Turbo-alternator group and power plant provided with such a turbo-alternator group

Abstract

The invention relates to a turbo-alternator group (3) comprising: - an alternator (5) comprising a driven shaft (16); - at least one drive stage (E1) comprising a plurality of turbines (7), each turbine (7) comprising a rotor (13) driving a drive shaft (15), the drive shaft (15) carrying a primary gear (17); and - a transmission reduction system (19) mechanically connecting each primary gear (17) to the driven shaft (16) with a reduction ratio strictly greater than 1, the transmission reduction system (19) comprising an intermediate shaft (21) carrying one secondary gear (23) per drive stage (E1), such that, in each drive stage (E1), each primary gear (17) meshes with the secondary gear (23) of the drive stage (E1). The invention also relates to a power plant (1) comprising such a turbo-alternator group (3).

Description

[0001] DESCRIPTION

[0002] TITLE: Turbo-alternator unit and power plant equipped with such a turbo-alternator unit

[0003] TECHNICAL FIELD

[0004] The invention applies to a turbo-alternator unit, as well as to a power plant comprising such a turbo-alternator unit.

[0005] STATE OF THE ART

[0006] Typically, power plants, particularly nuclear and thermal power plants, include a turbine-generator unit, which is a rotating machine that generates electricity from pressurized steam. Such a turbine-generator unit consists of at least one turbine and one generator. For example, a typical power plant, especially a nuclear one, includes a turbine-generator unit made up of a high-pressure turbine, one or more low-pressure turbines (for example, three low-pressure turbines), and one generator.

[0007] For example, document EP 2 434 103 A1 describes in particular a turbine system, document US 2009 / 0297337 A1 describes in particular a set of turbines associated with a gear train, and document DE 10 2012 000044 U1 describes in particular an electricity production device.

[0008] Electricity generation using turbines often follows the Rankine cycle. In its simplest form, the Rankine cycle involves steaming water in a boiler, also called a steam generator, using heat from a heat source. This heat source can come from the combustion of a gas (such as natural gas or hydrogen), the combustion of coal, or any other energy-releasing material (such as fuel oil or waste). Alternatively, the heat source can come from the fission of atoms in a nuclear reactor. The hot, high-pressure steam passes through a turbine, which mechanically drives a generator. This generator produces electricity, which is then used on-site or fed into the electrical grid.The work produced by the turbine is achieved by expanding the steam, which cools as it passes through the turbine. The steam exiting the turbine can be either dry or wet (containing water droplets). This steam is then condensed in a condenser to become water again. Condensation is achieved by cooling the steam exiting the turbine with a cold source. This cold source is often seawater or river water. The condensed water is returned to the boiler by a pumping unit. To improve the thermodynamic efficiency of the simple Rankine cycle, an enhanced version of this cycle is often used. In this case, a steam generator using a heat source, such as a primary fluid heated by the fission reaction in a nuclear reactor, produces steam at high pressure and high temperature.This steam is injected into the first stage of the high-pressure (HP) turbine drive. A small portion of the steam produced by the steam generator is sent to a heat exchanger, which preheats the steam exiting the HP turbine. Once preheated, this steam is injected into a low-pressure (LP) turbine. The expansion of the steam in the HP and LP turbines produces mechanical work, which is transmitted by rotors to the alternator. The alternator then converts this mechanical work into electrical current.

[0009] Such a turbo-alternator group is classically linear, and consists of a line formed of one or more turbines and an alternator, which are connected together by rigid couplings to form a line of shafts.

[0010] This means that the turbine(s) and the generator must operate at the same rotational speed. The size of a turbo-generator unit is often very large, with linear lengths reaching several tens of meters and a mass on the order of several hundred tons. These significant dimensions mean that each turbo-generator unit is a unique model, specific to the spatial configuration of the power plant site in which it is housed. Such a turbo-generator unit is also sensitive to its environment. For example, aligning a turbo-generator unit is an operation that requires taking into account the expansion of the mechanical components and the civil engineering structures that support it, and even that of the building housing the turbo-generator unit. Managing these factors requires considerable intervention time and heavy handling, which has a significant impact on the availability of the turbo-generator unit.Furthermore, the malfunction of a single component constituting the turbo-alternator group requires the cessation of electrical production and the in-situ repair of the defective component.

[0011] Currently, the architecture of turbo-alternator units designed for small power plants, particularly small modular reactor (SMR) nuclear power plants, is similar to that of large nuclear power plants: a linear assembly of turbines and an alternator. SMRs aim to provide a complementary solution to renewable energies and to replace coal-fired power plants, supply electricity to isolated communities and energy-intensive industrial sites, as well as grids with capacities too limited for large-scale power plants. Such SMRs are designed with a focus on standardization, modular construction, and simplicity for mass production in factories, with flexibility during construction and operation.

[0012] However, this conventional turbo-alternator unit architecture is not optimal for the objectives of SM R reactors. These reactors, smaller in size and with a lower electrical output (between 10 MWe and 300 MWe, for example, around 170 MWe to 180 MWe) than conventional reactors, are manufactured in a factory. They are then transported to the installation site to reduce on-site work and minimize manufacturing costs thanks to their standardized modular design. These SM R reactors can also be optimized for load following and adapted for non-power-generating applications such as heat generation or hydrogen production.

[0013] As an example, a power plant consists of two independent and similar 170 MWe SM R reactors. The reactor design is centered on standardization, modular construction, and simplicity for mass production in a factory, with flexibility during construction and operation.

[0014] To improve standardization, it is necessary to minimize site effects and manufacture as many components as possible in the factory, then transport them to the plant for installation. Maintenance operations must also be standardized by promoting the exchange of standard or modular parts to perform most maintenance in the factory.

[0015] There is therefore a need to propose a turbo-alternator group architecture that aims to get as close as possible to the modular design of the SM R, in order to take full advantage of the levers offered by modularity and series manufacturing in the factory.

[0016] DESCRIPTION OF THE INVENTION

[0017] The present invention aims in particular to remedy the aforementioned disadvantages, by proposing a turbo-alternator unit with higher modularity, thus making it possible to standardize its main components, while simplifying its manufacture and maintenance.

[0018] To this end, the invention proposes, according to a first aspect, a turbo-alternator unit, remarkable in that it comprises:

[0019] - an alternator comprising a driven shaft,

[0020] - at least one drive stage comprising several turbines, in which each turbine comprises a rotor driving a drive shaft, the drive shaft carrying a primary gear, and

[0021] - a transmission reduction system, which mechanically connects each primary gear to the driven shaft with a reduction ratio strictly greater than 1, such that each primary gear is capable of rotating at a rotational speed strictly greater than that of the driven shaft, the transmission reduction system comprising an intermediate shaft carrying a secondary gear per drive stage, such that in each drive stage, each primary gear is meshed with the secondary gear of the drive stage.

[0022] Thus, a turbo-alternator unit conforming to the proposed solution offers higher modularity, making it possible to standardize its main components, while simplifying its manufacture and maintenance.

[0023] Indeed, the rotational speed of the turbines is greater than that of the generator, which allows for a significant reduction in turbine size and mass, and improves their thermodynamic efficiency. This size reduction has important advantages, particularly in the context of small modular reactors (SMRs). By reducing the size of the turbines and using several smaller turbines, a series effect is created, which reduces costs. The turbines are then designed and assembled in a factory before being transported to their operating site (i.e., a power plant, such as a nuclear power plant) by standard trucks. This allows for very high control over the quality and assembly process of the turbine-generator unit and reduces power plant downtime.

[0024] Indeed, if one of the turbines malfunctions, it simply needs to be replaced, and the defective turbine sent back to the factory for repair. Another advantage of having small turbines lies in their lower thermal inertia, which reduces the thermal conditioning requirements during cold starts. The turbo-alternator unit is therefore more responsive. Its increased maneuverability allows it to respond quickly to power demands in order to maintain the supply-demand balance of the electrical grid. This is all the more important given the ever-increasing share of intermittent generation sources (wind turbines, photovoltaic power plants, etc.) in the energy mix.

[0025] Furthermore, having a single alternator connected to several small turbines allows for more precise modulation of the generated electrical power over a wider range without impacting the mechanical strength of the equipment. Indeed, currently, power modulation in a turbo-alternator unit is often achieved through partial fluid injections, which negatively affect the mechanical strength of the turbine rotor (blades) and increase vibrations within the turbo-alternator unit.

[0026] Reducing the size of the turbines also reduces their footprint and makes them easier to handle.

[0027] Manufacturing, assembly and adjustment in the factory reduces the need for skilled mobile labor that would be required to perform maintenance operations on site.

[0028] Furthermore, the proposed solution offers several technical and economic advantages:

[0029] - Cost reduction by leveraging mass production.

[0030] - Finer and easier load tracking. In addition, steam management is facilitated for electricity production and / or for industrial processes based on demand.

[0031] - Mastery of manufacturing through factory assembly.

[0032] - Reduction of downtime and maintenance times by performing standard exchanges of turbine components.

[0033] - Ease of handling.

[0034] - No need for skilled labor on site for adjustment (alignment, balancing, disassembly, etc.).

[0035] - To take advantage of the large number of turbines to carry out relevant monitoring of the health of the turbines, which allows for early detection of defects.

[0036] - Small size allowing the use of quality materials (stainless steel) and conventional machining processes.

[0037] - Cost reduction through the implementation of manufacturing methods adapted to large-scale production.

[0038] - Factory balancing and factory adjustment.

[0039] The turbo-alternator unit according to the invention is advantageously and optionally supplemented by the following features, taken alone or in any of their technically possible combinations:

[0040] The intermediate shaft is engaged with the driven shaft by a bevel gear and / or a coupling. A coupling is a transmission between the ends of two rotating shafts to transfer torque from one to the other. Thus, the transmission of motion and torque between the intermediate shaft and the driven shaft is achieved reliably and safely. Indeed, in the event of an alternator failure, the transmission reduction system is guaranteed not to be damaged, and conversely, in the event of a transmission reduction system failure, the alternator is guaranteed not to be damaged.

[0041] - The coupling uses flanges and tightened bolts. This makes the coupling particularly simple and secure. - The driven shaft can be positioned vertically or horizontally. This simplifies the management of loads applied to the driven shaft.

[0042] - Each drive shaft is positioned vertically or horizontally. This simplifies the management of loads applied to the drive shaft, while also facilitating space and footprint management.

[0043] - The driven shaft is orthogonal to each drive shaft or parallel to each drive shaft. This simplifies the assembly and adjustment of the power transmission.

[0044] - For each drive stage, the turbines are identical in that drive stage. Thus, turbine standardization is possible, which simplifies their manufacture and makes them less expensive.

[0045] - The reduction ratio is between 2 and 10, preferably between 4 and 6, more preferably between 7500 / 1500 and 7935 / 1500. Such a ratio is advantageous in that it allows the efficiency of the turbines to be increased, due to their higher rotational speed, without changing the rotational speed of the driven shaft of the alternator.

[0046] - Each drive stage comprises between 2 and 64 turbines, preferably between 6 and 32 turbines, and more preferably between 16 and 32 turbines. This allows the use of smaller turbines, which are easier to manufacture, transport, and maintain.

[0047] - The turbo-alternator unit has at least two drive stages. This allows for increased power and improved overall efficiency of the turbo-alternator while limiting the size of each secondary gear.

[0048] Each turbine has a clutch located on the drive shaft, between the rotor and the primary gear. This clutch allows the rotor to be alternately coupled and decoupled from the primary gear. This enables turbine maintenance to be performed without shutting down the turbo-alternator unit, and allows the electrical power produced by the alternator to be modulated according to demand.

[0049] - The clutch is automatic, designed to disengage the rotor from the primary gear when the rotor's rotational speed is lower than the primary gear's rotational speed, and to engage the rotor with the primary gear when the rotor's rotational speed reaches the primary gear's rotational speed. This increases safety because, in the event of a turbine failure, the turbine's rotor will not be forcibly driven by the primary gear driven by the other turbines in the drive stage. - The alternator has a rated electrical output between 10 MWe and 1500 MWe, preferably between 10 MWe and 300 MWe, more preferably between 150 MWe and 200 MWe, and even more preferably between 170 MWe and 180 MWe. This allows the use of a high-power alternator while limiting the individual power output of each turbine.

[0050] - The alternator, preferably the driven shaft, is suitable for rotating at a nominal rotational speed such that fx 60 N = - -

[0051] P with:

[0052] Let N be the nominal rotational speed in revolutions per minute, f the frequency of the electrical grid, and p the number of pole pairs of the alternator. Thus, the electrical output of the alternator can be easily fed into the electrical grid. Advantageously, p is between 1 and 32, preferably between 1 and 8, more preferably between 1 and 4, and even more preferably equal to 2.

[0053] Advantageously, f is between 30 Hz and 100 Hz, preferably is between 50 Hz and 60 Hz, more preferably is equal to 50 Hz or 60 Hz.

[0054] Advantageously, when f = 50 Hz, N is equal to 750, 1500 or 3000, or when f = 60 Hz, N is equal to 900, 1800 or 3600.

[0055] - At least two turbines are arranged in a pair and are symmetrical with respect to a primary gear common to both turbines. Thus, the compactness of the turbo-alternator unit is improved.

[0056] - The turbines in at least one drive stage are regularly arranged in a star configuration, such that in that drive stage, each primary gear is conical and the secondary gear is also conical. This optimizes the distribution of forces applied to the secondary gear in the event of a turbine failure. In such a case, the forces can be easily transferred and do not cause bending of the intermediate shaft.

[0057] According to a second aspect, the invention proposes a power plant comprising a turbo-alternator unit conforming to the first aspect.

[0058] The power plant according to the invention is advantageously and optionally supplemented by the following features, taken alone or in any of their technically possible combinations: - The power plant is a nuclear power plant.

[0059] - The power plant is a thermal power plant.

[0060] - The power plant includes a closed fluid circuit, preferably a closed water-steam circuit.

[0061] - The closed circuit includes a boiler, preferably a steam generator.

[0062] - The closed circuit includes each turbine.

[0063] - The closed circuit includes a superheater.

[0064] - The closed circuit includes a condenser.

[0065] - Each turbine is powered by the boiler or by a superheater.

[0066] - Each turbine supplies the condenser or the superheater.

[0067] DESCRIPTION OF THE FIGURES

[0068] Other features, purposes and advantages of the invention will become apparent from the detailed description below, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings, given by way of non-limiting examples and on which:

[0069] Figure 1 is a schematic "system" view of a power plant comprising a turbo-alternator unit according to a first embodiment; Figure 2 is a schematic side view of a turbo-alternator according to a second embodiment; Figure 3 is a schematic side view of a turbo-alternator according to a third embodiment; Figure 4 is a schematic side view of a power plant comprising a turbo-alternator unit according to a fourth embodiment; Figure 5 is a schematic side view of a turbo-alternator according to a fifth embodiment; Figure 6 is a schematic side view of a turbo-alternator according to a sixth embodiment; Figure 7 is a schematic side view of a turbo-alternator according to a seventh embodiment.

[0070] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0071] Figure 1 represents a power plant 1 comprising a turbo-alternator unit 3. The power plant 1 is advantageously a nuclear power plant or a thermal power plant.

[0072] The turbo-alternator group 3 includes an alternator 5 and at least one drive stage E1 comprising several turbines 7.

[0073] Advantageously, each drive stage E1 comprises between two turbines 7 and sixty-four turbines 7, preferably between six turbines 7 and thirty-two turbines 7, more preferably between sixteen turbines 7 and thirty-two turbines 7.

[0074] Advantageously, as shown in Figure 1, the turbo-alternator group 3 comprises a single drive stage E1.

[0075] Advantageously, the E1 drive stage has two turbines 7.

[0076] Power plant 1 advantageously operates according to a Rankine cycle. Thus, power plant 1 comprises a closed fluid circuit, preferably a closed water-steam circuit. Within this closed circuit, power plant 1 includes a boiler 9, preferably a steam generator. The closed circuit also includes a condenser 11. Finally, the closed circuit includes each turbine 7. Power plant 1 also includes piping connecting these various components to form the closed circuit. Thus, to form the closed circuit, this piping connects the boiler 9 to each turbine 7 of the drive stage E1, each turbine 7 of the drive stage E1 to the condenser 11, and the condenser 11 to the boiler 9.

[0077] Thus, each turbine 7 of the drive stage E1 is supplied by the boiler 9. For example, each turbine 7 of the drive stage E1 is supplied with high pressure steam HP.

[0078] Each turbine 7 advantageously comprises a rotor 13 driving a drive shaft 15. Thus, each turbine 7 provides work by rotation of the rotor 13, which recovers energy from the high-pressure steam HP, and transfers it to the drive shaft 15, which then indirectly drives the alternator 5.

[0079] Each turbine 7 of the drive stage E1 is advantageously connected at its outlet to the condenser 11. Thus, each turbine 7 supplies the condenser 11. In other words, the low-pressure steam BP at the outlet of turbine 7 supplies the condenser 11, which cools and condenses the low-pressure steam BP into liquid water L. To enable cooling, the condenser 11 is cooled by a cold source SF. The cold source SF is advantageously cold water, preferably seawater, river water, or water cooled by air via one or more water-air exchangers, which passes through the condenser 11 to cool the low pressure steam BP into liquid water L. This liquid water L is then pumped by a pumping unit (for example integrated into the condenser 11) and sent to the boiler 9, in which it is again vaporized into high pressure steam HP by supplying heat from a heat source SC.The heat from this SC heat source can be derived from the combustion of a gas (e.g., natural gas or hydrogen), the combustion of coal, or any other energy-releasing material (e.g., fuel oil or waste). Alternatively, the heat from this SC heat source can be derived from the fission of atoms in a nuclear reactor, such as a SMR.

[0080] Advantageously, the alternator 5 has a rated electrical power PE between 10MWe and 1500MWe, preferably between 10 MWe and 300MWe, more preferably between 150MWe and 200 MWe, even more preferably between 170MWe and 180 MWe.

[0081] Advantageously, alternator 5 is suitable for rotating at a nominal rotational speed of 1500 revolutions per minute.

[0082] Advantageously, the alternator 5 has a driven shaft 16. The driven shaft 16 is advantageously indirectly driven by the motor shaft 15.

[0083] Preferably, the driven shaft 16 is suitable for rotating at a nominal rotational speed such that fx 60 N = - -

[0084] P with:

[0085] N is the nominal rotation speed in revolutions per minute (or rpm), f is the frequency of the electrical network, and p is the number of pole pairs of the alternator.

[0086] Advantageously, p is between 1 and 32, preferably between 1 and 8, more preferably between 1 and 4, and even more preferably equal to 2.

[0087] Advantageously, f is between 30 Hz and 100 Hz, preferably is between 50 Hz and 60 Hz, more preferably is equal to 50 Hz or 60 Hz.

[0088] Advantageously, when f = 50 Hz, N is equal to 750, 1500 or 3000, or when f = 60 Hz, N is equal to 900, 1800 or 3600. Thus, when p = 2 and f = 50 Hz, N = 1500 revolutions per minute, and when p = 2 and f = 60 Hz, N = 1800 revolutions per minute. Thus, the drive shaft 15 of each turbine 7 advantageously carries a primary gear 17, and the turbo-alternator unit 3 includes a transmission reduction system 19, which mechanically connects each primary gear 17 to the driven shaft 16 with a reduction ratio strictly greater than 1, such that each primary gear 17 is capable of rotating at a rotational speed strictly greater than that of the driven shaft 16. In other words, in normal operation, the ratio of the rotational speed of the primary gear 17 of each turbine 7 to the rotational speed of the driven shaft of the alternator 5 is equal to the reduction ratio.

[0089] Advantageously, the reduction ratio is between 2 and 10, preferably between 4 and 6, more preferably between 7500 / 1500 and 7935 / 1500.

[0090] Advantageously, the reduction system 19 includes an intermediate shaft 21. The intermediate shaft 21 carries a secondary gear 23 for each drive stage E1. Thus, in each drive stage E1, each primary gear 17 meshes with the secondary gear 23 of the drive stage E1.

[0091] Advantageously, each drive shaft 15, each primary gear 17, each secondary gear 23, the intermediate shaft 21 and the driven shaft 16 are made of steel, preferably stainless steel.

[0092] The intermediate shaft 21 can be extended to form the driven shaft 16. In this case, the intermediate shaft 21 and the driven shaft 16 form a single unit. Alternatively, the intermediate shaft 21 is meshed with the driven shaft 16 by a bevel gear and / or a coupling. A coupling is a means of transmission between the ends of two rotating shafts to transfer torque from one to the other.

[0093] Advantageously, as shown in Figure 1, the driven shaft 16 is arranged horizontally and each driving shaft 15 is arranged horizontally, such that the driven shaft 16 is parallel to each driving shaft 15.

[0094] As shown in the figures, the X-axis is a horizontal longitudinal axis, the Y-axis is a horizontal transverse axis orthogonal to the X-axis, and the Z-axis is a vertical axis orthogonal to the X-axis and the Y-axis. Thus, by "horizontal" we should understand parallel to a plane formed by the X and Y axes, and by "vertical" we should understand parallel to the Z-axis.

[0095] Advantageously, for each drive stage E1, the turbines 7 are identical in that drive stage E1.

[0096] Power modulation is entirely possible without using a clutch. This simply requires cutting off the steam supply to certain turbines 7, for example by closing valves (not shown). These turbines 7 are then driven by the alternator 5.

[0097] A second embodiment of the turbo-alternator group 3 is schematically represented in Figure 2.

[0098] The turbo-alternator group 3 according to this second embodiment differs from the turbo-alternator group 3 according to the first embodiment in that the drive stage E1 advantageously comprises six turbines 7. In order to make the figures more legible, in figure 2 and the following figures, only one turbine 7 is referenced in detail, with its steam-supplied rotor 13, its drive shaft 15 and its primary gear 17.

[0099] Furthermore, in this second embodiment, the intermediate shaft 21 is advantageously connected to the driven shaft 16 by a coupling 25. Thus, the intermediate shaft 21 and the driven shaft 16 are coaxial and fixed relative to each other, the coupling 25 being fixed. Preferably, the coupling 25 has flanges and clamped bolts.

[0100] Furthermore, in this second embodiment, the alternator 5 is arranged vertically. In other words, the driven shaft 16 is arranged vertically. Each drive shaft 15 is also arranged vertically. Each turbine 7 is thus arranged vertically. Therefore, the driven shaft 16 is parallel to each drive shaft 15.

[0101] A third embodiment of the turbo-alternator group 3 is schematically represented in Figure 3.

[0102] The turbo-alternator group 3 according to this third embodiment differs from the turbo-alternator group 3 according to the second embodiment in that each turbine 7 has a clutch 27 disposed on the drive shaft 15, between the rotor 13 and the primary gear 17.

[0103] The clutch 27 allows the rotor 13 to be coupled and decoupled from the primary gear 17. Thus, the rotor 13 can be coupled to the primary gear 17, the turbine 7 then supplying power to the alternator 5, or the rotor 13 can be decoupled from the primary gear 17, the turbine 7 then not supplying power to the alternator 5.

[0104] Advantageously, the clutch 27 is automatic. Thus, the clutch 27 is suitable for disengaging the rotor 13 from the primary gear 17 when the rotational speed of the rotor 13 is lower than the rotational speed of the primary gear 17. The clutch 27 is also suitable for coupling the rotor 13 to the primary gear 17 when the rotational speed of the rotor 13 reaches the rotational speed of the primary gear 17. Such an automatic clutch 27 is advantageously purely mechanical. Thus, it is independent of any electrical power supply, and consequently more reliable, particularly in the event of a malfunction. Such an automatic clutch 27 is preferably synchronous, more preferably synchronous with self-engagement. For example, such a synchronous automatic self-engaging clutch 27 is also known as an SSS Clutch, for "Synchro-Self-Shifting Clutch" in English, and is described in particular in document FR 1 351 989 A.

[0105] A fourth embodiment of the turbo-alternator group 3 is schematically represented in Figure 4, which schematically represents a power plant 1 comprising such a turbo-alternator group 3.

[0106] The turbo-alternator group 3 according to this fourth embodiment differs from the turbo-alternator group 3 according to the second embodiment in that it comprises at least two drive stages E1, E2, preferably exactly two drive stages E1, E2. Thus, the intermediate shaft 21 carries a secondary gear 23 per drive stage E1, E2.

[0107] Advantageously, each drive stage E1, E2 has the same number of turbines 7, for example six turbines 7 as shown in Figure 4.

[0108] In the embodiment shown in Figure 4, the power plant 1 includes, in addition to the components mentioned above in the first embodiment, a superheater 29 in the closed circuit. Thus, in this fourth embodiment, the closed circuit includes a superheater 29. To form the closed circuit, piping connects the boiler 9 to each turbine 7 of the drive stage E1, each turbine 7 of the drive stage E1 to the superheater 29, the superheater 29 to each turbine 7 of the drive stage E2, each turbine 7 of the drive stage E2 to the condenser 11, and the condenser 11 to the boiler 9.

[0109] A portion of the high-pressure steam (HP) is drawn off before entering the turbines 7 of the E1 drive stage and is sent to the superheater 29 to superheat the low-pressure steam (LP) exiting the turbines 7 of the E1 drive stage into superheated steam (VS). The superheater 29 also inherently functions as a dryer.

[0110] Each turbine 7 of the drive stage E1 is advantageously connected at its outlet to the superheater 29. Thus, each turbine 7 of the drive stage E1 supplies the superheater 29. Each turbine 7 of the drive stage E2 is advantageously supplied by the superheater 29. For example, each turbine 7 of the drive stage E2 is supplied with superheated steam VS.

[0111] Thus, each turbine 7 is supplied by the boiler 9 or by the superheater 29.

[0112] Thus, each turbine 7 of the drive stage E2 provides work by rotation of the rotor 13, which recovers energy from the superheated steam VS, and transfers it to the drive shaft 15, which then indirectly drives the alternator 5.

[0113] Each turbine 7 of the drive stage E2 is advantageously connected at the outlet to the condenser 11. Thus, each turbine 7 of the drive stage E2 supplies the condenser 11 with very low pressure steam TBP.

[0114] Thus, each turbine 7 supplies the condenser 11 or the superheater 29.

[0115] A fifth embodiment of the turbo-alternator group 3 is schematically represented in Figure 5.

[0116] The turbo-alternator group 3 according to this fifth embodiment differs from the turbo-alternator group 3 according to the second embodiment in that the intermediate shaft 21 is engaged with the driven shaft 16 by a bevel gear 31.

[0117] Thus, the intermediate shaft 21 and the driven shaft 16 are orthogonal to each other. Indeed, in this fifth embodiment, the alternator 5 is arranged horizontally. Therefore, the driven shaft 16 is arranged horizontally, while the intermediate shaft 21 is arranged vertically, and each drive shaft 15 is arranged vertically. Each turbine 7 is thus arranged in a cantilevered fashion, and the driven shaft 16 is orthogonal to each drive shaft 15.

[0118] Furthermore, in this fifth embodiment, the intermediate shaft 21 is advantageously meshed with the driven shaft 16 by a coupling 25. Preferably, the coupling 25 is fixed, more preferably with flanges and clamped bolts. In this example, the coupling 25 is located on the intermediate shaft 21 before the bevel gear 31 located at the end of the intermediate shaft 21. More precisely, the bevel gear is formed by an intermediate bevel gear 33 carried by the intermediate shaft 21 and a driven bevel gear 35 carried by the driven shaft 16, the intermediate bevel gear 33 meshing with the driven bevel gear 35. A sixth embodiment of the turbo-alternator unit 3 is schematically represented in Figure 6.

[0119] The turbo-alternator group 3 according to this sixth embodiment differs from the turbo-alternator group 3 according to the fifth embodiment in that at least two turbines 7 are arranged in a pair P1, P2 and are symmetrical with respect to a primary gear 17 common to these two turbines 7. For example, all the turbines 7 of at least one drive stage E1 are arranged in such pairs.

[0120] A seventh embodiment of the turbo-alternator group 3 is schematically represented in Figure 7.

[0121] The turbo-alternator group 3 according to this seventh embodiment differs from the turbo-alternator group 3 according to the second embodiment in that the turbines 7 of at least one drive stage E1 are regularly arranged in a star pattern, such that in this drive stage E1, each primary gear 17 is conical and the secondary gear 23 is conical.

[0122] Moreover, in this seventh embodiment, the drive stage E1 advantageously comprises eight turbines 7.

[0123] Furthermore, in this seventh embodiment, each drive shaft 15 is arranged horizontally. Thus, the driven shaft 16 is orthogonal to each drive shaft 15.

[0124] A detailed example of the installation of a turbo-alternator unit 3 comprising two drive stages E1, E2 in a power plant 1, namely a drive stage E1 referred to as "high pressure" and a drive stage E2 referred to as "low pressure", is shown below. The drive stage E1 comprises sixteen high-pressure turbines 7. The main characteristics of these small turbines 7 are:

[0125] - Rotation speed 7700 revolutions per minute.

[0126] - Useful power: 5 MW.

[0127] - Number of rotor stages 13: fourteen.

[0128] - Rotor diameter 13: 200 mm.

[0129] - Maximum inner diameter of the stator: 286 mm.

[0130] - Approximate length: 679 mm.

[0131] - Static pressure at the inlet of turbine 7: 42 bar. - Static temperature at the inlet of turbine 7: 298 °C.

[0132] - Quality of high-pressure steam VP at the inlet: dry steam.

[0133] - Mass flow rate: 12.62 kg / s.

[0134] - Static pressure at the outlet of turbine 7: 4.43 bar.

[0135] - Static temperature at the outlet of turbine 7: 147 °C.

[0136] - Low pressure steam quality at outlet: wet steam of which 90% of the mass is made up of steam.

[0137] The total power of the sixteen high-pressure 7 turbines is then 80MW.

[0138] The E2 drive stage comprises thirty-two low-pressure turbines 7, whose main characteristics are:

[0139] - Rotation speed 7935 revolutions per minute.

[0140] - Useful power: 3.23 MW.

[0141] - Number of rotor stages 13: fourteen.

[0142] - Rotor diameter: 280 mm.

[0143] - Maximum inner diameter of the stator: 580 mm.

[0144] - Approximate length: 1380 mm.

[0145] - Static pressure at the turbine inlet: 4.85 bar.

[0146] - Static temperature at the turbine inlet: 242 °C.

[0147] - Quality of superheated steam VS at the inlet: dry steam.

[0148] - Mass flow rate: 5.8 kg / s.

[0149] - Static pressure at the turbine outlet: 0.1 bar.

[0150] - Static temperature at the turbine outlet: 46 °C.

[0151] - Very low pressure steam quality TBP at the outlet: wet steam of which 90% of the mass is made up of steam.

[0152] The total power of the thirty-two low-pressure turbines is then 103.4 MW. Thus, the total power of all the high-pressure and low-pressure turbines is approximately 183 MW.

[0153] The modes and variants of embodiment can be combined with each other in any technically possible combination.

Claims

DEMANDS 1. Turbo-alternator unit (3), which comprises: - an alternator (5) comprising a driven shaft (16), - at least one drive stage (E1, E2) comprising several turbines (7), in which each turbine (7) comprises a rotor (13) driving a drive shaft (15), the drive shaft (15) carrying a primary gear (17), and - a transmission reduction system (19), which mechanically connects each primary gear (17) to the driven shaft (16) with a reduction ratio strictly greater than 1, such that each primary gear (17) is capable of rotating at a speed strictly greater than that of the driven shaft (16), the transmission reduction system (19) comprising an intermediate shaft (21) carrying a secondary gear (23) for each drive stage (E1, E2), such that in each drive stage (E1, E2), each primary gear (17) meshes with the secondary gear (23) of the drive stage (E1, E2), the turbo-alternator unit (3) being characterized in that each turbine (7) comprises a clutch (27) disposed on the drive shaft (15), between the rotor (13) and the primary gear (17), the clutch (27) allowing alternately to couple and decouple the rotor (13) from the primary gear (17).

2. Turbo-alternator group (3) according to claim 1, in which the intermediate shaft (21) is engaged with the driven shaft (16) by a bevel gear (31) and / or by a coupling (25).

3. Turbo-alternator group (3) according to claim 1 or 2, in which for each drive stage (E1, E2), the turbines (7) are identical in that drive stage (E1, E2).

4. Turbo-alternator group (3) according to any one of claims 1 to 3, wherein the reduction ratio is between 2 and 10, preferably between 4 and 6, more preferably between 7500 / 1500 and 7935 / 1500.

5. Turbo-alternator group (3) according to any one of claims 1 to 4, in which each drive stage (E1, E2) comprises between 2 turbines (7) and 64 turbines (7), preferably between 6 turbines (7) and 32 turbines (7), more preferably between 16 turbines (7) and 32 turbines (7).

6. Turbo-alternator group (3) according to any one of claims 1 to 5, which comprises at least two drive stages (E1, E2).

7. Turbo-alternator unit (3) according to any one of claims 1 to 6, wherein the clutch (27) is automatic, the clutch (27) being suitable for disengaging the rotor (13) from the primary gear (17) when the rotational speed of the rotor (13) is less than the rotational speed of the primary gear (17), and suitable for coupling the rotor (13) to the primary gear (17) when the rotational speed of the rotor (13) reaches the rotational speed of the primary gear (17).

8. Turbo-alternator group (3) according to any one of claims 1 to 7, in which at least two turbines (7) are arranged in a pair (P1, P2) and are symmetrical with respect to a primary gear (17) common to these two turbines (7).

9. Turbo-alternator group (3) according to any one of claims 1 to 8, wherein the turbines (7) of at least one drive stage (E1) are regularly arranged in a star pattern, such that in this drive stage (E1), each primary gear (17) is conical and the secondary gear (23) is conical.

10. Power plant (1), characterized in that it comprises a turbo-alternator unit (3) according to any one of claims 1 to 9, the power plant (1) preferably being a nuclear power plant or a thermal power plant.

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