Subcritical to supercritical mixing

Abstract

Liquid jet injection into a quiescent gaseous environment has been experimentally and analytically studied covering subcritical to supercritical conditions. The focus was placed on the influence that the surrounding gas pressure and temperature have on the jet breakup. Under subcritical conditions, the surrounding gas inertia and surface tension forces controlled this process with ligament formation from which the material broke off and the drops, later, formed. Decreasing surface tension influenced the jet surface behavior under transcritical conditions: Ligament formation was significantly reduced under these conditions with only occasional drop formation. Further increasing the pressure and temperature led to supercritical breakup modes. This manifested through a smoothening of the liquid-gas interface. Ligament formation was not observed under supercritical conditions; this indicated that surface tension did not play any role in the supercritical jet breakup. The experimental technique, using planar laser induced fluorescence, revealed important core jet structures previously undetected. A linear jet stability analysis was, then, performed to gain physical insight into the jet breakup mechanisms. The results showed good correlation with experimental results under subcritical mixing but failed to predict the transcritical and supercritical regimes.