A free turbine turbomachine comprising a device driven by the free turbine

Abstract

The present invention relates to a turbomachine comprising a gas generator (13) equipped with a first shaft (18), an accessory box (14), at least one reversible electric machine (11) connected to the accessory box (11), a free turbine (12) equipped with a second shaft (17) and driven in rotation by the gas flow of the gas generator (13), and at least one accessory (15, 16) connected to the accessory box (14). The turbomachine (10) comprises first mechanical connection means (20) configured to mechanically connect the first mechanical shaft (18) to the accessory transmission box (14) in a first configuration and to mechanically disconnect said first mechanical shaft (18) from the accessory transmission box (14) in a second configuration, and second mechanical connection means (25) configured to mechanically connect the second mechanical shaft (17) to the accessory transmission box (14) in a first configuration and to mechanically disconnect said second mechanical shaft (17) from the accessory transmission box (14) in a second configuration, the electric machine (11) being sized to drive the gas generator and said at least one accessory when starting the turbomachine.

Description

Technical Field

[0001] This invention relates to the general field of free-turbine turbines for aviation, particularly for turbojet engines or turbogenerators, and more specifically to structures for such turbines that allow the turbine to be driven via a free turbine during startup without impairing the operation of the equipment. Existing technology

[0002] A free-turbine turbine for helicopters typically includes a gas generator and a free turbine driven rotatably by the gas flow generated by the gas generator, as well as a reversible motor that can be connected to the gas generator, particularly for rotating the gas generator during the turbine's start-up phase.

[0003] Typically, a gas generator comprises at least one compressor and a turbine rotatably connected. It operates as follows: cold air entering the turbojet engine is compressed by the rotation of the compressor before being sent to the combustion chamber, where it mixes with fuel. During combustion, the combusted gases are then expelled at high speed.

[0004] The initial expansion then occurs in the turbine of the gas generator, during which the gas generator extracts the energy needed to drive the compressor and equipment. The turbine of the gas generator does not absorb all the kinetic energy of the combusted gas, and the excess kinetic energy is equivalent to the gas flow generated by the gas generator. The gas generator thus provides kinetic energy to the free turbine, causing a secondary expansion in the free turbine, which converts this kinetic energy into mechanical energy to drive receiving components, such as the rotor of a helicopter.

[0005] During the start-up phase of a turbojet engine or a conventional turbine, it is necessary to rotatably drive the gas generator, that is, to rotatably drive the compressor connected to the turbine along with the various connected devices. As mentioned in the introduction, this is one of the functions of a reversible motor, which is typically an electric motor capable of reversibly operating as a generator.

[0006] like Figure 1As shown, this schematically illustrates a prior art free-turbine turbine for startup, in which a motor 1, in operation, drives the mechanical shaft 2 of a gas generator 3 until the rotation of this mechanical shaft is sustained by fuel combustion. During the startup phase, the rotation of the gas generator shaft by a reversible motor operating in electric motor mode also drives equipment items, not shown in the figure, which can be driven by the shaft 2 via an accessory transmission box. This supplies fuel and oil to the turbine, circulates air in the compressor 4, and thus delivers compressed air to the combustion chamber 5 to initiate combustion. This combustion then produces a gas flow that rotates to drive the turbine 6 of the gas turbine 3, after which the compressor 4 and equipment are rotated without motor assistance, indicating that the gas generator 3 operates independently, signifying the end of the turbine startup phase.

[0007] In addition, for such Figure 1 The turbine shown, coupled to the receiver 7 on the shaft 8 of the free turbine 9, such as a second motor or helicopter rotor associated with the main drive box when available, can meet the demand for supplying mechanical power or generating high power.

[0008] exist Figure 1 On the turbine shown, equipment such as fuel pumps and oil pumps are mechanically connected to the shaft 2 of the gas generator 3 via an accessory transmission box.

[0009] Equipment items that require the extraction of mechanical energy to be driven in a rotating manner, such as pumps, are also called accessories and are typically mounted on an accessory drive housing, which includes at least one gear train to adapt to the rotational speed of the accessory.

[0010] Once the startup phase is complete, it is known that a reversible motor is used in generator operation mode to generate non-propulsive electrical energy (e.g., 28V mains) to power electrical equipment. Motor 1 generates electrical energy by drawing mechanical power from shaft 2 of gas generator 3; the rotational kinetic energy drawn from the gas generator is converted into electrical energy by the motor.

[0011] If no electricity generation is required, the motor 1 can be non-reversible and consist of a single starter.

[0012] Figure 2 The solid lines show the ratings of shaft 2 of gas generator 3, and the dashed lines show the variations in the ratings of shaft 8 of free turbine 9 over time and with possible configurations of the turbine generator. It can be seen that the variations in the ratings of these two shafts are independent. The exit point from the start-up phase is also indicated.

[0013] For a turbojet engine with a free turbine and a conventional starting system using a reversible motor, mechanical extraction from the shaft of the gas generator used to generate electricity by the reversible motor 1 has an adverse effect on the performance of the gas generator in generator operation mode.

[0014] This is because, during flight, the change in mechanical power extracted from the gas generator by motor 1 and the equipment manifests as a shift in the engine's operating line on the compressor map. This shift corresponds to a surge margin that must be specified, and its consequences are:

[0015] - Optimize the work line by prohibiting the use of the compressor at the optimal pressure ratio, which is detrimental to the engine;

[0016] Therefore, it reduces stability and affects fuel consumption per unit.

[0017] For this type of configuration, one solution to avoid drawing mechanical power from the gas generator to generate electricity includes using a motor with a disengagement clutch system for starting, and using another motor for... Figure 1 The fixed-to-free turbine motor shown in the diagram is disadvantageous in terms of quality and cost, and is rarely used in practice.

[0018] Document FR 2 929 324 discloses a known structure for starting a free-turbine turbine without adding a specific generator. Compared to... Figure 1 The turbine shown includes two electric motors. This technical solution can reduce overall mass and cost, and improve the reliability of the turbine generator. The technical solution described in this document includes a switching system using two freewheels, which can start the gas generator of a free-turbine turbojet engine and then generate non-propulsive electrical energy by extracting mechanical energy from the free turbine shaft. The device is driven via the gas generator and an accessory transmission box.

[0019] By avoiding the drawbacks of extracting kinetic energy from the gas generator, and especially the problem of the engine's operating line shifting on the compressor map due to changes in the mechanical power extracted by the motor during flight, this solution can particularly improve the transient performance of the gas generator.

[0020] This structure with two freewheels is advantageous for helicopter turbines, as it avoids driving the main rotor via an electric motor during the start-up phase. In particular, since the freewheel is mechanically connected to the main rotor, the connection between the shaft of the freewheel and the main rotor, which cannot be separated during the start-up phase, would require at least an excessively large energy storage system so that the electric motor can obtain sufficient energy to rotate and drive the entire power line (including the main rotor).

[0021] To improve the performance of a free-turbine turbine, all equipment driving the turbine via the free turbine would also be beneficial. However, since the performance of the fuel pump is related to its rotational speed, speed variations of the free turbine after the start-up phase will not allow or will severely affect the design of the fuel system components to ensure proper turbine startup. Summary of the Invention

[0022] To this end, the present invention provides a free turbine that drives one or more motors with sufficient power, the motors having a simplified switching system that can optimize quality, cost and reliability.

[0023] In the subject matter of this invention, a turbine is provided, comprising a gas generator having a first mechanical shaft, at least one reversible motor, a free turbine having a second mechanical shaft and rotatably driven by a gas flow generated by the gas generator, an accessory transmission case, a mechanical power transmission device in a helicopter environment, and at least one accessory connected to the accessory transmission case.

[0024] According to the technical features of the present invention, the turbine further includes a first mechanical connection device configured to mechanically connect the first mechanical shaft to the accessory drive box in a first configuration and to mechanically separate the first mechanical shaft from the accessory drive box in a second configuration, and a second mechanical connection device configured to mechanically connect the second mechanical shaft to the accessory drive box in the first configuration and to mechanically separate the mechanical shaft from the accessory drive box in a second configuration, wherein the size of the motor is designed to drive the gas generator and the at least one accessory during turbine startup.

[0025] The turbine according to the invention includes a motor and two mechanical connection devices. This allows both the joint function of starting the gas generator and generating high electrical power on the motor, while also preventing the free turbine and rotor from being driven by the motor during the start-up phase, thus reducing inertia and drag torque during startup. Furthermore, once the turbine is started, this configuration allows the free turbine to drive the attachments and rotor. Specifically, the motor can initiate the rotation of the attachments and the gas generator until the gas generator can operate independently. This is because once the free turbine exceeds a certain power, above which the second mechanical connection device mechanically connects a second mechanical shaft to the attachment drive housing, the motor can operate in generator mode driven by the free turbine via the attachment drive housing, thereby supplying power to other components.

[0026] Furthermore, in the event of a free turbine shaft breakage during operation, the structure according to the invention can directly affect the drive of accessories (including the fuel pump), which has the direct effect of immediately cutting off the engine and thus limiting the overspeed of the free turbine. This structure serves to protect the free turbine in overspeed conditions.

[0027] According to a first aspect of the turbine, the turbine may also include a control unit for the motor, the control unit being configured to put the motor into motor mode during turbine startup and to put the motor into generator mode when the second connection device is in its first configuration.

[0028] Once the gas generator reaches its rated capacity, allowing it to operate independently, the power supplied by the motor is reduced (to the rated power of the free turbine) by separating the gas generator from the accessory drive housing, as the required energy is now only the energy needed to drive the accessory.

[0029] The transition phase between the independent operation of the gas generator and the free turbine being connected to the accessory drive box to allow the motor to operate in gas generator mode can thus maintain the speed of the equipment item or accessory high enough to ensure its proper operation. During the transition phase, the motor continues to operate in motor mode but only for the accessory.

[0030] According to a second aspect of the turbine, the second mechanical connection device is in its second configuration from the turbine's start-up phase until the operating parameters of the second mechanical shaft or the second mechanical connection device have exceeded a power threshold. Above the power threshold, the free turbine is in power configuration, which allows it to drive the at least one accessory without the assistance of an electric motor.

[0031] The operating parameter value corresponding to the threshold is preferably greater than the value of the operating parameter when the first shaft reaches the speed threshold leaving the start-up phase, above which the free turbine is in its power configuration. In other words, a threshold appears after the moment the gas generator becomes independent, above which the free turbine is able to drive these accessories. Once the parameters of the second mechanical shaft or motor have exceeded the power threshold, the motor is set to operate in gas generator mode.

[0032] According to a third aspect of the turbine, the first mechanical connection device may include a first freewheel, and the second mechanical connection device may include a second freewheel.

[0033] According to the fourth aspect of the turbine, the first mechanical connection device and the second mechanical connection device may be included in the housing of the accessory transmission box.

[0034] Therefore, the pinion gear in the accessory gearbox can be adapted to the speed of a device (such as a fuel pump or oil pump) that is mechanically connected to the first mechanical shaft (i.e., the gas generator).

[0035] According to a fifth aspect of the turbine, the turbine may also include an additional accessory drive box connected to the first mechanical shaft to continuously connect additional accessories directly to the gas generator.

[0036] In another aspect of the invention, an aircraft with a rotary wing is provided, comprising at least one turbine as defined above, a main transmission housing, and a mechanical connection between the free turbine and the main transmission housing. Attached Figure Description

[0037] As already described Figure 1 This is a simplified schematic diagram of a free turbine in the prior art.

[0038] As already described Figure 2 yes Figure 1 A graphical representation of the time-varying ratings of the gas generator shaft of the turbine and the free turbine shaft, and possible structural variations of the turbine generator.

[0039] Figure 3 This is a block diagram of a free turbine according to an embodiment of the present invention.

[0040] Figure 4 This illustrates a control method according to one implementation mode. Figure 3 A flowchart of the turbine startup method.

[0041] Figure 5 yes Figure 3 A graphical representation of the time-varying ratings of the gas generator shaft of the turbine and the free turbine shaft, and possible structural variations of the turbine generator. Detailed Implementation

[0042] Figure 3 A free turbine 10 according to an embodiment of the present invention is schematically shown.

[0043] The turbine 10 includes an electric motor 11, a free turbine 12, a gas generator 13, an accessory transmission box 14, a fuel pump 15, and an oil pump 16.

[0044] The gas generator 13 includes a shaft 18 connected and mechanically linked to an accessory drive housing 14 via a first mechanical connection 20. The first mechanical connection 20 is configured to mechanically connect the shaft 18 of the gas generator 13 to the accessory drive housing 14 in a first configuration and to mechanically separate it from the accessory drive housing 14 in a second configuration, specifically for separating the shaft 18 of the gas generator 13 relative to the shaft 17 and the motor 11. Therefore, the shaft 18 of the gas generator 13 is selectively connected to the motor 11 via the accessory drive housing 14.

[0045] The free turbine 12 includes a shaft 17 connected and mechanically linked to an accessory drive housing 14 via a second mechanical connection 25. The accessory drive housing 14 is mechanically connected to a motor 11. The second mechanical connection 25 is configured to mechanically connect the shaft 17 of the free turbine 12 to the accessory drive housing 14 in a first configuration and to mechanically separate it from the accessory drive housing in a second configuration, specifically for separating the shaft 17 of the free turbine 12 relative to the shaft 18 and the motor 11. Thus, the shaft 17 of the free turbine 12 is selectively connected to the motor 11 via the accessory drive housing 14.

[0046] The turbine 10 also includes a main drive housing 26 and a main rotor 27. The free turbine 12 may also include another mechanical shaft 28, which may be an extension of shaft 17 and connects the free turbine 12 to the main drive housing 26, which is also connected to the main rotor 27. The free turbine is thus connected to the main rotor 27 via the main drive housing 26.

[0047] The accessory drive housing 14 is also mechanically connected to the fuel pump 15 on one hand and to the oil pump 16 on the other. In other embodiments, other accessories may be mechanically connected to the accessory drive housing 14.

[0048] The first mechanical connecting device 20 and the second mechanical connecting device 25 each include a free wheel.

[0049] The turbine 10 also includes a unit 30 for controlling the motor 11, which is configured to put the motor 11 into motor mode during the start-up phase of the turbine 10 and to put the motor 11 into generator mode when the second mechanical connection device 25 is in its first configuration.

[0050] The first connection device 20 is mechanically configured to mechanically connect the motor 11 to the gas generator 13 via the shaft 18 during the start-up of the turbine 10.

[0051] Furthermore, the first connecting device 20 is mechanically configured to disconnect the gas generator 13 from the motor 11 when the gas generator 13 reaches the exit speed threshold of the start-up phase.

[0052] The second connection device 25 is mechanically configured such that when the free turbine 12 is in a power configuration that allows it to drive the at least one accessory without the assistance of the motor 11, the motor 11 is mechanically connected to the free turbine 12 via the shaft 17.

[0053] Figure 4 A flowchart of a method for controlling the start-up of a turbine 10 according to an embodiment of the present invention is shown.

[0054] Figure 5 The chart uses solid and dashed lines to represent the use of... Figure 4 When the method is started, Figure 3 The ratings of the shaft 18 of the gas generator 13 of the turbine 10, and the ratings of the shaft 17 of the free turbine 12, vary over time and vary with the possible configuration of the turbine generator.

[0055] The method for starting the turbine 10 includes a first step 405, wherein the motor 11 is placed in motor mode and started to initiate rotation of the shaft 18 of the gas generator 13 via the accessory drive housing 14, a first connecting device 20 is disposed in its first configuration to connect the shaft 18 of the gas generator 13 to the accessory drive housing 14, and a second connecting device 25 is disposed in its second configuration to mechanically disengage the shaft 17 of the free turbine 12 from the accessory drive housing 14. Specifically, when the accessory drive housing 14 is rotated by the motor 11, the first mechanical connecting device 20 of the free turbine can automatically transmit the necessary torque to rotate the gas generator 13.

[0056] In the second step 410, when the rated value of the shaft 18 of the gas generator 13 exceeds the first threshold, the gas generator 13 can operate independently, i.e., without any assistance from the motor 11. At this time, the first connecting device 20 is placed in its second configuration to separate the gas generator 13 from the accessory drive box 14 and thus from the motor 11.

[0057] However, motor 11 remains in motor operation mode to drive accessories 15 and 16 via accessory drive box 14.

[0058] In the third step 415, when the rating of the shaft 17 of the free turbine 12 exceeds the second threshold, the free turbine 12 is in so-called power operation, allowing it to drive the accessories. At this time, the second connecting device 25 is placed in its first configuration to mechanically connect the free turbine 12 to the accessory drive housing 14, thereby driving the accessories 15 and 16.

[0059] In the fourth step 420, the motor 11 is simultaneously put into generator operation mode in the third step 415.

[0060] Therefore, the motor 11 can operate as a generator and generate electrical energy by rotating the shaft 17 of the free turbine driven by the rotational motion of the free turbine 12, which itself is driven by a gas flow supplied by the gas generator 13.

[0061] The transition phase between the independent operation of the gas generator 13 and the powered operation of the free turbine 12 can thus maintain the rotational speed of the equipment or accessories, during which the motor 11 continues to operate in electric motor mode but only drives the accessories, and the rotational speed is high enough to ensure its proper operation.

[0062] Therefore, the free turbine according to the present invention can optimize the switching system and thus the quality, cost and reliability of the turbine.

Claims

1. A turbine (10) comprising a gas generator (13), the gas generator including a first mechanical shaft (18), an accessory drive housing (14), at least one reversible motor (11) connected to the accessory drive housing (14), a free turbine (12) provided with a second mechanical shaft (17) and rotatably driven by a gas flow generated by the gas generator (13), and at least one accessory (15, 16) connected to the accessory drive housing (14). characterized in that The turbine (10) further includes a first mechanical connection device (20) configured to mechanically connect the first mechanical shaft (18) to the accessory drive box (14) in a first configuration of the first mechanical connection device and to mechanically separate the first mechanical shaft (18) from the accessory drive box (14) in a second configuration of the first mechanical connection device, and a second mechanical connection device (25) configured to mechanically connect the second mechanical shaft (17) to the accessory drive box (14) in a first configuration of the second mechanical connection device and to mechanically separate the second mechanical shaft (17) from the accessory drive box (14) in a second configuration of the second mechanical connection device, wherein the motor (11) is sized to drive the gas generator and the at least one accessory during the start-up of the turbine.

2. The turbine (10) according to claim 1, further comprising a control unit (30) for the at least one motor (11), the control unit (30) being configured to place the motor (11) in motor mode during the start-up of the turbine (10) and to place the motor (11) in generator mode when the second mechanical connection device (25) is in its first configuration.

3. The turbomachine (10) of claim 2, wherein, The second mechanical connection device (25) is in its second configuration from the start-up phase of the turbine (10) until the parameters of the second mechanical shaft (17) or the second mechanical connection device (25) have exceeded a power threshold, above which the free turbine (12) is in a power configuration that allows it to drive the at least one accessory without the assistance of the motor (11).

4. Turbomachine (10) according to any one of claims 1 to 3, wherein The first mechanical connection device (20) includes a first free wheel, and the second mechanical connection device (25) includes a second free wheel.

5. The turbine (10) according to any one of claims 1 to 4, wherein, The first mechanical connection device (20) and the second mechanical connection device (25) are contained in the housing of the accessory transmission box (14).

6. The turbine (10) according to any one of claims 1 to 5 further includes an additional accessory drive box connected to the first mechanical shaft (18) for continuously directing additional accessories to the gas generator (13).

7. An aircraft with a rotary wing, comprising at least one turbine according to any one of claims 1 to 6, a main drive housing (26), and a mechanical connection device (28) between the free turbine (12) and the main drive housing (26).

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