Automotive Science and Engineering

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The HCCI combustion process is initiated due to auto-ignition of fuel/air mixture which is dominated by chemical kinetics and therefore fuel composition has a significant effect on engine operation and a detailed reaction mechanism is essential to analysis HCCI combustion. A single zone-model permits to have a detailed chemical kinetics modeling for practical fuels. In this study a single-zone thermodynamic model with detail chemical mechanism is developed to investigate the effect of hydrogen addition to natural gas in a homogeneous charge compression ignition combustion and to analyze the performance and emissions of the HCCI engine. The effect of five different percentage of hydrogen added to natural gas ranging from 0 to 40 on HCCI combustion is investigated in this study. The results indicate that by increasing hydrogen portion in intake mixture, start of combustion advances and maximum temperature increase, but increasing in maximum pressure is negligible. Carbon’s included emissions such as Co, Co2 and unburned hydrocarbons decreases by increasing of hydrogen, and also, specific fuel consumption decreases. The result shows that hydrogen improves combustion characteristics of natural gas in an HCCI engine and leads to better performance and less emissions.

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Homogenous Charge Compression Ignition (HCCI) engines hold promise of high fuel efficiency and low emission levels for future green vehicles. But in contrast to gasoline and diesel engines, HCCI engines suffer from lack of having direct means to initiate combustion. A combustion timing controller with robust tracking performance is the key requirement to leverage HCCI application in production vehicles. In this paper, a two-state control-oriented model is developed to predict HCCI combustion timing for a range of engine operation. The experimental validation of the model confirms the accuracy of the model for HCCI control applications. An optimal integral state feedback controller is designed to control the combustion timing by modulating the ratio of two fuels. Optimization methods are used in order to determine the controller’s parameters. The results demonstrate the designed controller can reach optimal combustion timing within about two engine cycles, while showing good robustness to physical disturbances.

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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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Diesel exhaust particles are a complex mixture of thousands of gases and fine substances that contain more than 40 different environmental contaminants. Being exposed to these exhaust particles (called soot) can cause lung damage and respiratory problems. Diesel particulate filters are used in many countries for mobile sources as a legal obligation to decrease harmful effect of these fine particles. The size range of these particles is varied from 0.01 to 1 µm. Moreover, it takes a long time to be settled when they are outspread in atmosphere. In this paper, homogeneous plane standing waves are used to coagulate nano particles in order to achieve larger size which has a better gravitational settling. It means that fine particles are converted into a large one. Theoretical mechanisms are studied which led to experimental results in 155(db) and 160 (db). The results show that acoustic precipitators have a good performance in removing fine particles in diesel exhaust. Additionally, they indicate that at high pressure levels, the system has high efficiency for removing fine particles

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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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In spark ignition (SI) engines, the accurate control of air fuel ratio (AFR) in the stoichiometric value is required to reduce emission and fuel consumption. The wide operating range, the inherent nonlinearities and the modeling uncertainties of the engine system are the main difficulties arising in the design of AFR controller. In this paper, an optimization-based nonlinear control law is analytically developed for the injected fuel mass flow using the prediction of air fuel ratio response from a mean value engine model. The controller accuracy is more increased without chattering by appending the integral feedback technique to the design method. The simulation studies are carried out by applying severe changes in the throttle body angle to evaluate the performance of the proposed controller with and without integral feedback. The results show that the proposed controller is more effective than the conventional sliding mode controller in regulating the AFR without chattering.

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The subjects of heat transfer and cooling system are very important topics in the Internal Combustion Engines (ICE). In modern cooling systems, low weight, small size and high compactness are the critical designing criteria that requires heat transfer enhancement. Boiling phenomenon which is occurred in the water jacket of the ICE is one of the methods to increase heat transfer in the coolant system of an ICE. A research has been shown that parameters such as material, temperature, and roughness of the heated surface have direct effect on the rate of heat transfer in a boiling phenomenon. In this paper the potential of boiling phenomenon and the effect of the surface roughness on the amount of heat flux removed by the coolant flow in the engine water jacket is investigated experimentally. For this purpose the experiments was carried out in three different flow velocities and also three different surface roughnesses. Results show that the boiling and roughness of a hot surface will increase the heat removal significantly.

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In this paper, the development and optimization of Power Distribution Control Strategy (PDCS) have been performed for a Hybrid Energy Storage Systems (HESS) of a Series Hybrid Electric Bus (SHEB). A common PDCS is based on the use of Ultra-Capacitor (UC) pack. A new simple PDCS is developed as a battery based one. For the battery based PDCS, four parameters are introduced for tuning the PDCS performance. The Design of Experiment (DoE) method is utilized to optimize the parameters of the battery based PDCS for the driving cycles and the vehicle controllers. The results show the optimized battery based PDCS performance for some cases are better than the UC based PDCS performance. Vice versa, for some cases the performance of the UC based PDCS is better than the battery based PDCS. Finally, the costs rising from the HESS (about 66%) is reasonable when considering the over double increase in the battery life-time when using an appropriate PDCS.

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Robust control design of vehicles addresses the effect of uncertainties on the vehicle’s performance. In present study, the robust optimal multi-objective controller design on a non-linear full vehicle dynamic model with 8-degrees of freedom having parameter with probabilistic uncertainty considering two simultaneous conflicting objective functions has been made to prevent the rollover. The objective functions that have been simultaneously considered in this work are, namely, mean of control effort (MCE) and variance of control effort (VCE).The nonlinear control scheme based on sliding mode has been investigated so that applied braking torques on the four wheels are adopted as actuators. It is tried to achieve optimum and robust design against uncertainties existing in reality with including probabilistic analysis through a Monte Carlo simulation (MCS) approach in multi-objective optimization using the genetic algorithms. Finally, the comparison between the results of deterministic and probabilistic design has been presented. The comparison of the obtained robust results with those of deterministic approach shows the superiority robustness of probabilistic method.

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This study tries to redesign the interior design of inter-city bus in order to fulfill needs of Iranian User. The goal of this study is practically investigate how user centered design can be applied considering cultural needs of Iranian user. By defining common needs between cultural and physical aspects of Iranian user, the main focus was on improving the sitting condition of the traveler with intercity bus. Ergonomic redesign of the Bus Seat was the result of such a study

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Heat transfer in internal combustion engines is one of the most significant topics. Heat transfer may take place through thermal conduction and thermal convection in spark ignition engines. In this study, valve cover heat transfer and thermal balance of an air-cooled engine are investigated experimentally. The thermal balance analysis is a useful method to determine energy distribution and efficiency of internal combustion engines. In order to carry out experiments, a single cylinder, air-cooled, four-stroke gasoline engine is applied. The engine is installed on proper chassis and equipped with measuring instruments. Temperature of different points of valve cover and exhaust gases is measured with the assistance of K-type thermocouples. These experiments are conducted in various engine speeds. Regarding to the first law of thermodynamics, thermal balance is investigated and it is specified that about one-third of total fuel energy will be converted to effective power. It is also evaluated that for increasing brake power, fuel consumption will increase and it is impossible to prevent upward trends of wasted energies. In addition, it is resulted that, there is a reduction heat transfer to brake power ratio by increasing engine speed. Furthermore, it is found that, at higher engine speed, lower percentage of energy in form of heat transfer will be lost.

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In this paper, a three-axle bus rollover threshold and the effective parameters are studied. The rollover threshold is a speed that automotive is passing without occurring rollover. The objective is a determination of the heavy vehicle rollover critical speed while turning. For this purpose, a three-axle bus is studied. The dynamic equations related to rollover is extracted, and then rollover criterion, which is LTR (Load Transfer Ratio) in this paper, is obtained. The governing equations are simulated in MATLAB software and then the effect of the parameters such as steering rate, road curvature radius, road bank slope and automotive effective parameters on the rollover critical speed is studied. Prior to the investigation of these parameters, due to validation of the simulation model in MATLAB, a three-axle bus with specific parameters values is placed under various maneuvers with different conditions in TruckSim software then results are recorded. In order to validate, these results are compared with the results which are achieved from MATLAB. After validation, the relation between effective parameters in rollover stability and vehicle speed for desire maneuvers is obtained and it is illustrated in form of function. The results of this research work can be used in road threshold speed without huge computation costs and expensive tests.

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In this paper we aim to develop a predictive combustion model for a turbocharged engine in GT-Power software to better simulate engine characteristics and study its behavior under variety of conditions. Experimental data from combustion was initially being used for modelling combustion in software and these data were used for model calibration and result validation. EF7-TC engine was chosen for this research which is the first turbocharged engine designed and developed by IKCO and IPCO in Iran. After analyzing necessary theories for predictive combustion model and required steps for calibration of CombSITurb model in software, one final set of multipliers were calculated based on different sets derived for each engine speed and engine operation was simulated with this combustion model. In addition to improved predictability of engine model, comparing results of predictive model with non-predictive model shows better accuracy especially at lower engine speeds and less tolerance of results for each engine speed.

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The thermal balance analysis is a useful method to determine energy distribution and efficiency of internal combustion (IC) engines. In engines cooling concepts, estimation of heat transfer to brake power ratio, as one of the most significant performance characteristics, is highly demanded. In this paper, investigation of energy balance and derivation of specific heat rejection is carried out experimentally and numerically. Experiments are carried out on an air-cooled, single cylinder, four-stroke gasoline IC engine. The engine is simulated numerically and after validation with experimental data, the code is run to find out total and instantaneous thermal balance of engine. Results indicate that about one-third of fuel energy is converted to brake power and major part of energy is dissipated through exhaust and heat transfer. Experimental and numerical results show that by increasing engine speed, heat transfer to brake power ratio decreases. It is also observed that increasing engine speed leads to increase of exhaust power to brake power ratio. Finally two correlations for estimation of heat transfer and exhaust power to brake power ratios are obtained.

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This paper investigates 3D simulation of fluid flow in a centrifugal pump from the Detroit Diesel company to extract possible engine cooling trends.  The velocity and pressure profile of water, the coolant, is analyzed and the characteristic curves of the pump are derived. This provides a useful evaluation of the pump performance at all working conditions. For this aim, a computational fluid dynamic model is developed using ANSYS CFX for a wide span of flow rates and a number of shaft angular velocities. The variation of constituting parameters are examined using dimension-less descriptive parameters of flow, head and power coefficients, finally, the efficiency of the pump is examined. In this analysis, sst-k-w turbulent model is employed which is a combination of two different models for pumps and turbomachines. Numerical results show that prolonged cooling duty cycles of the vehicle should accompany a flow factor of 10%. In addition, the peak of the vehicle’s loading should match the maximum efficiency of the pump that can be increased to 62% by augmentation of flow rate and flow coefficient.

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In this paper, a computational in-cylinder analysis of HCCI diesel engine was carried out using IC Engine FORTE (ANSYS 18.2) software package. The analysis used pre-defined industry standard CHEMKIN format for specifying a chemical reaction mechanism during the combustion duration. The investigation was carried out for the effects of various EGR mass percentages on the thermal and emission characteristics of a diesel engine running on HCCI mode of combustion. It was observed that an increase in EGR concentration resulted in the decrease in peak in-cylinder pressure and temperature and it was also found that when the EGR rates were increased beyond 75% there was no combustion happening within the cylinder. A considerable decrease in the NO_x emissions was found with an increase in EGR mass percentage with almost negligible values when the EGR rates were increased beyond 50%, however there was a slight increase in un-burnt hydrocarbons.

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In internal combustion engines, exhaust valve and its seat gain considerable temperature as the hot gases exit through them. So, the rate of heat transfer should be under control. In this study, the contact heat transfer coefficient has been estimated. An experimental study on an Air-Cooled internal combustion engine cylinder head has been considered. Using the measured temperatures of sensors located in specific locations of the exhaust valve and the seat and the method of linear extrapolation, the surface contact temperatures and constant and periodic contact heat transfer coefficient were calculated. Also, a sensitivity analysis has been done to study the effects of different parameters of contact pressure, contact frequency, heat flux and cooling air speed on thermal contact conductance. The results show that between the major four considered parameters, the thermal contact conductance is more sensitive to the contact pressure, then the contact frequency, heat flux and the cooling air speed are the most affecting parameters on thermal contact resistance.

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The purpose of this study is to investigate the effect of radiation heat transfer on temperature distribution and heat flux to the walls of a diesel engine. A diffusion flame is modeled in a simple cylindrical geometry and boundary conditions are defined. A specific solver which can model the turbulent diffusion flame by considering radiation in participating media is used to solve the problem. The solver is verified using experimental data of a furnace. The results show that with considering radiation and non-gray effects in the model, the flame temperature is calculated higher than that with ignoring these effects (about 11% in problem considered in this study).