Izvestiâ Vysših Učebnyh Zavedenij i Ènergetičeskih ob Edinennij SNG. Ènergetika (Oct 2015)
FUNDAMENTALS OF THE THEORY OF VENTILLATION PROCESSES IN THE STEAM TURBINES TPP
Abstract
The article proposes the theoretical framework of ventilation processes emerging and going on in the stages of TPP steam turbines during the operating regimes with small-quantity volumetric flow rates in the low-pressure cylinder. The basic theory includes new physicomathematical models for estimating the ventilating capacity losses and ventilation heatings-up of the steam and the air-gas channel of the turbine; search and investigation of the factors causing the increased momental loads on the blade wheels of the finale stages which are likely to lead to destruction of the rotating blades. The paper renders the practical results of utilizing the theoretical framework of ventilation processes.The author obtains a new mathematical relation for high-accuracy assessment of the ventilating capacity losses accounting for all the diversification of parameters defining the level of these losses (it is established that the Coriolis force contributes twice as much to the ventilating capacity losses as the centrifugal force). Seven ordinary formulae obtained on its basis provide a separate stage ventilation-losses immediate evaluation (with rotation blades of the finale stage not unwinding from the turning, with rotation blades of the finale and intermediate stages unwinding from the turning), in the turbine altogether-vapor-evacuated including by readings of the regular instruments located at the connecters of the exhaust part of the lowpressure cylinder.As the cornerstone of the new ventilation heating-up evaluation system the author lays two experimentally established facts: the ventilating capacity losses are practically constant at working steam negligible volumetric flow rates; symmetrical ventilating flows in the blade channel mingle entirely to the moment of their split up at the periphery. This renders possible estimating the complete enthalpy increment of the steam being discharged from a stage in relation to the enthalpy of the steam being drawn into the blade channel of the blade wheel out of the vapor space of the condenser. The research establishes and acknowledges the influence of a wide spectrum of parameters on the ventilating capacity losses level and ventilation heatings-up in a turbine stage, indicates the measures for them. The estimation results of ventilating losses and ventilation heatings-up are close to the experimental findings of different researchers.
