Near-field observations of a coaxial airblast atomizer under elevated ambient pressure

Spray atomization is a complex process that is vital in many industrial applications such as combustion, agricultural chemical application, and powder formation. Spray processes occur under atmospheric conditions as well as increased ambient pressure environments, providing a need to observe both for a more complete understanding of spray characteristics and control mechanisms. This study presents the results from a coaxial airblast atomizer operated within a newly commissioned Chamber for Assorted Pressurized Spray sUrveiLlancE, or CAPSULE. The CAPSULE is a 190 liter, 316L stainless steel pressure vessel with six sight glasses that facilitate multiple experimental techniques. For this study, high-speed, back-illuminated images are taken of sprays inside the CAPSULE at a constant momentum flux ratio of 27 & PLUSMN; 1 for increasing swirl ratios and ambient pressures up to 0.5 MPa. The fluids used in the spray are compressed air and distilled water. Results for spray angle and intact length measurements are presented and compared to data from previous atmospheric studies. The spray angle results show that increasing the ambient pressure increases the spray angle when the swirl ratio is sufficient, with the maximum spray angle occurring when SR =1 and Pamb = 0.5 MPa. Under lower swirl conditions, there was little to no difference in spray angle when varying ambient pressure. Intact length decreased with increasing swirl ratio, but there was little effect of ambient pressure. Atmospheric intact length measurements taken within the CAPSULE resembled those taken previously with atomizers of the same geometry.