Automotive Science and Engineering

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Intake system design as well as inlet ports and valves configuration is of paramount importance in the optimal performance of internal combustion engines. In the present study, the effect of inlet ports design is investigated on OM-457LA diesel engine by using a CFD analysis and the AVL-Fire code as well. A thermodynamic model of the whole engine equipped with a turbocharger and an intercooler is used to obtain the initial and boundary conditions of the inlet and outlet ports of the engine cylinder which are necessary for performing the three dimensional CFD analysis. The intake stroke as well as the compression and power strokes are included in this three dimensional CFD model. As a mean of validation the performance of the engine model with the base configuration of the inlet ports is compared to the experimental data. Two new alternative configurations for the inlet ports are then investigated with respect to the turbulence levels of the in-cylinder flow and the combustion characteristics as well. Finally it is demonstrated that applying the new configurations results in circa 75% reduction in nitric oxide formation besides increase of 32% in the in-cylinder flow swirl.

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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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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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Generally, parts whose geometric form in the final configuration, or before additional operations such as machining, does not require special dimensional accuracy are produced using casting methods. Producing parts with this method results in significant deviations in dimensions and geometric forms from the main designed geometric model. Due to economic considerations, scrapping such parts will result in energy and material waste and high costs. In this study, dimensional deviations at the exhaust manifold outlet and deviations from the defined geometric tolerance limits of the part during the repair process are identified as geometric non-conformities and investigated using computer tools. Considering the harsh operating conditions under which the engine is under full load, the temperature distribution is determined using computational fluid dynamics, and the thermo-elastic stress distribution is calculated using the finite element method, accounting for the loads applied to the structure. The main part model and the non-conforming models with upper and lower limits in geometric dimensions have been investigated with respect to the deviation in thermo-elastic stress relative to the reference value in the part with the nominal size. The results showed that, given the amount of stress changes in the desired area of parts with deviations from the main design, these parts are also usable and have a lifetime almost the same as a part produced with the nominal size.

 

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This study employs two-dimensional CFD simulations to analyze how rear slant angle and inter-vehicle spacing dictate aerodynamic drag in a tandem Ahmed body configuration. We systematically evaluated slant angles from 15° to 45° and longitudinal spacings from X/L = 0.1 to 0.5. The results delineate three distinct aerodynamic regimes for the trailing vehicle: a drafting zone at close distances (X/L=0.1) with significantly reduced drag, an interference zone (X/L=0.2-0.3) where drag peaks, and an independence zone (X/L>0.4) where vehicles behave aerodynamically isolated. Furthermore, the model successfully captures the critical drag rise as the slant angle surpasses 30°, a key flow transition. While the simulation over-predicts absolute drag values, which is an expected outcome of the 2D approach, it demonstrates high fidelity in capturing complex trends, providing foundational insights for optimizing vehicle platooning strategies.