Microemulsion fuels provide a method for increasing the use of byproduct and biomass materials, including alcohols, in diesel fuels. The ability to replace 50% of diesel fuel with byproduct and biomass-derived materials microemulsion fuels could significantly decrease petroleum consumption. However, it is likely that the low particulate and NO{sub x} emissions characteristic of these fuels will drive the adoption of this technology. This report is concerned with the development of a series of short experiments to determine the fuel composition changes required to support development of microemulsion fuels which have combustion properties acceptable to the public and adequate to support widespread use in current diesel engines. The goal is delineation of microemulsion diesel fuel compositions which have acceptable compression ignition and emissions properties and which permit the replacement of one-third to one-half of current diesel fuel petroleum. A review of the literature on cetane enhancers for conventional and alternative diesel fuels was performed and a small number of enhancers likely to be effective with high-alcohol fuels selected. Based on linear regression analysis of emissions from a passenger diesel engine using alcohol and aqueous microemulsion fuels, correlation between microemulsion solution structure as determined by small-angle neutron scattering and actual NO{sub x}more » and particulate emissions was determined. The analysis indicates that solution structure and microemulsion composition play major roles in emissions modification. 223 refs., 5 figs., 9 tabs.« less

Correlating microemulsion fuel composition, structure, and combustion properties

Emissions and fuel economy of a large volume prechamber, fuel injected, stratified charge engine with gasoline and a gasoline/20% methanol blend are measured. The engine is a modified CFR cetane test engine operating with MBT spark timing and 8. 4:1 compression ratio. The effect of both prechamber and main chamber mixture ratio on engine operation and emissions is investigated. Lowest overall emissions are achieved simultaneously with low fuel consumption at a prechamber equivalence ratio of 1. 10. The stratified charge engine when operated on the gasoline/methanol blend shows significant improvement over gasoline in NO emissions but also with higher exhaust CO and HC. Fuel economy is not significantly different for the two fuels so long as the prechamber is not overly rich. The interpretation of the HC emissions measurements is aided by a study of quenching distances of methanol and methanol blends. A constant volume, flanged electrode test bomb is used to measure quenching distances of reactive gas mixtures. Experiments are performed with methane, methanol, iso-octane and iso-octane/methanol blends over a range of equivalence ratios for several mixture initial temperatures and pressures. The fuel blends are found to have larger quenching distances than either pure fuel which is consistent with the observation of slightly higher HC emissions in the engine study when using the methanol blend

N Ishikawa

Papers

Combustion of methanol and methanol blends in a stratified charge engine