The Impacts of Ethanol-Gasoline Blended Fuels on the Pollutant Emissions and Performance of a Spark-Ignition Engine : An Empirical Study

The blending of ethanol with imported gasoline types has been compulsory since January 1, 2018, with the Communiqué No. 30098 published in the Official Gazette in Turkey. In line with this, it is aimed to determine the effects of gasoline-ethanol blends on engine performance and exhaust emissions resulting from the use of an SI engine. The experiments were performed at different speeds for different ethanol-gasoline blends (E0, E10 and E20) under full load in a four-stroke, single-cylinder engine. As a result, air-fuel mixture ratios, torque, power, vibration and noise values, specific fuel consumption, harmful gas emissions (CO, HC, CO2 and NOx) was measured. Measurements were obtained with 96% accuracy. In this study, carbon monoxide and hydrocarbon emissions decreased, carbon dioxide and nitrogen oxide emissions increased by the addition of ethanol to gasoline. On the other hand, the addition of ethanol has also led to a certain increase in brake specific fuel consumption, vibration and noise levels.


I. INTRODUCTION
The more studies and developments for the internal combustion engines (ICEs) have gained momentum particularly after the late of the 1800s.Nicolaus Otto, Rudolph Diesel, Gottlieb Daimler, Karl Benz and Henry Ford contributed and gave the direction of the new developments on the automobile world between the years of 1800-1930 and also directly helped to the invention of compression ignition engine (CI) and spark ignition (SI) engine [1].Even today, their outstanding attempts in vehicular systems still have a vital role and in use.
Currently, ICEs have been the foundation for the accomplished achievements for many industrial technologies such as the applications of power generation, military, telecommunication, agriculture, transportation, offshore drilling, marine and generator [2].On the other hand, the popularity of ICEs and its use in nearly all sectors have caused great energy consumption and undoubtedly played a leading role of the most of the depleting fossil fuel sources [3] because ICEs have been powered by the burning of the fossil fuels and the reserves of the fossil fuels have a finite.
Today, there are nearly 380 million commercial vehicles and 1.2 billion passenger cars across the world.These vehicles and cars have gained the motion as a result of the burning of fossil fuels [4].It is predicted that fossil fuels will completely run out in near future.That is why we need to find an alternative energy source instead of fossil fuels and decrease our dependency on fossil fuels, immediately.Therefore, it is of great importance that the new energy source to replace fossil fuels is also in equipment with ICEs.Although many alternatives are considered in this context, biomass (bioenergy) for ICEs is the most accepted energy source.In addition, the use of biomass has the ability to be applied directly to the fuel tank without any modification on the vehicle.There are basically two methods for biomass power generation for ICEs.These are biofuels obtained with liquid-biomass and gas-biomass blends.The most preferred biomass for ICEs is ethanol (known as ethyl alcohol, the chemical representation C 2 H 5 OH) and methanol (known as methyl alcohol, the The Impacts of Ethanol -Gasoline Blended Fuels on the Pollutant Emissions and Performance of a Spark -Ignition Engine: An Empirical Study chemical representation of CH 3 OH), respectively.The low thermal values of methanol and ethanol compared to gasoline, the low fuel values of the new fuel formed by the mixing of these alcohol species with the gasoline is also lower than the thermal value of pure gasoline.Therefore, blends of methanol-gasoline [5,6] and ethanol-gasoline [7,8] increase specific fuel consumption compared to pure gasoline.However, many studies conducted in the literature have proved that the new mixture causes a great deal of reduction in harmful gas emissions such as CO (carbon monoxide), HC (hydro carbon) and NO (nitrogen oxide).Therefore, the use of biomass in the fuel tank turns fossil fuels into a cleaner form of energy source.
This study mainly focused on experimentally investigation and comparing the motor performance by using various rates of ethanol and gasoline blends.Ethanol is the most popular source of renewable energy for spark ignition engines [9,10].On the other hand, ethanol is a pure substance and includes nearly 34.7% by weight of oxygen.Hence, the stoichiometric air-fuel ratio of ethanol is 9 and this ratio is less than the gasoline stoichiometric ratio.Also; ethanol also has a higher octane number than gasoline.As a higher octane number fuel, ethanol allows it to withstand higher compression ratios when mixed with gasoline [11,12].Furthermore, ethanol is a safe source of energy for the purposes of storage and transportation compared to gasoline fuels owing to the higher ignition temperature and flash point [13].In the literature, it is possible to come across many studies focusing on engine performance effects, such as vibration and noise, exhaust gas emissions of fuel types and mixtures [14] When the measurements of the vibration and noise values at the same cycles were evaluated, the experiment values in the pure gasoline blends were lower than the vibration and noise values obtained from the fuels including E25 and E50.The highest vibration and noise values for all mixtures were obtained at 2500 rpm and for E50 fuel type.The results indicated that as the ethanol content increased, there was an increase in vibration and noise.In addition, there are studies in which ethanol is added to diesel, and the results of these studies are similar to those in which ethanol is mixed by gasoline [16].Ioannis et al. (2011) in their study of different rates (10%, 20% and 30% by vol.) of ethanol and methanol bioenergy sources at different speeds (1000, 1300, 1600 and 1900 rpm) investigated by a spark ignition engine.Compared to the experiment results, at 1000 rpm engine, the lowest vibration value was reached when E10 fuel was used, while E20 fuel with 7.41 m/s 2 at an engine speed of 1900 rpm and E81 fuel with 6.81 m/s 2 had the highest vibration values [17].Also, there is a great deal of study including harmful exhaust gas emissions arising from fossil fuels in ICEs.Today, the harmful exhaust gas emissions have caused millions of deaths and suffered serious diseases for humans worldwide [18].
Therefore, the reduction of these harmful gases from ICEs has significant importance.In line with these, Palmer (1986) experimentally investigated the impacts of the various composition rates of ethanol and gasoline compositions and his experiment results reported that addition at the rate of 10% ethanol into gasoline increased the engine power output at the rate of 5%.Also, it was observed that each 10% ethanol added into gasoline gave rise an increase to octane number.Palmer highlighted that the addition 10% of ethanol into gasoline might reduce the Ümit Ağbulut, Suat Sarıdemir, Gökhan Durucan carbon monoxide emission concentration up to 30% [19].Alexandrian and Schwalm (1992) showed that the air fuel ratio (AFR) has a great effect on the amount of the CO emission.In the related study, it was highlighted that instead of gasoline alone, the composition of the ethanol and gasoline could cause the less NOx (nitrogen oxides) and CO emissions by making possible the fuel-rich condition [19].Abdel-Rahman and Osman (1997) explored the effects of adding ethanol at the rate of 10%, 20%, 30% and 40% to gasoline in a variable compression ratio engine.
The authors determined that the enhancement of ethanol content increased the octane number whilst decreasing the heating value.The most obvious influence in terms of increasing the octane number was obtained through 10% addition of ethanol into gasoline.Under different engine compression ratios, the optimum composition ratio of ethanol and gasoline was reported as 10% ethanol and 90% gasoline [21].Bata et al. (1989) experimentally investigated the different ethanol-gasoline blends in engines and observed that the ethanol decreased the CO and UHC (unburned hydrocarbon) emissions to some degree.Owing to the better oxygenated characteristic and the wide flammability of ethanol than pure gasoline, the blends including ethanol caused a reduction in CO emissions [22].On the other hand, the studies of Rideout et al. (1994) and Chao et al. (2000) reported that the composition of the ethanol and gasoline fuels have increased the emission of acetaldehyde, formaldehyde and acetone between 5.12-13.8times than those of from gasoline.Even though the using ethanol in engines will cause an increase in the aldehyde emission, this damage to the atmosphere arising from the emitted aldehyde is far less than the poly-nuclear aromatics arising from the burning of the gasoline alone [23,24].In comparison with gasoline alone, using a higher rate of alcohol into gasoline can clearly make the air quality better [25].
Based on these literature studies, it is clearly understood that the use of ethanol and gasoline blended fuels in engines can effectively cause the lower the harmful exhaust gas emissions without any modifications in the vehicular systems and fuel tank as well.According to the Turkish Official Gazette no.30098, come into force on 1 January 2018, the blending of biodiesel with ethanol produced from domestic agricultural products or vegetable waste oils at least 3% and at least 0.5% in the engine has been made compulsory [4].In the future, it is thought that the amount of ethanol blended into gasoline and diesel will also be increased due to the negative effects of fossil fuels on the environment and human health, the decrease in the reserves of fossil fuels and the increasing oil prices.

II. MATERIAL & METHOD
In this study, we experimentally investigated the effects of the engine performance and harmful exhaust gas emission of ethanol-gasoline blended fuels at different engine speeds and under full load.The ethanol and gasoline were blended by 0% (E0=pure gasoline), 10% (E10) and 20% (E20) volumetrically.The properties of commercial gasoline and ethanol are given in Table 1.A schematic view of the experimental setup is seen in Fig. 1.The experiments for each fuel type were performed at the same operating conditions.In the experiment part of this study, we used the single cylinder, 4-stroke and aircooled, HONDA GX390 engine and a 15 kW power absorbable electric dynamometer.
In the experimental section of this study, we used the single cylinder, 4-stroke and air-cooled, HONDA GX390   To obtain the torque values of the system, KiTorq System is used in this study and this system has a torque measuring flange system consisting of the Kistler Type 4550A.The technical specification of the torque measurement device is given in Table 4.In this study, harmful exhaust gas emission values were measured for all experiments and variables.Fort his measurement, the exhaust gas emissions were determined by K Test emission measuring device and the technical specification of this device are given in Table 5.

III. ERROR ANALYSIS
The experiments cannot be measured with 100% accuracy owing to many factors such as calibration, test conditions-planning, instrument selection, reading, the absence of homogeneity of materials used in experiments, from ambient conditions, the range of measurement devices and even the connection type-points and locations of the measurement probes on the experiment setup [28].To decrease the effects of these factors, it is suggested that the experiments in the studies were performed at least three times to ensure the reality of the obtained results and to confirm the repeatability under the same conditions, and then reported the averages of this three measurement.
Actually, the error and uncertainty analysis are one of the most effective methods to evaluate and determine the experimental results.Hence, the accuracy rates of all measurement devices using the experimental section of this study are given in Table 6.Total error rate (e r ) in this study are calculated using the following equation.As is known, torque is the ability potential of the engine to work.In ICEs, the internal filling ratio is low and the torque value is less because the filling ratio is low and insufficient at high speeds.Therefore, the most efficient operating conditions are obtained at medium speeds [29].Power and torque changes depending on the engine speed for all fuel blends are given in Figure 2. As shown in figure x, the engine power and torque values of the ethanol-containing fuels are lower in all cycles compared to gasoline alone.This is due to the fact that ethanol-containing fuels have a lower thermal value than gasoline, as shown in Table 1.Thus, during the combustion of ethanol-containing fuels, less energy is generated at the engine's operating time [30].According to the experimental results, the maximum motor torque for all fuels reached a maximum value at 2500 rpm. to the ethanol content in the fuel mixtures.This is because of the lower heat value of ethanol compared to gasoline alone (Table 1).As the ethanol content in the fuel mixtures increases, the energy amount of the fuel mixtures decreases and the engine consumes more fuel in order to provide the same power under the same operating conditions.As shown in Fig. 3, the minimum specific fuel consumption for all fuel mixtures is around the maximum torque cycle.
In ICEs, the speed range in which the highest engine torque is obtained is accepted to be the most efficient operating The Impacts of Ethanol -Gasoline Blended Fuels on the Pollutant Emissions and Performance of a Spark -Ignition Engine: An Empirical Study range.In this range, the high volumetric and combustion efficiency reduces specific fuel consumption and increases engine torque [29].However, the specific fuel consumption for all fuel blends increases at low and high engine speeds.
As the engine generates less power at low speeds, the specific fuel consumption increases for all fuels due to increased frictional forces and reduced volumetric efficiency at high speeds.presented good results in the literature [38][39][40][41][42][43] because the optimization helps not only to achieve the optimum value with less trial but also to make the possible evaluated the parameters and used effectively.
. Taghizadeh et al. (2016) investigated of the effects at different composition rates of ethanol and gasoline blends (2%, 4%, 6%, 8%, 10% and 12%) and at different engine speeds (1600, 1700, 1800, 1900 and 2000 rpm) for the engine performance of the blends.The results clearly demonstrated that the vibration values increased depending on the increasing in the engine.For different fuel compositions, the compositions containing 4% ethanol content for all experiments at the same speed showed the lowest vibration values, while the compositions containing 12% ethanol showed the highest vibration values [15].In another similar study, Keskin (2010) investigated the vibration and noise values of the fuels with 25% and 50% ethanol content at 1500, 2000 and 2500 rpm engine revolutions.The results of the experiment revealed a linear relationship between vibration values and noise values.

engine and a 15
kW power absorbable electric dynamometer.Technical specifications of the engine are shown in Table 2. Additionally, the vibration data of the system were obtained by a data acquisition device capable The Impacts of Ethanol -Gasoline Blended Fuels on the Pollutant Emissions and Performance of a Spark -Ignition Engine: An Empirical Study of conducting a four-channel VIBROTEST 80 model FFT analysis with a single-axis piezoelectric accelerometer.It has Brüel & Kjaer software and hardware system.After that, the data were analyzed by Hanning filtering method at 6400 resolution.Vibration data up to 5 kHz were obtained in the experiments.The total mean of the vibration data was calculated by the mean square root (RMS) method and the unit of the acceleration is g (m/s 2 ).

Figure 1 .
Figure 1.Schematic view of the experimental setup.

Figure 2 .
Figure 2. Torque and Power curves for all fuel blends at different engine speed

Figure 3 .Figure 4 .Figure 5 .
Figure 3.The curves of BSFC and Engine speed Figure 4 indicates exhaust gas emissions such as CO, HC, CO 2 and NOx depending on engine speed and fuel blends.Figure 4a shows the effects of fuel blends on CO emissions depending on engine speed.As shown in Fig. 4a, CO emissions have been reduced with both increasing the ethanol content in the fuel blends and engine speed.As increasing the ethanol content in the fuel blends brought the air-to-fuel ratio (AFR, λ) as close to 1 as shown in Fig. 5 and consequently increased combustion quality [31.32].Additionally, the carbon content of the gasoline is greater than ethanol.Carbon in the fuel turns into carbon monoxide during combustion.Thus, CO emissions also are reduced depending on the ethanol content in the fuel blends.In addition, because the latent heat of evaporation of ethanol is greater than gasoline, the air absorbing into the engine cools at the time of vacuum and the volumetric efficiency increases.The increased volumetric efficiency reduces CO emissions by providing a greater degree of complete combustion.In addition, the high oxygen content of ethanol also leads to a decrease in CO emissions by increasing the combustion quality[33].At high engine speeds, the air fuel mixture improves combustion as a better homogeneity due to increased turbulence.Therefore, CO emissions tend to

Figure 6 .
Figure 6.Vibration and Noise levels depending on the engine speed To sum up, carbon monoxide and hydrocarbon emissions arising from burning ethanol and gasoline blends were reduced as compared to gasoline alone.On the other hand, the increase in ethanol content in the fuel blends caused the increase in carbon dioxide and nitrogen oxide emissions.In addition, the ethanol content caused in a certain increase in specific fuel consumption, vibration and noise levels.However, ethanol has the potential to be used on the vehicle without any modifications.It is suitable for use in vehicles by improving the negative properties resulting from the use of ethanol.As an advice for future works, experiment numbers could be decreased by a mathematical optimization study.There are a number of various studies applying different optimization method and

TABLE VI THE
ACCURACIES OF THE EXPERIMENTAL DEVICES USING IN THIS STUDY