The present investigation examines the fundamental aspects of airblast atomization in both the breakup and drop dispersion regimes. Experiments were conducted using a high-magnification 4×5 camera and a Phase/Doppler particle analyzer to evaluate the spray characteristics and atomizer performance. The primary parameters of interest are: liquid film breakup length, spray angle, drop size and trajectory. Observation of wave formation and propagation along the sheet surface was made to provide guidance in formulating mathematical models. Effects of air flow and nozzle design on atomization were examined for a wide range of flow conditions.
Computational analysis was also utilized to predict the sheet breakup and subsequent drop behavior. This model considered a swirling sheet interacting with the surrounding air streams. The governing equations were formulated in a curvilinear coordinate system conforming to the film boundaries. Primary breakup is based upon linear stability analysis. The present model is capable of predicting the variations in thickness, trajectory, velocity, and angle of a liquid film as a function of nozzle geometry, operating conditions, fluid properties, and ambient conditions. Secondary breakup and drop history calculations were also included in the model to provide local drop size spectra.
Agreement between the experimental and predicted breakup length and angle was excellent. The predictions of drop size, trajectory and other parameters were qualitatively correct. The present investigation demonstrated a realistic approach for simulating the breakup process and described the physical structure of a pure airblast atomizer spray.