当量比对环管型燃烧室内NO_x生成特性影响的研究

Study on the Effect of Equivalent Ratio on NO_x Generation Characteristics in Can-annular Combustion Chamber

采用数值模拟方法研究了当量比对环管型燃烧室内燃烧及NOx生成特性的影响,分析了不同当量比时燃烧室内流场、温度场、热力型NOx生成速率分布、出口温度分布系数（OTDF）及出口NOx浓度的变化。模拟过程中,保持空气量不变,通过调整入口甲烷量来改变当量比。研究表明：增大当量比,燃烧室内燃烧反应速率加快,轴向速度升高,高温区域沿径向扩张,其范围明显扩大,热力型NOx生成速率加快,其高速率范围与高温区域重合,出口NOx浓度上升,而OTDF始终处于合理范围内。因此,在当量比为0.48-0.54范围内,适当降低当量比有利于控制出口NOx浓度。

The effects of equivalence ratio on the combustion and the characteristics of NOx generation in the annular combustion chamber were studied by numerical simulation. The changes of the flow field, tem- perature field, thermal NOx generation rate distribution, OTDF and outlet NOx concentration in the corn- bustion chamber at different equivalence ratios were analyzed. During the simulation, the air flow rate was kept constant, and the equivalence ratio was changed by adjusting the inlet methane amount. The results showed that： by increasing the equivalence ratio, the combustion reaction rate in the combustion chamber is accelerated, resulting in higher axial velocity. The high temperature region is expanded in the radial di- rection ,the range thereof is clearly enlarged. The thermal NOx generation rate is accelerated, and the high rate range coincides well with high temperature of the region. The NOx concentration at the exit increases, and OTDF is always within a reasonable range. Therefore, in the range of the equivalent ratio of 0.48 to 0.54, appropriately lowering the equivalence ratio is favorable for controlling the outlet NOx concentra- tion.