煤粉射流火焰的典型形态及其转捩规律

Classification and Transition of Pulverized Coal Jet Flames

利用Hencken型燃烧器研究了一次风速度、给粉浓度和二次风氧浓度等参数变化对煤粉射流火焰形态的影响规律,得到了煤粉射流火焰形态转捩图谱.实验表明,煤粉射流火焰形态主要分为煤粉群燃火焰(亮黄色,均相燃烧主导)和单颗粒稀释火焰(暗红色,异相稀释的煤颗粒燃烧主导).挥发分含量和煤粉浓度的增大均可促使稀释火焰向群燃火焰的转捩;在二次风氧浓度较高(15.3%,)时,提高一次风速度对火焰形态的影响有限,但同时降低氧浓度到10%,,则可实现群燃火焰向稀释火焰的转捩.

The influence of key parameters on pulverized coal jet flame,such as primary flow velocity,coal feed concentration and O_2 concentration in the secondary flow,was investigated experimentally through Hencken burner.The transition criteria of coal jet flames were obtained.The experimental results reveal that the pulverized coal jet flames under different operating conditions can be typically divided into group combustion flame（GCF）and single particle dilution flame（SPDF）.The GCF is dominated by homogeneous combustion,thus displaying luminous yellow flames.The SPDF is dominated by heterogeneous combustion of dispersed coal particles,therefore exhibiting a dark red flame cloud.Increase of coal volatile content or coal feed concentration can promote the transition from SPDF to GCF.The influence of primary flow velocity on coal jet flame transition is limited when the O_2 concentration is 15.3%,.However,when the O_2 concentration in the secondary flow is decreased to 10%,,the flame can be transited from GCF to SPDF as the primary flow velocity increases.