间接空冷汽轮机组变工况特性研究

以某600MW间接空冷汽轮机组为例，利用EBSILON软件建立了汽轮机和凝汽器模型，结合空冷塔模型完成三者耦合计算，通过正交试验方法研究了多种变工况特性，获得了不同环境温度、循环水流量和机组负荷下背压和热耗率的变化规律。结果表明：机组在相同负荷和循环水流量下，随着环境温度上升，背压和热耗率不断升高，在高温段上升速率明显快于低温段；机组负荷一定，在同样的循环水流量变化幅度下，环境温度越高，背压和热耗率的变化速率越大；在一定环境温度和循环水流量下，随着负荷增大，背压升高，热耗率下降；在机组负荷和循环水流量不变时，空冷塔出口水温上升速率大于环境温度上升速率，在100%循环水流量下，前者为后者的1.11~1.15倍，导致凝汽器进口水温迅速升高，机组运行经济性下降。

Study on Off-Design Performance of Indirect Air-Cooling Steam Turbine Unit

Taking a 600-MW indirect air-cooling steam turbine unit for example, the calculation model of steam turbine, condenser and air-cooling tower is established on the basis of EBSILON software. Characteristics regarding to a variety of operation conditions are studied through the orthogonal test method, such that the variations of back pressure with respect to heat rate under the conditions of different ambient temperatures, circulating water flows and steam turbine loadings are obtained. The results show that, with constant circulating water flow and steam turbine load, as the ambient temperature goes up, the back pressure and the heat rate will keep rising. In particular the increasing rate in the high-temperature section is apparently higher than that in the low-temperature section. If the steam turbine load remains constant, the higher the ambient temperature, the higher the changing rate of the back pressure and the heat consumption rate under the same cyclic water flow. In the case of constant ambient temperature and the circulating water flow, with the raise of steam turbine load, the back pressure will increase while the heat rate will drop down. In the case of constant steam turbine load and circulating water flow, the rising rate of the outlet water temperature for the air-cooling tower is greater than that of the ambient temperature rise. Specifically, the former will be 1.11-1.15 times of the latter if the circulating water flow reaches full volume limit, which will lead to the rapid increase of the inlet water temperature at the condenser and the decline of the system economy performance.