Real Fuels

The variability of the price of oil, the need for energy efficiency and pollution minimization has led to increasing interest in alternative fuels. These fuels are structurally and compositionally different than the conventional fuels presently used.  Past work on conventional fuels have established on an empirical basis that such differences can lead to drastic changes in the combustion properties of fuels as manifested in pollutant emissions and efficiencies. The differences between alternative fuels and conventional petroleum based fuels are larger It is important to have an information base before their introduction and thus assuring that they can be "drop in" replacements in existing combustion devices. 

Progress in the development of Computational Fluid Dynamics codes has led to the possibility of describing the quantitative details of reactive flows. They have applicability to combustion problems dealing with real fuels in real devices. The aim is a computationally based predictive tool that can replace expensive and uncertain physical testing. In order to make use of the computational tools a quantitative understanding of the basic physico-chemical phenomenon is necessary. 

The emphasis is on fundamental information on chemical and physical properties that can be used in any environments.  For the former, interest is focused on the quantitative details of the breakdown of the larger hydrocarbons that are components in real fuel mixtures. This is an area that has been neglected in the past. It is important for the present application since the reaction of the breakdown products with active species are responsible for many combustion phenomenon. A single pulse shock tube have been used to generate the large hydrocarbon radicals of interest and observing their branching ratio for decomposition. From this data and available information on related processes at lower temperatures and estimated thermodynamic properties, rate constant for unimolecular decomposition and isomerization are generated under all combustion conditions. Radicals containing up to eight carbon atoms have been studied. Data dealing with the effect methyl substitution have been obtained and is being analyzed. Such information have direct bearing on Fisher-Tropsch fuels. Work on oxygenated radicals (from biofuels) will be initiated in the near future. Work on oxidative decomposition have now been initiated. The principal physical property of interest is the diffusion coefficient. For the larger fuel molecules there is no data. CFD modeling led to the conclusion that they can have important effect on the simulation results. A series of experiments to test this hypothesis have been initiated and preliminary results have been obtained. Finally, existing data on these issues existing in the literature have been analyzed. A database of databases have been constructed. A consistent nomenclature have been developed and detailed comparisons between existing chemical kinetics databases on the same fuel can now be made. Practically all such databases have been on single component fuels. Due to the necessity of fitting global measurements, a mixtures database that is necessary for real fuels cannot be simply a conglomeration of such databases. In the present approach the mixing rules become transparent.