超低负荷工况下大功率汽轮机低压缸内温度场分布特性研究  

Research on Temperature Distribution Characteristics in Low Pressure Cylinder of Large Steam Turbine Under Ultra-low Load Conditions

作　　者：曹丽华[1] 李禹 司和勇 CAO Lihua;LI Yu;SI Heyong(School of Energy and Power Engineering,Northeast Electric Power University,Jilin 132012,Jilin Province,China)

机构地区：[1]东北电力大学能源与动力工程学院,吉林省吉林市132012

出　　处：《中国电机工程学报》2021年第3期1018-1025,共8页Proceedings of the CSEE

基　　金：国家重点研发计划项目(2017YFB0902100)。

摘　　要：超低负荷下,汽轮机低压缸内的温度分布情况直接影响汽轮机的安全运行。为了更加清晰地分析蒸汽在低压缸内的温度分布特性,采用非平衡凝结流动模型、SST k-ω湍流模型对某300MW汽轮机极低负荷工况下的低压缸流场进行数值模拟,分析了整个低压缸内蒸汽流动特性、做功能力、温度分布以及近零功率时冷却蒸汽参数变化对温度场的影响。结果表明:汽轮机在30%机组热耗验收工况(turbine heat acceptance,THA)时,末级动叶根部出现了回流。在20%THA左右时,末级已经出现了鼓风现象,动静叶顶部出现漩涡,温度明显上升,且此时末级做功为负功率输出。在近零工况下时,低压缸排汽温度与冷却蒸汽流量和冷却蒸汽温度呈线性变化趋势,与冷却蒸汽流量负相关,与冷却蒸汽温度正相关,因此需设置合理的冷却蒸汽流量和温度来控制末两级叶片的出口温度。研究成果可为超低负荷工况下汽轮机的运行提供参考。Under the ultra-low load condition, the temperature distribution in the low pressure cylinder has the direct influence to the safety of steam turbine. In order to study the distribution of temperature field of the whole low pressure cylinder, the numerical simulation was used to calculate the flow field of low pressure cylinder in this paper by the nonequilibrium condensation flow model and SST k-ω turbulence model. The characteristics of flow field, power output, temperature distribution and the influence of cooling steam parameters on the temperature field at near zero power condition of low pressure cylinder were analyzed. Results show that there is a back flow vortex at the diffuser at 30% turbine heat acceptance(THA) condition. The tip clearance vortex appears at the upper span between the last stator blade and the last rotor blade at 20% THA condition and the temperature increases significantly, which is called the "windage" phenomenon and the last stage produces a negative power output contribution. At near zero power conditions, the exhaust temperature of low pressure cylinder is linear with the flow rate and the temperature of cooling steam. It is negatively related to the cooling steam flow rate and positively correlated with the cooling steam temperature. Therefore, the outlet temperature of the last two stage blades can be effectively controlled by setting the cooling steam flow rate and temperature reasonably. The research results can provide reference for the operation of steam turbine under ultra-low load conditions.

关 键 词：汽轮机 低压缸 超低负荷 温度分布 

分 类 号：TM62[电气工程—电力系统及自动化]