Elucidation of the gas flow and droplet behavior near the liquid sheet at the nozzle exit of the hollow-cone spray

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Behavior of droplets and the air flow in a hollow-cone spray was studied paying atteintion to the hollow-cone liquid sheet formed at the atomizer orifice. The shape of the liqiud sheet was investigated by taking photographs with a flush of Nd-YAG pulse laser. Phase Doppler method was used to detect the behavior of the droplets adjacent to the break-up point of the liquid sheet. Numerical simulation was carried out to compare the experiments to the predictions. The results obtained are as follows.(1) The cone angle of the liquid sheet formed at the atomizer orifice tends to converge or decrease along with the flow. The instantaneous angle is less than that of the observed time-averaged envelop of the liquid sheet. The direction of the liquid sheet flow at the break-up point dominates the initial droplet velocity and its direction. The shape is related to the surface tension of the liquid sheet.(2) The break-up point of the liquid sheet fluctuates up and down and the initial droplet velocity and the direction fluctuates significantly.(3) Numerical simulation incorporating the existence of the liquid sheet reveals that the the movement of the liquid sheet induces strong air stream and that this air stream selectively transports small droplets and plays an essintial role in classification of droplets by size and dispersion of droplets.