Impact of inlet air momentum on flameless combustion

Impact of inlet air momentum on flameless combustion characteristics was investigated numerically. Changing the inlet air momentum was achieved using different inlet air nozzle diameters (12, 10, 8 and 6 mm). The mixture mixing and recirculation ratio were obtained and evaluated. A Three-dimensional model was computed using ANSYS fluent. The computations were carried out using RNG k- ε with standard wall function for turbulence modelling. The GRI-EDC model was used to simulate the interaction between turbulence and chemical kinetic. The predicted results were validated against experimental data of small-scale flameless burner. The results showed that, reducing the air nozzle diameter from 12 to 6 mm increased the inlet air momentum, leading to an increase in the recirculation ration by more than 300% of its value at 12 mm. As a result, the O2 concentration decreased in the mixture at burner tip and supports flameless mode creation. The influence of inlet air momentum on combustion species (OH, HC, CO, and NO) were reported. It was concluded that increasing inlet air momentum reduces the greenhouse gases due to the decrease in reaction temperature and mixture dilution. Moreover, Transient radicals (OH and HC) decreased with increasing the inlet air momentum which supports the flame disappearance.