Electrostatic dispersion of drops of sprayed liquid fuel has been proposed as a technique for reducing the amount of soot formed during burning of the fuel. It is necessary to disperse fuel drops in order to reduce local concentrations of fuel-rich vapors, because such concentrations favor the nucleation of soot. The present technique can be implemented by use of a previously developed device called an "electrostatic triode"; this device puts like electrostatic charges onto sprayed fuel drops to generate dispersion of the drops.
Another technique for reducing the formation of soot is mechanical dispersion through utilization of turbulence. The effectiveness of electrostatic versus mechanical dispersion for reducing the formation of soot has been investigated in a theoretical and computational study. In the study, the mechanical and thermodynamic interactions between fuel drops and the surrounding gases were simulated numerically by use of a mathematical model similar to the models used in previous studies of sprayed liquid fuels that have been performed by the same innovators and summarized in a number of articles in NASA Tech Briefs. The model includes, among other conservation equations, equations for the momenta of the drops. The electrostatic forces were included in these equations for those drops that were considered to be charged. The calculations for the charged drops were stopped at the Rayleigh limit; that is, secondary atomization was not modeled.
The results of the numerical simulations were interpreted as signifying that electrostatic dispersion would be superior to mechanical dispersion for reducing the nucleation of soot; this finding gave rise to speculation that perhaps a combination of electrostatic and mechanical dispersion might be even more effective. However, further numerical simulation revealed that for the purpose of reducing the formation of soot, the combination electrostatic and mechanical dispersion would not offer a significant advantage over electrostatic dispersion alone.
This work was done by Josette Bellan and Kenneth Harstad of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Physical Sciences category, or circle no. 187on the TSP Order Card in this issue to receive a copy by mail ($5 charge). Refer to NPO-20219