Effects of surrounding air temperature on soot distribution and deposition characteristics in laminar diffusion flames near solid walls in microgravity

Soot particles play an important role as a heat radiation media for heat exchanger of boiler or chemical reactor, while it is one of the most typical air pollutants and may cause soot deposition to heat exchanger to lower the thermal efficiency. Consequently, soot particle formation mechanism is one of the most important subjects to be studied in combustion field. A study on the position change of flame, soot distribution, and a relative change in the peak value of soot volume fraction by surrounding air temperature, and to know the correct thermophoretic effect acting on the in situ soot particle presenting in flame zone was carried out. A stable diffusion flame around solid rod was formed in a microgravity environment. In normal gravity, a flame surrounding cylindrical burner fluctuated periodically because of buoyancy presence and relative position of flame and solid surface changed time by time. The use of microgravity was strongly required to know the interaction between flame and solid wall to determine soot distribution. The motion of soot particle and soot deposition behavior on the wall was clarified by calculations. The mechanism of soot deposition near solid wall based on the microgravity experiment and calculation data was discussed. This is an abstract of a paper presented at the 30th International Symposium on Combustion (Chicago, IL 7/25-30/2004).