不同烟气再循环率燃油超低NO_(x)燃烧器的大涡模拟

Large Eddy Simulation of Ultra-low NO_(x)Burners with Different Flue Gas Recirculation Rates

利用Fluent软件中的大涡模拟方法,对燃油锅炉1/10尺缩模型进行不同烟气再循环率的燃烧过程研究,分析0%,20%和30%烟气再循环率下温度场的分布特点以及污染物的排放特性。模拟结果表明:采用烟气再循环能有效降低锅炉的最高温度、平均温度以及污染物排放水平。其中,20%烟气工况降温最为明显,最高温度相较无烟气工况下降400 K,且随着烟气再循环率的增加,焰型缩短,着火点逐渐向炉膛前部移动,温度梯度减小。相较于0%烟气工况,20%和30%烟气工况的NO_(x)排放浓度分别减少了85.5%和72.7%;20%烟气工况下CO排放水平最低,出口排放浓度为110 mg/m^(3),而30%烟气工况下Soot排放水平最低,出口体积分数为2.14×10_(-5)。

According to the large eddy simulation method in Fluent software,the combustion process of the 1/10 scaling model of oil-fired boiler at different flue gas recirculation rates was studied,and the distribution characteristics of temperature field and pollutant emission characteristics under 0%,20%and 30%flue gas recirculation rates were analyzed.The simulation results show that adopting the flue gas recirculation can effectively reduce the maximum temperature,average temperature and pollutant emission level of the boiler.The temperature drop under 20%flue gas condition is the most obvious,and the maximum temperature is 400 K lower than that under no flue gas condition.With the increase of flue gas recirculation rate,the flame shape is shortened,and the ignition point gradually moves to the front of the furnace,and the temperature gradient decreases.Compared with 0%flue gas condition,the NO_(x)emission concentrations of 20%and 30%flue gas are decreased by 85.5%and 72.7%respectively;the minimum outlet concentration of CO emission level under 20%flue gas condition is 110 mg/m^(3),while the minimum outlet volume fraction of soot emission level under 30%flue gas condition is 2.14×10_(-5).