Labyrinth disk with built-in stiffener for turbomachine rotor

A labyrinth disk includes a main stiffener placed in the middle of the rim immediately below labyrinth elements. Attachment elements are preferably in the form of a bayonet attachment system using teeth fixed on the labyrinth disk crown and teeth fixed on the rotor. Attachment by bolting may optionally be used. The disk may be utilized with turbojets, on the cooling circuit, on the upstream side of the high pressure turbine.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to turbomachines, such as turbojets with axial flow 
using labyrinth sealing devices to separate chambers containing air and/or 
oil. In particular, this is the case of the labyrinth fixed on the 
upstream side of the high pressure turbine. 
2. Discussion of the Background 
With reference to FIG. 1, the technological definition of turbomachines 
involving air flows at different pressures and temperatures, includes the 
use of sealing devices between chambers containing air and/or oil. This is 
the case of the labyrinth disk 2 that exists upstream from the high 
pressure turbine 1 and located on the passage of a part of the cold stream 
at the combustion chamber. In this position, this part is subjected to 
extremely high mechanical forces particularly due to the centrifugal 
force, since it is placed on the rotor. It is also in a difficult 
environment since the air stream surrounding it is fairly oxidizing and 
the temperature is very high. There are also very severe vibrational 
excitation phenomena that occur when passing through certain speeds, at 
which some parts of the rotary equipment become resonant. 
For these reasons, this part which is also called the high pressure turbine 
front labyrinth, is one of the most difficult parts to design. 
Furthermore, this operation sometimes results in a part with 
insufficiently long life, or a limitation as to its thermal qualities. 
FIG. 1 shows that this labyrinth disk 2 comprises several parts, including 
the labyrinth itself mostly facing the arrow indicated as 2. The lips of 
this labyrinth are supported by a rim 3 that projects upwards through a 
crown 4 which is supported on a downstream surface 5 of the rotor disk 8 
to which this part is fixed. On many recent turbojets, it is fixed by 
bolts 6 passing through the inner part of this part, which terminates at 
an inner stiffener 7. 
It should also be noted that this bolted attachment is not conducive to 
long life of this whole part. 
The purpose of the invention is to optimize the shape of this part, namely 
the labyrinth disk and its attachment device to the high pressure turbine 
rotor disk 8. 
SUMMARY OF THE INVENTION 
Consequently, the main object of the invention is a labyrinth disk for a 
turbomachine rotor comprising: 
a main rim, 
a labyrinth built into the rim, 
a crown in the outer extension of the rim, to be supported on an upstream 
surface of the rotor, and 
means of attachment of the labyrinth disk on the rotor. 
According to the invention, the labyrinth disk comprises a main radial 
stiffener built into the rim, just on the inside of the labyrinth. 
In one embodiment of the labyrinth disk according to the invention, the 
crown is an upper part of the rim relatively elongated in the radial 
direction, slightly complex, its downstream surface being in the same 
axial position as the downstream end of the main stiffener. 
In a first embodiment, the attachment means comprise attachment bolts 
placed in attachment holes formed in the inner part of the rim, inside and 
upstream from the stiffener. 
In another embodiment of the invention, the attachment means comprise 
attachment teeth designed to be placed behind the teeth fixed on the rotor 
in a bayonet locking system. In these cases, the crown may include 
stiffeners placed along the inner extension of the attachment teeth. 
Axial stops may also be used with the system, acting as stops facing the 
rotor stop surfaces placed on an upstream surface of the rotor. 
The crown of the labyrinth disk according to the invention may comprise 
stiffeners placed on the downstream surface of the rim. 
Part of the downstream surface of the crown may then act as an axial stop 
surface, particularly when it has ribs. 
Axial stops may also consist of the inner surface of attachment teeth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The labyrinth disk according to the invention is placed at approximately 
the same position as the labyrinth disk in FIG. 1. 
It generally comprises a rim 13 that forms the radial structure of this 
part. The inner part of this rim 13 terminates in an inner stiffener 9 
which is smaller than stiffener 7 in FIG. 1. 
Labyrinth 10 in the labyrinth disk consists of two parts each comprising 
several lips that are tangential with friction parts 16 fixed on a fixed 
part 17 added onto the inside of the stator at the outlet from the 
combustion chamber 20. 
In the embodiment shown in FIG. 1, the assembly is fixed onto the rotor, 
symbolized by the radial disk 8, by the inner part, i.e. the flange 
located above the inner bore. The attachment means shown are bolts 6 
penetrating inside holes in the inner bore. 
The rim 13 is extended by a central part comprising passages 11 and inner 
orifices 15 allowing the passage of the cooling air stream from the 
upstream part to the downstream part of the labyrinth disk. 
The outer part of the labyrinth disk 12 according to the invention, 
consists of the crown 14 extending from the rim 13 to be supported by an 
outer end 18 on an upstream surface 19 of the rotor. This crown 14 is 
somewhat less convex than that shown in FIG. 1. 
It is thus possible that the seal is made between the volume of the 
turbomachine placed inside the volume delimited by combustion chambers 20, 
and the inlet to the high pressure turbine 1 symbolized by a blade 21 in 
its first stage. However, passages 11 allow the cold stream to pass from 
the upstream surface of labyrinth disk 12 towards its downstream surface 
22. 
It can be seen that the inner stiffener 9 is smaller. However, a main 
stiffener 23 is provided in the middle of the labyrinth disk 12, i.e. on 
rim 13. It is shaped in the form of a torus that projects radially onto 
the downstream surface 22 of the labyrinth disk 12 immediately below the 
labyrinth lips 10 and below passages 11. Its downstream end is in the same 
longitudinal position as the downstream end of the downstream surface 22 
of crown 14. Lower orifices 15 are also provided so that a relatively 
small amount of the cold air stream passing from upstream to downstream 
through the labyrinth disk can pass below and around this main stiffener 
23, between it and the upstream surface 19 of the rotor disk 8. This type 
of cold air current can cool this main stiffener 23 and the downstream 
surface 22 of labyrinth disk 12. The two cool air flows passing through 
passages 11 and the inner orifices 15 join together behind labyrinth disk 
10 on the downstream surface 22 of the crown 14 to rise between the 
attachment teeth 24. They thus cool the entire rear part of this assembly 
formed by the labyrinth disk. They reach the rim of the turbine disk 8 and 
join the blade 21 cooling circuits and the attachment compartments of 
these blades. 
This main stiffener 23 provides most of the mechanical strength of the 
labyrinth disk 10. It contributes to reducing the size of the inner 
stiffener 9 and to reducing the general dimensions of the labyrinth disk 
10 and particularly crown 14. It should be noted that the shape of the 
crown may be somewhat less convex but slightly offset towards the 
downstream side of labyrinth disk 12, to be almost tangential with the 
upstream surface 19 of the rotor disk 8. 
The general flexibility of the rim 13 of labyrinth disk 12 is maintained by 
the fact that this main stiffener 23 is slightly offset towards the 
downstream direction. Since this main stiffener 23 is closer to the 
operational elements of the labyrinth disk 12, i.e. the labyrinths 
themselves 10, improves their mechanical strength. Furthermore, his main 
stiffener 23 increases the thermal response time of the labyrinth disk 12, 
since it is placed in the central part of this disk. It improves the 
compatibility of radial displacements of the labyrinth disk 12 with 
respect to turbine disk 8 and thus minimizes forces on the upper support 
means of labyrinth disk 12. These support means also contribute to the 
attachment of labyrinth disk 12 to the rotor. 
In the outer part, these attachment means may indeed be composed of 
attachment teeth 24 placed on the downstream surface 22 of the labyrinth 
disk 12 and in particular, on the outer part of the crown 14. There 
attachment teeth 25 of a bayonet locking system, facing these teeth on the 
upstream surface 19 of the rotor disk 8; the number of these teeth is the 
same as the number of attachment teeth 24 on labyrinth disk 12. Thus, once 
in its radial and axial position, the labyrinth disk 12 may be rotated by 
half the pitch of the attachment teeth 24 and 25 to be fixed behind the 
attachment teeth 24 of the bayonet locking system. 
The axial position of the labyrinth disk 12 is controlled with respect to 
the rotor disk 8, by the downstream surface 22 or rim 13 and crown 14. In 
the solution shown in FIG. 1, ribs 26 are placed on the downstream surface 
22 of the crown 14, in order to stiffen it. They are supported on the 
downstream surface 22 of rotor disk 8, and thus form axial stops. It 
should be noted that the labyrinth disk 12 may be fixed by a system of 
bolts 6 in its inner part. 
Radial stops 27 may be provided on the upstream surface 19 of the rotor 
disk 8, immediately below the bayonet attachment teeth 25, in order to be 
supported on the outer surface of the attachment teeth 24 of labyrinth 
disk 12. Radial stops 27 are only facing attachment teeth 24 when the part 
is in the locking position in the bayonet system. 
No other attachment system is necessary in this embodiment. This thus 
prevents the possible need for an attachment hook on the downstream 
surface 22 of the rim 13 or the crown 14. 
In this embodiment, some of the radial loads are absorbed by radial stops 
27, a part being absorbed by the main stiffener 23 and a smaller part 
being taken on bolts 6. 
FIG. 3 shows a first alternative of the labyrinth disk according to the 
invention. It shows the use of holes 30 placed on base 31 of the single 
main stiffener 33, which is consequently somewhat elongated, but is always 
located immediately below the labyrinth 10. Furthermore, the bayonet 
attachment system is only a single series of teeth 34 on the labyrinth 
disk 32, since they act as attachment teeth that fit behind the attachment 
teeth 35 of the rotor disk 38 bayonet locking system, and also act as 
radial stops, due to their inclined surface, cooperating with the 
corresponding inclined surfaces of the attachment teeth of rotor disk 38. 
These attachment teeth 34 of the labyrinth disk 32 are preferably housed 
in the upper part of ribs 36. 
The second alternative shown in FIG. 4 contains the same holes 30 in the 
main stiffener 33. However, the attachment system shown in FIG. 2 is the 
same. In other words, it uses the same set of attachment teeth 24 on the 
labyrinth disk 42 positioned to correspond with the attachment teeth 25 on 
the rotor disk 8 to form the bayonet system. Radial stops 28 are provided 
in the outer part of ribs 26 and are positioned to correspond with the 
stops 27 on the rotor disk 8. 
FIG. 5 shows a third alternative still using the single main stiffener 33, 
elongated to allow for the use of holes 32 on each side of the stiffener 
disk 52. In this version, teeth 58 contact a stop 59 and the radial stops 
58 are placed more towards the outside of the attachment system. They are 
placed facing the surfaces of the stops 59 of rotor disk 8. The axial 
attachment is made by means of a bayonet attachment system on ribs 56. 
They make use of teeth 54 that engage in the teeth in the bayonet locking 
system 55 corresponding to the rotor disk 8. 
The fourth alternative in FIG. 6 shows a different shape of the crown 64 of 
the labyrinth disk 62. Indeed, from its outer end 61, this crown is almost 
straight, i.e. its downstream surface 63 is further away from the rotor 
disk 68 than in the other embodiments. Consequently, the ribs 66 are 
wider. 
The number of alternatives may also be increased by changing the labyrinth 
disk attachment means on the rotor disk. With reference to FIG. 7, the 
attachment by bolting may be eliminated to be replaced by a bayonet type 
attachment. In this case, there is an axial ring 71 on the inside and 
upstream from the main stiffener 33; a sectional view through this axial 
ring shows that it is in the shape of a foot, as shown in FIG. 7. 
Similarly, the rotor disk 78 also has an axial ring 77 that extends 
approximately parallel to the turbojet centerline A, to come into contact 
with the end of the axial ring 71 of the labyrinth disk 72. 
Attachment means on the labyrinth disk 72 consist of a set of tenons 74 
each penetrating into a rib 76 formed on the outer surface 79 of the axial 
ring 77 of the rotor disk 78. These tenons 74 may be inserted through 
longitudinal notches 75 machined on this outer surface 79 of the axial 
ring 77 of the rotor disk 78. Centering is done by direct contact of these 
two parts at the outer surface 79 of the axial ring 77 of the rotor disk 
78. 
All these embodiments make sizing of this assembly, which forms the 
labyrinth disk, easier at the design stage, and longer lives can be 
obtained. 
The operating capacity of this type of part enables a much more severe 
thermomechanical environment due to the distribution of masses 
accumulating heat, and the ventilation system for this assembly which is 
formed by the labyrinth disk.