diesel powertrain was designed and simulated in the European and Tehran driving cycle. Simulation results and experimental data’s shown that the series hybrid electric-diesel bus fuel consumption reduction in ‌the ECE_EUDC_LOW driving cycle, is 30% and in Tehran driving cycle is 39% less in comparison to base power train that is base diesel engine.

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Today, many car manufacturers can achieve emission standards through catalytic converters. The goals of this research was in tow sections. Initially, the amount of pollutants was measured to determine the role of the catalytic converters in the reduction of pollutants for 3 types of vehicles and in 50 cases, in the two stages before and after the catalytic converter. Then, to achieve the useful life of the catalytic converter, out of 750 test vehicle emissions were tested. Data analysis was done by SPSS software, which shows that catalytic converters can reduce up to 80% of exhaust emissions. This is independent of the type of vehicle. The useful life of the catalytic converters is up to 36 months, so they should be replaced at least every three years. Also, the pollutant standards of the technical examination centers are reviewed. For this purpose, the pollutants have been measured in 2200 vehicles. Due to the huge difference in technology, cars are divided into two main categories of carburetor and injector and are analyzed statistically. Eventually, for each group of these vehicles, the values of HC, CO and O₂ are obtained.

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As alternatives for future refrigeration, heat pumping, air conditioning, or even power generation plants are emerging due to the regulatory changes, R744 (carbon dioxide) is considered as a serious alternative to be the successor of other Halogenated Hydrocarbons Refrigerants (HHR) for the AC-system of vehicles. This paper investigates the heat transfer performance of R744 through a subcritical vehicular condenser, designed and manufactured for the first product based on NP01 platform (Iranian vehicle), at different operating conditions in terms of refrigerant mass flow rate and wind velocity. The experiments carried out in order to investigate the effect of mass flow rate, the R744 inlet temperature was observed to have sudden fluctuations. At the condenser outlet, for the smallest mass flow rate, the least variation of temperature was observed. It was also found out that for higher air velocities through the condenser, the stabilized temperature after the condenser was lower. The results show that the performance of the designed and manufactured automotive condenser based on R744 refrigerant is acceptable which makes it a suitable candidate for automotive applications.
As alternatives for future refrigeration, heat pumping, air conditioning, or even power generation plants are emerging due to the regulatory changes, R744 (carbon dioxide) is considered as a serious alternative to be the successor of other Halogenated Hydrocarbons Refrigerants (HHR) for the AC-system of vehicles. This paper investigates the heat transfer performance of R744 through a subcritical vehicular condenser, designed and manufactured for the first product based on NP01 platform (Iranian vehicle), at different operating conditions in terms of refrigerant mass flow rate and wind velocity. The experiments carried out in order to investigate the effect of mass flow rate, the R744 inlet temperature was observed to have sudden fluctuations. At the condenser outlet, for the smallest mass flow rate, the least variation of temperature was observed. It was also found out that for higher air velocities through the condenser, the stabilized temperature after the condenser was lower. The results show that the performance of the designed and manufactured automotive condenser based on R744 refrigerant is acceptable which makes it a suitable candidate for automotive applications.
 

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Portfolio optimization is the process of distributing a specific amount of wealth across various available assets, with the aim of achieving the highest possible returns while minimizing investment risks. There are a large number of studies on portfolio optimization in various cases, covering numerous applications; however, none have focused exclusively on the automotive industry as one of the largest manufacturing sectors in the global economy. Since the economic activity of this industry has a coherent pattern with that of the global economy, the automotive industry is very sensitive to the booms and busts of business cycles. Due to the volatile global economic environment and significant inter-industry implications, providing an appropriate approach to investing in this sector is essential. Thus, this paper aims to provide an appropriate approach to investing in this sector. In this study, an extended Conditional Drawdown at Risk (CDaR) model with cardinality and threshold constraints for portfolio optimization problems is proposed, which is highly beneficial in practical portfolio management. The feature of this risk management technique is that it admits the formulation of a portfolio optimization model as a linear programming problem. The CDaR risk functions family also enables a risk manager to control the worst ( 1-α)×100%  drawdowns. In order to demonstrate the effectiveness of the proposed model, a real-world empirical case study from the annual financial statements of automotive companies and their suppliers in the Tehran Stock Exchange (TSE) database is utilized.