Influences of Fluctuating Flow Rate on Soot Emission from Coflow Diffusion Flame

Abstract

We experimentally investigated the soot emission characteristics of the coflow diffusion flame undergoing periodic fluctuation of fuel and air flow rates. The flame has been acoustically forced using sine-wave excitation of a loudspeaker attached to the upstream side of the burner. A fuel (propane) and an air are supplied respectively from inner tube and outer tube. The obtained results are summarized as follows: (1) The soot emission characteristics of the unsteady flame are worse than that of the steady flame. (2)The air flow rate at the soot limit increases monotonously as the mean value of fluctuating fuel flow rate increases as for the soot limit curve when frequency f is small. However, the soot limit curve becomes S shape when f is large. (3)Bulge and the separation of the flame tip are observed at f =16Hz and the soot emission characteristics deteriorate further. (4) Soot limit curve of the air flow rate change flame is similar to that of the fuel flow rate change flame.