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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.]

Team from GM, Ford, FCA reviews how to calculate engine efficiency benefits of high octane fuels

August 25, 2015

A team of engineers from GM Powertrain, Ford and FCA have published a detailed review of how to estimate the engine efficiency benefits of higher octane fuel—e.g., fuel with higher ethanol content—for part- and full-load operation for different engine types and fuel assumptions. Their paper is published in the ACS journal Environmental Science & Technology.

Engine compression ratio plays a fundamental role in engine efficiency; a higher compression ratio improves efficiency, but also causes higher temperatures and pressures of the unburned air-fuel mixture which can lead to knock at high loads. Compression ratio is thus limited to avoid knock. The compression ratio selected for a particular engine depends, the authors note, on the expected duty cycle and fuel octane. A higher compression ratio can be used if an engine will operate primarily at light loads, such that degraded efficiency at high loads is more than offset by improved efficiency at light loads.

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UC Riverside team characterizes impact on PM of fuels with varying aromatics and octane rating; benefit of increased ethanol fraction

August 18, 2015

Researchers at the University of California-Riverside have characterized the effect of decreased aromatic content fuels combusted in advanced vehicle technologies on emissions of particulate matter (PM). In a paper in the ACS journal Environmental Science & Technology, they present the changes in PM emissions for different fuels, engine technologies, and operating conditions. Among their findings is that an increased ethanol fraction in gasoline could help reduce PM mass and black carbon (BC) from gasoline direct injection engines (GDI).

Typical commercial gasoline comprises varying concentrations of aromatic hydrocarbons and octane ratings; the impacts on PM such as black carbon (BC) and water-soluble and insoluble particle compositions of these differences are not well-defined. The UC Riverside study tested seven 2012 model year vehicles, including one port fuel injection (PFI) configured hybrid vehicle; one PFI vehicle; and six GDI vehicles.

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Tsinghua studies on alcohol-gasoline dual fuel engines show fuel efficiency and particle number benefits

August 10, 2015

Researchers at Tsinghua University in China are studying the effects of Dual-Fuel Spark Ignition (DFSI) combustion fueled with different alcohols and gasoline. In one paper, published in the journal Fuel, they investigated the use of alcohols–gasoline DFSI Combustion for knock suppression and high fuel efficiency using a gasoline engine with high compression ratio.

In a second paper, also published in Fuel, they systematically compared the stoichiometric alcohol–gasoline and gasoline–alcohol DFSI combustion for engine particle number (PN) reduction (and fuel economy improvement), also using a high compression ratio gasoline engine.

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NREL examines potential of blending ethanol with condensate for flex-fuels and high-octane mid-level blends

July 21, 2015

A team at the National Renewable Energy Laboratory (NREL), with a colleague at EcoEngineering, has explored the potential of blending ethanol with natural gasoline (condensate) to produce flex-fuels (ASTM D5798-13a) and high-octane, mid-level ethanol blends (MLEBs). A paper on their work is published in the ACS journal Energy & Fuels.

The study addresses two current market conditions: first, more ethanol is produced domestically than can legally be blended in E10 (the ethanol blend wall). Second, as a result of recent increases in crude oil and natural gas production in the US, condensate—a component of natural gas liquids (NGLs) found in rich gas—is produced in abundance and could potentially serve as a lower-cost blendstock. Current US production of condensate is estimated at 1.5 × 108 m3 annually compared to 9.7 × 107 m3 annually 10 years ago.

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Argonne, Ford and FCA partnering to study natural gas and gasoline blending for 50% cut in gasoline, 10% boost in efficiency and power density

July 14, 2015

Researchers at the US Department of Energy’s (DOE) Argonne National Laboratory are partnering with Ford Motor Company and FCA US LLC in pre-competitive research to study blending natural gas and gasoline using natural gas direct injection to enable more efficient engines. The project is a cooperative research and development agreement (CRADA) resulting from the 2014 DOE Vehicle Technologies Office (VTO) Funding Opportunity Announcement (FOA).

The project’s objective is to understand potential benefits and demonstrate targeted blending of gasoline and natural gas in an engine that uses half as much gasoline and shows a 10% increase in overall efficiency and a 10% improvement in power density.

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Promising results from Mercedes-Benz fleet test of Clariant high-octane cellulosic E20

September 23, 2014

Clariant, Haltermann and Mercedes-Benz have fleet-tested high-octane sunliquid 20 fuel—containing 20% cellulosic ethanol produced from straw—since January. (Earlier post.) The test found that the use of sunliquid 20 improves engine efficiency—more than compensating for its 4% lower energy content compared to E10. For drivers, this means with sunliquid 20, CO2emissions are reduced while consumption remains the same.

Use of sunliquid 20 also resulted in a 50% improvement in particle emissions count in contrast to the EU 5 reference fuel. The cellulosic ethanol in sunliquid 20 demonstrates greenhouse gas emission savings of up to 95% across the entire value chain (well-to-wheel perspective) without competing with food production or agricultural acreage.

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Study finds US refining sector could produce higher octane E20 and E30 at modest additional cost; enabling more efficient engines

September 18, 2014

A new study concludes that using ethanol can be a cost-effective approach to increasing the octane rating of the US gasoline pool. Source: ACS, Hirshfeld et al. Click to enlarge.

A number of studies recently have pointed out that increasing the octane rating of the US gasoline pool (currently ∼93 Research Octane Number (RON)) would enable higher engine efficiency for light-duty vehicles through reducing engine knock constraints, thereby enabling the design of new spark-ignition engines with higher compression ratios and boost levels. (Earlier post.) Such a move would also have significant implications for refineries in the US refining sector, whether the higher octane was achieved via more severe refining operations, increased use of ethanol, or both.

A linear programming analysis of US refining sector by a team from MathPro Inc., Ford, GM and Chrysler has found that, by increasing the volume of ethanol, the refining sector could produce hydrocarbon blendstocks for oxygenate blending (BOBs) yielding finished E20 and E30 gasolines with higher octane ratings at modest additional refining cost (ARC): e.g., ∼1¢/gal for 95-RON E20 or 97-RON E30; 3–5¢/gal for 95-RON E10, 98-RON E20, or 100-RON E30; and 96-RON E10, 99-RON E20, or 101-RON E30 gasoline pools at approximately 10¢/gal.

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