低压、低氧及快速变工况条件下甲烷/空气扩散燃烧稳定性和NO_x排放的数值模拟研究

Numerical Simulation of CH₄/Air Diffusion Combustion Stability and NNO_x Emission under Low Pressure, Low Oxygen and Rapid Variable Operating Conditions

摘要: 高海拔地区燃气火焰燃烧稳定性是影响锅炉运行效率和安全性的重要因素。通过数值模拟对甲烷在不同海拔高度(0到5500 m)和不同空气流速(±5%、±20%、±40%)下燃气燃烧的火焰稳定性、火焰温度和NO_X排放进行了研究。结果表明：在0 m ≤ H ≤ 5500 m范围内，同一海拔，突然增加空气流速，随着时间变化，火焰燃烧区域逐渐向燃烧器中心线靠拢，火焰高度降低，温度降低，火焰稳定性有所提升，突然降低空气流速会出现相反结果。同一海拔，燃烧室温度和NO_X浓度随空气流速增加而降低，空气流速降低时，燃烧室温度和NO_X浓度增加。随海拔升高，火焰高度随之升高，燃烧温度及NO_X的生成量均下降，火焰稳定性降低。

Abstract: The stability of gas flame combustion in high altitude areas is an important factor affecting the op-eration efficiency and safety of boilers. The flame stability, flame temperature and NO_X emissions of CH₄ combustion at different altitudes (0 to 5500 m) and different air velocities (±5%, ±20%, ±40%) were studied by numerical simulation. The results indicate that within the range of 0 m ≤ H ≤ 5500 m, at the same altitude, a sudden increase in air flow velocity leads, over time, to the gradual con-vergence of the flame combustion area towards the centerline of the burner. This results in a de-crease in flame height and temperature, accompanied by an improvement in flame stability. Con-versely, a sudden decrease in air flow velocity yields opposite outcomes. At the same altitude, the combustion chamber temperature and NO_X concentration decrease with increasing air flow velocity, while they increase as air flow velocity decreases. With an increase in altitude, the flame height also increases, while both combustion temperature and NO_X production decrease, consequently reduc-ing flame stability.