Twin-spool aircraft turbine engine with at least two flows

Abstract

The present invention relates to a twin-spool aircraft turbine engine (1') with at least two flows. This turbine engine comprises a fan (10) rotated by a fan shaft (100), a low-pressure shaft (30) which connects a low-pressure turbine to a low-pressure compressor (3), and a speed reducer (4, 4'), this speed reducer (4, 4') comprising an input shaft (41) rotated by the low-pressure shaft (30) and an output shaft (42) which rotates the fan shaft (100). This turbine engine is noteworthy in that the low-pressure compressor (3) comprises at least two stages, in that at least the rotor disc (31) of the first stage (310) is mounted on the fan shaft (100) and is rotated by the latter, and in that the rotor disc of the other remaining stage or stages of the low-pressure compressor (3) is mounted on the low-pressure shaft (30) and is rotated by the latter.

Description

[0001] Twin-body aircraft turbomachine with at least two flow paths.

[0002] FIELD OF INVENTION

[0003] The invention is in the field of aeronautics.

[0004] The present invention relates more particularly to a twin-spool aircraft turbomachine with at least two flow paths, enclosed or not, equipped with a reduction gear. Turbomachines with at least two flow paths include those known as "twin-flow turbomachines" or "triple-flow turbomachines".

[0005] STATE OF THE ART

[0006] Figure 1 shows a diagram of a prior art turbofan 1. This turbofan 1 has a central longitudinal axis X-X'. In the remainder of the description and claims, the terms "radially internal" and "radially external" refer to the radial position of an element with respect to this axis.

[0007] In a conventional manner, this turbomachine comprises successively from upstream to downstream, with respect to the direction of flow of air and gases in the turbomachine (i.e. from left to right in the figures), a shrouded blower 10, also known under the English terminology as "fan", a low pressure compressor 11, a high pressure compressor 12, a combustion chamber 13, a high pressure turbine 14 and a low pressure turbine 15.

[0008] The high-pressure compressor 12 and the high-pressure turbine 14 are connected to each other by a high-pressure shaft and form a high-pressure unit. Similarly, the low-pressure compressor 11 and the low-pressure turbine 15 are connected to each other by a low-pressure shaft, so that they rotate at the same speed. Together with the shrouded blower 10, they form a low-pressure unit.

[0009] Compressors 11 and 12, combustion chamber 13 and turbines 14 and 15 together form a gas generator 16, with central axis X-X'. This gas generator 16 includes a first air flow channel 17.

[0010] A nacelle 18 surrounds the blower 10 and the gas generator 16 and delimits, with the latter, a second air flow channel 20.

[0011] Several outlet guide vanes 21 (or OGVs, from the English "Outlet Guide Vane") connect the gas generator 16 to the nacelle 18. These vanes 21 extend radially with respect to the X-X' axis and are therefore arranged across the second airflow channel 20. The air (flow F) drawn in by the blower 10 is divided between a primary airflow I, which flows in the first airflow channel (or primary vein) 17 and a secondary airflow II, which flows in the second airflow channel (or secondary vein) 20, which surrounds the gas generator.

[0012] To further increase the dilution ratio (i.e. the ratio between the air flow of the secondary flow II and that of the primary flow I, this ratio also being known by the English acronym "BPR", which means "Bypass Ratio"), it is known to introduce a reducer, which decreases the rotational speed of the blower 10 relative to that of the low-pressure shaft on which the low-pressure compressor 11 (also known by the English name "booster") and the low-pressure turbine 15 are mounted.

[0013] Figure 1 and the attached Figure 2, which is a detailed view of Figure 1, can be seen such an example of a turbomachine with a reducer 22.

[0014] The problems encountered with such an architecture are numerous and are detailed below.

[0015] First, it is necessary to have two casings at the level of two successive goosenecks 171 and 172 of the primary flow 17, namely an upstream casing 173 and an intermediate casing 174. The upstream casing 173 is positioned between the blower 10 and the low pressure compressor 11 and the intermediate casing 174 is positioned between the low pressure compressor 11 and the high pressure compressor 12. This generates pressure losses and thus penalizes the performance of the turbomachine 1.

[0016] Furthermore, it is necessary to have two stators on either side of the upstream casing 173 in the primary vein, namely an upstream stator 23 and a downstream stator 24.

[0017] The upstream stator 23, also known as "stator 0", comprises a plurality of inlet guide vanes or IGVs (Inlet Guide Vanes). It is positioned just after the fan foot 10 to straighten the primary flow I before it reaches the upstream casing 173; otherwise, the pressure losses in this upstream casing would be prohibitive.

[0018] The downstream stator 24, positioned after the upstream casing 173 and before the rotor 111 of the first stage of the low pressure compressor 11, allows the flow of the primary flow I to be channeled, after passing through the gooseneck 171 and before reaching this rotor 111.

[0019] Furthermore, the need to integrate the reducer 22 under the upstream casing 173, (i.e. in a radially internal position relative to it), requires moving the low-pressure compressor 11 downstream relative to the upstream casing 173 and therefore lengthening the turbomachine 1.

[0020] Furthermore, the outlet guide vanes 21 (OGV) must be located around the upstream casing 173 for structural reasons, which is too close to the fan 10 itself to achieve an acceptable acoustic level. It is therefore necessary to move the tip 211 of the outlet guide vanes 21 downstream for acoustic reasons, while the foot 212 of these vanes is moved upstream to be around the upstream casing 173 (see Figure 1). This results in inclined outlet guide vanes 21, which are therefore heavier and more complex to design.

[0021] In the embodiment shown in Figure 2, the low-pressure compressor 11 is a two-stage compressor, which comprises successively from upstream to downstream, after the first rotor 111, a first stator 112, then a second rotor 113 and a second stator 114. The first rotor 111 and the first stator 112 together form the first stage of this compressor and the second rotor 113 and second stator 11, the second stage.

[0022] However, in order to maintain a sufficiently high overall compression level and to guarantee good thermal efficiency (and therefore low fuel consumption), it is necessary at a minimum to increase the number of low-pressure compressor stages, in order to allow the first stages to take over the incidence and the following stages to ensure the bulk of the compression.

[0023] Indeed, a two-stage low-pressure compressor is not sufficient to meet the needs of the turbomachine architecture, because it is impossible to design a stator that straightens the incoming airflow by more than 40°, while being sufficiently robust to this incidence.

[0024] To obtain the required compression ratio, such a two-stage low-pressure compressor would either have to be overstressed (too high compression required relative to the flow rate too low passing through it), but it would then be inoperable or inefficient, or enlarged by increasing the radius of the air stream, but this would then increase the overall radius of the turbomachine and therefore its mass and drag.

[0025] In addition, a three-stage low-pressure compressor would also be conceivable, but this would make the turbomachine longer and therefore heavier.

[0026] DESCRIPTION OF THE INVENTION

[0027] One aim of the invention is to provide a turbomachine solving the aforementioned problems, and in particular a twin-body aircraft turbomachine with a reduction gear and at least two flows, which has a high bypass ratio in order to have high propulsive efficiency, while having very low levels of fuel consumption, and therefore low greenhouse gas emissions.

[0028] Another aim of the invention is to propose such a turbomachine which reduces pressure losses while gaining in mass and length and retaining good acoustic properties.

[0029] Finally, another objective of the invention is to provide such a turbomachine which provides a simplified and extended range of operability, over all phases of flight.

[0030] To this end, the invention relates to a twin-body, at least two-flow aircraft turbomachine, comprising a speed reducer, a low-pressure turbine, a low-pressure compressor, a fan driven in rotation by a fan shaft and a low-pressure shaft which connects the low-pressure turbine to the low-pressure compressor, this low-pressure shaft driven in rotation by the low-pressure turbine, this speed reducer comprising an input shaft and an output shaft whose rotational speed is lower than that of the rotational speed of the input shaft, the input shaft of the speed reducer being driven in rotation by the low-pressure shaft and the fan shaft being driven in rotation by the output shaft of the speed reducer.

[0031] According to the invention, the low-pressure compressor comprises at least two stages, at least the rotor disc of the first stage of this low-pressure compressor is mounted on the blower shaft and is driven in rotation by it at the same rotational speed as the blower, and the rotor disc of the other remaining stage or stages of the low-pressure compressor is integral with the low-pressure shaft and is driven in rotation by it.

[0032] Thanks to these features of the invention, at least one rotor disc mounted on the blower shaft rotates at a lower speed but still performs part of the compression of the incoming airflow, so that the rotor(s) of the compressor stage(s) positioned on the low pressure shaft is / are less stressed, can be less robust, and exerts / are greater compression.

[0033] The at least one rotor disc mounted on the fan shaft is positioned radially closer to the turbomachine's central axis. Consequently, the upstream end of the first gooseneck is also closer to the turbomachine's axis, resulting in a less steep first gooseneck and thus reduced pressure losses within it. The first gooseneck is also shorter, further reducing pressure losses. This improvement in the overall aerodynamics of the airflow within the low-pressure compressor, along with the reduction in pressure losses, contributes to improved turbomachine operability, meaning it can be used over a wider operating range.

[0034] According to other advantageous and non-limiting features of the invention, taken alone or in combination:

[0035] - the low pressure compressor comprises at least three stages, the rotor disc of the first stage and the rotor disc of the second stage of this low pressure compressor are mounted on the blower shaft and are driven in rotation by it at the same rotational speed as the blower, and the rotor disc of the other remaining stage or stages of the low pressure compressor is mounted on the low pressure shaft and is driven in rotation by it;

[0036] -the speed reducer includes a planetary gear mounted on the input shaft, a ring gear surrounding the planetary gear and at least one satellite gear, which is interposed between the planetary gear and the ring gear, which meshes with them and which is held by a planet carrier, the planet carrier is fixed to a housing of the turbomachine, and the ring gear is fixed to the output shaft of the speed reducer, which it drives in rotation;

[0037] - the speed reducer includes a planetary gear mounted on the input shaft, a ring gear surrounding the planetary gear and at least one planetary gear, which is interposed between the planetary gear and the ring gear, which meshes with them and which is held by a planet carrier, the ring gear is fixed to a housing of the turbomachine, and the planet carrier is fixed to the output shaft of the speed reducer which it drives in rotation.

[0038] DESCRIPTION OF THE FIGURES

[0039] Other features, purposes and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0040] Figure 1 is a longitudinal axial cross-sectional view of a twin-body, geared, twin-flow turbomachine, known from the prior art.

[0041] Figure 2 is a detailed view of the area surrounded by dotted lines in Figure 1.

[0042] Figure 3 is a diagram representing a turbomachine according to the invention.

[0043] Figure 4 is a diagram representing a first embodiment of the turbomachine speed reducer according to the invention. Figure 5 is a diagram representing a second embodiment of the turbomachine speed reducer according to the invention.

[0044] DETAILED DESCRIPTION OF THE INVENTION

[0045] In the following description and claims, elements identical to the prior art turbomachine described above bear the same numerical references.

[0046] The turbomachine 1 according to the invention differs from the turbomachine 1 previously described, in that the speed reducer 22 and the low pressure compressor 11 are replaced respectively by a reducer 4 and by a low pressure compressor 3.

[0047] As can be seen in figures 4 and 5, the blower 10 is driven in rotation by a blower shaft 100 shown partially and whose axis of rotation is coaxial with the longitudinal central axis X1 -X'1 of the turbomachine 1'.

[0048] Furthermore, the low-pressure compressor 3 comprises at least two successive stages, or even at least three or more stages. Preferably, the low-pressure compressor 3 comprises a maximum of five stages.

[0049] In Figure 3, which illustrates an example of a four-stage embodiment, and in Figures 4 and 5, which illustrate an example of a three-stage embodiment, these successive stages of the low-pressure compressor 3 are referenced respectively as 310 for the first, 320 for the second, 330 for the third, and 340 for the fourth.

[0050] Each stage 310, 320, 330 and 340 comprises a rotor disk, referenced respectively 31, 32, 33 and 34, and a stator, the latter not being shown in the figures for the sake of simplification.

[0051] Furthermore, as can be seen in Figures 4 and 5, a low-pressure shaft 30 connects the low-pressure turbine 15 to the low-pressure compressor 3, so that the low-pressure turbine 15 drives this shaft 30 in rotation. The axis of rotation of the shaft 30 is also coaxial with the longitudinal central axis X1 -X'1 of the turbomachine 1'.

[0052] The speed reducer 4 according to the invention will now be described in more detail, in connection with figures 4 and 5, which represent two variant embodiments.

[0053] In general, this 4-speed reducer includes:

[0054] -an input shaft 41, -an output shaft 42 whose rotational speed is lower than that of the input shaft 41, these two shafts 41, 42 having as their axis of rotation the longitudinal central axis X1 -X'1 of the turbomachine 1',

[0055] -a planetary gear 43, mounted on the input shaft 41 such that this shaft 41 drives the planetary gear 43 in rotation,

[0056] -a crown 44 surrounding the planetary gear 43, (and arranged around the central axis X1 -X'1 ),

[0057] -and at least one satellite 45, intercalated between the planetary 43 and the corona 44 and which meshes with them.

[0058] Each satellite 45 is held by a satellite carrier 46.

[0059] The input shaft 41 is connected to the low-pressure shaft 30, is driven in rotation by it and rotates at the same speed as it.

[0060] The output shaft 42 is connected to the blower shaft 100, which it drives in rotation. In other words, the two shafts 42 and 100 are fixed in rotation and rotate at the same speed.

[0061] According to a first variant of the speed reducer 4, shown in Figure 4, the planet carrier 46 is fixed to a housing 460 of the turbomachine 1', it is therefore fixed and furthermore, the ring 44 is integral with (fixed to) the output shaft 42 which it drives in rotation.

[0062] Thus, during the operation of the turbomachine 1', the low-pressure turbine 15 drives the low-pressure shaft 30 and the input shaft 41 to which it is attached. The planetary gear 43 is driven in rotation and rotates at the same speed as the low-pressure shaft 30. The planetary gear 43 drives the rotation of the planet(s) 45 and the rotation of the ring gear 44.

[0063] The output shaft 42, as well as the blower shaft 100 and the blower 10, therefore have a rotational speed lower than that of the input shaft 41.

[0064] As illustrated in Figure 4, which represents a first embodiment of the low-pressure compressor 3, the first stage 310 of this compressor is located upstream of the speed reducer 4, and the rotor disc 31 of this first stage is therefore mounted on the blower shaft 100. The rotor disc 31 is thus driven in rotation at the same speed as that of the blower 10 (a speed which, as previously explained, is lower than that of the input shaft 41).

[0065] Furthermore, the second stage 320 and the third stage 330 are located downstream of the speed reducer 4, and the corresponding rotor discs 32 and 33 are mounted on the low-pressure shaft 30 and are rotationally fixed to it. These discs 32 and 33 are driven in rotation by the shaft 30 at a rotational speed that is therefore higher than that of the rotor disc 31 of the first stage 310.

[0066] Figure 3 represents a second embodiment of the compressor 3, in which the rotor disc 31 of the first stage 310 and the rotor disc 32 of the second stage 320 are rotationally fixed to the blower shaft 100, while the rotor discs 33 and 34 of the third and fourth stages are mounted on the low pressure shaft 30 and rotate faster than the discs 31 and 32.

[0067] To summarize, in general, at least the rotor disc 31 of the first stage 310 is mounted on the blower shaft 100 and the rotor disc(s) of the remaining stages (i.e. the one(s) not mounted on the blower shaft 100) are mounted on the low pressure shaft 3 and are driven in rotation by it.

[0068] According to a second embodiment of the speed reducer referenced 4', shown in Figure 5, the ring 44 is fixed on a housing 440 of the turbomachine 1' and is therefore fixed and furthermore, the planet carrier 46 is fixed to the output shaft 42 which it drives in rotation.

[0069] Thus, during the operation of the turbomachine 1', the low pressure turbine 15 drives the input shaft 41 and the planetary gear 43 into rotation. The rotation of the planetary gear 43 causes the rotation of the satellite(s) 45 which mesh with the fixed ring 44, which causes the rotation of the planet carrier 46 around the axis X1 -X'1.

[0070] The different stages of the low pressure compressor 3 are arranged (distributed) respectively on the blower shaft 100 and on the low pressure shaft 30, as described previously for the first embodiment of the speed reducer 4.

[0071] Other types of speed reducers can also be used.

[0072] As described previously, the two types of gearboxes (planetary gearbox 4 and epicyclic gearbox 4') just described can be used in the turbomachine according to the invention. However, the planetary gearbox 4 is used if a reversed direction of rotation is desired between the low-pressure shaft 30 and the fan shaft 100, and the epicyclic gearbox 4' is used if the same direction of rotation is desired for these two shafts.

[0073] Furthermore, the epicyclic reducer 4' is better suited to high speed reduction ratios. Regardless of the embodiment of the speed reducer 4 or 4', the invention offers the following additional advantages, described below.

[0074] Since the airflow through the first gooseneck 171 is more compressed than in the prior art because it has already been compressed by at least one compressor stage mounted on the blower shaft 100, and since this gooseneck 171 is shorter, the upstream compressor stage(s) among the remaining compressor stages mounted on the low-pressure shaft 30 are subjected to less stress. It is therefore possible to eliminate the downstream stator 24 (see Figure 2) of the prior art, located upstream of the upstream stages (320, 330 in Figures 4 and 5, or 330, 340 in Figure 3). Thus, the entire low-pressure compressor assembly 30 is lighter and shorter axially.

[0075] Since the first gooseneck 171 is less inclined and closer to the X-X' axis, it is possible to move the outlet guide vanes 21 radially closer to this X-X' axis. Consequently, the highest point at the tip of the guide vanes is also brought closer to the central X-X' axis of the gas generator, leading to a reduction in the diameter of the nacelle 18 (see Figure 3). The "master section," which corresponds to the maximum cross-sectional area of ​​the turbomachine and is generally located at this nacelle, is therefore also reduced. This results in an overall reduction in the turbomachine's mass.

[0076] Furthermore, since the upstream casing 173 of the gooseneck 171 is positioned further downstream of the turbomachine 1' than in the prior art, the head 211 of each outlet guide vane 21 is less inclined downstream than in the prior art (see the comparison of Figures 1 and 3). Thus, each vane 21 extends in a direction almost perpendicular to the axis X1-X'1. This simplifies the design of the outlet guide vanes 21, reduces their mass, and improves their acoustic qualities.

[0077] It is also possible to position discharge valves (known by the English name VBV for "variable bleed valve") in the first gooseneck 171 to scoop water or hail or to discharge the compressor stage(s) positioned on the blower shaft 100, which was not possible with the prior art architecture, because the pressure downstream of the foot of the guide vane 21 was not sufficient to create a pressure differential with the secondary vein 20 allowing air to flow.

Claims

DEMANDS 1. Aircraft turbomachine (1') with a twin-spool and at least two flow paths, comprising a speed reducer (4, 4'), a low-pressure turbine (15), a low-pressure compressor (3), a fan (10) driven in rotation by a fan shaft (100), and a low-pressure shaft (30) which connects the low-pressure turbine (15) to the low-pressure compressor. (3), this low-pressure shaft (30) being driven in rotation by the low-pressure turbine (15), this speed reducer (4, 4') comprising an input shaft (41) and an output shaft (42) whose rotational speed is lower than that of the input shaft (41), the input shaft (41) of the speed reducer (4, 4') being driven in rotation by the low-pressure shaft (30) and the blower shaft (100) being driven in rotation by the output shaft (42) of the speed reducer, characterized in that the low-pressure compressor (3) comprises at least two stages, in that at least the rotor disc (31) of the first stage (310) of this low-pressure compressor (3) is mounted on the blower shaft (100) and is driven in rotation by it at the same rotational speed as the blower (10), and in that the disc of rotor (32, 33, 34) of the other remaining stage or of the other remaining stages (320, 330,340) of the low-pressure compressor (3) is mounted on the low-pressure shaft (30) and is driven in rotation by it.

2. Turbomachine according to claim 1, characterized in that the low pressure compressor (3) comprises at least three stages, in that the rotor disc (31) of the first stage (310) and the rotor disc (32) of the second stage (320) of this low pressure compressor (3) are mounted on the blower shaft (100) and are driven in rotation by it at the same rotational speed as the blower (10), and in that the rotor disc (33, 34) of the other remaining stage or of the other remaining stages (330, 340) of the low pressure compressor (3) is mounted on the low pressure shaft (30) and is driven in rotation by it.

3. Turbomachine according to claim 1 or 2, characterized in that the speed reducer (4) includes a planetary gear (43) mounted on the input shaft (41), a ring gear (44) surrounding the planetary gear (43) and at least one planetary gear (45), which is interposed between the planetary gear (43) and the ring gear (44), which meshes with them and which is held by a planet carrier (46), in that the planet carrier (46) is fixed to a housing (460) of the turbomachine (1'), and in that the crown (44) is fixed to the output shaft (42) of the speed reducer, which it drives in rotation.

4. Turbomachine according to claim 1 or 2, characterized in that the speed reducer (4') comprises a planet (43) mounted on the input shaft (41), a ring gear (44) surrounding the planet (43) and at least one planet gear (45), which is interposed between the planet (43) and the ring gear (44), which meshes with them and which is held by a planet carrier (46), in that the ring gear (44) is fixed to a housing (440) of the turbomachine (1'), and in that the planet carrier (46) is fixed to the output shaft (42) of the speed reducer which it drives in rotation.

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