Study on droplets characteristics used for infrared spectrum suppression

A model is developed to predict the motion and evaporation characteristics of spray droplets which are used for infrared stealth based on the assumptions of single droplet and spherical symmetry. There are lots of parameters like sprays properties and ambient conditions that affect the stealth process, but only several factors such as wind, irradiation, initial values of sprays, etc. are discussed. Some investigations are done with the condition of coupled effect of radiation and forced convection, to reveal that radiation and forced convection have only a little influence on the droplets life and can be basically neglected when the process is carried out in the out-door environment. The dominant influencing factors are ambient humidity and initial diameters of the spray droplets. The biggish droplets are beneficial to dispersion of sprays, however, the oversize ones will shorten there life because of the sedimentation. So there is an optimum initial diameter needs to be considered. The study also reveals that the influence by the forced convection to the droplets temperature can be basically neglected, for the initial relative velocity between droplets and air will be quickly attenuated to be 0. But the radiation will result in a significant temperature rise of the droplets which will be higher than the ambient. In addition, the droplets temperature will present a varying law of firstly rising and then dropping.