The paper considers torsional vibrations of turbine shaftings under sudden generator rotor loadings, which are caused by two-and three-phase short circuit. The fatigue damageability of shaftings under the most unfavorable loading conditions has been assessed.Introduction. An important problem of modern turbine manufacture is ensuring the strength of the turboset elements in operation under different conditions. One of the causes of shafting failures can be fatigue damage accumulation due to strong torsional vibrations [1,2], which are most often caused by actions on the generator side. In this case, a considerable dynamic load arises under extraordinary generator operation conditions [short circuits (SC), switching into a network with rough synchronization, quick reswitching after the cessation of the action of short circuit, etc.]. On short circuits, the generator rotor is acted upon by considerable electromagnetic torques for 0.01-0.265 s [3,4], which exceed the nominal moment by a factor of 8-10 in the most unfavorable cases.The effect of torsional vibrations of shafting, which arise under extraordinary turbogenerator operation conditions, on the strength of steam turbine rotors was considered in [5][6][7]. The investigations of transient processes were carried out numerically for the shafting of a 200 MW steam turbine. The degree of its fatigue damageability due to torsional vibrations was assessed. In [5], a three-dimensional finite element model of shafting was employed without regard for the influence of the generator rotor in the case of loading with a short rectangular pulse, which exceeds the nominal moment by a factor of six. In [6,7], the fatigue damageability due to torsional vibrations was assessed numerically with the aid of a simplified discrete model of shafting with four localized masses, which had moments of inertia and were connected by elastic elements. The effect of the parameters and form of torque burst on the degree of damageability of the shafting material was studied. Besides rectangular pulse, other forms of short-circuit moment were considered [8]. The possibility of fatigue damage accumulation in the turbine shaft during long operation, reaching the limit state of turbine and, as a consequence, its failure were shown. The above papers point out that the torsional vibrations of the turbine shaft which arise in extraordinary situations depend on the time of reactive moment action, which is accidental.Taking into account the diversity of extraordinary operating conditions, under which the generator rotor undergoes rapid changes in torque, the ambiguity of the conclusions drawn about their effect on the life of shaftings and the dependence of results on their dynamic and strength properties, further investigations of these subjects appear to be topical.
621.165:539.4 and N. G. GarmashWe present the results of numerical analyses (in the three-dimensional statement) of the kinetics of stressed state and accumulation of dispersed defects in the zone of discharge holes in the rotor disks of a steam turbine in creep for 400,000 h . It is shown that the zones of discharge holes in the disks of the first two stages suffer the action of the highest stresses and the material in these zones is damaged more intensely that near the surface of the axial channel.Keywords: rotor, discharge holes, creep, damage to the material, long-term strength.Parallel with the surface of the axial channel, disk fillets, fillets of the root joints, and temperaturecompensating grooves of the end and diaphragm seals, the zones of discharge holes in the disks of the first two stages of solid-forged rotors of high-pressure (HPC) and medium-pressure cylinders (MPC) of steam turbines are regarded as the most critical sites from the viewpoint of exhaustion of their service life. Indeed, the rotors are most often damaged just at these sites [1,2]. In view of the severe consequences of possible failures, the high-temperature zone of the axial channel proves to be especially dangerous. In estimating the service life of rotors, special attention is given to the temperature-compensating grooves and disk fillets because, in these zones, the metal operates under severe conditions and is damaged as a result of both creep and thermal fatigue in the nonstationary modes. In the branch standard [3] regulating the numerical analyses of the total and residual service life of the rotors of steam turbines, the zone of discharge holes is neglected.The analysis of the accumulated numerical results shows that, near the surface of the axial channel, in the zones of discharge holes and in the rims of disks at the sites of steam inlet, the defects are mainly accumulated according to the mechanism of creep in the stationary modes of operation. In these zones, it is reasonable to determine the long-term static strength according to the branch standards [4,5] in which the safety margins are specified for the computed nominal equivalent stresses relative to the long-term ultimate strength.Among highly stressed zones of the rotors, the zone of discharge holes remains studied quite poorly. In finding the stress-strain state (SSS), the discharge holes are regarded as stress concentrators. Moreover, it is recommended [4] to determine local stresses for these holes by using the nominal hoop and radial stresses obtained from the solution of the plane problem of thermoelasticity for disks or the values determined from the solution of the axisymmetric problem and averaged over the thickness. In this case, according to [3], it is recommended to decrease the safety margin for long-term strength n lt from 1.5 to 1.35 (by 10%).In [6], the long-term strength of the medium-pressure rotor of a K-300-240 LMZ turbine was studied in the zone of discharge hole in the disk of the first stage (T =°525 C) according to the recommendations mad...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.