Electrostatic Dispersion and Evaporation of Dense and Dilute Clusters of Drops of High-energy Fuel for Soot Control1

The high-energy-density (HED) fuels developed under U.S. Navy sponsorship as a replacement for conventional liquid fuels in its missile propulsion systems have the drawback of high soot propensity: this makes missiles visible and thus strategically unacceptable. Experimental evidence of heavy sooting from such potential fuels has been presented by Law[l]. Soot propensity is defined here as the ability of a fuel to form soot precursors through nucleation react ions; it does not refer to soot growth, or soot production which includes the additional effect of soot destruction through oxidation react ions. The general goal of this study is to investigate the potential for reducing soot propensity through the reduction in soot nucleation reactions which are the initiators of soot formation processes. The concept employed is electrostatic liquid drop charging for dispersing drops so as to avoid the creation of the fuelrichvapor regions where soot mrcleat ion occurs. ‘I’he relation between drop dispersion and soot formation has been experimentally investigated by Sangiovanni and Liscinsk y [21 who showed that the soot emission index decreases monotonically with the spacing between drops in a stream. The results were consistent for a variety of fuels and oxygen mass fractions in the surrounding gas. Since in that study [2] it is only the effect of drop spacing in a single direction that has been investigated, those results underestimate the benefit of drop dispersion in a real spray where a drop is surroundeci by other drops in all directions. The previous two years studies have focussed on: (1) calculations of fuel properties [3], (2) proof of the concept [4], and (3) elucidation of velocity effects (is it soot propensity reduction, or could it be soot oxidatioll effects) [5]. This year has been focussed on: (1) calculation of additional fuel properties (more recent fuels used by Law [6]), and (2) binary fuel effects where only one of the fuels is a HED fuel.