1 000 MW机组不同BEST级数下变工况回热特性研究

为了寻找抽汽背压式汽轮机(back pressure extraction steam turbine,BEST)最佳的级数方案,以配置BEST的二次再热机组为设计基础,保持总回热级数不变,BEST级数从4级增加到8级,对比不同BEST级数下机组的可行性、变工况特性及热经济性.结果表明:从BEST功率相对给水泵功率的裕...

Research on Regenerative Characteristics of 1 000 MW Units at Different BEST Stages under Variable Operating Conditions

In order to find the optimal stages scheme of back pressure extraction steam turbine (BEST), based on the design of the secondary reheat unit equipped with BEST, keeping the total number of regenerative stages unchanged, the number of BEST stages was increased from 4 to 8, and the feasibility, variable working condition characteristics and thermal economy of the unit under different BEST stages were compared. The results show that from the perspective of the margin of the BEST power relative to the feedwater pump power, when the number of BEST stages is equal to 4 and under the condition of the unit load of 100% to 75% THA, the BEST power cannot meet the power demand of the feedwater pump.A feasible solution selects the number of BEST stages to increase from 5 to 8. For every additional stage of BEST, the average margin of BEST power relative to feedwater pump power will increase by 5 to 7 MW; For extraction pressure, when the load decreases, the extraction pressure in front of the deaerator where BEST is located decreases with the increase of the number of BEST stages, and the extraction pressure behind the deaerator where BEST is located increases with the increase of the number of BEST stages;For the extraction steam flow, when the load decreases, the first stage extraction steam flow increases with the increase of the number of BEST stages, the extraction steam flow in front of the deaerator where BEST is located decreases with the increase of the number of BEST stages, the extraction steam flow behind the deaerator increases with the increase of the number of BEST stages; From the perspective of thermal economy, as the number of BEST stages increases, the heat consumption rate of the unit also increases. The 5 stage BEST solution is the best solution for the thermal economy of the unit.