Observatio of Sooting Behavior in an Emulsion Droplet Flame by Planar Laser Light Scattering in Microgravity

摘要

Two-dimensional visualization of the soot concentration profile in a flame formed around a suspended droplet was carried out under microgravity conditions using the planar laser light scattering technique. The 500-m drop shaft in Japan was used for microgravity experiments, which offers the effective time of the microgravity of 10 s and the relatively large space of the falling assemgbly for constructing the optical measurement system. The soot concentration and the instantaneous amount of soot were estimated approximately from the intensity of the scattered light using the image analysis system. The fuels employed were water-in-oil emulsions composed of base fuel, water, and surfactant. The base fuel was n-dodecane. The sooting region can be observed spherically around the droplet by using the apparatus developed in the present work. The results showed the unsteadiness of the sooting behavior and the flame behavior. Most of the soot concentration is located in the vicinity of the inner edge of the sooting region, which corresponds to the soot shell observed previously. The maximum of soot concentration does not vary with the water content, whereas the maximum amount of soot decreases significantly with water emulsification.