Computational study of 16 kW furnace cofired using pulverized bituminous coal and liquified petroleum gas operated in un-staged and air-staged conditions

This paper presents a computational study on air-fuel combustion of bituminous coal and liquified petroleum gas (LPG) in a 16 kW test facility with a coflow-swirl burner. The performance of three turbulence models is investigated for the furnace operated under both air-staged and un-staged conditions by comparing their predictions with the reported measurements of temperature and species concentrations. This comparison shows that the shear stress transport (SST) k-ω model and SST k-ω model with low-Re correction predict the profiles of temperature and species concentrations reasonably well, but significantly underpredict the temperature in the furnace core at axial locations away from the burner. On the other hand, the transition SST k-ω model provides better overall congruency with the measured temperature and species concentrations when compared with the other turbulence models used, as indicated by relatively higher values of the Pearson correlation coefficient at locations away from the burner. The present high-fidelity computational model developed is also capable of accurately simulating the effect of coal particle size on the furnace environment, which is verified by the match between the computational predictions and the experimental results for two different sized coal samples. The model is also used to investigate the effect of coal particle size on the internal recirculation zone (IRZ) and the reattachment length (L) for the same inlet swirl number (SN). A decrease of nearly 50% in the coal sample size results in the increase of L and IRZ length by 20% and 82.6%, respectively.