直流燃烧器参数对氧煤燃烧特性的影响

Effect of Parameters of Direct-Flow Burner on Combustion Characteristics of Oxy-Coal

以Φ200 mm×2 m的火焰炉为对象,借助软件FLUENT研究了在O_2/CO_2气氛下燃烧器射流动量比和射流间距的改变对炉内流场特性和燃烧特性的影响.结果表明:当射流动量比由28增至66时,烟气内循环率峰值呈现先增大后减小的趋势,混合区烟气内循环率的整体水平是在射流动量比为48时最大;随着射流间距的增大,Oxz轴面回流区向下游偏移,且氧气质量分数高于10%的区域逐渐缩小,燃烧峰值有所降低,当射流间距增至75mm时,Oxz轴面回流区的范围明显缩小,反应区氧气体积分数回升,使得燃烧峰值升高.同轴射流方式下的燃烧峰值最高,约2 200K,仅当射流间距为60mm工况下的炉膛燃烧最大温升小于煤粉的着火温度(790 K),即可实现氧煤MILD(moderate or intensive low oxygen dilution,温和)燃烧.

The software FLUENT was applied on a Φ200 mm×2 m furnace to study the influence of jet momentum ratio and jet spacing on the flow field and combustion characteristics at 02/CO2 atmosphere. The results show that when the jet momentum ratio varies from 28 to 66, the peak of flue gas inner recirculation rate increases and then decreases, and the overall level of inner recirculation rate in the mixing zone is the largest when the jet momentum ratio is 48. When the jet spacing gradually increases, the recirculation zone on x-z plane shifts downstream. Besides, the region where the concentration of oxygen volume is higher than 10% narrows, the temperature peak decreases slightly.However, the jet spacing must maintain a proper value. When the jet spacing is 75 ram, the recirculation zone on the x-z plane narrows significantly, and the oxygen concentration in the reaction zone rises again, and, as a result, the temperature peak increases. The temperature peak is the highest （about 2 200 K） under coaxial jet condition, the max temperature increase is lower than the ignition temperature （790 K） only when the jet spacing is 60mm, indicating that the oxy-MILD combustion state can be established.