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Fuel Economy and CO2 Emissions of Ethanol-Gasoline Blends in a Turbocharged DI Fuel Economy and CO2 Emissions of Ethanol-Gasoline Blends in a Turbocharged DI Engine
Abstract
Engine dynamometer testing was performed comparing E10, E20, and E30 splash-blended fuels in a Ford 3.5L EcoBoost direct injection (DI) turbocharged engine. The engine was tested with compression ratios (CRs) of 10.0:1 (current production) and 11.9:1. In this engine, E20 (96 RON) fuel at 11.9:1 CR gave very similar knock performance to E10 (91 RON) fuel at 10:1 CR. Similarly, E30 (101 RON) fuel at 11.9:1 CR resulted in knock-limited performance equivalent to E20 at 10:1 CR, indicating that E30 could have been run at even higher CR with acceptable knock behavior.
The data was used in a vehicle simulation of a 3.5L EcoBoost pickup truck, which showed that the E20 (96 RON) fuel at 11.9:1 CR offers 5% improvement in U.S. EPA Metro-Highway (M/H) and US06 Highway cycle tank-to-wheels CO₂ emissions over the E10 fuel, with comparable volumetric fuel economy (miles per gallon) and range before refueling. The results also indicated that the E30 (101 RON) fuel at 11.9:1 CR provides improvements in CO₂ emissions of 5% on the EPA M/H cycle and 7.5% on the US06 Highway cycle, while volumetric fuel economy was 3% lower on the M/H cycle and approximately equal on the US06 Highway cycle, compared to the baseline E10 fuel at 10:1 CR.
... Several studies have identified possible ethanol-gasoline fuel formulations that could lend themselves to enabling increased engine compression ratio, reduced tailpipe CO 2 , and minimally reduced tank fuel mileage by not over-diluting the energy content of the fuel with ethanol (Jung et al., 2013a;Splitter and Szybist, 2014a,b). These recent studies show that blends of ethanol between 20 and 40% could increase octane more than E10 or E15 blends, while not diluting fuel energy as mush as typical flex fuel (e.g., "E85") blends that can range from 51 to 83% ethanol (ASTM Standard D 5798, 2014). ...
... Beyond flame speed and dilution tolerance effects, intermediate ethanol-gasoline blends have been shown to exhibit reduced combustion temperatures and increasing engine efficiency (Szybist et al., 2010;Jung et al., 2013b), which Szybist et al. illustrate could be a product of increased molar expansion ratio of alcohols compared to gasoline (Szybist et al., 2012). Many have indicated that the charge cooling of ethanol in direct injection engines offers reduced enrichment need (Stein et al., 2012(Stein et al., , 2013Jung et al., 2013a). An interesting recent study of Sluder et al. (2016) suggests that, in practice, fuel sensitivity -the fuel RON minus the fuel MON octane numbers -by default accounts for much of the charge cooling effects from direct fuel injection on fuel antiknock performance. ...
... However, daily sources show that more recently the ethanol spot price can be higher than gasoline due to market volatility changes (Oil Price Information Services, 2015). Based on this and the current high volatility but consistent cost competiveness of ethanol and gasoline and a break even tank mileage possible from E20-E30 fuels (Jung et al., 2013a;Splitter and Szybist, 2014a), it seems possible that the national octane level of regular grade could be increased to 89 AKI via E15, and premium grade could be increased to 95 AKI via E25. Although compatibility will need to be considered for vehicles older than MY 2001, the EPA has declared that vehicles newer than MY 2001 are legally E15 compatible (Federal Register, 2011); with research supporting this work critically investigates differences between E15 and E10 and cites that no significant differences were found (West et al., 2012;McCormick et al., 2013). ...
In this work, the authors reviewed engine, vehicle, and fuel data since 1925 to examine the historical and recent coupling of compression ratio and fuel antiknock properties (i.e., octane number) in the U.S. light-duty vehicle market. The analysis identified historical time frames and trends and illustrated how three factors—consumer preferences, technical capabilities, and regulatory legislation—affect personal mobility. Data showed that over many decades these three factors have a complex and time-sensitive interplay. Long-term trends in the data were identified where interaction and evolution between all three factors were observed. Specifically, transportation efficiency per unit power (gal/ton-mi/hp) was found to be a good metric to integrate technical, societal, and regulatory effects into the evolutional pathway of personal mobility. From this framework, discussions of future evolutionary changes to personal mobility are also presented, with a focus centered on how increasing fuel octane number can help to enable sustained improvement in transportation efficiency per unit power.
... Ford and AVL have shown that ethanol enables efficiency improvements, with several notable works summarized in Stein et al. [11]. Vehicle-specific effects were researched by Jung et al. [12] at light load conditions and also in an additional study by Jung et al. [13] with drive cycle and engine efficiency estimates. The latter study points out that a light-duty pickup truck engine with intermediate ethanol-gasoline blends could be optimized such that the thermal efficiency increase with ethanol-gasoline blends of 20% ethanol vol./vol. ...
... The second observation from Figure 5, is that the load for the onset of knock between 87AKI 9.2 r c and 11.85 r c E30 is identical. Jung et al. [13] demonstrates that a 10 percent volume increase in ethanol with ethanol-gasoline blends enabled a 2 point increase in compression ratio with similar knock limited phasing. Their results were validated against E10 gasoline with E20 or E30 blends. ...
... Since the higher compression piston was non-optimized, the potential for further improvements or relaxation of EGR requirement for high r c E30 breakeven MPG may be possible. These findings are similar to those shown by Jung et al. [13], which demonstrate that intermediate alcohol-gasoline bio-fuels can achieve equivalent MPG to conventional distillate fuels with different higher r c engines. decreased MPG compared to 87AKI. ...
The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in mid-level alcohol-gasoline blends with 24% vol./vol. iso-butanol-gasoline (IB24) and 30% vol./vol. ethanol-gasoline (E30). A single-cylinder research engine is used with a low and high compression ratio of 9.2:1 and 11.85:1 respectively. The engine is equipped with hydraulically actuated valves, laboratory intake air, and is capable of external exhaust gas recirculation (EGR). All fuels are operated to full-load conditions with λ=1, using both 0% and 15% external cooled EGR. The results demonstrate that higher octane number bio-fuels better utilize higher compression ratios with high stoichiometric torque capability. Specifically, the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with the 11.85:1 compression ratio using E30 as compared to 87 AKI, up to 20 bar IMEPg at λ=1 (with 15% EGR, 18.5 bar with 0% EGR). EGR was shown to provide thermodynamic advantages with all fuels. The results demonstrate that E30 may further the downsizing and downspeeding of engines by achieving increased low speed torque, even with high compression ratios. The results suggest that at mid-level alcohol-gasoline blends, engine and vehicle optimization can offset the reduced fuel energy content of alcohol-gasoline blends, and likely reduce vehicle fuel consumption and tailpipe CO2 emissions.
... A study by Ford evaluated splash blended 91 RON E10, 96 RON E20 and 101 RON E30 fuels in a 3.5L GTDI "EcoBoost" engine at 10:1 and 11.9:1 CR [27]. In this engine, E20 at 11.9:1 CR exhibited knock-limited performance equivalent to that of E10 at 10.0 CR. ...
... Thus, a mid-level ethanol-gasoline blend (greater than E20 and less than E40) appears to be attractive as a long-term future fuel for automotive engines in the U.S. As an example, E30 has approximately 7% lower energy content per volume compared to E10. This can be partially or perhaps completely offset by improved thermal efficiency enabled by the higher octane rating of E30, which allows increased CR [27] and greater amounts of engine downsizing. Using current regulargrade E10 blendstocks, E30 would have correspondingly higher octane ratings, approximately 100 RON and 94 AKI. ...
... Using current regulargrade E10 blendstocks, E30 would have correspondingly higher octane ratings, approximately 100 RON and 94 AKI. For engines realizing the potential benefit of higher octanerating E30, the peak pressure requirement will be moderately higher than for E10, but still within the range of conventional SI engine design practice [27]. PM emissions for E30 should be less than for E10, and startability and cold start emissions at very low temperatures will be better than for high ethanol blends such as E85. ...
This paper provides an overview of the effects of blending ethanol with gasoline for use in spark ignition engines. The overview is written from the perspective of considering a future ethanol-gasoline blend for use in vehicles that have been designed to accommodate such a fuel. Therefore discussion of the effects of ethanol-gasoline blends on older legacy vehicles is not included.
As background, highlights of future emissions regulations are discussed. The effects on fuel properties of blending ethanol and gasoline are described. The substantial increase in knock resistance and full load performance associated with the addition of ethanol to gasoline is illustrated with example data. Aspects of fuel efficiency enabled by increased ethanol content are reviewed, including downsizing and downspeeding opportunities, increased compression ratio, fundamental effects associated with ethanol combustion, and reduced enrichment requirement at high speed/high load conditions. The effects of ethanol content on emissions are also reviewed, including NMOG/CO/NOX, particulate matter, toxic compounds, and off-cycle and evaporative emissions.
Considering the engine and vehicle-related factors reviewed in this paper, a mid-level ethanol-gasoline blend (greater than E20 and less than E40) appears to be attractive as a future fuel. To provide high knock resistance, this fuel should be formulated using a blendstock that retains the octane of the current blendstock used for regular-grade E10 gasoline. Further work is needed to recommend a specific ethanol blend level, including analysis of fuel efficiency and CO₂ benefits for representative powertrain/vehicle applications, and of fuel production and supply considerations.
... Prototype pistons were designed for CRs of 11.9:1 and 13.0:1, in addition to the production baseline CR of 10.0:1. In the first part of the study documented in [1], tests were run with CRs of 10.0:1 and 11.9:1 on the same engine. For the second part of the study tests were run with CRs of 10.0:1, 11.9:1, and 13.0:1 on a second engine. ...
... As shown in Table 2, the splash-blend fuels had slightly lower carbon intensity (0.2% for E20 and 0.4% for E30) relative to the E10-91RON baseline fuel, all from the prior study [1]. The carbon intensity of the match-blend E20 and E30 fuels were lower, but similar (within 0.4%) to the baseline E10-91RON fuel used in the testing shown in Figure 8, and as shown in Table 3. ...
... This section summarizes results previously obtained [1] with the splash blend fuels E20-96RON and E30-101RON compared to E10-91RON ( Table 2). Combustion phasing and lambda for load sweeps at 1500 rpm at 10:1 CR are shown in Figure 9. ...
Engine dynamometer testing was performed comparing fuels having different octane ratings and ethanol content in a Ford 3.5L direct injection turbocharged (EcoBoost) engine at three compression ratios (CRs). The fuels included midlevel ethanol “splash blend” and “octane-matched blend” fuels, E10-98RON (U.S. premium), and E85-108RON.
For the splash blends, denatured ethanol was added to E10-91RON, which resulted in E20-96RON and E30-101 RON. For the octane-matched blends, gasoline blendstocks were formulated to maintain constant RON and MON for E10, E20, and E30.
The match blend E20-91RON and E30-91RON showed no knock benefit compared to the baseline E10-91RON fuel. However, the splash blend E20-96RON and E10-98RON enabled 11.9:1 CR with similar knock performance to E10-91RON at 10:1 CR. The splash blend E30-101RON enabled 13:1 CR with better knock performance than E10-91RON at 10:1 CR. As expected, E85-108RON exhibited dramatically better knock performance than E30-101RON.
The data were used in a vehicle simulation of a 3.5L EcoBoost F150, which showed that E20-96 RON at 11.9:1 CR offers 5% improvement in tailpipe CO2 emissions and 1% improvement in miles per gallon (MPG) fuel economy relative to E10-91RON at 10:1 CR. E30-101 RON at 13:1 CR in this vehicle yielded 6−9% improvement in CO2 emissions and 2% worse to 1% better MPG fuel economy, depending on the drive cycle.
The match blend fuels resulted in no opportunity for improved efficiency, and degradation of MPG fuel economy due to reduced heating value per volume.
... The HoV of a fuel mixture affects brake thermal efficiency by several other mechanisms. Jung et al. performed experiments and analysis to determine the mechanisms by which efficiency is improved with a blend of 15% gasoline and 85% ethanol (E85) compared to operation with gasoline for throttled conditions [214] . With the E85 fuel, HC and carbon dioxide (CO 2 ) emissions are reduced, and η comb increases. ...
... Jung et al. provided an empirical estimate for the second group of terms in Eq. 21 and found that, overall, vaporization cooling increased the thermal efficiency of a throttled DI engine by about 4.2% between E0 and E85 or 1% for an increase in HoV of ∼130 kJ/kg [214] . The estimate is likely conservative due to the relatively large displacement of the test engine compared to the displacement expected for a downsized engine. ...
The Co-Optimization of Fuels and Engines (Co-Optima) initiative from the US Department of Energy aims to co-develop fuels and engines in an effort to maximize energy efficiency and the utilization of renewable fuels. Many of these renewable fuel options have fuel chemistries that are different from those of petroleum-derived fuels. Because practical market fuels need to meet specific fuel-property requirements, a chemistry-agnostic approach to assessing the potential benefits of candidate fuels was developed using the Central Fuel Property Hypothesis (CFPH). The CFPH states that fuel properties are predictive of the performance of the fuel, regardless of the fuel's chemical composition. In order to use this hypothesis to assess the potential of fuel candidates to increase efficiency in spark-ignition (SI) engines, the individual contributions towards efficiency potential in an optimized engine must be quantified in a way that allows the individual fuel properties to be traded off for one another. This review article begins by providing an overview of the historical linkages between fuel properties and engine efficiency, including the two dominant pathways currently being used by vehicle manufacturers to reduce fuel consumption. Then, a thermodynamic-based assessment to quantify how six individual fuel properties can affect efficiency in SI engines is performed: research octane number, octane sensitivity, latent heat of vaporization, laminar flame speed, particulate matter index, and catalyst light-off temperature. The relative effects of each of these fuel properties is combined into a unified merit function that is capable of assessing the fuel property-based efficiency potential of fuels with conventional and unconventional compositions.
... In fact, recently published data from Department of Energy (DOE) national laboratories Szybist, 2014a, 2014b;Szybist, 2010;Szybist and West, 2013) and OEMs (Anderson, 2013) and discussions with the U.S. Environmental Protection Agency (EPA) suggest the potential of a new high octane fuel (HOF) with 25-40 vol % of ethanol to assist in reaching Renewable Fuel Standard (RFS2) and greenhouse gas (GHG) emissions goals. This mid-level ethanol content fuel, with a research octane number (RON) of about 100, appears to enable efficiency improvements in a suitably calibrated and designed engine/vehicle system that are sufficient to offset its lower energy density (Jung, 2013;Thomas, et al, 2015). This efficiency improvement would offset the tank mileage (range) loss typically seen for ethanol blends in conventional gasoline and flexible-fuel vehicles (FFVs). ...
... HOF enables less spark retard and significantly improved efficiency. These results are consistent with those reported by others with turbocharged, direct-injection engines (Jung, 2013;Leone, 2014). Note that the energy density difference between E0 and E15 is very similar to that expected between E10 and E25. ...
... This is attributed to a high yield of molar products for alcohols on both a stoichiometric and energy basis relative to petroleum distillates, increasing expansion pressure. 9,10 Ford and AVL have shown that ethanol enables efficiency improvements, with several notable works summarized in Stein et al. 11 Vehiclespecific effects were researched by Jung et al. 12 at light load conditions and also in an additional study by Jung et al. 13 with drive cycle and engine efficiency estimates. The latter study points out that a light-duty pickup truck engine with intermediate ethanol−gasoline blends could be optimized such that the thermal efficiency increase with ethanol−gasoline blends of 20% ethanol vol/vol are sufficiently high to at least offset the fuel mileage penalty of alcohol fuels (miles per gallon, [MPG]) and achieve even greater tailpipe CO 2 reductions. ...
... Additionally, note that the trends in Figure 13 are dependent on the assumption of 25% maximum overall turbocharger efficiency and FMEP of the E30+15% EGR map. The assumptions used are reasonable (FMEP in Figure 7 and 25% overall turbocharger efficiency) because the peak BTE of the present study is nearly identical to that obtained by Jung et al., 13 which measured brake-based numbers from a multicylinder engine with a near identical compression ratio (11.9 vs 11.85) and fuel (E30). ...
... This is attributed to a high yield of molar products for alcohols on both a stoichiometric and energy basis relative to petroleum distillates, increasing expansion pressure. 9,10 Ford and AVL have shown that ethanol enables efficiency improvements, with several notable works summarized in Stein et al. 11 Vehiclespecific effects were researched by Jung et al. 12 at light load conditions and also in an additional study by Jung et al. 13 with drive cycle and engine efficiency estimates. The latter study points out that a light-duty pickup truck engine with intermediate ethanol−gasoline blends could be optimized such that the thermal efficiency increase with ethanol−gasoline blends of 20% ethanol vol/vol are sufficiently high to at least offset the fuel mileage penalty of alcohol fuels (miles per gallon, [MPG]) and achieve even greater tailpipe CO 2 reductions. ...
... Additionally, note that the trends in Figure 13 are dependent on the assumption of 25% maximum overall turbocharger efficiency and FMEP of the E30+15% EGR map. The assumptions used are reasonable (FMEP in Figure 7 and 25% overall turbocharger efficiency) because the peak BTE of the present study is nearly identical to that obtained by Jung et al., 13 which measured brake-based numbers from a multicylinder engine with a near identical compression ratio (11.9 vs 11.85) and fuel (E30). ...
The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in midlevel alcohol–gasoline blends with 24% vol/vol isobutanol–gasoline (IB24) and 30% vol/vol ethanol–gasoline (E30). A single-cylinder research engine was used with an 11.85:1 compression ratio, hydraulically actuated valves, laboratory intake air, and was capable of external exhaust gas recirculation (EGR). Experiments were conducted with all fuels to full-load conditions with λ = 1, using both 0% and 15% external cooled EGR. Higher octane number biofuel blends exhibited increased stoichiometric torque capability at this compression ratio, where the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with E30 as compared to 87 AKI, up to 20 bar IMEPg (indicated mean effective pressure gross) at λ = 1. EGR provided thermodynamic advantages and was a key enabler for increasing engine efficiency for all fuel types. However, with E30, EGR was less useful for knock mitigation than gasoline or IB24. Torque densities with E30 with 15% EGR at λ = 1 operation were similar or better than a modern EURO IV calibration turbo-diesel engine. The results of the present study suggest that it could be possible to implement a 40% downsize + downspeed configuration (1.2 L engine) into a representative midsize sedan. For example, for a midsize sedan at a 65 miles/h cruise, an estimated fuel consumption of 43.9 miles per gallon (MPG) (engine out 102 g-CO2/km) could be achieved with similar reserve power to a 2.0 L engine with 87AKI (38.6 MPG, engine out 135 g-CO2/km). Data suggest that, with midlevel alcohol–gasoline blends, engine and vehicle optimization can offset the reduced fuel energy content of alcohol–gasoline blends and likely reduce vehicle fuel consumption and tailpipe CO2 emissions.
... Knock resistance of fuel governs the compression ratio of any engine, and for ethanol is less than the best value for operation ( Jung et al. 2013b ). Many research works have been conducted on the compression ratio within the flexible fuel engine performance, which was running with a mixture of hydrous ethanol (E100) or 22% anhydrous ethanol and 78% gasoline mixture (E22) as fuel ( Jung et al. 2013a ). Table 1presents the most popular characteristics of hydrous E22 and ethanol, which could be employed later to investigate the effect of fuel on engine efficiency parameters ( Costa and Sodr é Jos é 2011 ). ...
... Hsieh et al. (2002) have analyzed the consequences of gasoline and ethanol blends on emission of SI engine. They analyzed samples of 99.9% pure ethanol and ethanol-gasoline blend by using a volumetric ratio range between 0% and 30% (E0, E5, E10, E20, and E30) ( Jung et al. 2013a ). These percentages of blends were represented by the ethanol ratio in the whole blends. ...
Biofuels are acting as a renewable replacement for petroleum fuels due to some environmental and economic benefits. They are prepared by blending a major portion of diesel fuel and a certain minor percentage of bio-oils, which provides less greenhouse gas (GHG) compared to pure diesel. Recently, bioethanol has been the most widely used biofuel for transportation. Bioethanol can be produced from different kinds of agricultural raw materials classified into three categories: simple sugars, starch, and lignocellulose. Use of bioethanol-blended gasoline fuel for automobiles can significantly reduce petroleum use and exhaust GHG emission. Bioethanol from sugar cane, produced under the proper conditions, is essentially a clean fuel and has several clear advantages over petroleum-derived gasoline in reducing GHG emissions and improving air quality in metropolitan areas. However, there remains a compromise between GHG emission and saving of fossil fuel energy by introducing bioethanol either totally or as a blending component of engine fuel. Thus, considering biofuel as a replenishable energy source, the future pathway of energy management could be planned.
... High octane bioethanol blends enable to improve energy efficiency and, as a result, vehicle energy economy [58,59]. Fuel economy impacts on decision-making. ...
Historically, petroleum fuels have been the dominant fuel used for land transport. However, the growing need for sustainable national economics has urged us to incorporate more economical and ecological alternative vehicle fuels. The advantages and disadvantages of them complicate the decision-making process and compel us to develop adequate mathematical methods. Alternative fuel (compressed natural gas, liquefied petroleum gas, and ethanol fuel mixtures), the standard prices and their ratios were investigated. A mathematical model to determine a critical ratio between alternative and conventional fuel prices had already been developed. The results of this were investigated. The results showed that the critical ratio is not a linear function on annual conventional fuel consumption costs. According to our simulation gaseous fuels were economically more attractive. Whereas, the use of bioethanol blends had more risk.
... Vehicle manufacturers along with component developers, suppliers and research institutions are pursuing a wide range of technologies to increase fuel economy and reduce emissions. This pursuit includes engine technologies such as downsped and downsized turbocharged engines, which could benefit from improved antiknock properties of fuel (Jung et al., 2013;Splitter and Szybist, 2014;Leone et al., 2014;Theiss et al., 2016) and novel advanced combustion approaches such as reactivity-controlled compression ignition (RCCI), gasoline compression ignition (GCI), homogeneous-charge compression ignition (HCCI), and several other low temperature combustion approaches (examples include: Chadwell et al., 2011;Ciatti et al., 2013;Dec et al., 2004;Dempsey et al., 2015;Dempsey et al., 2016;Manente et al., 2009;Musculus et al., 2013;Najt and Foster, 1983;Ryan and Callahan, 1996;Suresh et al., 2013;Wagner et al., 2003). ...
History of Significant Vehicle and Fuel
Introductions in the United States
... Linear extrapolation was required to extend the maps to 5000 rpm. This high speed region of the map is not considered important for most drive cycles [47,48]. ...
Advanced engine technologies will play a central role in achieving future greenhouse gas (GHG) emissions targets for light-duty vehicles. However, these technologies will place greater emphasis on optimizing the engine and fuel as a synergistic system, since many technologies will require higher octane gasolines to realize their full social and environmental benefits. The most extreme example of a synergistic engine-fuel system is the Octane-on-Demand concept. This technology platform makes use of an oil-derived fuel at low and intermediate loads where the octane requirement of the engine is comparatively low, while a second high octane fuel is introduced at higher loads to suppress knock. This paper presents the first comprehensive study of vehicle fuel economy and well-to-wheel GHG emissions for the Octane-on-Demand concept with respect to a regular grade E10 gasoline (RON 93) and a high octane E30 gasoline (RON 101). Experimental fuel consumption maps are first used to evaluate the drive cycle fuel economy and GHG emissions for a light-duty vehicle equipped with two alternative powertrains. The upstream GHG emissions arising from the production of the fuels are then quantified, with consequent uncertainties assessed using Monte Carlo analysis based on probability distribution functions for critical input parameters. The results demonstrate that the Octane-on-Demand concept used in conjunction with either methanol or ethanol generally provides comparable well-to-wheel GHG emissions to the high octane E30 gasoline, with up to a 10% improvement in the vehicle fuel economy. The use of a non-traditional engine calibration strategy that maximizes the trade-off between thermal efficiency and fuel energy density also enables the amount of high octane fuel required to suppress knock to be reduced significantly. This increases the distance that the vehicle can be driven before the secondary tank requires refueling by a considerable margin, but comes at the expense of marginally higher well-to-wheel GHG emissions than could otherwise be achieved. These findings are shown to be largely insensitive to uncertainties in the upstream fuel production GHG emissions, with the exception of the land use change (LUC) for bioethanol. Overall, this study has implications for the design of engine-fuel systems for future light-duty vehicles.
... This enables higher thermal efficiencies to be achieved from engines that have been optimized to exploit the superior fuel octane quality. Nevertheless, volumetric fuel economy parity with existing market gasolines has so far been difficult to achieve, due to the lower energy density of fuels with significant methanol or ethanol content [31][32][33][34]. ...
Higher octane gasoline will be an important factor in enabling future spark-ignition engines to meet increasingly stringent fuel economy and CO2 emissions requirements. The most effective method to raise the octane ‘floor’ of regular grade gasoline is through the use high octane blend components, such as methanol and ethanol. However, this is often limited by the negative effects associated with energy density, phase separation and cold engine starting. This paper therefore examines the optimal way to leverage the most widely available high octane fuels to improve the performance and environmental impact of light-duty vehicles. A comprehensive set of baseline engine data is first presented for two splash-blended gasolines containing ethanol (E10 and E30). The octane quality of these fuels (RON 93 and 101) has been raised by directly displacing the gasoline blendstock (RON 90) with higher octane ethanol (RON 109). The two splash-blended gasolines are compared with the Octane-on-Demand concept, which instead leverages only the necessary amount of high octane fuel when the octane requirement of the engine exceeds the level that can be provided by the oil-derived base fuel. The same gasoline blendstock is used in both cases, thus enabling the leveraging effect of the high octane fuels in the Octane-on-Demand configuration to be directly quantified. The results demonstrate that the Octane-on-Demand concept used in conjunction with either methanol or ethanol provides comparable or lower specific CO2 emissions to the E30 gasoline, with up to a 10% improvement in specific fuel consumption. The use of a non-traditional engine calibration strategy that maximizes the trade-off between thermal efficiency and fuel energy density also enables the amount of high octane fuel required to suppress knock to be reduced by at least 25%, with methanol offering the greatest benefits. This however comes at the expense of marginally higher specific CO2 emissions than could otherwise be achieved. Overall, this work suggests that powertrains designed around the Octane-on-Demand concept may provide greater social and environmental benefits than those designed for high octane splash-blended gasolines with significant methanol or ethanol content.
... There are many researchers who have studied splash blended ethanol fuels in spark ignition engines and achieved promising results. For example, Jung et al. [12] studied E10, E20, and E30 fuels in a Ford 3.5 L EcoBoost DI turbocharged engine with compression ratios (CR) of 10.0:1 and 11.9:1. It was found that a 10 vol.% increase of ethanol in the blends enabled a 2 unit increase of CR without changing the knock limited combustion phase. ...
Downsized spark ignition engines have the benefit of high thermal efficiency; however, severe engine knock is a challenge. Ethanol, a renewable gasoline alternative, has a much higher octane rating and heat of vaporization than conventional gasoline, therefore, ethanol fuels are one of the options to prevent knock in downsized engines. However, the performance of ethanol blends in modern downsized engines, and the contributions of the research octane number (RON), octane sensitivity (defined as RON-MON) and charge cooling to suppressing engine knock are not fully understood. In this study, eight fuels were designed and tested, including four splash blended ethanol fuels (10 vol.%, 20 vol.%, 30 vol.% and 85 vol.% ethanol, referred to as E10, E20, E30 and E85), one match blended fuel (E0-MB) with no ethanol content but the same octane rating as E30, and three fuels (F1-F3) with different combinations of RON and octane sensitivity. The experiments were conducted in a single-cylinder direct-injection spark ignition (DISI) research engine. Load and spark timing sweep tests at 1800 rpm were carried out for E10-E85 to assess the combustion performance of these ethanol blends. In order to investigate the impact of charge cooling on combustion characteristics, the results of the load sweep for E0-MB were compared to those of E30. Load sweep tests were also carried out for F1-F3 to understand the impacts of RON and octane sensitivity on suppressing engine knock. The results showed that at the knock-limited engine loads, splash blended ethanol fuels with a higher ethanol percentage enabled higher engine thermal efficiency through allowing more advanced combustion phasing and less fuel enrichment for limiting the exhaust gas temperature under the upper limit of 850 °C, which was due to the synergic effects of higher RON and octane sensitivity, as well as better charge cooling. In comparison with octane sensitivity, RON was a more significant factor in improving engine thermal efficiency. Charge cooling reduced engine knock tendency through lowering the unburned gas temperature.
... This study adds investigation of K at part load conditions which are not as knocklimited. Modern turbocharged engines start to become knock-limited at much lower loads than naturally aspirated engines, even under throttled conditions, which constrains fuel economy and CO 2 emissions on heavily loaded test cycles like US06 [10,11,12]. Knowledge of K is needed for a wide range of conditions including some which were not knock-limited for the baseline fuel and compression ratio. ...
Combustion in modern spark-ignition (SI) engines is increasingly knock-limited with the wide adoption of downsizing and turbocharging technologies. Fuel autoignition conditions are different in these engines compared to the standard Research Octane Number (RON) and Motor Octane Numbers (MON) tests. The Octane Index, OI = RON - K(RON-MON), has been proposed as a means to characterize the actual fuel anti-knock performance in modern engines. The K-factor, by definition equal to 0 and 1 for the RON and MON tests respectively, is intended to characterize the deviation of modern engine operation from these standard octane tests. Accurate knowledge of K is of central importance to the OI model; however, a single method for determining K has not been well accepted in the literature.
This paper first examines four different methods for determining K, using literature results from a modern SI engine operating with direct injection (DI), port fuel injection (PFI) and homogeneous, upstream fuel injection (UFI). The test fuels were ethanol-gasoline blends spanning a wide range of RON and MON, together with isooctane as a reference. The quality of the K results from some of these methods is particularly dependent on the design of the test fuel matrix, with unreliable K values resulting in some cases.
One of the more reliable methods is then used to examine how K varies with the intake pressure, fueling strategy, engine speed and compression ratio, with throttled conditions considered in detail. Several of the observed trends are consistent with prior studies, including K being consistently negative at higher loads for DI. In contrast to other studies, however, K is also observed to approach 0.5 at part load, throttled conditions, irrespective of whether the engine is fuelled by DI, PFI or UFI. Preliminary analysis of the autoignition chemistry for different fuelling methods then suggests plausible reasons for these results.
... In most cases, these splash-blended fuels exhibit comparable or marginally higher anti-knock quality than standard gasolines, but this is often offset by a lower volumetric energy density [5,11]. For these reasons, several studies indicate that such fuels can only provide limited fuel economy and CO 2 emissions benefits when utilized in both optimized and non-optimized engine applications [12,13,14,15,16,17,18]. In particular, fuels with modest oxygenate levels often lead to higher volumetric fuel consumption rates during urban driving. ...
... The splash-blending process typically produces finished fuels with comparable or marginally higher anti-knock quality than standard gasolines, but often with a much lower volumetric energy density [6,9]. For these reasons, several studies indicate that such fuels can only provide limited benefits when utilized in both optimized and non-optimized engine applications [10,11,12,13,14,15,16,17,18]. In particular, fuels with modest oxygenate levels often lead to higher volumetric fuel consumption rates during urban driving. ...
... 7 Recent studies examined increased ethanol content in gasoline and its impacts on engine performance with favorable results. Jung et al. 8 tested splash-blended E10, E20, and E30 fuels in a Ford 3.5L EcoBoost direct injection turbocharged engine at CRs of 10.0:1 and 11.9:1. Results showed E30 (101 RON) at a 11.9:1 CR reduced CO 2 emissions by 5% and 7.5% on the EPA M/H (Metro Highway) cycle and US06 Highway cycles, respectively, while volumetric fuel economy was 3% lower on the M/H cycle and approximately equal on the US06 Highway cycle, compared to E10 fuel at a 10:1 CR. ...
Refinery GHG emissions were predicted for 10% and 30% ethanol blends at refinery blendstock octanes between 77 and 89 AKI at any gasoline pool energy content between parity and constant gasoline pool volume. Linear programming analyzed how separate E30 blending scenarios of 2017 PADD 2-based refineries affect greenhouse gas (GHG) emissions relative to status quo gasoline (i.e., E10, 87 AKI and 93 AKI premium). The compliance synergy of higher ethanol blends illustrated here is pertinent to national policy goals and multiple environmental objectives. Study results have implications for CAFE Standards, US EPA Tier 3 fuel standards, and Clean Air Act regulations of stationary source CO2 emissions from refinery operations. Results varied by amounts and types of crude oil processed, refinery operations, refinery gasoline blendstock produced (and fuel ethanol blended), and produced refinery product composition and properties. Significant differences exist in total refinery GHG emissions (including emissions from purchased electricity and hydrogen) with the largest differences from coke burn in the fluidized catalytic cracker and refinery fuel gas combustion principally related to reformer operations. The concept of refinery GHG emissions intensity was introduced to differentiate between differences in refinery throughput (an extensive factor) and severity of refinery operations (intensive factors). Refinery GHG emissions decline 12% to 27% from a 2017 base case for the various 30% ethanol cases, highlighting a significant gap in current life cycle analysis (LCA) and supporting incorporation of this improved approach into LCA related to higher ethanol blends. This methodology can be adapted to other PADDs and/or for the USA. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd.
... However, due to ethanol having a higher latent heat of vaporization and boiling point it is unfavorable for the cold start condition in a spark-ignited engine [7,8,9,10]. Furthermore, ethanol has a lower energy density, so when it is used in real cars, the cruising distance becomes shorter due to restricted fuel tank size [11,12]. Therefore, ethanol is widely used currently in blended form with gasoline rather than its pure form. ...
Ethanol is becoming more popular as a fuel component for spark-ignited engines. Ethanol can be used either as an octane enhancer of low RON gasoline or splash-blended with gasoline if a single injector is used for fuel injection. If two separate injectors are used, it is possible to inject gasoline and ethanol separately and the addition of ethanol can be varied on demand. In this study, the effect of the ethanol injection strategy on knock suppression was observed using a single cylinder engine equipped with two port fuel injectors dedicated to each side of the intake port and one direct injector. If the fuel is injected to only one side of the intake port, it is possible to form a stratified charge. The experiment was conducted under a compression ratio of 12.2 for various injection strategies. From the experimental results, it was found that injecting ethanol to the left side only of the intake port while both intake valves were open required approximately 52.1% (at 1500rpm) or 60.6% (at 2000rpm) less ethanol compared to the case in which ethanol is injected to both sides of intake port while intake valves are closed under a similar level of knock frequency. Furthermore, the engine load was maintained to the same level.
... Whilst this may cause issues of consumer acceptance, recent research suggests that it can be addressed by exploiting ethanol's high octane rating and increasing the engine compression ratio [9,14]. ...
This paper presents a numerical study of trace knocking combustion of ethanol/gasoline blends in a modern, single cylinder SI engine. Results are compared to experimental data from a prior, published work [1]. The engine is modeled using GT-Power and a two-zone combustion model containing detailed kinetic models. The two zone model uses a gasoline surrogate model [2] combined with a sub-model for nitric oxide (NO) [3] to simulate end-gas autoignition. Upstream, pre-vaporized fuel injection (UFI) and direct injection (DI) are modeled and compared to characterize ethanol's low autoignition reactivity and high charge cooling effects. Three ethanol/gasoline blends are studied: E0, E20, and E50. The modeled and experimental results demonstrate some systematic differences in the spark timing for trace knock across all three fuels, but the relative trends with engine load and ethanol content are consistent. Possible reasons causing the differences are discussed. Finally, the influence of NO on autoignition is investigated, yielding results that are consistent with prior works. Overall, the same, two-zone kinetic model appears to capture both the UFI and DI autoignition similarly well. These results also provide further evidence suggesting that inclusion of a NO sub-model is necessary for mechanistically accurate modeling of autoignition and knock in general.
... This is attributed to a high yield of molar products for alcohols on both a stoichiometric and energy basis relative to petroleum distillates, increasing expansion pressure. 9,10 Ford and AVL have shown that ethanol enables efficiency improvements, with several notable works summarized in Stein et al. 11 Vehiclespecific effects were researched by Jung et al. 12 at light load conditions and also in an additional study by Jung et al. 13 with drive cycle and engine efficiency estimates. The latter study points out that a light-duty pickup truck engine with intermediate ethanol−gasoline blends could be optimized such that the thermal efficiency increase with ethanol−gasoline blends of 20% ethanol vol/vol are sufficiently high to at least offset the fuel mileage penalty of alcohol fuels (miles per gallon, MPG) and achieve even greater tailpipe CO 2 reductions. ...
The present study experimentally investigates spark-ignited combustion with 87 AKI E0 gasoline in its neat form and in midlevel alcohol–gasoline blends with 24% vol/vol isobutanol–gasoline (IB24) and 30% vol/vol ethanol–gasoline (E30). A single-cylinder research engine is used with an 11.85:1 compression ratio, hydraulically actuated valves, laboratory intake air, and was capable of external exhaust gas recirculation (EGR). Experiments were conducted with all fuels to full-load conditions with λ = 1, using both 0% and 15% external-cooled EGR. Higher octane number biofuel blends exhibited increased stoichiometric torque capability at this compression ratio, where the unique properties of ethanol enabled a doubling of the stoichiometric torque capability with E30 as compared to that of 87AKI, up to 20 bar IMEPg (indicating mean effective pressure gross) at λ = 1. The results demonstrate that for all fuels, EGR is a key enabler for increasing engine efficiency but is less useful for knock mitigation with E30 than for 87AKI gasoline or IB24. Under knocking conditions, 15% EGR is found to offer 1°CA of CA50 timing advance with E30, whereas up to 5°CA of CA50 advance is possible with knock-limited 87AKI gasoline. Compared to 87AKI, both E30 and IB24 are found to have reduced adiabatic flame temperature and shorter combustion durations, which reduce knocking propensity beyond that indicated by the octane number. However, E30+0% EGR is found to exhibit the better antiknock properties than either 87AKI+15% EGR or IB24+15% EGR, expanding the knock limited operating range and engine stoichiometric torque capability at high compression ratio. Furthermore, the fuel sensitivity (S) of E30 was attributed to reduced speed sensitivity of E30, expanding the low-speed stoichiometric torque capability at high compression ratio. The results illustrate that intermediate alcohol–gasoline blends exhibit exceptional antiknock properties and performance beyond that indicated by the octane number tests, particularly E30.
... High octane, midlevel ethanol blends (e.g., 30% ethanol in gasoline), if widely available, could increase engine efficiency, reduce ethanol's mileage disadvantage, and reduce GHG emissions. 7 This would require cooperation by the auto and fuel industries and regulatory agencies to develop the necessary specifications and to make these new fuels widely available. Achieving high octane gasoline via intermediate ethanol blends reduces aromatics and other toxic components in gasoline and avoids intensive refining of crude oil, thereby improving public health outcomes while simultaneously improving fuel efficiency and reducing GHGs. ...
The US Congress passed the Renewable Fuels Standard (RFS) seven years ago. Since then, biofuels have gone from darling to scapegoat for many environmentalists, policy makers, and the general public. The reasons for this shift are complex and include concerns about environmental degradation, uncertainties about impact on food security, new access to fossil fuels, and overly optimistic timetables. As a result, many people have written off biofuels. However, numerous studies indicate that biofuels, if managed sustainably, can help solve pressing environmental, social and economic problems (Figure 1). The scientific and policy communities should take a closer look by reviewing the key assumptions underlying opposition to biofuels and carefully consider the probable alternatives. Liquid fuels based on fossil raw materials are likely to come at increasing environmental cost. Sustainable futures require energy conservation, increased efficiency, and alternatives to fossil fuels, including biofuels.
... 9 In addition to direct emissions impacts, higher ethanol content fuel can also provide more efficient combustion and overall engine operation under part-load conditions 10 and under knock-limited higherload conditions. 11,12 Designing and calibrating for optimal performance on midlevel ethanol blends represents a new consideration for FFV design. FFVs have historically been designed for operation on E0/E10 and E85 and are certified for emissions compliance by testing with E0 and E85. ...
Engine-out and tailpipe emissions of NOx, CO, non-methane hydrocarbons (NMHC), non-methane organic gases (NMOG), total hydrocarbons (THC), methane, ethene, acetaldehyde, formaldehyde, ethanol, N2O, and NH3 from a 2006 model year Mercury Grand Marquis flexible fuel vehicle (FFV) operating on E0, E10, E20, E30, E40, E55, and E80 on a chassis dynamometer are reported. With increasing ethanol content in the fuel, the tailpipe emissions of ethanol, acetaldehyde, formaldehyde, methane, and ammonia increased; NOx and NMHC decreased; while CO, ethene, and N2O emissions were not discernibly affected. NMOG and THC emissions displayed a pronounced minimum with mid-level (E20-E40) ethanol blends; 25-35% lower than for E0 or E80. Emissions of NOx decreased by approximately 50% as the ethanol content increased from E0 to E30-E40, with no further decrease seen with E55 or E80. We demonstrate that emission trends from FFVs are explained by fuel chemistry and engine calibration effects. Fuel chemistry effects are fundamental in nature; the same trend of increased ethanol, acetaldehyde, formaldehyde, and CH4 emissions and decreased NMHC and benzene emissions are expected for all FFVs. Engine calibration effects are manufacturer and model specific; emission trends for NOx, THC, and NMOG will not be the same for all FFVs. Implications for air quality are discussed.
This study aims to investigate the control mechanism of fuel properties and intake temperature (Tin) on the low-temperature polyoxymethylene dimethyl ethers (PODEn)/gasoline combustion to maximize the advantages of PODEn in enhancing engine performance. To achieve this goal, two representative combustion modes of partially premixed combustion (PPC) and reactivity-controlled compression ignition with reverse reactivity stratification (R-RCCI) with different fuel regulating methods were investigated. In PPC, the fuel was regulated by blending PODEn and gasoline outside the cylinder, while for R-RCCI, the in-cylinder fuel was tuned by delivering the two fuels into the cylinder with two different fuel supply systems. The main factors dominating the combustion process and pollutant emissions were identified for these two combustion modes. The results show that the combustion process of PPC is dominated by the collaborative organization of fuel reactivity and concentration in the cylinder, and 50% burn point (CA50) plays only a secondary role, but CA50 determines the nitrogen oxides (NOx) emission level. For PPC operated with the start of injection later than −40 °CA ATDC, increasing local fuel concentration is more effective in improving the combustion efficiency and indicated thermal efficiency than increasing Tin. For R-RCCI, the lower local temperature caused by the heat of vaporization of the directly injected gasoline remarkably influences the combustion process, but this cooling effect is not significant in PPC. The comparison of PPC and R-RCCI shows that the in-cylinder local fuel reactivity impacts the ignition more significantly than the overall fuel reactivity. Compared with PPC, R-RCCI can effectively reduce combustion instability and combustion rate, and simultaneously 26% reduction in NOx emissions was accomplished.
The depletion of non-renewable sources of fuel has evoked the research of alternative fuel for automobile sector. Currently, ethanol is an attractive fuel for blending with gasoline obtained from various feedstock and waste. E10 (10% ethanol) is currently commercialized and research is going on higher percentage of ethanol blend in gasoline to meet the energy demand and factor for reducing climate change by 2030. First generation ethanol (1GE) obtained from biofuel are commercialized and 2GE is still in development phase and lot of research is going on the commercialization. In this study, major focus is given on feedstock for ethanol production for reduction of global warming and climate change. In addition a major study has also been done to investigate the feedstock for ethanol production and found lignocellulose waste obtained from agro waste as a potential feedstock for ethanol production. The use of waste obtained from agro-industry has also overcome the limitation of land and water for crops to produce ethanol.
An experiment was conducted to explore the performance, combustion, and emission characteristics of the Miller cycle by asynchronous late intake valve closing (LIVC) on a direct-injection turbocharged gasoline engine. Asynchronous LIVC Miller cycle uses geometric compression ratio (GCR) of 12.5:1 (Miller-CR12.5), compared with Otto cycle original engine with GCR of 12.5:1 (Otto-CR12.5) and 10:1 (Otto-CR10). The study indicates that one late intake valve closing can not only realize the Miller cycle but also control the load to effectively reduce the pumping loss. When the brake mean effective pressure (BMEP) is below 4 bar, Miller-CR12.5 shows a very short combustion duration and lower combustion cycle variation compared with the Otto cycle, which solves the problem of low combustion efficiency due to the low actual compression ratio of the Miller cycle. In addition, the Miller cycle of asynchronous LIVC is similar to that of synchronous LIVC, which all can improve knock resistance at medium and high loads. Based on the above factors, Miller-CR12.5 reduces fuel consumption, especially at low and heavy loads. Besides, Miller-CR12.5 shows great fuel-saving potential at high speeds. In terms of emissions, Miller-CR12.5 significantly increases CO and THC emissions within the range of tested loads, but the NOx emissions are reduced under low and high loads.
The modern world visualizes the achievement of sustainable development goals by 2030 and hence, the idea of sustainable biorefinery has gained immense attention of researchers globally. One of the most abundant organic resources worldwide is the lignocellulosic biomass. Being a promising source of renewable energy, it offers a wide range of benefits due to its environment-friendly nature, ease of availability and affordability. Three fractions make up the lignocellulosic biomass-cellulose, hemicelluloses and lignin, making it a recalcitrant structure. To convert this lignocellulosic biomass into value-added products demand the disruption of its recalcitrant structure via pretreatment methods with acidic, alkaline and combined acidic-alkaline treatments being the common techniques in practice. However, the conventional pretreatment methods available are costly, consume heat as well as power, and produce a variety of secondary inhibitory compounds. These compounds hamper the accessibility of polysaccharides to the microbes and enzymes. There is a dire need to discover effective pretreatment strategies and their optimization in a way that overcomes the obstacles of operational costs, energy consumption and ensures efficiency and enhanced production of fermentable sugars. However, to make it applicable for industrial adaptation still remains a vague domain. This chapter provides an insight on the recent advances in the lignocellulosic biomass pretreatment strategies, along with an exclusive discussion and comparative study of their efficacy based on the composition of different feedstock materials. This analysis would be a doorway for the development of sustainable energy systems.
Oil derived vehicle fuels are mainly consumed by land transport. The transport sector of economy must currently get round a number of challenges caused by the following: a tendency of oil derived fuel price rise, uneven allocation of fossil fuels, their exhaustibility, and climate change caused by carbon dioxide emissions. The above forces to look for solutions of the above mentioned problems. One of the ways out is the use of alternative vehicle fuels. They must be renewable or have more reserves compared to crude oil, and environmentally friendly. The purpose of this study is to give tools to management of transport companies to be able to make appropriate decisions. The goal of alternative vehicle fuel management is to maximize profit and improve ecological indicators. To reach the above it is necessary to choose an alternative fuel, determine its consumption, reduce fuel consumed costs, and cut down harmful emissions mainly carbon dioxide.
Ethanol has shown substantial capacity for improving the emission and combustion. EGR can effectively and significantly reduce emissions. Based on the open-loop control system, the performance of GPI + EDI four-cylinder SI engine under different EDIr and EGR was studied under the operating conditions of λ = 1, speed = 1500rmp, DIT = 120° CA BTDC. The results show that, with the increase of EGR, IMEP first increases and then decreases, NOx keeps decreasing, BSFC, CO and HC first decreases and then increases, CoVPmax, CA 0–10 and CA 10–90 all increase. When EGR = 12%, EDIr = 15%, IMEP reaches the highest value of 0.417 MPa, which is about 10.74% higher than the original engine level. At this working point, BSFC reaches 307.22 g/(kW·h), which is about 10.49% lower than the original engine level. Until EGR = 12%, CoVPmax is always lower than baseline. And it has the largest average decrease of 31.49% at EDIr = 15%. When EGR = 12%, NOx can decrease about 164 ppm with an average increase of 1% EGR. At this time HC also drops to the lowest point, with an average drop of 39.80%. And the lowest value of CO is 0.32 vol% at EGR = 12%, EDIr = 45%. In summary, ethanol has a higher oxygen content and LFS is faster. EGR can not only reduce pumping losses and throttling losses, but also effectively accelerate the positive effects of ethanol on combustion and emissions. EGR + EDI + GPI can obviously increase the engine power performance, improve fuel economy and decline the gaseous emissions. 12%EGR + 15%EDI provides an innovative and optimal solution for ethanol/gasoline dual fuel SI engine coupled EGR.
In order to reach the goal of energy conservation and pollution emissions reduction, the combustion and emissions of a combined injection engine with ethanol port injection and gasoline direct injection under lean burn conditions are investigated in this paper. The experiments are carried out by using different direct injection timing (DIT), gasoline addition ratio (αgasoline) and excess air ratios (λ). The results indicate that Tmax declines after gasoline addition at λ = 1, 1.2, while increases after gasoline addition at λ = 1.4. The IMEP reaches the maximum value at DIT = 90 or 105 °CA BTDC and 0%, 10% and 30% gasoline addition bring the highest IMEP at λ = 1, 1.2 and 1.4, respectively. The COVIMEP decreases continuously with the increase of αgasoline and the EPI+GDI mode has great advantages in improving the combustion stability under λ = 1.4 condition. As for gaseous emissions, from λ = 1 to λ = 1.4, HC emissions change from increasing trend to the decreasing trend with the increase of αgasoline, while the NOx emissions show the opposite. As for particle number, at λ = 1 and 1.2, the total particle number (TPN) shows an upward trend with the increase of αgasoline. When λ = 1.4, TPN decreases with the increase of αgasoline.
The combustion and emission characteristics of a dual-fuel spark-ignition engine with direct injection of gasoline surrogates and port injection of ethanol were studied. Toluene reference fuel with different research octane number namely TRF#1, TRF#2, TRF#3, TRF#4 and TRF#5 were employed as gasoline surrogates, in which TRF#1 with high octane number was to simulate commercial gasoline under direct-injection spark-ignition mode as comparison. For dual-fuel spark-ignition mode, the ethanol port-injection ratios were 21%, 25%, 29%, 32% and 35%, respectively. The results demonstrated that with the increase of the ethanol ratio, the knock-limited spark timing was advanced gradually. The emissions of hydrocarbon, ethane, propylene, isopentane, cyclohexane and aromatic hydrocarbons reduced while CO, NOx, ethylene, acetaldehyde and ethanol increased. Compared to TRF#1 in direct-injection spark-ignition mode, the indicated thermal efficiencies of dual-fuel spark-ignition mode were slightly lower under most test conditions. When direct injection of TRF#3, TRF#4, TRF#5 and the ethanol ratio was higher than 29%, some of the indicated thermal efficiencies of the engine were consistent with or higher than that of TRF#1 in direct-injection spark-ignition mode. Based on dual-fuel spark-ignition mode and with the assistance of port injection of ethanol, the indicated thermal efficiency of low research octane number fuels was comparable to that of TRF#1 in direct-injection spark-ignition mode.
The effects of a broad range of fuel injection strategies on thermal efficiency and engine-out emissions (CO, total hydrocarbons, NOx and particulate number) were studied for gasoline and ethanol fuel blends. A state-of-the-art production multi-cylinder turbocharged gasoline direct injection engine equipped with piezoelectric injectors was used to study fuels and fueling strategies not previously considered in the literature. A large parametric space was considered including up to four fuel injection events with variable injection timing and variable fuel mass in each injection event. Fuel blends of E30 (30% by volume ethanol) and E85 (85% by volume ethanol) were compared with baseline E0 (reference grade gasoline). The engine was operated over a range of loads with intake manifold absolute pressure from 800 to 1200 mbar. A combined application of ethanol blends with a multiple injection strategy yielded considerable improvement in engine-out particulate and gaseous emissions while maintaining or slightly improving engine brake thermal efficiency. The weighted injection spread parameter defined in this study, combined with the weighted center of injection timing defined in the previous literature, was found well suited to characterize multiple injection strategies, including the effects of the number of injections, fuel mass in each injection and the dwell time between injections.
Increased biofuel content in automotive fuels impacts vehicle tailpipe vehicle emissions via two mechanisms: fuel chemistry and engine calibration. Fuel chemistry effects are generally well recognized, while engine calibration effects are not. It is important that investigations of the impact of biofuels on vehicle emissions consider the impact of engine calibration effects and are conducted using vehicles designed to operate using such fuels. We report the results of emission measurements from a Ford F-350 fueled with either fossil diesel or a biodiesel surrogate (butyl nonanoate) and demonstrate the critical influence of engine calibration on NOx emissions. Using the production calibration the emissions of NOx were higher with the biodiesel fuel. Using an adjusted calibration (maintaining equivalent exhaust oxygen concentration to that of the fossil diesel at the same conditions by adjusting injected fuel quantities) the emissions of NOx were unchanged, or lower, with biodiesel fuel. For ethanol, a review of the literature data addressing the impact of ethanol blend levels (E0-E85) on emissions from gasoline light-duty vehicles in the U.S. is presented. The available data suggest that emissions of NOx, non-methane hydrocarbons, particulate matter (PM), and mobile source air toxics (compounds known, or suspected, to cause serious health impacts) from modern gasoline and diesel vehicles are not adversely affected by increased biofuel content over the range for which the vehicles are designed to operate. Future increases in biofuel content when accomplished in concert with changes in engine design and calibration for new vehicles should not result in problematic increases in emissions impacting urban air quality and may in fact facilitate future required emissions reductions. A systems perspective (fuel and vehicle) is needed to fully understand, and optimize, the benefits of biofuels when blended into gasoline and diesel.
As CO2 emissions standards continue to tighten, engine efficiency has jumped to the forefront of automotive engine focus. A proven way to realize efficiency gains is through the increase of engine compression ratio, yet the data available that quantifies this trend are more limited than one would expect. In this paper results from various experimental and simulation studies are compiled to quantify the effect of compression ratio on modern spark- ignited engine efficiency. Four studies are taken from research conducted at the Sloan Automotive Laboratory at MIT and three are from the recent literature. Compression ratios range between 8 and 13.4 in these studies, and gross indicated efficiency, net indicated efficiency, and brake efficiency were compiled. Curves of efficiency versus compression ratio are fit to the data points for each of the studies and normalized about a compression ratio of 10. Average curves for each of the three efficiency types across all data available show that increasing from a compression of 10 to 13 results in relative increases of 5.1% for brake efficiency, 4.6% for gross indicated efficiency and 4.5% for net indicated efficiency (at constant displaced volume). About two-thirds of this increase is realized by the compression ratio increase from 10 to 11.5. The standard deviations of these data sets are 1.8%.
Light-duty vehicles (LDVs) in the United States and elsewhere are required to meet increasingly challenging regulations on fuel economy and greenhouse gas (GHG) emissions as well as criteria pollutant emissions. New vehicle trends to improve efficiency include higher compression ratio, downsizing, turbocharging, downspeeding, and hybridization, each involving greater operation of spark-ignited (SI) engines under higher-load, knock-limited conditions. Higher octane ratings for regular-grade gasoline (with greater knock resistance) are an enabler for these technologies. This literature review discusses both fuel and engine factors affecting knock resistance and their contribution to higher engine efficiency and lower tailpipe CO2 emissions. Increasing compression ratios for future SI engines would be the primary response to a significant increase in fuel octane ratings. Existing LDVs would see more advanced spark timing and more efficient combustion phasing. Higher ethanol content is one available option for increasing the octane ratings of gasoline and would provide additional engine efficiency benefits for part and full load operation. An empirical calculation method is provided that allows estimation of expected vehicle efficiency, volumetric fuel economy, and CO2 emission benefits for future LDVs through higher compression ratios for different assumptions on fuel properties and engine types. Accurate "tank-to-wheel" estimates of this type are necessary for "well-to-wheel" analyses of increased gasoline octane ratings in the context of light duty vehicle transportation.
Ethanol has the potential to improve engine efficiency and reduce harmful emissions when used as fuel in a spark-ignited engine. Ethanol is mostly supplied in a splash-blended form with gasoline or in a pure form; however, this is not an optimal way of using ethanol because the use of ethanol leads to increased brake specific fuel consumption. To fully utilize the merits of ethanol, on-demand control of ethanol and gasoline is required so that the fuel-blending ratio can be altered according to the engine operating conditions. This study investigated the effect of ethanol port fuel injection and gasoline direct injection systems on engine combustion and emission characteristics under full load conditions. The experiment was conducted using two different compression ratios and various ethanol injection timings. Knock occurrence decreased as the ethanol injection timing was held while intake valves were open. Minor reductions in carbon monoxide, total hydrocarbon, and particulate emissions were observed under a compression ratio of 9.5, while the reduction in emissions became significant under a compression ratio of 13.3 as the amount of ethanol injection increased.
ExxonMobil, Corning and Toyota have collaborated on an Onboard Separation System (OBS) to improve gasoline engine efficiency and performance. OBS is a membrane based process that separates gasoline into higher and lower octane fractions, allowing optimal use of fuel components based on engine requirements. The novel polymer-ceramic composite monolith membrane has been demonstrated to be stable to E10 gasoline, while typically providing 20% yield of ~100 RON product when using RUL 92 RON gasoline. The OBS system makes use of wasted exhaust energy to effect the fuel separation and provides a simple and reliable means for managing the separated fuels that has been demonstrated using several generations of dual fuel test vehicles. Potential applications include downsizing to increase fuel economy by ~10% while maintaining performance, and with turbocharging to improve knock resistance.
This paper presents engine dynamometer testing and modeling analysis of ethanol compared to gasoline at part load conditions where the engine was not knock-limited with either fuel. The purpose of this work was to confirm the efficiency improvement for ethanol reported in published papers, and to quantify the components of the improvement. Testing comparing E85 to E0 gasoline was conducted in an alternating back-to-back manner with multiple data points for each fuel to establish high confidence in the measured results. Approximately 4% relative improvement in brake thermal efficiency (BTE) was measured at three speed-load points. Effects on BTE due to pumping work and emissions were quantified based on the measured engine data, and accounted for only a small portion of the difference. Approximately half of the improvement was accounted for by the fact that the heat of vaporization (HoV) of the fuel detracts from the heat release measured in the combustion bomb used in the determination of heating value, but does not detract from the heat released during combustion in the engine. Engine modeling indicated that the remaining difference in BTE is due to lower burned gas temperatures and consequently lower heat transfer losses. The lower temperatures are due to greater charge cooling and to lower adiabatic flame temperature. CO2 emissions at part load are reduced about 7% for ethanol compared to gasoline. Approximately 4% CO2 benefit is due to improved thermal efficiency, and about 3% is due to the increased hydrogen-to-carbon ratio (H/C) of ethanol.
Biofuels are acting as a renewable replacement
for petroleum fuels due to some environmental and economic
benefits. They are prepared by blending a major
portion of diesel fuel and a certain minor percentage of
bio-oils, which provides less greenhouse gas (GHG) compared
to pure diesel. Recently, bioethanol has been the
most widely used biofuel for transportation. Bioethanol
can be produced from different kinds of agricultural raw
materials classified into three categories: simple sugars,
starch, and lignocellulose. Use of bioethanol-blended
gasoline fuel for automobiles can significantly reduce
petroleum use and exhaust GHG emission. Bioethanol
from sugar cane, produced under the proper conditions,
is essentially a clean fuel and has several clear advantages
over petroleum-derived gasoline in reducing GHG emissions
and improving air quality in metropolitan areas.
However, there remains a compromise between GHG
emission and saving of fossil fuel energy by introducing
bioethanol either totally or as a blending component of
engine fuel. Thus, considering biofuel as a replenishable
energy source, the future pathway of energy management
could be planned
Ethanol offers significant potential for increasing the compression ratio of SI engines resulting from its high octane number and high latent heat of vaporization. A study was conducted to determine the knock limited compression ratio of ethanol gasoline blends to identify the potential for improved operating efficiency. To operate an SI engine in a flex fuel vehicle requires operating strategies that allow operation on a broad range of fuels from gasoline to E85. Since gasoline or low ethanol blend operation is inherently limited by knock at high loads, strategies must be identified which allow operation on these fuels with minimal fuel economy or power density tradeoffs. A single cylinder direct injection spark ignited engine with fully variable hydraulic valve actuation (HVA) is operated at WOT conditions to determine the knock limited compression ratio (CR) of ethanol fuel blends. The geometric compression ratio is varied by changing pistons, producing CR from 9.2 to 13.66. The effective CR is varied using an electro-hydraulic valvetrain that changed the effective trapped displacement using both Early Intake Valve Closing (EIVC) and Late Intake Valve Closing (LIVC). The EIVC and LIVC strategies result in effective CR being reduced while maintaining the geometric expansion ratio. It was found that at substantially similar engine conditions, increasing the ethanol content of the fuel results in higher engine efficiency and higher engine power. These can be partially attributed to a charge cooling effect and a higher heating valve of a stoichiometric mixture for ethanol blends (per unit mass of air). Additional thermodynamic effects on and a mole multiplier are also explored. It was also found that high CR can increase the efficiency of ethanol fuel blends, and as a result, the fuel economy penalty associated with the lower energy content of E85 can be reduced by about a third. Such operation necessitates that the engine be operated in a de-rated manner for gasoline, which is knock-prone at these high CR, in order to maintain compatibility. By using EIVC and LIVC strategies, good efficiency is maintained with gasoline, but power is reduced by about 34%.
In an effort to both increase engine efficiency and generate new, consistent, and reliable data useful for the development of engine concepts, a modern single-cylinder 4-valve spark-ignition research engine was used to determine the response of indicated engine efficiency to combustion phasing, relative air-fuel ratio, compression ratio, and load. Combustion modeling was then used to help explain the observed trends, and the limitations on achieving higher efficiency. This paper analyzes the logic behind such gains in efficiency and presents correlations of the experimental data. The results are helpful for examining the potential for more efficient engine designs, where high compression ratios can be used under lean or dilute regimes, at a variety of loads. Extensive data from this study, across a wide range of engine operating conditions, show that the well-known loss of Net Indicated Mean Effective Pressure (NIMEP; the ratio of net work per cycle to cylinder volume displaced per cycle), with spark retard varies with operating conditions, mostly from variations in burn durations. However, a combustion phasing parameter, here termed "combustion retard", which represents the shift of the crank angle for 50% mass fraction burned from the optimal angle, was found to correlate with high accuracy all the changes in indicated torque output. At the baseline compression ratio of 9.8:1, as the engine was operated under mid-load and increasing relative air-fuel ratio, the efficiency curve versus dilution showed two distinct regimes. Through the first regime, efficiency increased with dilution until it peaked at a certain relative air-fuel ratio (range 1.5 to 1.6). Beyond this peak efficiency ratio began a second regime characterized by a falling efficiency due to increasing combustion duration and variability. Modeling and data analysis were used to investigate the contributions of pumping losses, mixture composition (ratio of specific heats), heat loss, burn durations, and combustion variability to the overall efficiency trend. It was determined that the leveling off in efficiency at high air-fuel ratios is due to a lengthening of burn duration beyond a critical value (10-90% burn angle of 30 degrees). Increasing compression ratio increases flame speed, extending the air-fuel ratio for peak efficiency an additional 0.1 lambda. Increasing combustion variability only affects the downward slope in efficiency at high air/fuel ratios. Increasing load extends the peak efficiency to leaner conditions. Above a compression ratio of 9.8:1, relative mid-load net efficiency improvement is about 2.5% per unit compression ratio. Efficiency peaks at a compression ratio of about 15:1 with a maximum benefit of 6-7%. Efficiency improves more with compression ratio at high speeds and loads due to the reduced importance of heat loss. Wide-open throttle indicated torque at MBT spark timing behaves similarly to mid-load efficiency, with a maximum benefit of 8-9% at a 14:1 compression ratio. These data are particularly useful considering the limited available publications containing consistent compression ratio effect data for a wide range of operating conditions. Relative net efficiency improvement from increasing load is about 6% per bar net indicated mean effective pressure at mid-load. About 80% of the improvement is from reduced pumping losses and 20% is from heat loss becoming a smaller portion of the overall charge energy. Correlations of efficiency with load are also presented.
Companion empirical and analytical studies were conducted to assess the feasibility and constraints (hardware and combustion perspectives) associated with operating a Spark Ignition Direct-Injection (SIDI) engine on high ethanol and gasoline mixtures ranging from 0 to 85% by volume. Cold start, part and full-load performance aspects were explored. Analytical experiments were performed to correlate with the empirical data using a commercially available single dimensional engine simulation code. Under WOT operating conditions it was found that the engine's simulated output was overestimated with E85 fuel which was caused by the over prediction of volumetric efficiency. It was necessary to create a sub-routine to accurately model the impingement, vaporization, and heat transfer of fuel on the piston surface. Results could only be correlated after taking fuel impingement into account. Spray measurements were conducted including white light illumination and phase Doppler interferometery to study the differences in the spray shape, impingement, and the droplet formation regime between gasoline and E85 fuels. Efforts were taken to study the effects of temperature and back pressure on the spray. The results suggested that the spray properties were quite similar between the fuels, that the penetration lengths and droplet sizes of the fuels were comparable for like conditions, however E85 was more resistant to flash boiling effects for typical engine operating conditions. Selected empirical part-load optimization suggested efficiency improvements of 3-6% were possible over the optimized gasoline baseline. These gains were primarily due to a reduction in heat rejection and increased Exhaust Gas Residual (EGR) tolerance. These efficiency gains mildly offset the inherent energy density deficiency of ethanol based gasoline mixtures. Full-load empirical data suggested a potential for 13-15% increase in specific output with E85, as compared to a customer intent gasoline baseline fuel. These performance gains were enabled by the anti-knock qualities of the ethanol blends and an increase in volumetric and indicated efficiencies. It was also found that optimized full-load E85 operation was possible with injector hardware that was sized for gasoline (E00) operation. Ultimately, strategies were developed that enabled E85 operation at all operating conditions, as enabled by low smoke operation, improved knock resistance, increased charge cooling, and increased combustion stability. Cold startability tests with representative Class 3 E85 fuel were conducted at extreme ambient conditions to assess the cold start performance of the SIDI engine. It was found that a Low Pressure Start (LPS) operating strategy enabled engine starts at ambient conditions as cold as -20C, however, High Pressure Stratified Starts (HPSS) were necessary to meet colder startabilty requirements. Ultimately, a HPSS strategy improved startabilty and reduced enrichment requirements for E85.
This paper presents engine dynamometer testing and modeling analysis of ethanol compared to gasoline at part load conditions where the engine was not knock-limited with either fuel. The purpose of this work was to confirm the efficiency improvement for ethanol reported in published papers, and to quantify the components of the improvement. Testing comparing E85 to E0 gasoline was conducted in an alternating back-to-back manner with multiple data points for each fuel to establish high confidence in the measured results. Approximately 4% relative improvement in brake thermal efficiency (BTE) was measured at three speed-load points. Effects on BTE due to pumping work and emissions were quantified based on the measured engine data, and accounted for only a small portion of the difference. Approximately half of the improvement was accounted for by the fact that the heat of vaporization (HoV) of the fuel detracts from the heat release measured in the combustion bomb used in the determination of heating value, but does not detract from the heat released during combustion in the engine. Engine modeling indicated that the remaining difference in BTE is due to lower burned gas temperatures and consequently lower heat transfer losses. The lower temperatures are due to greater charge cooling and to lower adiabatic flame temperature. CO2 emissions at part load are reduced about 7% for ethanol compared to gasoline. Approximately 4% CO2 benefit is due to improved thermal efficiency, and about 3% is due to the increased hydrogen-to-carbon ratio (H/C) of ethanol.
The Energy Independence and Security Act of 2007 established a new Renewable Fuel Standard (RFS2) requiring increased biofuel use (through 2022) and greater fuel economy (through 2030) for the US light-duty vehicle (LDV) fleet. Ethanol from corn and cellulose is expected to supply most of the biofuel and be used in blends with gasoline. A model was developed to assess the potential impact of these mandates on the US LDV fleet. Sensitivity to assumptions regarding future diesel prevalence, fuel economy, ethanol supply, ethanol blending options, availability of flexible-fuel vehicles (FFVs), and extent of E85 use was assessed. With no E85 use, we estimate that the national-average ethanol blend level would need to rise from E5 in 2007 to approximately E10 in 2012 and E24 in 2022. Nearly all (97%) US gasoline LDVs were not designed to operate with blends greater than E10. FFVs are designed to use ethanol blends up to E85 but comprise only 3% of the fleet. To satisfy the RFS2 using E10 and E85 requires very large scale introduction of FFVs (tens of millions) in the next 10-20 years. The RFS2 has profound ramifications for LDV technology.
Ethanol and other high heat of vaporization (HoV) fuels result in substantial cooling of the fresh charge, especially in direct injection (DI) engines. The effect of charge cooling combined with the inherent high chemical octane of ethanol make it a very knock resistant fuel. Currently, the knock resistance of a fuel is characterized by the Research Octane Number (RON) and the Motor Octane Number (MON). However, the RON and MON tests use carburetion for fuel metering and thus likely do not replicate the effect of charge cooling for DI engines. The operating conditions of the RON and MON tests also do not replicate the very retarded combustion phasing encountered with modern boosted DI engines operating at low-speed high-load.
In this study, the knock resistance of a matrix of ethanol-gasoline blends was determined in a state-of-the-art single cylinder engine equipped with three separate fuel systems: upstream, pre-vaporized fuel injection (UFI); port fuel injection (PFI); and DI. Constant inlet temperature was held downstream of the injector for UFI and upstream of the injectors for PFI and DI. For each fuel, engine inlet pressure was swept at borderline knocking conditions at constant engine speed using each of the three fuel systems. This test method characterized each fuel's knocking behavior over a wide range of conditions, including those typical of boosted DI engines.
Comparison of UFI and DI results allowed the chemical octane effect on knock to be separated from the evaporative charge cooling effect. These effects were found to be of comparable importance for ethanol blends.
An outcome of the test method was the discovery of an interaction between combustion phasing and the sensitivity of a fuel's autoignition kinetics to temperature. For a given gasoline blendstock, increasing ethanol content significantly increased knock-limited performance with combustion phasing near the thermodynamic optimum, as expected. However, due to ethanol's high sensitivity, knock-limited performance improved to a much greater extent with increasing ethanol content as combustion phasing was retarded. This effect was further enhanced by charge cooling with DI. Increasing ethanol content also significantly increased the knock-limited performance before enrichment was required to control exhaust gas temperature.
The RON ratings of the fuels did not fully reflect the observed knock resistance of mid-to-high level ethanol blends (E20 and higher). K, the weighting factor for MON in the Octane Index, decreased with increasing combustion phasing retard and with increasing evaporative charge cooling, and increased with increasing inlet temperature and increasing compression ratio.
Ethanol provides a significant contribution to road transportation fuel in the US, Brazil, and elsewhere. Renewable fuels regulations in the US and EU imply that ethanol use will continue to increase in the near future. The high octane rating of ethanol could be used in a mid-level ethanol blend to increase the minimum octane number (Research Octane Number, RON) of regular-grade gasoline. Higher RON would enable greater thermal efficiency in future engines through higher compression ratio (CR) and/or more aggressive turbocharging and downsizing, and in current engines on the road today through more aggressive spark timing under some driving conditions. Such an approach would differ from the current practice of blending ethanol into a gasoline blendstock formulated with lower octane rating such that the net octane rating of the resulting final blend is unchanged from historical levels.
Energy flows and energy efficiencies in the operation of a modern automobile are expressed in terms of simple algebraic approximations. One purpose is to make a car's energy use and the potential for reducing it accessible to non-specialists with technical backgrounds. The overall energy use depends on two factors, vehicle load and powertrain efficiency. The former depends on speed and acceleration and key vehicle characteristics such as mass. The latter depends on heat-engine thermodynamic efficiency, and engine and transmission frictions. The analysis applies to todays automobiles. Numerical values of important parameters are given so that the reader can make his or her own estimates. Various technologies to reduce the energy consumption of automobiles are discussed.
Energy Independence and Security Act of
Energy Independence and Security Act of 2007, Public Law 110-140.
Leone Ford Motor Company P
- G Thomas
Thomas G. Leone
Ford Motor Company
P.O. Box 2053, MD 2629