Velocity of gas from free fall type atomisers

The velocity of gas around the geometric point of atomisers of different focal lengths, apex angles, and number and diameter of nozzles was studied as a function of plenum pressure by measuring pitot pressure. The gas field around the geometric point was found to consist of widely varying velocities. The velocity increases with increase in plenum pressure and diameter of nozzle but with decrease in focal length. The change in velocity was found to be insignificant with cither change in apex angle or number of nozzles. Empirical correlations were obtained to determine the velocity at and downstream of the geometric point. The exponent value of the power function of the downstream velocity was shown to decrease exponentially with increase in the ratio of gas density to surrounding air. The discharge coefficient was found to be independent of plenum pressure but decreased with increase in total cross-sectional area of atomiser nozzles.