以一台 2 0 0MW双背压凝汽式汽轮机组为对象 ,采用分析其相对于单背压凝汽式汽轮机组功率增益变化的方法 ,分析了双背压汽轮机组变工况运行时主要工作参数对机组热效率的影响。指出为了取得最大经济效益及保证机组安全 ,在运行时应根据冷却水温度及凝汽器蒸汽负荷的变化对冷却水流量作相应调整或对机组负荷作相应限制。 Taking a 200MW dual back pressure condensing steam turbine as an example, this paper analyzes the change of power gain relative to single back pressure condensing steam turbine, and analyzes the main work of dual back pressure steam turbine when it is in working condition Effect of Parameters on Unit Thermal Efficiency. It is pointed out that in order to obtain the maximum economic benefit and ensure the safety of the unit, the cooling water flow rate should be adjusted or the corresponding limit to the unit load should be adjusted according to the cooling water temperature and the change of condenser steam load during operation.