Combined drop sizing using phase Doppler anemometry and high-speed imaging

The majority of conventional atomizers generate sprays with a polydisperse droplet size distribution. The spray size distribution width is one of the main spray characteristics and influences the efficiency of mass-transfer related applications such as CO2 capture efficiency in spray columns. A newly developed impinging effervescent atomizer is investigated at different operating regimes. The inlet pressure of 0.1 MPa and three gas to liquid ratio (GLRs) regimes of 2.5, 5 and 10% were tested. The spray droplet size distribution was investigated using two experimental techniques, Phase Doppler anemometry (PDA) and high-speed (HS) imaging. The droplet size distributions obtained by both experimental techniques are compared, both with slightly different results and features. Therefore, an approach with combining of the experimental data from both techniques is provided. More realistic droplet size distributions are obtained then, since PDA detects small droplets, while the HS imaging accurately captures large and non-spherical droplets. It was found that the spray polydispersity grows with increasing GLR. The spray contains most of its volume in large droplets for GLR=2.5%. With increasing GLR, the smaller droplets contain a larger volume fraction, but a small number of large droplets remains and thus increases the spray polydispersity.