A team at Sandia National Laboratories has designed a five-component gasoline-like blend containing 40% vol of a mixture of 2-methyl furan and 2,5-dimethyl furan (representative of products of a viable pathway to make furans from bio-feedstock). Simulations show promising results when the resulting fuel is compared to regular E10 gasoline. Measurements show that the fuel has research octane number (RON) = 97.4 and octane sensitivity (S) = 13.6, improving the RON and S of E10 by 5.4 and 6.3 units, respectively, and suggesting that the new fuel blend is suitable for spark-ignition engines.

The researchers experimentally evaluated the new fuel blend in the low-temperature gasoline combustion engine at Sandia National Laboratories, and compared the results with those of E10. The fuel blend requires less intake heat than E10 to autoignite under premixed, naturally aspirated conditions, indicating that the blend operates under the ACI mode easier than regular gasoline. Both the new blend and E10 allow virtually the same maximum engine load under premixed, high-boost conditions. Finally, the new blend shows significantly higher φ-sensitivity than E10.

A paper on the study is published in the ACS journal Energy & Fuels.

The new study was a continuation of work led by Sandia postdoctoral appointee Dario Lopez-Pintor and presented at the 2019 SAE World Congress highlighting how low-temperature gasoline combustion can lead to substantial efficiency improvements to reduce fuel consumption by 30% compared to conventional gasoline engines, and the importance of φ-sensitivity for making this type of combustion work well.

Lopez-Pintor was recognized for his work at the 2019 SAE World Congress, receiving an SAE Excellence in Oral Presentation Award for his paper, “Phi-Sensitivity for LTGC Engines: Understanding the Fundamentals and Tailoring Fuel Blends to Maximize This Property.”

The work was funded by Co-Optima, an R&D collaboration between DOE, nine national laboratories, several universities and industry organizations.

Background. High-performance renewable fuels (HPFs) are an alternative to conventional petroleum fuels that could greatly reduce the carbon footprint of internal combustion engines. The combination of high-HPF-content fuels with advanced engine technologies such as advanced compression ignition (ACI) that have been demonstrated to provide efficiencies well above those of diesel engines is a promising pathway for substantial reductions in CO₂ with low criteria emissions.

One of the key fuel properties for the operation of ACI engines is φ-sensitivity—a key fuel property that represents how the autoignition reactivity of the fuel varies with the fuel/air equivalence ratio. A fuel is φ-sensitive if its autoignition reactivity varies with the fuel/air equivalence ratio (φ).

Regular gasoline is not very φ-sensitive under naturally aspirated conditions, meaning that intake boosting is required to take advantage of this property. Thus, there is strong motivation to design HPF fuel blends that improve φ-sensitivity at lower pressures and simultaneously increase the research octane number (RON) and octane sensitivity (S) to make them improved fuels suitable for both ACI and spark-ignition engines.

In the 2019 work, Lopez-Pintor; John Dec, Senior Scientist and principal investigator of the low-temperature gasoline combustion laboratory in Sandia’s Combustion Research Facility; and former Sandia postdoctoral appointee Gerald Gentz applied a detailed mechanism using CHEMKIN to understand the chemistry responsible for φ-sensitivity.

They also explored the potential of designing fuel blends that increase the φ-sensitivity compared to E10 while maintaining high RON and octane-sensitivity, and found that higher φ-sensitivity and higher RON than E10 could be reached with a 5-component blend that meets US. regulations. The fuel mixture was composed of a combination of 1-hexene, n-pentane, iso-octane, p-xylene and iso-butanol (which was recently approved for gasoline in the US). That 2019 study showed that it is possible to have both high φ-sensitivity and high RON with high octane-sensitivity.

Resources

• Dario Lopez-Pintor and John E. Dec (2021) “Experimental Evaluation of a Gasoline-like Fuel Blend with High Renewable Content to Simultaneously Increase φ-Sensitivity, RON, and Octane Sensitivity” Energy & Fuels doi: 10.1021/acs.energyfuels.1c01979

• Lopez Pintor, D., Dec, J., and Gentz, G., “Φ-Sensitivity for LTGC Engines: Understanding the Fundamentals and Tailoring Fuel Blends to Maximize This Property,” SAE Technical Paper 2019-01-0961, 2019, doi: 10.4271/2019-01-0961