以1000MW直接空冷机组为例,基于效能—传热单元数方法,建立了直接空冷机组凝汽器变工况数学模型.通过分析排汽管道压降及机组对环境散热量等因素对汽轮机末级排汽压力的影响,得出汽轮机末级排汽压力与环境温度、迎面风速、排汽流量间的关系曲线.分析了汽轮机末级排汽压力与其影响因素之间的线性关系,为1000MW空冷机组在变工况下选择合适的排汽压力和提高经济性提供参考.%Taking 1 000 MW direct air cooling units as an example, by using the method of effective energy-heat transfer units, a mathematical model of direct air cooling units under variable operating conditions has been elaborated. By considering the influence of pressure drop of the exhaust pipe and environment heat dissipation loss on the exhaust steam pressure of the last stage in the steam turbine in direct air cooling units, the curves of condenser pressure change with environment temperature, face velocity and exhaust steam flow were obtained. The linear relationship between the exhaust steam pressure of the last stage and its influence factors was analyzed, which can provide a reference for choosing the suitable exhaust steam pressure and for improving economical efficiency under off-design operation conditions in 1 000 MW air-cooling units.
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