PARTICLE DIAGNOSTICS AND TURBULENCE MEASUREMENTS IN A CONFINED ISOTHERMAL LIQUID SPRAY

This work reports an experimental study of the behavior and structure of a liquid spray immersed in a strong swirling field. In order to sim ulate some of the aerodynamic conditions experienced by a spray in a m odel combustor, an experimental setup using an acrylic chamber, a vane type swirler, and separate air supplies for both the secondary air an d the swirl air were integrated to perform the experiments in the wind tunnel. A vane-type swirler exhibiting a high swirl number was used t o produce a strong recirculation flow field downstream of a pressure s wirl atomizer. Properties of the dispersed phase such as velocity, siz e distribution, and size-velocity correlation were measured at several locations within the swirling flow field. In addition, mean velocity and turbulence properties were obtained for the gas phase. Flow visual ization was performed with a laser sheet to gain further understanding of the formation and influence of the recirculation region on the spr ay. A two-component PDPA system with a frequency-based Doppler signal analyzer was used throughout the measurements, and proved most valuabl e in the toroidal vortex region where low SNR conditions and nonunifor m concentration of seed particles prevail. The results show that flow reversal of the drops is present at this swirl intensity within the re circulation region at distances up to X/D = 2. 0. Small variations of drop size distribution within the recirculation region are observed, h owever, large variations outside of it are also present. Plots of the normal Reynolds stresses and Reynolds shear stresses show double-peak radial distributions, which indicate regions in the flow where high me an velocity gradients and large shear forces are present. The decay of turbulence velocities in the axial direction was observed to be very fast, an indication of high diffusion and dissipation rates of the kin etic energy of turbulence.