Effect of N-2 and CO2 dilution on syngas/air deflagration characteristics in narrow gap disk burner

This study explored the typical features of flame from syngas/air premixed flame in a narrow gap disk burner based on diluted N-2 and CO2. Four concentrations (i.e. 10%, 20%, 30%, and 40%) of CO2 and five concentrations (i.e. 10%, 20%, 30%, 40%, and 50%) of N-2 were adopted in this study. The experiment was conducted in a narrow gap disk burner with a clearance of 2 mm. The results showed that the addition of N-2 and CO2 significantly reduced the brightness of flame, the flame propagation velocity, and the pressure resulting from the explosion. When the CO2 concentration reached 40%, the maximum pressure was reduced to 60.78 kPa, which was 41.5% lower than that without diluent. When the N-2 concentration was increased to 50%, the maximum pressure was reduced to 67.01 kPa, but at this point, the inhibition effect on the maximum pressure was not as good as 40% of CO2. Additionally, the dilution effect of CO2 was more obvious than of N-2. An analysis on the dilution mechanism found that reduced moles of critical radicals H, O, and OH were an important reason for the inhibition effect. However, with the increase of N-2 and CO2 concentrations, the unstable flame propagation behavior in a later stage was not inhibited, but enhanced. The unstable propagation behavior was related to the flow field disturbance caused by heat loss.