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High Octane Fuels

[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]

ExxonMobil, Corning and Toyota develop onboard membrane system to separate gasoline into octane fractions to optimize engine efficiency and performance

April 10, 2014

ExxonMobil, Corning and Toyota have collaborated to develop an Onboard Separation System (OBS) to optimize gasoline engine efficiency and performance. OBS is a membrane-based process that separates gasoline into higher and lower octane fractions—essentially creating a dual fuel system from a single base fuel—allowing optimal use of fuel components based on engine requirements. The system, say the researchers, offers the potential to exploit most of the benefits of operating on premium high octane fuel while using less expensive regular grade more effectively.

In a paper on the OBS presented at the SAE 2014 World Congress, the researchers suggested that potential applications include downsizing to increase fuel economy by ∼10% while maintaining performance, and or using OBS with turbocharging to improve performance and knock resistance.

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Study finds butanol-gasoline blends effective to control soot from CI engines under Low Temperature Combustion

January 31, 2014

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(Left) Thermal efficiency and (right) soot from different gasoline-butanol blends at different EGR rates. Yang et al. Click to enlarge.

A study by a team at Tianjin University found that the addition of n-butanol to gasoline for use in a compression ignition engine (CI) under Low Temperature Combustion (LTC) conditions has a significant effect on soot reduction. The peak soot value of a 30% butanol blend (B30) was 85% lower than that of pure gasoline; the EGR rate that corresponds to the peak value of soot is also decreased with the higher n-butanol fraction. Their study is published in the journal Fuel.

Partially Premixed Combustion involving the injection of gasoline fuel into CI engines is being explored by other researchers as a means to reducing simultaneously NOxand soot emissions. High octane fuels such as gasoline are preferred for high-efficiency and clean combustion at high engine loads, the Tianjin researchers note.

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Global Bioenergies to collaborate with Audi on development of drop-in bio-isooctane

January 21, 2014

Global Bioenergies (GBE), a leading developer of one-step fermentation processes for the direct and cost-efficient transformation of renewable resources into light olefins (earlier post), has signed a collaboration agreement with Audi on the development of bio-isooctane—a high-performance drop-in biofuel for gasoline engines—derived from bio-isobutene. In 2011, GBE had announced an agreement “with a major German car manufacturer” regarding an undisclosed application of GEB’s technology. (Earlier post.)

Under the agreement, GBE will supply Audi with isooctane derived from isobutene produced at its new pre-commercial pilot system at the Fraunhofer CBP in Leuna. (Earlier post.) During the two-year collaboration, this agreement also foresees the possibility for Audi to acquire shares of Global Bioenergies corresponding to less than 2% of its capital.

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Oak Ridge Lab study finds E30 blend and EGR can deliver significant efficiency improvements in optimized SI engines

January 17, 2014


Estimated gasoline equivalent MPG of each fuel and combustion strategy in a midsize sedan at a 65 mph steady cruise condition, referenced to chassis dyno data of the production GM Ecotec SI engine and vehicle. CDC = conventional diesel combustion. Credit: ACS, Splitter and Szybist (2014a). Click to enlarge.

Researchers at Oak Ridge National Laboratory’s National Transportation Research Center (NTRC) report that an E30 (30% ethanol) mid-level ethanol blend shows promise as a means for significant improvement in vehicle efficiency in optimized spark-ignited (SI) engines. Results of the study by Derek Splitter and Jim Szybist suggest that it could be possible to implement a 40% downsize + downspeed configuration (1.2 L engine) into a representative midsize sedan using this combination of optimized engine and mid-level alcohol blend.

As an example, for a midsize sedan at a 65 mph (105 km/h) cruise, estimated fuel efficiency of 43.9 mpg (5.4 l/100 km) with engine-out CO2 of 102 g/km could be achieved with similar reserve power to a 2.0 L engine fueled with regular gasoline (38.6 mpg/6.1 l/100km, engine out CO2 of 135 g/km). The 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.

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Researchers explore ethanol-diesel dual-fuel combustion for reduction in engine-out emissions

November 14, 2013

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Effect of ethanol energy fraction and PFI position on CO, NOx, HC, and opacity emissions. Credit: ACS, Padala et al. Click to enlarge.

Researchers at the University of New South Wales (Australia) have demonstrated the potential for ethanol use in diesel engines with dual-fuel combustion, in which ethanol is injected into the intake manifold and diesel is directly injected into the engine cylinder. A paper on their work is published in the ACS journal Energy & Fuels.

The goal of such an approach is effectively to address some of the drawbacks of conventional diesel combustion, such as higher in-cylinder soot formation associated with locally rich mixtures and high flame temperatures and engine-out emissions of NOx.

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Omnitek selects DD 12.7L Series 60 and Cat C15 engine models for diesel-to-gas conversion project at Port of Seattle

November 04, 2013

Omnitek Engineering Corporation has selected the 12.7 L Detroit Diesel Series 60 and the Caterpillar C15 engine models for the beginning of the second phase of a Puget Sound Clean Air Agency pilot project, which includes the development of diesel-to-natural gas engine conversion kits for these engine models and obtaining Environmental Protection Agency (EPA) approval.

Omnitek’s diesel-to-natural gas engine conversion system was selected as the best technology under the competitive grant process for the agency’s “Piloting Engine Upgrade Technologies in the Freight Mobility Sector” project. (Earlier post.)

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Advanced Biofuels USA introduces “E30 Capable” high-octane fuels concept in EPA Tier 3 comments

July 02, 2013

Biofuel advocacy group Advanced Biofuels introduced the concept of “E30 Capable” vehicles as part of its comments to the the US Environmental Protection Agency’s (EPA’s) recently proposed Tier 3 motor vehicle fuel and emission rulemaking. (Earlier post.)

As part of the Tier 3 requirements, EPA proposes allowing vehicle manufacturers to request approval for an alternative certification fuel—such as a high-octane 30% ethanol by volume (E30) blend—for vehicles they might design or optimize for use on such a fuel. (Earlier post.) Advanced Biofuels suggests that “E30 Capable” vehicles can serve a practical key to transitioning to higher percentage blends of affordable renewable transportation fuels. Elements of the proposal include:

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New MOF could enable more efficient and cost-effective production of high octane gasoline

May 24, 2013

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The new MOF contains triangular channels running through the material. The walls of these channels trap the lower-octane components while allowing the higher-octane molecules to pass through, potentially providing a more efficient and cost effective way to refine high-octane gasoline. Credit: Science/AAAS. Click to enlarge.

An international team of researchers has developed a new metal-organic framework (MOF) that might provide a significantly improved method for separating hexane isomers in gasoline according to their degree of branching. A paper on the work is published in the journal Science.

Created in the laboratory of Jeffrey Long, professor of chemistry at the University of California, Berkeley, the MOF features triangular channels that selectively trap only the lower-octane hexane isomers based on their shape, separating them easily from the higher-octane molecules in a way that could prove far less expensive than the industry’s current method for producing high-octane fuel. The Long laboratory and UC Berkeley have applied for a patent on the MOF Fe2(bdp)3. (BDP2– = 1,4-benzenedipyrazolate)

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Researchers propose evaluating alt fuel efficiency based on energy rather than volume; impact of ethanol on vehicle efficiency and GHGs

May 17, 2013

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Relative changes in vehicle energy efficiency (VEE) (km/MJ) on ethanol/gasoline blends over those on gasoline for different blending levels. Credit: ACS, Yan et al. Click to enlarge.

In a policy analysis in the ACS journal Environmental Science & Technology, researchers from the Universities of Cambridge, Exeter and Oxford argue that, due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume.

With that as a premise, they go on to show that the efficiency of existing vehicles can be both positively and negatively affected by ethanol content, ranging from −15% to +24%. As a result, they conclude, uncertainties in the net greenhouse gas (GHG) effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated. Standard deviations increase by >10% and >200% when used in high and low blends, respectively.

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Ford / AVL study concludes mid-level ethanol blend attractive as a long-term future fuel for use in optimized engines in US

April 19, 2013

A study by a team from Ford Motor Company and AVL has concluded that a mid-level ethanol blend—greater than E20 but less than E40—appears to be attractive as a long-term future fuel for the US for use in engines optimized for the higher octane blend. The team presented a paper on their work at the 2013 SAE World Congress in Detroit. Ford engineers also presented two other papers evaluating the effects of low to mid-level ethanol blends in spark-ignited engines at the conference.

In the face of increased regulatory stringency (e.g., US CAFE, California LEV 3 and pending US Tier 3), the combustion engine community is gearing up for an intensified push to deliver higher efficiency engines with lower fuel consumption and emissions. One of the many emerging possible technology pathways to achieve those goals is the use of a future high-octane fuel in optimized, higher-compression-ratio engines. (Earlier post.) The study by the Ford / AVL team provides an overview of the effects of such a future ethanol-gasoline blend in such an engine.

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