Search Results

The development of surrogate mixtures that represent gasoline combustion behavior is reviewed. Combustion chemistry behavioral targets that a surrogate should accurately reproduce, particularly for emulating homogeneous charge compression ignition (HCCI) operation, are carefully identified. Both short and long term research needs to support development of more robust surrogate fuel compositions are described. Candidate component species are identified and the status of present chemical kinetic models for these components and their interactions are discussed. Recommendations are made for the initial components to be included in gasoline surrogates for near term development. Components that can be added to refine predictions and to include additional behavioral targets are identified as well. Thermodynamic, thermochemical and transport properties that require further investigation are discussed.

The influence of the addition of oxygenated hydrocarbons to diesel fuels has been studied, using a detailed chemical kinetic model. Resulting changes in ignition and soot precursor production have been examined. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether, dimethoxymethane and methyl butanoate were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 30-40 % by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

Laminar burning velocity (LBV) measurements are reported for promising high-performance fuels selected as drop-in transportation fuels to automotive grade gasoline as part of the United States Department of Energy’s Co-Optimization of Fuels and Engines Initiative (Co-Optima). LBV measurements were conducted for ethanol, methyl acetate, and 2-methylfuran with synthetic air (79.0 % N2 and 21.0 % O2 by volume) within a constant-volume spherical combustion rig. Mixture initial temperature was fixed at 428±4 K, with the corresponding initial pressure of 1.00±0.02 atm. Current LBV of ethanol is in good agreement with literature data. LBV of ethanol and 2-methylfuran showed similar values over the range of equivalence ratios, while methyl acetate exhibited an LBV significantly lower over the range of tested equivalence ratios. The maximum laminar burning velocity occurred at slightly richer equivalence ratio from the stoichiometric value for all fuels tested.