Turbine Cogeneration Research Articles

On the feasibility and possibility of heating water for district heating systems through the use of heat of the main condensate after cogeneration turbines

The possibilities of increasing the efficiency of cogeneration turbines of CHP plants through the use of low-potential heat carriers for water heating in district heat supply systems and increasing the generation of CHP electricity are considered. The existing technologies of heating the makeup water of the district heating system upstream water treatment apparatuses do not always provide the required heating temperature and do not have the sufficient energy efficiency. The technologies of using the main condensate of the exhaust steam in the turbine to heat the feed water in additional heaters included in the system of regeneration of cogeneration turbines are developed. The use of these technologies contributes to increasing the flow rate and reducing the enthalpy of the steam of regenerative outlets of the turbine used to heat this condensate, and, therefore, increases the combined heat and power generation. In order to determine the industrial applicability of the proposed solutions, experimental studies of the regeneration systems of turbo-units under the conditions of Ulyanovsk СHPPs-1 have been carried out. Multiparameter data arrays on operation of turbine condensate-feed path have been collected, and regression equations have been obtained to calculate the main condensate flow temperatures depending on various factors. On the basis of experimental data there have been calculated the minimum and maximum flow rates of feed water that can be heated to the desired temperature in the surface heaters included in the regeneration system of the turbines, the flow graphs of the heated feed water are constructed depending on the temperature of the main condensate after the turbines. The fields of application of the proposed technological solutions in operating heat supply systems are defined. The evaluation of energy efficiency is carried out using the method of specific generation of CHP electricity and conventional fuel economy at the implementation of the proposed solutions is calculated.

Efficiency Optimisation of Blade Shape in Steam and ORC Turbines

Abstract This paper is devoted to direct constrained optimisation of blading systems of large power and small power turbines so as to increase their internal efficiency. The optimisation is carried out using hybrid stochastic-deterministic methods such as a combination of a direct search method of Hooke-Jeeves and simulated annealing or a combination of a bat algorithm and simplex method of Nelder-Mead. Among free shape parameters are blade number and stagger angle, stacking blade line parameters and blade section (profile) parameters. One practical example of efficiency optimisation of turbine blading systems is modification of low load profiles PLK-R2 for high pressure (HP) stages of large power steam turbines. Another optimised geometry is that of an ORC radial-axial cogeneration turbine of 50 kWe. Up to 1% efficiency increase can easily be obtained from optimisation of HP blade profiles, especially by making the rotor blade more aft-loaded and reducing the intensity of endwall flows. Almost 2% efficiency rise was obtained for the optimised 50 kWe ORC turbine due to flow improvement at the suction side of the blade.

Estimating the Low-Cycle Fatigue, Damageability and the Residual Life of the Rotor of High Pressure Turbine Т-100/120-130 unit No 1 used by PJSC "Kharkiv CHPP-5

The development of centralized heat supply for large cities requires the estimation of the individual life of each cogeneration power unit that reached the economic life. To extend the service life of the cogeneration turbine Т-100/120-130 unit No 1 used by PJSC Kharkiv CHPP-5 we analyzed the individual service life using the integrated approach. This approach combines the data of destructive and nondestructive metal examination with the strength and longevity verification computations and the detailed studies of each individual history of the unit operation. Based on the 3D spatial analogue of high pressure rotor and numerical experiment data on the estimation of thermal and stress-strain behavior the damageability of basic metal has been calculated. In the course of the estimation of low-cycle fatigue of high pressure rotor the values of the reduced amplitude of the strain intensity for the most loaded rotor sections were established. When determining the permissible number of start cycles in different thermal states the metal safety factors were experimentally calculated. The computations done showed that a degree of the wear of basic metal makes up 69 %. The metal examination data analysis for the high pressure rotor over the entire operation period is indicative of its satisfactory condition and together with the computation data allows for the extension of the service life of high pressure rotor by 50000 hours and a number of the starts should not exceed 558 starts.

Increasing the Operation Efficiency of Low Pressure Cylinders of Cogeneration Turbines

An increase in the operation efficiency of cogeneration turbines used by big heat and power plants is conditioned by the need of a maximum use of the fuel heat, mainly that of natural gas. The generation of two types of energy, in particular electric and thermal by cogeneration turbines for outside consumers is closely related to turbine operation modes and first of all to those for low pressure section in which the permanent heat loss occurs. The purpose of this research was to analyze the operation of low pressure cylinders used by operating cogeneration turbines of Т-100/120-130 and Т-250/300-240 types in a wide range of changes in electric and thermal loads. At high heat consumption according to the thermal schedule and low steam rate in the LPC the cascades of it operate consuming power at high ventilation losses. The joint operation of supply line heaters and low pressure cylinders was analyzed using the method of mathematical simulation of the turbine unit, experimental investigation of the models of LPC cascades and full-scale test data of cogeneration turbines built by different organizations. The relationships for the determination of power losses by LPC cascades when operating in low rate modes and additional generation of electric power by the turbine with the rational distribution of thermal load between the supply-line heaters have been given. It has been shown that the choice of heat release mode by the turbine unit can be defined by the optimization problem that requires the comparative estimation of power losses in the LPC and a gain in electric power due to the rational distribution of thermal load between the supply-line heaters.

Concept of turbines for ultrasupercritical, supercritical, and subcritical steam conditions

The article describes the design features of condensing turbines for ultrasupercritical initial steam conditions (USSC) and large-capacity cogeneration turbines for super- and subcritical steam conditions having increased steam extractions for district heating purposes. For improving the efficiency and reliability indicators of USSC turbines, it is proposed to use forced cooling of the head high-temperature thermally stressed parts of the high- and intermediate-pressure rotors, reaction-type blades of the high-pressure cylinder (HPC) and at least the first stages of the intermediate-pressure cylinder (IPC), the double-wall HPC casing with narrow flanges of its horizontal joints, a rigid HPC rotor, an extended system of regenerative steam extractions without using extractions from the HPC flow path, and the low-pressure cylinder’s inner casing moving in accordance with the IPC thermal expansions. For cogeneration turbines, it is proposed to shift the upper district heating extraction (or its significant part) to the feedwater pump turbine, which will make it possible to improve the turbine plant efficiency and arrange both district heating extractions in the IPC. In addition, in the case of using a disengaging coupling or precision conical bolts in the coupling, this solution will make it possible to disconnect the LPC in shifting the turbine to operate in the cogeneration mode. The article points out the need to intensify turbine development efforts with the use of modern methods for improving their efficiency and reliability involving, in particular, the use of relatively short 3D blades, last stages fitted with longer rotor blades, evaporation techniques for removing moisture in the last-stage diaphragm, and LPC rotor blades with radial grooves on their leading edges.

Environmental aspects of thermal power equipment operation modes optimization

The article deals with development of methods for improving the efficiency of power generation in thermal power plants by means of main equipment operating mode optimization. The technique for efficient load distribution between cogeneration turbines for cogeneration of heat and electricity is introduced. The calculated fuel consumption corresponds to the optimal operating modes of turbines. The environmental aspects of optimization method have been considered. The economic effect from implementation of proposed technical solutions has been calculated. For more significant reduction of toxic compounds, generated in boiler furnace, the use of thermal effect from combustion of the hydrogen formed during the decomposition of the damp water, metered into the combustion chamber at temperature 1100 °C is introduced. The use of hydrogen additive as a source of additional stored energy due to combustion in the combustion device, expands the scope of its application in a power system significantly and provides normal emissions of toxic compounds into the air. The use of hydrogen additive in combustion refers to the best available techniques, implementation of which allows increasing the competitiveness of Russian energy production.

Cogeneration steam turbines from Siemens: New solutions

The Enhanced Platform system intended for the design and manufacture of Siemens AG turbines is presented. It combines organizational and production measures allowing the production of various types of steam-turbine units with a power of up to 250 MWel from standard components. The Enhanced Platform designs feature higher efficiency, improved reliability, better flexibility, longer overhaul intervals, and lower production costs. The design features of SST-700 and SST-900 steam turbines are outlined. The SST-700 turbine is used in backpressure steam-turbine units (STU) or as a high-pressure cylinder in a two-cylinder condensing turbine with steam reheat. The design of an SST-700 single-cylinder turbine with a casing without horizontal split featuring better flexibility of the turbine unit is presented. An SST-900 turbine can be used as a combined IP and LP cylinder (IPLPC) in steam-turbine or combined-cycle power units with steam reheat. The arrangements of a turbine unit based on a combination of SST-700 and SST-900 turbines or SST-500 and SST-800 turbines are presented. Examples of this combination include, respectively, PGU-410 combinedcycle units (CCU) with a condensing turbine and PGU-420 CCUs with a cogeneration turbine. The main equipment items of a PGU-410 CCU comprise an SGT5-4000F gas-turbine unit (GTU) and STU consisting of SST-700 and SST-900RH steam turbines. The steam-turbine section of a PGU-420 cogeneration power unit has a single-shaft turbine unit with two SST-800 turbines and one SST-500 turbine giving a power output of Nel. STU = 150 MW under condensing conditions.

ON TORSIONAL OSCILLATIONS OF SHAFT TRAINS OF POWERFUL STEAM TURBINE UNITS UNDER OPERATING CONDITIONS

The problem of massive damageability of low pressure rotors of cogeneration turbines of types T-175 and PT-135 is considered. The hypotheses of crack formation in low-temperature rotors of steam turbines under the action of bending and torsional oscillations are compared. Based on the analysis of a variety of factors, including those of structural and operational nature, it is shown that there are a number of prerequisites that make the second of the hypotheses considered somewhat more preferable. However, the eff ects of torsional oscillations can only be estimated on the basis of the results of experimental studies of dynamic stresses in rotors on real turbine generating units under operating conditions. This required the development and creation of a multichannel control and monitoring system for torsional oscillations of the shaft train of turbine units, its pilot-industrial version implemented on the T-175/210-130 turbine generator unit. Based on the calculations performed out and the analysis of the causes of both the intrinsic and forced torsional oscillations of the shaft train, the requirements were formulated that must be imposed to recording the parameters of torsional oscillations and, what is especially important, for algorithms and software for processing data and presenting the results. It is shown that in most of the published studies only intrinsic torsional oscillations of the shaft trains are given. Typical mistakes are analyzed, and it is shown that the forced oscillations which are multiples of the rotation frequency could not be obtained with the data processing algorithms used, and that conclusions based on such studies are untenable. Moreover, in most cases, using source data not subjected to necessary pre-adjustment prior to using the same in the Fourier transform may cause signifi cant distortion of the analysis results. The methods of measurement, preparation and processing of data suggested in the paper enable to record both intrinsic and forced torsional oscillations of shaft train. The results of studies are presented that have shown that forced torsional oscillations multiple to rotation speed are mostly implemented in the shaft train. Further ways of improving the created system are provided.

Cogeneration turbine unit with a new T-295/335-23.5 steam turbine

The design, schematics, and arrangement of a T-295/335-23.5 turbine and the basic features of a steam-turbine unit (STU) intended for replacement of STUs with a T-250/300-23.5 turbine with the expired service life and installed in large cities, such as Moscow, St. Petersburg, Kiev, Minsk, and Kharkov, for heat and power generation are considered. The basic solutions for an automatic electrohydraulic control and protection system using high-pressure (HP) technology are described. As the turbine operates in a power unit together with a supercritical boiler and the design turbine service life of 250000 hours must be attained, turbine component construction materials complying with these requirements are listed.

Substantiation of the cogeneration turbine unit selection for reconstruction of power units with a T-250/300-23.5 turbine

The selection of a cogeneration steam turbine unit (STU) for the reconstruction of power units with a T-250/300-23.5 turbine is substantiated by the example of power unit no. 9 at the cogeneration power station no. 22 (TETs-22) of Mosenergo Company. Series T-250 steam turbines have been developed for combined heat and power generation. A total of 31 turbines were manufactured. By the end of 2015, the total operation time of prototype power units with the T-250/300-23.5 turbine exceeded 290000 hours. Considering the expiry of the service life, the decision was made that the reconstruction of the power unit at st. no. 9 of TETs-22 should be the first priority. The main issues that arose in developing this project—the customer’s requirements and the request for the reconstruction, the view on certain problems of Ural Turbine Works (UTZ) as the manufacturer of the main power unit equipment, and the opinions of other project parties—are examined. The decisions were made with account taken of the experience in operation of all Series T-250 turbines and the results of long-term discussions of pressing problems at scientific and technical councils, meetings, and negotiations. For the new power unit, the following parameters have been set: a live steam pressure of 23.5 MPa and live steam/reheat temperature of 565/565°C. Considering that the boiler equipment will be upgraded, the live steam flow is increased up to 1030 t/h. The reconstruction activities involving the replacement of the existing turbine with a new one will yield a service life of 250000 hours for turbine parts exposed to a temperature of 450°C or higher and 200000 hours for pipeline components. Hence, the decision has been made to reuse the arrangement of the existing turbine: a four-cylinder turbine unit comprising a high-pressure cylinder (HPC), two intermediate pressure cylinders (IPC-1 & 2), and a low-pressure cylinder (LPC). The flow path in the new turbine will have active blading in LPC and IPC-1. The information is also presented on the use of the existing foundations, the fact that the overall dimensions of the turbine unit compartment are not changed, the selection of the new turbine type, and the solutions adopted on the basis of this information as to LPC blading, steam admission type, issues associated with thermal displacements, etc.

The Cogeneration Turbine Т-295/335-23,5 Designed for the Reconstruction of Power-Generating Units Equipped with T-250/300-240 Turbines

A description of the cogeneration turbine Т -295/335-23,5 developed to replace Т -250/300-240 turbines with exhausted stock life has been given. The turbines Т -250 are installed in such big cities as Moscow, St. Petersburg, Kiev, Kharkov, and Minsk to meet the needs for centralized heat and electric power production. The prerequisites and options that are examined during the reconstruction of power units equipped with Т -250 turbines have been given. The structure of new Т -295 turbine has been described, some circuitry and layout solutions have been defined and the main obtained techno economic characteristics are shown taking into account the simultaneous reconstruction of boiler equipment to increase the steam output and live steam temperature and the reheat. Taking into account the need for the life maintenance of the units of turbine proper operating at a temperature higher than 450 ° С for about 250000 hours the materials selected to meet the above requirement were designated.

Integrated Mathematical Model of the Processes in the Turbine with Adjustable Steam Extraction

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Thermodynamic evaluation of the possibility to increase cogeneration turbine efficiency by using a heat pump operating with steam

Cogeneration turbines operate in different operation modes that considerably differ as to the working process conditions. In summer time, when heat demand is minimal, almost all steam flow passes through all turbine stages and enters into the condenser (condensing mode of operation). When heat supply is needed, the steam bleed-offs are used. The several last stages of the turbine (low-pressure part—LPP) have a control diaphragm at the inlet. When the heat supply is large, the diaphragm is maximally closed, and the entire steam flow, with an exception for a minimal ventilation flow is delivered to the steam bleed-offs (cogeneration mode). LPP flow path is designed for the optimal operation in the condensing mode. While running in cogeneration mode, the LPP operating conditions are far from optimal. Depending on the ventilation steam flow rate and outlet pressure, the LPP power can drop to zero or even become negative (ventilation mode). It is proposed to control an outlet steam pressure by using the heat pump that operates with steam. The heat pump energy consumption can be compensated and even exceeded by optimizing the steam expansion process in LPP. In this respect, operating conditions of cogeneration turbine LPPs during the cold season are analyzed. A brief description of a heat pump operating with steam is made. The possibility of increasing cogeneration turbine efficiency by using a steam heat pump is shown.

Modernization of exhaust hood of low-pressure cylinder of a cogeneration turbine T-250/300-23.5

An option of modernization of an exhaust hood for a low-pressure cylinder of a T-250/300-23.5 series turbine is presented in order to increase its effectiveness in a wide regimes range. An influence of a number of design decisions on gas-dynamic and energy characteristics of an exhaust compartment is considered. The investigation is carried out by the numerical simulation of a viscous wet steam flow through the exhaust compartment consisting of a last stage and an exhaust hood. A comparison of the calculated and experimental data is presented.

Results of Mathematical Modeling to Study the Influence of Accounting the Process Moisture on Energy Indicators of Cogeneration Steam Turbines

The article proposes and being tested a methodology that allows using the mathematical model developed to clarify the possible impact of a precise process moisture measurement on the performance of energy efficiency of the cogeneration turbines.

Influence of the Real Operation Modes of the Cogeneration Turbine T-100/120-130 on the Heat and Electric Energy Supply

Influence of the Real Operation Modes of the Cogeneration Turbine T-100/120-130 on the Heat and Electric Energy Supply

The T-125/150-12.8 cogeneration steam turbine

The article presents the design, the economic indicators, and the main solutions on the thermal process circuit and layout of the T-125/150-12.8 turbine, a new design version of the T-100-12.8 turbine, which is one of the best known, unique and widely used cogeneration turbines in Russia and abroad. The project of the new turbine is supposed to be used both for renovating and upgrading already installed turbines of the T-100 family and for supplying it as a full set for replacing obsolete equipment or constructing new one.

Prospects for constructing cogeneration stations equipped with back-pressure steam turbines

The possibilities of using back-pressure cogeneration turbines developed on the basis of serially produced ones are considered together with the thermal process circuits in which such turbines are applied. Design versions and advantages of cogeneration stations in which the proposed process circuits are implemented are described.

A numerical analysis of the serial design of the T-250/300-23.5 cogeneration turbine low-pressure cylinder’s exhaust hood

A mathematical model of the low-pressure cylinder’s exhaust compartment used in the serial design version of the T-250/300-23.5 turbine is constructed. The exhaust compartment consists of the turbine flow path last stage, a moisture removal chamber, and an exhaust hood (the EH stage). The effect of individual elements of the low-pressure cylinder exhaust compartment’s flow path on its gas dynamic characteristics in condensing modes of operation is numerically modeled for a wide range of steam flow rates. For the compartment with the exhaust hood completely filled with its inner elements, the flow patterns are calculated in partial modes of operation with presenting data on losses and flow-averaged integral characteristics at the diffuser inlet. The calculation results have been verified against the data of full-scale and model tests.

Improving the efficiency of steam-turbine plants of different capacities

Important scientific and technical problem of increasing operational efficiency of steam-turbine plants by developing new technologies for solving problems of efficient distribution of thermal and electrical loads between turbines and network heaters of cogeneration turbines during the heating period is solved in the paper. The scientific principles and methods for solving problems of both the analysis of power plant states, and their synthesis (optimization), taking into account a large number of factors, affecting the indicators of thermal circuit elements in their interaction, thus providing modeling of energy systems of different configurations with the ability to include new elements are developed. Additional modules of mathematical model and software-computer complex for calculating thermal circuits to implement energy-saving measures are developed and introduced. Formulation and solution of the problem of determining rational operation modes of thermal circuits of low-capacity steam-turbine plants (confirmed by implementation acts) is first performed. For power units of industrial enterprises, expediency of building steam-turbine plants up the power steam boilers (confirmed by implementation acts) is shown. The optimum modes of heat output from cogeneration turbines T-100/120-130 and T-250/300-240 (confirmed by implementation acts) are determined. The obtained results have shown the feasibility of solving the energy-saving optimization problems through generating additional electric power from CHP turbine plants. To solve this problem, new methods, which allow to propose measures on saving fuel and energy resources without additional capital investment, are used.