Soot emissions of mutually synchronized candle flames

Abstract The evolution of soot particles from steady flames is relatively well explored compared to the evolution of soot particles from oscillating flames. Therefore, the present study aims to characterize soot particles' size evolving from self-excited oscillating flames, which are produced from the burning of two bundles of candles (4 candles/bundle). When two self-excited oscillating flames interact at various separation distances, they exhibit different modes of synchronization, namely in-phase synchronization (IP), amplitude death (AD), and anti-phase synchronization (AP). We captured the time-resolved flame images of synchronization modes using a digital camera and found that the AD mode represents the steady flames, whereas the IP and AP modes represent the symmetric and asymmetric oscillating flames, respectively. We measured the flame height and area for both the steady and oscillatory flames and found that the mean flame height is nearly invariant for all the flame modes, whereas the mean flame area exhibits significant variations among each synchronization mode. By using the Dynamic Light Scattering (DLS) technique, we measured the diameter of soot particles, and the results show that the smallest soot particles (78 nm) are produced at steady flames compared to their oscillatory flames counterparts. On comparing oscillatory flames, the symmetrically oscillating IP mode produced larger-sized soot particles (129 nm) compared to the asymmetrically oscillating AP mode (102 nm).