WO2019180755A1

WO2019180755A1 - Automatic pitch variator for turbo fan blades of aircraft engines with contactless control between stator and rotating hub

Info

Publication number: WO2019180755A1
Application number: PCT/IT2019/000022
Authority: WO
Inventors: Leonardo Valentini
Original assignee: Leonardo Valentini
Priority date: 2018-03-20
Filing date: 2019-03-18
Publication date: 2019-09-26
Also published as: IT201800003771A1

Abstract

Automatic and continuous variation of the blade pitch without mechanical contact for applications in aeronautical turbofans. The actuation of the adjustable blade-holder supports with seat in the rotating hub of the fan takes place through electric pulses applied on special coils integral with the stator. The generated magnetic force imparts the rotating torque to multiple endless screws conjugated to a common ring gear which rotates an annular disk to adjust the step angle of the blades.

Description

DESCRIPTION of the invention having for TITLE:

"Automatic pitch variator for turbo fan blades of aircraft engines with contactless control between stator and rotating hub".

The turbofans aeronautical engines for civil use are designed to have the maximum efficiency only for the narrow range of speeds and flight quotas for long-haul sections, when they are operating outside this range (take-off, low altitude, variation in flight altitude on free-run areas, etc. ) the propulsive efficiency drops dramatically because the fixed-mount turbofans are rotated by a turbine stage forced to work outside the optimal flow and power conditions.

To overcome these criticalities, the innovative technological solution object of the present invention is aimed at solving the problem of optimizing fuel consumption with changes in altitude and flight speed.

The constructive solution proposed in the present invention allows variable pitch turbofans to be made which can better adapt to the optimal revolutions and to the transients of the driving turbine stage to which they are connected, obtaining a greater propulsive efficiency even outside the usual operating range.

The conception of this peculiar pitch variation system of turbofan blades has been oriented towards the extreme the reliability and durability of the device to the most extreme operating conditions.

Compared to other solutions of pitch variation PCM (Pitch Change

Mechanism), this is characterized as a system without physical contact having and no mechanical parts between the control kinematics integral with the stator and the blades pivoted to the turbofan body. The absence of mechanical linkages or rolling or crawling kinematics between the rotating and fixed part of the actuator makes the pitch orientation exceptionally reliable as it avoids lubrication, the onset of wear, potentially catastrophic wear and tear.

The device for varying the pitch of the present invention is particularly suitable for the use of carboresin blades for making turbofans, since the carbon fiber blades are much lighter than the corresponding blades in aluminum alloy and consequently the resulting stresses are reduced proportionally from the action of the centrifugal force on the support structures.

The heart of the system is represented by a single crown with external teeth where the worm screws mesh with the central body of the turbofan.

The ring gear, moved by the endless screws, is keyed on a coaxial disk on the periphery of which the seats are made to house the spherical-terminal pins of the adjustable blade-holder supports.

With this configuration, the rotation of the worm screws turns the door crown into rotation, making the pitch change.

To perform the rotation of the worm screws, without mechanical connection, permanent magnets have been placed integral with these and by means of stator coils it is possible to generate a radially variable magnetic field which puts the screws in clockwise or counterclockwise rotation depending on how they are fed the reels.

Figure 1 illustrates the turbofan in the two extreme positions of the blades, at a minimum with blades arranged with the lowest pitch angle, at most arranged with the greatest angle of keying allowed for the system of continuous pitch variation.

Figure 2 shows the overall cross section of the turbofan, in which the hub is shown in position 3, made of a special superalloy of very high toughness and rigidity, which houses, in the front polygonal (number of sides equal to the number of blades), the position pins 10, connected to the prismatic support base of the position blades 15.

The blades support base of position 15 rotates by means of the position pin 10 of an angle of amplitude a variable between the minimum value and the maximum value corresponding to the greatest angle of keying.

To make the system very smooth on the position hub 3, on the position pin 10, an axial roller bearing of position 12 is interposed above and at the bottom a very strong axial bearing of position 11, on which are concentred the

considerable centrifugal forces deriving from the turbofan rotation.

The adjustment of the geometric tolerances between the parts and the stable maintenance of the mutual position is ensured by the self-locking position ring 8.

On the extreme part of the support base of position 15 the spherical terminal of position 16 is locked by threading and is housed in the position seats 18 of the annular position disc 17.

In order to minimize the friction between the position base 15 and the support plane on the position hub 3, a special anti-wear support plate of position 13 is interposed between the surfaces.

In the rear area of the position hub 3 the position supports 4 are fixed, on which the worm screws of position 5 can rotate, mating with the toothed crown of position 6 integral with the position ring 14, constrained by means of the position screws 26 and the position spacers 25 to the annular position disk 17.

The specific worm screws of position 5 are set in rotation by the action of the magnetic field generated by the position coils 22 rigidly fixed on the static annular support of position 24.

The position hub 3 is set in rapid rotation by the shaft of the position turbine 30 through the position seat 27 constrained on the hub itself. The internal circular seat on the annular position disc 17 and the circular one of the position ring 14, are free to perform an arc of angular displacement on the position hub 3, providing a kinematic mechanism in which for a determined rotation of the worm screws of position 5 corresponds to an appropriate angle of orientation a of the support of the position blades 15.

Figure 3 illustrates in more detail how, for a rotation arc g of the position disc 17, the inclination of the position blades 1 of a determined pitch angle a is obtained.

Figure 4 shows in more detail the position of the shovel-holding support 15, made of a special titanium superalloy (reduced weight for containing

centrifugal forces) on which the carbon fiber blades are fixed in the tailed recess of swallow.

In the recess formed in the position support 15 the locking screws of the respective carboresin blades are inserted, which being very resistant and light limits the stress values on the respective seats of the hub.

Between the axis of the rotation pin and that of the spherical terminal, which transmits the displacement force, there is an adequate distance of the arm to allow the containment of the value of the driving force of the kinematic mechanism.

The lower part of the position support base 15 has a polygonal profile (side C) in which the position sliding shoe 13 is housed, made of a special material with a very low friction coefficient and integral in the orientation rotation with the base same.

Figure 5 illustrates the conformation of the annular position disk 17 in the periphery of which the seats for the spherical terminal pins of position 16 are formed, all in contact in the position area 18, equidistant from the center of the hub with circular radius b.

Figure 6 shows the positioning of the position supports 4 (in number from 3 to 6 equidistant on the circumference), on which the special position screws 5 free to rotate around the position pin 7 are mounted.

The worm screws of position 5 all mesh on the same mating crown gear 6, causing a distributed distribution of the peripheral stress, so that with modest efforts of each screw a considerable torque is obtained on the crown of position 6, with the very low ratio of the kinematic transmission, the position of irreversibility of the motion between the screws of position 5 and the crown of position 6 is ensured, thus ensuring the maintenance of the angle g to which corresponds the instantaneous value of the pitch of the blades with angle a.

Figure 7 illustrates in more detail the conformation of the hub of the turbofan of position 3, in which the spacer pins of position 25 (Figure 2) can perform an arc of rotation g comprised between two extreme values, maximum and minimum, exceeded these values of the angular excursion there will be a limit switch contact of the position pin 25 on the seat of the hub of position 3.

Operating in these conditions, an absolute safety of positioning of the end of stroke is obtained for the pitch angles of the blades, also in case of faults or anomalies of the control system there will be a stop in a position with a consequent decrease in performance of propulsion but with the turbofan that will continue to operate safely.

Figure 8 illustrates in detail the position disk 21 of Figure 2 which is inserted and fixed by means of numerous screws to the end of the position hub 3, in the polygonal side which houses the pivots 10 for rotating the blades.

This position element 21 is of enormous importance from the point of view of the structural stability of the position hub 3, since this part of the hub being lightened due to the presence of the holes of the position pins 10 (of

considerable diameter) would come to conform as a cantilever shelf, penalized by the effect of concentration of the flow of effort and would constitute a critical area.

The presence of the position disc 21 made of very tough maraging steel which is housed with interference in the peripheral seat of the position hub 3, fixed by the numerous screws, constitutes an armoring ring passing from a

cantilever bracket to a beam on two supports, significantly contributing to the structural stability of the hub and considerably increasing the resistance to the fatigue cycles of the position hub 3 which is a key element of the object of the present invention.

Figure 9 illustrates the conformation of the specific worm screws of position 5, at whose two ends symmetrical cavities are obtained (in the number of 4 - 6 - 8) on which the high-intensity permanent magnets of position field 9 are be positioned, with polarity alternating between a magnet and the next (North - South - North - South etc ...).

The position screw 5 can rotate on the central position pin 7, in the peripheral zone of the screw, in correspondence with the permanent position magnets 9, there are the position coils 22, which are supplied through the specific electric circuit of position 23 ( figure 6 and figure 9), alternately and in syncshronism to allow the rotary motion of the screw in a clockwise or anti-clockwise direction. The synchronized square-wave power supply of the position coils 22 generates the magnetic fields that attract and repel the respective adjacent position magnets 9, puting the screw in rotation.

The position coils 22 are integral with the fixed part (position 24 figure 2) of the structure, while the position screws 5 housed in the position supports 4 (figure 2 and figure 6) are integral with the rotary position hub 3.

From this configuration a control device is created without physical contact between the fixed part (statoric) and the mobile part (hub - rotor).

Figure 10 illustrates the front position cover disc 31, which houses on the position hub 3 on the front outer part in contact with the inlet air flow, where the position ogive 2 is housed in centering of figure 1.

Claims

1) Device for automatic and continuous variation of the pitch of the blades (1) of turbofans of aeronautical engines comprising supports (15) of blades, adapted to be hinged to the hub of the turbofan (3), provided with spherical terminals (16) housed at the periphery of an annular transmission disk (17) coupled to an external toothing crown (6), the disc and the toothed crown are arranged coaxial to the hub, comprising numerous endless screws (5), meshed with the toothing of the crown, bearing numerous magnets (9) integral and coaxial adapted to be rotated by magnetic fields, transverse to the axis of rotation of the hub, and generated by specific coils (22) integral with the motor stator and powered by a special electric circuit (23).

2) Variation device according to claim 1, characterized in that for the generation of the magnetic field there are numerous coils (22), generally from 2 to 500, integral with the stator of the turbofan (24) arranged in an annular way on a circumference with a medium radius coinciding with the distance between the axes of the screws from the transverse axis of the hub.

3) Variation device according to claim 1 and 2, characterized in that the numerous supports (15), generally from 2 to 100, of the worm screws (5) are arranged equidistant from each other and so that they mesh on the toothing outside of the crown (6).

4) Variation device according to one of the preceding claims, characterized in that the numerous permanent magnets (9), generally from 2 to 200, are fixed at the ends of the respective endless screws (5) with alternating polarity to form two rotor cylinders. 5) Variation device according to one of the preceding claims, characterized in that the toothed crown (6), on which all the worm screws (5) engage, is coaxial and neutral to the rotation axis of the turbofan hub (3).

6) Variation device according to one of the preceding claims, characterized in that the annular transmission disk (17), in whose seats (18) house the spherical terminals (16), is coaxial and integral with the toothed crown (6) and also it is idle on the hub of the turbofan (3) through the ring (14).

7) Variation device according to one of the preceding claims, characterized in that the bases of the supports (15) of the blades (1) are provided with a pin (10) perpendicular to the hub axis and have an end with spherical terminals (16). ) housed on the annular transmission disk (17).

8) Variation device according to one of the preceding claims, characterized in that the generation of the magnetic field is carried out by the action of the electric circuit (23) on the stator coils (22) through the application of square wave pulses of electric current. , synchronized between the different coils so as to induce the clockwise or anticlockwise rotation of the magnets (9) inserted in the end of the worm screws (5).

9) Variation device according to one of the preceding claims, characterized in that the perimetral conformation of the hub (3) which houses the oscillating pins (10) of the supports of the blades (15) is polygonal with a number of sides equal to the number of blades ( 1) of the turbofan.

10) Variation device according to one of the preceding claims, characterized in that in the peripheral polygonal planes of the hub (3) two bearings (11) and (12) are housed orthogonal to the axis of the hub itself.