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

摘要

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% CO_2 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.