A computational analysis of the impact of boundary conditions on a particle-laden flow: A case study in a pressurized oxy-coal combustor

Abstract

Designing an effective burner is vital for the development of coal combustion technologies. Because of high pressure, the volumetric fraction of the coal particles at the fuel inlet of the POC burner approaches or even exceeds the limitations allowed by the commercial computational fluid dynamics (CFD) codes (e.g., Ansys FLUENT). Consequently, for such high particle volumetric fractions, the interplay between the particles, the fluid flow, and the wall need to be re-evaluated. The present computational work is a first step in a systematic analysis of the roles of various characteristics, specifically, the method of particle release, its location, and the particle size. In the POC process, pulverized coal is burned under elevated pressure in an O2/CO2 environment. Specifically, a 15-bar, 100 kWth, POC combustor is modeled with Ansys FLUENT using the Reynolds-averaged Navier-Stokes (RANS) approach. It is revealed that for this pilot-scale, pressurized burner, the gas phase flow velocity in the near-wall region exhibits some anomalies. In order to scrutinize the role of particle loading in the near-wall region, the particle release location is investigated. The numerical simulations incorporate coupling between the turbulent flow and the particles. It is found that the tuning of the particle release location makes the gas phase flow velocity consistent with the pure gas flow velocity profile. Moreover, the particle releasing location also influences the flame stability. The particle size is also found to have a significant impact on the particle trajectory, flame stability, and temperature.