FR3035156A1 - DOUBLET TURBOMOTOR WITH CONTRAROTATIVE PROPELLERS HAS BEFORE THE GAS GENERATOR - Google Patents

Abstract

The invention relates to a motor comprising a thruster with a pair of counter-rotating propellers (31, 32), a gas generator (5) supplying a power turbine (53), the pair of propellers being rotated by the shaft (53A) of the power turbine through a speed reducer, the axis of rotation (XX) of the pair of propellers being non-coaxial with that (YY) of the power turbine, characterized by the fact that the speed reducer comprises a differential gear train (7) with a first stage (6) comprising a single gear train between the turbine shaft (53A) and the differential gear (7).

Description

BACKGROUND OF THE INVENTION 1 Turbomotor with a pair of counter-rotating propellers arranged upstream of the gas generator. The present invention relates to the field of aeronautical propulsion. It aims a twin engine propeller driven by a gas turbine engine.

State of the art Propeller-doublet engines are referred to in the art as "open rotor" or "unducted fan" motor. They are distinguished in fact multiflux turbojets by the use of a propeller instead of a blower. It is also formed of two coaxial propellers contrarotative. The development of these engines is an architecture where the propellers are either at the rear of the gas generator and designated "pusher" or at the front of the latter and designated "puller". The invention relates to an engine of the latter type. The prior art shows for this case that the propellers, forming the propellant, and the gas generator are coaxial, in the extension of one another. The engine is said online. Several elements or parameters are to be considered in the adoption of an architecture according to this scheme, such as the drive mode of the propeller formed by the two propellers, the propeller hub ratio and the disposition of the entry sleeve. air.

The drive of the propellers by the power turbine coupled to the gas generator, rotating at a higher speed than the propellers, is performed through a differential speed reducer. The speeds, the torque ratio and the speed ratio between the counter-rotating propellers of an open rotor are derived from an aero acoustic optimization. For a differential gearbox, the ratio of the torques between the propellers depends on the reduction ratio 10 - in general a reduction ratio of between 7.5 and 12. The mass of the differential transmission is related to the size of the wheels. For a given ratio, it is possible to play on the module of the teeth, but in a limited manner, there are therefore a limited number of configurations and which are remote from the desired ratio and / or from an optimized mass. The speed of the selected power turbine is a consequence of the combination of the reduction ratio and the speed of the propellers and may not be compatible with the objective of lifetime or result in a turbine under optimized because of high mass. Conversely, compliance with this specification may lead to a non-optimized aero acoustic situation in the absence of an additional degree of freedom when defining the characteristics of the engine. The reduction of the propeller hub ratio - ratio between the diameter of the hub and that of the propellers - is favorable in terms of the performance of the engine or the mass thereof.

With iso-diameter, it allows a reduction of the aerodynamic load of the propellers and consequently an increase of the yield.

3035156 3 A iso aerodynamic load, it allows a reduction of the diameter of the propellers and consequently a reduction of the mass.

The air intake can be arranged in different ways: The engine air intake can be arranged upstream of the propellers with a central opening and an annular channel between the hub and a crown supporting the propeller blades, as this is illustrated in the patent application FR 10 2951502 in the name of the applicant. However, the presence of rotating arms in the air inlet channel causes a pressure drop which has a negative impact on the performance of the gas generator. The air inlet can be arranged between the two propellers 15 in the form of an annular channel. The patent applications FR 2998867 or FR 3001264 in the name of the applicant represent an example, see Figure 1. However insofar as the radius of the annular channel is high since the periphery of the engine, the available height of the opening 20 is weak. This results in a significant boundary layer thickness which is unfavorable in terms of yield. In addition, the intake air flow is subject to distortion phenomena in case of skidding or strong impact of the aircraft. Finally, this arrangement results in an increase in the hub ratio of the downstream propeller which is unfavorable in terms of mass and performance. The air inlet can be arranged behind the propellers and have an annular or bilobed shape. With an annular shape, we find the same aerodynamic impact as 30 previously. With a bilobed shape, it enjoys a higher opening height and therefore more favorable in terms of efficiency but there is a distortion of the higher flow in case of skidding which has an impact on the operability of the compressor of the gas generator.

3035156 4 The air intake can be arranged behind the propellers and have a lobed mono shape. This makes it possible to increase the height of the vein and to avoid the aerodynamic problems encountered in the other solutions, but this arrangement imposes a certain aerodynamic profile which makes the integration of a speed reducer dependent on a significant elongation of the engine. . The air inlet makes it possible to circumvent the differential transmission but its size depends on the radius of the ring of the differential transmission. This elongation comes at the expense of mass while inducing carcass distortion and decreased performance. In an upstream propeller doublet propeller architecture, it is also important to pay attention to the arrangement of servitudes. Each propeller, being of variable pitch, comprises a mechanism for varying the pitch of the blades with a cylinder for rotating the pivots. It must be possible to supply fluidic and electrical servitudes to the various upstream cylinders. These easements must be passed from a fixed reference point, linked to the structural casing, to a rotating reference mark at the level of the propellers. In particular, the fluid supply must pass through an oil transfer system that generates a lot of leaks. In addition, passing electrical servitudes from a fixed reference 25 to a rotating mark requires to set up a rotating transformer. Finally, it is also desirable not to have to cross air vein because of the induced pressure drops.

The present applicant has set as its first objective the production of an upstream propeller doublet engine, the transmission of power between the power turbine and the propeller doublet allows an easy adaptation between a speed reduction mechanism and the turbine that drives it.

A second objective is a motor whose air intake is both insensitive to variations in the incidence of the aircraft and induces a pressure drop as low as possible.

Another objective is the realization of a motor whose thruster arrangement allows a low hub ratio. Another objective relates to the optimal arrangement of the servitudes feeding the pitch change mechanisms of the propeller blades. Presentation of the invention.

These objectives can be achieved in accordance with the invention with an engine having a pair of counter-rotating propellers, a gas generator supplying a power turbine, the pair of propellers being rotated by the turbine shaft of the turbine. power through a speed reducer, the axis of rotation of the pair of propellers being non-coaxial with that of the power turbine. This engine is characterized in that the speed reducer comprises a differential gear train and a first stage comprising a simple gear train between the turbine shaft and the differential gear train. The differential gear train includes an input on the power turbine side and two outputs, each driving a propeller rotor.

According to another characteristic, the first stage comprises a wheel connected to the planetary gear of the gear unit.

By this characteristic, the invention makes it possible to have an additional degree of freedom when it comes to determining the speeds and torques in relation to the power turbine. Indeed in a differential transmission, the ratio of the couples between the two outputs is related to the input / output reduction ratio. With this additional stage, it is possible to optimize the characteristics of the power turbine. A fast power turbine has a lower mass because its average radius can be reduced and its integration is also facilitated. This additional stage also allows more freedom to reduce the mass of the differential. For this purpose several solutions can be explored and combined: increase the reduction ratio to reduce the diameter of the central sun gear, reduce the diameter of the satellites or optimize the overall reduction ratio to reduce the total mass of the wheels.

The ratio between the downstream propeller and the upstream propeller torques is set by aerodynamic and acoustic parameters so as to have an optimum propulsive efficiency of the propeller doublet. The overall reduction ratio is different from the reduction ratio of the differential transmission. It is desired to have an overall reduction ratio between 8 and 15 and a reduction ratio on the differential portion between 6 and 11. The ratio of the overall transmission is between 0.5 and 2 of the ratio of reduction of the differential transmission. A gear ratio is preferably chosen for the single gear train so as to have the gear ratios correlated to the aforementioned torque ratio. In particular we seek to have a differential with a higher reduction ratio to limit its weight.

At the same time, the simple gear train produces a shift between the axes of the thruster and the generator. This offset makes it possible to ensure an optimization of the modularity between the thruster and the gas generator as well as a low hub ratio at the helices, made possible by the absence of internal vein in the thruster. It also makes it possible to drive equipment directly via the gearbox, for example a charge compressor.

According to one embodiment, the differential gear comprises a planetary gear, a planet carrier and a ring gear, the carrier being connected to the upstream propeller and the crown to the downstream propeller of the propeller pair.

According to an alternative embodiment, the differential gear comprises a planet gear a planet carrier and a ring gear, the planet carrier being connected to the downstream propeller and the ring gear to the upstream propeller.

More particularly, in accordance with a preferred integrated structure, the motor comprises a fixed structure with a sleeve, a first shaft member being supported by bearings within the sleeve, said shaft member connecting the crown to a helix of the doublet. According to another feature, the motor comprises a second shaft element supported by bearings within the first shaft element, the second shaft element connecting the planet carrier to the other shaft of the shaft element. propeller. According to another feature, the motor comprises a third shaft member supported by bearings at the fixed structure, said shaft member connecting the first speed reduction stage to the planetary gear. Advantageously, the motor comprises a sleeve containing servitudes, housed inside the shaft elements. More particularly, this sheath is fixed. The invention thus allows the routing of the servitudes in the static reference, and the implementation of a static cylinder. Such an arrangement is not possible in the case of an online architecture. In addition, the incorporation of a sheath into the thruster, offset from the gas generator allows easier access.

According to another feature, the air intake of the engine comprises an air inlet sleeve, lobe-shaped adjacent to the speed reducer. By the combination of an offset of the shafts and an air intake sleeve 20 adjacent to the speed reducer: - Improved access conditions for the maintenance of the main modules that are the gas generator and the thruster . The offset lobed air inlet improves the aerodynamic performance of the air intake and easily integrates a particle trap. - The integration of the external configuration is easier; the engine has a larger volume to house the equipment (AGB, pump ....), which is also arranged in a cold part. - The installation of the engine, turboprop type, is possible, with the advantage over an in-line engine, to have an increased ground clearance, same diameter propeller. 3035156 9 - Large diameter rotary housings can be omitted from other engine architectures because there is no air flow through the hub. This results in a significant mass reduction. 5 - The length of the motor is reduced relative to the in-line engine - since at least 80% of the axial size of the transmission is taken from the space occupied by the inlet duct - while respecting the constraint of maintaining a small deviation of air between the inlet sleeve and the compressor inlet. This results in a gain in weight. Brief description of the figures.

The invention will be better understood, and other objects, details, features, and advantages thereof will become more apparent upon reading the following detailed explanatory description of an embodiment of the given invention. by way of purely illustrative and non-limiting example, with reference to the accompanying schematic drawings. In these drawings: Figure 1 shows schematically in axial section an example of the engine according to the invention; Figure 2 shows in more detail the structural elements of the embodiment of an engine according to the invention; Figure 3 shows the details of Figure 2 pertaining to the thruster; Figure 4 shows an alternative embodiment of the invention; Figure 5 shows, in perspective, an example of a gearbox with double toothed wheels; Figure 6 shows another example of a reducer.

Figure 7 shows the engine, in perspective, with the arrangement of the air inlet sleeve with respect to the offset axes.

Description of Embodiments of the Invention With reference to FIG. 1, the engine 1 is shown mounted on an aircraft A in the rear part of the fuselage. It is attached to it in two suspension planes, a plane P1 10 upstream and a plane P2 downstream. It comprises from upstream to downstream, a thruster 3 formed of two counter-rotating propellers, 31 and 32, rotating about an axis XX, said axis of the thruster. Downstream, a gas generator 5 is formed of a gas turbine engine with a compression assembly, a combustion chamber and a set of turbines. The gases of the gas generator 5 are ejected into the atmosphere by an exhaust nozzle 12 at the rear of the engine. The shafts of the generator 5 are coaxial and rotatably mounted about an axis YY, said axis of the gas generator.

The axes XX and YY are offset with respect to each other. With respect to the position on the aircraft, in FIG. 1, the axis XX is positioned above the axis YY; it makes it possible to increase the distance from the ground to the thruster and to have an engine positioned lower on the aircraft or positioned on an aircraft requiring a large ground clearance. The offset also allows the engine to be mounted on the aircraft so that the gas generator is brought closer to the fuselage to limit the overhang of the engine while moving the propellers away. In this case the axes will be at the same height but offset horizontally or offset in height and horizontally. Figure 7 shows schematically the motor of the invention with its two axes XX and YY and the air inlet sleeve whose axis is coplanar with the two first 3035156. The arrow F with its double direction illustrates how one can vary the relative position of the axes relative to each other on the aircraft by rotating them relative to each other.

Part of the power supplied by the gas generator 5 is transmitted by a shaft 53a to the propellant. The shaft 53a extends upstream and drives the rotors 31 and 32 of the thruster through a speed reducer comprising a differential gear 7 and a first stage 6 gear simple. The gear train is said to be simple because the axes of rotation of the gear wheels are fixed. The first stage 6 with a simple gear train comprises, according to this embodiment, a toothed wheel 61, integral with the shaft 53A, meshing with a toothed wheel 63, rotatably mounted about the axis XX of the thruster. The offset between the axes XX and YY corresponds to the difference between the axes of the two wheels 61 and 63. According to the respective radii of the two wheels, this first stage 6 causes a reduction or an increase in speed of rotation between the wheels of the two wheels. entry and exit. The gear train is said to be simple because the axes are fixed unlike the differential.

The wheel 63 drives the wheels of the differential gearbox 7. This differential comprises a central sun gear 71, a ring 73 and in between, the satellites 72 mounted on the satellite gate 72P. The three elements 71, 73 and 72P of the differential and the axis XX are coaxial.

The shafts 31A and 32A of the propeller rotors are coaxial with the axis XX and are respectively integral with the planet carrier 72P and the ring gear 73 of the differential gearbox.

The output wheel 63 of the first reduction stage causes, by its shaft, the shaft of the sun wheel 71.

The pitch of the blades of each of the propellers is controlled by a cylinder schematized at 31V and 32V respectively. For example, the pitch is modified by cranking the blades around their axis. Patent FR 3001264 filed by the applicant describes an embodiment of a pitch change control. The gas generator 5 is housed in a nacelle 10 which comprises an air inlet sleeve 11 for supplying air to the gas generator. This air inlet sleeve is adjacent to the speed reducers 6 and 7 with an inlet plane 11a perpendicular to the axis XX and is arranged to direct the air in a direction parallel to XX and then to divert it to the inlet of the generator 5. The curvature of the air intake duct allows the incorporation of a particle trap 13 and foreign objects likely to damage the engine. It should be noted that the offset in height of the axes makes it possible to integrate the air duct 11 with an opening height 25 that is more favorable in terms of pressure drop with respect to the annular openings, since the boundary layer in the duct The air inlet occupies a relatively small part of it compared with fresh air. The width of the sleeve 11 extends over a portion of a circle, for example 90 °.

Furthermore, advantageously, the upstream lip 11b of the air inlet sleeve, on the nacelle side, is detached from the latter so as to avoid or at least reduce the ingestion of the air of the air. boundary layer formed by the flow along the revolving platform. Also advantageously, a device for recovering lubricating oils from the gearbox gears is housed in the lower part of the gearbox near the air inlet sleeve. This recovery oil is at a temperature sufficient to constitute a means of defrosting the air shaft.

The operation of this engine is as follows. The air is guided by the sleeve 11 to the gas generator 5 which provides an appropriate energy to drive the power turbine 53. The gases from the turbine are ejected through the nozzle 12. The architecture of a such engine allows a focus during its development in several stages. This development comprises: An aero-acoustic optimization step where the absolute value of the ratio of the torque of the upstream propeller between 0.8 and 1.5 or 2 and the speed of the propellers is fixed. The torque ratio sets the differential reduction ratio. A step of optimizing the turbine where an ideal turbine speed is set according to the parameters of the turbomachine that are the power the shape of the vein and the maximum speed. We deduce the overall reduction ratio between the turbine and the propellers. The reduction ratio of the reducer is thus fixed.

A step of optimizing the mass of the entire gear and the size of the offset between the axes XX and YY where the torque ratio is varied by +/- 10% to determine a lower mass point .

Referring to Figures 2 and 3, there is shown in more detail an embodiment of the motor. The combustion chamber 54 is disposed between the compressor 52C, high pressure compressor, and the turbine 52T, high pressure turbine. Downstream of the turbine 51T, a low-pressure turbine, a power turbine 53 is mounted on the shaft 53a coaxial with the shafts 51a and 52a.

The first stage 6 with a simple gear train comprises, according to this embodiment, a toothed wheel 61 integral with the shaft 53a meshing with a toothed wheel 63 rotatably mounted about the axis XX of the thruster. The offset between the axes XX and YY corresponds to the difference between the axes of the two wheels 61 and 63. According to the respective radii of the two wheels, this first stage 6 causes a reduction or an increase in speed of rotation between the wheels of the two wheels. entry and exit. The gear train is said to be simple because the axes are fixed unlike the differential wheel 63 drives the wheels of the differential gear 7. This differential comprises a central sun gear 71, a ring 73 and in between, the satellites 72 mounted on the 72P planet carrier. The three elements 71, 73 and 72P of the differential and the axis XX are coaxial. The shafts 31A and 32A of the propeller rotors are coaxial with the axis XX and are integral respectively with the planet carrier 72P and the ring gear 73 of the differential gearbox. The output wheel 63 of the first reduction stage drives the shaft of the sun gear 71 through its shaft.

The turbine rotates the wheels of the first reduction stage 6. The rotational speed of the output wheel relative to that of the shaft 53A is determined by the ratio of reduction / or increase defined with the 5 engine characteristics. The output wheel of the first stage drives the sun gear which rotates the planet carrier and the planet wheels that it supports. These planet wheels drive the crown in reverse rotation relative to that of the sun gear. During flight and on the ground, the pitch of the blades are adjusted by jacks. The pitch of the blades of each of the propellers is controlled by a cylinder schematized in 31V and 32V respectively. For example, pitch modification is provided by cranking the blades about their axis. The patent FR 3001 264 filed by the applicant describes an embodiment of a pitch change control.

The diagram of FIG. 2 makes it possible to understand the operation of the engine, FIG. 3 shows the same motor elements relating to the propulsion part and shows how these are integrated into the structure.

The fixed structure 20 comprises a set of housing elements forming bearing supports. Thus, the casing comprises a sleeve 21 extending upstream. This sleeve 21 is coaxial with the shafts 32A and 31A of the two propellers. It supports by means of bearings 22 the shaft 32A of the downstream propeller connected to the ring 73 of the differential gear. This shaft 32A is secured at its other end of the hub of the propeller 32. It is noted that the sleeve 21 supports the actuator 32V for controlling the pitch of the blades of the downstream propeller 32. To ensure the transmission of a movement 3035156 16 of translation of the control member of the fixed jack 32V, a ring 32v1 is mounted with bearings on the control member of the jack. This ring is connected to the pivot rods of the pivot 32p of the blades.

The shaft 31A connected to the upstream propeller 31 is supported by the shaft 32A via inter-shaft bearings 321. Downstream, the shaft 31A is attached to the planet carrier 72p.

The shaft 63A connecting the first stage gear 6 to the sun gear 71 is supported by a stationary housing member through bearings 24. A fixed sleeve 25 is housed within the shafts 63A and 31A. . It connects the actuator cylinder 31V pitch pitch of the upstream propeller to an area downstream of the gearboxes. The function of this sleeve is to serve as a guide to the fluidic and electrical servitudes for including the 31V cylinder. This jack is fixed and, like the jack 32V, it transmits the movement to the pivots 31P of the blades of the upstream propeller by means of a rotating ring. According to another embodiment, the upstream cylinder is rotatable about the axis XX. An appropriate seal is then provided between the jack and the sheath. FIG. 4 shows a variant embodiment in which the attachment of the shafts of the two propellers has been modified. The shaft 32A 'is arranged to be driven by the carrier 72P and in turn drive the downstream propeller. The shaft 31A 'is arranged to be driven by the ring gear 73 of the differential gearbox and to drive the upstream propeller 31.

FIG. 5 shows an embodiment of the first stage with a single gear train enabling transmission of a high power density by distributing the forces applied to the teeth over a larger area. . In this example, the shaft of the turbine 53A is secured to two coaxial gearwheels 61 'which mesh simultaneously on two coaxial toothed wheels 63'. These two wheels 63 'are integral with two coaxial wheels 71 forming the sun gear of the differential 7. In the same way, the satellites 72' are split axially and the ring 73 '. . This arrangement has the advantage of distributing the torque transmitted between the two split wheels, which limits the load on the teeth, without penalizing the gear in the longitudinal direction. There is shown in Figure 6 an alternative embodiment of the gearbox for the same purpose. In this figure the differential ring has not been drawn. There is the toothed wheel 61 "secured to the shaft 53 A. Here it drives two wheels 62" in parallel. These two wheels are placed in the same plane transverse to the shaft 53A and engage with the wheel 63. This wheel is coaxial with the planet wheel of the differential which, as in the previous example, has been split. in the same way, the two wheels of the sun wheels drive the planet wheels itself axially split like the unscored crown This solution makes it possible to reduce the axial size of the gearbox without affecting the capacity to transmit high torques. more particularly its cantilevered part is reduced accordingly.

A mechanism for equalizing the torque between the two wheels is optionally added to this gear train to prevent premature wear on one of the stress paths.

Claims (12)

REVENDICATIONS1. Motor comprising a propellant with a pair of counter-rotating propellers (31, 32), a gas generator (5) supplying a power turbine (53), the pair of propellers being rotated by the shaft (53A) of the power turbine through a speed reducer, the axis of rotation (XX) of the pair of helices being non-coaxial with respect to that (YY) of the power turbine, characterized in that the speed reducer comprises a differential gear train (7), with a first stage (6) comprising a simple gear train between the turbine shaft (53A) and the differential gear (7). 2. Motor according to claim 1, the first stage (6) comprising a wheel (63) connected to the planetary gear (71). 3. Motor according to one of the preceding claims, wherein at least one of the differential gear and the single gear train comprises split gear wheels, in particular axially. 4. Motor according to claim 3, the simple gear train having two wheels (62 ") in parallel meshing on the wheel connected to the planetary gear. 5. Motor according to one of claims 1 to 4, whose differential gear comprises a planetary gear (71), a planet carrier (72P) and a ring gear (73), the planet carrier being connected to the upstream propeller. (31) and the crown (73) to the downstream propeller (32) of the doublet. 3035156 20 6. Motor according to one of claims 1 to 4, the differential gear (7) comprises a planet gear (71), a planet carrier (72P) and a ring gear (73), the satellite carrier being connected to the 5 downstream propeller and the crown to the upstream propeller. 7. Motor according to one of claims 1 to 6, wherein the air inlet comprises a lobe-shaped air inlet sleeve (11) adjacent to the speed reducer. 10 8. Motor according to one of the preceding claims comprising a fixed structure (20) with a sleeve (21), a first shaft element (32A) being supported via bearings (22) inside the 15 sleeve, said shaft member connecting the crown to a helix of the doublet. 9. Motor according to the preceding claim comprising a second shaft element (31A) supported by bearings 20 (321) inside the first shaft element, the second shaft element connecting the planet carrier the other helix of the doublet of propellers. The engine of one of claims 8 and 9 including a third shaft member (63A) supported by bearings (24) to the fixed structure, said shaft member connecting the first speed reduction stage to the planetary gear. 30 11. Motor according to one of claims 8 to 10 comprising a sleeve (25) containing servitudes, housed inside the shaft elements. 3035156 21 12. Motor according to the preceding claim whose sleeve is fixed.