Spray characteristics of diesel fuel containing dissolved CO₂

The effect of adding CO₂ to diesel fuel has been studied by several groups that used tailor-made injection systems to achieve notable low Sauter mean diameters (SMDs). In the present study, we use a real commercial fuel injection system and study the effect of the amount of dissolved CO ₂ on the resulting spray characteristics. In this case, when the mixture enters the injector and flows downstream through the variable cross-section passage toward the discharge orifice, partial nucleation of the dissolved gas is expected to occur at different locations along the duct, which transforms the mixture into tiny bubbles that grow fast downstream. When the mixture is driven out through the discharge orifice, these bubbles undergo a rapid flashing process that results in an intensive disintegration of the liquid bulk into small droplets. In the present study, we present an experimental study of the atomization process of diesel fuel containing dissolved CO ₂ that occurs in steady flow conditions. An extensive study was performed to map the effect of the CO₂ content on the spray SMD and droplet distribution at different locations downstream the discharge orifice. It is concluded that the atomization of diesel fuel containing dissolved CO ₂, is significantly promoted by the flash-boiling phenomenon, which results in low SMD sprays, low D_0.1 droplets, a faster breakup mechanism, and a more uniform droplet size distribution.