Soot Formation in a Shock Tube under Elevated Pressure Conditions

Abstract

Abstract High pressure soot formation from methane, ethylene, acetylene, propane and n-heptane was studied at rich burning conditions applying the shock tube technique. Pressure behind reflected shock was varied between 15 and 100 bar. Time resolved measurements of soot particle diameter and number density were carried out using an extinction-scattering technique at 488 nm. It could be shown that soot formation at high pressures is characterized by particle diameters below 30 nm that decrease with pressure. The corresponding high particle number densities in the range of N≈1012 — 10131/cm3 turned out to be considerably higher than at atmospheric conditions. This behavior has to be attributed to reduced coagulation coefficients in the transition regime between free molecular and continuum flow. It was found that an increase in carbon concentration has a strong promoting influence on soot volume fraction. Total pressure, however, does significantly enhance soot yield at pressures up to 30 bar and loses its ...