Automotive Science and Engineering

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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.

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This work investigates the effects of hydrogen addition to compressed natural gas (CNG) on combustion characteristics and emission reduction using a closed cycle simulation with exact geometry of piston and cylinder head. The effect of equivalence ratio on combustion characteristic were investigated using a spark ignition (SI) engine fueled with CNG and addition of 10% _vol, 15% _vol and 20%_vol hydrogen. Two different speed of 1500 and 3000 rpm have considered at full load condition. The modeling includes ECFM combustion model combined with K-ζ-f turbulent modeland has been done by AVL Fire software. Different volume fraction of Hydrogen with different excess air modeled and validated with experimental data. The validation procedure included in-cylinder pressure profile, maximum pressure, angle of maximum pressure, indicated mean effective pressure, and carbon monoxide (CO) emission showing a good agreement with the experimental results. The value of the peak pressure increases by hydrogen addition and it takes place sooner as the hydrogen volume fraction increases. However, the mean effective pressure drops 3.5%, 7% and 15% for HCNG 10, HCNG15 and HCNG20, respectively. CO emission decreases by increasing the hydrogen volume fraction. The results also indicate that hydrogen addition in lean combustion causes more CO reduction compared to the fuel-rich mixtures.

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Due to very low PM and NOx emissions and considerable engine efficiency, dual-fuel combustion mode such as RCCI strategy attracted lots of attention compared to other combustion modes. In this numerical research work, the impacts of direct injection timing and pressure of diesel fuel on performance and level of engine-out emissions in a diesel-butanol RCCI engine was investigated. To simulate the combustion process, a reduced chemical kinetic mechanism, which consists of 349 reactions 76 species was used. The influence of thirty-six various strategies based on two diesel spraying characteristics such as injection pressure (650, 800, 1000, and 1200 bar) and diesel spray timing (300 to 340 CA with 5 CA steps) have been examined. Results indicated that, under the specific operating conditions like 1000-bar spray pressure by direct injection at 45 CA BTDC and the spray angle of 145 degrees, the level of cylinder-out pollutants such as CO (up to 26%), NOx (about 86%), PM (by nearly 71%) and HC (about 17.25%) have been simultaneously reduced. Also, ISFC decreased by about 2.3%, IP increased by about 2.4%, and also ITE improved by nearly 2% compared to the baseline engine operating conditions.

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This paper presents low cycle fatigue (LCF) life prediction of an engine exhaust manifold. First Solidworks software was used to model the exhaust manifolds. Then Ansys Workbench software was used to determine stress and fatigue life based on Morrow and Smith-Watson-Topper (SWT) approaches. Thermal fatigue (TMF) of the engine components easily happens due to excessive temperature gradient and thermal stress. Modern exhaust systems must withstand severe cyclic mechanical and thermal loads throughout the whole life cycle. The numerical results showed that the temperature and thermal stresses have the most critical values at the confluence region of the exhaust manifolds. This area was under low cycle fatigue. After several cycles the fatigue cracks will appear in this region. The results of the finite element analysis (FEA) correspond with the experimental tests, carried out in references, and illustrate the exhaust manifolds cracked in this region. Finite element (FE) simulation proved a close correlation between Morrow and SWT criterions results. The lifetime of this part can be determined through finite element analysis instead of experimental tests.
 

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Reactivity control compression ignition (RCCI) engines have demonstrated high-efficient and clean combustion but still suffer from ringing operation at upper load and production of unburned hydrocarbon (uHC) and carbon monoxide (CO) emissions at lower load. In this study, statistical analysis and experimental testing were conducted to consider the effects of input parameters such as intake temperature (T_in), equivalent ratio (Φ) and engine speed on emissions, combustion noise and performance of a 0.5 liter RCCI engine using response surface method (RSM) with the aim to minimize emissions and combustion noise and to maximize parameters of performance. The developed models for measured responses like uHC, CO, nitrogen oxides (NOx) and calculated responses such as indicated mean effective pressure (IMEP) and combustion noise level (CNL) were statistically considered to be significant by analysis of variance (ANOVA). Interactive effects between Tin, Φ and engine speed for all operating points were analyzed by 3-D response surface plots. The results from this study indicated that at optimum input parameters, the values of uHC, CO, NOx, IMEP and CNL were found to be 90.3 (ppm), 106.8 (ppm), 248.2 (ppm), 11.7 (bar) and 87 (db), respectively. The models were validated by confirmatory tests, indicating the error in prediction less than 5%.

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HCCI engines have become the attention of research lately due to their advantages in reducing the emissions level, and their fuelling ability with alternative fuels. For this purpose, a single cylinder diesel engine with a port fuel injector and heated intake air were used to operate the HCCI engine at 2700 rpm using four different blends of POB biodiesel. The parameters varied for the study were different λ and intake air temperature. When using diesel fuel on HCCI mode, it is found that the engine power, torque, and BTE are lower and fuel consumption is higher compared to conventional Compression Ignition Direct Injection (CIDI) mode. The in-cylinder pressure pattern for HCCI mode shows that the combustion is advanced, and the in-cylinder pressure peak is higher at rich mixture compared to CIDI mode. The in-cylinder pressure decreases in the case of higher amount of biodiesel. Combustion intensity for biodiesel fuel is lower, which affects the heat release rate, whereas a high intake temperature triggers the combustion easily, enhances the fuel mixture auto-ignition proses. Increasing the amount of biodiesel will increase the NOx emissions insignificantly, however it is still lower than that of CIDI. POB based biodiesel improved the emissions of HCCI engines.

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Diesel engines are the most trusted sources in the transportation industry. They are also widely used in the urban transportation system. Most pollutants are related to these engines. Therefore, it is important to increase the performance and reduce exhaust emissions of these engines. Alternative fuels are key to meeting upcoming targets.
An experimental and numerical study was performed to investigate the effect of diesel fuel and hydrogen addition to diesel fuel from 0 to 30% on performance and exhaust emissions. Also in this research for changing diesel fuel, an indirect injection engine converted to direct injection engine. The simulation study was conducted by Star cd codes and experimental investigation was carried out on a diesel engine (Perkins 1103A-33TG1), three- cylinders, and four-stroke with maximum engine power 72.3hp at 1800 rpm. The results from this study showed that the increase of hydrogen to diesel fuel improves the thermal efficiency, resulting in lower specific fuel consumption. Also, the results showed that adding hydrogen until 30%, the cylinder pressure increase by about 9% and occurred the delay of peak pressure about 8 degrees of a crank angle compared to diesel fuel. The other obtained results in emission with 30%H2+Diesel showed the soot emission reduced 11.3%, HC and CO reduced nearly 36%, but NOx increased by about 8.3% due to high combustion temperature.

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Surface texturing modifications improve the tribological performance parameters. In parallel slider bearings with a micro-grooved textured surface, the effects of the Reynolds number and the texture aspect ratio at constant texture density have been studied; however, the texture density variation's effects on the tribological performance have not been investigated yet. The focus of this study is on the texture density variation in micro-grooved parallel slider bearings. The numerical analysis approach was utilized to perform a more in-depth understanding of texture density variation on the two-dimensional pressure distribution, skin friction coefficient, and recirculation zones in micro-grooves and the objective of flow functions such as load-carrying capacity and friction coefficient. In order to validate using the current CFD model for analyzing hydrodynamic bearings, a comparison with the published theoretical paper results was presented. The results were in good agreement with the published theoretical predictions. In a variety of aspect ratios, the texture densities led to an upgrade tribological performance. Results showed remarkable improvements in frictional response with texture density, and an optimal texture density exists. Finally, it was observed that the optimal micro-grooves texture density depends on the texture aspect ratio, while it is independent of the sliding velocity.

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Many efforts have been made to increase power and reduce emissions from internal combustion engines. For this purpose, the internal combustion engine subsystems are examined via many studies, and the effective parameters in each of them are analyzed. One of these subsystems is the air inlet and outlet to the combustion chamber, the most important part of which is the manifold. In the present study, using one-dimensional modeling of the OM457 heavy diesel engine in the GT SUITE software environment, the effect of geometric parameters of cylinder runner’s length - cylinder runner’s transverse distance as well as plenum’s depth on the performance and the emissions of this engine has been investigated. During this study, it was concluded that increasing the volume of the plenum not only improves the engine’s output but also reduces the emission of pollutants produced. Also, increasing the length of the cylinder runner increased the engine power. The change in the transverse distance of the cylinder runners did not have a significant effect on the power and pollutants of the sample engine. It was also observed that in similar geometric changes, the effect of changing the input manifold is significantly greater than the output manifold level.

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The confluence area cracks is most important durability problems in internal combustion engines. The aim of this article is a thermo-mechanical analysis for exhaust manifold using elasto-viscoplastic chaboche model. The Chaboche model was selected for the elasto-viscoplastic model including a kinematic hardening plastic law coupled with the Norton creep equation. The modeling, meshing and analyzing was performed on a finite element model of the exhaust manifold in ABAQUS software. In order to increase the accuracy of finite element analysis (FEA) results, temperature-dependent of material parameters was considered. The results of mechanical-thermal analysis showed that the temperature maximum and stress is visible in the confluence area. Obtained FEA results proved the manifold gasket leak is another region of critical that has to sustain the expanding and contracting of the heated exhaust manifold metal. The results of the modal analysis proved that the maximum strain energy density and total strain energy exist in the confluence area. The results of the thermo-mechanical analysis are compared with the real sample of the damaged exhaust manifold to evaluate the properly results, and it has been shown that serious identified zones correspond to the failure areas of the real sample.

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In this paper, to address the problem of using displacement sensors in measuring the transverse vibration of engine accessory belt, a novel non-contact method based on machine vision and Mask-RCNN model is proposed. Mask-RCNN model was trained using the videos captured by a high speed camera. The results showed that RCNN model had an accuracy of 93% in detection of the accessory belt during the test. Afterward, the belt curve was obtained by a polynomial regression to obtain its performance parameters. The results showed that normal vibration of the center of the belt was in the range of 2 to 3 mm, but the maximum vibration was 8.7 mm and happened in the engine speed of 4200 rpm. Also, vibration frequency of the belt was obtained 124 Hz. Moreover, the minimum belt oscillation occurred at the beginning point of the belt on the TVD pulley, whereas the maximum oscillation occurred at a point close to the center of the belt at a distance of 16 mm from it. The results show that the proposed method can effectively be used for determination of the transvers vibration of the engine accessory belts, because despite the precise measurement of the belt vibration at any point, can provide the instantaneous position curve of all belt points and the equation of the belt curve at any moment. Useful information such as the belt point having the maximum vibration, belt slope, vibration frequency and scatter band of the belt vibration can be obtained as well.

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In the current study, the hydrogen-addition influence on the performance of an SI engine using a gasoline-ethanol blend is investigated numerically. The simulation and validation of the model are carried out in order to evaluate the engine performance using conventional gasoline (G100) and the blend of gasoline and ethanol (G75E25). Furthermore, the hydrogen is added to the gasoline–ethanol blend (G50E25H25) to improve the engine thermal efficiency and reduce the amount of brake specific fuel consumption (BSFC) which leads to the reduction in greenhouse gas (GHG) emissions. The brake specific carbon dioxide (BSCO₂) is also studied in this paper. Results show that the addition of hydrogen increases the brake power and thermal efficiency, moderates the BSFC, and decreases the maximum temperature of combustion chamber which reduces the production of greenhouse gases as well as BSCO₂. In comparison with pure gasoline, by using G50E25H25, the maximum temperature of in-cylinder gas decreased by 12.55%, 10.82%, and 13.43% at 2000, 4000, and 6000 rpm, respectively. It is also evaluated that the lowest amount of BSCO₂ is related to G50E25H25 in most of the engine speeds. The bio-fuel of G75E25 and pure gasoline are placed in next positions, respectively.

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Due to the complex geometry and thermos-mechanical loading, cylinder heads are the most challenging parts among all parts engines. They must endure cyclic thermal and mechanical loading throughout their lifetime. Cast aluminum alloys are normally quenched after solution treatment process to improve aging responses. Rapid quenching can lead to high residual stress. Residual stress is one of the main reasons for failure of cylinder heads. The effect of residual stress on the thermal stress and low cycle fatigue life (LCF) of cylinder heads was studied. For this goal, Solidworks software was used to model the cylinder heads. Then the thermo-mechanical analysis was performed to determine the temperature and stress field in ANSYS software.  Finally, the fatigue life analysis that considers residual stress effect was done. The results of finite element analysis (FEA) proved that the effect of residual stress in LCF is significant which is not negligible. Thus, residual stress must be considered in the thermo-mechanical fatigue analysis of the engines cylinder heads. The numerical results showed that the area where the maximum temperature and stress is occurred is where the least LCF is predicted.

 

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In this study, feedback neural networks namely Elman and Jordan are used for prediction of exhaust valve temperature for air cooled engines. Input-output data are extracted from an experimental setup including the valve mechanism of an air cooled engine. Inverse heat transfer problem applying the Adjoint problem is used to address the thermal flux through exhaust valve and seat. Elman and Jordan neural networks are used to predict the transient valve temperature using the experimental data. The results show that Elman and Jordan neural networks predicts well the transient exhaust valve temperature. However, Jordan neural network with training algorithm of Gradient Descent with Adaptive Learning Rate performs better with RMSE error of 16.3 for prediction of exhaust valve temperature.
 

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In this research, the effect of using three Nano fluids contains graphene oxide (GO), titanium oxide (TiO2) and aluminum oxide (Al2 O3) was analyzed on the heat transfer of the car radiator by experiment in physical conditions on the car engine. Distilled water and ethylene glycol (60:40) as the base fluid was companied with three nanoparticles contain graphene oxide, titanium oxide and aluminum oxide that each one separately with 0.1, 0.2 and 0.3 weight percent and flow rates of 10, 20, 32 and 40 liters per minute were used at normal engine temperature. After the temperature of the radiator cooling fluid reached 90 degrees Celsius and the fan was turned on for one minute, the results showed that increasing the weight percentage of nanoparticles to the base fluid increases the displacement heat transfer coefficient and most increase in the coefficient of heat transfer at 0.3 weight percent to an approximate value of 5.2% in aluminum oxide, 11.9% for titanium oxide and 28.7% for graphene oxide compared to the base fluid was received. With the increase in weight percentage, the pressure drop and Nusselt number increased.  The highest percentage increase in the radiator pressure drop for all three Nano fluids with 0.3 weight percentage and 2.2% for   aluminum oxide, 3.5% for Titanium oxide and 5.24% for graphene oxide were received.

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In this article, the effect of the usage of variable speed electric water pump on the cooling system of a type of passenger car engine has been investigated. The engine water circulation in most of today's cars uses a mechanical method, the power required for its circulation is provided by a belt with a ratio of 1:1 from the crankshaft. This action makes the changes of the water pump speed a function of the engine speed and there is no control over it. One way to solve this problem is to use an intelligent thermal management system. In this method, some components of the cooling system, including the electric water pump, are controlled based on the working conditions and engine temperature. In this research, GT Suite and Simulink software were used simultaneously, and for this purpose, the engine cooling circuit with a mechanical water pump was simulated in GT Suite software and the accuracy of laboratory values was verified in terms of heat transfer. Then the mechanical connection of the water pump was disconnected and the water pump circuit was controlled with an electric motor. In the next step, in order to obtain the control pattern, the electric water pump was replaced with the mechanical water pump in the simulation pattern. The results of the software and experimental simulations of the intelligent cooling system showed a 13.4% reduction in engine warm-up time.