低NO_(x)旋流燃烧器冷态动力场数值模拟研究

Numerical Simulation of Cold Dynamic Field on Low NO_(x) Swirl Burner

为解决采用OPCC型旋流燃烧器的锅炉出现大面积燃烧器喷口烧毁的问题,基于商用计算流体力学软件Fluent对OPCC型旋流燃烧器开展数值模拟研究,采用控制变量法研究中心风,一次风,内、外二次风风速与旋流燃烧器冷态动力场的关系。结果表明:中心风风速与回流区距喷口距离成正比例关系;中心风风速过小会增加燃烧器喷口烧毁的可能性,风速过大易造成大回流区紊乱。一次风风速过小或较大会分别导致大回流区的轴向长度和径向宽度明显减小。内二次风风速低于一次风风速时,内、外二次风将产生飞边现象,极易诱发因水冷壁沾污结渣和高温腐蚀而导致的水冷壁爆管和炉膛熄火等事故;内二次风风速高于外二次风风速时,大回流区的轴向长度和径向宽度均减小。外二次风主要影响回流区的大小和范围;外二次风风速低于一次风风速时,无法形成良好的回流区;外二次风风速高于内二次风风速且梯度较大时,大回流区轴向长度减小。因此在工程实际中,中心风风速应采用适中的5 m/s,一次风风速应选用适中的22.4 m/s,内二次风风速宜采用高于一次风风速的35.2 m/s,外二次风风速应采用高于内二次风且梯度较小的36.4 m/s。

In order to solve the problem of large-area burner nozzle burn-out of the boiler unit with OPCC swirl burner,this paper carries out numerical simulation study on OPCC swirl burner by using the commercial computational fluid dynamics software Fluent,and studies the relationship between the cold dynamic field of swirl burner and the wind speeds of variable central air,primary air,internal and external secondary wind using the control variable method.The results show that the central wind speed is in direct proportion to the distance between the reflux area and the nozzle.If the central wind speed is too small,it will greatly increase the possibility of burning the burner nozzle,while if the central wind speed is too large,it is easy to cause disorder in the large reflux area.If the primary air speed is too small or large,it will significantly reduce the axial length and radial width respectively of the large reflux area.When the wind speed of the internal secondary air is lower than that of the first primary air,the internal and external secondary air will produce flash phenomenon,which is very easy to induce accidents such as water wall tube explosion and furnace flameout caused by water wall fouling and slagging and high-temperature corrosion.When the wind speed of the internal secondary air is higher than that of the external secondary air,the axial length and radial width of the large reflux area are reduced.The external secondary air mainly affects the size and range of the reflux area.When the wind speed of the external secondary air is lower than that of the primary air,the external secondary air cannot quickly hold the relatively rigid primary air to form a good reflux area.When the wind speed of the external secondary air is higher than that of the internal secondary air and the gradient is large,the axial length of the large reflux area decreases.According to the research results,it is suggested to adopt a moderate wind speed of the central wind at 5 m/s,the primary air speed is moderate at 22.4 m/s,the internal secondary air speed is suitable at 35.2 m/s and the external secondary air speed is appropriate to be adopted with smaller gradient at a wind speed of 36.4 m/s in actual projects.