Low-pressure Cylinder Research Articles

Steam Turbine Low Pressure Cylinder Last Stage by the Blades Spatial Profiling

Steam Turbine Low Pressure Cylinder Last Stage by the Blades Spatial Profiling

Development of Working Blades From a Titanium Alloy for the Last Steps of a Low Pressure Cylinder for Powerful Steam Turbines

The main design studies of JSC “Turboatom” are highlighted when creating a working blade made of titanium alloy with an active part length of 1200 mm for the last stages of K-1000-60/3000 turbines. It is noted that complex calculations for blades made of titanium alloy for the last stages of the low-pressure cylinder of powerful steam turbines are an urgent task. A three-dimensional calculation of the strength of these blades was carried out, the stress-strain state and displacements at different values of the natural frequency of the blade were determined. The calculation of the bladed disk of the stage of the low pressure cylinder is performed. The dynamic frequencies of natural vibrations are determined for various rotation frequencies of the turbine rotor. A feature of manufacturing technology that provides for the control assembly on the process disk is indicated. The blades made of titanium alloy manufactured by JSC “Turboatom”, considered in this work, are successfully operated on K-1000-60/3000 turbines of the South Ukrainian and Khmelnitsky nuclear power plants.

Development of technologies to increase efficiency and reliability of combined cycle power plant with double-pressure heat recovery steam generator

To increase the efficiency of a combined cycle power plant, it was suggested in a double-pressure heat recovery steam generator to carry out a reheat of water steam that had been spent in a high pressure cylinder of a steam turbine. The researchers introduce a mathematical algorithm and calculation methodology of the waste-heat boiler. It is proved that after re-superheat of water vapour in a double-circuit waste-heat boiler after the high-pressure superheater (with vapour already used in the high-pressure cylinder of a condensing steam turbine), a CHP-plant efficiency and reliability increase. Calculations for the combined cycle gas turbine unit PGU-450 were performed. It is shown that when the reheater is installed in the recovery steam generator, its efficiency increases by 2.15%. At the same time the efficiency of CCGT for power generation is increased by 3.36%, the degree of dry water steam used in the turbine is increased by 0.082. Consequently, the specific consumption of conventional fuel for electric power generation is reduced by 6.1%. Re-superheating of the total flow of water vapour allows to increase CGP-450 steam-gas unit efficiency by increasing the parameters of the steam entering the low-pressure cylinder of the steam turbine.

BASIC APPROACHES TO THE CHOICE OF MATERIAL FOR WORKING BLADES OF THE LAST STAGES OF THE LPC OF POWERFUL STEAM TURBINES

The paper outlines the need for a comprehensive analysis and selection of steels for the working blades of the last stages of low pressure cylinders (LPC) of high-power steam turbines. The authors reviewed the criteria and exist-ing technical requirements for the materials of the working blades. The analysis of various grades of steels for low-pressure cylinder blades was carried out taking into account the experience of their production at JSC “Turboatom”. The proposals on the use of materials of working blades with a large length of the active part are given, as well as ways for further research are outlined.

Research on Modeling and Deep Peak Regulation Control of a Combined Heat and Power Unit

This paper firstly proposes a nonlinear dynamic model of a combined heat and power (CHP) unit with absorption heat pump (AHP) and bypass systems, the unknown parameters are determined based on design data and perturbation test. Simulation results show that the model can reveal the couplings of AHP and bypass systems to the CHP unit, and provide model support for controller design. On the basis of the model, this paper further proposes a deep peak regulation control strategy, in which, the generalized predictive control algorithm with feedforward-feedback structure is adopted to fundamentally solve the control problems of large delay and inertia on the boiler side, and overcome known disturbances on the turbine side; the ratio of the first stage pressure to the exhaust pressure from high pressure cylinder is adopted to control the high pressure bypass. The deep peak regulation process is divided into two stages: 1) CHP and AHP are used for heating when their heating capacity can meet the heat load requirements of residents, 2) as the unit load is further reduced, bypass mode is activated for heating when the steam flow entering the low pressure cylinder is lower than its cooling flow. Simulation results show that the strategy can meet the heat load requirements of residents and ensure the safe and stable operation of the turbine when the unit is in deep peak regulation condition.

Determination of Minimum Flow Rate of Low Pressure Cylinder of Steam Turbine under Deep Peak Load Regulation Conditions

Determination of Minimum Flow Rate of Low Pressure Cylinder of Steam Turbine under Deep Peak Load Regulation Conditions

Increasing the reliability and manoeuvrability of the CCGT when operating in the variable part of the power consumption schedules by switching the CCGT steam turbine to the motor mode

The report is devoted to the problem of increasing the reliability and manoeuvrability of the CCGT when it operates in power control modes of the power system. The generalized results of research on improving the reliability and expanding the adjustment range of the PGU-450 based on the use of bypass steam distribution, reducing the duration of start-up operations and increasing the loading speed of the steam turbine and CCGT in general in the modes of CCGT power reserve during the night load gap by transferring the CCGT steam turbine to the motor mode when the CCGT operates in the condensation mode or in the heating mode according to the GTU-CHP scheme are presented. Additional advantages of the motor mode are noted: improved reliability of the steam turbine due to the elimination of cyclic temperature fluctuations of its steam inlet valves and vibrations in the last stages of the low-pressure cylinder and the possibility of operating the steam turbine generator in the synchronous compensator mode.

A Speed-Governing System Model with Over-Frequency Protection for Nuclear Power Generating Units

Overspeed is more likely to occur in the process of load rejection or large disturbances for nuclear steam turbines due to the large parameter range and low steam parameters, as well as the power of the low-pressure cylinder accounting for a high proportion of the total power. It is of great significance to study the overspeed characteristics of nuclear power plants (NPPs) to ensure the safe and stable operation of the unit and power grid. According to the characteristics of NPPs, the overspeed protection model and the super-acceleration protection model were established, which were added to the speed-governing system model. The response characteristics of the reactor, thermal system, steam turbine and speed-governing system in the process of load rejection or large disturbances of the power grid were analyzed and simulated. The results were compared using the simulation software personal computer transient analyzer (PCTRAN). The simulation results showed that quickly closing both the high and medium pressure regulating valves could effectively realize frequency control when load rejection or a large grid disturbance occurred. The over-acceleration protection cooperates with the super-acceleration protection to avoid the repeated opening/closing of the valves due to overspeed protection. This could effectively reduce the impact of large disturbances on the reactor, thermal system, and turbine.

Experimental Study of the Model Compartment of the Low-Pressure Cylinder of K-320-240 Turbines of JSC "Turboatom"

Experimental Study of the Model Compartment of the Low-Pressure Cylinder of K-320-240 Turbines of JSC "Turboatom"

A Evaluation of the Dynamic Strength of the Shaft Line with Welded Rotors of Low Pressure Cylinders of the K-220-44-1 Turbine

To assess the danger of resonance vibrations, the calculations data of the critical rotational speeds and strength in case of a sudden short circuit in the generator of the shaft line of the upgraded K-220-44-1 turbine unit have been presented. The turbine unit comprising a high-pressure cylinder and two low-pressure cylinders has been in operation at nuclear power plants since the early 1970s. The shaft-line consists of a high-pressure all-forged rotor, two low-pressure welded rotors, an intermediate part and a generator rotor. For the rotors of the turbine unit constituting the shafting, rod models with concentrated masses and elastic-damping support were used. Recommendations on the choice of vertical compliance of supports for computational studies are given. Estimates of the critical speeds of the shafting are obtained without taking into account the lubricant layer of the support bearings. The dynamic state of the shafting is considered for two-phase and three-phase short circuits in the generator. The maximum twisting moments in the rotors' necks under the support bearings are estimated, and the safety factors for the limiting table torque in the plasticity state are determined. The calculations were performed using software packages developed in the A. Podgorny Institute of Mechanical Engineering Problems of NASU, Joint Stock Corporation "Turboatom". The calculation data show that no dangerous resonance vibrations of the shaft-line of the upgraded K-220-44-1 turbine unit are detected and the strength of the shaft-line in case of a sudden short circuit in the generator is in conformity with the requirements of regulatory and technical documents.

The Dynamics of a Rotor System of a 1100 MW Turbine Unit

The calculations data of the critical rotational speeds of the shaft line on yielding supports with the support yield in the vertical and horizontal directions of the modernized turbine unit K-1000-60/1500-2 (after modernization, the turbine unit type is designated as K-1100-60/1500-2M) have been presented. 1000 MW turbine units comprising a high-pressure cylinder and three low-pressure cylinders have been in operation at nuclear power plants since 1984. The design models of shafting are based on technical and improved theories of variable cross-section rods on elastic-damper supports, taking into account the coupling of vibrations in two planes, inertia of rotation, gyroscopic moments and aerodynamic forces on the disks. Additionally, the stress condition of the most dangerous sections of welded rotors has been investigated in case of a sudden short circuit in the generator. The conditions of the shafting for the cases of two- and three-phase short circuits were considered. The calculations of the critical rotational speeds of the shaft line and of the strength of the rotors in case of a short circuit were performed using software packages developed in the IPMash of the NAS of Ukraine, Joint-Stock Corporation “Turboatom”. The calculation data show that no dangerous resonance vibrations of the shaft line of the upgraded К-1100-60/1500-2М turbine unit are detected and the strength of the shaft line in case of a sudden short circuit in the generator is in conformity with the requirements of regulatory and technical documents.

МОДЕЛИРОВАНИЕ И АНАЛИЗ КОЛЕБАНИЙ КОРПУСА ТУРБИНЫ 500 МВт ПРИ СНИЖЕНИИ РАБОЧЕЙ ЧАСТОТЫ

Problem. The problem of increased vibration of bodies of a steam turbine cases with a capacity of steam turbine of 500 М W is considered. The m а in cause of the increased vibration of the steam turbine is the rotor's unbalance and insufficient stiffness of the system elements. The c а se of operating pr а ctice is considered, where the rotational alignment did not significantly change the vibration parameters. Go а l . In this work the purpose was to make simulation of the forced kind of oscillations of the low-pressure cylinders flexible bodies in the turbineunit-foundation-base system with a turbine unit K-500-65/3000 KHTZ, to study the different causes of their increased level of vibration in case of less work frequencies. Methodology . Т he research is made using the method of oscillation, the method of finite elements, as well as the author's methods of constructing models and conducting research on oscillations of the turbineunit-foundation-base system. Res и lts . Т h е results of the research is as follows: a three-dimensional complex finite-element model of the turbine-foundation-base system was obtained, as well as the amplitude-frequency dependences for the points of the cylinder body of low pressure. The conducted study made it possible to draw conclusions about the different causes of increased vibration of the parts of the steam turbine unit flexible bodies. Originality . The type of designed three-dimensional models of the turbine unit-foundation-base system is unique. Due to the features of the developed model, it is possible to make a vibration processes study at a low level that enables to analyze the oscillations of complex system elements. For individual kinds of studies, further unique specification of the individual parts of the considered system is required. This enables to use the features of the finite element method to specify the turbine unit-foundation-base system in accordance with the actual operating conditions. Other researchers did not solve the problem or clarified it. Value to practice. The significance of the work done in practical terms is primarily an illustration of the technique as a tool for developing specific models in the study of oscillations of a turbine-foundation-base system, as well as for solving practical problems of concretizing and localizing the causes of increased vibration of individual elements of a complex system. The results obtained in the work were used to improve the vibration state of the buildings of units with a steam turbine power unit with the capacity of of 500 MW.

Ventilation modes of operation and their representation at the power characteristics of turbine stages and compartments

The article proposes an analysis of the main approaches in the theory of ventilation processes applied to the correct determination of ventilation losses occurring in the stages and compartments of TPP steam turbines in operating modes with low volumetric flow rates in a low-pressure cylinder. The features of the flow of ventilation processes in the low-pressure flow parts of CHP steam turbines and methods of their study are presented. New physical and mathematical models for calculating the ventilation power losses in the flow part of the turbine are considered. The universal generalized mathematical dependence for a high-precision estimation of the ventilation power losses of the turbine compartments is substantiated, taking into account the whole variety of parameters determining the level of these losses. On its basis, the authors have created mathematical models for calculating several types of CHP steam turbines for rapid assessment and accounting of technical and economic indicators of turbine operation all the possible range of operating modes. The basis of the new calculation models is adequate power and flow rate characteristics of the turbine stages and compartments, so the computational results correlate well with the experimental data, allowing to analyze a wide range of operating modes.

Investigation of oscillations of the case of steam turbine with a capacity of 500 MW

Problem. The problem of increased vibration of bodies of a steam turbine with a capacity of 500 MW is considered. The main cause of the increased vibration of the steam turbine is the rotor's unbalance and insufficient stiffness of the system elements. The case of operating practice is considered, where the rotational alignment did not significantly change the vibration parameters. Goal. The purpose of this work was to simulate the forced oscillations of the bodies of low-pressure cylinders in the turbine-foundation-base system with a turbine K-500-65 / 3000 KHTZ, as well as to study the causes of their increased vibration. Methodology. The research was carried out using the method of oscillation, the method of finite elements, as well as author's methods of constructing models and conducting research on oscillations of the turbine-foundation-base system. Results. As a result of the research, a three-dimensional finite-element model of the turbine-foundation-base system was obtained, and the amplitude-frequency dependences for the points of the cylinder body of low pressure were obtained. The conducted study made it possible to draw conclusions about the causes of increased vibration of the upper parts of the bodies of the steam turbine. Originality. The type of developed three-dimensional models of the turbine-foundation-base system is unique. Due to the features of this model, it is possible to study vibration processes at a level that allows you to analyze the vibrations of complex elements of the system. For individual studies, further specification of the individual parts of the system is required. This allows us to use the features of the finite element method to specify the turbine-foundation-base system in accordance with the actual operating conditions. By other researchers, using other methods and approaches, the problem was not solved and the causes of the hanging vibration of the cylinder body of low pressure were clarified. Practical value. The practical significance of the work performed is an illustrative tool for the development of specialized models for investigating forced oscillations of the turbine-foundation-base system, as well as solving a practical problem in analyzing the causes of increased vibration of individual complex elements. The results of the work were used to develop measures to improve the vibration state of power units with steam turbines of 500 MW capacity.

The Application of the Baumann Stage in the Low-Pressure Cylinders of Condensing Turbines

Among the characteristics of the power-generating steam turbines, the specific metal intensity ranks very high. Low-pressure cylinders (LPCs) that use a two-tier Baumann stage have the lowest value of this parameter. The Baumann stage allows a 50% increase in the limit steam passage rate to the condenser without increasing the last-stage blade length and the weight of the turbine. In Russia, such a solution was implemented in the most widely used K-200-12.8 (K-200-130) turbine manufactured by LMZ. However, the experience from operating the turbine and results of investigations into the economic efficiency of the K-200-12.8 turbine have shown that these turbines equipped with the Baumann stage have lower efficiency than similar turbines without the Baumann stage. In the course of subsequent modernization of the K-200-12.8 turbine, the Baumann stage was replaced by a new last stage with longer rotor blades. The design solutions employed by different turbine manufacturers to modernize the K-200-12.8 turbine have been analyzed. It is pointed out that the LPC of this turbine was modernized without analyzing the causes of the low economic efficiency of the basic LPC. An investigation into the real causes of the reduced efficiency of the K-200-12.8 turbine has shown that the LPCs modernized by different companies preserved the drawbacks intrinsic to the basic design. In view of this, a simple variant for modernization of the LPC preserving the Baumann stage is proposed. Its efficiency should not be inferior to the efficiency of modern LPCs whose last stage is equipped with longer blades; a conclusion that is supported by the results of mathematical modeling of the flows in the penultimate- and last-stage nozzle diaphragms of the new LPC.

Restoration of Steam Turbine Last Stage Rotor Blades by Laser Surfacing

Technology is provided for restoring erosion damaged rotor blades of the last stages of steam turbine low-pressure cylinders (LPC) using laser-powder surfacing and application of an erosion-resistant coating. For this method there is typically low heat input into the blade basic metal, which improves its restoration reliability. Results are obtained for comprehensive experimental studies on specimens and blades, confirming the high quality of welded joints obtained by laser surfacing of nickel alloy proposed for restoring the blade profile of blade steels EI961-Sh and 15Kh11MF-Sh, and application of a stellite-6 erosion-resistant coating. The possibility is concluded of using the laser-powder surfacing method during refurbishment of steam turbine LPC rotor blades.

Comparison on CHP Thermo-electric Decoupling Technologies with Heat Pump and Low Pressure Renovation

Thermo-electric decoupling is an effective way to improve the adoption capacity of renewable power of power grids. Therefore, theoretical analysis models are established in this study to evaluate the decoupling performance of CHP with absorption heat pump, compression heat pump and low-pressure turbine renovation. Results show that absorption heat pump, compression heat pump and low pressure cylinder can all expand the feasible operation area and reduce the minimum electricity load rate of the reference CHP plant. When the heat load is 250 MW, The minimal electricity load rate of unit decreases by 12.98%, 56.47% and 36.34% with absorption heat pump, compression heat pump and low-pressure turbine renovation, respectively. The maximal heat-to-electricity ratio of unit is also increased by integration with heat pump and low-pressure renovation. Besides, the compression heat pump has the best decoupling performance among these three decoupling technologies under the same max heating power.

An Automated Flow Traversing Measurement System in the Last Stages of Large-Capacity Steam Turbines

The article presents the results from putting a new automated flow traversing measurement system (AFTMS) in an experimental turbine intended for testing steam paths of the low-pressure cylinders (LPC) of large-capacity steam turbines into use. Modern computerized facilities have been used in developing the system. Such an approach has been implemented for the first time in the full-scale test bench available at PJSC Power Machines in carrying out experimental investigations of an LPC double stage compartment (on a 1 : 1 scale) equipped with a new, ultimately long last stage blade (LSB) developed for a steam turbine plant for ultrasupercritical steam conditions. The investigations were aimed at confirming the effectiveness of the developed system in measuring the flow parameters in the last LPC stage. The necessity of making a shift from nonautomated and semiautomatic systems to the use of automated measurement systems is substantiated. The article describes a system that makes it possible, with automated setting of the gas dynamic probe head position on the traversing line, to determine the steam flow direction; to measure the stagnation pressure, static pressure, and stagnation temperature; and to record the measures indicators with exactly assigned time tags. The results from measurements of flow parameters upstream of the last LPC stage in a partial load mode are given. A comparison between the experimental and calculated flow parameter distribution data over the stage radius in the control section is shown.

Modeling and analysis of 500 MW turbine casing oscillations near basic vertical oscillation

The problem of increased vibration of the most flexible housings of a steam turbine of a power unit of 500 MW is considered. The main cause of the increased vibration of the steam turbine is the unbalance of the rotor and insufficient rigidity of the elements of the system. A case study is considered where the centering of the rotors did not significantly change the vibration parameters. The purpose of this work was to simulate the forced oscillations of low pressure cylinder housings in a turbine-foundation system with a turbine capacity of 500 MW, and to investigate the causes of their increased vibration. The studies were carried out using the oscillation method, the finite element method, as well as the methods developed by the author to construct models and conduct oscillation studies of the turbine-foundation system. As a result of the studies, a three-dimensional finite element model of the turbine-foundation-base system was obtained. The amplitude-frequency dependences for the points of the low-pressure cylinder housings were obtained. The conducted research made it possible to draw conclusions about the causes of increased vibration of the rotors of the steam turbine. The type of developed three-dimensional models of the tour-bin-foundation-base system is unique. Due to the features of this model, it is possible to study the vibrational processes at the level, which allows you to analyze the vibrations of almost all elements of the system. For individual studies, further specification of the parts of the system important for the task is needed. The study made it possible to conclude on the causes of increased vibration of the upper parts of the steam turbine housings. Due to the unique features of the developed model, it is possible to study vibration processes at a level that allows you to analyze the vibrations of complex elements of the system. The practical value of the work carried out is a clear tool for the development of specialized models for the investigation of the forced oscillations of the turbine-foundation-base system, as well as the solution of a practical problem to analyze the causes of increased vibration of individual complex systems of the elements. The results of the realized work were used to develop measures to improve the vibration state and reability of power units with steam turbines with a capacity of 500 MW.

К 100-летию со дня рождения Бориса Михайловича Трояновского

The article is devoted to the scientific and pedagogical activities of B.M. Troyanovskii, Doct. Tech. Sci., Professor of the MPEI Chair of Steam and Gas Turbines named after A.V Shcheglyaev, on the occasion of his 100th anniversary. The article outlines the main results of scientific investigations that determined the development lines of large-capacity steam turbines for thermal and nuclear power plants in Russia and abroad, and the principles of designing the last stages of low-pressure cylinders for large-capacity steam turbines.