二次再热BEST机组变工况热力性能及贡献度分析  

Analysis of Thermodynamic Performance and Contribution of a Double-reheat BEST Unit under Variable Working Conditions

作　　者：朱梓傲 叶学民[1] 刘迪[1] 李春曦[1] ZHU Ziao;YE Xuemin;LIU Di;LI Chunxi(Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology,North China Electric Power University,Baoding,China,Post Code:071003)

机构地区：[1]华北电力大学河北省低碳高效发电技术重点实验室,河北保定071003

出　　处：《热能动力工程》2024年第8期94-103,共10页Journal of Engineering for Thermal Energy and Power

摘　　要：为了解决主蒸汽参数提高后回热抽汽过热度和热损失增大的问题,以某二次再热超临界机组为原型,搭建了BEST热力系统模型,建立了机组热经济性模型,比较了传统机组和BEST机组中各加热器的[火用]效率及热效率随机组发电量的变化,分析了锅炉给水、主蒸汽轮机和小汽轮机对BEST机组节能效果的贡献度,并讨论了小汽轮机抽汽加热给水方式对机组节能潜力的影响。结果表明:BEST设计方案显著降低了加热器[火用]损并优化了锅炉给水,是提高机组热效率的主要因素,但汽轮机一、二次再热蒸汽量降低造成主汽轮机做功减少,削弱了机组节能效果;小汽轮机可抵消该削弱作用,且其具备对机组热效率贡献随机组发电量降低而升高的特性,保障了机组低发电量下的节能效果。In order to solve the problem of increased superheat degree and heat loss in the regenerative extraction steam after the main steam parameters were increased,taking a double-reheat supercritical unit as a prototype,a thermal system model for a back pressure extraction steam turbine(BEST)unit and a thermos-economics model were established,and the changes of thermal efficiency and exergy efficiency with loads of each heater for a traditional unit and BEST unit were compared.The contribution of boiler feedwater,main steam turbine and auxiliary steam turbine to the energy-saving effect of BEST unit was analyzed,and the impact of auxiliary steam turbine extraction and heating feedwater on the energy-saving potential was discussed.The results indicate that the BEST design scheme significantly reduces heater exergy losses and optimizes boiler feedwater,which is the main factor in improving the thermal efficiency.However,a reduction in primary/secondary reheated steam flowrate decreases the output of the main turbine and weakens the energy-saving effect of the unit.The weakening effect can be offset by the auxiliary steam turbine.The contribution of auxiliary steam turbine to the thermal efficiency of BEST unit increases with decreasing unit load,thereby ensuring the energy-saving effect of the unit at low loads.

关 键 词：背压抽汽式汽轮机 二次再热 汽轮机热耗率 [火用]效率 

分 类 号：TK221[动力工程及工程热物理—动力机械及工程]