CCPP余热锅炉入口烟道烟气流动的数值模拟研究

Numerical Simulation of Flue Gas Flow in Inlet Flue of CCPP HRSG

燃气-蒸汽联合循环(CCPP)余热锅炉入口过渡烟道连接着燃气轮机与锅炉本体,其结构参数影响着余热锅炉炉内气体流动及换热,进而影响循环机组的效率。以某9F级CCPP系统135 MW的余热锅炉入口烟道为研究对象,利用数值模拟方法针对上仰角及导流板对烟道内部流场的影响进行了研究,分析了气体流动平均速度及流动均匀性。结果表明:当烟道上顶面第1段上仰角α_(1)不变、烟道上顶面第2段上仰角α_(2)减小时,烟道底部高速区范围减小,上部回流区变大,平均速度减小,流动均匀性变差;当α_(1)减小、α_(2)不变时,结论刚好相反。α_(1)=30°,α_(2)=70°的方案为最佳方案,该结构下烟气平均速度较初始方案提高1.87%。导流板设置可以极大增加烟气的平均流速,增加流动均匀性;导流板角度为30°,25°和20°的烟道结构为最佳方案,该烟道内烟气平均速度较原方案提高48.15%。

The inlet transition flue of combined cycle power plant(CCPP)heat recovery steam generator(HRSG)connects the gas turbine and the HRSG body.Its structure parameters affect the gas flow and heat transfer in the HRSG,and then affect the efficiency of the cycle unit.The inlet flue of a 135 MW HRSG in a 9F CCPP system was taken as the research object.Using the numerical simulation method,the influence of elevation angle and deflector on the internal flow field of flue was studied,and the average velocity and flow uniformity of gas flow were analyzed.The results show that when the elevation angleα_(1)of the first section of the upper top surface of the flue is constant and the elevation angleα_(2)of the second section of the upper top surface of the flue is decreased,the range of highspeed zone at the bottom of the flue decreases,the upper recirculation zone increases,the average velocity decreases and the flow uniformity becomes worse;whenα_(1)is decreased andα_(2)is constant,the conclusion is just opposite.The scheme ofα_(1)=30°andα_(2)=70°is the best one,and the average velocity of flue gas in this structure is 1.87%higher than that in the original scheme.The baffles can greatly increase the average velocity of flue gas and increase the flow uniformity;the flue structure with deflector angles of 30°,25°and 20°is the optimal scheme,and the average velocity of flue gas in the flue is 48.15%higher than that in the original scheme.