Improved steam turbine system

Abstract

A system comprising a steam turbine for power generation is disclosed. The steam turbine includes at least two expansion sections, each expansion section comprising at least one drum. The steam turbine also includes a shaft for connecting to at least one gearbox, a compressor, and a generator, with the drums arranged on the shaft. The steam turbine further includes a thrust bearing for absorbing axial forces during operation of the steam turbine and a compensating piston for compensating axial forces, the compensating piston being arranged on the shaft. The compensating piston has a first pressure side, a second pressure side, and at least one sealing surface. The first pressure side is connected via a first connection to a first pressure chamber of the expansion sections.The second pressure side is connected to a second pressure chamber of the expansion areas via a first valve and a second connection, and to a third pressure chamber of the expansion areas via a second valve and a third connection. The second and third connections are located downstream of the first pressure side. A method for operating the system is also disclosed, comprising the following steps: opening the first valve to provide a steam flow from the second pressure side of the compensating piston, via the first valve, into the second pressure chamber connected by the second connection at a first time, and opening the second valve to provide a steam flow from the second pressure side of the compensating piston, via the second valve, into the third pressure chamber connected by the third connection at a second time.

Description

Technical field

[0001] The invention relates to a steam turbine. In particular, the invention relates to a steam turbine for power generation with additional steam extraction and / or additional steam supply. Technical background

[0002] Steam turbines are used to convert heat into mechanical energy, particularly for electricity generation. In this process, steam is typically expanded through a single turbine stage or multiple turbine stages, usually arranged in drums.

[0003] In axial turbines, the steam flows axially along a shaft of the steam turbine or steam turbine system. The flow imparts a torque to the shaft, causing the turbine to rotate. Simultaneously, due to the conservation of momentum, the flow generates axial forces in the direction of the flow, which act on the turbine blades attached to the shaft. These axial forces are typically absorbed by an axial bearing.

[0004] To compensate for these axial forces, the prior art proposes compensating pistons. The compensating piston is mounted on the shaft. One side of the compensating piston is pressurized with steam at a higher pressure, while the other side is pressurized with steam at a lower pressure. The pressure difference also results in an axial force acting on the compensating piston. By arranging the axial piston and connecting its sides to two different pressure chambers or sections of pressure chambers within the turbine, an axial force is generated to compensate for the axial forces occurring during steam expansion.

[0005] To increase the efficiency of conventional power plants, it is also possible to extract steam from the steam turbine for other processes. This could include, for example, process steam at a medium pressure level or steam for heating purposes at a lower pressure level. Furthermore, heat or steam from other processes can be supplied, such as those with comparatively large amounts of waste heat, like metallurgical processes. This steam or heat can also be supplied at medium pressure levels relative to the boiler pressure of the power plant.

[0006] In such power plants, the steam mass flow rate can vary in different expansion ranges of the steam turbine due to steam supply and withdrawal. Consequently, the axial force acting on the shaft can be subject to comparatively large fluctuations. Description

[0007] One object of the invention is to provide a steam turbine system with improved efficiency and / or improved operational reliability.

[0008] In particular, it is an object of the invention to provide a steam turbine system with more efficient and / or safer axial force compensation in the event of additional steam extraction and / or steam supply.

[0009] A solution to this problem is provided in the independent claims. Further advantageous embodiments of the invention are described in the dependent claims, the following description, and the figures.

[0010] In a first aspect, a system is disclosed. The system comprises a steam turbine for power generation. The steam turbine includes at least two expansion sections, each expansion section comprising at least one drum. The steam turbine further comprises a shaft for connecting to at least one gearbox, compressor, and / or generator. The drums are arranged on the shaft. The steam turbine also includes a thrust bearing for absorbing axial forces during operation and a compensating piston for compensating axial forces. The compensating piston is arranged on the shaft.

[0011] The compensating piston has a first pressure side, a second pressure side, and at least one sealing surface. The first pressure side is connected via a first connection to a first pressure chamber of the expansion zones, for example, to a first pressure chamber within a first of the expansion zones.

[0012] The second pressure side of the axial piston is connected to a second pressure chamber of the expansion zones via a first valve and a second connection. Furthermore, the second pressure side is connected to a third pressure chamber of the expansion zones via a second valve and a third connection.

[0013] The second and third connections are located downstream of the first printing side.

[0014] The terms "upstream" and "downstream" refer to the direction of steam flow through the drums of the steam turbine during normal turbine operation. For example, a condenser is located downstream of a steam boiler.

[0015] The steam turbine can, in particular, be a stationary steam turbine of a power plant unit.

[0016] The term "expansion zone" refers to areas into or from which, during normal operation, essentially no steam is supplied or withdrawn, or from which, during normal operation, a quantity of steam is withdrawn that is essentially proportional to the steam mass flow rate. The withdrawn quantity of steam, essentially proportional to the steam flow rate, can, for example, include extraction mass flows used for feedwater preheating. However, leakage mass flows can be introduced into an expansion zone, for example, leakage mass flows across the sealing surface of the compensating piston. These are preferably small compared to the total mass flow rate through the respective expansion zone. An expansion zone comprises at least two pressure chambers.

[0017] Therefore, in an expansion region, if the turbine geometry, vapor density, and pressure ratio are known, a relationship between the total mass flow rate and the pressures in the expansion region can be approximated.

[0018] The pressure ratio can, for example, denote a ratio between inlet pressure and outlet pressure, especially according to Stodola's vapor cone law.

[0019] A drum comprises either a single turbine stage or multiple turbine stages. A drum therefore comprises at least one turbine rotor blade and at least one guide vane, and in particular multiple turbine rotor blades and multiple guide vanes. For example, the turbine blades of the drums can be arranged on the shaft, and associated guide vanes around the shaft in one or more guide vane carriers on a casing.

[0020] The axial bearing can be a bearing for absorbing forces in the axial direction of the shaft.

[0021] The compensating piston can be a compensating piston such as that known from EP 1035301 A1 or EP 2271827 B1.

[0022] The compensating piston can optionally be designed with steps.

[0023] The first and second pressure sides of the compensating piston can be essentially parallel. The normal vectors of the two pressure sides can be antiparallel. In other words, the first pressure side can have a first normal vector that is opposite to a second normal vector of the second pressure side.

[0024] The sealing surface of the axial piston can be a sealing surface of an essentially non-contact seal, for example a labyrinth seal or a brush seal. The system can also have a corresponding stationary sealing surface.

[0025] The first connection can connect the first printed page to a first printing space of an expansion area, in particular a first expansion area.

[0026] The first pressure chamber could, for example, be a pressure chamber in the expansion sections of the steam turbine, located upstream compared to the other expansion sections. In this example, the steam in the first pressure chamber could then be at a higher pressure compared to the other expansion sections.

[0027] The first connection can include at least one conductor and / or a direct connection, for example, within the housing. Preferably, the first connection includes the direct connection within the housing.

[0028] The second and third connections can each include at least one line and / or one direct connection. The second and third connections can also include at least one shared line segment.

[0029] The second connection can link the second printing page to a second printing chamber of the expansion areas. The third connection can link the second printing page to a third printing chamber of the expansion areas.

[0030] The second pressure chamber can be located upstream of the third pressure chamber. In particular, the second pressure chamber can be located at an expansion area upstream of an expansion area where the third pressure chamber is located.

[0031] The term "pressure chamber" refers to a space of the same pressure within the system. Adjacent pressure chambers can be separated from each other, for example, by valves, turbine stages, seals, steam inlets and / or steam outlets.

[0032] In particular, a pressure space can also denote a point or area of ​​an expansion space where a connection, for example the first connection, the second connection or the third connection, is attached.

[0033] The steam mass flow through the second connection can be controlled and / or regulated, for example, using the first valve. Similarly, the steam mass flow through the third connection can be controlled and / or regulated, for example, using the second valve.

[0034] Optionally, and advantageously, the second pressure side of the compensating piston can be connected to pressure chambers of different pressures. At least two of the first, second, and third pressure chambers can, for example, be located in different expansion zones.

[0035] Thus, it is optionally advantageous to set a lower pressure difference between the first and second pressure sides of the compensating piston via the first connection to the second pressure chamber than via the second connection to the third pressure chamber.

[0036] Thus, during operation, smaller leakage mass flows can optionally be advantageously achieved for adjusting the pressure on the second pressure side of the compensating piston, and / or overall leakage mass flows with a higher enthalpy level can be introduced into the expansion areas, thereby increasing the overall efficiency of the system.

[0037] Furthermore, the steam pressure on the second pressure side can optionally and advantageously be efficiently adjusted over a wider range, i.e., within a broader pressure interval. This allows a wider axial force band to be compensated for by the compensating piston, enabling safer and / or more efficient system operation.

[0038] The system may include a control device. The control device may be configured to determine an operating state of the steam turbine's expansion sections. In particular, the control device may be configured to determine a measure of the axial force. The control device may further be configured to control and / or regulate the first valve and the second valve depending on the operating state of the steam turbine's expansion sections, in particular depending on the measure of the axial force.

[0039] Thus, pressures on the second pressure side of the compensating piston can optionally be advantageously adapted to an axial force, and the load on the axial bearing can be kept within a permissible range.

[0040] In particular, the first and second valves can be designed as proportional valves. This allows, optionally and advantageously, a more reliable control and / or regulation of the steam flow via the second and / or third connection.

[0041] The measure of axial force can, in particular, be a measure of the axial force at the axial bearing. The measure of axial force can, for example, be calculated using linear regression based on known and / or simulated operating conditions.

[0042] The measure of the axial force can be determined from a weighted sum of measures for the operating conditions of the expansion ranges.

[0043] The dimensions for the operating conditions of the expansion ranges can include, for each expansion range, at least one of pressure, volume flow rate and mass flow rate at a point in the expansion range.

[0044] In particular, the measure of the axial force can be determined from a weighted sum of pressures at each point, especially at each measuring point, of each expansion area.

[0045] The system may include a first steam inlet to receive a live steam mass flow from a first steam generator. This could be, for example, a steam boiler. The first steam generator could, for example, be the system's main steam generator.

[0046] The system may include a first steam outlet to deliver an exhaust steam mass flow to a condenser.

[0047] The weights of the weighted sum of the measures for the operating states of the expansion ranges can at least approximate the influence of the operating states of the expansion ranges on the axial force.

[0048] The system may include a second steam outlet for extracting steam from the system, with the second steam outlet being located upstream of the first steam outlet.

[0049] In particular, the system for pressure-controlled withdrawal of process steam and / or steam for heating purposes can be set up at the second steam outlet.

[0050] The pressure of the steam at the second steam outlet can therefore be particularly higher than the pressure at the first steam outlet.

[0051] In particular, the system for intermittent process steam withdrawal can be configured at the second steam outlet. The withdrawal of process steam can therefore be interrupted and / or discontinuous. For example, the withdrawal of process steam can depend on the process for which the process steam is being drawn. Similarly, the withdrawal of steam for heating purposes can depend on a heating demand.

[0052] Thus, different axial forces can occur during operation with the same steam supply via the first steam inlet.

[0053] The control device can be configured to control and / or regulate the first and second valves in order to connect the second pressure side of the compensating piston to the second pressure chamber via the first valve and the second connection in a first interval of the axial force measurement, and to connect the second pressure side of the compensating piston to the third pressure chamber via the second valve and the third pressure side in a second interval of the axial force measurement.

[0054] This allows, optionally and advantageously, different pressure chambers and / or different expansion ranges to be connected to the second pressure side of the axial piston, depending on the operational axial force. This enables, optionally and advantageously, the setting of different pressures on the second pressure side with no or only limited throttling. As shown above, this can optionally and advantageously increase the efficiency of the system.

[0055] The first interval of the measure for the axial force can essentially correspond to axial forces that are larger in magnitude than the second interval of the measure for the axial force.

[0056] The intervals may have an overlapping range. The control device may be configured to introduce hysteresis between the closing and opening of the valves within the overlapping range during normal system operation.

[0057] This can optionally and advantageously prevent or reduce oscillations of the system.

[0058] The system may include a check valve designed to prevent steam flow between the pressure chambers via the second connection, the first valve, the second valve and the third connection.

[0059] This means that, optionally, efficiency losses due to steam mass flows outside the drums can be advantageously avoided or at least reduced when the first valve and the second valve are opened simultaneously.

[0060] In particular, the check valve can be positioned between the first valve and the second connection. This can optionally and advantageously allow the system to continue operating even if the first valve fails.

[0061] The non-return valve may have a closing aid, which may be designed in particular to ensure that the non-return valve is closed when the second valve is open.

[0062] This can optionally and advantageously further reduce the system's susceptibility to errors.

[0063] The first valve can be designed to close in case of a fault. This optionally allows for at least limited control and / or regulation of the system via the second valve.

[0064] The control device can be configured to connect the second pressure side of the compensating piston to the associated pressure chamber via the second valve and the third connection in the event of a fault of the first valve, both in the first interval of the axial force measurement and in the second interval of the axial force measurement.

[0065] This means that, optionally and advantageously, in the event of a fault, it may still be possible to control and / or regulate the pressure on the second pressure side of the axial piston.

[0066] The second valve can be designed to open in the event of a fault. The control device can be configured, in particular, to prevent the supply of process steam and / or steam for heating purposes in the event of a fault in the second valve. Thus, it is optionally advantageous to allow the steam turbine to continue operating for power generation without overloading the axial bearing, even in the event of a fault in the second valve.

[0067] The system can include a pressure measuring device for measuring pressure on the second pressure side of the compensating piston and a pressure measuring device for each of the expansion areas.

[0068] Thus, the measure of axial force can optionally and advantageously be determined. In particular, the measure of axial force can optionally and advantageously be determined very simply as a weighted sum of the measured pressures of the expansion zones.

[0069] The pressure measuring devices can each be designed redundantly.

[0070] In particular, each pressure measuring device can include at least three pressure sensors. This allows the pressure measuring device to optionally continue providing pressure data even if one pressure sensor fails.

[0071] The system may include a temperature measuring device for measuring the temperature of the axial bearing. In particular, the temperature measuring device may be redundant and comprise at least three temperature sensors.

[0072] This allows, optionally, the monitoring of an overload of the axial bearing and increases the operational reliability of the system.

[0073] The system may include a third steam outlet for extracting steam from the system. The third steam outlet may be located upstream of the first steam outlet.

[0074] In particular, the system for pressure-controlled steam extraction for heating purposes and / or as process steam can be configured at the third steam outlet. Specifically, the third steam outlet can be located downstream of the second steam outlet.

[0075] Thus, by using steam at lower pressure, the efficiency of an entire system can optionally be increased to a greater advantage.

[0076] The control device can be configured to also prevent steam extraction via the third steam outlet in the event of a fault in the second valve.

[0077] The system may include a second steam inlet for introducing steam into the system. This second steam inlet may be located downstream of the first expansion section of at least two expansion sections. The second steam inlet may, for example, be configured to introduce steam from another process, such as a heat exchanger in a metallurgical process.

[0078] In a second aspect, a method for operating a system with a steam turbine for power generation is disclosed. The system comprises the steam turbine. The steam turbine includes at least two expansion sections, each expansion section comprising at least one drum. The steam turbine further includes the shaft for connection to at least one gearbox, compressor, and / or generator. The drums are arranged on the shaft. The steam turbine further includes the axial bearing for absorbing the axial forces during operation of the steam turbine. The steam turbine further includes the compensating piston for compensating axial forces, the compensating piston being arranged on the shaft. The compensating piston has a first pressure side, a second pressure side, and at least one sealing surface.

[0079] The first printed page is connected to the first printing chamber via the first connection, for example to a first printing chamber within a first of the expansion areas.

[0080] The second pressure side is connected to the second pressure chamber of the expansion areas via the first valve and the second connection, and to the third pressure chamber of the expansion areas via the second valve and the third connection.

[0081] The second and third connections are located downstream of the first printing side.

[0082] The procedure involves opening the first valve to provide a steam flow from the second pressure side of the compensating piston via the first valve into the second pressure chamber at a first time point in time.

[0083] The procedure also includes opening the second valve to provide a steam flow from the second pressure side of the compensating piston via the second valve into the third pressure chamber at a second time.

[0084] Advantages, definitions and explanations regarding the system may also be applicable to the procedure.

[0085] The first time point can optionally be before or after the second time point.

[0086] The system used in the process may include the first steam inlet. The system used in the process may include the first steam outlet.

[0087] The system used in the process can include the second steam outlet, wherein the second steam outlet can be located upstream of the first steam outlet.

[0088] The system used in the procedure may include one or more features of the system of the first aspect.

[0089] The process can further include the intake of a fresh steam mass flow from a first steam generator via the first steam inlet.

[0090] The process may include supplying an exhaust steam mass flow to the condenser via the first steam outlet.

[0091] The method may include extracting steam from the system via the second steam outlet, in particular pressure-controlled extraction of process steam and / or steam for heating purposes via the second steam outlet.

[0092] This can optionally and advantageously increase the overall efficiency of the entire system.

[0093] The method may in particular further include at least temporary operation of the system at an operating point in which the pressure at the second pressure chamber is higher than the pressure at the third pressure chamber.

[0094] The method may further include the use of the control device. The method may also include determining the operating state of the steam turbine's expansion sections, in particular the axial force, using the control device. The method may also include controlling and / or regulating the first valve and the second valve depending on the operating state of the steam turbine's expansion sections, in particular the axial force.

[0095] The control device can control and / or regulate the first and second valves such that in the first interval of the axial force measurement the first valve is at least partially open and the second valve is closed, and in the second interval of the axial force measurement the second valve is at least partially open.

[0096] The system used in the process may include a check valve designed to prevent steam flow between the pressure chambers via the second connection, the first valve, the second valve, and the third connection. If the second valve is at least partially open, the first valve may remain open.

[0097] In this operating state, the check valve can optionally and advantageously be closed, so that the system can be operated independently of the first valve and the system's reliability can be increased.

[0098] The control unit may, in particular, include a computer-readable storage medium. The control unit may, for example, include a programmable logic controller (PLC). The control unit may include at least one processor and the computer-readable storage medium. The storage medium may contain instructions that lead to the operating behavior of the control unit as described above. The storage medium may also contain instructions that control the control unit according to the procedure.

[0099] The control unit can be configured to control and / or regulate the first valve and the second valve.

[0100] The control device can therefore, for example, comprise at least one microprocessor, one microcontroller, one FPGA (Field Programmable Gate Array), and / or one DSP (Digital Signal Processor). The control device can further comprise means for executing the disclosed method.

[0101] The control unit can also be configured to receive data for calculating the measure of axial force, such as pressure data, mass flow data and / or temperature data. Character description

[0102] The invention is further explained with reference to the accompanying illustrations. These illustrations show Figure 1 a first schematic diagram of a steam turbine; Figure 2 a second schematic diagram of the steam turbine; Figure 3 an enlarged section of the schematic diagram; Figure 4 a first diagram showing steam mass flow and turbine thrust for different operating points; Figure 5 a second diagram showing a measure of axial force and thrust of the turbine for different operating points; Figure 6 a third diagram showing valve control as a function of the measure of axial force and thrust of the turbine.

[0103] Figure 1 Figure 1 shows a preliminary schematic of a system comprising a steam turbine 10. In the example shown in the figures, steam can be extracted from the turbine for further processes and steam can be supplied from other processes.

[0104] The steam turbine 10 in Figure 1 It comprises three expansion areas: 12a, 12b, 12c.

[0105] Each expansion section 12a, 12b, 12c comprises at least one drum. Each drum comprises at least one guide wheel and one impeller, in particular a plurality of guide wheels and impellers. In other words, each drum comprises at least one stage, in particular a plurality of stages.

[0106] The expansion sections of turbine 12a, 12b, 12c can comprise several drums. During normal operation, essentially no steam is supplied to or withdrawn from the expansion sections 12a, 12b, 12c; rather, a quantity of steam is withdrawn that is essentially proportional to the steam mass flow rate.

[0107] Within the expansion ranges 12a, 12b, 12c, the relationship between mass flow and pressure profile in the expansion range is therefore essentially determined by the geometry of the drums, the vapor density, the pressure ratio and the connecting lines within the pressure range.

[0108] The pressure ratio can, for example, be a pressure ratio between the inlet and outlet of the expansion area, especially according to Stodola's vapor cone law.

[0109] At steam turbine 10 in Figure 1This is an axial turbine. Due to the conservation of momentum, axial forces occur during the operation of the steam turbine 10. These are absorbed by an axial bearing 14. To compensate for the axial forces, the steam turbine also includes a balancing piston 16. The balancing piston has a first pressure side 17 and a second pressure side 18. The balancing piston 16 is described with reference to Figure 3 further explained.

[0110] Furthermore, the system includes in Figure 1 a plurality of pressure measuring devices 40a, 40b, 40c, 40d. Each of the pressure measuring devices 40a, 40b, 40c is set up to measure a pressure in a pressure chamber of the expansion areas 12a, 12b, 12c.

[0111] Furthermore, sealing shells are schematically shown between the expansion zones 12a, 12b, and 12c. These seal the expansion zones from each other. The expansion zones are connected to each other by control elements (not shown).

[0112] Although in Figure 1 While a steam turbine 10 is schematically depicted for a steam mass flow in one direction (from left to right), the drums and / or expansion sections 12a, 12b, 12c can also be configured for a steam mass flow in different spatial directions, so that, for example, in Figure 1 In expansion area 12a, the flow passes through a first drum from left to right and a second drum from right to left. In this example, pressure area 12a encompasses... Figure 1 Then, corresponding connections between the two drums (not shown). These connections between the drums can, for example, be via the housing, especially an outer housing.

[0113] The system further comprises a first valve 30 and a second valve 32 as well as a check valve 54 between the first valve and an expansion area 12b of the steam turbine 10.

[0114] Figure 2 Figure 10 shows a further schematic diagram of the system and the steam turbine. For the sake of clarity, the representation of some components has been omitted. Figure 1 The static parts of the sealing shells, the valves 30 and the pressure measuring devices 40a, 40b, 40c, 40d have been omitted, e.g. the static parts of the sealing shells, the valves 30 and the pressure measuring devices 40a, 40b, 40c, 40d are not shown.

[0115] The steam turbine 10 in Figure 2 The system includes the compensating piston 16 and three expansion areas 12a, 12b, 12c. It also includes a first steam inlet 20 and a first steam outlet 24.

[0116] The first steam inlet 20 is configured for the inlet of boiler steam, i.e., live steam. The first steam outlet 24 is configured for the outlet of exhaust steam to a condenser (not shown). With this first steam inlet 20 and the first steam outlet 24, the steam turbine 10 can be operated according to common steam turbine processes, e.g., with or without reheating.

[0117] The steam turbine 10 in the example of Figure 2 is a double-extraction steam turbine. The system comprises in Figure 2 The system includes a second steam outlet 26 between a first expansion zone 12a and a second expansion zone 12b. Process steam, for example, can be drawn off from the second steam outlet 26 at controlled pressure. The system also includes a third steam outlet 28 between the second expansion zone 12b and a third expansion zone 12c. Steam, for example, for heating purposes, can be drawn off from the third steam outlet 28 at controlled pressure.

[0118] In the example of Figure 2 The system also features a second steam inlet 22 for the intake of steam. The steam at the second steam inlet 22 can, for example, be generated using waste heat from another process in a heat exchanger. This other process could be, for example, a welding process or a metallurgical process.

[0119] The withdrawal of steam via the second and third steam outlets 26, 28 may depend on a demand for process steam and / or steam for heating purposes. Likewise, the inlet of steam via the second steam inlet 22 may depend on the other process.

[0120] This means that the steam mass flow through the expansion zones 12a, 12b, 12c can differ. In particular, the steam mass flow through the individual expansion zones 12a, 12b, 12c can vary considerably. Consequently, the turbine thrust and the resulting axial force at the axial bearing 14 can vary significantly due to process-related factors.

[0121] Figure 3 This is an enlarged view of section A in Figure 1. Shown in Figure 3is part of the first expansion area 12a, the axial bearing 14, a section of the shaft 13 as well as a first pressure side 17 of the compensating piston, a second pressure side 18 of the compensating piston and a sealing surface 19 of the compensating piston.

[0122] The first pressure side 17 of the compensating piston has a first connection 34 with one of the expansion areas, in the example of the Figure 3 with the first expansion area 12a. In particular, the first connection can be a connection with a first pressure chamber of the expansion areas.

[0123] In particular, the first pressure side 17 of the compensating piston can be connected to a pressure chamber of the first expansion area 12a, which has a comparatively high pressure, e.g. a pressure on the order of the pressure at the first steam inlet 20 of the steam turbine 10.

[0124] The second pressure side 18 of the compensating piston is typically connected to another pressure chamber of the same or a different expansion area 12a, 12b, 12c. Different pressures on the first pressure side 17 of the compensating piston and on the second pressure side 18 of the compensating piston can generate an axial force that counteracts the axial force generated by the turbine thrust, thus reducing and / or compensating for the load on the axial bearing 14.

[0125] The compensating piston 16 typically includes a sealing surface 19 that separates the first pressure side 17 from the second pressure side 18. Leakage mass flows typically occur across the sealing surface 19.

[0126] Figure 4 shows a diagram that shows a thrust of the steam turbine 10 and a steam mass flow in a system that does not include either the second valve 32 or the third connection 38.

[0127] The axial bearing 14 is in the example of Figure 4 Designed to withstand shear forces from approximately -180 kN to approximately 180 kN. These limits are indicated by the corresponding horizontal lines. As can be seen, there are operating conditions in which higher shear forces occur.

[0128] In the example of Figure 4 The minimum thrust is not reached in some operating conditions during extraction operation, i.e., when steam is extracted through the second steam outlet 26 and / or through the third steam outlet 28.

[0129] At the same time, in the example of Figure 4 the maximum thrust was exceeded in some operating conditions during steam injection, i.e., when steam is supplied through the second steam inlet 22.

[0130] To compensate for these thrust forces, the second pressure side 18 of the compensating piston is connected via the first valve 30 and a second connection 36 to a pressure chamber of the expansion areas 12a, 12b, 12c and via the second valve 32 and a third connection 38 to one of the pressure areas.

[0131] In the example of Figure 1 The second pressure side 18 of the compensating piston is connected via the second connection 36 and the first valve 30 to a second pressure chamber, which is located in the second expansion area 12b, and via the third connection 38 and the second valve 32 to a third pressure chamber, which is located in the third pressure area 12c.

[0132] Valves 30 and 32 are controllable or adjustable, thus allowing a steam flow to be enabled via the second connection 36 and / or the third connection 38.

[0133] Preferably, the system is designed to allow a steam flow simultaneously only via the first and second connection 34, 36 or the first and third connection 34, 38.

[0134] In the example of Figure 1 The second connection 36 preferably connects the second pressure chamber of the expansion zones to the second pressure side 18 of the compensating piston, in which a higher pressure prevails at at least one operating point than in the third pressure chamber of the expansion zones, which the third connection 38 connects to the second pressure side 18 of the compensating piston. This relationship preferably applies essentially at all steady-state operating points during operation without steam withdrawal via the second or third steam outlet 26, 28 and without steam supply via the second steam inlet 22.

[0135] Thus, the second pressure side 18 of the compensating piston can be connected via the second connection 36 and the third connection 38 to different pressure chambers of the expansion areas 12a, 12b, 12c, so that, optionally, different pressure levels can be advantageously set on the second pressure side 18.

[0136] A smaller pressure difference between the pressure chamber of the expansion areas 12a, 12b, 12c connected to the second pressure side 18 and the second pressure side 18 can be achieved, for example, by partially opening the valve. However, this reduces the leakage mass flow, resulting in a loss of usable leakage mass flow.

[0137] Since the second pressure side 18 can be connected to different pressure spaces of the expansion areas 12a, 12b, 12c via the second connection 36 and the first valve 30 as well as the third connection 38 and the second valve 32, steam from the leakage mass flow can optionally be used advantageously at higher pressure levels of the turbine, and optionally also minimized at the same time.

[0138] This can optionally and advantageously increase the efficiency of the steam turbine 10. Furthermore, it can optionally and advantageously simplify the pressure adjustment on the second pressure side 18.

[0139] The check valve 54 between the first valve 30 and the second connection 36 prevents steam from flowing via the second connection 36 and the third connection 38 outside the turbine into a lower pressure area without performing work on a corresponding turbine section. The first valve 30 can thus, in the example of Figure 1 It must be executed in the event of an error.

[0140] This optionally increases the operational reliability of the steam turbine 10, since the second valve 32 can also be used to adjust the pressure on the second pressure side 18 of the balancing piston 16 in the event of a malfunction of the first valve 30. In this case, the check valve and the fault position of the first valve 30 ensure that the steam from the second pressure side 18 of the balancing piston flows via the second valve 32 and the third connection 38, but not via the first valve 30 into the second pressure chamber.

[0141] Furthermore, the second valve 32 is designed to open in the event of a fault. Optionally, this can also advantageously increase the reliability of the steam turbine 10, since in this fault condition a sufficiently low pressure is provided on the second pressure side 18 of the compensating piston to continue operating the steam turbine 10 for power generation.

[0142] Steam withdrawal via the second and third steam outlets 26, 28 and steam supply via the second steam inlet 22 can be prevented in the event of a malfunction of the second valve 32. This operating condition can also be referred to as full condensation mode.

[0143] Thus, in the event of a fault of the second valve 32, the thrust forces of the turbine can be kept within a defined range, so that, optionally, operation for power generation can be safely enabled despite a malfunction of the second valve 32.

[0144] The pressure measuring devices 40a, 40b, 40c, 40d are in the example of Figure 1 Redundantly designed with three pressure sensors. This ensures that even in the event of a single pressure sensor failure, a reliable pressure can still be determined, and the operational reliability of steam turbine 10 can optionally be further increased.

[0145] The system also includes a control unit (not shown). The control unit is configured to control and / or regulate valves 30 and 32. Furthermore, the control unit is configured to receive pressure data from pressure measuring devices 40a, 40b, 40c, and 40d.

[0146] As from Figure 4 As can be seen, the steam mass flow supplied via the first steam inlet 20 is not a suitable criterion alone for estimating the thrust or for controlling and / or regulating the first valve 30 and the second valve 32.

[0147] The pressure chambers of the expansion areas 12a, 12b, 12c can, for example, be ring sections of the expansion areas. However, the pressure chambers can also be, for example, areas within the expansion areas, such as in front of, between, or behind the drums of the expansion areas.

[0148] The first connection 34, the second connection 36 and the third connection 38 can each be provided directly or, for example, via connecting lines.

[0149] For example, the first connection 34 can be provided by arranging the first pressure side 17 of the compensating piston in a common pressure chamber with a drum of the turbine 10 and separating the second pressure side 18 from this pressure chamber by the sealing surface 19.

[0150] In this or another example, the second connection 36 and the third connection 38 can be designed as pipes.

[0151] Figure 5The diagram shows the thrust of steam turbine 10 as a function of a measure of axial force. The measure of axial force in this example is... Figure 5 a weighted sum of measures for operating states of the expansion ranges 12a, 12b, 12c. In the example of Figure 5 The dimensions for the operating states of the expansion zones 12a, 12b, 12c are pressures at a section of the pressure zones, e.g., at an inlet of each expansion zone 12a, 12b, 12c. However, other dimensions for the operating states are also conceivable, e.g., a mass flow rate through the respective pressure zone, from which the pressures at a pressure chamber of the expansion zones can be determined.

[0152] The measure for the axial force is, in the example of Figure 5This is a weighted sum of pressures at each pressure chamber of the expansion areas 12a, 12b, 12c. With reference to the pressures at the pressure measuring devices 40a, 40b, 40c, this sum can be formed in the example shown in the figures as follows: F ^ = a 1 p A 1 + a 2 p A 2 + a 3 p A 3

[0153] In Eq. 1 is F̂ the measure of axial force, a 1 until a 3 are constants, and p A 1 until p A 3 For each expansion area 12a, 12b, 12c, specify the pressure in a pressure chamber of the expansion area 12a, 12b, 12c.

[0154] More generally, the measure of axial force can be represented for any number of expansion ranges as F ^ = ∑ i p i a i where the variables are named analogously to Eq. 1.

[0155] The constants a 1 until oh They can be determined, for example, by linear regression from known and / or simulated load points.

[0156] Out of Figure 5The expert can deduce that the weighted sum of the measurements for the operating states of the expansion ranges 12a, 12b, 12c of the steam turbine 10 allows an estimate of the axial force.

[0157] Optionally, and advantageously, the weighted sum can be determined safely and / or reliably in a control device.

[0158] Figure 6 shows an exemplary strategy for controlling and / or regulating the first valve 30 and the second valve 32 based on the measure of the axial force.

[0159] Similarly to Figure 4 and Figure 5 The limits of the permissible shear forces for the axial bearing 14 are marked by horizontal lines.

[0160] In a first interval 50 of the axial force measurement, the first valve 30 is open, i.e., fully open or throttled. This allows a steam mass flow from the second pressure side 18 of the compensating piston via the second connection 36, and reduces the pressure on the second pressure side of the compensating piston 36 to at most the pressure in the second pressure chamber of the second expansion zone 12b in the example shown in the figures. Advantageously, any leakage mass flow via the sealing surface 19 of the compensating piston and the second pressure side 18 is then fed back to the corresponding expansion zone of the steam turbine 10 via the second connection 36 and further expanded in the turbine or extracted via the third steam outlet 28.

[0161] As can be seen, the first valve 30 continues to be throttled within a range of the first interval 50, so that the pressure on the second pressure side 18 is further increased. A setpoint for the pressure on the second pressure side 18 is shown on the left. Figure 6 Shown as an example.

[0162] If the measure of the axial force increases further into a second interval 52, the second valve 32 is opened, so that the pressure on the second pressure side 18 of the compensating piston decreases further or the leakage mass flow over the sealing surface 19 increases further.

[0163] Optionally, this can advantageously enable more efficient thrust compensation, since more steam from the leakage mass flow is introduced further upstream into turbine 10, i.e., into pressure chambers of higher pressure, across the different operating points than with other arrangements and / or strategies for valve control.

[0164] The quantitative data in Figure 4-6 The values ​​for axial bearing 14, thrust, mass flow, and axial force are purely exemplary. Different quantitative diagrams may result for other steam turbines, particularly for other systems with twin-extraction turbines. However, the qualitative relationships may be transferable. Reference symbol list

[0165] 10 Steam turbine 12a, 12b, 12c Expansion area 13 Shaft 14 Thrust bearing 16 Compensating piston 17 First pressure side 18 Second pressure side 19 Sealing surface 20 first steam inlet 22 second steam inlet 24 first steam outlet 26 second steam outlet 28 third steam outlet 30 first valve 32 second valve 34 first connection 36 second connection 38 third connection 40a, 40b, 40c, 40d Pressure measuring device 50 first interval 52 second interval 54 check valve

Claims

1. System comprising: - a steam turbine for power generation, comprising: ∘ at least two expansion sections, each expansion section comprising at least one drum, ∘ a shaft for connection to at least one gearbox, compressor, and generator, the drums being arranged on the shaft, ∘ a thrust bearing for absorbing axial forces during operation of the steam turbine, ∘ a compensating piston for compensating axial forces, the compensating piston being arranged on the shaft, the compensating piston having a first pressure side, a second pressure side, and at least one sealing surface, the first pressure side being connected via a first connection to a first pressure chamber of the expansion sections, the second pressure side being connected a) via a first valve and a second connection to a second pressure chamber of the expansion sections,and b) is connected via a second valve and a third connection to a third pressure chamber of the expansion areas, wherein the second connection and the third connection are arranged downstream of the first pressure side.

2. System according to the preceding claim, wherein the system comprises a control device, wherein the control device is configured to determine an operating state of the expansion ranges of the steam turbine, in particular to determine a measure of the axial force, and to control and / or regulate the first valve and the second valve depending on the operating state of the expansion ranges of the steam turbine, in particular depending on the measure of the axial force, in particular wherein the first valve and the second valve are designed as continuous valves.

3. System according to the preceding claim, wherein the measure for the axial force is determined from a weighted sum of measures for the operating states of the expansion ranges, wherein the measures for the operating states of the expansion ranges for each pressure range include at least one of pressure, volume flow rate and mass flow rate at a point of the expansion range.

4. System according to one of the preceding claims, further comprising a first steam outlet for delivering an exhaust steam mass flow to a condenser and a second steam outlet for extracting steam from the system, wherein the second steam outlet is arranged upstream of the first steam outlet, wherein the system is in particular configured for pressure-controlled extraction of process steam and / or steam for heating purposes at the second steam outlet.

5. System according to one of the preceding claims 2-4, wherein the control device is configured to control and / or regulate the first and second valves in order to connect the second pressure side of the compensating piston to the second pressure chamber via the first valve and the second connection in a first interval of the axial force measurement, and to connect the second pressure side of the compensating piston to the third pressure chamber via the second valve and the third connection in a second interval of the axial force measurement.

6. System according to one of the preceding claims, wherein the system has a check valve which is configured to prevent a steam flow between the pressure spaces via the second connection, the first valve, the second valve and the third connection, in particular wherein the check valve is arranged between the first valve and the second connection.

7. System according to the preceding claim, wherein the check valve has a closing aid, wherein the closing aid is in particular designed to ensure that the check valve is closed when the second valve is open.

8. System according to one of the preceding claims, wherein the first valve is designed to close in the event of a fault.

9. System according to one of the preceding claims with the features of claims 5 and 8, wherein the control device is configured to connect the second pressure side of the compensating piston to the third pressure chamber via the second valve and the third connection in the event of a fault of the first valve, both in the first interval of the measure for the axial force and in the second interval of the measure for the axial force.

10. System according to one of the preceding claims 2-9, wherein the second valve is designed to open in the event of a fault, wherein the control device is in particular configured to prevent the provision of process steam and / or steam for heating purposes in the event of a fault of the second valve.

11. System according to one of the preceding claims, wherein the system comprises a pressure measuring device for measuring a pressure on the second pressure side of the compensating piston and a pressure measuring device for each of the expansion areas.

12. System according to the preceding claim, wherein the pressure measuring devices are each redundant, in particular wherein each pressure measuring device comprises at least three pressure sensors.

13. System according to one of the preceding claims with the features of claim 4, wherein the system comprises a third steam outlet for extracting steam from the system, wherein the third steam outlet is arranged upstream of the first steam outlet, and wherein the system is in particular configured for pressure-controlled extraction of process steam and / or steam for heating purposes at the third steam outlet.

14. System according to one of the preceding claims, wherein the system comprises a first steam inlet for receiving a live steam mass flow from a first steam generator and a second steam inlet for introducing steam into the system, wherein the second steam inlet is arranged downstream of a first of the at least two expansion regions.

15. Method for operating a system with a steam turbine for power generation, wherein the system comprises: - a steam turbine comprising: ∘ at least two expansion sections, each expansion section comprising at least one drum, ∘ a shaft for connection to at least one gearbox, compressor, and generator, the drums being arranged on the shaft, ∘ a thrust bearing for absorbing axial forces during operation of the steam turbine, ∘ a compensating piston for compensating axial forces, the compensating piston being arranged on the shaft, the compensating piston having a first pressure side, a second pressure side, and at least one sealing surface, the first pressure side being connected via a first connection to a first pressure chamber of the expansion sections, the second pressure side being connected a) via a first valve and a second connection to a second pressure chamber of the expansion sections,and b) is connected via a second valve and a third connection to a third pressure chamber of the expansion areas, wherein the second connection and the third connection are arranged downstream of the first pressure side, the method comprising the following steps: - opening the first valve to provide a steam flow from the second pressure side of the compensating piston via the first valve into the second pressure chamber at a first time, and - opening the second valve to provide a steam flow from the second pressure side of the compensating piston via the second valve into the third pressure chamber at a second time.

16. Method according to the preceding claim, wherein the method further comprises: - using a control device, - determining an operating state of the expansion ranges of the steam turbine, in particular a measure of the axial force, by means of the control device, and - controlling and / or regulating the first valve and the second valve depending on the operating state of the expansion ranges of the steam turbine, in particular depending on the measure of the axial force.

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