Numerical simulation of particle jet in supercritical water environment based on an improved coarse-grained CFD-DEM method

Abstract

Supercritical water gasification is an innovative way to clean and green coal conversion. Nevertheless, the flow dynamics of the fluid-particle introduced into the reactor via the nozzle still require further investigation. In this study, the fluid-particle flow dynamics within the supercritical water environment are examined by an improved Coarse-grained CFD-DEM method. The fluid flow field, particle evolution process, particle velocity and temperature distributions, as well as the particle forces and energy variations during evolution are analyze. The primary findings indicate that the instability of the jet flow field in a supercritical water environment is amplified with a reduction in incident temperature, thereby enhancing heat transfer and mixing. The violent perturbations between the fluid and the particles result in a more complex particle evolution process. In contrast, incidence conditions of transcritical and supercritical have no significant effect on the particle velocity distribution. Furthermore, the variation of particle temperature along the jet axis approaches the incident temperature as the incident temperature increases. Additionally, the particle drag force accounts for 70 % of the total force, and its translational and rotational kinetic energy decreases with increasing incident temperature. This research reveals the mechanism of particle dispersion in supercritical water environment, and supplies a reference for optimized configuration of supercritical water gasification reactor and the improvement of model.