Balancing screw, device and method for a rotating part of a turbine engine

Abstract

A balancing device for a rotating part of a turbomachine, includes a ferrule pierced with a plurality of ports, a balancing screw passing through each port, each balancing screw including a body and a head, the head of each balancing screw being pierced with a recess, the balancing screws being of at least one first type, the recess of the screws of the first type being formed by a driving recess from which an additional recess extends.

Claims

1. A balancing device for a rotating part of a turbomachine, comprising a ferrule pierced with a plurality of ports, and a balancing screw passing through each port of the plurality of ports, each balancing screw including a body and a head, the head being pierced with a recess, wherein the balancing screws are of a first type and a second type, wherein the recess of the balancing screw of the first type is formed by a driving recess and by an additional recess, the driving recess having a bottom, the bottom of the driving recess being pierced with the additional recess, and wherein the recess of the balancing screw of the second type is formed only by a second driving recess.

2. The balancing device according to claim 1, wherein: the balancing screws of the first type are made of a material having a first density m1, the balancing screws of the second type are made of a material having a second density m2, m2 being strictly higher than m1.

3. The balancing device according to claim 2, wherein: the balancing screws of the first type are made of titanium; the balancing screws of the second type are made of steel.

4. The balancing device according to claim 1, wherein: the screws of the first type have a length l1; the screws of the second type have a length l2, l2>l1.

5. The balancing device according to claim 1, wherein the balancing screw heads are cylindrical.

6. The balancing device according to claim 1, wherein: the head of each balancing screw of the first type has a mass at least equal to 60% of a total mass of said balancing screw; and/or the head of each balancing screw of the second type has a mass at least equal to 40% of a total mass of said balancing screw.

7. The balancing device according to claim 1, further comprising additional balancing screws, each additional balancing screw having a mass between the mass of one of the screws of the first type and the mass of one of the screws of the second type.

8. A method for balancing a rotating part of a turbomachine provided with the balancing device according to claim 1, the method comprising adjusting a depth of the recess of the balancing screw of the first type and/or the recess of the balancing screw of the second type so as to balance the rotating part.

9. The balancing method according to claim 8, further comprising adjusting one or more of the following parameters to balance the rotating part: external dimensions of each of the heads; a shape of the screw heads; a material of the balancing screws.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further characteristics and advantages of the invention will appear upon reading the detailed description that follows, in reference to the appended figures, which illustrate:

(2) FIG. 1, a cross-section view of an inlet cowl of a turbomachine of prior art;

(3) FIG. 2, a perspective view of an inlet cowl of a turbomachine according to one embodiment of the invention;

(4) FIG. 3, a cross-section view of the inlet cowl of FIG. 2;

(5) FIG. 4, an enlarged cross-section view of a part of the inlet cowl of FIG. 2;

(6) FIG. 5, another cross-section view of a part of the inlet cowl of FIG. 2;

(7) FIG. 6, another cross-section view of another part of the inlet cowl of FIG. 2;

(8) FIG. 7, a cross-section view of one of the screws of the inlet cowl of FIG. 2;

(9) FIG. 8, a cross-section view of another screw of the inlet cowl of FIG. 2.

(10) For more clarity, identical or similar elements are marked with identical reference signs throughout the figures.

DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT

(11) FIGS. 2 and 4 to 6 represent an inlet cowl 20 of a turbomachine including a balancing device according to one embodiment of the invention.

(12) This inlet cowl 20 includes a cone 21 provided with a balancing device 22. The balancing device 22 includes a ferrule 23. The ferrule 23 has in this case a conical shape. In this embodiment, the ferrule 23 is formed by a back part of the cone 21. However, in the embodiment of FIG. 3, the ferrule 23 is formed by an additional part 24 which has a rotational symmetry and which is connected to the cone 21.

(13) The ferrule 23 is pierced with ports 25 which are radially distributed throughout the perimeter of the ferrule 23. In this embodiment, the ferrule 23 is pierced with twenty ports 25. However, the number of ports depends in particular on the diameter of the ferrule 23 and the desired balancing accuracy.

(14) The balancing device also includes nuts 26, each nut 26 being crimped in one of the ports 25. The crimped nuts 26 are able to receive so-called balancing screws 27, 27 so as to decrease or even remove the unbalance of the turbomachine.

(15) For this, balancing screws 27 of a first type are first inserted in each of the ports 25 and screwed in each of the nuts.

(16) The turbomachine is then rotated so as to detect the presence of a possible unbalance.

(17) If an unbalance is detected, some screws of the first type 27 are then replaced with balancing screws of a second type 27 so as to decrease the unbalance. The balancing screws of the first type 27 and of the second type 27 are radially distributed about the ferrule so as to decrease the unbalance of the turbomachine. In this exemplary embodiment, five screws of the first type 27 have been replaced with five screws of the second type 27, however, the radial distribution and the respective number of the screws of the first type and of the second type depend on the unbalance.

(18) The balancing screws of the second type 27 have a mass higher than that of the screws of the first type 27.

(19) A screw of the first type 27 is more precisely represented in FIG. 7.

(20) The balancing screw of the first type 27 extends along a reference axis 31. The balancing screw of the first type 27 is preferably made of titanium. The balancing screw of the first type 27 includes a head 29 and a body 30. The body 30 of the balancing screw of the first type 27 includes on its external surface a thread 35 enabling the balancing screw of the first type 27 to be screwed in the nut 26. The body 30 of the screw of the first type 27 has a length l1 sufficient to be able to be wholly screwed in the nut 26. However, the length l1 is preferably chosen such that the body 30 does not project too much from the nut 26 such that the turbomachine is not made too heavy. The head 29 of the screw of the first type is pierced with a recess 32. The recess 32 is formed by a driving recess 33 and by an additional recess 34 located in the axial extension of the driving recess 33. The driving recess 33 has a bottom 40 which is pierced with the additional recess 34. The driving recess 33 is able to receive a spanning tool enabling the screw to be screwed in the corresponding nut 26. For this, the driving recess 33 preferably has a hexagonal cross-section. The additional recess 34 has preferably a cylindrical shape so as to facilitate its machining. Besides, it preferably has transverse dimensions with respect to the reference axis 31 which are lower than those of the driving recess 33 such that a spanning tool inserted in the driving recess 33 abuts against the bottom 40, at the limit between the driving recess 33 and the additional recess 34. The depth p1 of the recess 32 is adjusted as a function of the desired mass for the screw and more precisely for the head of this screw. In the same way, the transverse dimensions of the additional recess can be adjusted as a function of the desired mass for the screw and more precisely for the head of the screw. The head 29 is preferably cylindrical to facilitate its manufacture.

(21) The dimensions of the screws of the first type 27 can be modified as a function of the mass they must have to balance the turbomachine. Thus, the length l1 of the body 30 of the screws of the first type 27 can first be modified. The mass of the head 29 can also be modified to achieve the desired balancing. For this, the dimensions of the head 29, and in particular its height l3 can in particular be modified. The depth p1 of the recess 32, as well as its shape can also be modified. It can also be contemplated to modify the shape of the head 29. The head 29 has a diameter d1.

(22) A screw of the second type 27 is more precisely represented in FIG. 8.

(23) The balancing screws of the second type 27 are substituted for some of the balancing screws of the first type 27 so as to decrease the unbalance of the turbomachine.

(24) The balancing screw of the second type 27 is preferably made of steel. The balancing screw of the second type 27 also extends along a reference axis 31 and it also has a head 29 and a body 30. The body 30 of the balancing screw of the second type 27 also includes on its external surface a thread 35 enabling the balancing screw of the second type 27 to be screwed in the nut 26. The body 30 preferably has a length l2 higher than the length l1 of the body 30 of the balancing screw of the first type 27. The head 29 is pierced with a recess 32. The recess 32 is formed in this exemplary embodiment by a spanning tool. In this embodiment, the recess 32 does not extend beyond the driving recess 33. Consequently, in this example, the depth p2 of the recess 32 corresponds to the depth of the driving recess 33. The depth p2 is thus lower than the depth p1, The recess 32 of the balancing screw of the second type 27 is thus minimum in this embodiment so as to maximize the mass of the heads and thus the screw balancing capability. Likewise, the head is preferably cylindrical so as to maximize its mass. The head 29 has a diameter d2.

(25) The dimensions of the screws of the second type 27 can be modified as a function of the mass they must have to balance the turbomachine. Thus, the length l2 of the body 30 of the screws of the second type 27 can be first modified. However, this length l2 is restricted by the space inside the ferrule. Consequently, it is advantageous to modify the mass of the head 29 to obtain the desired balancing. For this, the dimensions of the head 29, and in particular its height 14 can in particular be modified. The depth p2 of the recess, as well as its shape can also be modified. It can also be contemplated to modify the shape of the head 29.

(26) Besides, in this exemplary embodiment, all the balancing screws of the first type 27 were identical to each other, as well as all the balancing screws of the second type 27 were identical to each other. However, it could also be contemplated to use balancing screws of the first type 27 being different from each other and/or balancing screws of the second type 27 being different from each other.

(27) Besides, if the use of two types of screw is not sufficient to balance the unbalance of the turbomachine, and as a function of the desired balancing accuracy, intermediate screws, having a mass between the screws of the first type 27 and the screws of the second type 27 can be used.

(28) Naturally, the invention is not restricted to the embodiments described with reference to the figures and alternatives can be contemplated without departing from the scope of the invention. The radial distribution of the screws can thus be modified as a function of the unbalance to be balanced. Other materials can also be used to make the balancing screws.