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1 Zeszyty Naukowe. Elektryka / Politechnika Opolska

1 2002

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Blok ograniczeń termicznych turbiny z nowymi algorytmami modelowania naprężeń

Rusin A., Kosman G.

Zeszyty Naukowe. Elektryka / Politechnika Opolska

2002

Vol. 280, z. 51

583-590

W artykule przedstawiono rolę bloków ograniczeń termicznych turbin w procesie uruchamiania bloku. Omówiono nowe algorytmy BOTT oparte o wykorzystania funkcji Greena. Przedstawiono wyniki weryfikacji opracowanych algorytmów dokładnymi obliczeniami numerycznymi.

The paper discusses the application of thermal stress monitoring system in control of steam turbine start-up. New version of the thermal stress monitoring system based on Duhamel's integral is discussed. The algorithm applied enables on line stress control of HP, IP rotors, valves and casings of the turbine. Determination of the state of stresses of thick-walled components may be done by various methods. The most effective ones are finite elements method (FEM) and boundary elements method (BEM). In on-line monitoring and control systems for variable, non-stationary thermal load, these complex numerical calculation techniques (on-line, multiple calculating the inverse problem) not always can be used. Thus other algorithms must be worked out, which would permit on-line calculation of thermal stresses. This paper presents the main assumptions and algorithms of the stress states modelling. Sample results of calculations are also included. The solutions shown above lead to the conclusion that in some cases thermal stresses distribution of arbitrary thick-walled components may be described by formulas, which depend on temperature difference AT or differential coefficient of metal (1). For any non-stationary thermal state, stresses were determined by functions of influence in the form of Green's function and Duhamel's integral. The functions of influence determine the effort of the material per step function, i.e. of the temperature of the medium flowing around the component. Discretizing the continuously changing input function into a sequence of small (within the range of infinitely small) stepwise changes of temperature, we replace a continuous response of the system by a superposition of singular answers (responses). The total stresses in an element may be calculated by integrating the individual responses. The components of the mass stresses, caused by rotors rotation, should be added to the components of thermal stresses calculated above. The surface load of the turbine casing, i.e. the steam or gas pressure, should be also taken into the consideration.