大型火电机组母管制空冷系统特性
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摘要
为提高大型火电直接空冷机组对气象条件和发电负荷变化的适应能力,提出了一种联建式直接空冷机组母管制冷却系统。建立数学物理模型,对其空气侧流场进行数值模拟,并以此为外部边界条件,开发汽轮机排汽在冷却系统内流动阻力损失和蒸汽流量计算程序。综合考虑外部冷却空气流场和内部蒸汽流动凝结过程,获得夏季和冬季不同环境温度、不同冷却单元投运数量下,各空冷单元的凝结蒸汽流量及汽轮机背压。结果表明,采用母管制冷却系统,在夏季高温环境下冷却一台机组乏汽时,可以显著降低汽轮机背压,提高机组热经济性;冬季环境温度低至??25℃,冷却两台机组乏汽仍可保证汽轮机背压高于阻塞背压,翅片管不发生冻结。
In order to improve the adaptability of the large-scale direct air-cooled power generating units to the variations both of meteorological conditions and power loads, a piping-main scheme of the air-cooled system was proposed for the co-established power generating units. The physicomathematical model of such piping-main air-cooled system was established for the 2???600 MW power generating units,with which the air-side flow characteristics of cooling system were obtained through computational fluid dynamics(CFD)simulation. Taking this as the external boundary condition, the calculating programs both for exhaust steam flow resistance loss and flow distributions inside air-cooled condenser(ACC)cells were developed. Taking the external cooling air flow field and the internal steam flow condensation process into account,the condensate flow rate in ACC cells, as well as the back pressure of turbine can be acquired under different environmental temperatures of summer and winter and different operating ACC cells. The results indicate that the present proposed piping-main scheme of direct air-cooled system for co-established power generating units can reduce the back pressure of the steam turbine significantly and improve the thermal economy of the unit while cooling the exhaust steam of one steam turbine by the whole piping-main cooling system under the summer high ambient temperature. It also can ensure the back pressure higher than block back pressure and the finned tubes do not freeze with the ambient temperature as low as ?25℃ while cooling the exhaust steam of two steam turbines by part ACC cells of the piping-main cooling system during the winter.
In order to improve the adaptability of the large-scale direct air-cooled power generating units to the variations both of meteorological conditions and power loads, a piping-main scheme of the air-cooled system was proposed for the co-established power generating units. The physicomathematical model of such piping-main air-cooled system was established for the 2???600 MW power generating units,with which the air-side flow characteristics of cooling system were obtained through computational fluid dynamics(CFD)simulation. Taking this as the external boundary condition, the calculating programs both for exhaust steam flow resistance loss and flow distributions inside air-cooled condenser(ACC)cells were developed. Taking the external cooling air flow field and the internal steam flow condensation process into account,the condensate flow rate in ACC cells, as well as the back pressure of turbine can be acquired under different environmental temperatures of summer and winter and different operating ACC cells. The results indicate that the present proposed piping-main scheme of direct air-cooled system for co-established power generating units can reduce the back pressure of the steam turbine significantly and improve the thermal economy of the unit while cooling the exhaust steam of one steam turbine by the whole piping-main cooling system under the summer high ambient temperature. It also can ensure the back pressure higher than block back pressure and the finned tubes do not freeze with the ambient temperature as low as ?25℃ while cooling the exhaust steam of two steam turbines by part ACC cells of the piping-main cooling system during the winter.
引文
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[13]杨立军,杜小泽,杨勇平.风场影响下直接空冷系统热风回流率的空间分布特性[J].工程热物理学报,2011,32(7):1181-1184.Yang Lijun,Du Xiaoze,Yang Yongping.Space characteristics of exhaust plume recirculation flow ratios for air-cooled condensers at ambient winds[J].Journal of Engineering Thermophysics,2011,32(7):1181-1184(in Chinese).
[14]王松岭,刘阳,李声强.直接空冷系统排汽管道特性研究[J].应用能源技术,2008(2):26-28.Wang Songling,Liu Yang,Li Shengqiang.Study on characteristics of exhaust piping of direct cooling system[J].Applied Energy Technology,2008(2):26-28(in Chinese).
[15]Haaland S E.Simple and explicit formulas for the friction factor in turbulent pipe flow[J].Journal of Fluids Engineering,1983,105(1):89-90.
[16]华绍曾,杨学宁.实用流体阻力手册[M].国防工业出版社,1985.Hua Shaozeng,Yang Xuening.Practical fluid resistance manual[M].National Defense Industry Press,1985(in Chinese).
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[18]杜小泽,金衍胜,姜剑波.火电厂直接空冷凝汽器传热性能实验研究[J].工程热物理学报,2009,30(1):99-101.Du Xiaoze,Jin Yansheng,Jiang Jianbo.Experimental study on heat transfer performance of direct air-cooled condenser in power plant[J].Journal of Engineering Thermophysics,2009,30(1):99-101(in Chinese).
[19]程通锐.直接空冷机组防冻机理分析[D].北京:华北电力大学(北京),2016.Cheng Tongrui.Research on anti-freezing mechanism of air cooling condenser of large power plant[D].Beijing:North China Electric Power University(Beijing),2013(in Chinese).
[2]Zhang X,Chen H.Effects of windbreak mesh onthermo-flow characteristics of air-cooled steam condenser under windy conditions[J].Applied Thermal Engineering,2015,85:21-32.
[3]Chen L,Yang L,Du X,et al.A novel layout of air-cooled condensers toimprove thermo-flow performances[J].Applied Energy,2016,165:244-259.
[4]Kong Y,Wang W,Huang X,et al.Circularly arranged air-cooled condensers to restrain adverse wind effects[J].Applied Thermal Engineering,2017,124:202-223.
[5]Owen M,Kr?ger D G.Contributors to increased fan inlet temperature at an air-cooled steam condenser[J].Applied Thermal Engineering,2013,50(1):1149-1156.
[6]周振起,袁猛,周楠.直接空冷机组排汽管道流量分配特性数值模拟[J].汽轮机技术,2016,58(1):37-39.Zhou Zhenqi,Yuan Meng,Zhou Nan.Numerical simulation of flow distribution characteristics of exhaust steam duct in direct air cooling unit[J].Turbine Technology,2016,58(1):37-39(in Chinese).
[7]张康,张红霞.直接空冷凝汽器冻结机理与防冻措施[J].汽轮机技术,2008,50(1):52-54.Zhang Kang,Zhang Hongxia.The freezing mechanism and anti-freezing measures for direct air-cooled condensers[J].Turbine Technology,2008,50(1):52-54(in Chinese).
[8]程通锐,杜小泽,杨立军.蒸汽在扁平管内逆流流动凝结实验与理论分析[J].化工学报,2015,66(12):4806-4814.Cheng Tongrui,Du Xiaoze,Yang Lijun.Experimental and theoretical analysis on reflux flow condensation of vapor inside flat tube[J].Journal of Chemical Industry and Engineering,2015,66(12):4806-4814(in Chinese).
[9]邓慧,白焰,李小缤,等.直接空冷岛顺流基管管内冷凝的传热传质分析[J].中国电机工程学报.2015,35(24):6431-6438.Deng Hui,Bai Yan,Li Xiaobin,et al.Analysis for heat and mass transfer of condensation inside down-flow unit tube of air-cooled heat exchanger[J].Proceedings of the CSEE,2015,35(24):6431-6438(in Chinese).
[10]席新铭,宋艳峰,刘赟,等.基于波形翅片扁平管传热性能的直接空冷凝汽器低温冻结规律研究[J].中国电机工程学报,2014,34(26):4493-4499.Xi Xinming,Song Yanfeng Cai yun,et al.Study on freezing characteristics of direct air-cooling condenser based on heat transfer performance of wavy-finned flat tube[J].Proceedings of the CSEE,2014,34(26):4493-4499(in Chinese).
[11]赵晓东.大型直接空冷系统蒸汽流量分配研究及运行策略[D].北京:华北电力大学,2013.Zhao Xiaodong.Research on exhaust steam distribution of large-scale direct air-cooling system and operating control strategy[D].Beijing:North China Electric Power University,2013(in Chinese).
[12]王星,闫宏,孙大伟,等.环境风对空冷风机群运行性能影响的数值模拟研究[J].热力发电,2014,43(6):112-118.Wang Xing,Yan Hong,Sun Dawei.et al.Effect of environmental air on operation performance of the air cooling fan cluster numerical study[J].Thermal Power Generation,2014,43(6):112-118(in Chinese).
[13]杨立军,杜小泽,杨勇平.风场影响下直接空冷系统热风回流率的空间分布特性[J].工程热物理学报,2011,32(7):1181-1184.Yang Lijun,Du Xiaoze,Yang Yongping.Space characteristics of exhaust plume recirculation flow ratios for air-cooled condensers at ambient winds[J].Journal of Engineering Thermophysics,2011,32(7):1181-1184(in Chinese).
[14]王松岭,刘阳,李声强.直接空冷系统排汽管道特性研究[J].应用能源技术,2008(2):26-28.Wang Songling,Liu Yang,Li Shengqiang.Study on characteristics of exhaust piping of direct cooling system[J].Applied Energy Technology,2008(2):26-28(in Chinese).
[15]Haaland S E.Simple and explicit formulas for the friction factor in turbulent pipe flow[J].Journal of Fluids Engineering,1983,105(1):89-90.
[16]华绍曾,杨学宁.实用流体阻力手册[M].国防工业出版社,1985.Hua Shaozeng,Yang Xuening.Practical fluid resistance manual[M].National Defense Industry Press,1985(in Chinese).
[17]Zipfel T.Steam flow distribution in air-cooled condensers[D].Stellenbosch:Stellenbosch University,1996.
[18]杜小泽,金衍胜,姜剑波.火电厂直接空冷凝汽器传热性能实验研究[J].工程热物理学报,2009,30(1):99-101.Du Xiaoze,Jin Yansheng,Jiang Jianbo.Experimental study on heat transfer performance of direct air-cooled condenser in power plant[J].Journal of Engineering Thermophysics,2009,30(1):99-101(in Chinese).
[19]程通锐.直接空冷机组防冻机理分析[D].北京:华北电力大学(北京),2016.Cheng Tongrui.Research on anti-freezing mechanism of air cooling condenser of large power plant[D].Beijing:North China Electric Power University(Beijing),2013(in Chinese).