Numerical investigation on drag coefficient and flow characteristics of two biomass spherical particles in supercritical water

Supercritical water fluidized bed (SCWFB) is a novel reactor which can achieve efficient and clean gasification of biomass. The study of supercritical water (SCW)-solid two-phase flow characteristics in SCWFB is of great significance for biomass conversion and optimization of the reactor. However, the work on the drag coefficient of single biomass particle and biomass particle cluster has limitations to describe the interactions between particles accurately. In this paper, two-particle model was used to study the drag coefficient and flow characteristics of supercritical water flow past biomass particle cluster in the range of 10 < Re < 200. The simulation results show the interactions between particles can transmit larger distances perpendicular to the flow field at low Re. Drag coefficient of particles is mainly affected by the wake zone generated behind the upstream particles and nozzle effect between particles. Nozzle effect which is significant at high Re will promote flow separation and make form drag and friction drag increase. And the wake zone generated behind the upstream particles has the opposite effect.