ID 270

Effect of spill orifice design on discharge characteristics of spill-return pressure-swirl atomizers

 

Abstract:

Pressure-swirl (PS) atomizers are much favoured for their simple construction, reliability and fine spray. They produce a hollow cone spray with drop sizes strongly linked to the inlet overpressure, pl. Their disadvantage is a limitation in turn-down ratio due to their flow rate dependency on the square root of the pl. To overcome this drawback, a spill-return (SR) version was developed in the past. In this work, small SR PS atomizers were exper-imentally investigated using PDA and high-speed imaging with the aim to determine the effect of the SR orifice design, e.g. the positioning of the axial and off-axis spill orifices, their number and inclination on control charac-teristics, nozzle efficiency and spray characteristics. These data are not to be found in the open literature. The axially positioned SR orifice shows an unstable spray for low spill-to-feed ratios (SFR) compared to the off-axial spill orifice version that produces a stable spray at all tested regimes. However, the axially placed SR ori-fice was found to be more energy efficient as it required a lower spill flow rate to achieve the same injection flow rate. The radial position of the SL orifices affects the turndown ratio and the spray characteristics such as spray cone angle and Sauter mean diameter.