Spray characteristics of diesel fuel containing dissolved CO2

Abstract

The effect of adding CO2 to diesel fuel has been studied by several groups that used tailor-made injectionsystems 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 CO2 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 arapid flashing process that results in an intensive disintegration of the liquid bulk into small droplets. Inthe present study, we present an experimental study of the atomization process of diesel fuel containing dissolved CO2 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 CO2, is significantly promoted by the flash-boiling phenomenon, which results in low SMD sprays, low D0.1 droplets, a faster breakup mechanism, and a more uniform droplet size distribution