MILD combustion of oxygen fuel burner using impinging jet method

Abstract

The possibility of oxygen-MILD combustion without preheating of oxidants is assessed numerically and experimentally in this paper. For the formation of oxygen-MILD combustion, jet impingement method was employed to enhance the internal recirculation flow effectively and also compensate the drawback which the momentum of oxygen becomes smaller than that of air combustion. And effects of impingement and reactant jet velocity were analyzed to investigate the extent of internal recirculation necessary for formation of oxygen-MILD combustion. Results show that as the velocity of oxygen increases, the stronger internal recirculation ratio (KV) makes the oxygen jet more diluted leading to reduce the maximum temperature and high-temperature zone inside the combustion field. It is found that MILD combustion having a uniform temperature distribution can be formed at low oxygen velocity with increasing impingement angle. The Damköhler number at the oxygen velocity of 120 m/s approaches to 1 as the impingement angle increases and MILD condition of Da < 1 and Ret < 10,000 was satisfied at the oxygen velocity of 220 m/s. Diffusion jet flame to MILD combustion flame was observed experimentally as the impingement angle increases at the oxygen flow velocity of 120 m/s. But at higher Voxy = 220 m/s, the effect of impingement angle is not critical, unlike Voxy = 120 m/s. The experimental results clearly support various numerical results which can provide valuable data for designing the oxygen MILD based the furnace.

Keywords

• mild (moderate or intense low oxygen dilution) combustion
• oxygen flame
• jet impingement
• recirculation ratio (kv)
• pilot scale furnace
• nox reducing technique