A parametric experimental study has been conducted to measure the discharge coefficient, the flow number, the film thickness, the spray angle, the velocity coefficient and droplet size of a large-scale simplex nozzle using ultrasonic and optical techniques. Seventeen nozzle geometries have been studied for three mass flow rates. The large-scale nozzle provides adequate resolution for measurements of film thickness, spray angle, and droplet size. The experimental data collected have been used to derive new and improved correlations for nozzle flow and breakup parameters. It is found that the atomizer constant (ratio of total inlet area to product of the swirl chamber and orifice diameter) is the primary parameter affecting the atomizer performance. As the atomizer constant increases, the discharge and velocity coefficients increase and the spray angle decreases.