energies

Article The Effect of Using -Gasoline Blends on the Mechanical, Energy and Environmental Performance of In-Use Vehicles

Juan E. Tibaquirá 1, José I. Huertas 2,* ID , Sebastián Ospina 1, Luis F. Quirama 1 and José E. Niño 2

1 Mechanical Engineering Department, Universidad Tecnológica de Pereira, Pereira 660003, Colombia; [email protected] (J.E.T.); [email protected] (S.O.); [email protected] (L.F.Q.) 2 School of Science and Engineering, Energy and Climate Change Research Group, Tecnológico de Monterrey, Monterrey 64849, Mexico; [email protected] * Correspondence: [email protected]; Tel.: +52-1-722-100-9417

Received: 12 December 2017; Accepted: 11 January 2018; Published: 17 January 2018

Abstract: The use of ethanol in gasoline has become a worldwide tendency as an alternative to reduce net CO2 emissions to the atmosphere, increasing gasoline octane rating and reducing dependence on petroleum products. However, recently environmental authorities in large urban centers have expressed their concerns on the true effect of using ethanol blends of up to 20% v/v in in-use vehicles without any modification in the setup of the engine control unit (ECU), and on the variations of these effects along the years of operation of these vehicles. Their main concern is the potential increase in the emissions of volatile organic compounds with high formation potential. To address these concerns, we developed analytical and experimental work testing engines under steady-conditions. We also tested carbureted and fuel-injected vehicles every 10,000 km during their first 100,000 km of operation. We measured the effect of using ethanol-gasoline blends on the power and torque generated, the fuel consumption and CO2, CO, NOx and unburned emissions, including volatile organic compounds (VOCs) such as acetaldehyde, formaldehyde, benzene and 1,3-butadiene which are considered important ozone precursors. The obtained results showed statistically no significant differences in these variables when vehicles operate with a blend of 20% v/v ethanol and 80% v/v gasoline (E20) instead of gasoline. Those results remained unchanged during the first 100,000 km of operation of the vehicles. We also observed that when the vehicles operated with E20 at high engine loads, they showed a tendency to operate with greater values of λ (ratio of the actual air-fuel ratio to the stoichiometric air-fuel ratio) when compared to their operation with gasoline. According to the Eco-Indicator-99, these results represent a minor reduction (<1.3%) on the impact to human health, and on the deterioration of the ecosystem. However, it implies a 12.9% deterioration of the natural resources. Thermal equilibrium analysis, at the tailpipe conditions (~100 ◦C), showed that ethane, formaldehyde, ethylene and ethanol are the most relevant VOCs in terms of the amount of mass emitted. The use of ethanol in the gasoline reduced 20–40% of those emissions. These reductions implied an average reduction of 17% in the ozone formation potential.

Keywords: E10 and E20; ozone formation potential; vehicular emissions; volatile organic compounds (VOCs) emissions in vehicles; eco-indicator

1. Introduction Currently, road transport is the largest consumer of petroleum-derived fuels in the world (~25%), and therefore it is the main emitter of atmospheric pollutants in urban centers (>75%) [1]. Due to the growing energy demand, the increasing fuel prices, the severe issues in city centers, and the more restrictive environmental regulations to the road transport sector, nations worldwide

Energies 2018, 11, 221; doi:10.3390/en11010221 www.mdpi.com/journal/energies Energies 2018, 11, 221 2 of 17 are vigorously developing and finding sources and new technologies to reduce the vehicular emissions of air pollutants [2,3]. Ethanol is a fuel produced mainly from crop materials such as sugarcane and corn, which makes it an attractive substitute for gasoline for reducing dependence on fossil fuels and reducing CO2 net emissions released into the atmosphere. Additionally, ethanol has a higher octane number than gasoline (~108.5 vs. 84.4, Table1)[ 4] which implies that ethanol-gasoline blends have a higher octane number than traditional gasoline. Therefore, the use of ethanol becomes a partial alternative for providing high-octane fuels (~94), required for modern high compression ratio engines. As the efficiency of engines increases with the engine’s compression ratio, which demands a fuel with a high octane number, the use of ethanol in an engine can improve the energy efficiency [5]. Ethanol is also characterized by having a higher heat of vaporization than gasoline (Table1). This aspect makes the temperature of the intake manifold lower, which increases air-fuel mixture density, therefore increasing the engine’s volumetric efficiency. However, a higher heat of vaporization also causes lower temperatures and burning velocities, which could potentially cause higher CO and HC emissions. The Reid Vapor Pressure (RVP) of ethanol is much lower than that of gasoline (Table1), and the resulting lower volatility reduces the VOCs emissions during pumping processes. However, it can also cause difficult cold transient of the engine during the warm-up phase. The ethanol-gasoline blended fuel does not have an RVP value that ranges linearly with the percentage of ethanol in the blends. In fact, the RVP of the blended fuel rises with the ethanol content until reaching a maximal value at around 15% v/v of ethanol addition [6]. At higher ethanol percentages, the RVP declines. Finally, the energy content of ethanol is approximately one third lower than that of gasoline (Table1). Thus, the combustion temperature is lower which reduces the formation of NOx. However, the heating value of the ethanol-gasoline blended fuel will decrease with the ethanol content and therefore more mass of fuel will be required to obtain the same engine power output [2].

Table 1. Properties of ethanol-gasoline blends.

Property Method/References Gasoline E10 E20 E100 Density (kg/m3) ASTM D369 733 739 746 790.7 LHV (kJ/kg) [7] 43000 41282 39591 26950 Latent Heat of Vaporization [8] 305 - - 840 (kJ/kg) RVP (kPa) ASTM D323 62 - - 14 RON ASTM D2699 88.5 90.7 94.8 115 MON ASTM D2700 80.3 81.6 83.3 102 AKI (RON + MON)/2 84.4 86.2 89.1 108.5 Stoichiometric air/fuel ratio - 14.49 13.89 13.31 8.87

Many authors have studied the performance of spark-ignition engines on engine-dynamometers, when they operate with ethanol-gasoline blends, controlling the fuel-air ratio, under steady-state conditions. These studies have found that the use of blends with low concentrations of ethanol (<20% v/v ethanol) have a negligible effect on the power and torque generated by the engine [9–11]. Likewise, a negligible effect on CO2 emissions and a slight reduction on CO, NOx and HC emissions has been found [4,9,12,13]. However, the validity of these results is limited to the particular conditions under which the tests were carried out and by the reduced number of engines tested. Furthermore, conclusions drawn from testing engines under laboratory conditions are not necessarily the ones expected for new and in-use vehicles, when they circulate in the city operating with ethanol-gasoline blends without any previous adjustment in the programming of their respective engines. The effect of using ethanol-gasoline blend on carbureted and fuel-injected vehicles for a long period of time (>10,000 km) has not been studied yet either. Recently, it was reported that the use of ethanol-gasoline blends in vehicles increases the emission of volatile organic compounds (VOCs) [2], especially acetaldehydes compounds, which are precursors Energies 2018, 11, 221 3 of 17

Energiesof tropospheric 2018, 11, 221 ozone in urban areas. This contradictory result has reversed the decision of government3 of 17 authorities, previously in favor of the use of ethanol-gasoline blends in large urban centers such as centersMexico such City, whereas Mexico the mainCity, environmentalwhere the main problem environmental is the high problem concentration is the high of tropospheric concentration ozone. of troposphericAn analytical ozone. study isAn required analytical to explore study is if thisrequired result to is explore a natural if tendencythis result of is the a natural ethanol-gasoline-air tendency of thecombustion ethanol-gasoline-air process inside combustion the engine process or a particular inside the result. engine or a particular result. To address these issues, we studied analytically and experimentally the the effect effect of of using low low ethanol content (<20% v/vv) )in in the the mechanical mechanical and and environmental environmental performance performance of of in-use in-use sedan-type gasoline fueled fueled vehicles, vehicles, without without any any prior prior adjustment adjustment to to the the programming programming of of the the engine. engine. Initially, Initially, we usedused aa zero-dimensional zero-dimensional model model that that simulates simulates the the operation operation of the of engine the engine and estimated and estimated the power, the power,fuel consumption, fuel consumption, and the generatedand the generated emission emis of airsion pollutants of air pollutants under different under working different conditions. working conditions.Then, we measured Then, we measured these variables these variables in two engines in two typicallyengines typicall used iny used sedan-type in sedan-type vehicles, vehicles, under underlaboratory laboratory conditions conditions at different at di heightsfferent aboveheights sea above level. sea Finally, level. we Finally, evaluated we theevaluated same variables the same in variablesfour vehicles in four every vehicles 10,000 kmevery of operation 10,000 km over of theiroperation first 100,000 over thei kmr of first operation, 100,000 running km of underoperation, very runningdifferent under weather very conditions different andweather altitudes. conditions and altitudes.

2. Methodology Methodology Figure 11 illustratesillustrates thethe methodologymethodology implementedimplemented toto evaluateevaluate thethe effecteffect ofof usingusing E20E20 onon thethe mechanical, energy energy and and environmental performance performance of of in-use in-use vehicles, vehicles, operating operating on on a a daily basis under different real altitude and climate conditions. conditions. This This methodology methodology involved involved an an analytical analytical phase, phase, an experimental phase testing the engines under la laboratoryboratory conditions and finally finally an experimental phase testing thethe vehiclesvehicles under under on-road on-road conditions. conditions. In In all all cases, cases, the the power power generated generated (P), ( specificP), specific fuel fuelconsumption consumption (SFC) (SFC) and COand2, CO CO,2, NOxCO, NOx and VOCs and VOCs emission emission index index (EI) were (EI) observedwere observed when thewhen engine the engineor the vehicleor the vehicle was fueled was withfueled gasoline with gasoline and E20. and E20.

Figure 1. Illustration of the general methodology used to evaluate the effects of using ethanol-gasoline Figure 1. Illustration of the general methodology used to evaluate the effects of using ethanol-gasoline blends on the mechanical, energy and environmental performance of in-use vehicles during their blends on the mechanical, energy and environmental performance of in-use vehicles during their useful useful life of operation. life of operation. 2.1. Studying the Effect of Fuel Change Using a Zero-Dimensional Model for Engines 2.1. Studying the Effect of Fuel Change Using a Zero-Dimensional Model for Engines The analytical study seeks to establish the thermodynamic expected effects of using ethanol- The analytical study seeks to establish the thermodynamic expected effects of using ethanol- gasoline blends on vehicles. Equations (1)–(5) estimate SFC, P, τ and EI for the given engine geometry gasoline blends on vehicles. Equations (1)–(5) estimate SFC, P, τ and EI for the given engine geometry (Ed, Nc, r) and its operating parameters (RPM, λ). (Ed, Nc, r) and its operating parameters (RPM, λ). = . (1) mf SFC = (1) P = (2)

60 = (3) 2

Energies 2018, 11, 221 4 of 17

. P = ηth m f LHV ηm (2) 60 P τ = (3) 2π RPM . . A mi = xi m f (1 + λ ( /F)s) (4) . m EI = i (5) i P

To estimate the work generated per cycle (δw) and the thermal efficiency (ηth) of the engine, we used the CIMA model, which is a zero-dimensional steady-state model similar to the Otto cycle [7]. In the CIMA model, the combustion process is modeled through a classical chemical thermo-equilibrium analysis, which involves solving a system of nonlinear equations with as many equations of chemical equilibrium as species considered, equations for species conservation and an extra equation for energy conservation. Additionally, it considers energy losses in the compression and expansion processes through the second-law of thermodynamics efficiency concept. For estimating the mass of the pollutant i emitted at the vehicle’s exhaust pipe (mi), we calculated the thermo-chemical equilibrium composition of combustion byproducts at the temperature of the exhaust pipe. Results of this model have shown a high correlation (R2 > 0.9) with experimental results carried out on an engine test bench and on vehicles by on-road tests. The main assumptions of this model are that the working substance behaves as an ideal gas and that the equilibrium composition is reached at the temperature of exhaust gases, except for NOx, where it is assumed that the NOx mass emitted by the exhaust pipe is equal to the one formed at the end of the combustion process. Using the CIMA model, SFC, P, τ and EI were estimated using the data specified in Table2 as input data.

Table 2. Input data for estimating fuel consumption and mass emissions of air pollutants.

Parameter Symbol Units Range

Ambient pressure P0 kPa 75 Ambient temperature T0 K 288 Fuel - - Gasoline–E100 Compression ratio r - 9.4 Engine displacement Ed cm3 1597 Lambda λ - 0.8–1.5 RPM - - 1000–5000

2.2. Evaluation of the Fuel Change in Engines To include technological aspects in the evaluation of the effect that the fuel change causes in the performance of vehicles, two typical engines frequently found in sedan vehicles were evaluated. ◦ The first engine operated at 1000 masl (T0 = 20 C and P0 = 87 kPa) while the second engine operated at ◦ 2400 masl (T0 = 15 C and P0 = 75 kPa). In both cases SFC, P, τ and EI of air pollutants were evaluated on an engine test bench under steady-state conditions as a function of RPM, λ and engine load (inlet pressure). The tests were limited to gasoline, E20 gasoline and E20. Table3 describes the technical characteristics of the engines. To test engine 1 we used a Dynapack 2WD-2 cube dynamometer (oil hydraulic dynamometer, 0–2000 Nm range and 5 Nm of resolution) to measure engine mechanical performance variables, a Vgate OBD scan and a LabView homemade software interface to read engine sensors (RPM, TPS position). We used a SUM–290122 fuel tank and 6 kg Fenix Lexus electronic scale (0.5 g of resolution) for the measurement of fuel consumption. We used a Galio Smart 2000X gas analyzer to determine composition and an Innovate LC-1 lambda sensor for the determination of λ values (Table4). Energies 2018, 11, 221 5 of 17

To test engine 2 we used a SuperFlow SF902 engine test dynamometer (hydraulic, 0–1627 Nm range, and 5 Nm of resolution, (Superflow, Des Moines, IA, USA). We measured engine operational parameters (engine RPM, temperatures, TPS position) via an ELM327 OBD scan and a LabView software interface. We measured fuel consumption in volumetric form using an auxiliary calibrated 1 4 -inch glass tube and a DVT Legend Vision camera. For the determination of exhaust gas composition, we used an FGA-4000XD gas analyzer (Infrared Industries, Hayward, CA, USA) (Table4). We used an external engine Electronic Control Unit to establish the λ values of engine operation.

Table 3. Technical description of the engines used to evaluate changes in their performance when fueled with gasoline and E20.

Engine 1 Engine 2 Model Chevrolet Sail/LPDA Chevy Powertrain DOHC GM Z16SE Displacement [cm3] 1398 1597 Orientation Transversal Longitudinal Compression ratio 10.2 9.4 Cylinder diameter/Stroke 79.8 mm/81.8 mm - Distribution 4 valves per cylinder/2 camshafts 2 valves per cylinder/1 camshaft Fuel System Indirect fuel injection Sequential multipoint fuel injection Power rating 76 kW @ 6000 RPM 74.5 kW @ 5600 RPM Torque 130 Nm @ 4200 RPM 135.6 Nm @ 3200 RPM

Table 4. Technical characteristics of the instrumentation used in this work.

Lab 1 Lab 2 Trademark Dynapack 2wd-2 SuperFlow SF902 Range 0–2000 Nm 0–1627 Nm Dynamometer Power capacity 300 kW 1119 kW Maximum speed 2450 hub RPM 15,000 RPM Trademark Galio Smart 2000X gas analyzer FGA 4000XD gas analyzer Variable Method Range Accuracy Method Range Accuracy CO Infrared 0–10 % V 0.06% Absolute, 5% Relative Infrared 0–10 % V ±5% Gas Analyzer CO2 Infrared 0–20 % V 0.03% Absolute, 5% Relative Infrared 0–20 % V ±5% HC Infrared 0–10,000 ppm 4 ppm Absolute, 5% Relative Infrared 0–5000 ppm ±5% O2 Infrared 0–25 % V ±2% Relative Infrared 0–25 % V ±5% NOx Infrared 0–2000 ppm 32 ppm Absolute Infrared 0–5000 ppm ±4% Trademark Innovate Motorsport LC-1 Lambda sensor Variable Response time Range Accuracy λ <100 ms 0.5–8.0 ±0.007

2.3. Evaluation of the Fuel Change in Vehicles To include all the operational aspects which have an impact on the real performance of the vehicles, we evaluated four sedan type vehicles typically used in Latin America. Two of them were carbureted vehicles (Chevrolet Sprint) and the other two had electronic fuel injection (Chevrolet Aveo). Table5 describes the technical characteristics of these vehicles. The fuel-injected vehicles were brand new at the time tests started. Due to environmental regulations, it was not possible to obtain brand new carbureted vehicles at that time. Therefore, we purchased two two-year old carbureted vehicles and provided them with full mechanical maintenance, which included the replacement of all powertrain elements with original spare parts, except for the engine block and the transmission. The carbureted vehicles were included in this analysis because there are still a significant number of vehicles operating with this technology and the fuel change can generate big changes in their performance, to the extent that it can generate adverse changes that could frustrate the benefits pursued by the authorities in the promotion of biofuel use. For the experiments, one fuel-injected and one carbureted vehicle operated with E10 and the other two with E20. The vehicles were subjected to normal operating conditions, always following the Energies 2018, 11, 221 6 of 17 same routes. During the road tests, drivers were exchanged every two hours to eliminate potential deviations generated by the driving style. The performance of the vehicles was monitored every ~10,000 km. SFC, CO, CO2 and HC emission indices were measured when the vehicles reproduced the New European Driving Cycle (NEDC) on a chassis dynamometer. The instruments used for all tests in this case were the same as those described in Table4 for the evaluation of engine 1 under steady-state conditions. The properties of the fuels used during the experimental work are shown in Table1.

Table 5. Vehicles’ technical characteristics in long-term tests.

Chevrolet Sprint 1997 Chevrolet Aveo 2010 Engine Displacement (cm3) 990 1.598 Engine compression ratio 8.5:1 9.5:1 Weight (kg) 690 1165 Fuel System Carburetor Sequential multipoint fuel injection Transmission Manual transmission, 5 speeds Manual transmission, 5 speeds Power rating 37 kW @ 5100 RPM 82 kW @ 6000 RPM Torque 77 Nm @ 3200 RPM 145 Nm @ 3600 RPM

3. Results

3.1. Power and Torque Figure2 shows the power generated by the vehicles when they operate with ethanol-gasoline blends. Analytical Results: Assuming that the mechanical efficiency of the engine remains unaffected by the fuel change, the mechanical power generated by the engine decreases with the ethanol content in the fuel. When E20 is used instead of gasoline, the power generated by the engine decreases between 0.19% and 0.48% depending on λ. This decrease can be up to 2.6% when using E85 (Figure2a). These negligible changes in power result from the compensatory effect generated by the reduction in the air/fuel ratio (A/FE20 = 13.31 vs. A/FGasoline = 14.49) to the negative effect of the lower energy content of the ethanol (LHVE20 = 39,860 kJ/kg vs. LHVGasoline = 43,370 kJ/kg). The engine requires less air to burn the same mass of fuel and therefore it can increase the amount of fuel injected into the combustion chamber per engine cycle, which increases the power generated during each cycle. When the engine operates with E20, it uses a fuel with 8% less energy content than when it operates with gasoline, but it can use 8.1% more fuel. The net effect is a minor reduction in power (<0.2% for λ = 1). Experimental results obtained under steady-state conditions showed that in no operational mode of the tested engines did the power generated show statistically significant changes when E20 was used instead of gasoline. Figure2c shows that for the case of engine 1, the average power decreased in all operating modes between 0.1% and 3.2%. However, for engine 2 (operating at 2750 masl), the average power increased between 0.1% and 8.9% in 75% of the operating modes. These results agree with analytical results that predict smaller reductions in power than the variability of the power vs. RPM experimental results. Additionally, these results agree with those obtained by other authors. Ref. [9] used blends of gasoline and E30 and found that the full-load power of a four-cylinder engine is slightly diminished (up to 3%) as the ethanol content increases in the fuel. Ref. [14] analyzed a KIA 1.3 SOHC four-cylinder engine, operating with gasoline-E20 blends at full load and found that the power increased slightly with the ethanol content in the fuel. Ref. [11] studied a 200 cm3 mono-cylinder engine, fueled with gasoline and up to E100 and found no trend in the power generated by the engine. Experimental results with vehicles: The tests performed on the four vehicles on the chassis dynamometer every ~10,000 km of operation showed no statistically significant differences in power when they operated with E20 instead of E10. In this case, E10 was used instead of gasoline because E10 was the only commercially available fuel in the region where tests were carried out. We also observed Energies 2018, 11, 221 7 of 17 that the normal deterioration of the vehicles did not affect the power delivered by the engine when it operated with E10 or E20 (Figure2d). The torque delivered by an internal combustion engine is directly related to the power generated by the engine, through Equation (3). In fact, torque is the variable measured in the laboratory tests and power is the derived reported variable. Thus, the effect of the fuel change on this variable is similar to Energies 2018, 11, 221 7 of 17 the one described for power. In summary, analytical and experimental results obtained on engines and enginesin fuel-injected and in fuel-injected and carbureted and vehiclescarbureted showed vehicles a negligible showed a loss negligible of torque loss (<0.51%) of torque when (<0.51%) the enginewhen theoperates engine with operates E20 instead with E20 of gasoline.instead of gasoline.

64 39 E0 E10 63 E0 37 E10 62 E20 35 E20 61 E85 60 33 E85 th [%]th

59 η

Power [kW] Power 31 58 29 57 5000 RPM 56 27 0.8 0.9 1.0 1.1 0.8 0.9 1.0 1.1 λ λ (a) (b)

60 E20

50 Fuel injected vehicles E10 40

30 E10 [kW] 20 Carbureted E20 10 vehicles

Max powervehicleMax the at wheels 0 0 20406080100 103 km accumulated (c) (d)

Figure 2. Power generated by engines when they operate with ethanol-gasoline blends. (a) Estimated Figure 2. Power generated by engines when they operate with ethanol-gasoline blends. (a) Estimated power at 5000 RPM and (b) Estimated thermal efficiency displayed by engine 2 as a function of λ and power at 5000 RPM and (b) Estimated thermal efficiency displayed by engine 2 as a function of λ and ethanol content in the fuel; (c) Measured power delivered by engine 2 under steady-state conditions ethanol content in the fuel; (c) Measured power delivered by engine 2 under steady-state conditions and different modes of operation; (d) Measured maximum power delivered by carbureted vehicles and different modes of operation; (d) Measured maximum power delivered by carbureted vehicles and and fuel-injected vehicles after each ~10,000 km of operation. fuel-injected vehicles after each ~10,000 km of operation. 3.2. Fuel Consumption 3.2. Fuel Consumption In practice, users perceive fuel consumption as volumetric consumption instead of mass fuel In practice, users perceive fuel consumption as volumetric consumption instead of mass fuel consumption (. ), the latter being a more appropriate variable when referring to blends. However, consumption (m ), the latter being a more appropriate variable when referring to blends. However, given that the densityf of gasoline (~733 kg/m3) is similar to that of ethanol (~791 kg/m3), differences given that the density of gasoline (~733 kg/m3) is similar to that of ethanol (~791 kg/m3), differences in the fuel consumption perceived by users can be observed as differences in mass fuel consumption. in the fuel consumption perceived by users can be observed as differences in mass fuel consumption. The automotive community prefers to use specific fuel consumption (SFC), which is defined by The automotive community prefers to use specific fuel consumption (SFC), which is defined by Equation (1). As described above, when the ethanol content in gasoline increases, power decreases Equation (1). As described above, when the ethanol content in gasoline increases, power decreases negligibly. Therefore, variations in fuel consumption can be appreciated in the same way, using negligibly. Therefore, variations in fuel consumption can be appreciated in the same way, using volumetric consumption, mass consumption or SFC. volumetric consumption, mass consumption or SFC. Figure 3a shows estimated SFC as a function of λ and ethanol content in the fuel. As described above, increasing the ethanol content in gasoline, power decreases negligibly thanks to an increase in fuel consumption that can reach up to 46.7% in the case of E85. The above effect is observed in SFC as an increase of ~9.6% for E20 and of ~52% for E85. SFC is also a measurement of thermal efficiency when multiplied by the equivalent heating value of the fuel. Figure 2b shows that the reduction in the energy content of the fuel also generates small losses in the thermal efficiency of the engine (0.38–0.46% for E20 depending on λ). This loss in thermal efficiency increases with ethanol content, up to 2.3% for E85. Our analytical model predicts that this efficiency does not depend on engine RPM nor on engine load.

Energies 2018, 11, 221 8 of 17

Figure3a shows estimated SFC as a function of λ and ethanol content in the fuel. As described above, increasing the ethanol content in gasoline, power decreases negligibly thanks to an increase in fuel consumption that can reach up to 46.7% in the case of E85. The above effect is observed in SFC as an increase of ~9.6% for E20 and of ~52% for E85. SFC is also a measurement of thermal efficiency when multiplied by the equivalent heating value of the fuel. Figure2b shows that the reduction in the energy content of the fuel also generates small losses in the thermal efficiency of the engine (0.38–0.46% for E20 depending on λ). This loss in thermal efficiency increases with ethanol content, up to 2.3% for E85. Our analytical model predicts that this efficiencyEnergies does 2018, 11 not, 221 depend on engine RPM nor on engine load. 8 of 17 Figure3b shows that SFC increased between 2.3% and 23.6% when engine 2 was tested using E20 instead ofFigure gasoline. 3b shows that SFC increased between 2.3% and 23.6% when engine 2 was tested using E20Figure instead3c shows of gasoline. the SFC of the four vehicles operating under steady-state conditions at full load Figure 3c shows the SFC of the four vehicles operating under steady-state conditions at full load on the chassis dynamometer after 72,000 km of operation. This figure shows the typical behavior of on the chassis dynamometer after 72,000 km of operation. This figure shows the typical behavior of internalinternal combustion combustion engines, engines, which which exhibit exhibit higherhigher efficiencies efficiencies (lower (lower consumption) consumption) in intermediate in intermediate rangesranges (2500–3500) (2500–3500) of RPM.of RPM. It It also also shows shows thatthat fuel-injectedfuel-injected vehicles vehicles are are substantially substantially more more efficient efficient thanthan carbureted carbureted vehicles. vehicles. Finally, Finally, it it shows shows thatthat inin the case case of of fuel-injected fuel-injected vehicles, vehicles, fuel fuelconsumption consumption increasedincreased with with ethanol ethanol content content except except at at high high RPMRPM (>5000). (>5000). In In the the case case of carbureted of carbureted vehicles, vehicles, there there was nowas clear no clear trend. trend.

450

400 E85 350

300

250 SFC [g/kWh]

200 E0 E10 E20 150 0.80.91.01.1 λ (a)

530 E20 490 Carbureted E10 vehicles 450 410 370

SFC [g/kWh] 330 E20 Fuel injected vehicles 290 E10 250 1000 2000 3000 4000 5000 6000 RPM (b) (c)

Figure 3. Results of specific fuel consumption (SFC) obtained: (a) analytically; (b) testing engine 2 Figure 3. Results of specific fuel consumption (SFC) obtained: (a) analytically; (b) testing engine 2 under under steady-state conditions; and (c) carbureted and fuel-injected vehicles under steady-state steady-stateconditions conditions; at full load and on the (c) chassis carbureted dynamometer and fuel-injected after 72,000 vehicles km of operation under steady-state. conditions at full load on the chassis dynamometer after 72,000 km of operation. 3.3. Effect of Fuel Change on λ 3.3. Effect of Fuel Change on λ Fuel-injected vehicles usually use a lambda sensor to close the control loop of engine operation. ItFuel-injected measures the vehicles content usually of use the acombustion lambda sensor products to close and the the engine control computer loop of engineunit converts operation. It measuresthat measurement the oxygen into content a λ value of using the combustion a default fuelproducts composition. and We the evaluated engine computerthe effects of unit the fuel converts change on the real values of λ under which the vehicles operate. To do so, we used several that measurement into a λ value using a default fuel composition. We evaluated the effects of the experimental data points of known byproducts composition and used our analytical model based on fuel change on the real values of λ under which the vehicles operate. To do so, we used several equilibrium analysis, in the reverse direction, and calculated λ, assuming that the fuel was gasoline experimentaland repeated data the points calculation of known assuming byproducts that the compositionfuel was E20. We and found used differences our analytical smaller model than based 1% on in all cases. We also compared those calculated values of λ with the ones reported by the engine computer and a third lambda sensor (Table 4). Again, we obtained negligible differences. These results indicate that lambda sensors for gasoline-fueled vehicles are unaffected when they operate with E20 instead of gasoline. We then used the external lambda sensor described in Table 4 to compare the λ operational conditions of the vehicles when they are fueled with E20 and E10 under different steady-state conditions and we found no significant differences. However, we did find consistent differences

Energies 2018, 11, 221 9 of 17 equilibrium analysis, in the reverse direction, and calculated λ, assuming that the fuel was gasoline and repeated the calculation assuming that the fuel was E20. We found differences smaller than 1% in all cases. We also compared those calculated values of λ with the ones reported by the engine computer and a third lambda sensor (Table4). Again, we obtained negligible differences. These results indicate that lambda sensors for gasoline-fueled vehicles are unaffected when they operate with E20 instead of gasoline. We then used the external lambda sensor described in Table4 to compare the λ operational conditions of the vehicles when they are fueled with E20 and E10 under different steady-state conditions Energies 2018, 11, 221 9 of 17 and we found no significant differences. However, we did find consistent differences when the vehicles whenoperated the atvehicles full load. operated Figure at4 fullshows load. that Figure at full 4 shows load, carbureted that at full andload, fuel-injected carbureted and engines fuel-injected operate withengines 0.9 operate < λ < 0.95. with It 0.9 also < λ shows < 0.95. that,It also at shows full load, that, engines at full load, tend engines to operate tend with to operate greater with values greater of λ whenvalues they of λ are when fueled they with are E20 fueled instead with of E10.E20 instead This is due of E10. to the This fact is that due at fullto the load fact (maximum that at full power), load (maximumengines demand power), maximum engines fuel demand rates. maximum However, whenfuel rates. the engines However, operate when with the E20 engines instead operate of E10 with they E20require instead additional of E10 fuel,they asrequire described additional above, fuel, but injectors,as described or the above, calibrated but injectors, orifices ofor thethe carburetor,calibrated orificesare rated of for the the carburetor, base case are of gasolinerated for and the thereforebase case they of gasoline are unable and to therefore supply thethey new are demanded unable to supplyfuel rate. the Consequently, new demanded the fuel engine rate. worksConsequently, with less th fuele engine than works demanded, with less i.e., fuel the than engine demanded, operates withi.e., the greater engineλ thanoperates demanded. with greater The differences λ than demanded. disappear The for differences lower engine disappear loads. This for fortunatelower engine fact loads.favors This the environmental fortunate fact performancefavors the environmental of the vehicles, performance especially inof thethe workingvehicles, modesespecially where in the workingengine is modes programed where to the work engine with isλ programed< 1, that correspond to work with to the λ conditions<1, that correspond under which to the the conditions emission underof pollutants which arethe theemission greatest, of pollutants as it will be are shown the greatest, in the next as it sections. will be shown in the next sections.

0.95 Carbureted 0.95 Fuel injected vehicles vehicles 0.90 0.90 E20 E20

λ 0.85 0.85 λ E10 0.80 E10 0.80

0.75 0.75 1500 2500 3500 4500 5500 1500 2500 3500 4500 5500

RPM RPM (a) (b)

Figure 4. Effect of fuel changes in the operational conditions under which the vehicles work. λ vs. Figure 4. Effect of fuel changes in the operational conditions under which the vehicles work. λ vs. RPM obtained from (a) carbureted and (b) fuel-injected vehicles at full load. RPM obtained from (a) carbureted and (b) fuel-injected vehicles at full load. Combustion of gasoline-ethanol blends requires a smaller amount of air than in pure gasoline combustion.Combustion For a of given gasoline-ethanol engine RPM blends and throttle requires valve a smaller opening, amount the of airflow air than rate in pureentering gasoline the cylinderscombustion. remains For a the given same. engine To keep RPM the and air-fuel throttle eq valveuivalent opening, ratio theconstant, airflow the rate ECU entering (electronic the cylinders control unit)remains increases the same. the ethanol-gasoline To keep the air-fuel blend equivalent rate. However, ratio constant, in some thefuel-rich ECU (electronicconditions, control the leaning unit) effectincreases produced the ethanol-gasoline by the oxygen blendcontent rate. of ethanol However, leads in someback to fuel-rich stoichiometric conditions, operating the leaning conditions, effect producedamending by the the combustion oxygen content efficiency. of ethanol leads back to stoichiometric operating conditions, amending the combustion efficiency.

3.4. CO2 Emission Index 3.4. CO2 Emission Index Figure 5a shows that the estimated emission index for CO2 (EICO2) increases negligibly with Figure5a shows that the estimated emission index for CO 2 (EICO ) increases negligibly with ethanol content for λ > 1. EICO2 increases between 0.22% and 1.65% depending2 on λ when the engine ethanol content for λ > 1. EI increases between 0.22% and 1.65% depending on λ when the engine operates with E20 instead of COgasoline2 . This increase can reach up to 9% in the case of E85. Analytically, operates with E20 instead of gasoline. This increase can reach up to 9% in the case of E85. Analytically, EICO2 is independent of RPM or engine load. EICO is independent of RPM or engine load. 2We found that in 93% of the engine operating modes, EICO2 showed a statistically significant We found that in 93% of the engine operating modes, EI showed a statistically significant increase when the engine operated with E20 instead of gasoline.CO 2This increase varied between 6.4% increase when the engine operated with E20 instead of gasoline. This increase varied between 6.4% and 21.1% as shown in Figure 5b. This could be due to the fact that ethanol-gasoline blend ensures and 21.1% as shown in Figure5b. This could be due to the fact that ethanol-gasoline blend ensures more efficient and complete combustion of such blends inside the cylinder, thereby increasing the total quantity of CO2 exhaust emissions. The increase in EICO2 was not statistically significant when carbureted and fuel-injected vehicles were evaluated following the NEDC on a chassis dynamometer, after every 10,000 km traveled. The normal deterioration of the vehicle did not affect EICO2 when they operated with E20 or E10 (Figure 5c).

Energies 2018, 11, 221 10 of 17 more efficient and complete combustion of such blends inside the cylinder, thereby increasing the total quantity of CO2 exhaust emissions.

The increase in EICO2 was not statistically significant when carbureted and fuel-injected vehicles were evaluated following the NEDC on a chassis dynamometer, after every 10,000 km traveled.

The normal deterioration of the vehicle did not affect EICO2 when they operated with E20 or E10 (FigureEnergies5c). 2018, 11, 221 10 of 17

690

670 E85 650 630 [g/kWh]

2 610 E20 590 E10 E0 EI CO EI 570 550 0.8 0.9 1.0 1.1 λ (a) (b)

(c) (d)

Figure 5. CO2 emission indexes obtained through: (a) Analytical model; (b) Engine tests under steady- Figurestate 5. COconditions;2 emission (c) Carbureted indexes obtained and (d) through:Fuel-injected (a) Analyticalvehicles, followi model;ng (theb) Enginenew european tests under driving steady- statecycle conditions; (NEDC) (onc) Carburetedchassis dynamomete and (drs,) Fuel-injected after every 10,000 vehicles, km traveled following. the new european driving cycle (NEDC) on chassis dynamometers, after every 10,000 km traveled. 3.5. CO Emission Index 3.5. CO Emission Index Figure 6a shows that EICO is negligible for λ > 1 and grows proportionally with (1 − λ). For rich

air-fuelFigure6 mixturesa shows ( thatλ < 1),EI theCO estimatedis negligible EICO forshowsλ > a 1 small and growsreduction proportionally with the ethanol with content (1 − λ in). theFor rich fuel that could be up to ~17.5% for E20. air-fuel mixtures (λ < 1), the estimated EICO shows a small reduction with the ethanol content in the fuel that couldExperimental be up totests ~17.5% on engines, for E20. operating under steady state conditions, showed that the average values of EICO tended to decrease in most of the operational modes (~80% of the cases) of the engine Experimental tests on engines, operating under steady state conditions, showed that the average when they used E20 instead of gasoline (Figure 6b). However, those changes were not statistically valuessignificant. of EICO tendedThis result to decreaseagrees with in our most analytical of the operationalresults and those modes obtained (~80% by of other the authors cases) of [14–16]. the engine whenFigure they 6c,d used show E20 that instead EICO is of about gasoline two orders (Figure of6 b).magnitude However, higher those for carbureted changes were vehicles not than statistically for significant.fuel-injected This resultvehicles, agrees when with they our reprod analyticaluce the results NEDC and on thosea chassis obtained dynamometer. by other authorsThis result [14 –16]. Figuredemonstrates6c,d show thatthe capacityEICO is of about fuel injection two orders technolo of magnitudegy to control higher air/fuel for ratio carbureted under very vehicles diverse than for fuel-injectedconditions of vehicles,operation in when contra theyst to reproducethe carbureted the technology. NEDC on a chassis dynamometer. This result demonstratesWe also the found capacity that ofin fuel88% injectionof the evaluated technology cases, to carbureted control air/fuel vehicles ratioshowed under a significant very diverse conditionsreduction of operationin CO emissions in contrast (~70%), to when the carbureted they used E20 technology. instead of E10, which was an expected result given the high levels of CO emissions of carbureted vehicles and the expected effects of oxygenating We also found that in 88% of the evaluated cases, carbureted vehicles showed a significant the fuel with ethanol. However, in the case of fuel-injected vehicles, no statistically significant reduction in CO emissions (~70%), when they used E20 instead of E10, which was an expected result differences were observed due to fuel changes. The same results were observed during the tests givencarried the high out levels every of~10,000 CO emissions km. of carbureted vehicles and the expected effects of oxygenating the fuel with ethanol. However, in the case of fuel-injected vehicles, no statistically significant differences were observed due to fuel changes. The same results were observed during the tests carried out every ~10,000 km.

Energies 2018, 11, 221 11 of 17

Energies 2018, 11, 221 11 of 17

90 80 E0 70 E10 60 50 E20 40 30 E85

EI CO [g/kWh] 20 10 0 0.80.91.01.1

λ (a) (b)

(c) (d)

Figure 6. CO emission indexes obtained by: (a) Our analytical model for engines; (b) Engine tests Figureunder 6. CO steady-state emission condition; indexes ( obtainedc) Carbureted by: and (a) Our(d) Fuel-injected analytical modelvehicles for following engines; the (b NEDC) Engine on tests underchassis steady-state dynamometers, condition; after (everyc) Carbureted 10,000 km andtraveled (d). Fuel-injected vehicles following the NEDC on chassis dynamometers, after every 10,000 km traveled. 3.6. NOx Emission Index 3.6. NOxIncreasing Emission Indexthe percentage of ethanol increases the latent heat of vaporization of the blends and thereforeIncreasing the the temperature percentage of of the ethanol air-fuel increases mixture thedecreases latent heatat the of end vaporization of the intake of thestroke blends in and comparison with gasoline. It also reduces the energy content of the fuel blend, which reduces the therefore the temperature of the air-fuel mixture decreases at the end of the intake stroke in comparison combustion temperature, reducing the thermal NOx production. with gasoline.Our model It also for reducesthe estimation the energy of emissions content in en ofgines the fuelpredicts blend, a small which (<2.50%) reduces reduction the combustion in the temperature,NOx emission reducing index the (EINOx thermal) when NOxthe engine production. operates with E20 instead of gasoline. Figure 7a shows thatOur this model reduction for the can estimation be up to 14.1% of emissionswhen the en ingine engines operates predicts with E85. a smallThe formation (<2.50%) of reductionNOx in in the NOxinternal emission combustion index engines (EINOx depends) when thestrongly engine on operatesthe maximum with temperature E20 instead achieved of gasoline. inside Figure the 7a showscombustion that this chamber. reduction Therefore, can be up reduction to 14.1% in NOx when emissions the engine is due operates to ethanol’s with lower E85. heating The formation value, of NOxwhich in internal generates combustion lower temperatures engines depends inside the strongly combustion on the chamber maximum as ethanol temperature content achievedin the fuel inside the combustionincreases. chamber. Therefore, reduction in NOx emissions is due to ethanol’s lower heating value, whichHowever, generates engine lower tests temperaturesshowed that NOx inside emissi the combustionons did not chamberexhibit statistically as ethanol significant content in the changes when E20 was used instead of gasoline in any mode of operation. Figure 7b shows reductions fuel increases. in the average values of EINOx in the 86.7% of the modes of the engine operation. Those reductions variedHowever, between engine 3.0% tests and showed 17.5%. A that similar NOx result emissions was found did not for exhibitthe case statistically of the carbureted significant and fuel changes wheninjected E20 was vehicles used in instead their test of ever gasoliney ~20,000 in any km of mode operation. of operation. These experimental Figure7b showsresults are reductions consistent in the averagewith values the results of EI ofNOx thein analytical the 86.7% model, of the which modes pr ofedicts the engineNOx reductions operation. that Those are lower reductions than the varied betweenvariability 3.0% andof the 17.5%. experimental A similar results. result Additionally, was found forthey the agree case with of the results carbureted reported and by fuelseveral injected vehiclesauthors in their who testtested every engines ~20,000 varying km the of operation.ethanol content These in experimentalthe fuel [4,17,18]. results are consistent with the results of the analytical model, which predicts NOx reductions that are lower than the variability of the experimental results. Additionally, they agree with results reported by several authors who tested engines varying the ethanol content in the fuel [4,17,18].

Energies 2018, 11, 221 12 of 17 Energies 2018, 11, 221 12 of 17

50 E0 45 E10 Energies40 2018, 11, 221 12 of 17 35 E20 30 50 25 E0 20 45 E10 15 40 E85 E20 10 35 EI NOx [g/kWh] NOx EI 5 30 25 0 20 0.8 0.9 1.0 1.1 15 E85 10

EI NOx [g/kWh] NOx EI λ 5 0 (a) (b) 0.8 0.9 1.0 1.1 Figure 7. NOx emission indexes obtained by (a) Our analytical model for engines; and (b) Tests on Figure 7. NOx emission indexes obtained by (a) Our analytical model for engines; and (b) Tests on engine 1 under steady-stateλ conditions, when the engine used different ethanol-gasoline blends. engine 1 under steady-state(a) conditions, when the engine used different ethanol-gasoline(b) blends.

3.7. HC FigureEmission 7. NOx Index emission indexes obtained by (a) Our analytical model for engines; and (b) Tests on 3.7. HC Emission Index engine 1 under steady-state conditions, when the engine used different ethanol-gasoline blends. Figure 8a shows the unburned emission index (EIHC) estimated by thermal equilibriumFigure8a analysis shows at the the unburned tailpipe conditions hydrocarbons (T = 120 emission °C, P = 101 index kPa). (ResultsEIHC) are estimated similar to by the thermal ones 3.7. HC Emission Index ◦ equilibriumobtained for analysis CO. Like at CO, the EI tailpipeHC becomes conditions negligible (T for= 120 poorC, air-fuelP = 101 mixtures kPa). Results(λ > 1). However, are similar under to the Figure 8a shows the unburned hydrocarbons emission index (EIHC) estimated by thermal onesthis obtained operating for condition, CO. Like Figure CO, EI 8aHC showsbecomes that negligibleEIHC increases for negligibly poor air-fuel (~0.2%) mixtures with ethanol (λ > 1). content However, equilibrium analysis at the tailpipe conditions (T = 120 °C, P = 101 kPa). Results are similar to the ones underin the this fuel. operating For rich condition, air-fuel mixtures Figure8a ( showsλ < 1), thatEIHC EIincreasesHC increases proportionally negligibly with (~0.2%) λ reductions. with ethanol obtained for CO. Like CO, EIHC becomes negligible for poor air-fuel mixtures (λ > 1). However, under contentHowever, in the contrary fuel. For to richCO emissions, air-fuel mixtures the addition (λ < 1),of ethanolEIHC increases in gasoline proportionally contributes to with an increaseλ reductions. of this operating condition, Figure 8a shows that EIHC increases negligibly (~0.2%) with ethanol content However,EIHC of up contrary to 3.01% to for CO E20 emissions, at λ = 0.85. the This addition increase of can ethanol reach in up gasoline to 14.6% contributes when operating to an with increase E85 of in the fuel. For rich air-fuel mixtures (λ < 1), EIHC increases proportionally with λ reductions. EIfor ofthis up same to 3.01% condition for E20 of extreme at λ = 0.85. operation. This increase Usually can spark-ignition reach up to engines 14.6%when operate operating with λ close with to E85 HC However, contrary to CO emissions, the addition of ethanol in gasoline contributes to an increase of for1. this Results same shown condition in Figure of extreme 8a are independent operation. Usually of RPM spark-ignition and of the percentage engines of operate engine with load.λ close to 1. EIHC of up to 3.01% for E20 at λ = 0.85. This increase can reach up to 14.6% when operating with E85 Experimental work was limited to the measurement of the unburned hydrocarbons in vehicles Resultsfor shownthis same in condition Figure8a of are extreme independent operation. of RPMUsually and spark-ignition of the percentage engines of operate engine with load. λ close to followingExperimental1. Results the shown NEDC work in on Figure wasa chassis limited8a are dynamometer. independent to the measurement of We RPM found and of thatof thethe carbureted unburnedpercentage and of hydrocarbons enginefuel-injected load. invehicles vehicles followingdid notExperimental theshow NEDC any onstatistically work a chassis was limited significant dynamometer. to the differmeasuremen Weence found int ofunburned that the unburned carbureted hydrocarbon hydrocarbons and fuel-injected emissions in vehicles when vehicles didvehicles notfollowing show were any the fueled statisticallyNEDC with on a E20chassis significant compared dynamometer. difference to when We in they found unburned were that fueledcarbureted hydrocarbon with and E10 emissionsfuel-injected (Figure 8b,c). when vehicles These vehicles experimental results are consistent with results obtained from the analytical model and with results weredid fueled not withshow E20 any compared statistically to whensignificant they differ wereence fueled in withunburned E10 (Figurehydrocarbon8b,c). Theseemissions experimental when reported by other authors [19,20]. resultsvehicles are consistent were fueled with with results E20 compared obtained to from when the they analytical were fueled model with and E10 with (Figure results 8b,c). reported These by experimental results are consistent with results obtained from the analytical model and with results other authors [19,20]. 16 reported by other authors [19,20]. E85 14 16 12 E85 1014 E0 812 10 E10 6 E0 8

EI HC [g/kWh] EI 4 E20 6 E10 2

EI HC [g/kWh] EI 4 E20 0 0.82 0.9 1.0 1.1 0 0.8 0.9λ 1.0 1.1 (a) λ (a)

Figure 8. Cont.

Energies 2018, 11, 221 13 of 17 Energies 2018, 11, 221 13 of 17

(b) (c)

Figure 8. HC emission indexes obtained from (a) Our analytical model for engines; (b) Carbureted Figure 8. a b and (HCc) Fuel-injected emission indexes vehicles obtained following from the (NEDC) Our on analytical a chassis model dynamometer for engines; every ( 10,000) Carbureted km of and (c) Fuel-injectedoperation. vehicles following the NEDC on a chassis dynamometer every 10,000 km of operation.

3.8. Effect3.8. Effect on the on Othe3 FormationO3 Formation Potential Potential As describedAs described in thein the introduction introduction section, section, the po potentialtential increase increase in inthe the emission emission of unburned of unburned hydrocarbonshydrocarbons of vehicles of vehicles when when they they are are fueled fueled withwith ethanol-gasoline blends blends instead instead of gasoline of gasoline is an is an issue of great interest because unburned hydrocarbons, specifically the volatile organic compounds issue of great interest because unburned hydrocarbons, specifically the volatile organic compounds (VOC), are precursors of (O3). (VOC), are precursors of tropospheric ozone (O ). Figure 9a shows the equilibrium composition3 of most relevant VOCs at the tailpipe temperature Figure(~100 °C).9a showsIt shows the that equilibrium the emissions composition of ethane, formaldehyde, of most relevant ethylene VOCs and atthe ethanol tailpipe are the temperature most ◦ (~100relevantC). It showsVOCs in that terms the of emissions the amount of of ethane, mass emitted. formaldehyde, For poor air-fuel ethylene mixtures and ethanol (λ > 1) all are VOCs the most relevantdisappear VOCs and in termsfor λ < of 1 thethose amount emissions of massare negligible emitted. (EI For < 10 poor−6 g/kWh). air-fuel However, mixtures it is (λ relevant> 1) all to VOCs disappearunderstand and for theλ tendency< 1 those in emissionsthe emission are of negligible VOCs to predict (EI < 10the− potential6 g/kWh). cumulative However, impact it is relevantof the to understandmillions theof vehicles tendency running in the in emission large urban of centers. VOCs to predict the potential cumulative impact of the millions ofFigure vehicles 9b shows running the relative in large differences urban centers. in those emissions when the engine operates with E20. FigureIt shows9b that shows these the emissions relative reduce differences by between in those 20% emissionsand 40%. Toluene, when thebenzene engine and operates 1,3-butadiene with E20. are the VOCs that experience the largest reductions in mass emissions. These equilibrium-based It shows that these emissions reduce by between 20% and 40%. Toluene, benzene and 1,3-butadiene results do not explain the observed increases in some VOCs, particularly acetaldehydes, ethanol and are theformaldehydes VOCs that [19]. experience Additional the research largest work reductions is needed in to mass find out emissions. if these differences These equilibrium-based are due to the resultsportential do not explainroll of chemical the observed kinetics increases in the VOCs’ in some concentrations VOCs, particularly or the particular acetaldehydes, conditions ethanol under and formaldehydeswhich the experimental [19]. Additional measurements research were work conducted. is needed to find out if these differences are due to the portentialEvery roll VOC of has chemical a different kinetics contribution in the VOCs’to the tota concentrationsl ozone formation or thepotential particular (OFP) conditionsof the engine under whichemissions. the experimental The maximum measurements incremental were reactivity conducted. (MIR) index developed by Carter [21] is one of the Everywell accepted VOC has alternatives a different to grade contribution their contribution. to the total This ozone reactivity formation scale is potential based on (OFP) calculations of the of engine emissions.relative The O3 impacts, maximum expressed incremental as the mass reactivity of the (MIR)maximum index additional developed O3 formed by Carter per mass [21] isof oneVOC of the well acceptedadded to the alternatives emissions (g to O grade3/g VOC) their for contribution. various compounds, This reactivity under conditions scale is in based which on the calculations ambient of O3 concentration is most sensitive to changes in VOC emissions [22]. Equation 6 calculates the total relative O3 impacts, expressed as the mass of the maximum additional O3 formed per mass of VOC OFP in g O3/kW h of the VOCs emitted by the engine, where MIRi is the MIR (in g O3/g VOCi) and EIi added to the emissions (g O /g VOC) for various compounds, under conditions in which the ambient is the emission index (in g3 VOCi/kWh) for compound i. O3 concentration is most sensitive to changes in VOC emissions [22]. Equation 6 calculates the total OFP = OFP in g O3/kW h of the VOCs emitted by the engine, where MIRi is the MIR (in g O3/g VOC(6) i) and EI is the emission index (in g VOC /kWh) for compound i. i Figure 9c shows the relative idifferences in OFP of the engine emissions when they operate with E20 instead of gasoline. It shows that for all engine operating conditions, the use of ethanol-gasoline blends tend to reduce the OFP of the engiOFPne emissions= ∑ MIR wheniEI ithe engine works with λ < 1, regardless (6) of the temperature being considered. Figure9c shows the relative differences in OFP of the engine emissions when they operate with E20 instead of gasoline. It shows that for all engine operating conditions, the use of ethanol-gasoline blends tend to reduce the OFP of the engine emissions when the engine works with λ < 1, regardless of the temperature being considered.

Energies 2018, 11, 221 14 of 17

Energies 2018, 11, 221 14 of 17

0 1.E+0010-00 Methane -5 1.E-0410-04

-10 1.E-0810-08 Ethane

-12 Formaldehyde 1.E-1210 -15 Methane Ethanol Formaldehyde -16 Acetaldehyde 1.E-1610 Ethylene -20 Ethane Ethanol Ethylene Acetone -20 (%) 1.E-2010 Acetaldehyde Acetylene -25 Propylene

EI (g/kWh) EI Propylene 1.E-2410-24 -30 1,3 Butadiene 1.E-2810-28 Acetylene -35 1.E-3210-32 Benzene Benzene 1.E-3610-36 Toluene -40 Toluene

1,3 Butadiene gasoline of instead E20 using EI by in differences Relative 1.E-4010-40 Acetone -45 0.85 0.90 0.95 1.00 1.05 0.75 0.80 0.85 0.90 0.95 1.00 1.05 λ λ

(a) (b) 5 100 °C 0

-5

(%) -10 727 °C

-15

Relative differences in OFP OFP in differences Relative -20 0.85 0.90 0.95 1.00 1.05 1.10 λ (c)

Figure 9. (a) Estimated emission indexes for the most relevant volatile organic compounds (VOCs) Figure 9.for(a )gasoline Estimated and emissionE20 fueled indexesvehicles. Relative for the mostdifferences relevant of using volatile E20 instead organic of gasoline compounds in (b) (VOCs) for gasoline andemission E20 indexes fueled and vehicles. (c) ozone Relative formation differencespotential. of using E20 instead of gasoline in (b) emission indexes and (c) ozone formation potential. 3.9. Overall Environmental Impact of Using Ethanol-Gasoline Blends in Vehicles

3.9. Overall EnvironmentalSo far, we have Impact described of Using the effects Ethanol-Gasoline of using ethanol-gasoline Blends in Vehicles blends on the vehicle performance. Complementarily, it is of interest to estimate the net effect of the fuel change on the So far,environment we have through described a life the cycle effects analysis. of To using do so ethanol-gasoline, we used the Eco-indicator-99 blends on methodology the vehicle [23]. performance. This indicator considers three areas of impact of a given process (Table 6): Complementarily, it is of interest to estimate the net effect of the fuel change on the environment • through a lifeDamage cycle to analysis. human health To, dowhich so, is we given used in terms theEco-indicator-99 of inactivity days per methodology year caused by each [23]. kg This of indicator pollutant emitted during the process. It considers carcinogenic and respiratory effects, health considers threeeffects areas caused of impactby ionizing of aradiat givenion, processhealth effects (Table caused6): by ozone layer depletion and damage to human health caused by climate change. • Damage to human health • Damage to ecosystem, which quality, is which given is inexpressed terms of as inactivity the percentage days of per species year that caused have by each kg of pollutantdisappeared emitted per during unit area the due process. to the environmen It considerstal loads carcinogenic imposed by andthe process. respiratory It includes effects, health effects causedtoxicity, by acidification, ionizing eutrophication, radiation, health land-use effects and land caused transformation. by ozone layer depletion and damage to human health caused by climate change. • Damage to ecosystem quality, which is expressed as the percentage of species that have disappeared per unit area due to the environmental loads imposed by the process. It includes toxicity, acidification, eutrophication, land-use and land transformation. • Damage to resources caused by extraction of minerals and fossil fuels expressed in terms of the energy needed per unit of mineral or fuel extracted.

Medical and ecological studies have quantified and reported each of these damages for different processes. To quantify the net effect on the environment of fueling vehicles with ethanol-gasoline Energies 2018, 11, 221 15 of 17 blends instead of gasoline, we applied the Eco-indicator-99 methodology to both cases considering the following processes: (i) The production of gasoline and E20 and (ii) The use of those fuels in vehicles. Following this procedure, we obtained relative reductions of 1.3%, 1.4% and 12.9% in damages to human health, the ecosystem and natural resources, respectively, when using E20 instead of gasoline in vehicles. These results were expected, as emission indexes and fuel consumption were similar with E20 and gasoline. Therefore, the main contribution to the global environment of using E20 in vehicles is the reduction in the depletion of natural resources.

Table 6. Overall environmental impact of using ethanol-gasoline blends in vehicles according to the Eco-indicator-99 methodology.

Categories Subcategories Gasoline E20 Reductions Carcinogenic effects 4.13 × 10−21 4.16 × 10−21 −1% Respiratory effects due to organic emissions 4.78 × 10−12 5.38 × 10−12 −12% Damage to human health Respiratory effects due to inorganic emissions 6.49 × 10−2 6.39 × 10−2 1% Damage to human health caused by climate change 3.50 × 10−3 3.52 × 10−3 −1% Toxic emissions 2.82 × 10−46 2.72 × 10−46 4% Damage to ecosystem quality Acidification and eutrophication 1.25 × 10−2 1.24 × 10−2 1% Extraction of minerals and fossil fuels 1.03 × 10−1 8.99 × 10−2 12% Damage to resources Fuel processing 3.57 × 10−2 3.06 × 10−2 14%

4. Conclusions We performed analytical and experimental work on engines and vehicles to evaluate the effect of using ethanol-gasoline blends instead of gasoline on the mechanical, energy and environmental performance of carbureted and fuel-injected, in-use vehicles, without any adjustment in the setup of the engine computer unit. We used a zero-dimensional, steady-state model, based on thermal equilibrium analysis, to estimate power, torque, fuel consumption and emissions of internal combustion engines when they are fueled with different ethanol-gasoline blends. This model predicted minor reductions (<2%) in the maximum delivered power and torque, and in the CO and NOx emissions when they are fueled with E20 instead of gasoline. Although ethanol has a lower energy content than gasoline, power remained essentially unchanged thanks to a minor increase (<2%) in fuel consumption. Reductions in NOx emissions are due to reductions in the maximum temperature reached inside the combustion chamber caused by the lower energy content and the higher latent heat of vaporization of ethanol compared to that of gasoline. CO2 and unburned hydrocarbon (HC) emissions increased with ethanol content in the fuel. A minor increase (<2%) was estimated in these two pollutant emissions when using E20. These estimated reductions are less than the variations of the measurements obtained in engine test benches and vehicles on chassis dynamometers. Experimental tests showed statistically insignificant differences in power, torque, fuel consumption and emission of pollutants in engines and vehicles. The same conclusions were obtained during the tests conducted every 10,000 km of vehicle operation, indicating that the addition of ethanol to the fuel does not significantly affect mechanical, energy or environmental performance, at least for the first 100,000 km of operation. We learned from measuring λ at different conditions of vehicle operation that when they operate at full load, which corresponds to the conditions of maximum emission of pollutants (0.9 < λ < 0.95) and maximum fuel consumption, the addition of ethanol to the fuel forces the engines to operate with greater λ than when they operate with gasoline, reducing the net emission of pollutants. This effect disappears at partial engine loads. Thermal equilibrium analysis of the tailpipe conditions (~100 ◦C) showed that the estimated emissions of VOCs were negligible (EI < 10−6 g/kWh) and that ethane, formaldehyde, ethylene and ethanol are the most relevant VOCs in terms of the amount of mass emitted. The use of ethanol in the gasoline reduced those emissions by between 20–40%, with toluene, benzene and 1,3-butadiene being the VOCs that experienced the largest reductions in mass emissions. These reductions imply Energies 2018, 11, 221 16 of 17 an average reduction of 17% for λ < 1 in the ozone formation potential, calculated following the methodology of the maximum indexes of reactivity (MIR). Complementarily, we estimated the effect of the fuel change on the environment through a life cycle analysis based on the Eco-indicator-99 methodology. We obtained relative reductions of 1.3%, 1.4% and 12.9% in damages to human health, the ecosystem and natural resources, respectively, when vehicles are fueled with E20 instead of gasoline.

Acknowledgments: This work was partially financed by ECOPETROL, Ministry of Mines and Energy of Colombia, COLCIENCIAS (the Colombian Administrative Department of Science, Technology and Innovation) and CONACYT (The Mexican Council for Science and Technology). Author Contributions: Juan E. Tibaquirá leaded of the experimental work. José I. Huertas leaded data analysis, analytical analysis and wrote the last version of the manuscript. Sebastián Ospina and Luis F. Quirama conducted experimental work under the direction of Juan E. Tibaquirá. José E. Niño conducted data analysis, analytical analysis an wrote the first draft of the paper under the direction of José I. Huertas. Conflicts of Interest: The authors declare no conflict of interest.

Symbols and Acronyms x Mass fraction - τ Torque N m . m f Fuel mass flow g/h ηth Engine thermal efficiency % ηm Engine mechanical efficiency % r Engine compression ratio - λ Relative air/fuel ratio - Ed Engine displacement L EI Emission Index g/kWh P Power kW Nc Engine cylinders number - A/F Air-fuel ratio - CO - CO2 Carbon dioxide - E20 Gasoline with 20% v/v content of ethanol - LHV Fuel low heating value kJ/kg masl Meters above the sea level m HC Unburned hydrocarbons - MIR Maximum index of reactivity g O3/gVOC NEDC New European driving cycle - NOx - OFP Ozone formation potential - RPM Engine rotating speed Rev/min RVP The Reid Vapor Pressure SFC Specific Fuel Consumption g/kWh HC Total unburned hydrocarbons - VOC Volatile organic compounds -

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