High Octane Fuel

The Energy Independence and Security Act (EISA) of 2007 is an omnibus energy policy law designed to move the United States toward greater energy security and independence. A key provision of EISA is the Renewable Fuel Standard (RFS), which requires the nation to use 36 billion gallons per year (BGPY) of renewable fuel in vehicles by 2022.* Ethanol is the most widely used renewable fuel, and increasing the allowable ethanol content from 10% to 15% is expected to push renewable fuel consumption to as much as 21 BGPY. Therefore, a large portion of the 36 billion gallon requirement can be met by increasing the ethanol content in gasoline to 15%. However, raising the ethanol content to 15%, by itself, will still not fully meet the RSF requirement, and concerns have been raised that this increase in ethanol may not be entirely compatible with current and legacy materials used in standard gasoline fueling systems. In the summer of 2008, the U.S. Department of Energy (DOE) recognized the need to assess the impact of intermediate blends of ethanol on the fueling infrastructure, specifically those systems located at the fueling station. A short time later (March 2009), Growth Energy (a coalition of ethanol producers and supporters) requested a waiver from the U.S. Environmental Protection Agency (EPA) to allow the use of 15% ethanol in gasoline.†

The compatibility of elastomer materials used in fuel storage and dispensing applications was determined for an off-highway diesel
fuel and a blend containing 20% bio-oil (Bio20) derived from a fast pyrolysis process. (This fuel blend is not to be confused with B20,
which is a blend of diesel fuel with 20% biodiesel.) The elastomer types evaluated in this study included fluorocarbon, fluorosilicone,
acrylonitrile rubber (NBR), styrene butadiene rubber (SBR), polyurethane, neoprene, and silicone. All of these elastomer types are
used in sealing applications, but some, like the nitrile rubbers are also common hose materials. The elastomer specimens were exposed
to the two fuel types for 4 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at
60°C and then remeasured. A solubility analysis was performed to better understand the performance of plastic materials in fuel blends
composed of bio-oil and diesel.

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.

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.

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.

Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high
latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and
power can be increased through higher compression ratio, direct fuel injection, higher levels of boost, and a reduced need
for enrichment to mitigate knock or protect the engine and aftertreatment system from overheating.
The ASTM D5798 specification for high level ethanol blends, commonly called “E85,” underwent a major revision in
2011. The minimum ethanol content was revised downward from 68 vol% to 51 vol%, which combined with the use of
low octane blending streams such as natural gasoline introduces the possibility of a lower octane “E85” fuel. While this
fuel is suitable for current “ethanol tolerant” flex fuel vehicles, this study experimentally examines whether engines can
still be aggressively optimized for the resultant fuel from the revised ASTM D5798 specification.
The performance of six ethanol fuel blends, ranging from 51-85% ethanol, is compared to a premium-grade
certification gasoline (UTG-96) in a single-cylinder direct-injection (DI) engine with a compression ratio of 12.87:1 at
knock-prone engine conditions. UTG-96 (RON = 96.1), light straight run gasoline (LSRG, RON = 63.6), and n-heptane
(RON = 0) are used as the hydrocarbon blending streams for the ethanol-containing fuels in an effort to establish a broad
range of knock resistance for high ethanol fuels.
Results show that nearly all ethanol-containing fuels are more resistant to engine knock than UTG-96 (the only
exception being the ethanol blend with 49% n-heptane). This allows ethanol blends made with low octane number
hydrocarbons to be operated at significantly more advanced combustion phasing for higher efficiency, as well as at higher
engine loads.
While experimental results show that the octane number of the hydrocarbon blend stock does impact engine
performance, there remains a significant opportunity for engine optimization when considering even the lowest octane
fuels that are in compliance with the current revision of ASTM D5798 compared to premium-grade gasoline.

Spark-ignition (SI) engines with direct-injection (DI) fueling can improve fuel economy and vehicle power beyond
that of port fuel injection (PFI). Despite this distinct advantage, DI fueling often increases particle number emissions, such that SI
exhaust may be subject to future particle emissions regulations. In this study, ethanol blends and engine operating strategy are
evaluated for their effectiveness in reducing particle emissions in DI engines. The investigated fuels include a baseline emissions
certification gasoline, a blend of 20 vol % ethanol with gasoline (E20), and a blend of 85 vol % ethanol with gasoline (E85). The
operating strategies investigated reflect the versatility of emerging cam-based variable valve actuation technology capable of
unthrottled operation with either early or late intake valve closing (EIVC or LIVC). Particle emissions are characterized in this study
by the particle number size distribution as measured with a scanning mobility particle sizer (SMPS) and by the filter smoke number
(FSN). Particle emissions for PFI fueling are very low and comparable for all fuels and breathing conditions.When DI fueling is used
for gasoline and E20, the particle number emissions are increased by 1
2 orders of magnitude compared to PFI fueling, depending
upon the fuel injection timing. In contrast, when DI fueling is used with E85, the particle number emissions remain low and
comparable to PFI fueling. Thus, by using E85, the efficiency and power advantages of DI fueling can be gained without generating
the increase in particle emissions observed with gasoline and E20.

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 and other high-load conditions to determine the knock
limited compression ratio (CR) of ethanol fuel blends. The
geometric CR is varied by changing pistons, producing CR
from 9.2 to 12.87. 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.
 

The Energy Independence and Security Act (EISA) of 2007 is an omnibus energy policy law designed to
move the United States toward greater energy security and independence. A key provision of EISA is the
Renewable Fuel Standard (RFS) which requires the nation to use 36 billion gallons per year (BGPY) of
renewable fuel in vehicles by 2022.1 Ethanol is the most widely used renewable fuel, and increasing the
allowable ethanol content from 10% to 15% is expected to push renewable fuel consumption to 21BGPY.
Therefore, a large portion of 36 billion gallon goal can be met by increasing the ethanol in gasoline to
15%. However, concerns were raised that this increase in ethanol may negatively impact the compatibility
of materials and components used in standard gasoline fueling hardware. In the summer of 2008, the U.S.
Department of Energy recognized the need to assess the impact of intermediate blends of ethanol on
the fueling infrastructure, specifically those systems located at the fueling station. A short time later
(March 2009), Growth Energy (a coalition of ethanol producers and supporters) requested a waiver from
the Environmental Protection Agency (EPA) to allow the use of 15% ethanol in gasoline.2
The first phase of this research focused on intermediate ethanol levels (10 to 25%), and the materials
evaluated at that time were limited to elastomers, metals and sealants. The results from the Phase 1effort
were published in March of 2011.3 At the conclusion of the Phase 1 activity, ORNL expanded the
material selection to include plastics, which included types typically found in fueling infrastructure
systems, including piping and underground storage tanks. Initially, the test fuels were those representing
gasoline containing 0 to 25% levels of ethanol, but later, test fuels representing the high ethanol blends,
E50 and E85, were added for completeness. Since elastomers and metals had not been evaluated in these
high ethanol blends, they were included along with the plastic materials.
The results contained within this report are divided into three sections according to material type. In the
first section, the compatibility results are presented for plastic materials exposed to gasoline test fuels
containing low and high levels of ethanol. The remaining two sections emphasize the compatibility of
elastomers and metals with gasoline test fuels containing high ethanol concentrations. Additional data
obtained from the earlier study on these materials are included for additional interpretation and summary.

The Energy Independence and Security Act (EISA) of 2007 was an omnibus energy policy law designed to move the United States toward greater energy security and independence.1 A key provision of EISA modified the Renewable Fuel Standard (RFS) which requires the nation to increase the volume of renewable fuel blended into transportation fuels from 7.5 billion gallons by 2012 to 36 billion gallons by 2022. Ethanol is the most widely used renewable fuel, and increasing the ethanol content in gasoline to 15% offers a means of getting significantly closer to the 36 billion gallon goal. In March 2009, Growth Energy (a coalition of ethanol producers and supporters) requested a waiver from the United States Environmental Protection Agency (EPA) to allow the use of 15% ethanol in gasoline.2 In response the US EPA granted two partial waivers that allow (but do not require) E15 in 2001 and newer light-duty vehicles. Prior to the waiver being granted, uncertainties arose as to whether the additional fuel ethanol (from 10% to 15%), would cause an increase in leaking of underground storage tank (UST) systems, which include not only the tank but also the piping and connecting hardware.