GENERATION OF CO AND SMOKE DURING UNDERVENTILATED COMBUSTION

The CO and smoke yields observed for underventilated laminar diffusion flames are presented for methane and ethene for global equivalence ra tio PHI over the range 0.5 to 4.0. A Burke-Schumann type burner with f uel in the center tube and air in the annular region was used. The pea k CO yields for methane and ethene, 0.37 and 0.47, respectively, are a t least a factor of 100 greater than for overventilated burning. The r atio of CO/CO, versus PHI for the methane flame is compared with local measurements of this ratio for both overventilated and underventilate d laminar diffusion flames and with the results for turbulent natural gas flames quenched in an upper layer. The peak smoke yields for metha ne at a flow rate of 10 cm3/s and for ethene at a fuel flow rate of 6. 4 cm3/s are 0.01 and 0.05, respectively, compared with yields of 0.0 a nd 0.028 for the overventilated case. The proportionality between smok e yield and CO yield observed for overventilated burning for a wide ra nge of fuels is found not to be valid for the under-ventilated case. T he chemical makeup and structure of the smoke produced at high equival ence ratio is qualitatively different from smoke produced under overve ntilated conditions; the smoke is mainly organic rather than graphitic and it has an agglutinated structure rather than an agglomerate struc ture with distinct primary spheres usually observed in overventilated burning.