International Journal of Multiphase Flow ( IF 3.083 ) Pub Date : 2020-01-10 , DOI: 10.1016/j.ijmultiphaseflow.2019.103189
Simon Wachter, Tobias Jakobs, Thomas Kolb

The present work aims for the isolated investigation of the influence of system pressure on spray quality of twin-fluid atomizers. An approach of pressure adapted nozzles was applied, allowing for constant mass flows, gas-to-liquid ratio as well as fluid velocities at the nozzle orifice independent of system pressure. Two Newtonian liquids featuring viscosities of 1 and 100 mPa · s were used, varying the system pressure from 1 to 16 bar for gas velocities of 60, 80 and 100 $\mathrm{m}·{\mathrm{s}}^{-1}$. A phase doppler analyzer was applied for measurement of resulting drop size and velocity. Primary breakup morphology was detected by a high-speed camera. Two regions with different dependencies of spray quality on system pressure were identified. Applying pressure adapted nozzles while increasing system pressure, first results in a decrease of droplet size followed by an increase. A maximum of the dynamic pressure of the gas phase was determined at minimum droplet size, which is explained based on the theory of a free jet. The observations are underlined by images of the high-speed camera. Here, a change in breakup morphology from fiber type to a mixture of fiber type and non-axisymmetric Rayleigh type breakup at high system pressure was observed.

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