天然气燃料预混水蒸气的燃气轮机低氮燃烧研究

Study on DeNO_x Combustion of Gas Turbine by Natural Gas Premixed With Steam

针对燃气轮机NO_x排放限额日趋严格、天然气气源多样性引起燃烧特性波动等问题,该文基于重型燃气轮机燃烧室进口天然气预混水蒸气对其燃烧特性及NO_x排放特性进行研究。以某在役F型燃气轮机为对象,采用k-ε湍流模型、有限速率/涡团耗散燃烧等模型,通过CFD数值模拟并经现场燃烧调整试验数据验证,结果表明：在额定工况下,值班喷嘴附近温度较高,最高可达约1900K;而主燃烧喷嘴附近温度则较低,最高达约1200K。主燃烧喷嘴进口速度最高可达约40m/s,在出口段燃气速度达到约140m/s。NO浓度（标准状态,15%含氧量）在值班燃烧喷嘴附近可达约335mg/m^3,而主燃烧喷嘴附近明显较低。在天然气预混入水蒸气后,当水蒸气预混比从R_f=0增大至Rf=0.5时,出口燃气平均流速从125.3m/s下降为121.5m/s,燃气平均温度从1606K降到1594K。燃烧室出口NO的平均浓度从R_f=0的24.94mg/m^3逐渐下降到R_f=0.5的11.79mg/m^3。同时也会带来燃气速度受影响、火焰长度变长等不利的结果。

Gas turbine power plants are confronted with the tougher NO_x emission standards,and fluctuations in combustion characteristics resulted from gas source diversity.This paper studied the combustion characteristics and NO_x emission in the case of an in-service F class heavy-duty gas turbine fired by natural gas premixed with steam.Based on K-ε turbulence model and finite/Eddy-Dissipation combustion model,CFD numerical simulation was carried out and validated by the field combustion adjustment data.The results show that： at the rated power load,gas temperature near the pilot nozzle is as high as about 1900 K; and gas temperature near the main combustion nozzles is as low as about 1200 K; the gas velocity of the main combustion nozzle inlet is up to 40 m/s,while 140 m/s in the outlet section.The NO concentration at standard condition and 15% O_2 reaches about 335 mg/m^3 near the pilot combustion nozzle,while it is significantly lower near the main combustion nozzles.In the case of natural gas premixed with steam,when the steam premixed ratio increases from R_f = 0 to R_f = 0.5,the flue gas average velocity decreases from 125.3 m/s to 121.5 m/s,and the average temperature decreases from 1606 K to 1594 K.NO average concentration of the combustion chamber outlet gradually decreases from 24.94 mg/m^3 at R_f = 0 to 11.79 mg/m^3 at R_f = 0.5.At the same time,some adverse effects are produced,for example,the gas velocity is affected,the flame length becomes longer.