RU173299U1 - Steam turbine - Google Patents

Abstract

The utility model relates to a power system and can be used in steam turbine plants of nuclear power plants (NPPs). EFFECT: increased efficiency and reliability of a steam turbine installation. The steam turbine installation comprises a turbine consisting of a combined cylinder having a high pressure part and a medium pressure part, a low pressure cylinder, a seal manifold and a deaerator. The deaerator communicates with a part of the high pressure and through a control valve with a seal manifold. The first steam exhaust chamber of the front end seal of the combined cylinder, designed to collect steam leaks from the high-pressure part, is in communication with the steam extraction pipe from the medium-pressure part. The second chamber for removing steam from the front end seal of the combined cylinder, located behind the first chamber for steam removal, and the chamber for removing steam from the rear end seal of the combined cylinder are in communication with the seal manifold. The seal manifold communicates with the steam supply chambers of the front and rear end seals of the low pressure cylinder. 1 ill.

Description

The utility model relates to a power system and can be used in steam turbine plants of nuclear power plants (NPPs).

The source of steam for the steam turbine plant of a nuclear power plant is a nuclear steam production plant (steam generator). Modern turbines typically consist of several cylinders, including a high pressure cylinder, a medium pressure cylinder, and one or more low pressure cylinders. Each cylinder can be single-threaded or two-threaded. The turbine, which is part of the steam turbine installation, drives a turbogenerator, which is designed to generate alternating current.

When designing a steam turbine installation, much attention is paid to increasing the efficiency of the installation. End seals provide operational reliability of the turbine and affect its efficiency. The turbine end seals are designed to prevent steam leaks into the engine room from the turbine cylinders above atmospheric pressure, as well as to prevent air suction into the turbine cylinders in the presence of vacuum.

The invention is known as "Steam-powered installation" (USSR author's certificate No. 1101566, F01K 13/02, publ. 07/07/1984), which contains cylinders of high, medium and low pressure with steam supply chambers to the front and rear end seals connected to the manifold supply (seal manifold), having at least two sections separated by a valve, and vacuum chambers equipped with lines (pipelines) for the removal of steam and vapor-air mixture. The installation is equipped with at least three additional pipelines with shut-off and control valves placed on them, two of which communicate the first section of the collector with the steam exhaust lines from the vacuum chambers of the high-pressure cylinder and the chamber of the front end seal of the medium-pressure cylinder, respectively, and the third pipeline communicated with the second section of the collector and the vacuum chambers of the rear end seal. The indicated technical solution is not rational to use for turbine plants of nuclear power plants in connection with a large number of chambers for supplying sealing steam for end seals of high pressure cylinders and medium pressure cylinders and, accordingly, pipelines and shut-off and control valves. Also, the collector device is characterized by the presence of sections with different pressures, which requires additional control valves. The pressure in the cylinders of the steam turbine units of thermal power plants (TPPs) significantly exceeds the pressure in the cylinders of the steam turbine units of nuclear power plants, and the more rational use of high-potential steam in the end seal chambers of the TPP turbines requires the organization of additional seal chambers, which is not advisable for the end seals of the NPP turbines.

Known technical solution "Installation with steam turbine modules of optimized efficiency" (RF application No. 2012141598, IPC F02C 6/00, publication date 04/27/2014). The installation includes a high pressure steam turbine module (high pressure cylinder), a medium pressure steam turbine module (medium pressure cylinder) and at least one low pressure steam turbine module (low pressure cylinder), sealing devices (end seals) located between the rotating shaft of the turbine (turbine rotor) and the corresponding casings of the turbine modules of high, medium and low pressure. In the casing of the high-pressure turbine module, there is a first collection chamber for collecting steam leaks leaving the specified module through its sealing devices at pressures above atmospheric. In the housing of the low-pressure turbine module, injection chambers (supply chambers) are placed, connected by the first circuit (seal manifold) to the first collection chamber so that the steam is transferred from the first collection chamber towards the injection chambers and then to the low-pressure turbine module through leaks through it sealing devices. The second collection chamber is located in the housing of the medium-pressure turbine module in order to collect steam leaks leaving the specified module through its sealing devices at a pressure above atmospheric pressure and to transfer the indicated leaks along the primary circuit (seal manifold) in the direction of the above injection chambers. The first circuit (seal manifold) includes a pressure control device (pressure reducer) that maintains the pressure in this circuit at a level above atmospheric.

The disadvantage of this solution is the transfer of steam leakage from the first collection chamber to the first circuit (seal manifold), thus, this leak does not participate in the steam cycle. In addition, the total steam flow directed to the primary circuit from the pre-assembled chambers of the high-pressure turbine module and the medium-pressure turbine module is not sufficient to maintain pressure in the primary circuit and, accordingly, to ensure constant steam supply to the injection chambers of the low-pressure turbine module, i.e. it does not prevent air from entering the low pressure turbine module. Therefore, to provide pressure in the primary circuit (seal manifold) at all turbine operating modes, an additional supply of fresh (high-potential) steam from the steam generator through a pressure reducer is required, which is not thermodynamically justified, since the utilization of high-potential steam leads to a decrease in the cost-effectiveness of the installation.

The closest technical solution to the proposed technical solution for the combination of essential features and selected as a prototype is the invention "Steam turbine installation, turbine installation and method of operation of the turbine" (US patent 8650878; IPC F01D 11/06; publication date 02/18/2014). According to the invention, the turbine installation comprises a high pressure cylinder connected to a medium pressure cylinder and a low pressure cylinder; a seal manifold for supplying constant pressure sealing steam through pipelines to the steam supply chambers of the front and rear end seals of the low pressure cylinder and in communication with the condenser to discharge the first steam flow rate; the first steam exhaust chamber of the front end seal of the high-pressure cylinder, designed to collect steam leaks from the high-pressure cylinder, is in communication with the medium-pressure cylinder; a second steam exhaust chamber located behind the first steam exhaust chamber of the front end seal of the high pressure cylinder is connected by a pipeline to the seal manifold; the steam exhaust chamber of the rear end seal of the medium pressure cylinder is connected by a pipeline to the seal manifold; a valve located on the leakage pipe from the first chamber of the front end seal of the high pressure cylinder and designed to control the flow rate of steam leakage into the seal manifold from the second chamber of the front end seal; regulator to control valve operation.

The main power source for the seal manifold is leakage from the front end seal of the high pressure cylinder. When the turbine self-sealing mode is reached (turbine unit operation mode is 90%), the control valve on the leakage pipeline from the first seal chamber of the high-pressure cylinder is fully open. In these modes, 90% of the steam flow rate is used to power the seal manifold, the remaining 10% of the leakage is discharged into the condenser and does not participate in the generation of electricity in the turbine. In partial operation modes of the turbine unit (less than 90%), by means of the valve indicated above, by means of its cover, the flow rate of steam leakage directed to the seal manifold from the second chamber of the front seal of the high pressure cylinder is increased.

The disadvantages of this solution are:

in the technical solution there is no third-party source of steam for the seal manifold, and therefore, to achieve the self-sealing mode, it is necessary to organize a relatively large amount of steam leakage through the front end seal of the high pressure cylinder. The specified steam leakage is directed to the seal collector and then does not participate in the generation of electricity;

if this technical solution is used for steam turbine plants of nuclear power plants, the steam humidity behind the high pressure cylinder will be more than 10%, and taking into account throttling in the front end seal, the steam temperature will drop to 100 ° C, which is not satisfactory for using it as a sealing pair of a low cylinder pressure. The moisture contained in the steam causes significant erosive wear of the control and shutoff valves and parts of the turbine seals, causes water hammer in the seal pipelines, so low steam temperature reduces the reliability of the end seals of the low pressure cylinder;

in the nominal operating mode of the steam turbine unit, a part of the leak is not used as sealing steam for the end seals of the low pressure cylinder, but is discharged from the seal manifold into the condenser (10%) and is not involved in the generation of electricity, which leads to a loss of efficiency;

the positive effect of the known invention is determined in comparison with leakage schemes in which 70% of the steam flow supplied to the seal manifold is discharged to the condenser. This comparison is not correct, since in the implemented schemes of operation of seals, pairs of leaks are sent to regenerative heaters. Thus, the claimed economic effect of the known invention is not confirmed by the applicable schemes.

The technical result, the claimed utility model is aimed at, is to increase the efficiency and reliability of the steam turbine installation.

The specified technical result is achieved in that the steam turbine installation comprises a turbine consisting of a combined cylinder having a high pressure part and a medium pressure part, with steam chambers for front and rear end seals connected to at least one low pressure cylinder with supply chambers a pair of front and rear end seals, a manifold of seals and a deaerator. The deaerator communicates with a part of the high pressure and through the control valve with the seal manifold. The first steam exhaust chamber of the front end seal of the combined cylinder, designed to collect steam leaks from the high-pressure part, is in communication with the steam extraction pipe from the medium-pressure part. The second steam exhaust chamber of the front end seal of the combined cylinder, located behind the first steam chamber, and the steam chamber of the rear end seal of the combined cylinder are in communication with the seal manifold. The seal manifold communicates with the steam supply chambers of the front and rear end seals of the low pressure cylinder.

In the proposed technical solution, the high and medium pressure parts of the turbine are combined in one cylinder (housing). This solution differs from the traditional design of high-power steam turbines with saturated steam, in which the high and low pressure cylinders are made in separate two-line designs, and do not require a separate part or medium-pressure cylinder. In the proposed turbine, the combined cylinder includes a high-pressure part of a single-threaded structure located in the left stream, and a medium-pressure part of a single-threaded structure also located in the right-hand stream of the cylinder. The transition to a single-threaded design of the cylinder allows you to place in one cylinder the flow part of the high pressure and flow part of the medium pressure and increase the efficiency of the turbine as a whole, reduce the dimensions of the turbine and the metal consumption of the turbine.

The proposed technical solution allows you to save part of the steam leakage from the high-pressure part of the combined cylinder, which is guided from the first steam exhaust chamber of the front end seal of the combined cylinder to the steam extraction pipe from the medium pressure part of the combined cylinder. This leakage allows you to save part of the selected steam sent from part of the medium pressure to the regeneration system to generate electricity in the low pressure cylinder.

With regard to steam turbine units of saturated steam NPPs, the use of the end seal of a high pressure cylinder as a source of steam seal seals is not satisfactory due to the high humidity and low temperature of the steam. In this connection, traditionally in turbine units of nuclear power plants, the seal collector is supplied with throttled fresh steam from a steam generator. In the proposed technical solution, a deaerator is used as a source of steam in the nominal mode for the seal manifold. This solution allows you to save high-potential steam sent to the turbine to generate electricity, which increases the efficiency (efficiency) of the turbine.

A control valve is installed on the steam supply pipe to the seal manifold from the deaerator to maintain a constant pressure in the seal manifold just above atmospheric pressure. This valve eliminates the need for many separate pressure regulators on the steam supply pipelines to the chambers of the front and rear end seals of the low pressure cylinder, which simplifies the circuit and increases its reliability.

The drawing shows a schematic diagram of a steam turbine installation.

The source of steam for the steam turbine installation is steam generator 1. The steam turbine installation contains a turbine comprising a combined cylinder consisting of a single-threaded high-pressure part (CVP) 2 and a single-threaded medium-pressure part (ChSD) 3, as well as a two-flow low-pressure cylinder (LPC) 4. Steam generator 1 is communicated by pipeline 5 with CVP 2, CVP 2 is connected by pipeline 6 with CSR 3 through a steam superheater 7. Separator-steam superheater 7 is traditionally used for steam turbine plants of nuclear power plants to remove moisture from steam and superheated steam. CHS 3 pipeline 8 communicates with the low-pressure cylinder 4. The turbine is connected to a turbogenerator 9.

Cylinders have front and rear end seals. The end seal of the cylinder located on the side of the turbogenerator (in the considered example of the turbogenerator 9) is considered to be the rear seal, and the front seal on the opposite side of the cylinder.

Traditionally, the end seal of any cylinder consists of several labyrinth compartments separated by chambers through which the sealing vapor is supplied or the sealing medium is withdrawn. The scheme of end seals is designed in accordance with the basic design principles and reliability requirements (see, for example, “Labyrinth seals for stationary steam and gas turbines and compressors”, Design and calculation. RTM 108.020.33-86. Signed for print on 09/21/1988; Zhiritsky G.S. Design and Strength Analysis of Steam Turbine Parts, Goenergoizdat, 1955, pp. 219-222; Trukhniy A.D., Losev S.M. Stationary Steam Turbines. M: Energoizdat, 1981, pp. 104-106 )

The steam exhaust chambers of the front end seal of the combined cylinder are divided into a first steam exhaust chamber 10 for collecting steam leaks from the CVP 2, and a second steam exhaust chamber 11, located behind the first steam exhaust chamber 10, for collecting steam leaks from the first chamber 10. The first chamber 10 of the steam outlet is connected by a pipe 12 with a pipe 13 for the selection of steam from CHSD 3, sent from the medium pressure part to the regeneration system.

The chamber 14 for the removal of steam from the rear end seal of the combined cylinder is designed to collect steam leaks from the CSD 3. The chamber 11 for the extraction of steam of the front end seal of the combined cylinder and the chamber 14 for the removal of steam from the rear end seal of the combined cylinder are in communication with the seal manifold 15 by pipelines 16 and 17, respectively.

Chambers 18 for supplying steam of the front and rear end seals of the low pressure cylinder 4 are connected to the seal manifold 15 by pipelines 19 in order to prevent air from entering the atmosphere of the machine room into the low pressure cylinder 4.

The deaerator 20 communicates with the manifold 15 by a pipe 21 on which the control valve 22 is installed. The control valve 22 is designed to throttle the steam and maintain a constant pressure slightly above atmospheric in the seal manifold 15. The deaerator 20 communicates with the CVP 2 by the pipe 23.

Vacuum chambers 24, which are the last along the steam leaks of the chambers of the front and rear end seals of the combined cylinder and low pressure cylinder, are connected by pipelines 25 to the condenser pair of seals 26. The condenser pair of seals 26 is designed to receive the vapor-air mixture from the vacuum chambers 24 due to the created in it rarefaction.

In steam turbine plants of nuclear power plants, the vacuum chambers of the end seals of the cylinders are traditionally located last and are designed to prevent air from entering the turbine cylinders, as well as to remove the vapor-air mixture formed by mixing steam leaks from seals and air leaks from the atmosphere of the turbine room.

When the steam turbine unit is operating in the nominal mode, fresh steam with a pressure of, for example, about 6.8 MPa, and a temperature of about 284 ° C, is sent from the steam generator 1 through pipeline 5 to the combined cylinder cylinder 2. Then, the steam leaving the HPP 2 with a humidity of at least 10% is sent through line 6 to the PSA 3 through a steam superheater 7, which separates moisture from the steam and heats the steam to a temperature of at least 270 ° C. Next, the steam leaving CHS 3 through the pipe 8, enters the low pressure cylinder 4. The steam drives the turbine shaft, which transmits the rotation to the shaft of the turbogenerator 9 in order to generate electricity.

To prevent air from entering the atmosphere of the engine room in the low pressure cylinder 4 into the chambers for supplying 18 front and rear end seals of the low pressure cylinder 4 through the piping 19 from the seal manifold 15, sealing vapor is supplied. The direction of movement of the steam and air leaks into the seal chambers is indicated by arrows in FIG. 15 pairs are supplied to the seal manifold from the steam extraction chambers 11 and 14 of the front and rear end seals of the combined cylinder, respectively, and the control valve 22 maintains a constant pressure of about 0.12 MPa in the seal manifold 15, into which steam from the deaerator 20 flows through line 21. In the deaerator 20 pairs comes from CVP 2 through the pipe 23.

The vapor-air mixture from the vacuum chambers 24 is discharged through pipelines 25 to a steam condenser of seals 26, in which the pressure is maintained below atmospheric (about 0.095 MPa).

Thus, the total steam flow rate supplied to the seal manifold 15 will be sufficient to supply steam to the steam supply chambers 18 of the low-pressure cylinder end seals 4 to prevent air from entering, and the temperature of the sealing steam in the steam supply chambers 18 will be at least 120 ° C, which ensures the absence of moisture in the pair and, as a result, the reliable operation of the seals. Thus, the direction of the portion of the steam leakage from the first chamber 10 into the steam withdrawal pipe 13 from the PSR 3 allows you to save part of the selected steam sent from the PSR 3 to the regeneration system to generate electricity in the low-pressure cylinder 4.

In the proposed technical solution, a deaerator is used as a source of steam in the nominal mode for the seal manifold. This solution allows you to save high-potential steam sent to the turbine to generate electricity, which increases the estimated value of the efficiency of the steam turbine plant by more than 0.1%.

Claims (1)

A steam turbine installation, characterized in that it comprises a turbine consisting of a combined cylinder having a high pressure part and a medium pressure part, with steam chambers for front and rear end seals connected to at least one low pressure cylinder with front steam chambers and rear end seals, a manifold of seals and a deaerator in communication with a part of the high pressure and through a control valve to a manifold of seals, while the first chamber for removing steam is at the front end a combined cylinder seal designed to collect steam leaks from the high pressure part is in communication with a steam extraction pipe from the medium pressure part, and a second steam exhaust chamber of the front end seal of the combined cylinder located behind the first steam exhaust chamber and a steam exhaust chamber of the rear end seal the combined cylinder communicates with the seal manifold, and the seal manifold communicates with the steam supply chambers of the front and rear end seals of the low pressure cylinder.

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