**ABSTRACT**

Particle collision is an important process in soot particle growth. In this research, based on gas-solid two-phase flow, particle trajectory was traced by the Lagrange approach with periodic boundaries. Trajectory intersection, collision probability, and critical velocity were considered, and the growth path of each particle was traced. The collision frequency (fc), agglomeration frequency (fa), and friction collision frequency (ffc) were calculated, and the main influence factors of particle collision were analyzed. The results showed that fc, fa, fa/fcincreased with the increase of the particle volume fraction and gasphasevelocity(v), but the particle initial diameter (dpi) andvhad the great influence on fa/fc. fa/fcobviously decreased with the increase of dpiand v.The statistical analysis of fa/fcand Stokes number showed that fa/fcdecreased with the increase of Stokes number, especially when stokes number was extremely small, fa/fcdecreased rapidly. Using the trajectory analysis of each particle, the particle growth process could be classified in three types: firstly, the particles that did not agglomerate with any particles during the entire calculation process; secondly, the particles that continually agglomerated with small particles to generate larger ones; and finally, the particles that were agglomerated by larger particles at some calculation moment.

**KEYWORDS**

PAPER SUBMITTED: 2019-11-10

PAPER REVISED: 2020-07-30

PAPER ACCEPTED: 2020-07-31

PUBLISHED ONLINE: 2020-08-08

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