Recent fuel developments have resulted in a number of aqueous fuel emulsions comprised essentially of a carbon based fuel, water, and various additives such as lubricants, emulsifiers, surfactants, corrosion inhibitors, cetane improvers, and the like. These aqueous fuel emulsions may play a key role in finding a cost-effective way for internal combustion engines including, but not limited to, compression ignition engines (i.e. diesel engines) to achieve the reduction in emissions below the mandated levels without significant modifications to the engines, fuel systems, or existing fuel delivery infrastructure.
Advantageously, aqueous fuel emulsions tend to reduce or inhibit the formation of nitrogen oxides (NOx) and particulates (i.e. combination of soot and hydrocarbons) by altering the way the fuel is burned in the engine. Specifically, the fuel emulsions are burned at somewhat lower temperatures than a conventional fuels due to the presence of water. This, coupled with the realization that at higher peak combustion temperatures, more NOx are typically produced in the engine exhaust, one can readily understand the advantage of using aqueous fuel emulsions.
A major concern of aqueous fuel emulsions or water blend fuels, however, is the stability of the fuel. As is well known in the art, the constituent parts of such aqueous fuel emulsions have a tendency to separate over time. Blending of the fuel emulsions in a manner to achieve long-term stability is essential if such fuels are to be commercially successful. The problems associated with fuel emulsion separation are very severe inasmuch as most engine operating characteristics are adjusted for a prescribed fuel composition. Where the fuel emulsion composition has changed due to ingredient separation, the engine performance is markedly diminished.
Several related art references have disclosed various devices or techniques for producing or blending a fuel emulsion for internal combustion engines. For example, U.S. Pat. No. 5,535,708 (Valentine) discloses a process for forming an emulsion of an aqueous urea solution in diesel fuel and combusting the same for the purposes of reducing NOx emissions from diesel engines. See also U.S. Pat. No. 4,938,606 (Kunz) discloses an apparatus for producing an emulsion for internal combustion engines that employs an oil line, a water line, a dosing apparatus and various mixing and storage chambers. Another related art process and system for blending a fuel emulsion is disclosed in U.S. Pat. No. 5,298,230 (Argabright) which discloses a specialized process for blending a fuel emulsification system useful for the reduction of NOx in a gas turbine.
The present invention addresses the aforementioned problems associated with separation of aqueous fuel emulsions by providing a blending system and method that enhances the long term stability of such emulsions.