EFFECT OF "COLD" ZONE ON PARTICLE FEATURES IN BURNER-STABILIZED STAGNATION (BSS) PREMIXED ETHYLENE FLAMES

In burner-stabilized stagnation (BSS) flames the probe used to sample particles is embedded in a disk. This allows to have well defined boundary conditions; however, particles pass through a "cold zone" (temperature below 1000K). This zone can significantly modify the features of the particles due to condensation of material from gas phase onto the particles. In order to investigate the effect of this zone, particulate collected from ethylene burner-stabilized stagnation flames was chemically characterized. Several diagnostic tools were used to shed light on the effect of temperature on soot properties in this peculiar flame configuration. Particles were thermophoretically sampled on the stagnation plate and analyzed by Raman and UV-visible spectroscopy, techniques sensitive to particle internal structure. Complementary information on the functional groups located at the edge of the polyaromatic system constituting soot nanostructure was obtained by FTIR analysis. The experimental conditions chosen provide a broad range of sooting conditions to understand the temperature effect on soot properties in ethylene BSS flames.