旋流对天然气高温空气燃烧特性影响的数值模拟

以工业炉的高温空气燃烧技术应用为背景，对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器（HCASbumer）中螺旋肋片的旋转角度对燃烧特性的影响，其中湍流采用Reynolds应力模型，气相燃烧模拟采用β函数形式的PDF燃烧模型，采用离散坐标法模拟辐射换热过程，NOx模型为热力型与快速型。计算结果表明，对预热空气采用旋转射流时，能明显降低NOx生成量。对于HCAS型燃烧器，随着空气射流旋转角度的增大，燃烧室内的回流区域增大增强，降低了局部的氧体积分数分布，燃烧室中平均温度和最高温度都有所增加，且燃烬程度大幅度提高，而局部高温区缩小，只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小，后增大。因此，适当调整肋片的旋转角度可以降低NOx生成量。

Numerical Study of the High Temperature Air Combustion in an Industrial Furnace with a Swirling Burner

A numerical simulation was carried out on the high temperature air combustion ofnatural gas in an industrial furnace with a Homocentric Axial Swirling （HCAS） Burner. PDF （Probability Density Function） combustion model based on aβfunction was selected to simulate the gas combustion combined with the Reynolds Stress model to simulate the flow field. The radiation was simulated by a Discrete Ordinates method. The NOx emission was simulated by thermal and prompt NOx model. Numerical results showed the NOx emission was obviously reduced when the preheated air was fed into the furnace with the swirling burner compared to the traditional direct injection burner. For HCAS burner, as the swirling angle of the air jets increased, the recirculation of the hot flue gas and the mixing of the flue gas, fuel and oxygen were both enhanced; low oxygen region enlarged; the local maximum temperature regions reduced and happened only in the small region near the inlet, the flame length decreased and the flame width increased, while the final NOx emission first decreased, then increased with the increase of the swirling angle of the air jets. Therefore NOx emission can be reduced by regulating the swirling angle of the air jets of the burner.