目前大容量的机组普遍采用对冲式锅炉，对冲式锅炉的燃烧效果取决于燃烧器性能。为了分析DRB-4Z型旋流煤粉燃烧器流动及燃烧特性，运用Fluent软件对单只燃烧器流场分布和某单机容量1 000 MW超超临界机组（采用DRB-4Z型旋流煤粉燃烧器）燃烧过程进行模拟仿真。研究了一次风风速，内、外二次风风速,旋流强度对一次风刚度、回流区位置和范围的影响。对单只燃烧器流场模拟结果表明：DRB-4Z型旋流煤粉燃烧器一次风风速与回流区范围呈反比，额定负荷下一次风风速为16 m/s时流场分布较好，低负荷时一次风风速不宜低于12 m/s，避免煤粉着火点距燃烧器出口过近，高负荷下一次风风速不宜超过20 m/s，保证煤粉在燃烧初期得到充足的热量；内、外二次风风速与回流区范围成正比；内二次风风速28 m/s、旋流强度0.75时流场分布较好，对易燃煤种内二次风叶片开度可设置为30°、旋流强度为0.52，推迟一次风与内二次风的混合降低NOx生成。对难燃煤种内二次风叶片开度可设置为50°、旋流强度为1.02，保证回流区卷吸到足够的高温烟气使煤粉稳定燃烧；对锅炉燃烧过程模拟结果表明：炉膛中上层燃烧器区域温度最高，最高温度可达1 900 K，主燃区处于严重缺氧状态，主燃区严重缺氧虽可降低NOx生成，但还原性气体CO与H2S在燃烧器出口区域大量生成，易造成水冷壁高温腐蚀。

At present,hedge boilers are widely used in large capacity units,and the combustion effect of hedge boilers depends on the performance of burners. In order to analyze the flow and combustion characteristics of DRB-4Z swirl pulverized coal burner,the flow field distribution of a single burner and the combustion process of a 1 000 MW ultra supercritical unit (using DRB-4Z swirl pulverized coal burner)were simulated by Fluent software. The effects of primary air speed,internal and external secondary air speed and swirl intensity on primary air stiffness,location and range of reflux area were studied. The flow field simulation results of a single burner show that the primary air velocity of DRB-4Z swirl pulverized coal burner is inversely proportional to the range of reflux area. When the primary air velocity is 16 m/s under rated load,the flow field distribution is better. The primary air velocity under low load should not be less than 12 m/s,so as to avoid the ignition point of pulverized coal being too close to the burner outlet,and the primary air velocity under high load should not exceed 20 m/s,so as to ensure that pulverized coal gets sufficient heat at the initial stage of combustion,the wind speed of internal and external secondary air is directly proportional to the range of reflux area,when the wind speed of internal secondary air is 28 m/s and the swirl intensity is 0.75,the flow field distribution is good. For combustible coal,the opening of internal secondary air blade can be set to 30°,and the swirl intensity is 0.52,so as to delay the mixing of primary air and internal secondary air and reduce the generation of NOx. For difficult coal combustion,the opening of secondary air blade in the seed can be set to 50°,and the swirl intensity is 1.02 to ensure that enough high-temperature flue gas is entrained in the reflux area to make the stable combustion of pulverized coal. The simulation results of boiler combustion process show that the temperature in the middle and upper burner area of the furnace is the highest,and the maximum temperature can reach 1 900 K. The main combustion area is in a state of severe hypoxia. Although severe hypoxia in the main combustion area can reduce the generation of NOx,a large number of reducing gases CO and H2S are generated in the outlet area of the burner,which is easy to cause high-temperature corrosion of the water wall.

0 引言

1 燃烧器及锅炉概况

2 燃烧特性数值模拟

   2.1 燃烧器几何模型及网格划分

   2.2 燃烧模型设置

3 DRB-4Z型燃烧器流场分析

   3.1 基础工况下流场分析

   3.2 一次风风速对流场的影响

   3.3 内二次风风速及旋流强度对流场的影响

   3.4 外二次风风速对流场的影响

4 DRB-4Z燃烧器燃烧特性

   4.1 模拟值与现场测量数据比较

   4.2 温度与流场分布

   4.3 O2分布

   4.4 CO与H2S分布

5 结论