Characteristics of soot and PAH formation in a micro flow reactor with a controlled temperature profile

A micro flow reactor with a controlled temperature profile was employed for rich methane/air and acetylene/air mixtures to examine the capabilities for the investigation of characteristics of soot and polycyclic aromatic hydrocarbons (PAHs) formation. In the experiment for a methane/air mixture, four kinds of flame and soot responses to equivalence ratio (1.5-4.5) and inlet mean flow velocity (5-40 cm/s), i.e., soot formation without flame; a flame with soot formation; a flame without soot formation; and neither flame nor soot formation, were observed. The soot formation was observed at high equivalence ratio and low flow velocity. Sooting limits, which depend on equivalence ratio and flow velocity (residence time), were successfully examined by the present micro flow reactor. To investigate the PAH formation process, the micro flow reactor was employed for a rich acetylene/air mixture at equivalence ratio of 4 and the flow velocity of 2 cm/s and gas sampling and analysis were conducted at temperatures from 600 to 1000 K. Temperature dependence of mole fractions of benzene, styrene, naphthalene, phenanthrene, indene, acenaphthylene and biphenyl was successfully obtained and larger PAHs such as pyrene and coronene were not observed in the present experiment. One-dimensional computation with ABF2.99 mechanism predicted three times higher benzene mole fraction than the experimental result. The modification of the ABF2.99 mechanism using recent benzene reactions significantly improved the prediction of benzene mole fraction. On the other hand, the modification did not affect the predictions of mole fractions of the other PAHs.