Generation of Dense Fogs for Infrared Multiple Scattering Applications.

摘要

A continuous flow fog chamber was built with the fog generated by a commercially available spray nozzle. The droplet size spectrum produced resembles that natural fog and is 10 to 100 times denser. An optical depth of 3 to 5m was obtained with the present setup, and it is feasible to decrease the optical depth (i.e., increase the fog particle density) by an order of magnitude by using multiple spray nozzles. The spectral shape was found to be insensitive to the operating parameters of the commercially available spray nozzle. Preliminary experiments were carried out to produce fog with a variable size spectrum. The amount of small droplets (radius<2 micrometers) produced by the nozzle can be increased or decreased by an order of magnitude by mixing steam or hot air with the spray. Experiments were carried out to grow sodium chloride nuclei in steam by passing the mixture through a cooled pipe. Preliminary results were very encouraging as a significant amount of large particles ( 5 to 10 micrometers radii) were obtained by changing the temperature of the coolant in the heat-exchanger pipe. Fog densities achieved with these controllable, large-particle spectra were up to 100 times greater than natural fog. (Author)