Numerical investigation of the effects of fuel variability on the dynamics of syngas impinging jet flames

Numerical simulations using the Large-eddy simulation technique is presented to study the effects of fuel variability on the dynamics of hydrogen and syngas impinging flames. The compositions of CO and H-2 are varied in a syngas mixture, including a pure H-2 case as the baseline Case 1, 20% CO with 80% H-2 for Case 2, 40% CO with 60% H-2 for Case 3, and 20% CO with 20% CO2 and 60% H-2 for Case 4. The impinging flame configuration has a distance to nozzle diameter ratio of H/d = 20 and the inlet velocity of the fuel is 27 m/s. The fuel is issued from a circular nozzle and mixes with air in a non-premixed configuration. The results show that the flames develop vortical structures in the primary jet associated with the buoyancy and shear layer instability, and the wall jet progresses parallel to the impinging plate forming large-scale vortex rings at different locations and strengths as a consequence of the fuel compositions. A comprehensive analysis of vortical structures in the primary and secondary jet streams, along with a description of their effects on the near-wall heat transfer and instabilities of syngas flames is presented here. Pollutant emissions and species formations are also investigated in order to gain further insight into the syngas burning characteristics for future cleaner combustion systems. (C) 2012 Elsevier Ltd. All rights reserved.