TiO2 and SiO2 Formation in Corona Discharge Assisted Combustion

CHANAKYA BAGYA RAMESH, Daoru Han, Yang Wang, University of Miami

     Abstract Number: 353
     Working Group: Combustion

Abstract
Plasma assisted combustion (PAC) has been proposed as a greener alternative to conventional combustion as it increases flame stability and efficiency, especially during the combustion of low-grade fuels. PAC is different from conventional combustion due to plasma's kinetic, thermal, and hydrodynamic effects on combustion. Due to these effects, PAC may result in very different particle formation mechanisms, thus the physiochemical properties of the combustion-generated particles are expected to be influenced. This study introduced a non-thermal atmospheric pressure plasma (AC corona discharge) into a conventional methane-air premixed flame to understand how plasmas influence particle formation (D_p <10nm) during combustion. Here, we use the particle synthesis precursors TTIP and TEOS (Ti- and Si-based) to study the formation of TiO₂ and SiO₂ during combustion under plasma and non-plasma conditions. For both oxides, cluster formation and subsequent growth are observed to be enhanced up to a certain precursor feed rate. For TiO₂ (up to a feed rate of ~67.7 μmol/hr), the D_p increases by as much as ~43%. For SiO₂ (up to a feed rate of ~288 μmol/hr), the D_p increases by as much as ~9%. Beyond this feed rate threshold, introducing plasma seems to inhibit the formation and growth of particles, with up to ~13% decrease in D_p for TTIP and up to ~20% decrease in D_p for TEOS. This observation suggests that the particle formation and growth mechanism in PAC depends on the concentration and physiochemical properties of ions, which further influence the particles that are formed eventually. It was also seen that these effects were more significant for negatively charged clusters, showing the role of the more mobile charge carriers (e.g., electrons) in such systems.