Determining the Idle Mode of the Last Stages of Powerful Steam Turbines for Wet Steam Area

Increasingly, low-capacity electricity generating installations using renewable energy sources are becoming widespread. They bring imbalance to the energy system. Frequency control is carried out using powerful steam turbines. To ensure reliable and efficient operation of powerful steam turbines, it is important to understand the processes occurring in the last stages of the low-pressure cylinder. At present, there is no approach to determining the idle mode (the moment of transition from the generation of mechanical power to its consumption) for large fanning stages. The purpose of the work is to develop an approach to estimating the relative volumetric steam flow rate of steam for large fanning stages, which characterizes the idle mode. This goal is achieved by developing a dependence to determine the idle mode for large fanning stages at nominal operating mode in a compressible medium using the results of an experimental study of model stages for high power turbines. The most important result is the satisfactory agreement between the values of volume flow rate obtained during the calculation, using the proposed method, with experimentally studies for the T-250/300-240 turbine last stage. The calculation error is about 3%. The significance of the results obtained is that the proposed approach allows determining the idle mode of the low-pressure cylinder stages of steam turbines quickly and ac-curately during operation and design, which makes it possible to increase the efficiency and reli-ability of power units.