On the influence of different alcohol-type biofuels on performance and engine emissions of an SI engine

Greenhouse gas emissions (G.H.G.) from vehicles are the main source of pollution. In this transition period from fossil fuels to the use of synthetic fuels, the diversification of alternative fuels used to fuel internal combustion engines is seen as one of the best alternatives for reducing G.H.G. In Europe, conforming to the stringent emission reduction targets for 2030, as well as trying to fulfil the regulations of the new Euro VII standard will force engine manufacturers to adopt alternative fuel solutions with a low environmental impact. However, fossil fuels will continue to be used but alternative fuels will substantially decrease our dependence on petroleum-derived fuels. Modern simulation software tools make it easy to produce a fairly accurate analysis of how an internal combustion engine works without the need for prototyping. Packages such as Ricardo WAVE or AVL Boost, are relatively cheap and represent accessible tools for developing, designing, and testing modern internal combustion engines. AVL Boost is a widely used engine simulation tool a 1D (one-dimensional) simulation software that allows engineers and researchers to model, simulate, and optimize various internal combustion engines, including spark ignition (SI) engines, diesel engines, and hybrid powertrains. The software also offers a high degree of flexibility in terms of alternative fuel blends. This paper evaluates the influences of using alcohol-based biofuels on performance metrics and pollutant emissions, such as brake power, brake thermal efficiency, and emissions, such as CO, CO2, and NOx in a spark ignition engine. The effects of varying alcohol fractions in the gasoline-alcohol blends on engine performance and emissions are analysed and explained. In this study, several types of ethanol in gasoline blends were simulated (E25, E50, E85). The one-dimensional model of the tested engine was developed based on the design dimensions of the 1.2L TCe H5FT engine produced by Renault. In the context of maintaining constant engine power output, the findings from the simulation results indicate that the utilization of alcohol-based blends with a high volumetric percentage of alcohol (ranging from 70-90%) can result in a substantial increase in fuel consumption, particularly in the case of methanol blends. Consequently, this phenomenon is associated with an elevated emission of carbon dioxide (CO2). However, it should be noted that despite this drawback, there is evidence of an inclination towards reduced emissions of other pollutants due to the enhanced combustion processes facilitated by the higher ratio of oxygenated compounds and a lower peak temperature. Methanol, one of the two alcohols investigated in this study, is not recommended for usage in fuel blends for several reasons. Firstly, the consumption rate of methanol is higher compared to ethanol, which can result in increased fuel usage. Secondly, methanol poses health risks due to its toxicity at certain levels, posing potential hazards in handling and utilization. Moreover, high concentrations of methanol are not easily miscible with gasoline without the addition of co-solvents, further limiting its feasibility as a viable fuel component.


Introduction
During the transition from petroleum-based fuels to electrification or the use of synthetic fuels, the exploration of clean alternative fuels to power internal combustion engines emerges as a paramount approach.Fossil fuels currently fulfil the majority of global energy demands; however, using them as fuels in a combustion process contributes significantly to greenhouse gas emissions released into the atmosphere.To address this issue, biomass has gained recognition as a crucial resource for the production of alternative fuels.Given the stringent regulations on exhaust gas emissions produced by internal combustion engines worldwide, the transportation sector is compelled to seek alternatives to fossil fuels.Notably, ethanol has gained momentum in recent years as from an additive blended into gasoline to a viable substitute for gasoline.Blending ethanol with petrol can not only extend its availability but also improve its properties like knock characteristics, Reid vapor pressure and combustion characteristics while reducing "well-to-wheel" emissions generated by internal combustion engines.Moreover, if ethanol is derived from renewable sources, it boasts a neutral carbon footprint.Enzymes and microorganisms play a vital role in extracting bio alcohols through the process of alcoholic fermentation, which involves the conversion of cellulose, glucose, starch, carbohydrates, and other sugars into ethanol.These bio alcohols are categorized into distinct types, namely bioethanol, bio propanol, and biobutanol [1].
Currently, the production methods for bio alcohols hold significant importance.The European Union has committed to including a certain proportion of bio-components in all internal combustion engine fuels distributed within its market.Among the various fuels utilized in the European Union, gasoline stands as the second most commonly used, following diesel [2].Consequently, the consumption of these biocomponents within the fuel aligns with this ratio.The European standard EN 228 outlines the quality requirements and parameters for gasoline sold in the European market [3].Directive 2009/30/EC mandates that Member States necessitates suppliers to ensure that gasoline with a maximum oxygen content of 2.7%vol.is made available in the market, effectively translating to 7.3% volume of ethanol [4].
Approximately half of the emissions generated can be attributed to private car transport and public transportation.Recognizing the urgent necessity to tackle climate change, governments worldwide are exerting pressure on the transport sector to curtail greenhouse gas (GHG) emissions resulting from fuel combustion.To this end, the majority of major vehicle markets have established limits on the amount of CO2 they are allowed to produce [5].
The road transport sector accounts for approximately 15% of global carbon dioxide emissions.Europe has taken the lead in establishing the most rigorous targets for tailpipe CO2 emissions, aiming for a 37.5% reduction within the next decade, ultimately reaching below 59 g/km by 2030.Ongoing efforts are being made to further refine this target to align with the European green initiative [6].
In recent years, the utilization of alternative fuels in engines has gained significant importance due to growing concerns regarding climate change and the imperative to reduce greenhouse gas emissions.However, despite this growing awareness, numerous governments have set targets for the gradual phasing out of internal combustion engines within the timeframe 2025 to 2040.Consequently, current research endeavours are concentrated on developing alternative solutions that not only meet tank-towheel carbon dioxide (CO2) emission targets but also address urban air quality challenges.To accomplish these objectives, the adoption of electrification is paramount, beginning with the widespread implementation of hybrid electric vehicles (HEVs) and progressing towards the vision of zero tailpipe emission vehicles (ZEVs).ZEVs encompass diverse technologies such as battery electric vehicles (BEVs) and fuel cell electric vehicles (FCEVs) [7].
The introduction of a new emissions standard, Euro 7, is currently in progress and is scheduled to be implemented in 2025.Euro 7 will introduce more stringent regulations for internal combustion engines, with a particular focus on diesel vehicles.Notably, it will also establish the first-ever guidelines for brake and tire emissions, which will apply to electric cars as well.According to Euro 7 standards, both gasoline and diesel vehicles must limit their emissions to no more than 60 milligrams [8].
Internal combustion engines are known to emit several harmful exhaust gases, including unburned hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO), and particulate pollutants.These emissions have significant environmental implications and must be effectively addressed to mitigate their impact.
Alcohol-based fuels offer a promising solution for significantly reducing carbon emissions.This research study aims to present and analyze the outcomes of an engine simulation conducted using various blends of alcohol and petrol.The objective is to gain valuable insights into the performance of different fuel blends and their impact on engine efficiency and emissions.Furthermore, the study examines the potential advantages and disadvantages of employing alcohol as a fuel source, while also comparing it to conventional petrol.By delving into these aspects, a comprehensive understanding of the viability of alcohol-based fuels can be attained.
The polarity of methanol and ethanol plays a significant role as it enables both compounds to form hydrogen bonds and achieve complete miscibility with water.In contrast, gasoline primarily consists of hydrocarbon molecules, rendering it a non-polar substance with a low dipole moment.Consequently, gasoline does not mix with water and exhibits phase segregation when combined with alcohols.This phenomenon results in the formation of distinct layers of gasoline and alcohol-water mixtures [9].
Fortunately, spark ignition engines can tolerate a certain percentage of water-contaminated mixtures without adverse effects.This alleviates the necessity to obtain stable gasoline-ethanol-water blends using co-solvents and emulsifiers [10].

Methodology
The utilization of virtual modeling through mathematical models implemented in specialized software, such as AVL Boost, Ricardo WAVE, or GT-Power, has emerged as a prominent approach, surpassing traditional prototyping methods.This shift offers significant advantages in the development of internal combustion engines, including time efficiency, cost-effectiveness, and improved overall efficiency.Simulation models provide insights that are often challenging to obtain experimentally, enhancing the understanding of complex engine processes.
Moreover, simulations that incorporate fluid flow modeling have become important tools for designing engine intake and exhaust systems.While most engine processes occur in three dimensions (3D), simulations introduce additional complexity to the model and increase compilation time.As a result, simplified versions of the typically one-dimensional models are commonly employed, striking a balance between accuracy and computational efficiency.
Recently, there has been a rise in articles and publications centring on simulating the functionality of an internal combustion engine.This trend reflects the increasing interest in employing such software for research purposes.While many of these published works primarily involve comparing experimental findings to simulation outcomes, there exist certain publications that exclusively rely on calculations [10].This study endeavours to construct a one-dimensional (1D) model that simulates the response of a four-stroke spark ignition engine with direct in-cylinder fuel injection when the fuel type is changed from regular petrol to a mixture of various percentages of ethanol and gasoline (E25, E50, E85).
To achieve this objective, the simulation was fine-tuned by utilizing data acquired from the reference engine while operating on gasoline and establishing correlations for simulations conducted with alternative fuel types.The methodology revolves around constructing a one-dimensional model of a spark ignition engine, intending to illustrate the engine's behaviour when fuelled with various blends of alcohol and petrol.The model was created using a software solution provided by AVL namely Boost version 2019.1 and subsequently calibrated using data obtained from the selected reference model, specifically the 1.2L TCe H5FT (Gasoline Direct Injection) engine produced by Renault.Table 1 showcases some significant design attributes of the reference engine.

Simulation study
Figure 1 depicts the simulation program interface with the constructed virtual engine model.Each icon featured in the interface represents a mathematical model.The primary components encompassed in the model are as follows: cylinders, ducts, metering points, boundary conditions, transfer elements (such as throttle valve, injector, and restrictor), volume elements (such as plenum), assembled elements (including air cleaner, air filter, intercooler, catalytic converter, and particulate filter), and supercharger elements (such as a turbocharger or a mechanical compressor).Furthermore, the user has the flexibility to incorporate external elements (linked to AVL Cruise or Fire), control elements (such as the engine control unit, temperature, or pressure sensors) or acoustic elements (like a microphone).

Figure 1. Virtual engine model in AVL Boost program
To assess the real-world applicability of the virtual model, an evaluation of its real counterpart is necessary.The simulation model must incorporate the geometric characteristics specific to the actual engine.Subsequently, the model needs to be calibrated by comparing its performance to that of the real engine when fuelled solely with regular petrol.Following the calibration process, the performance and pollutant emissions of the engine will be examined under different fuel scenarios, including gasoline, and ethanol-gasoline blends.To streamline the model calibration procedure, a map for the simulated engine has been developed using statistical data and publicly available results provided by the manufacturer of the selected reference model.This map was tailored to accommodate the stoichiometric air-fuel ratio for each fuel utilized.Table 2 displays the stoichiometric ratios for gasoline and each blend employed in the study.The development of an air-fuel ratio map holds significant importance in the optimization of engine performance, ensuring that the engine receives the ideal mixture of air and fuel for various operating conditions.Numerous engine parameters, such as throttle position, engine speed, and load, influence the required air-fuel ratio.The process of "mapping" remains a crucial element in optimizing engine performance.By calibrating the air-fuel ratio according to the specific operating conditions, engineers can achieve the desired balance between power, efficiency, and emission control.With ongoing advancements in engine technologies, further enhancements in the techniques for developing lambda maps are anticipated, resulting in more efficient and environmentally friendly engines.Figure 2 illustrates the generated map for the simulated model.This map was maintained for all fuel mixtures utilized, adapting the ratio based on the stoichiometric air-fuel ratio specific to each mixture type.When employing fuel blends such as gasoline-ethanol or gasoline-methanol, it was necessary to define their composition using an arbitrary number of species, which is determined directly by the user.The minimum required number of species is seven, namely: fuel, O2, N2, CO2, H2O, CO, and H2.For each species, a conservation equation in terms of mass fractions is solved for every model element.

Fuel Model
In this simulation, the blending of gasoline and ethanol was modelled using predefined chemistry models within the software.The software offers two approaches for defining the fuel used: classical and general.In the general model, the gas composition can be described using an arbitrary number of chemical species directly specified by the user [13 [14].The minimum required number of chemical species for the general model to operate is seven: fuel, O2, N2, CO2, H2O, CO, and H2.Each species is solved for conservation equations in terms of mass fractions across the various model elements.
The input chemical species for the fuel include gasoline, ethanol, O2, N2, CO2, H2O, CO, H2, H, O, N, and OH.The fuel species are set based on fractions.For this study, the concentrations of the ethanolgasoline blend were categorized as E0 (pure gasoline), E25, E50, and E85.
The specification of the chemical species, chemical patterns, and fuel composition is depicted in Figure 3.

Figure 3. Fuel model implemented for this simulation
For this study, the AVL Boost v.2019.1 program was applied as the simulation tool.This program employs mathematical models to calculate regulated pollutant emissions.The combustion process within an internal combustion engine involves a complex series of exothermic chemical reactions.The chemical energy stored in the molecular bonds of the fuel undergoes conversion, first into thermal energy and ultimately into mechanical energy.During this high-temperature oxidation process, a multitude of chemical intermediates are generated and rapidly depleted within fractions of a second.However, certain compounds persist in very low concentrations and are released as pollutant emissions in the engine exhaust, including carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx).

NOx Model
The simulation program employs a kinetic model, developed by Pattas and Häfner, to estimate the generation of nitrogen oxides (NOx) within internal combustion engines.This model is derived from the widely recognized Zeldovich mechanism.It considers various factors including engine speed, fuel properties, and several other parameters such as pressure, temperature, equivalence ratio, volume, and mass of gas within the combustion zone.The incorporation of these parameters is vital as the theory of NOx formation is rooted in the dissociation of N2 and O2 molecules at high temperatures ahead of the flame front [14].
Among the mathematical models employed to calculate exhaust emissions, the NOx model stands out as the most intricate.It comprises six equations that operate in a state of equilibrium.The equations are derived from the following equilibrium reactions (1)-(6).

CO Model
The model utilized in Boost draws from the research conducted by Onorati.It enables the calculation of the quantity of carbon monoxide (CO) generated during combustion by solving a differential equation derived from the following equilibrium reactions ( 7)-( 8) [14].

HC Model
The formation of unburned hydrocarbons in spark ignition engines is a complex phenomenon influenced by multiple factors.Although a comprehensive understanding and a definitive predictive model are still under development, the software uses a phenomenological model to evaluate trends and behaviours regarding unburned hydrocarbons.
In a spark ignition engine, unburned hydrocarbons originate from various sources.The model identifies the following primary sources of unburned hydrocarbons:  A portion of the air-fuel mixture enters the interstitial space without being burned, as the flame is extinguished upon entering. Fuel vapor is absorbed into the oil layer and subsequently deposited on the cylinder wall during the intake and compression strokes, respectively.Desorption occurs when the cylinder pressure drops during the expansion stroke, as complete combustion is no longer feasible. The flame is prematurely extinguished before reaching the walls. Incomplete combustion of the fresh charge or the occurrence of a misfire [14].These identified sources are significant contributors to the presence of unburned hydrocarbons in the engine system.

Model calibration
The calibration of the virtual model is a crucial step in ensuring the accuracy and reliability of the simulation outcomes.It involves adjusting the model's parameters and input data to closely mimic the actual behaviour of the simulated engine.
The calibration process commences by gathering experimental data from the real engine, including measurements of pressure, temperature readings, fuel consumption, and emissions.This data serves as a reference for comparing and validating the simulation results.
The initial stage of calibration entails fine-tuning the physical parameters of the model, such as engine geometry, valve lift laws, and combustion characteristics.These parameters undergo iterative adjustments until the simulated engine's performance closely aligns with the measured data.
In cases where experimental or manufacturer-provided data is unavailable, the model is calibrated by comparing the power and torque curves obtained from simulations at full load (wide open throttle or WOT) with an external characteristic provided by the manufacturer.Consequently, the primary simulation parameters are established within the simulation control window.To assess the parameters of interest, the simulation time is set to cover 15 engine duty cycles and the average finite element dimension is set at 25mm in order to keep the computational time to a minimum.The results are then plotted on a shared graph for comparison.The power and torque curves demonstrate a close resemblance between the simulated model and the actual engine.The maximum calculation error for actual power and torque is approximately 4.8%, with an average not exceeding 5%.The overall shape of the curves also exhibits similarity.The calibration results of the model are depicted in Figures 4,5,6.Following these results obtained for the operation of the petrol engine, it can be considered that the model is ready for the change of the fuel type.

Results and discussions
Once the model was adjusted and its accuracy validated, the concentration of fuel alcohol was increased.The engine simulation was run at full load across a wide range of engine speeds, from 1000 to 5800 rpm with an increment of 1000 rpm.The fuels used for these simulations were E25, E50, and E85, corresponding to ethanol blended with conventional gasoline at volumetric percentages of 25%, 50%, and 85%, respectively.Simultaneously, the engine operation on standard gasoline was also maintained for comparison.
During the simulations, it was imperative to ensure that the engine's performance closely resembled that of operating on gasoline in order to not disturbed the end user experience.By utilizing the data acquired from each case ran on the engine model external characteristic, power and torque curves were derived along with other curves regarding the principal exhaust emissions (CO, HC, NOx).

Engine performance characteristics
Effective power is a key parameter for evaluating the performance of an internal combustion engine.To analyse its variation with engine speed, full load conditions were considered for different fuel compositions: E25, E50, E85, and pure petrol (E0).As the ethanol content in the fuel increased, the power exhibited a small decrease across the entire range of engine RPMs even if it was tried to maintain them closely similar.This behaviour was highlighted specifically when compared to high ethanol blends like E50-E85 fuels.Running the engine on regular gasoline resulted in higher power output at all engine speeds.
The higher evaporation heat of ethanol, relative to gasoline, contributes to the cooling of the air-fuel charge and increases its density.This can potentially improve combustion by bringing the equivalence ratio of the fuel blend closer to the stoichiometric state.However, the calorific value of ethanol is lower than that of gasoline, which can offset the positive effects mentioned above.Consequently, reduced power output is observed when using blended fuels.The break specify fuel consumption (BSFC) serves as an important index that measures the efficiency of a thermal engine.It is a crucial parameter in the automotive industry, utilized for evaluating the effectiveness of internal combustion engines.
In Figure 9, the relationship between break specify fuel consumption and engine speed is depicted for regular petrol and ethanol-gasoline blends.The graph illustrates a notable increase in fuel consumption as the percentage of ethanol in the fuel rises.This can be attributed to the lower heating value and stoichiometric air-fuel ratio of ethanol.Essentially, when aiming to achieve the same energy output through combustion, a greater quantity of fuel is required due to these lower values.The E85 blend demonstrates the highest specific fuel consumption among the tested blends.
Despite the rise in fuel consumption associated with higher ethanol percentage blends, the benefits outweigh this drawback.These advantages include improved combustion properties, resulting in decreased engine deposits and potentially cleaner combustion, as well as the utilization of a diverse range of renewable resources as raw materials for alcohol production.In Figure 10, the graph demonstrates the percentage increase in brake specific fuel consumption.It clearly indicates that as the ethanol percentage rises, fuel consumption also increases, resulting in a corresponding drop in engine efficiency.As expected, the decrease in effective efficiency, as depicted in Figure 11, aligns with the increasing alcohol percentage.

Enhancing engine performance through increasing the compression ratio.
One significant advantage of utilizing alcohols as fuels in internal combustion engines is their higheroctane number in comparison to petrol.This characteristic enables engines to operate with higher compression ratios, effectively preventing detonation.As a result, engine performance is enhanced, leading to improved thermal efficiency.
To maximize the engine's thermal efficiency, one approach is to raise the engine's geometric compression ratio to take advantage of the alcohol's higher-octane rating.By maintaining the other parameters constant, the compression ratio was incrementally increased through iterative adjustments.The increase continued until the calculated required octane number, as determined by the model for the alcohol blends in petrol, matched the octane number calculated for regular gasoline itself.The simulation was performed for two ethanol blends, specifically E50 and E85.
Table 3 provides the research octane numbers (RON) sourced from literature for the most commonly used alcohols in spark ignition engines.By employing the simulation software, it is possible to compute the minimum octane number needed for the engine to function without experiencing detonation.This calculation is performed using a mathematical approach [14].The calculated octane number is illustrated in Figure 12.As depicted in Figure 13, to achieve an octane number similar to that of petrol, the compression ratio is raised by 25% for E50 and 37% for E85.This elevation in the compression ratio has a direct impact on the power and torque generated by the engine.
Figure 14 illustrates the actual efficiency of the engine and it's demonstrating that increasing the compression ratio leads to enhanced engine efficiency.

Exhaust emissions
The impact of exhaust emissions on the environment is of great importance when evaluating vehicle's engine performance.To mitigate the environmental effects, the utilization of gasoline-alcohol blends has emerged as a potential solution.These blends combine traditional petrol with a certain proportion of ethanol, typically sourced from renewable resources like corn or sugar cane.Ethanol exhibits a higher 25% increase in geometric compression ratio 37% increase in geometric compression ratio oxygen content than petrol, leading to more complete combustion and consequently lower carbon monoxide (CO) emissions.Moreover, ethanol is considered a renewable fuel with an almost neutral carbon footprint since it is primarily derived from plant materials.During the growth phase, plants absorb CO2 from the atmosphere, which is subsequently released upon ethanol combustion.When considering the entire life cycle, the carbon footprint of ethanol may be lower than that of gasoline due to the ability of plants used for ethanol production to offset some of the emissions.
It is important to acknowledge that the emission levels resulting from the combustion of petrolethanol blends can differ based on various factors, including ethanol concentration, engine technology, and maintenance practices.Blends with higher ethanol content, such as E85 (comprising 85% ethanol), have the potential for greater reductions in pollutant emissions but may necessitate specific engine adaptations.Additionally, it is worth noting that the emission values obtained from the simulation represent the quantities generated after the combustion process, before undergoing any treatment in an after-treatment system.
Nitrogen oxides (NOx) are a group of chemical compounds composed of oxygen and nitrogen, which is formed through a reaction between these elements at high temperatures.It is commonly generated during the combustion of fuels such as diesel, natural gas, and organic matter.NOx, which encompasses nitrogen oxides like NO and NO2, contributes to the formation of smog in urban areas, leading to poor air quality.These emissions are also associated with acid rain as they react with ammonium, water vapour, and other substances to produce nitric acid (HNO3) and small particles.
Figure 15 illustrates the impact of fuel mixtures on NOx emissions.The graph demonstrates that NOx emissions tend to increase with higher engine speeds, reaching a peak around 4000 rpm and subsequently decreasing at maximum engine speed.Moreover, increasing the ethanol percentage in the fuel mixtures leads to a reduction in NOx emissions.
This phenomenon can be attributed to the higher ethanol content in the blends, which has the property of lowering the temperature in the combustion chamber.The lower temperature, as shown in the Figure 16, is a result of two significant characteristics of alcohol.Firstly, the latent heat of vaporization contributes to cooling the combustion chamber during fuel injection.Secondly, the production of more triatomic molecules in the combustion process increases the heat capacity of the gas, resulting in a lower combustion gas temperature.Carbon monoxide (CO) is a hazardous by-product that results from the incomplete combustion of hydrocarbon fuels.It is commonly observed in spark ignition engines, particularly when they operate at specific loads with rich fuel mixtures.However, carbon monoxide can also be produced under conditions of excess air, although the concentrations formed in such cases are minimal.These minimal concentrations usually arise from brief periods of spark ignition engine operation with rich mixtures or from regions within the combustion chamber where inhomogeneous mixtures contain localized pockets of rich mixtures.
By examining Figure 17, it can be inferred that an increase in ethanol content leads to a decrease in the amount of carbon monoxide produced.One possible explanation for this phenomenon lies in the presence of additional oxygen within the ethanol molecule, which promotes further oxidation during the combustion process.As a result, the formation of carbon monoxide is reduced.Unburned hydrocarbons (HC) comprise a diverse group of chemical compounds consisting of hydrogen and carbon.The release of unburned hydrocarbons occurs when there is an insufficient amount of oxygen to support complete combustion.During the combustion process, hydrocarbon compounds are generated through the fragmentation of extended molecular chains and subsequent transformations of the original fuel, resulting in the formation of hydrocarbon compounds that were not initially present in the fuel.However, it is worth noting that the lower temperature in the combustion chamber may also lead to an increase in the fraction of unburned hydrocarbons, which can have environmental implications [16].

Figure 18. The amount of accumulated HC produced during combustion
Figure 18 provides a visual representation of the impact of ethanol-gasoline blends on HC emissions.The graph demonstrates that as the proportion of ethanol increases, the concentration of HC decreases.The reduction in HC emissions can be attributed to similar factors as the decrease in CO concentration, as both are influenced by the combustion process.Ethanol promotes more complete combustion due to its higher oxygen content, leading to a shift towards stoichiometric combustion and a decrease in the emission of unburned hydrocarbons.
During the complete combustion of fuel, the carbon present in the fuel structure is converted into carbon dioxide (CO2), which accounts for approximately 13.5% of the volume of the exhaust gas composition.The quantity of carbon dioxide produced serves as a direct indicator of fuel consumption.While CO2 is a natural component of the Earth's atmosphere and not classified as a pollutant, it is a significant contributor to the greenhouse effect, which contributes to global warming and climate change.
Figure 19 depicts the relationship between engine speed, as shown on an external engine characteristic, and the emissions of carbon dioxide resulting from combustion.

Conclusion
The findings of this study highlight the importance of continued research and development in the field of ethanol-blended fuels to maximize their performance and emission advantages.When using high-volume percentage blends of alcohols in gasoline (70-90% vol.), fuel consumption can rise with about 50%, as shown in Figure 10.However, this is not a concern for countries like Brazil, which can leverage the abundant biomass from sugar production to produce ethanol.Simulations indicate that an optimal range of 25 to 50% vol.ethanol in gasoline can improve fuel quality without significantly impacting consumption.
In general, the production of CO emissions is heavily influenced by the excess air ratio and the C/H ratio of the fuel.As the percentage of ethanol increases, the concentration of both CO and HC decreases.Blends containing 85% vol.ethanol (E85) exhibit the lowest CO and HC emissions.
NOx emissions exhibit an upward trend with increasing speed, followed by a sharp decrease around the nominal speed.The use of E85 fuel yields the lowest NOx emissions.
Ethanol, derived from renewable sources, offers the potential to reduce global greenhouse gas emissions when blended with petrol.Although burning ethanol releases CO2, the carbon footprint can be offset by the plants used for its production, making it a more environmentally friendly option.
Alcohols demonstrate good resistance to detonation.By adjusting the compression ratio when utilizing ethanol blends in petrol, it is possible to enhance effective engine efficiency while avoiding detonation.
Blends of ethanol and gasoline, particularly those with higher ethanol concentrations like E85, may require specific engine modifications to optimize performance.These modifications could involve adjustments to the fuel system, materials, and engine control strategies.Ensuring engine compatibility and implementing proper maintenance practices are crucial for maximizing the benefits of ethanol and gasoline blends.
In summary, ethanol-gasoline blends offer advantages such as reduced emissions, decreased greenhouse gas emissions, and economic sustainability, albeit at the expense of slightly lower engine performance.However, achieving optimal results necessitates engine compatibility, appropriate maintenance, and continuous research efforts to further enhance the performance and emission benefits of ethanol-blended fuels.

Figure 2 .
Figure 2. Excess air map (λ) used in the model

Figure 4 .Figure 5 .Figure 6 .
Figure 4. Calibrating the power developed by the engine

Figure 10 .
Figure 10.Percentage change in the break specify fuel consumption

Figure 11 .
Figure 11.Engine effective efficiency determined for different ethanol-gasoline blends

Figure 12 . 13 Figure 13 .
Figure 12.The octane number calculated from the simulation

Figure 14 .
Figure 14.The actual engine efficiency before and after increasing the compression ratio

Figure 15 .Figure 16 .
Figure 15.The amount of accumulated NOx produced during combustion

Figure 17 .
Figure 17.The amount of accumulated CO produced during combustion

Figure 19 .
Figure 19.The amount of accumulated CO2 produced during combustion

Table 2 .
[12]stoichiometric air-fuel ratio and lower heating value for different blends of alcohols and gasoline[12]