Automotive Science and Engineering

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Conventional compression ignition (CI) engines are known for their high thermal efficiency compared to spark ignited (SI) engines. Gasoline because of its higher ignition delay has much lower soot emission in comparison with diesel fuel. Using double injection strategy reduces the maximum heat release rate that leads to NOx emission reduction. In this paper, a numerical study of a gasoline fuelled heavy duty Caterpillar 3401 engine was conducted via three dimensional computational fluid dynamics (CFD) procedures and compared with experimental data. The model results show a good agreement with experimental data. To have a better design the effect of injection characteristics such as, the main SOI timing, injection duration and nozzle hole size investigated on combustion and emissions and an optimized point find. The results suggest an optimization in injection characteristics for simultaneous reduction of NOx and soot emissions with negligible change in IMEP.

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Multidimensional modelling of open-cycle process of OM355 engine was developed. Calculations for computational mesh were carried out. The results of the model were validated by experimentally measured in-cylinder pressure and the good agreement between calculations and measurements approved the trustworthy of numerical code. Results included pressure, temperature, emission and Rate of heat release diagrams were represented for the full cycle. Further more local flow field velocity vectors were indicated. The results show the importance of open-cycle simulations in automotive researches.

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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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In the present work, multidimensional modeling of open-cycle process of OM355 engine was developed. Calculations for computational mesh were carried out. The results of the model were validated by experimentally measured in-cylinder pressure and the good agreement between calculations and measurements approved the trustworthy of numerical code. Results included pressure, temperature, emission and Rate of heat release diagrams were represented for the full cycle. Furthermore local flow field velocity vectors were indicated. The results show the importance of open-cycle simulations in automotive researches.

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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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If an air flow is injected into a liquid fluid, many ambulant air bubbles are formed inside the fluid. Air bubbles move inside the liquid fluid because of the buoyancy force, and the mobility of these air bubbles makes sizable commixture and turbulence inside the fluid. This mechanism was employed to enhance the heat transfer rate of a horizontal double pipe heat exchanger in this paper. However it can be used in any other type of heat exchanger. Especially, this method can be expanded as a promising heat transfer improvement technique in automotive cooling system, for instance in radiator which contains of water or other liquid fluid. Bubbles were injected via a special method. Present type of air bubbles injection and also the use of this mechanism for double tube heat exchanger have not been investigated before. Results are reported for varying bubble inlet parameters. The main scope of the present work is to experimentally clarify the effect of air bubble injection on the heat transfer rate and effectiveness through a horizontal double pipe heat exchanger.

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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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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.