Particulate formation is greatly enchanced by the nondiluteness of a diesel spray because it is responsible for the creation of a fuel-rich vapor that accumulates without burning and instead undergoes complex chemical reactions [1, 2] which, combined with nucleation processes, [2-4] form soot. Since premixing was found to eliminate soot [1], it is clearly desirable to burn the nondilute spray injected in a diesel engine cylinder in a dilute configuration.
Since injector design has been pushed to the limit and turbulent dispersion is not totally reliable either, other means to disperse the spray must be found. This communication presents a model illustrating one novel possibility. By electrically charging each drop of the cloud with the same charge, the spray expands by drop repulsion, and thus becomes dilute. This expansion can be achieved to any level of diluteness found acceptable from the point of view of soot formation and depends upon the drop charge only. Droplet charging might, also induce secondary atomization of the drops [5], which presents an additional benefit of this concept.
In this model, the droplet cloud is spherical and all quantities in the cloud are spherically symmetric. It is also assumed that injection, evaporation, ignition, and, finally, combustion of the drops are events that occur sequentially. Under these conditions, knowing the cloud density n o at the time of injection t o , and the desired cloud density n f (<n Β°) at time t f at which evaporation