变工况下直接空冷机组最佳真空的分析

为了提高直接空冷机组运行经济性，以冷端系统的变工况模型为基础，通过计算空冷凝汽器风机送风量增大时空冷机组发电功率与对应风机耗功功率的增量，得到直接空冷机组凝汽器最佳真空的确定方法．根据相似定律确定迎面风速对风机耗功的影响，并通过冷端系统数学模型的分析和简化得到机组背压与发电功率的关系，最终导出了不同环境温度和排汽热负荷下迎面风速对应的最佳真空．根据模型对某330Mw机组在变工况下的最佳真空进行了计算，结果表明：随着排汽量的增加或环境温度的升高，最佳真空及对应的风量都增加；当环境温度高于20℃时，环境温度对最佳真空的影响更加突出．

Analysis on Optimum Vacuum of Direct Air-cooled Unit Under Variable Working Conditions

To improve the thermal economy of direct air-cooled power unit, a determination method for op timum vacuum has been developed by calculating the increment of both the unit power generation and the auxiliary power eonsumption based on the variable condition model for eold end system, at rising supply rate of air for condenser. According to the similarity law, the effect of face velocity on fan power consump- tion is determined firstly, then the influence of baek pressure on unit power generation is obtained by ana- lyzing and simplifying the mathematical model of cold end system, and finally the optimum vacuum corre- sponding to various face velocities is deduced at different ambient temperatures and different exhaust steam heat loads. Calculation results on a 330 MW unit show that both the optimum vacuum and corresponding air velocity increase with rising exhaust steam or ambient temperature; the optimum vacuum is greatly af letted by the ambient temperature, when the temperature gets above 20℃.