The influence of varying the oxidizer stream velocity on the sooting structure of an ethylene/air counter-flow diffusion flame, stabilized around a porous cylinder, has been examined. Laser light scattering and extinction measurements have been made to determine the soot parameters in the forward stagnation region. Temperature and velocity were measured to locate the flame front and to enable calculation of the soot residence time and growth rates. The soot loading, represented here by the soot volume fraction, was found to decrease with increasing oxidizer velocity; e.g. maximum vlaues of 9.3×10-7, 6.7×10-7, 5.4×10-7 and 3.6×10-7 for oxidizer velocities of 21, 38, 58 and 67 cm/sec respectively. The variation of the peak measured temperature was very small (1907-1927° K). The number of soot particles did not vary significantly within this velocity range. Maximum particle size decreased with increasing oxidizer velocity as a result of the reduced residence time for coagulation and for surface growth reactions with fuel pyrolysis products. The specific surface growth rate (/S), when examined in terms of particle age, show the typical decrease with time (age). For velocities of 21, 38, and 58 cm/sec the rates are very similar close to the flame front, but deviate later on. In the highest approach velocity case, 67 cm/sec, the growth rate is lower than those of the other cases also in the immediate vicinity of the flame front (where the soot particles are young and thus have a high surface reactivity).
ASJC Scopus subject areas
- Chemical Engineering(all)
- Fluid Flow and Transfer Processes
- Physical and Theoretical Chemistry
- Energy Engineering and Power Technology
- Fuel Technology
- Mechanical Engineering