Velocity measurement of magnetic particles simultaneously affected by two-phase flow and an external magnetic field using dual-sided SPIM-µPIV

Abstract

Micro-particle image velocimetry (µPIV) measurement in gas–liquid flow is a challenging task mainly due to the volume illumination of the laser light. A special solution frequently adopted is the use of a thin laser sheet with a reduced macro-scale 2D-PIV illumination method. In this study, a novel dual-sided single-plane illumination microscopy-micro particle image velocimetry (SPIM-µPIV) technique was developed and successfully applied to multi-phase flow. The velocity of magnetic particles in a power-generation unit using waste heat simultaneously affected by two-phase flow and an external magnetic field was measured. This technique illuminates a light source in a thin sheet form, thus reducing errors due to particle overlap. Both sides of the laser sheet were illuminated to prevent particle shadowing and amplify the fluorescence signal. The velocity distributions of the wall and center were measured simultaneously. The average magnetic particle diameter was 200 nm; the excitation and emission wavelengths were 530 and 650 nm, respectively. The central magnetic force of the external magnetic field was 0.23 T. The velocity of the magnetic particles was measured under bubbly and slug flows, where magnetic particles are disturbed and power can be generated. For the bubbly flow, the velocity and vorticity were reduced by 11.89% and 32.29%, respectively, and by 34.70% and 8%, respectively, for the slug flow. The bubbly and slug flows showed opposite results in terms of velocity and vorticity reduction.