The low and variable load regimes of steam turbines have become a highly topical issue in recent times. Steam turbines frequently balance fluctuations in the power grid or operate with a heat source that has variable parameters, such as waste incineration plants. In such cases, the steam can have wetness content locally up to 19 %. During operation with variable output, compression, heating, and the formation of vibrations occur in the tips of the last stage rotating blades. Steam flows only through a portion of the available cross-section, while the remainder flows in reverse. Under such conditions, it is necessary to cool the exhaust section of the turbine. This paper describes contemporary knowledge regarding the behaviour of the steam flow and tip vibrations of rotating blades across various operating regimes. The flow parameters are monitored using pneumatic probes and local pressure and temperature measurements, while the vibration amplitudes are measured using the blade tip-timing method.
Hoznedl et al. (Fri,) studied this question.