Experimental and theoretical approaches to droplet size, velocity, and temperature distributions of a cylindrical liquid jet.

摘要

The function of a spray is to increase the surface area of the emanating liquid to enhance the heat and mass transfer across the interface of the spray and surroundings. A model based on maximum entropy formulation has been derived for the system experiencing Rayleigh jet breakup with satellite droplets. A complete description for droplet size, velocity, and temperature distributions of a cylindrical liquid jet is accomplished experimentally for various flow conditions. Droplet temperatures are measured by employing a disk-shape micro thermocouple and an infrared photo sensor. Droplet sizes and velocities are measured by using a high-speed imaging system.;Maximum entropy principle has been formulated on a spray system in Riemann form. This formulation not only improves former researchers' derivation on spray systems but also clarifies the relationship of the joint probability function. Two additional constraints are added into the analysis to characterize droplet temperature distribution of a cylindrical liquid jet. Numerical predictions and experimental results are in good agreement under the thermal radiation constraint.;The cylindrical boundary layer has been analyzed for a stationary and a moving cylinder using the von Karman integral equation and the Reynolds analogy. The viscous drag and surface heat transfer rate of the moving cylinder model are greater than those of the stationary cylinder model for most regions of high initial Reynolds numbers.;The flow structures of an airblast atomizer are studied by using flow visualization and laser Doppler velocimetry. The flow from the center jet interacts with the conical airflow of the outer annular jet. This naturally forms an active source of generating instabilities in the flow. LDV measurements are achieved by employing a back-scatter, one-component system. The flow configurations are free mixing flow, confined mixing flow, and side-dump mixing flow. Turbulent intensity, variance of fluctuating velocities, and turbulent kinetic energy are locally enhanced by the presence of high viscous shear stress in the flow. The wall in the confined mixing flow has a strong effect on the variance distribution of the r-component fluctuating velocities.