On the Distance Required to Atomize Diesel Sprays Injected from Orifice-Type Nozzles

Abstract

Conductivity probe measurements, using ranges of nozzles, liquid properties and gas densities, have revealed more extensive and reliable information on the break-up process of diesel sprays than has been published to date. The spray generated from a single-hole orifice-type nozzle has an incompletely atomized break-up length which typically extends at least 100 hole diameters downstream. The physical structure of this break-up zone varies, depending on the liquid properties and both initial and boundary conditions, from that of a central liquid column, with outer drops and ligaments, to, more typically, that of a chaotic ‘wire wool’ structure of ligaments and drops. Time variations of the break-up length are found during spray pulses and concentrations of poorly atomized liquid are convected downstream in the form of coherent structures. The existence of this zone has repercussions with respect to spray-gas flow interaction, fuel vaporization and wall wetting in internal combustion engines.