超低负荷工况下汽轮机末级运行特性及其优化机制探索  

Operating characteristics and optimization mechanism of the final stage of steam turbine under ultra-low load conditions

作　　者：彭世亮 王卫良 吕俊复[2,3] 柯希玮 刘志东 马庆中 PENG Shiliang;WANG Weiliang;LYU Junfu;KE Xiwei;LIU Zhidong;MA Qingzhong(MOE Key Lab of Disaster and Control in Engineering,International Energy College(Energy and Electricity Research Center),Jinan University,Zhuhai 519070,China;Key Laboratory of Thermal Science and Power Engineering of the Ministry of Education,Tsinghua University,Beijing 100084,China;Shanxi Research Institute of Huairou Laboratory,Taiyuan 030006,China;Guangdong Zhuhai Jinwan Power Generation Co.,Ltd.,Zhuhai 519050,China;Shanxi Guojin Coal Power Co.,Ltd.,Lüliang 030500,China)

机构地区：[1]暨南大学重大工程灾害与控制教育部重点实验室国际能源学院(能源电力研究中心),广东珠海519070 [2]清华大学热科学与动力工程教育部重点实验室,北京100084 [3]怀柔实验室山西研究院,山西太原030006 [4]广东珠海金湾发电有限公司,广东珠海519050 [5]山西国锦煤电有限公司,山西吕梁030500

出　　处：《热力发电》2024年第6期65-78,共14页Thermal Power Generation

基　　金：珠海市产学研合作项目(2220004003010);“十四五”国家重点研发计划(2022YFB4100805);中国华能集团有限公司总部科技项目“基础能源科技研究专项(三)”(HNKJ22-H105)。

摘　　要：构建以新能源为主体的新型电力系统,对燃煤发电机组深度调峰和超低负荷运行提出了越来越严苛的要求,进而对汽轮机组低负荷安全运行提出了越来越严峻的挑战。采用数值模拟方法,基于低负荷工况下汽轮机末级运行性能的深入分析,着重研究探索了不同解决方案在超低负荷工况下的工作机理与优化效果。研究发现,当机组从中低负荷下降到超低负荷时,末级叶片附近出现间隙涡、回流涡和分离涡等涡群,其范围随着负荷的减小逐渐扩大。低负荷工况降低机组背压和低压缸切缸运行是弱化汽轮机涡流、提高末级性能的有效途径,二者结合使用效果更佳。例如,在20%热耗率验收(THA)工况条件下,将背压从4.9 k Pa降低到2.5 k Pa,使得末级涡群影响范围明显减小,转子叶片转矩从–38 N·m增加到73N·m,末级运行性能明显改善。在10%THA工况下,采用降低背压和低压缸切缸相结合可使叶顶间隙涡完全消失,回流涡和分离涡的径向长度都减小50%以上;优化后的动叶转矩增加了约130 N·m,末级运行性能改善效果显著。Constructing a power system predominantly based on renewable energy sources imposes increasingly stringent demands on deep peak shaving capability and ultra-low-load operation of coal-fired power generating units,thereby presents more severe challenges to the safe operation of steam turbine units under low-load conditions.This paper employs numerical simulation methods,focusing on an in-depth analysis of the operational performance of the last stage of a steam turbine under low-load conditions,and explores various solutions for their working mechanisms and optimization effects under ultra-low-load conditions.It is found that,when the unit transitions from medium-low load to ultra-low load,vortex clusters such as gap vortices,backflow vortices,and separation vortices emerge near the last stage blades,with their extent gradually expanding as the load decreases.Reducing the back pressure of the unit and operating the low-pressure cylinder with cylinder-cutting are effective strategies to attenuate steam turbine vortex flow and enhance the last stage’s performance,with a combined application of these strategies yielding better results.For instance,under 20%turbine heat acceptance(THA)conditions,reducing the back pressure from 4.9 kPa to 2.5 kPa significantly diminishes the influence range of the last stage vortex cluster,increasing the rotor blade torque from−38 N·m to 73 N·m,thereby markedly improves the last stage performance.Under 10%THA conditions,employing a combination of reduced back pressure and low-pressure cylinder-cutting can completely eliminate the tip clearance vortex,with the radial lengths of the backflow vortices and separation vortices reducing by more than 50%.The optimized rotor blade torque increases by approximately 130 N·m,significantly enhancing the last stage performance.

关 键 词：汽轮机 低负荷工况 涡流 背压 切缸 

分 类 号：TM621[电气工程—电力系统及自动化]