|Title of Invention||
"A TURBINE RING"
|Abstract||A turbine ring forming a rotor shroud, the ring being of the type constituted by a plurality of sectors (11) interconnected end to end with interposed sealing systems comprising tongues (27, 28, 29) extending between adjacent sectors, said tongues being housed in slots formed facing each other in adjacent radial faces of said sectors, each sealing system being constituted by rectilinear tongues engaged in respective rectilinear slots (31, 32, 33) in said radial faces, and in that the slots formed in each radial face are independent, without communication there between, the ring being characterized in that each sealing system between two sectors comprises first and second tongues (2 7, 28) extending in a chevron configuration from the insides of said radial faces, said tongues being engaged in slots (31, 32) in said radial faces defining their relative positions, and in that said second tongue (28) extends between a point (C) situated close to an outlet edge of each sector, towards the inside, and a point (D) situated close to said first tongue, substantially between its middle and a point two-thirds of the way therealong.|
|Full Text||A TURBINE RING
The invention relates to a turbine ring forming the outer shroud of the rotor of said turbine. The invention applies particularly to a high pressure turbine situated immediately downstream from the combustion chamber of an airplane turbojet. It relates more particularly to the interconnection and cooling of the sectors making up said turbine ring.
In a turbine of the kind mentioned above, driven by gas at very high temperature, the rotor rotates inside a stationary turbine ring constituted by a plurality of curved sectors that are united end to end circumferentially in order to form the rotor shroud. The temperature of the gas driving the blade wheel is such that the thermomechanical stresses that are created between the sectors can lead to deterioration, reducing the lifetime of such rings. Typically, small cracks and/or flaking can often be observed on the inside (or "hot") face of the sectors, mainly in the vicinity of the connections between adjacent sectors.
To provide the ring with better sealing, reducing leaks of non-working air, and in order to prevent hot gas being reinserted, sealing systems are provided between such adjacent sectors, said systems comprising tongues that extend between the sectors and that are received in slots formed facing them in the adjacent radial faces of said sectors.
For example, a prior art sector 1 shown in Figure 1 includes a sealing system comprising four tongues 2-5 received in slots 6, 7, and 8. The tongue 3 is bent and extends between two slots 6 and 7 that open out into each other and that receive the other tongues 2 and 4 which are straight. It is difficult to machine the slots accurately, in particular because of the difference in thickness needed to be able to insert the bent tongue. It is difficult to position this tongue properly. In addition, the tongue 2 is received entirely within a slot
6 that is parallel to the hot face 9 of the sector and that is close thereto. Unfortunately, the mere fact of forming the slot leads to stress concentration zones which, when situated close to a hot surface, weaken the part and accelerate deterioration thereof. The invention makes it possible to eliminate these drawbacks, in particular.
The invention thus provides firstly a turbine ring forming a rotor shroud, the ring being of the type constituted by a plurality of sectors interconnected end to end with interposed sealing systems comprising tongues extending between adjacent sectors, said tongues being housed in slots formed facing each other in adjacent radial faces of said sectors, the ring being characterized in that each sealing system is constituted by rectilinear tongues engaged in respective rectilinear slots in said radial faces.
The fact of making the sealing system from tongues that are straight simplifies making the slots and facilitates mounting the tongues therein. In addition, control over the positioning of the tongues is improved because of the bear against surfaces that are under better control since they are strictly linear. Overall, leakage sections are made smaller. A configuration with only three tongues is described below.
More particularly, the above-defined turbine ring is also advantageously characterized in that each sealing system comprises a first tongue and a second tongue extending in a chevron configuration on the inside of said radial faces, said tongues being engaged in rectilinear slots of said radial faces defining their relative positions accurately. As a result, air leakage between two consecutive sectors can be accurately calibrated. Such leakage can thus be identical through all of the inter-sector spaces. Overall, it is estimated that the leakage rate can be reduced by 10% to 20%
compared with the above-described prior art configuration.
Another advantage of the invention lies in the fact that arranging the tongues in a chevron configuration on the hot face side makes it possible both to move the stress concentration zones further away from said hot face (since the slots go away therefrom), and also to provide sufficient space between the tongues and the hot face to allow cooling air ejection channels to open out therein, which channels are fed from a cavity formed within the sector itself.
More precisely, the invention also provides a turbine ring as defined above in which each sector includes a cooling air flow cavity, the ring being characterized in that it further includes air ejection channels extending between said cavity and at least one radial face of the sector, these channels opening out in said radial face between an inner edge thereof and said first and second tongues.
The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description given purely by way of example and made with reference to the accompanying drawings, in which:
- Figure 1 shows a radial face of a sector used in building up a prior art turbine ring;
- Figure 2 shows a radial face of a sector used in building up a tongue ring in accordance with the invention;
- Figure 3 is a diagrammatic view showing two consecutive sectors seen looking along III in Figure 2;
- Figure 4 is a diagrammatic view of the casing associated with such ring sectors;
- Figure 5 is a diagrammatic view showing the various possible orientations for said first and second tongues; and
- Figures 6 to 8 are fragmentary views showing variants of one of the sectors shown in Figure 3.
In the drawings, and more particularly in Figures 2 to 4, there can be seen turbine ring sectors 11 constituting the stationary shroud of a rotor (not shown), specifically a rotor in the high pressure turbine of a turbojet. This turbine is located downstream from the combustion chamber. Specifically, such a ring is made up of thirty-two curved ring sectors 11 such as those shown, disposed end to end to form a slightly conical shroud surrounding said rotor. Each sector 11 is constituted by a slightly curved thick plate so as to build up the ring. There is a substantially rectangular inside face 12 that is slightly concave and that is referred to as the "hot" face since it comes into contact with the stream of hot gas, and a substantially rectangular outer face 14 referred to as the "cold" face. Relative to the flow direction of hot gas passing through the rotor, there is also an inlet edge 16 facing the combustion chamber nozzle, and an opposite outlet edge 18. Each sector 11 also has two radial faces 20 and 21 via which it is connected circumferentially to the adjacent sectors via sealing systems 26 (see Figure 2) as mentioned above. Each sealing system 26 is constituted by a set of tongues engaged in corresponding slots defined in said facing radial faces 20, 21. Each tongue is engaged in two slots belonging to two circumferentially-adjacent ring sectors.
The tips of the rotor blades travel past the inner surface of the ring as constituted in this way. The direction of rotation is represented by arrow F in Figure 3. The hot gas expelled from the combustion chamber thus flows close to the inside surface of the ring, which must therefore withstand very high temperatures. It is therefore necessary both to minimize temperature gradient within the structure of the ring as much as possible (thereby minimizing in particular
leakages of gas between the sectors), and also to cool said ring effectively. For this purpose, use is made of a fraction of the air delivered by the compressor feeding the combustion chamber. To do this, each sector 11 is hollow and includes a cooling air flow cavity 35 fed from the outside.
Figure 4 is a highly diagrammatic view showing the position of the ring made up from the set of sectors 11. A turbine casing 15 co-operates with the ring to define an annular cavity 17. The assembly extends radially outside the high pressure bladed wheel 19, itself interposed axially between the high pressure nozzle 21 and the low pressure nozzle 23. Air coming from the compressor is taken from a point upstream of the combustion chamber and penetrates (via holes) into the annular cavity 17. This cavity thus feeds all of the sectors in the ring. Each ring sector (Figure 3) has two distinct cavities 39 and 40 of zigzag shape, separated by a partition 42, and fed via respective orifices 37 and 38. The air flowing in the cavity 39 escapes via a series of ejection channels 44 opening out in the inlet side 16 of the ring sector, while the air which flows in the cavity 40 escapes via a series of ejection channels 44 opening out in the outlet side 18 of the ring sector.
Apart from the sealing systems between the sectors, the arrangement described above is already known. The invention relates in particular to an advantageous improvement in said sealing systems between the sectors.
More particularly (Figures 2 to 4), each sealing system 26 is constituted in this case by three rectilinear tongues engaged in respective rectilinear slots in the radial faces of two adjacent sectors. Specifically, each sealing system (Figure 2) comprises a first tongue 27 and a second tongue 28 situated on the insides of said radial faces, i.e. beside the hot faces of the sectors. The tongues 27 and 28 are arranged in a chevron configuration, i.e. they are engaged in slots 31
and 32 in said radial faces that extend at an angle relative to the inner and outer faces 12 and 14 of the sectors. These slots define the relative positions of the two tongues.
In addition, each sealing system includes a third tongue 29 extending substantially from one end to the other of the adjacent sectors, parallel to the axis of the ring and on the outer side of said radial faces. The tongue 29 is engaged in rectilinear slots 33 in the adjacent sectors. As can be seen in Figure 2, the first tongue 27 extends between a point A situated close to the inlet side of the two sectors close to the inside (i.e. close to the hot faces) and a point B situated close to the third tongue 29. The second tongue 28 is positioned so as to extend between a point C situated close to the outlet side 18 of each of the sectors close to the inside and a point D situated close to the first tongue, substantially between the middle and a two-thirds point therealong starting from point A.
The pressures which become established in the spaces between the sectors on the inside and on the outside, and also between the third tongue and said first and second tongues taken together are such that said first and third tongues 27, 29 are pressed against the inside faces of the slots 31, 33 in which they are received, while said second tongue 28 is pressed against the outside faces of the slots 32 in which it is received, as can be seen in Figure 2.
The length of the first tongue 27 depends on the angle it makes with the first tongue 29. Once this angle has been determined (several possibilities are shown in Figure 5), the position and the length of the second tongue can be derived therefrom.
The angle defined between the first and third tongues may lie in the range 15° to 70°, approximately.
The slots can be machined accurately and they are well located. The tongues can be inserted in these slots
and their relative positions can be well controlled. As a result the leakage section between said first and second tongues (at Sx) and the leakage section between the first and third tongues (at S2) are well controlled.
With reference more particularly to Figures 2 and 3, another advantageous feature of the invention can be seen concerning the cooling of the radial faces 2 0 and 21 with air from the cooling air flow cavity 35. It can be seen that each sector has air ejection channels 50 extending between the cavity 40 and at least one radial face of the sector. These channels open out in the radial face 20 between its inside edge (hot face) and said first and second tongues 27, 28. The chevron configuration of these two tongues leaves room to form these air ejection channels. These channels are disposed in a row parallel to the axis of the ring. In the example of Figure 3, they all extend perpendicularly to the radial face. In the example of Figure 6, some of the channels 50 extend perpendicularly to the radial face while others situated at the ends of said row, or at least one of them, are at an angle diverging from the others, on going from the cavity towards the radial face. The angle between the diverging channels may lie in the range 10° to 120°. In certain circumstances, channels could be provided at angles that converge in the opposite direction. In the variant of Figure 7, the channels are parallel and form an angle relative to a direction perpendicular to the radial face. The angle is such that the air is ejected with a component directed towards the rear of the ring. In the variant of Figure 8, the channels are parallel and make an angle relative to a direction perpendicular to the radial face. The angle is such that the air is ejected with a component directed towards the front of the ring.
In the example, the channels 50 open out it the radial face 2 0 that is the first face to be reached by the blades, given the direction of rotation represented
by arrow F. This is favorable for avoiding or limiting any reintroduction of hot gas into the inter-sector spaces. It would also be possible to make similar channels through the opposite wall, opening out in the radial face 21. The air escaping from the channels 50 cools the wall through which they are formed by convection (thermopumping), while the opposite wall (face 21) is cooled by the impact of the jets of air. In addition, the jets of air escaping from the channels 50 set up a kind of fluidic system preventing hot gas being ingested.
It should also be observed that the slots 31, 32, and 33 are preferably independent, i.e. they do not communicate with one another. This avoids any need to make any tool clearance at the junction between two slots. Leakage sections between the sectors are also reduced.
The invention also provides any ring sector or any assembly of ring sectors presenting the characteristics described above.
1. A turbine ring forming a rotor shroud, the ring being of the type constituted by a plurality of sectors (11) interconnected end to end with interposed sealing systems comprising tongues (27, 28, 29) extending between adjacent sectors, said tongues being housed in slots formed facing each other in adjacent radial faces of said sectors, each sealing system being constituted by rectilinear tongues engaged in respective rectilinear slots (31, 32, 33) in said radial faces, and in that the slots formed in each radial face are independent, without communication there between, the ring being characterized in that each sealing system between two sectors comprises first and second tongues (27, 28} extending in a chevron configuration from the insides of said radial faces, said tongues being engaged in slots (31, 32) in said radial faces defining their relative positions, and in that said second tongue (28) extends between a point (C) situated close to an outlet edge of each sector, towards the inside, and a point (D) situated close to said first tongue, substantially between its middle and a point two-thirds of the way therealong.
2. The turbine ring as claimed in claim 1, wherein each sealing system includes a third tongue (2 9) extending substantially from one end to the other of the adjacent sectors, parallel to the axis of the ring, and on the outside of said radial faces.
3. The turbine ring as claimed in claim 2, wherein said first tongue (27) extends between a point (A) situated close to an inlet edge of each sector, towards the inside, and a point (B) situated close to said third tongue.
|Indian Patent Application Number||936/DEL/2005|
|PG Journal Number||41/2013|
|Date of Filing||12-Apr-2005|
|Name of Patentee||SNECMA|
|Applicant Address||2 BD DU GENERAL MARTIAL VALIN, 75015-PARIS, FRANCE|
|PCT International Classification Number||F02C 7/00|
|PCT International Application Number||N/A|
|PCT International Filing date|