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This paper presents an experimental study investigating the effects of water-in-gasoline emulsion (WiGE) on the performance and emissions of a turbocharged PFI spark-ignition engine. The emulsions were produced through a micro-channels emulsifier, potentially capable to work inline, without addition of surfactants. Measurements were performed at a 3000 rpm speed and net Indicated Mean Effective Pressure (IMEP) of 16 bar: the engine point representative of commercial ECU map was chosen as reference. In this condition, the engine, fueled with gasoline, runs overfueled (λ = 0.9) to preserve the integrity of the turbocharger from excessive temperature, and the spark timing corresponds to the knock limit. Starting from the reference point, two different water contents in emulsion were tested, 10% and 20% by volume, respectively. For each selected emulsion, at λ = 0.9, the spark timing was advanced from the reference point value to the new knock limit, controlling the IMEP at a constant level. Further, the cooling effect of water evaporation in WiGE allowed it to work at stoichiometric condition, with evident benefits on the fuel economy. Main outcomes highlight fuel consumption improvements of about 7% under stoichiometric mixture and optimized spark timing, while avoiding an excessive increase in turbine thermal stress. Emulsions induce a slight worsening in the HC emissions, arising from the relative impact on combustion development. On the other hand, at stoichiometric condition, HC and CO emissions drop with a corresponding increase in NO. [ABSTRACT FROM AUTHOR]

This work presents the development and use of a comprehensive, quasi-dimensional, two-zone combustion model aiming at predicting the combustion characteristics, performance, nitric oxide (NO), and carbon monoxide (CO) emissions of high-speed spark-ignition (SI) engine. The model is validated against pertinent data from experimental investigation conducted at the authors' laboratory on experimental, Ricardo E6, mono-cylinder, high-speed SI engine, having the capability to operate over a wide range of compression ratios (CR) (variable compression ratio engine, VCR) and (fuel-air) equivalence ratios (EQR). In this work, a comparison between experimental and computational results is carried out for the engine fueled with gasoline, operated under various CR and EQR values at wide open throttle (WOT) position. The developed model is a two-zone one consisting of an unburned and a burned zone. It simulates the combustion process by following closely the flame front movement and development in the combustion chamber, at each instant of time, taking into account the history of pressure, temperature, and local composition. The unburned mixture turbulent entrainment into the burning zone through the flame front area is considered with its subsequent combustion. The flame front movement determines also the wetted areas and the volumes in the two zones. To determine the concentration of the chemical species equilibrium model is employed, while pertinent chemical kinetics schemes are used for computing NO and CO concentrations. The obtained pressure, mass fraction burned (MFB), mass fraction entrained (MFE), temperatures in the two zones, and NO and CO histories assist in the understanding of the complex phenomena involved, while they facilitate the interpretation of performance indices and knocking tendency. They shed light into the underlying physical and chemical mechanisms influencing the related SI engine performance and emissions attributes. The computed results are found to be in good agreement with the respective experimental ones. [ABSTRACT FROM AUTHOR]

To develop an effective control and monitoring scheme for automotive engines, a precise knowledge of the parameters and unmeasurable states of the nonlinear model capturing the overall dynamics of engines is of utmost importance. For a new vehicle out of the assembly line, the nonlinear model has constant parameters. However, in the long run, due to regular wear-and-tear, and for other unpredictable disturbances, they may change. The main challenges are how to obtain the information of parameters and states under the influence of process noise and measurement noise. To address these challenges, we present a new integrated state and parameter estimation algorithm in this paper for spark ignition (SI) engines based on the constrained unscented Kalman filter and the improved recursive least square technique. The system under consideration is a highly nonlinear mean value SI engine model consisting of the throttle, intake manifold, engine speed dynamics, and fuel system. The performance of the proposed algorithm in terms of root-mean-square-error and robustness with regards to initial conditions and random noises is analysed through exhaustive simulation scenarios considering constant, and time-varying parameters. In addition, the performance of other state-of-the-art estimation algorithms is also compared with that of the developed integrated algorithm. [ABSTRACT FROM AUTHOR]

More stringent emission norms are implemented all over the world to protect the environment from vehicular pollution. Biofuels are one of the best alternative solutions to reduce cost and environmental pollution. Among many alternate fuels, alcohol is a leading fuel used in automotive spark-ignition engines in pure or blended form. The capability of methanol to substitute gasoline has been known for a long time. This paper aims to systematically review methanol–gasoline blend with higher alcohol additives (ternary blends) as a transportation fuel in unmodified automotive spark-ignition engines. This review summarizes the previous research in methanol–gasoline blends with and without additives on spark-ignition engines' performance and emission characteristics. Many researchers found that methanol–gasoline blended fuels improve engine performance and emissions. Generally, alcohols burn very effectively and produce only fewer emissions compared to gasoline. Still, lower alcohol may cause some problems such as increased specific fuel consumption, phase separation and corrosion. These problems are further optimized using higher alcohol additives through improved energy content, kinematic viscosity, corrosion resistance, water tolerance and phase stability. Several research studies have been carried out in the past years, which focused mainly on single alcohol blended fuels for spark-ignition engines. Thus, a comprehensive survey of performance, combustion and emission characteristics of methanol–gasoline blended fuel with higher alcohol additives is necessary to show the potential of ternary blends in automotive engines. [ABSTRACT FROM AUTHOR]

Biodiesel, as an alternative fuel, has gained wide interest in recent years. However, despite the countless benefits, the enormous generation of glycerol-waste and higher production costs have been causing severe challenges to both the environment and the biodiesel economy's survival. With the focus on maintaining its sustainability, the proper valorization of the crude glycerol is of vital importance. The objective of the present study is to harness and transform glycerol (a by-product of biodiesel) to triacetin and utilize it further as a fuel additive for spark ignition (SI) engine. Triacetin is a valuable compound of bio-based origin, having good anti-knock properties and higher oxygen content. Test fuels containing different blends of gasoline, methanol and triacetin were prepared and compared with neat gasoline. The Response Surface Methodology (RSM) based multi-objective technique was selected to optimize the engine output parameters like BTE, CO, CO2, HC and NOx emissions. The results indicate that the engine operating at 1.17 kW brake power and containing 90.73% gasoline, 4.94% methanol and 4.31% triacetin (by vol.) were found to be the optimum input parameter combinations which shows maximum BTE and lowest engine exhaust emissions as compared to other fuel blends. The estimated economic analysis of small-scale plants was also carried out, revealing that about 4.2% of revenue per kg of triacetin selling can be generated by running biodiesel and triacetin production analogously. Among various alternatives probed, the acetylation of glycerol to triacetin appears to be the ideal solution. It can serve the multiple purposes of reducing vehicular emission and improving the economic viability of burgeoning biodiesel industries and creating new opportunities, livelihoods, and jobs for humanity. [ABSTRACT FROM AUTHOR]

Today, the demand for higher output efficiencies, lower fuel consumption, and ever reduced emissions has been rising. Due to its availability, one promising alternative is the applying of hydrogen in internal combustion engines. In this study, the initial efforts concentrated on combine relationships of input and output parameters of hydrogen compressed natural gas spark-ignition engine. The quadratic regression models were conducted for all six responses: torque, carbon monoxide, brake-specific fuel consumption, methane, nitrogen oxides, and total hydrocarbon through response surface methodology and tested for adequacy by analysis of variance. The multi-objective desirability approach employed for the optimization of input variables, namely, the hydrogen compressed natural gas ratio, excess air ratio (l), and ignition timing (ui). Also, two factors, that is, manifold absolute pressure and engine speed, were fixed at 105 kPa and 1600 r/min, respectively. Results indicate that the optimal independent input factors are equal to l of 1.178, hydrogen compressed natural gas ratio of 25.98%, and ui of 18 °CA before top dead center. Also, the optimal combination of responses is as follows: brake-specific fuel consumption of 219.334 g/kWh, the torque of 395 N m, 30.189 g/kWh for nitrogen oxides, carbon monoxide equal to 5.093 g/kWh, total hydrocarbon of 0.633 g/kWh, and 0.572 g/kWh for methane. This study provided the significance of response surface methodology as an attractive technique for investigators for modeling. In this regard, the response surface methodology modeling and multi-objective desirability approach can be utilized to predict the emission and performance characteristics of the hydrogen compressed natural gas engines minutely. [ABSTRACT FROM AUTHOR]

Summary Hydrogen is one of the most promising alternative fuels for the transportation industry. The use of hydrogen to enable lean burn in internal combustion engines is an attractive solution for reducing CO2 emissions from two points of views: the substitution of carbon‐based fuels and the increased thermal efficiency due to lean operation. Combining this strategy with the passive pre‐chamber ignition system with gasoline/hydrogen blends is even more interesting. The main limitations of the passive pre‐chamber concept in a high compression ratio spark‐ignition engine were shown through engine experiments. A numerical study was then performed to evaluate the chance of extending the dilution limit by using hydrogen along with this technology. Results show how the use of hydrogen provides considerable benefits in the main chamber combustion process by enhancing the thermo‐chemical properties of the mixture, increasing the flame speed, and improving the flame structure. Using an adequate gasoline‐hydrogen blend proved to enable optimum burning rates at lean conditions, leading to a relevant thermal efficiency gain. [ABSTRACT FROM AUTHOR]

This paper describes the possibility of replacing the single-fuel spark-ignition engines (SFSIE) fuelled with gasoline by the dual-fuel spark-ignition engines (DFSIE) fuelled with bioethanol and biogas. GASEQ software was used to estimate the combustion exhaust gases of the bioethanol, biogas and gasoline with 27% ethanol and 20% ethanol in order to calculate the energy-ecological efficiency of the DFSIE and the SFSIE. The tank-to-wheel (TTW) emissions were calculated to analyse the amount of carbon dioxide (CO2) emitted per kilometre and compared to the tailpipe emissions standards defined by the United States and European Union. The results showed that the energy-ecological efficiency found for the DFSIE fuelled with 50% bioethanol and 50% biogas was higher than that found for the SFSIE fuelled with gasoline. However, the TTW emissions of the DFSIE in category 2.0 presented the lowest emission values when compared to the other categories. As can be seen from the results obtained in the present study, the use of the DFSIE fuelled with bioethanol and biogas reveals the effect on the energy-ecological efficiency and the TTW emissions. The findings of this study can be used as a guide for public policy makers in order to assist their planning of sustainable urban mobility programs. [ABSTRACT FROM AUTHOR]

In gasoline engines, the spark timing is often advanced to increase fuel economy under certain heavy load engine operating conditions. As a compromise between the risk of knock and the power output, spark timing is regulated at the boundary where a low knock probability is tolerated. Due to the stochasticity of binary knock events, it is necessary to have a large number of engine cycles for probability estimations, which can slow down the response speed of a controller to operating condition changes. To speed up the spark timing regulation and to reduce the spark timing variance, in this article, a knock probability feedforward map learning method and a spark timing control method are proposed under a unified framework. A learning method that applies the beta distribution is the key contribution of this work. The beta distribution in the map learning part is used to describe knock probabilities with uncertainties and to determine the next engine operating condition for sampling and map learning. In the spark timing method, the beta distribution is applied in the conventional control method to adjust the control gains. The proposed methods are experimentally validated on a test bench equipped with a production Toyota 1.8 L, 4-cylinder SI engine. [ABSTRACT FROM AUTHOR]

The cyclic variability in a spark-ignition (SI) engine is examined fueled with methane/hydrogen blends with the use of an in-house computational fluid dynamics (CFD) code. A recent methodology is followed, which has been developed with the main aim at providing accurate predictions of the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) in a fraction of time. Instead of simulating several tens of engine cycles, the methodology is based on the numerical results obtained from just 5 cycles, which are then processed for developing suitable fitted correlations of the main parameters as a function of a normalized distance. The latter expresses the distance of the spheres of the initial flame within the computational cell at the spark-plug region with the local turbulent eddy, and provides a smooth transition from the laminar burning regime to the fully turbulent one. This sub-model is included in the ignition numerical approach and is applied here in a SI engine with 3 different hydrogen contents, 10%, 30% and 50%, and three equivalence ratios, 1, 0.8 and 0.7, showing that the COV of IMEP is well predicted compared to the available measured data. Other parameters of engine cycle variations are also examined, such as the distribution of the IMEP. The variability of NO (nitric oxide) emissions is also examined, showing that for the stoichiometric cases it follows a distribution similar to a normal (Gaussian) one, while for lower ratios it is positively skewed. Overall, the methodology seems to provide reliable results for the whole range of the operating conditions examined, while the next steps of this activity will focus on similar cases for engine with variable speed and load, with the final goal to include additional mechanisms that contribute to the engine cycle variations. • SI engine fueled with CH 4 –H 2 blends with variable H 2 content and equivalence ratio. • RANS-based CFD code for the engine performance and emissions under cyclic variability. • Fast methodology for low computational time and good accuracy of the COV of IMEP. • Variability of NO increases for high H 2 contents and low equivalence ratio. [ABSTRACT FROM AUTHOR]

The chemical, electrical, and mechanical power flow of a Chevrolet Spark plug‐in electric vehicle covering the cycles of the United States Environmental Protection Agency (US EPA), Vehicle Testing Regulations, namely the UDDS, Hwy and US06 cycles, is here analyzed. Experimental time series of instantaneous battery voltage and current are coupled to a simple model for energy conversion mechanical‐to‐electrical, and electrical‐to‐mechanical, and vice‐versa, and aerodynamic and rolling losses from Newton's equation model. A detailed CAE model is used to confirm the chassis dynamometer results complemented by the use of Newton's model. Computational time series of chemical, electric and mechanical power and energy are provided. Small advances are undergoing in motor/generator technology, where electric‐to‐mechanical efficiencies may approach 95%, while efficiencies mechanical‐to‐electric may exceed 90%. UDDS, Hwy and US06 efficiencies electric‐to‐wheels and wheels‐to‐electric are ηe−m = 0.794, 0.963, and 0.977, or ηm−e = 0.761, 0.893, and 0.902, respectively. Chemical‐to‐electric or electric‐to‐chemical efficiency ηc−e/e−c is about 0.984. These efficiencies are shared by the different products available on the market, with the weight of the vehicle and aerodynamic and rolling drags ultimately determining the energy efficiency of a specific vehicle. [ABSTRACT FROM AUTHOR]

The growing need for environmental sustainability motivates the search for efficient petroleum fuel replacements and additives, for which broad and reliable property knowledge is desired. In this work, a database of 615 fuel molecules is compiled with emphasis on spark-ignition engine applications. The considered fuel groups cover alkanes, alkenes, dienes, trienes, aromatics, alcohols, ketones, esters, ethers, furanics, oxygenated benzenoids, and nitrogenated components. For each component, the physical and chemical properties including research and motor octane numbers, octane sensitivity, cetane number, heat of vaporization, liquid density, surface tension, viscosity, boiling point, melting point, vapor pressure, lower heating value, H/C ratio, oxygen content, molecular weight, and water solubility are incorporated in the database. Their values are mostly experimentally determined and taken from the literature based on careful review and evaluation. For the case of missing experimental evidence, values are estimated by using a recently developed artificial neutral network-based octane number model or other established quantitative structure-property relationship models. This comprehensive database facilitates the straightforward selection of promising fuel candidates for specific application based on defined constraints, which is demonstrated in this study by ranking potential blending agents with gasoline for high efficiencies of future engines. In addition, this paper provides an overview of considered fuel properties in terms of their desirable ranges for modern spark-ignition engines, typical measurement procedures, and impacts on engine efficiency and emissions.

The indicated mean effective pressure (IMEP) is a key parameter for measuring the power output of an internal combustion engine (ICE). This indicator can be used to locate the high efficiency regions of engines. Therefore, it makes sense to predict the IMEP based on the machine learning (ML) approaches. However, different ML models are applicable to different scenarios, so it is important to choose the right model for prediction. The objective of this paper was to compare three ML models’ (ANN, SVR, RF) predictive performance in forecasting IMEP indicator with the input parameters spark timing (ST), speed and load. A validated one-dimensional (1D) computational fluid dynamics (CFD) model was employed to provide 756 sets of data for the training, validation, and testing of the model. The results indicated that the random forest (RF) model had the worst prediction performance, and support vector regression (SVR) had a slightly better prediction performance than the artificial neural network (ANN), at least for the investigations in this study. Overall, the ANN and SVR models showed good predictive performance for IMEP, as the coefficient of determination (R2) was close to unity, and the root mean squared error (RMSE) was close to zero. Whereas the overall prediction results of the RF model are acceptable, the RF model does not learn well for some internal engine laws.

The current research experimentally studied flame speed and stretch under engine in-cylinder conditions. A direct-injection, spark-ignition, and optically accessible engine was utilized to image the flame propagation, and E10 was selected as the fuel. Also, three fuel–air mixtures (stoichiometric, lean, and rich) were examined. The flame front was located by processing high-speed images. This study introduces a novel approach for calculation of equivalent spherical flame radius for analysis of flame speed and stretch. Flame front propagation analysis showed that during the flame propagation period, the stretch decreased until the flame front touched the piston surface. This was a common trend for stoichiometric, lean, and rich mixtures, which occurred because the flame radius was the dominant factor in the stretch calculation. In addition, the rich fuel–air mixture showed a lower flame stretch compared to stoichiometric or lean mixture. This was the result of a lower Markstein number for the rich fuel–air mixture. To study the sensitivity of different fuel–air mixtures to the flame stretch, the trajectory of the flame centroid was tracked until the flame front touched the piston surface. The results showed that the end centroid for the lean mixture deviated from the start point more than those of the rich and stoichiometric mixtures because the lean mixture had a higher flame stretch and lower flame speed. Furthermore, comparing the flame stretch at three different engine speeds revealed that increasing the engine speed increased the flame stretch, especially during the early flame development period. According to previous studies which discussed flame stretch as a flame extinguishment mechanism, the probability of flame extinction is higher when the engine speed is higher. Also, uncertainty analysis was conducted to determine the effect of camera setting on the flame stretch. Results showed that a maximum relative uncertainty of 4.5% occurred during the early flame development. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effect of the port injection of ammonia on performance, knock and NOx emission across a range of engine speeds in a gasoline/ethanol dual-fuel engine. An experimentally validated numerical model of a naturally aspirated spark-ignition (SI) engine was developed in AVL BOOST for the purpose of this investigation. The vibe two zone combustion model, which is widely used for the mathematical modeling of spark-ignition engines is employed for the numerical analysis of the combustion process. A significant reduction of ~50% in NOx emissions was observed across the engine speed range. However, the port injection of ammonia imposed some negative impacts on engine equivalent BSFC, CO and HC emissions, increasing these parameters by 3%, 30% and 21%, respectively, at the 10% ammonia injection ratio. Additionally, the minimum octane number of primary fuel required to prevent knock was reduced by up to 3.6% by adding ammonia between 5 and 10%. All in all, the injection of ammonia inside a bio-fueled engine could make it robust and produce less NOx, while having some undesirable effects on BSFC, CO and HC emissions. [ABSTRACT FROM AUTHOR]

Faced with the problem of reducing greenhouse gas emissions and transitioning toward a greater use of renewable energies, ammonia, as an energy carrier, is increasingly seen as a potential “green” fuel for transportation, in particular marine applications. However, its combustion characteristics (high minimum ignition energy and auto-ignition temperature, low combustion speed in comparison to usual hydrocarbon fuels) are drawbacks that have so far limited its use. Due to the evolution of different pollutant standards for road transportation, spark-ignition engines and thus the combustion process itself have been subjected to many changes over the last 20 years (e.g., gasoline direct injection, downsizing). The objective of this article is to discuss the potential of ammonia as a fuel for spark-ignition engines, thanks to the studies carried out so far and to point out directions for future work.

To reduce the greenhouse effect, it is important to reduce not only carbon dioxide but also methane emissions. Methane gas can be not only a fossil fuel (natural gas) but also a renewable energy source when it is extracted from biomass. After biogas has been purified, its properties become closer to those of natural gas or methane. Natural gas is an alternative energy source that can be used for spark-ignition engines, but its physicochemical properties are different from those of gasoline, and the spark-ignition engine control parameters need to be adjusted. This article presents the results of a study that considers a spark-ignition engine operating at different speeds (2000 rpm, 2500 rpm, and 3000 rpm) and the regulation of the timing of intake valve closure when the throttle is partially open (15%), allowing the engine to maintain the stoichiometric air–fuel mixture and constant spark timing. Studies have shown a reduction in engine break torque when petrol was replaced by natural gas, but break thermal efficiency has increased and specific emissions of pollutants (NOx, HC, CO2 (g/kWh)) have decreased. The analysis of the combustion process by the AVL BOOST program revealed different results when the engine ran on gasoline as opposed to when it ran on natural gas when the timing of intake valve closure changed. The volumetric efficiency of the engine and the speed of the combustion process, which are significant for engine performance due to the different properties of gasoline and natural gas fuels, can be partially offset by adjusting the spark timing and timing of intake valve closure. The effect of intake valve timing on engine fueled by natural gas more noticeable at lower engine speeds when the engine load is low.

Biogas, which is a renewable alternative fuel, has high antiknocking properties with the potential to substitute fossil fuels in internal combustion engines. In this study, performance characteristics of a spark-ignition (SI) engine operated under methane (baseline case) and biogas are compared at the compression ratio (CR) of 8.5:1. Subsequently, the effect of CR on operational limits, performance, combustion, and emission characteristics of the engine fueled with biogas is evaluated. A variable compression ratio, spark-ignition engine was operated at various CRs of 8.5:1, 10:1, 11:1, 13:1, and 15:1 over a wide range of operating loads at 1500rpm. Results showed that the operating range of the engine at 8.5:1 CR reduced when biogas was utilized in the engine instead of methane. However, the operating range of the engine for biogas extended with an increase in CR--an increase from 9.6N-m-16.5 N-m to 2.8N-m-15.1 N-m was observed when CR was increased from 8.5:1 to 15:1. The brake thermal efficiency improved from 13.7% to 16.3%, and the coefficient of variation (COV) of indicated mean effective pressure (IMEP) reduced from 12.7% to 1.52% when CR was increased from 8.5:1 to 15:1 at 8N-m load. The emission level of carbon dioxide was decreased with an increase in CR due to an improvement in the thermal efficiency and the combustion process. [ABSTRACT FROM AUTHOR]

According to the US Energy Information Administration, fossil fuels will remain the main source of energy for transportation over the next decades and thus the combustion of these fuels remains an important concern. This research studied the flame propagation under engine in-cylinder conditions and developed a correlation for turbulent burning velocity based on the global flame stretch concept. To study the impact of engine operation on flame stretch, two speeds, two loads, and three fuel-air mixtures were investigated. The flame front was determined by processing images of the flame natural luminosity. A turbulent burning velocity model was developed using dimensional analysis. The model showed that the turbulent burning velocity decreased due to flame stretching. Higher engine speeds increased the turbulent burning velocity by increasing the turbulent intensity, yet a tradeoff between the flame stretch and the turbulent burning velocity due to higher engine speed was observed. In cases where the flame distortion was very high, the flame stretch may cancel out any benefits of a large enflamed area. Incorporating the flame stretch into the burning velocity model and coupling the developed model with GT-Power simulation software revealed that the stretch may result in a 35% reduction in turbulent burning velocity. • The developed model showed that the turbulent burning velocity decreased due to flame stretching. • Higher engine speeds increased the turbulent burning velocity by increasing the turbulent intensity. • A tradeoff between the flame stretch and the turbulent burning velocity due to higher engine speed was observed. • In cases where the flame distortion was very high, the flame stretch may cancel out any benefits of a large enflamed area. [ABSTRACT FROM AUTHOR]

This work presents the assessment of direct water injection in spark-ignition engines using single cylinder experiments and tabulated chemistry-based simulations. In addition, direct water injection is compared with cooled low-pressure exhaust gas recirculation at full load operation. The analysis of the two knock suppressing and exhaust gas cooling methods is performed using the quasi-dimensional stochastic reactor model with a novel dual fuel tabulated chemistry model. To evaluate the characteristics of the autoignition in the end gas, the detonation diagram developed by Bradley and co-workers is applied. The single cylinder experiments with direct water injection outline the decreasing carbon monoxide emissions with increasing water content, while the nitrogen oxide emissions indicate only a minor decrease. The simulation results show that the engine can be operated at λ = 1 at full load using water--fuel ratios of up to 60% or cooled low-pressure exhaust gas recirculation rates of up to 30%. Both technologies enable the reduction of the knock probability and the decrease in the catalyst inlet temperature to protect the aftertreatment system components. The strongest exhaust temperature reduction is found with cooled low-pressure exhaust gas recirculation. With stoichiometric air-fuel ratio and water injection, the indicated efficiency is improved to 40% and the carbon monoxide emissions are reduced. The nitrogen oxide concentrations are increased compared to the fuel-rich base operating conditions and the nitrogen oxide emissions decrease with higher water content. With stoichiometric air--fuel ratio and exhaust gas recirculation, the indicated efficiency is improved to 43% and the carbon monoxide emissions are decreased. Increasing the exhaust gas recirculation rate to 30% drops the nitrogen oxide emissions below the concentrations of the fuel-rich base operating conditions. [ABSTRACT FROM AUTHOR]

From experimental spark ignition (SI) engine studies, it is known that the slow-down of early flame kernel development caused by the (Le > 1)-property of common transportation-fuel/air mixtures tends to increase cycle-to-cycle variations (CCV). To improve the fundamental understanding of the complex phenomena inside the flame structure of developing flame kernels, an engine-relevant DNS database is investigated in this work. Conclusive analyses are enabled by considering equivalent flame kernels and turbulent planar flames computed with Le > 1 and Le = 1. In Part I of the present study (Falkenstein et al., Combust. Flame, 2020), a reduced representation of the local mixture state was proposed for the purpose of this analysis. Fluctuations in heat release rate attributed to differential diffusion were found to be governed by the parameters local enthalpy, local equivalence ratio, and H-radical mass fraction. Here, a coupling relation for the diffusion-controlled mixture parameter local enthalpy with local flame geometry and structure is derived, characterized by the key parameters κ and |∇ c |/|∇ c | lam. The analysis shows that the large positive global mean curvature intrinsic to the flame kernel configuration may detrimentally affect the local mixture state inside the reaction zone, particularly during the initial flame kernel development phase. External energy supply by spark ignition may effectively bridge over this critical stage, which causes the impact of global mean flame kernel curvature to be small under the present conditions compared to the overall effect of Le ≠ 1 observed in a statistically planar flame. Once ignition effects have decayed, the mixture state inside the reaction zone locally exhibits an identical dependence on |∇ c | as in a strained laminar flame. This implies that differential diffusion effects at Karlovitz numbers representative for part-load conditions are not weakened by small-scale turbulent mixing, which is undesirable for the engine application, but can be favorable in terms of modeling. [ABSTRACT FROM AUTHOR]

Although experimental evidence for the correlation between early flame kernel development and cycle-to-cycle variations (CCV) in spark ignition (SI) engines was provided long ago, there is still a lack of fundamental understanding of early flame/turbulence interactions, and accurate models for full engine simulations do not exist. Since the flame kernel is initiated with small size, i.e. with large positive curvature, differential diffusion is expected to severely alter early flame growth in non-unity-Lewis-number (Le ≠ 1) mixtures as typically used in engines. In this work, a DNS database of developing iso-octane/air flame kernels and planar flames has been established with flame conditions representative for stoichiometric engine part-load operation. Differential diffusion effects on the global heat release rate are analyzed by relating the present findings to equivalent flames computed in the Le = 1 limit. It is shown that in the early kernel development phase, the normal propagation velocity is significantly reduced with detrimental consequences on the global burning rate of the flame kernel. Besides this impact on the overall mass burning rate, the initial production of flame surface area by the normal propagation term in the flame area balance equation is noticeably reduced. By using the optimal estimator concept, it is shown that strong fluctuations in local heat release rate inherent to Le ≠ 1 flames in the thin reaction zones regime are mainly contained in the parameters local equivalence ratio, enthalpy, and H-radical mass fraction. Differential diffusion couples the evolution of these parameters to the unsteady flame geometry and structure, which is analyzed in Part II of the present study (Falkenstein et al., Combust. Flame, 2020). [ABSTRACT FROM AUTHOR]

High-speed Mie scatter imaging and in-cylinder pressure measurements are performed in an optically accessible four-stroke spark-ignition engine to investigate cycle-to-cycle variations (CCVs). Droplet Mie scattering is used to measure the cross-sectional flame contour. Machine learning (ML) methods are applied to predict combustion cycles of high maximum in-cylinder pressure based on flame cross-sections at -15 °CA (crank angle degrees before top dead center). All tested ML methods (decision tree-based, multi-layer perceptron, and logistic regression) are able to predict high energy engine cycles given only partial flame topology information at a temporal snapshot of the flame propagation. Feature importance analyses, employed using decision tree methods, reveal that a combination of flame position and shape features of the flames' cross-section is necessary in achieving a high prediction accuracy. These sensitivity analyses can be used to gain insight into the combustion processes and to strategically reduce the number of features. This enables the addition of new physical quantities in future investigations. [ABSTRACT FROM AUTHOR]

In internal combustion engines, the use of gas fuels is becoming widespread due to its advantages such as low cost and being more environmentally friendly. Acetylene is one of the gas fuels seen as an alternative to petroleum-based fuels in internal combustion engines. In this experimental study, the availability of acetylene gas, a gas fuel, at 1600 rpm, 2400 rpm and 3200 rpm engine speeds in a spark plug-fired engine was investigated. Acetylene gas was added to gasoline by 5% and 10% of the mass and its effect on exhaust emissions was studied. The results showed that adding acetylene gas to gasoline by mass increased CO, CO2 and NOx emissions and exhaust gas temperature. HC, oxygen emissions and air supply coefficient decreased. [ABSTRACT FROM AUTHOR]

The paper presents the results of thermogravimetric tests of engine oil used in a small turbocharged spark-ignition engine. The main observation from the research was a significant soot contamination of engine oil, that appears even at its low mileage. This indicates that also in the case of port fuel injection spark-ignition engine, high particulate matter emissions may occur. A rapid soot contamination of the oil in this engine indicates that the oil change interval should be shortened. [ABSTRACT FROM AUTHOR]

Spark timing, one of the essential parameters to control combustion in spark-ignition gasoline engines, is often advanced to optimize the power output and fuel economy. An overly advanced spark timing, or equivalently a large spark advance, however, can lead to severe knocking under heavy load engine operating conditions. In a trade-off between engine damage avoidance and power enhancement, the knock probability has to be regulated at a low percentage. Based on the observation that the logarithm of the knock intensity under steady operating conditions follows a normal distribution, in this research, a Bayesian knock probability estimation method is proposed using the normal-gamma distribution and the observed knock intensity. Based on the estimation, a spark advance control algorithm is also developed. The proposed knock probability control algorithm is validated on a full-scale test bench with a production spark-ignition engine. The results show that the proposed method is capable of regulating the knock probability to be close to the target percentage. With different parameter settings, the controller can further be configured to behave more aggressively or conservatively in knock probability estimation and regulation. In comparison with the conventional controller and the maximum likelihood–based controller, and in the tip-in/tip-out test, the proposed method also presents a quick response to transient engine operating conditions and a low spark advance dispersion after the spark advance converges close to the borderline. [ABSTRACT FROM AUTHOR]

Two different high-speed cameras, a Photron SA-Z and a Vision Research Phantom v7.3, were used together with a large-aperture endoscopic system to visualize the early flame in a nearly unmodified production IC engine. At very low light levels, the patterned read-out noise on the Phantom v7.3 becomes significant. Filtering in the Fourier domain was effective in suppressing this noise component to acceptable levels. A previously-developed algorithm with automatic dynamic thresholding was expanded to separately detect spark ignition and flame kernel in the image sequences. The robustness of the algorithm was examined by processing data sets from different engine operating conditions as well as at different levels of lens collection efficiency (f-number) for the same engine operating point. [ABSTRACT FROM AUTHOR]

The anxieties regarding global warming upon increasing greenhouse gas emission grades worldwide and the presence of petroleumbased fuels have directed the researchers to focus on the development of biofuels as well as the utilization of reformulated gasoline fuels by adding oxygenated additives resulting in an extensive application to improve fuel properties. In this study, engine performance and exhaust emission tests were performed using pure gasoline and volumetrically 10% ethanol-C2 or methanol- C1/gasoline blends (G100, E10, and M10). The engine experiments for all test fuels were carried out in a single-cylinder, fourstroke, water-cooled, spark-ignition (SI) engine under fixed engine speed (1500 rpm) and various loading conditions (25%, 50%, 75%, and 100%). In the tested engine, the brake specific fuel consumption (BSFC) values of G100, M10, and E10 fuels under full load condition were found to be as 0.279 kg/kWh, 0.296 kg/kWh and 0.307 kg/kWh, respectively. When the exhaust emissions were examined, E10 and M10 fuels were observed to have lesser CO, CO2, NOX, and HC emissions in comparison with pure gasoline. The lowest CO emission was determined as 3.15% for E10 fuel at a 75% load. NOX emissions descended with the increase of engine load in all fuel blends meanwhile the best performance is measured as 908.86 ppm in E10 fuel at 100% load. The minimum HC emission for E10 fuel was measured as 116.36 ppm at a 75% load. Compared with G100 fuel, E10 and M10 blends emitted 39% and 35% fewer HC emissions, respectively at 75% load. Besides, E10 and M10 fuels generated 8% and 5% less CO2 emissions at all engine loads, respectively, when compared to G100 fuel. As a result of thermodynamic analyses; The highest exergy efficiency values were found to be at 21.0% for G100, 17.92% for E10, and 16.85% for M10, respectively. Besides, the energy efficiencies were obtained to be as 30.01% for G100, 28.33% for E10, and 29.90% for M10, respectively. According to the sustainability analysis, E10 fuel performed better results than M10 fuel in order to be an alternative to G100 fuel. [ABSTRACT FROM AUTHOR]

Despite the high technical relevance of early flame kernel development for the reduction of cycle-to-cycle variations in spark ignition engines, there is still a need for a better fundamental understanding of the governing in-cylinder phenomena in order to enable resilient early flame growth. To isolate the effects of small- and large-scale turbulent flow motion on the young flame kernel, a three-dimensional DNS database has been designed to be representative for engine part load conditions. The analysis is focussed on flame displacement speed and flame area in order to investigate effects of flame structure and flame geometry on the global burning rate evolution. It is shown that despite a Karlovitz number of up to 13, which is at the upper range of conventional engine operation, thickening of the averaged flame structure by small-scale turbulent mixing is not observed. After ignition effects have decayed, the flame normal displacement speed recovers the behavior of a laminar unstretched premixed flame under the considered unity-Lewis-number conditions. Run-to-run variations in the global heat release rate are shown to be primarily caused by flame kernel area dynamics. The analysis of the flame area balance equation shows that turbulence causes stochastic flame kernel area growth by affecting the curvature evolution, rather than by inducing variations in total flame area production by strain. Further, it is shown that in local segments of a fully-developed planar flame with similar surface area as the investigated flame kernels, temporal variations in flame area rate-of-change occur. Contrasting to early flame kernels, these effects can be exclusively attributed to curvature variations in negatively curved flame regions. [ABSTRACT FROM AUTHOR]

Developing more energy-efficient and environmentally friendly transportation technologies, that can enable to use significantly less petroleum and to reduce regulated emissions while meeting or exceeding drivers' performance expectations, has always been one of the main challenges in automotive technology. Therefore, based on an experimental dataset, metamodels were generated using design of computer experiments and central composite design technique in order to accurately predict carbon monoxide (CO), oxides of nitrogen ( NO x ), hydrocarbon (HC) and carbon dioxide ( CO 2 ) emissions, mean effective pressure and exergy destruction due to heat transfer and combustion process. Combustion metamodels was evaluated varying air–fuel ratio, ignition timing [( ∘ CAD) Crank Angle Degrees], compression ratio, and combustion duration ( ∘ ) on the performance of a Spark Ignition (SI) engine at constant speed of 750 rpm. Because SI gasoline engines always encounter the decreased thermal efficiency and increased toxic emissions at idle (Jurgen in Automotive electronics handbook, McGraw-Hill, New York, 1995). The Akaike information criterion was applied to automatically select the best metamodel for each case. [ABSTRACT FROM AUTHOR]

Spark discharge under flow conditions in different gas media is compared. The gases include nitrogen, pure methane, and methane–air mixtures with different volume ratios. The self-illuminated spark plasma photos, and the discharge current and voltage waveforms are recorded. [ABSTRACT FROM AUTHOR]

This research project shows the effect of altitude on the emissions of polluting gases from a spark ignition engine (SI engine), considering that in Ecuador and in Latin America, there are topographic variations that affect the conditions of vehicle operation. This work analyzes the emissions of polluting gases generated by a SI engine operating at different heights above sea level. Altitude is a very important factor in the performance of SI engine and in the emissions that it produces. Measurements were developed in three cities with different height above sea level (0, 2.200 and 3.000 masl), at four engine revolutions (idle, 2.000, 3.500 and 4.500 rpm) and at the same hour of the day. The emissions of carbon monoxide (CO), carbon dioxide (CO2) and unburned hydrocarbons (UHC) were measured. The results showed that the engine revolutions are the most important factor in the emission of CO and UHC; as the rpm increase, the percentage of CO is higher and the amount of UHC is reduced; however, in CO2 emissions, altitude has a more significant effect, decreasing as atmospheric pressure drops. Consequently, it is expected that the results achieved will promote future works to reduce harmful emissions to human health. [ABSTRACT FROM AUTHOR]

In the automotive sector, hydrogen is being increasingly explored as an alternative fuel to replace conventional carbon-based fuels. Its combustion characteristics make it well-suited for adaptation to internal combustion engines. The wide flammability range of hydrogen allows for higher dilution conditions, resulting in enhanced combustion efficiency. When combined with lean combustion strategies, hydrogen significantly reduces environmental impact, virtually eliminating carbon dioxide and nitrogen oxide emissions while maintaining high thermal efficiency. This paper aims to assess the potential of using an outwardly opening poppet valve hydrogen direct injection (DI) system in a small engine for light-duty applications. To achieve this, a comparison of performance, emission levels, and combustion parameters is conducted on a single-cylinder spark-ignition (SI) research engine fueled by hydrogen, using both port fuel injection (PFI) and this new direct injection system. Two different engine loads are measured at multiple air dilution and injection timing conditions. The results demonstrate notable efficiency improvements, ranging from 0.6% to 1.1% when transitioning from PFI to DI. Accurate control of injection timing is essential for achieving optimal performance and low emissions. Delaying the start of injection results in a 7.6% reduction in compression work at low load and a 3.9% reduction at high load. This results in a 3.1-3.2% improvement in ISFC in both load conditions considered. • A novel hydrogen medium-pressure direct injection system has been evaluated. • Direct injection improves gross indicated efficiency levels between 0.6%–1.1%. • ISFC gains around 3% are achieved with delayed SoI using a direct injection system. • Nitrogen oxide levels are minimized by combining dilution and injection strategies. • Results hint that controlling stratification may enhance efficiency and pollutants. [ABSTRACT FROM AUTHOR]

The impacts of excess air ratio (λ) on combustion, CO and NO regulated emissions, and formaldehyde (HCHO) and unburned methanol (CH 3 OH) unregulated emissions behaviors in a spark-ignition H 2 /methanol dual injection engine were studied numerically. The results show that the peak in-cylinder pressure (PIP), peak heat release rate (PHRR) and peak in-cylinder temperature (PIT) all decrease with the increase of λ , and their corresponding crank angles are also late; the ignition delay (ID) and combustion duration (CD) decrease with the increase of λ ; the CO, HCHO and CH 3 OH emissions increase with the increase of λ , while the NO emission decreases with the increase of λ. At a constant λ , the PIP, PHRR and PIT for with 5 % H 2 (R H2 = 5 %) are higher than those for without H 2 (R H2 = 0 %), and their corresponding crank angles for R H2 = 5 % are earlier than those for R H2 = 0 %; the ID and CD for R H2 = 5 % are lower than those for R H2 = 0 %. The CO, HCHO and CH 3 OH emissions for R H2 = 5 % are also much lower than those for R H2 = 0 %, while the NO emission for R H2 = 5 % is also higher than that for R H2 = 0 %. The impact order of adding H 2 to reduce emissions of H 2 /methanol dual-injection engine is: CO ≥ HCHO > unburned CH 3 OH. • H 2 -assisted combustion was proposed to improve the combustion and emissions of H 2 /methanol engine.. • The role of H 2 -assisted combustion was revealed.. • Adding H 2 is more beneficial to improve the firing characteristics under lean burn. • The impact order of adding H 2 to reduce emissions is: CO ≥ HCHO > unburned CH 3 OH. [ABSTRACT FROM AUTHOR]

This paper assesses the cyclic variability (cycle-by-cycle variations (CCV)) of combustion, performance and nitric oxide (NO) emissions in high-speed (HS), spark-ignition (SI) engine fueled with hydrogen-enriched methane (CH 4), for which experimental data are available. Thus, in-house, two-zone, quasi-dimensional turbulent combustion model is used that closely trails the flame-front movement, which was validated before regarding performance, emissions, exergy, and CCV for gasoline- or methane-run HSSI engines. It is enhanced herein to study CCV of performance, combustion, and NO emissions, with engine fueled by various hydrogen-methane blends (up to 50 % by vol. hydrogen) and equivalence ratios (EQR). Hence, the influence of flame-kernel turbulence and EQR variation mechanisms on CCV attributes is considered and assessed. The numerical results are compared with measured data of cylinder pressure, indicated mean effective pressure (IMEP), and NO emissions at 'steady' conditions, and further for validation against available experimental CCV results for IMEP at all operating conditions. That CCV analysis is extended to peak pressure, IMEP, and NO emissions using coefficients of variation (COV), frequency distributions, and pertinent diagrams illuminating their cycle-by-cycle variations. The CCV variations decrease with hydrogen content in the blend whereas they increase with the mixture leanness delineating the relative merits of the two mechanisms. • CCV study in SI engine run on H 2 /CH 4 blends with in-house, quasi-dimensional model. • Influence on CCV of flame-kernel turbulence and fuel-air ratio variation mechanisms. • The two mechanisms impact differently on various performance and emission parameters. • CCV evaluation of peak pressure, IMEP, combustion attributes, and NO emission. • CCV variations decrease with hydrogen content in the blend and mixture richness. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study investigating the effects of water-in-gasoline emulsion (WiGE) on the performance and emissions of a turbocharged PFI spark-ignition engine. The emulsions were produced through a micro-channels emulsifier, potentially capable to work inline, without addition of surfactants. Measurements were performed at a 3000 rpm speed and net Indicated Mean Effective Pressure (IMEP) of 16 bar: the engine point representative of commercial ECU map was chosen as reference. In this condition, the engine, fueled with gasoline, runs overfueled (λ = 0.9) to preserve the integrity of the turbocharger from excessive temperature, and the spark timing corresponds to the knock limit. Starting from the reference point, two different water contents in emulsion were tested, 10% and 20% by volume, respectively. For each selected emulsion, at λ = 0.9, the spark timing was advanced from the reference point value to the new knock limit, controlling the IMEP at a constant level. Further, the cooling effect of water evaporation in WiGE allowed it to work at stoichiometric condition, with evident benefits on the fuel economy. Main outcomes highlight fuel consumption improvements of about 7% under stoichiometric mixture and optimized spark timing, while avoiding an excessive increase in turbine thermal stress. Emulsions induce a slight worsening in the HC emissions, arising from the relative impact on combustion development. On the other hand, at stoichiometric condition, HC and CO emissions drop with a corresponding increase in NO.

We describe the external and internal hydrogen interaction on contacting surfaces in the “cylinder–piston rings” friction coupling. Under the influence of high temperatures and pressure, the oil in the combustion chamber at a temperature up to 1473 K decomposes and forms small amounts of water. External hydrogen (H2) is subsequently formed. Hydrogen removal from the piston rings reduces the heterogeneity of the structure, residual stresses, and uneven physical and chemical properties of the near-surface layers, which reduces the stress concentration and, as a consequence, results in an improvement in the performance characteristics of the surface layers of the friction couple “cylinder-piston rings” of the spark ignition engine.

Engine knock determination has been conducted in various ways for spark timing calibration. In the present study, a knock classification model was developed using a machine learning algorithm. Wavelet packet decomposition (WPD) and ensemble empirical mode decomposition (EEMD) were employed for the characterization of the in-cylinder pressure signals from the experimental engine. The WPD was used to calculate 255 features from seven decomposition levels. EEMD provided total 70 features from their intrinsic mode functions (IMF). The experimental engine was operated at advanced spark timings to induce knocking under various engine speeds and load conditions. Three knock intensity metrics were employed to determine that the dataset included 4158 knock cycles out of a total of 66,000 cycles. The classification model trained with 66,000 cycles achieved an accuracy of 99.26% accuracy in the knock cycle detection. The neighborhood component analysis revealed that seven features contributed significantly to the classification. The classification model retrained with the seven significant features achieved an accuracy of 99.02%. Although the misclassification rate increased in the normal cycle detection, the feature selection decreased the model size from 253 to 8.25 MB. Finally, the compact classification model achieved an accuracy of 99.95% with the second dataset obtained at the knock borderline (KBL) timings, which validates that the model is sufficient for the KBL timing determination.

The protection of the environment and pollution control are issues of paramount importance. Researchers today are engrossed in mitigating the harmful impacts of petroleum waste on the environment. Lubricating oils, which are essential for the smooth operation of engines, are often disposed of improperly after completing their life. In the experimental work presented in this paper, deteriorated engine oil was regenerated using the acid treatment method and was reused in the engine. The comparison of the properties of reused oil, the engine’s performance, and the emissions from the engine are presented. The reuse of regenerated oil, the evaluation of performance, and emissions establish the usefulness of the regeneration of waste lubricating oil. For the used oil, total acid number (TAN), specific gravity, flash point, ash content, and kinematic viscosity changed by 60.7%, 6.7%, 4.4%, 96%, and 15.5%, respectively, compared with fresh oil. The regeneration partially restored all the lost lubricating oil properties. The performance parameters, brake power (BP), brake specific fuel consumption (BSFC), and exhaust gas temperature (EGT) improved with regenerated oil in use compared with used oil. The emissions CO and NOX contents for acid-treated oil were 9.7% and 17.3% less in comparison with used oil, respectively. Thus, regenerated oil showed improved performance and oil properties along with significantly reduced emissions when employed in an SI engine.

Water injection is investigated for turbocharged spark-ignition engines to reduce knock probability and enable higher engine efficiency. The novel approach of this work is the development of a simulation-based optimization process combining the advantages of detailed chemistry, the stochastic reactor model and genetic optimization to assess water injection. The fast running quasi-dimensional stochastic reactor model with tabulated chemistry accounts for water effects on laminar flame speed and combustion chemistry. The stochastic reactor model is coupled with the Non-dominated Sorting Genetic Algorithm to find an optimum set of operating conditions for high engine efficiency. Subsequently, the feasibility of the simulation-based optimization process is tested for a three-dimensional computational fluid dynamic numerical test case. The newly proposed optimization method predicts a trade-off between fuel efficiency and low knock probability, which highlights the present target conflict for spark-ignition engine development. Overall, the optimization shows that water injection is beneficial to decrease fuel consumption and knock probability at the same time. The application of the fast running quasi-dimensional stochastic reactor model allows to run large optimization problems with low computational costs. The incorporation with the Non-dominated Sorting Genetic Algorithm shows a well-performing multi-objective optimization and an optimized set of engine operating parameters with water injection and high compression ratio is found. [ABSTRACT FROM AUTHOR]

Biogas is a promising alternative fuel to reduce the consumption of petroleum-based fuels in internal combustion (IC) engines. In this work, the effect of various biogas compositions on the performance, combustion, and emission characteristics of a spark-ignition (SI) engine is investigated. Additionally, the effect of Wobbe index (WI) of various fuel compositions was also evaluated on the operational limits of the engine. While considering a wide range of biogas compositions (including bio-methane), the percentage of carbon dioxide (CO2) (in a blend of methane and CO2) was increased from 0 to 50% (by volume). A single-cylinder, water-cooled, SI engine was operated at 1500 rpm over a wide range of operating loads with compression ratio of 8.5:1. With the increase in WI of the fuel, both low (limited by coefficient of variation (COV) of indicated mean effective pressure (IMEP)) and high (limited by pre-ignition) operating loads were decreased; however, it was found that the overall operating range was increased. Results also showed that for a given operating load, with the increase of CO2 percentage in the fuel, the brake thermal efficiency was decreased, and the flame initiation and combustion durations were increased. The brake thermal efficiency was decreased from 16.8% to 13.7%, when CO2 was increased from 0% to 40% in methane-CO2 mixture at 8 N·m load. Concerning to emissions, a considerable decrease was noted in nitric oxide, whereas hydrocarbon, carbon monoxide and carbon dioxide emissions were increased, with the increase in CO2 percentage. [ABSTRACT FROM AUTHOR]

In this study, the engine performance and emissions of gasoline were examined by applying a response surface methodology (RSM) optimisation approach. Fusel oil–gasoline blends were used to operate an engine at various speeds and loads. The optimal fusel oil–gasoline blend mix ratio was determined to minimise fuel consumption and nitrogen oxide and hydrocarbon emissions and to maximise the brake power (BP). The results demonstrate that the engine load and speed have a significant effect on performance and emissions. In addition, the blended fuels (F10 and F20) were shown to reduce NOx emissions. Furthermore, insignificant effects on engine performance were observed for fusel oil compared with pure gasoline. The design of experiments (DoE) method, which is a statistical technique, indicated that F20 was the optimum blend ratio among the three studied fuels, based on the RSM. The optimal parameters were a load corresponding to 60% of the wide open throttle engine load and an engine speed of 4500 rpm for the F20 blend, resulting in a high desirability value of 0.852 for the test engine, with values of 67.6 kW, 235.17 g/kW.h, 0.118%vol, and 1931.4 ppm for the BP, brake-specific fuel consumption, CO emission, and NOx emission, respectively. [ABSTRACT FROM AUTHOR]

This work develops a systematic methodology able to identify the desired work points, the metamodels were evaluated varying air–fuel ratio, ignition timing, compression ratio, and combustion duration using design of computer experiments and RSM. It provide the possibility to determine optimal control parameters, according to selected objectives and operating constraints. This methodology is able to automatically identify the optimal engine calibration with less computational effort. Only in this way, the reliability of an integrated metamodel/optimizer approach can be included in a general-purpose that is to identify the engine calibration that minimizes motor vehicle emissions according to European emission standards (European Union in Off J Eur Union 50, 2007). As long as it improves mean effective pressure and reduces exergy destruction due to heat transfer and combustion process. Since, in internal combustion engines, more than 30–40 % of fuel energy wastes through the exhaust and just 12–25 % of the fuel energy converts to useful work. So, researchers are motivated to recover the heat from the waste sources in engines using the ways which not only reduce the demand of fossil fuels, but also reduce the harmful greenhouse gases and help to energy saving (Hatami et al. in Neural Comput Appl 25(7–8):2079–2090, 2014). The advantages of this contribution include the ability to study a wide range of parametric space and to independently evaluate physical and chemical processes, and detailed in-cylinder information, which is normally not available or is inaccessible in experiments. The uncertainty of the information in this unexplored design region can be quantified. Finally, the problem of optimizing involves three optimization fronts, energetic, economic and ecological (Chica and Torres in Int J Interact Des Manuf 12(1):355–392, 2018). [ABSTRACT FROM AUTHOR]

• TJI concept was implemented in a high compression ratio turbocharged SI engine. • A numerical methodology was developed to design pre-chambers geometry. • Selected pre-chamber designs were experimentally evaluated and scored. • TJI concept is unable to extend dilution ratio to avoid the use of TWC system. • TJI concept is less tolerant to EGR dilution than the standard ignition concept. The pre-chamber ignition concept is an attractive strategy to enable the operation of spark-ignition engines in lean or diluted conditions keeping a suitable combustion process. According to the results the benefits in lean conditions include the combustion process shortening, the improvement of combustion stability and the increase of combustion efficiency by lowering carbon monoxide and hydrocarbons emissions. Thus, the pre-chamber ignition concept, especially in its passive version, arises as a promising alternative for future spark-ignition engines for passenger car applications. In this framework, an experimental investigation has been carried out to evaluate the potential of passive pre-chamber ignition concept in a high compression ratio, turbocharged, port fueled spark-ignition engine, using 95 Research Octane Number gasoline. As a first step, a 1D Wave Action Model was generated to design the pre-chamber geometry taking the fuel available at the start of pre-chamber combustion and the pressure difference between the main chamber and pre-chamber as key parameters. In a second step, these pre-chamber designs were experimentally validated at high load/speed conditions (4500 rpm, 12.5 bar Indicated Mean Effective Pressure) and compared with the conventional spark-ignition concept. Experimental results show how the passive pre-chamber concept increases efficiency with good combustion stability and high combustion efficiency in stoichiometric conditions. Nevertheless, maximum lambda attainable with the passive system is similar than that of the conventional spark and much lower compared to the maximum levels reported for the active system. [ABSTRACT FROM AUTHOR]

• Exhaust gases are the major source of exergy losses for full load condition. • Pumping losses are the major source of irreversibilities for partial loads. • Ethanol combustion has a lower degree of irreversibility compared to that of gasohol. • Higher mechanical losses are observed when the engine is operating with ethanol. • Exergy of exhaust gases is higher for lean mixtures conditions. Exergetic analysis consists in the evaluation of the exergetic balance on experimental data. When applied to an internal combustion engine, exergetic analysis can identify sources of inefficiency and potentialities for utilizing exergy that would be rejected. To perform this analysis, experimental data were acquired for different operating conditions of a spark-ignition engine by using gasohol and hydrous ethanol as fuels. With these data, an exergetic analysis was carried out by evaluating the effects of engine operating parameters on associated irreversibilities. Afterwards, a comparison between the exergetic analyses of hydrous ethanol and gasohol was presented. Finally, first and second law efficiencies were evaluated as functions of engine speed, engine load and air–fuel ratio. Exergy distributions of hydrous ethanol at different conditions and the accounts of exergy losses during engine operations were also evaluated. [ABSTRACT FROM AUTHOR]

The spark ignition (SI) methanol engine is particularly difficult for cold start at low ambient temperature. Adding liquefied petroleum gas (LPG) can ensure a successful cold start of SI methanol engine. Based on a single-cycle fuel injection strategy, the effects of the amount and injection timings of methanol and LPG per cycle were experimentally investigated on cold start firing and emissions of a LPG/methanol dual-fuel SI engine. The results show that the minimum amount of LPG injected per cycle is the key factor to determine the reliable firing of LPG/methanol engines at low ambient temperatures. In order to form an ideal mixture in the firing cycle, 300 °CA injection interval between methanol and LPG is feasible to be used. Fuel injection parameters have great influences on the HC emissions, which are 74.4% lower under critical firing than that of misfiring mode. By altering injection parameters, unburned methanol shows opposite tendencies with formaldehyde emissions and similar tendencies with HC emissions. • A single cycle fuel injection strategy is used to study cold start firing behavior. • Demarcation line between cold start firing and misfiring zone is determined. • Injection parameters significantly affect cold start firing behavior. • Formaldehyde and unburned methanol show an opposite trend with fuel injection parameters. • HC and unburned methanol show similar tendencies with injection parameters. [ABSTRACT FROM AUTHOR]

Automotive manufacturers nowadays are constantly working on improving their internal combustion engines' performance by reducing the fuel consumption and emissions, without compromising the power generated. Manufacturers are therefore relying on virtual engine models that can be run on simulation software in order to reduce the amount of time and costs needed, in comparison with experiments done on engine test benches. One important element of the intake system of an internal combustion engine is the throttle valve, which defines the amount of air reaching the plenum before being drawn into the cylinders. This article discusses a widely used model for the estimation of air flow rate through the throttle valve in an internal combustion engine simulation. Experiments have been conducted on an isolated throttle valve test bench in order to understand the influence of different factors on the model's discharge coefficient. These experiments showed that the discharge coefficient varies with the pressure ratio across the throttle valve and with its angle. Furthermore, for each angle, this variation can be approximated with a linear model composed of two parameters: the slope and the Y-Intercept. These parameters are calibrated for different throttle valve angles. This calibration can be done using automotive manufacturers' standard engine test fields that are often available. This model is then introduced into an engine simulation model, and the results are compared to the experimental data of a turbocharged engine test bench for validation. They are also compared with a standard discharge coefficient model that varies only with the throttle valve angle. The results show that the new model for the discharge coefficient reduces mass flow estimation errors and allows expanding the applications of the throttle valve isentropic nozzle model. [ABSTRACT FROM AUTHOR]