Liquid sheet and film atomization: a comparative experimental study

Liquid atomization processes are too complex to allow a purely theoretical study. Therefore experiments are necessary to quantify droplets production. In our problem, the replacement of an original complicated flow by a simpler one, i.e. liquid metal and high gas velocity by water and low air velocity, has led to a relation for the droplet diameter, thanks to dynamical similarity and order of magnitude estimates. Observation of a liquid film disruption development by high speed photography gives some informations about the mechanism of break-up in action. Granulometric measurements by video image analysis have specified the previous dimensionless relation for the mass median diameter. Measurements concern both the film and the sheet atomization, it is shown that the control of the liquid layer thickness is of major importance to control the quality of sprays.List of symbols d droplet diameter (m) - d _mm mass median droplet diameter (m) - g acceleration due to the gravity (ms^–2) - H _g , H _l gas slit width, liquid film thickness (m) - dimensionless parameters - Q ₁ = H ₁ V ₁ liquid flow rate (m²s^–1) - Reynolds number - T time(s) - V _g , V _l gas and liquid velocity (m s^–1) - W _c channel width (m) - Weber number - _g , _l gas and liquid viscosity (kg m^–1 s^–1) - _g , _i gas and liquid density (kg m^–3) - surface tension (kg s^–2) An abridged version of this paper was presented at the 6th ICLASS (Int. Conf. on Liquid Atomization and Spray Systems), Rouen, France, 18–22 July 1994