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Considering the gradual reduction of fossil fuel resources and their role in environmental issues, biodiesel-derived products have received much attention as fuel additives to enhance their properties and reduce emissions. The present work reports the engine performance and emission characteristics for a fuel blend consisting of solketal, a derivative of glycerol and gasoline. In this study, 5–10 vol% solketal was mixed with gasoline by ultrasonic processor to prepare a solketal-gasoline fuel blend. The blending of additives will affect the volumetric transport properties as well as the combustion quality of the fuel. Some important properties like thermal conductivity, surface tension, adiabatic compressibility, relative association, and intermolecular free path length were measured at different temperatures by measuring the ultrasonic velocity in the fuel blend. Four-stroke SI engine performance was studied in terms of brake-specific fuel consumption (BSFC) and brake thermal efficiency (BTE). BSFC increases by 15%, and BTE shows a marginal reduction of about 5.39% at 28.13 N·m torque with a 10% solketal-gasoline blend. The exhaust analysis indicates that CO emissions decrease and NOx and CO2 increase compared to pure gasoline as fuel, the brake thermal efficiency indicates a marginal reduction of about 5.39% for 10% solketal. [ABSTRACT FROM AUTHOR]

Simultaneous measurements of high-speed high-resolution particle image velocimetry near the piston top with spatial resolution of 152 × 76 μ m at 24 kHz and a micro-electro-mechanical-systems (MEMS) heat flux sensor on the piston surface was conducted in a motored optical gasoline engine with enhanced tumble flow for 2000 rpm. Characteristics of mean velocity profiles are discussed based on fitting to the turbulent and laminar boundary layers with conditioning by momentum. It has been found that the velocity profile of high momentum tends to be close to that of turbulent boundary layer, while its probability is not large. Cross correlation between maximum heat flux in each cycle and velocity in the piston-surface normal direction shows that heat flux is 3 CAD behind the velocity, which corresponds to about 0.25 ms. Also it is found that the correlation coefficient shows higher value at 0.50 mm from the piston wall rather than that at 0.27 and 0.12 mm with the delay of 3 CADs for heat flux. Furthermore, cross correlation coefficient of fluctuating components of heat flux and velocity shows also the similar tendency. [ABSTRACT FROM AUTHOR]

In an ideal conditions, three-way catalytic converters have a structure that will convert almost all of the harmful exhaust emissions. However, these conditions are not valid for cold start and idle conditions. Especially in cold weather, people wait for a while at the idle speed even though it is not a good way to warm up the engine. In this period, since the required temperature to reach light-off values are not provided, the emission released to the environment is at the highest level. The effects of preheating of the catalytic converter have been investigated in order to minimize the exhaust gases emitted under cold and idle working conditions and to meet the Euro standards as soon as possible after the emission release starts. In this experimental study, preheating of 1060, 1253 and 1493 Watt energy was applied to the exhaust line before the three-way catalytic converter at the cold start and idle conditions. Preheating was started when the engine started running. In the experiments, temperature and emission values were obtained at the catalytic converter inlet and outlet at idle conditions (1000 rpm) for about 430 seconds. The effects of inlet temperatures of exhaust gases on HC and CO emission behavior and converter conversion efficiency were investigated. When 1060, 1253 and 1493 Watt preheating are applied to the exhaust line, the times for reaching the light-off for HC and CO emissions occur at 395, 295, 220 and 369, 277, 200 seconds, respectively. However, when preheating is not applied, the catalytic converter has not been able to reach the light-off within the specified time. Finally, the EURO VI standard could not be achieved for the specified period without preheating. However, when the preheating load was set to 1493 Watt, EURO VI standards were achieved at the end of 310 and 285 seconds preheating times for both HC and CO emissions. [ABSTRACT FROM AUTHOR]

There has been extensive research on efficient energy conversion systems which also includes turbocharging the automotive SI engine. This research focuses on comparing the thermodynamic aspects of the turbine at different boost pressures at maximum engine torque and speed regions. A naturally aspirated CNG SI engine developing 15.5 kW at 3400 rpm was converted to a turbocharged LPG engine at the compression ratio of 8.5:1. The turbine performance was evaluated using ANSYS CFX numerical simulation tool and results were validated. The simulation study reveals that 1.3 bar boost pressure has a higher enthalpy generation and also has minimal Mach number than 1.5 bar signifying the effects of exhaust blowdown. Further, the experimental study was carried out at different boost pressures. The results show that at 1.3 bar, the turbine efficiency was higher with reduced heat transfer rate to the compressor which was due to reduced friction work compared to 1.5 bar which altogether improved the engine performance. This is also evident from the minimal COV of IMEP for 1.3 bar. On the whole, the turbine exhibited better performance for 1.3 bar and resulted in reduced thermal loading. [ABSTRACT FROM AUTHOR]

This paper is for the investigation on the turbulence kinetic energy distribution according to the design parameters of the intake system. The design parameter to be discussed is the intake valve angle. For this purpose, particle image velocimetry was introduced into the steady flow bench, in which four engine heads with 11, 16, 21 and 26 ° valve angles were evaluated changing valve lift. The experiment was conducted at 1.75 B evaluation position. The effect of valve angles and lift was analyzed by the planar flow characteristics of in-cylinder flow and the turbulence kinetic energy variation along the radial direction. 11, 16, and 21 ° have high turbulence kinetic energy near the cylinder wall with the highest flow velocity, and the turbulence kinetic energy around the swirl center is relatively low, indicating the same qualitative characteristics. 26 ° tends to be differentiated from other valve angles, and spatially very complex and fluctuating flow occurred. Complex turbulence kinetic energy distribution pattern appears at all valve angles, while the average turbulence kinetic energy shows a parabolic form as the valve lift increases because of the influence of the flow entry direction by the valve lift. [ABSTRACT FROM AUTHOR]

In the current time, sustainability and development of internal combustion engines is subjected to two kinds of threats which are fossil fuel depletion and environmental pollution. So, considerable efforts in the world have been exerted to develop and introduce alternative gaseous fuels to replace conventional fuel by partial or total replacement. In this study, the effect of adding acetylene to LPG-fuelled SI engine has been examined. This addition was with flow rates of 500, 750 and 1000 g/h for 25 % load and 1000 g/h for 50 % load, respectively. An experimental investigation has been carried out on 4 stroke, 4- cylinder, water-cooled spark ignition (SI) engine at constant speed (1500 rpm). Also, performance and emissions parameters have been tested at different excess air coefficients (λ = 0.8, 1, 1.2 and 1.7). As a result, it has been found optimum conditions which are the addition of 750 g/h acetylene for 25 % load (almost 41 % of the LPG-acetylene mixture at λ = 1.2) and 1000 g/h for 50 % load (almost 36 % of the LPG-acetylene mixture at λ = 1.5). In addition, hydrocarbon (HC) and carbon monoxide (CO) emissions decreased, while NO emissions increased when compared to that of baseline LPG operation. [ABSTRACT FROM AUTHOR]

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High octane number is one of the attractive properties of ethanol. Appropriate distribution of ethanol vapor concentrations in combustion chamber at the end of the compression process could suppress engine knock phenomena and hence improve performance and reduce pollutants emission of spark ignition engines fueled with gasoline–ethanol. This paper presents numerical simulation results of a new concept of octane number stratified charge mixture via dual injection of ethanol and gasoline. The principle of the concept is the optimization of fuel vapor concentrations distribution in combustion chamber to ensure high ethanol concentrations in zone risk of knock. Two dual-injection schemas have been studied: (1) port inject of gasoline and direct injection of ethanol and (2) separate port injection of gasoline and ethanol through two opposite intake manifolds. In the first case, direct injection of ethanol in axial direction did not result in ethanol concentration stratification. Stratification occurred when direct injection of ethanol in radial direction started later than port injection of gasoline. In the second case, significant stratification of ethanol concentrations occurred when ethanol injection started earlier than gasoline injection. In the combustion chamber, high ethanol concentration was found near the ethanol injection inlet port, whereas high equivalence ratio was found in the opposite side. Thus, the location of the spark plug in the opposite side of ethanol injector is optimal for improving anti-knock performance of engine fueled with ethanol gasoline at a given fuel ratio. [ABSTRACT FROM AUTHOR]

Abstract: Strategy of lean burn for reducing fuel consumption and emissions can be achieved by incorporating swirling motion in the incoming fluid entering the cylinder of the engine. In this backdrop, the application of shrouded intake valves gets the upper hand over the conventional poppet valve because of their capacity of producing intake-generated swirl flow. In the existing literature, a modified shrouded intake valve capable of producing significant amount of swirl with relatively smaller restriction to the incoming fluid has been reported. But, no work has been done to determine the effect of using modified shrouded intake valve in the emissions and performance of an SI engine. Thus, the effect of using the modified shrouded intake valve on the emissions and performance of an SI engine is studied and compared with that of poppet intake valve and 100°, 140°, and 180° shrouded intake valves. From the study, it is seen that the engine with modified shrouded intake valve produces lowest hydrocarbon and carbon monoxide emissions for maximum power condition, whereas the brake power, brake specific fuel consumption, and NOx emissions of the engine are quite close to the engine using poppet intake valve which is the best performing valve-engine combination for the same. For minimum brake specific fuel consumption condition, the engine with modified shrouded intake valve produces the highest brake power with the lowest brake specific fuel consumption, whereas the hydrocarbon and carbon monoxide emissions of the engine are similar to the engine using 180° shrouded intake valve which is the best performing valve-engine combination for the same.Graphical abstract: [ABSTRACT FROM AUTHOR]

Hydrogen is seen as one of the important energy vectors of the century. There are several alternatives procedures to produce it in high purity; aluminum corrosion could be considered as one of the most attractive ones. The use of hydrogen derived with this process in spark-ignition engines forms a promising approach to decarbonize hydrogen production and secure domestic energy supply. This study describes the development of an experimental setup for hydrogen production and testing a SI engine in the hydrogen-fueled mode. This paper investigates the effect of aluminum thickness (specific surface) and alkali concentration on the reaction rate. The experimental results show that an increase in alkali concentration and a reduction in aluminum thickness increase hydrogen production rate. The produced hydrogen was used as fuel for a single-cylinder spark-ignition engine. The experiments were conducted under various engine speeds. It is found that hydrogen combustion produces a lower exhaust gas temperature than gasoline, although NOx emissions decrease about 11 times compared to gasoline. It was expected that CO, CO2 and HC levels are zero when the engine is supplied with hydrogen, but it is found that there is a slight trace of CO, CO2 and HC due to combustion and evaporation of lubricant on cylinder walls. [ABSTRACT FROM AUTHOR]

In this investigation, performance and emission characteristics for enhancing LPG, hydrogen, and hydroxy with E20 were evaluated for the understanding of which fuel combination performs better in a gasoline engine. In the upper sequence, hydroxy-hydrogen-LPG could perform best in terms of brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC). The induction of gaseous fuel improves CO, CO2, and HC emission but increases the NOx emission. More concisely, the enhancement of hydroxy with E20 shows the best engine performance for highest BTE while lowest BSFC as well as lowest exhaust emissions (CO, HC, except NOx). [ABSTRACT FROM AUTHOR]

Knock is an abnormal combustion phenomena capable of causing serious damage to spark ignition engines, and is a constraint to reach the maximum potential of the engine, since strategies to increase power output and improve efficiency such as turbocharging, increased compression ratio and the advancement of spark timing, also increase the possibility of knock occurrence. Therefore, it is crucial to take into account the limits imposed by knock in the design and operating conditions of the engine when using an engine computational model. In this article a zero-dimensional two-zone engine model, coupled with a chemical kinetic model for knock detection through end-gas auto-ignition is developed and validated, for a natural gas engine. Given the importance of an accurate knock prediction, five heat transfer coefficient correlations are compared to find the most suitable to predict the knock occurrence, through calculation of a knock criterion. Correlations from Sitkei and Annand were the most suitable to predict this knock criterion for the experimental data used, and the Sitkei correlation was later tested in a parametric study to predict the effect of spark timing, compression ratio, equivalence ratio and inlet temperature in knock occurrence and intensity. Results were in accordance with real engine behaviour when knock occurs. [ABSTRACT FROM AUTHOR]

A reduced combustion kinetic model for the methanol-gasoline blended fuels for SI engines was developed. Sensitivity analysis and rate constant variation methods were used to optimize the kinetic model. Flame propagation, shock-tube and jet-stirred reactor systems were modeled in CHEMKIN. The laminar flame speed, ignition delay time and change in concentrations of species were simulated using the reduced kinetic model. The simulation results of reduced chemical mechanism agreed well with the relevant experimental data published in the literature. The experimental investigations on engine bench were also carried out. The in-cylinder pressure and exhaust emissions were obtained by using a combustion analyzer and an FTIR (Fourier transform infrared spectroscopy) spectrometer. Meanwhile, an engine in-cylinder CFD model was established in AVL FIRE and was coupled with the proposed reduced chemical mechanism to simulate the combustion process of methanol-gasoline blends. The simulated combustion process showed good agreement with the engine experimental results and the predicted emissions were found to be in accordance with the FTIR results. [ABSTRACT FROM AUTHOR]

An important intrinsic property of a combustible fuel, air, and burned gas mixture is its laminar burning velocity. The effect of laminar burning velocity on combustion is difficult to assess experimentally due to the difficulty in the measurement. In this study, an approach which uses the in-cylinder pressure traces, temperature and other in-cylinder variables for estimating the laminar burning velocity of a spark ignition engine is developed. In this model the flame velocity is calculated by quasi dimensional two zone thermodynamic combustion simulation. Laminar flame speed over a range of engine loads and at rated speed on a Royal Enfield single cylinder 350cc port fuel injected spark ignition engine are estimated and evaluated using available data given in the literature. For simulation, a code has been developed in MATLAB for computational speed and acceptable accuracy. [ABSTRACT FROM AUTHOR]

Detection and isolation of faults in the exhaust gas path of a turbocharged spark ignition (SI) engine is an essential part of the engine control unit (ECU) strategies to minimize exhaust emission and ensure safe operation of a turbocharger. This paper proposes a novel model-based strategy to detect and isolate an exhaust manifold leakage and a stuckclosed wastegate fault. The strategy is based on a globally optimal parameter estimation algorithm which detects a virtual hole area in the exhaust manifold. The estimation algorithm requires observation of the exhaust manifold's input and output flows. The input flow is estimated by a nonlinear Luenberger observer which is analytically shown to be robust to the faults in the exhaust manifold. The output flow of the exhaust manifold is estimated by a sliding mode observer. The designed fault detection and isolation (FDI) strategy is tested with the experimental data collected from a 1.7-liter turbocharged SI engine. The validation results show that the FDI strategy can successfully detect a leakage fault caused by a 5 mm hole in the exhaust manifold, and can identify the wastegate stuck-closed fault. [ABSTRACT FROM AUTHOR]

In this study, a thermodynamic cycle simulation of a conventional four-stroke SI engine has been carried out to predict the engine performance and emissions. The first law of thermodynamics has been applied to determine in-cylinder temperature and pressure as a function of crank angle. The Newton-Raphson method was used for the numerical solution of the equations. The non-differential form of equations resulted in the simplicity and ease of the solution to predict the engine performance. Two-zone model for the combustion process simulation has been used and the mass burning rate was predicted by simulating spherical propagation of the flame front. Also, temperature dependence of specific heat capacity has been considered. The performance characteristics including power, indicated specific fuel consumption, and emissions concentration of SI engine using gasoline and CNG fuels have been determined by the model. The results of the present work have been evaluated using corresponding available experimental data of an existing SI engine running on both gasoline and CNG. It has been found that the simulated results show reasonable agreement with the experimental data. Finally, parametric studies have been carried out to evaluate the effects of equivalence ratio, compression ratio and spark timing on the engine performance characteristics in order to show the capability of the model to predict of engine operation. [ABSTRACT FROM AUTHOR]

In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (AlO) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and compared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A maximum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved. [ABSTRACT FROM AUTHOR]

The influences of charge stratification on spark ignition (SI) engine combustion and NO emission were analyzed using a phenomenological model. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air-fuel charge, a dilution region without any combustible charge, and a mixing region lying between the core and the dilution region. Three mixture stratification parameters such as the extent of dilution in the mixing region, the extent of combustible charge in the mixing region, and the gradient of stratification in the mixing region were investigated. The results indicate that the extent of combustible charge in the mixing region could reduce in-cylinder NO formation significantly, compared with the extent of dilution in the mixing region. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation. [ABSTRACT FROM AUTHOR]

In this work, three-dimensional fuel-air mixing inside a conventional spark ignition engine cylinder is simulated under direct injection conditions. The motivation is to explore retrofitting of conventional engines for direct injection to take advantage of low emissions and high thermal efficiency of the direct injection concept. Fuel-air mixing is studied at different loads by developing and applying a model based on the Lagrangian-drop and Eulerian-fluid (LDEF) procedure for modelling the two-phase flow. The Taylor Analogy Breakup (TAB) model for modelling the hollow cone spray and appropriate models for droplet impingement, drag and evaporation are used. Moving boundary algorithm and two-way interaction between both phases are implemented. Fuel injection timing and quantity is varied with load. Results show that near-stoichiometric fuel-air ratio region is observed at different locations depending on the load. The model developed serves to predict the fuel-air mixing spatially and temporally, and hence is a useful tool in design and optimization of direct injection engines with regards to injector and spark plug locations. Simulations over a range of speed and load indicate the need for a novel ignition strategy involving dual spark plugs and also provide guidelines in deciding spark plug locations. [ABSTRACT FROM AUTHOR]

Combustion chamber crevices in SI engines are identified as the largest contributors to the engine-out hydrocarbon emissions. The largest crevice is the piston ring-pack crevice. A numerical simulation method was developed, which would allow to predict and understand the oxidation process of piston crevice hydrocarbons. A computational mesh with a moving grid to represent the piston motion was built and a 4-step oxidation model involving seven species was used. The sixteen coefficients in the rate expressions of 4-step oxidation model are optimized based on the results from a study on the detailed chemical kinetic mechanism of oxidation in the engine combustion chamber. Propane was used as the fuel in order to eliminate oil layer absorption and the liquid fuel effect. Initial conditions of the burned gas temperature and in-cylinder pressure were obtained from the 2-zone cycle simulation model. And the simulation was carried out from the end of combustion to the exhaust valve opening for various engine speeds, loads, equivalence ratios and crevice volumes. The total hydrocarbon (THC) oxidation in the crevice during the expansion stroke was 54.9% at 1500 rpm and 0.4 bar (warmed-up condition). The oxidation rate increased at high loads, high swirl ratios, and near stoichiometric conditions. As the crevice volume increased, the amount of unburned HC left at EVO (Exhaust Valve Opening) increased slightly. [ABSTRACT FROM AUTHOR]

The effects of pressure and temperature on the autoignition of propane and n-butane blends were investigated using a rapid compression machine (RCM), which is widely used to examine the autoignition characteristics. The RCM was designed to be capable of varying the compression ratio between 5 and 20 and minimize the vortex formation on the cylinder wall using a wedge-shaped crevice. The initial temperature and pressure of the compressed gas were varied in range of 720-900 K and 1.6-1.8 MPa, respectively, by adjusting the ratio of the specific heat of the mixture by altering the ratio of the non-reactive components (N2, Ar) under a constant effective equivalence ratio (øf=l.0). The gas temperature after the compression stroke could be obtained from the measured time-pressure record. The results showed a two-stage ignition delay and a Negative Temperature Coefficient (NTC) behavior which were the unique characteristic of the alkane series fuels. As the propane concentration in the blend were increased from 20 % and 40 % propane, the autoignition delay time increased by approximately 41 % and 55 % at 750 K. Numerical reduced kinetic modeling was performed using the Shell model, which introduced some important chemical ideas, represented by the generic species. Several rate coefficients were calibrated based on the experimental results to establish an autoignition model of the propane and n-butane blends. These coefficients can be used to predict the autoignition characteristics in LPG fueled SI engines. [ABSTRACT FROM AUTHOR]

A new evaporative cooling system for small four-stroke engines has been developed. Performance tests of a four-stoke single cylinder engine equipped with this evaporative cooling system have been carried out in the laboratory. Air removal rates from the closed coolant loop during the starting stage of the engine have been monitored for various engine operating conditions. In addition, data of the brake horsepower, the specific fuel consumption, heat loss to the coolant, cylinder-liner wall temperature and the wall heat flux have been obtained and were compared to those of the identical engine equipped with a conventional liquid cooling system. At a fixed air fuel ratio and under the MBT condition, the brake horsepower of the engine for the evaporative cooling system is enhanced compared to that for the liquid cooling system. The heat loss through the cylinder liner is decreased when the evaporative cooling system is adopted. The test result indicates several benefits of the evaporative cooling system such as faster warm up, better fuel economy and greater engine durability. [ABSTRACT FROM AUTHOR]