BE1027469A1 - TURBOMACHINE ARCHITECTURE WITH ACCELERATED BOOSTER - Google Patents

Abstract

The subject of the invention is a turbomachine (2), such as an aircraft turbojet, comprising: a turbine (32) rotating a transmission shaft (34); a fan (18) integral in rotation with the transmission shaft (34); a low pressure compressor (24) comprising rotor blades (40); the turbomachine (2) comprising a device (36) driving the rotor blades (40) in rotation at a speed greater than that of the fan.

Description

Description

TURBOMACHINE ARCHITECTURE WITH ACCELERATED BOOSTER Technical Field The invention relates to the field of the design of a turbomachine, in particular an airplane turbojet or an aircraft turboprop with a low pressure compressor driven by a transmission shaft. The invention also relates to methods of implementing such a turbomachine. PRIOR ART In order to gain in compactness and weight, turbomachines with counter-rotating turbines have been developed. Instead of an alternation between rotating vanes and fixed vanes, a succession of vanes rotating alternately in one direction and then in the other are provided. This allows an identical rate of expansion of the gas flow but over a shorter axial distance. This also means that the turbines turn less quickly for the same energy delivered by the combustion.

The compressors of the turbomachine being driven by the rotation of the turbines, it becomes necessary, due to slower rotation of the turbines, to multiply the compression stages in order to obtain a compression ratio similar to that obtained with turbines rotating more rapidly. Thus, the gain obtained in terms of the size of the turbines is partly lost at the level of the compressors.

Summary of the invention Technical problem The object of the invention is to provide a turbomachine architecture in which a compression ratio is guaranteed without compromising the size of the compressor. In particular, the objective is to ensure that the rotor blades of the low pressure compressor rotate at high speed even in a configuration where the speed of the turbines is "slower".

Technical solution The subject of the invention is a turbomachine, such as an aircraft turbojet, comprising: a turbine, rotating a transmission shaft; a fan integral in rotation with the transmission shaft; a low pressure compressor comprising rows of rotor blades; and a device driving at least one of the rows of rotor blades in rotation at a speed greater than that of the fan.

According to advantageous embodiments of the invention, the turbomachine can comprise one or more of the following characteristics, taken in isolation or according to all the possible technical combinations: the device driving the blades comprises an epicyclic train with an acceleration ratio close to 2, the epicyclic gear being made up of an internal planetary gear, at least one planet gear carried by a planet gear carrier and an outer ring gear. The acceleration ratio, defined by the output speed of the train over its input speed, can be between 1.5 and 2.5; the transmission shaft is integral with the planet carrier, the rotor blades of the compressor are integral with the outer ring gear and the internal sun gear is integral with the casing of the turbomachine; - The transmission shaft is integral with the outer ring gear, the rotor blades of the compressor are integral with the planet carrier and the internal sun gear is integral with the casing; - The drive device comprises an electric motor comprising a rotor integral with the rotor blades and the electrical energy of which comes from a generator whose rotor is driven in rotation by the transmission shaft, the rotor blades preferably being driven at least twice the rotational speed of the blower; - the stator of the electric motor is integral with the casing.

- the rotor of the generator is integral with the transmission shaft and the stator of the generator is integral with the casing; - the drive device comprises an electric motor comprising a rotor integral with the rotor blades and whose electrical energy comes from a generator whose rotor is rotated by a high pressure turbine via a shaft, the stator of the generator being integral with the housing; - Means for varying the speed and direction of rotation of the rotor of the electric motor; - the stator of the electric motor is integral with the crown of the epicyclic gear train.

- the generator is axially remote from the electric motor; - Mechanical means are provided for securing the rotor of the electric motor to the stator of the electric motor, in particular a brake clutch; the outer ring gear extends downstream from the epicyclic gear in a tubular portion, in that the inner sun gear is supported by a spindle integral with the casing, the spindle being at least partially fitted into the tubular portion of the outer ring gear.

The subject of the invention is also a method for implementing the turbomachine, remarkable in that it comprises a step of regulating the speed and the direction of rotation of the electric motor in order to obtain, from a speed measured transmission shaft rotation, a setpoint rotation speed of the low-pressure compressor.

The subject of the invention is also a method for implementing the turbomachine, remarkable in that it comprises a step of regulating the torque delivered by the electric motor in order to obtain, from a measured torque of the transmission shaft, a setpoint torque of the low pressure compressor.

In general, the advantageous modes of each subject of the invention are also applicable to the other subjects of the invention.

Each object of the invention can be combined with other objects, and the objects of the invention can also be combined with the embodiments of the description, which in addition can be combined with each other, according to all the possible technical combinations, unless the contrary is true. is not explicitly mentioned.

Advantages Provided The various embodiments presented here make it possible to make the turbomachine more compact while guaranteeing a suitable compression ratio at the level of the low pressure compressor.

In addition, the teaching of the invention makes it possible to adapt the design to the desired compression ratio either by choosing the reduction ratio of the epicyclic train, or by controlling the electric motor.

In particular, the embodiment with the electric motor allows total independence of the speed of the compressor with respect to the speed of the transmission shaft; the speed of the compressor can therefore be adjusted optimally with respect to the engine speed, in order to optimize the efficiency of the turbomachine. Brief description of the drawings FIG. 1 represents an axial turbomachine according to the invention; FIG. 2 represents a part of an axial turbomachine according to a first embodiment of the invention; FIG. 3 represents a part of an axial turbomachine according to a second embodiment of the invention; FIG. 4 represents a part of an axial turbomachine according to a third embodiment of the invention; Description of the Embodiments In the following description, the terms "internal" (or "internal") and "external" (or "external") refer to a positioning relative to the axis of rotation of a turbomachine. The axial direction corresponds to the direction along the axis of rotation of the turbomachine. The radial direction is perpendicular to the axis of rotation. Upstream and downstream refer to the main flow direction of the flow in the turbomachine. The term “integral” is understood as integral in rotation, and in particular rigidly linked.

By abuse of language, the expression the "compressor rotates" or any equivalent expression means that the rotor of such a compressor is in rotational movement. Likewise, the speed of rotation of the electric motor denotes by abuse of language the speed of rotation of the rotor of the electric motor with respect to its stator.

The figures show the elements schematically, in particular without certain assembly or sealing elements.

FIG. 1 represents a turbomachine 2, and more exactly a double-flow turbojet. The turbomachine 2 has an axis of rotation 4 which can also form an axis of axial symmetry. The turoomachine 2 has an annular inlet 6 which divides into a primary vein 8 and a secondary vein 10 by virtue of a separating nozzle 12 of circular shape. These veins 8 and 10 are passed through, respectively, a primary flow 14 and a secondary flow 16, which meet at the outlet of the turbomachine.

The primary flow 14 and the secondary 16 are annular flows coaxial and fitted into one another.

The secondary flow 16 is accelerated by a fan 18 placed at the inlet 6 and generating a thrust reaction.

This can be used for the flight of an aircraft.

Diffuser blades 20 may be arranged in the secondary stream and be configured in order to increase the axial component of the speed of the secondary stream 16. The blower 18 may be disposed upstream of the primary stream 8 and of the secondary stream 10, in particular at an axial distance from these veins.

Alternatively, the fan may be of the non-ducted type, for example with a double counter-rotating rotor.

It can be placed around the primary vein.

The turbomachine 2 comprises a compression zone, a combustion chamber 22 and an expansion zone for the primary flow 14. The compression zone is formed by two compressors, including an upstream compressor 24 (also called a “low pressure compressor”) and a downstream compressor 26. The downstream compressor 26, also called a high pressure compressor, can be placed at the inlet of the combustion chamber 22. Downstream of the combustion chamber 22, the turoomachine 2 can have a high pressure turbine 28 coupled to a high pressure shaft 30, then a low pressure turbine 32 coupled to a low pressure shaft 34. The shafts 30, 34 can rotate at different speeds from each other and be fitted one inside the other.

These turbines 28, 32 can form the zone of expansion of the air flow 14. Alternatively, two counter-rotating turbines can be provided driving respective transmission shafts in opposite directions.

In operation, the mechanical power received from the turbines 28, 32 is transmitted via the shafts 30, 34 so as to set the compressor 26 and the fan 18 in motion. The compressors 24 and 26 have several rows of rotor blades associated with rows of stator vanes.

The rotation of the rotors around their axis of rotation 4 thus makes it possible to generate a flow of air and to gradually compress the latter until it enters the combustion chamber 22. At the inlet of the duct 8 is a first annular row of stator vanes 37 near the nozzle 12.

The low pressure compressor 24 comprises stator vanes 39 and rotor vanes 40 interposed between the stator vanes 39. The compressor 24 can optionally end with two successive rows of stator vanes 39. According to the invention, the rotor of the compressor 24 is driven in rotation by means of a device 36 driving the blades 40 by amplifying or reducing the speed of rotation of the turbines. This device 36 will be described in more detail below. This device 36 allows the rotation of the fan 18 and of the two compressors 24, 26 at three respective potentially different speeds, without requiring three turbines rotating at three different speeds.

In a variant that is not illustrated, at least one of the stator rows 39 is replaced by a row of counter-rotating rotor blades, that is to say with a direction of rotation opposite to the blades 40.

The stator of the turbomachine 2 can comprise several support casings, including an upstream casing 47 and a downstream casing 49 arranged on either side of the low pressure compressor 24. The downstream casing 49 is also called an intermediate casing. These housings 47, 49 may include annular sleeves defining axial sections of the primary stream 8. They may have substantially radial support arms (called "struts") 46, 48 radially crossing the stream 8. The annular sleeves may have swan neck profiles. They can mark reductions in the diameter of the primary vein 8, as well as its progressive convergence.

The upstream and downstream housings 47, 49 and their arms 46, 48 can support the device 36 driving the vanes 40. Bearings are also provided to support in rotation the fan 18, the shaft 34, or rotating parts of the device 36.

Downstream of the arms 48 is the high pressure compressor 26 provided with stator blades 50 and rotor 52. The latter are driven in rotation by means of the shaft 30. In other embodiments, the rotor blades of the high pressure compressor 26 can be driven by the shaft 34 or the rotor of the low pressure compressor 28, optionally via a reduction gear.

FIG. 2 illustrates an enlarged part of the turbomachine 2 of FIG. 1, with a focus on the device 36 driving the blades 40, according to a first embodiment.

The device 36 driving the vanes 40 comprises an internal sun gear 60 integral with the casing arm 48. A spindle 54 composed for example of axial arms connected to the arms 48 and an upstream cylindrical portion, supports the sun gear 60. The human being. Those skilled in the art will recognize that this is only an example of an assembly making it possible to attach the sun gear 60 to the housing. Satellites 62, of which only one is visible in the section of FIG. 2, mesh with the internal sun gear 60. The satellites can have a double rotational movement, around their axis 64 and around the axis 4. By abuse of language, we will speak in the present application of the axis 64 to designate both the geometric axis of axisymmetry of a satellite 62 and the physical axis or pin, around which the satellite 62 rotates.

A ring gear 66 (also called an external planetary gear) meshes with the planet wheels 62. In the embodiment of FIG. 2, the rotor of the low pressure compressor 44 is integral with the ring gear 66.

The axes 64 are assembled to a ring or a planet carrier disc 68. Thus, when the planet carrier 68 rotates on itself around the axis 4, the satellites 62 travel through interplanetary space.

In the example illustrated in FIG. 2, the shaft 34 drives the planet carrier 68 and the fan 18. In an embodiment not shown, shaft 34 drives the ring gear 66, the sun gear 60 is fixed and the planet carrier 68 drives the rotor 44 of the compressor 24.

The arm of the housing 48 being fixed, the ring gear 60 is kept stationary and the train 36 behaves like a single gear: the rotor 44 rotates at a faster speed than the shaft 34, with a fixed speed ratio and dictated by the ratio of the diameters of the elements of the train 36. The acceleration ratio can for example be close to 2. Suitable bearings 80, 90 can support the shaft 34 and the ring 66 in rotation. The housing 47, via an adapted design of flanges, makes it possible to contain the bearings 80, 90.

The ring 66 continues downstream in a tubular portion 67 in which the fuse 54 is fitted.

FIG. 3 represents a turbomachine 102 according to a second embodiment of the invention. Only the elements which are different from the embodiment of FIG. 2 are incremented by 100. In this configuration, the device 136 driving the vanes 40 of the compressor 24 comprises a generator 103 and an electric motor 110. The rotor 104 of the electric generator 103 is integral with the 34 BP shaft. The stator 106 of this same generator 103 is integral with the support arm 46, it is placed inside the arm 46. Alternatively, the generator 103 can be driven by the HP shaft 30 (see FIG. 1) and be placed. at another location (for example downstream) of the turbomachine. The electric motor 110 is electrically connected, directly or indirectly, to the generator 103. The stator 112 of the motor 110 is also integral with the arm 46, placed outside the arm 46. The rotor 114 of this motor 110 is integral with the rotor 44 of the low-pressure compressor 24. In operation, the generator 103 transforms the energy of rotation of shaft 34 into electrical energy, and thanks to this energy the motor 110, 114 turns the low-pressure compressor 24. This system makes it possible to return the speed rotation speed of the low pressure compressor 24 independent of the shaft rotation speed

34. Those skilled in the art will know how to provide the appropriate intermediate electrical components between the generator and the motor (eg, inverter, battery, rheostat, etc.). Also in this example, the fan 18 is driven by the shaft 34. Thus, the rotational speed of the compressor 24 can be faster than the rotational speed of the fan 18. These rotational speeds are therefore decoupled in order to be able to optimize. the speed of the compressor independently of that of the turbines. FIG. 4 represents a turbomachine 202 according to a third embodiment. Only the elements which are different from the embodiment of FIG. 1 are incremented by 200. This embodiment can be considered as a combination of the teachings of the two preceding embodiments. In this example, the device 236 driving the blades of the compressor 24 comprises an epicyclic train 36 combined with a generator 203 / electric motor 210. The epicyclic train 36 may be similar to the train 36 in FIG. 2. The generator 203 / motor torque 210 may be similar to the 103/110 torque of FIG. 3. A schematic representation is chosen here in which the train 36 is that of FIG. 2 but the generator 203 / motor 210 torque is different from that 103/110 of FIG. 3. The tubular portion 67 downstream of the ring 66 supports the stator 212 of the electric motor 210. Thus, it is here a "rotating stator" 212. The rotor 214 can rotate at an absolute speed faster or less. faster than stator 212. In this example, generator 203 is encapsulated in rocket 54.