The fatigue damage and failure of steam turbine rotors by torsional vibrations are investigated. Possible causes of the occurrence of torsional vibrations are discussed. Modeling of torsional vibrations of the shafting of a steam turbine, which occur under its operating conditions, has been performed, and the cyclic strength of the shafting under these vibrations has been estimated.The world experience of the long-term operation of turbine units of thermal and nuclear power stations allows the conclusion to be drawn that one of the causes of accidents and catastrophic failures of turbine rotors is fatigue damage accumulation due to torsional vibrations of shafting. This is indicated, e.g., by accidents at a thermal power station in the USA (Tennessee, 1974) [1], at the state district power station-4 at Kashira in Russia (October 2002) [2] and at one of the overhauled power generating units of the Pridneprovskaya thermal power station in Ukraine (2007). In the first case, an accident resulted in the failure of a medium-low pressure rotor ( Fig. 1 shows the lines along which the rotor fractured) and in the second case in the complete failure of the power generating unit No. 3 (K-300-240-1 turbine) and in the partial failure of two neighboring power generating units. Fragments of rotors were found within a radius of several hundreds of meters from the station. In the last case, the turbine had to be urgently stopped because of the occurrence of strong vibration, which prevented it from failure because of a considerable fatigue damage of the rotor, as was found out later. It was concluded from the results of investigations of these accidents that one of the main causes was fatigue of the rotor metal as a result of cyclic torsion.Taking into account the potential hazard of this phenomenon for all steam turbines being in operation, the task was set to evaluate the degree of the fatigue damage of turbine unit shaftings due to torsional vibrations. To perform this task, it is necessary to ascertain the causes of the occurrence of torsional vibrations of shaftings during operation, to model vibrations under the action of operating load and to evaluate the fatigue properties of their materials in operation.The ascertainment of the causes of the occurrence of shafting vibrations made it possible to model structure loading conditions which approached the operating conditions. Since no monitoring of torsional vibrations of turbine rotors is performed at present, the causes of their occurrence can only be conjunctured. The results of a number of theoretical studies [2,3] indicate that the main cause of the occurrence of torsional vibrations of shaftings is the dynamic load acting on the turbine shaft on the turbogenerator side mainly under its abnormal operating conditions, particularly under short-circuit (SC) conditions, at the moments of connection to network with rough synchronization, because of the dynamic instability of the turbogenerator-network system and the nonuniformity of the electric field of the generator, et...
A peculiar feature of the power engineering in Ukraine is a shortage of maneuvering powers; therefore the Nuclear Power Plants available in Ukraine have to use pulverized-coal blocks designed for the basic operation to meet peak loads and for the control on the whole. The current state of power generating equipment was analyzed in compliance with the normative documents approved by the Ministry of Power Engineering and Fuel Industry of Ukraine. The influence of the operation of power units of 200-300 MW in the maneuvering mode has been studied and the predicted residual life in the normal operation mode and in the maneuvering mode of daily start-stop has been calculated. The ageing rate indicators have been calculated and it was established that the equipment aging rate in the maneuvering mode increases three to eight times in comparison with that at the normal operation. It was established that the operation in this mode requires the normative substantiation: the key parameters and criteria of operating conditions should be defined, the software for the technical diagnostics should be introduced, and the additional control (examination) of the technical state of power equipment should be arranged and exercised and the obtained results must be processed. The measures should be taken to provide the safe operation and exercise control over the aging of power plants during the reassigned operation life. Due to this fact and taking into consideration the current state of the equipment the operation in the maneuvering mode in undesirable and requires the development of special normative base, because the available key assets are subjected to a considerable wear.
АННОТАЦИЯ Директива Европейского союза о развитии когенерации до уровня в 10 % от общей выработки электроэнергии определяет развитие централизованного теплоснабжения в крупных городах преимущественным направлением. Для паровых турбин типа Т-100/120-130 разработана математическая модель теплового и напряженно-деформированного состояния. В ходе расчетов, определены максимально нагруженные зоны ротора и значения интенсивностей напряжений в них. Полученные данные позволяют провести оценку малоцикловой усталости и остаточного ресурса основного метала турбины на каждом из пусковых режимов эксплуатации. Ключевые слова: централизованное теплоснабжение, ротор ВД, пуск из холодного состояния, из неостывшего состояния, из горячего состояния, тепловое состояние, напряжённо-деформированное состояние. O. CHERNOUSENKO, V. PESHKO COMPUTATION INVESTIGATION OF THE THERMAL AND STRESS-STRAIN BEHAVIOR OF THE ROTOR OF HIGH PRESSURE TURBINE Т-100/120-130; BLOCK NO 1 OPERATED BY THE PJSC "KHARKIV CHPP-5" ABSTRACT A Directive of the European Union on the cogeneration development to reach a level of 10 % of the total electric power output defines the development of centralized heat supply to large cities by establishing priorities. A mathematical model of thermal and stress-strain behavior was developed for the steam turbines of a Т-100/120-130 type taking into consideration the available damages of designed structures and restoration and repair changes in elements during their operation. The model is based on 3D spatial analogous models used for high pressure rotor. The data of computation investigation include the calculations of thermal and stress-strain behavior of the high pressure rotor of steam turbine Т-100/120-130 of 100 MW; block No 1 operated by the PJSC "Kharkiv CHPP-5". The stress-strain behavior was created during the numerical experiment simulating the influence of high temperatures, working medium pressures, centrifugal forces and also a reaction of supports. The analysis of obtained data allowed us to determine maximally loaded rotor zones for each start mode of the operation, in particular the cold start, warm and hot starts. The values of maximum amplitudes of the stress intensities for the most loaded rotor sections were determined that allowed for the evaluation of low cycle fatigue and the residual resource of the main metal of turbine.
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