Improvements in laser sheet dropsizing using numerical and experimental techniques

Abstract

Laser sheet drop sizing (LSD) technique is used along with numerical tools to improve the accuracy of planar drop sizing in dense sprays. The multiple scattering in Mie and Planar Laser Induced Fluorescence (PLIF) signal is reduced using the Structured Laser Illumination Planar Imaging (SLIPI). The numerical corrections are applied to reduce error due to laser sheet scattering, absorption and auto-absorption of the PLIF signal. A novel methodology is proposed to measure the planar distribution of optical depth (OD) in airblast sprays using the LSD technique. The optical depth is observed to increase with an increase in Gas to Liquid mass Ratio (GLR) in air-blast sprays. It is demonstrated that, dependency of the LSD technique on another independent drop sizing technique can be minimized in airblast sprays using an empirical correlation. It is observed that the use of SLIPI improves the reliability of the LSD technique even in optically dilute sprays. The improvement in LSD techniques is significantly higher in dense sprays with the optical depth higher than 2.5. The maximum Mean Average Percentage Error (MAPE) reduced from 40% in conventional LSD technique to ∼12% for SLIPI-LSD with numerical corrections in dense sprays with OD ∼ 6. For the sprays with higher droplet density, it is necessary to use SLIPI in a combination with numerical correction techniques to improve the accuracy of the planar droplet sizing technique.