Experimental Evaluation of a Gasoline-like Fuel Blend with High Renewable Content to Simultaneously Increase φ-Sensitivity, RON, and Octane Sensitivity
Darío López Pintor, John E. Dec
Abstract
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. However, 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 this study, a holistic methodology was used to design a five-component gasoline-like blend (termed CB#2) that contains 40%vol of a mixture of 2-methyl furan and 2,5-dimethyl furan (which is representative of products of a viable pathway to make furans from bio-feedstock). Simulations show promising results when CB#2 is compared to regular E10 gasoline (RD5-87). Measurements show that CB#2 has RON = 97.4 and S = 13.6, improving the RON and S of RD5-87 by 5.4 and 6.3 units, respectively, and suggesting that CB#2 is suitable for spark-ignition engines. Fuel blend CB#2 has been experimentally evaluated in the low-temperature gasoline combustion engine at Sandia National Laboratories, and the results are compared with those of RD5-87. Fuel blend CB#2 requires less intake heat than RD5-87 to autoignite under premixed, naturally aspirated conditions, indicating that CB#2 operates under the ACI mode easier than regular gasoline. Both CB#2 and RD5-87 allow virtually the same maximum engine load under premixed, high-boost conditions. Finally, CB#2 shows significantly higher φ-sensitivity than RD5-87.