EP1577502B1 - Spraybar configuration to control the tip clearance in a gas turbine - Google Patents

Description

Background of the invention

The present invention relates to the general field of game control at the top of moving blades of a gas turbine. It is more particularly a device for controlling a turbomachine high-pressure turbine equipped with means for balancing the air flow rates.

A gas turbine, such as a high-pressure turbomachine turbine, comprises a plurality of blades arranged in the passage of hot gases from a combustion chamber. The blades of the turbine are surrounded, around the entire circumference of the turbine, by an annular stator. This stator defines one of the walls of the flow passage of the hot gases through the turbine.

In order to increase the efficiency of the turbine, it is known to reduce as much as possible the clearance between the top of the turbine blades of the turbine and the parts of the stator that face them.

To achieve this, game-steering means at the top of the blades have been developed. Such means are generally in the form of annular conduits which surround the stator and which are traversed by air taken from other parts of the turbomachine. Depending on the speed of operation of the turbine, the air is injected on the outer surface of the stator in order to modify the temperature thereof and thus causes thermal expansion or contraction of the casing which are able to vary its diameter.

The control devices known until now do not always make it possible to obtain a great uniformity of temperature over the entire circumference of the stator. A lack of temperature homogeneity generates distortions of the stator which are particularly detrimental to the efficiency and the service life of the gas turbine.

EP 1 205 637 describes a control device according to the preamble of claim 1.

Object and summary of the invention

The present invention therefore aims at overcoming such drawbacks by proposing a device for controlling blade clearance at the top of a gas turbine which makes it possible to balance the flow rates of air in the device. control to limit the thermal heterogeneities of the stator of the turbine.

For this purpose, the subject of the invention is a device for controlling the clearance of the blades of a gas turbine rotor according to claim 1.

The balancing of the air flow through the air duct thus makes it possible to limit the thermal heterogeneities at the level of the casing of the turbine. Indeed, it is possible to determine the pressure losses (at the supply of the air circulation ramp or ramps) to balance the air flow rates, and thus the characteristics of the diaphragm.

Each diaphragm is advantageously disposed at an inlet of the air duct so as to create additional pressure drops. It may be in the form of a ring of internal diameter smaller than the internal diameter of the air duct.

Brief description of the drawings

• la figure 1 est une vue en perspective d'un dispositif de pilotage selon l'invention ; et
• la figure 2 illustre l'emplacement des moyens d'équilibrage des débits d'air du dispositif de la figure 1.

Other features and advantages of the present invention will become apparent from the description given below, with reference to the drawings annexed which illustrate an embodiment without any limiting character. In the figures:

• the figure 1 is a perspective view of a control device according to the invention; and
• the figure 2 illustrates the location of the air flow balancing means of the device of the figure 1 .

Detailed description of an embodiment

The figures 1 and 2 illustrate a control device 10 according to the invention. Such a control device can be applied to any gas turbine whose game control at the top of the blades is necessary. This device is particularly applicable to a high-pressure turbomachine turbine.

In the figures, the control device 10 is mounted on an annular casing 12 forming part of the stator of the turbine. This housing 12 of longitudinal axis X-X surrounds a plurality of blades (not shown) forming the rotor of the turbine.

The function of the control device 10 is to control the clearance that exists between the top of the blades of the turbine and the parts of the stator that face them.

The blades of the turbine are surrounded by a plurality of ring segments (not shown) which are mounted on the housing 12 via spacers (not shown). The stator parts that face the top of the blades are thus formed by the inner surface of the ring segments.

The control device 10 figures 1 and 2 consists of three air circulation ramps 14; an internal ramp 14a, a central ramp 14b and an outer ramp 14c. These ramps are mounted circumferentially on the outer surface of the casing 12 by means of fastening rules 16.

The air circulation ramps 14 are spaced axially from each other and are substantially parallel to each other. They are disposed on either side of two annular fins (or bosses) 18 which extend radially outwardly of the housing 12.

The ramps 14 are provided with a plurality of bores 19 arranged facing the external surface of the casing 12 and the fins 18. These bores 19 allow the air circulating in the ramps 14 to be discharged on the casing 12 in order to change the temperature.

Moreover, as illustrated on the figure 1 , the air circulation ramps 14 can be segmented into several angular sectors of distinct ramps (six in number on the figure 1 ) and regularly distributed over the entire circumference of the housing 12.

The control device 10 further comprises two air collection tubes 20 which surround at least part of the air circulation ramps 14. The air collection tubes 20 are intended to supply air to the air circulation ramps 14.

Each air collection tube 20 is supplied with air by at least one air supply tube 22. The air supply tube 22 is connected to zones of the turbomachine in which air can be drawn to supply the piloting device 10. For example, the air sampling zones may be one or more stages of a compressor of the turbomachine.

The sampling of air in the areas of the turbomachine provided for this purpose can be regulated by a control valve (not shown) interposed between these air sampling zones and the air supply tube 22. Such a valve allows to control the control device 10 according to the operating speed of the turbine.

The control device 10 further comprises three air ducts 24 opening in the air collection tube 20 and opening into the air circulation ramps 14 to supply them with air.

An air duct 24 is provided for each angular sector of air circulation ramps 14, that is to say that the piloting device comprises six air ducts 24 regularly distributed over the entire circumference of the casing 12.

As the steering device 10 of this figure 1 comprises an air supply tube 22 supplying two separate air collection tubes 20, each air collection tube 20 extends circumferentially about one half of a circle and thus feeds three air ducts 24. distinguishes these three air ducts 24 by naming them respectively: first air duct 24a for the duct which is closest to the air supply tube 22, second air duct 24b for the duct placed directly downstream of the first pipe 24a, and third air pipe 24c for the pipe farthest from the air supply tube 22.

Each air duct 24 is in the form of a cylinder, for example a metal cylinder, having edges 26 which engage in lateral openings 28 of the air circulation ramps 14. The air ducts 24 are thus welded to the ramps 14.

According to the invention, each air duct 24 is provided with means for balancing the air flow therethrough.

Such means are in the form of a diaphragm 30 disposed at the inlet of the air duct 24, that is to say upstream of the air circulation ramps 14 with respect to the direction of flow of the air. the air coming from the air collection tube 20. More particularly, the diaphragm 30 is placed upstream of the internal ramp 14a.

The presence of this diaphragm 30 in each air duct 24a, 24b and 24c makes it possible to balance the flow rates of air coming from the air collection tube 20 and supplying the air circulation ramps 14 into which the duct opens. air.

On the figure 2 , the diaphragm 30 is in the form of a ring (or washer) metal which is for example welded to the inner walls of the air duct 24 and whose internal diameter d1 representing the air flow section is lower the internal diameter d2 of the air duct 24.

The characteristics of the diaphragm 30 for balancing air flows (such as its internal diameter d1 with respect to that of d2 of the air duct 24) are determined in order to generate additional head losses at the inlet. of each air duct 24 fed by it. Indeed, since the pressure drops are not identical for each air duct 24 fed by the same manifold tube 20, the characteristics of the diaphragms 30 are modeled to generate additional head losses at the inlet of each air duct 24 to obtain a balance in the distribution of air flow.

The modeling process of the characteristics of the diaphragms required for each air duct 24 will now be described from a modeling of the airflows in a piloting device of the prior art.

Table I below gives, for a control device of the prior art (that is to say devoid of air flow balancing means), the distribution of the air flow rates in the three ducts of FIG. air 24a, 24b, 24c supplied by the same air collection tube 20 and in each air circulation ramp 14 of the same ramp sector supplied by each of these air ducts. These air flows were modeled for a cruising operating speed of a turbomachine whose high-pressure turbine is equipped with a game control device. I) - Flow in the first air line 24a (g / s) 32.43 Flow in the internal ramp 14a (g / s) 4.11 Flow in the central ramp 14b (g / s) 7.76 Flow in the external ramp 14c (g / s) 4.35 - Flow in the second air line 24b (g / s) 34,03 Flow in the internal ramp 14a (g / s) 4.31 Flow in the central ramp 14b (g / s) 8.16 Flow in the external ramp 14c (g / s) 4.54 -Debit in the third air line 24c (g / s) 34.42 Flow in the internal ramp 14a (g / s) 4.36 Flow in the central ramp 14b (g / s) 8.26 Flow in the external ramp 14c (g / s) 4.59

In connection with Table I, the results of the ventilation show a heterogeneity in the distribution of air flows, on the one hand at the entrance of each air duct 24a, 24b and 24c (which reaches 6% ), and on the other hand between each sector of air circulation ramps (which reaches 5.8%). The third air duct 24c has an air supply pressure higher than the other two ducts 24a, 24b because of the decrease in the air flow rate in the collector tube air. It results from the heterogeneity of the air flow rates between each air duct that the cooling of the casing 12 is not homogeneous. Temperature gradients may therefore appear and cause mechanical distortions.

From such results, it is thus possible to model the additional pressure drops that it is necessary to apply for each air duct 24 to obtain homogeneity in the distribution of air flows. The modeling of the additional pressure drops then makes it possible to calculate the characteristics of the diaphragms 30 (in particular their internal diameter d1 with respect to the internal diameter d2 of each air duct 24).

For example, from the modeled data of Table I, it is noted that for the second air line 24b, it is necessary to generate an additional pressure drop of about 3.8. To generate such a loss of load, it is necessary to put a diaphragm whose drilling section F1 makes it possible to check: F1 / F2 = 0.51 with F1 drilling section or air flow section of the diaphragm and F2 air flow section of the air duct 24b. For a diameter d2 of the air duct 24b of the order of 39.8 mm, the diameter d1 of the diaphragm 30 to be put in place at the inlet of the second air duct 24b is then of the order of 28.4 mm for a diameter d2 of the air duct 24b of the order of 39.8 mm.

Still from the modeled data of Table I, it is also noted that for the third air line 24c, it is necessary to generate an additional pressure drop of the order 4.5. As described above, such a pressure drop can be obtained with a diaphragm whose drilling section F1 makes it possible to check: F1 / F2 = 0.49 with F1 drilling section or airflow section of the diaphragm and F2 airflow section of 24c air line. For a diameter d2 of the air duct 24c of the order of 39.8 mm, the diameter d1 of the diaphragm 30 to be put in place at the inlet of the second air duct 24c is then of the order of 27.9 mm.

The characteristics of each diaphragm 30 put in place in each air duct 24 which are thus determined from the modeling of additional head losses to be generated are individualized for each air duct. The results of the setting up of such diaphragms are expressed in Table II below. II) - Flow in the first air line 24a (g / s) 32.59 Flow in the internal ramp 14a (g / s) 4.14 Flow in the central ramp 14b (g / s) 7.82 Flow in the external ramp 14c (g / s) 4.37 - Flow in the second air line 24b (g / s) 32.67 Flow in the internal ramp 14a (g / s) 4.12 Flow in the central ramp 14b (g / s) 7.78 Flow in the external ramp 14c (g / s) 4.35 - Flow in the third air line 24c (g / s) 32.52 Flow in the internal ramp 14a (g / s) 4.13 Flow in the central ramp 14b (g / s) 7.79 Flow in the external ramp 14c (g / s) 4.36

In this Table II, it can be seen that, thanks to the introduction of diaphragms in the air ducts 24a, 24b and 24c, the heterogeneities in the distribution of the air flow rates are less than 1% between each air duct. which is negligible. This results in a temperature homogeneity of the housing 12.

Thus, it is possible to balance the flow rates of air circulating in each angular sector of air circulation ramps 14 by adding an individualized balancing diaphragm of the air flow rates to the inlet of the air duct which leads into this angular sector of ramps.

In other words, airflow balancing can be done individually for each airflow ramp sector 14 by adjusting the diaphragm section as needed for a particular boom section. Each air duct 24 can thus be provided with a diaphragm 30 whose characteristics (air flow section) are different for one sector of ramps to another.

Claims (4)

1. A device for tuning clearance at rotor blade tips in a gas turbine rotor, comprising:

   - three annular air flow ducts (14) that are mounted around the circumference of an annular casing (12) of a stator of the turbine, said annular air flow ducts being designed to discharge air onto said casing (12) in order to modify the temperature thereof;

   - at least one tubular air manifold (20) of which a portion at least is disposed around the air flow ducts (14);

   - at least one air feed tube (22) for feeding the tubular air manifold (20) with air; and

   - at least one air pipe (24) opening in the tubular air manifold (20) and opening out into the air flow ducts (14);
   said device for tuning clearance being characterised in that it includes two tubular air manifolds (20), each manifold being connected to three air pipes (24), each air pipe opening out into the three air flow ducts (14), each air pipe (24) being provided with a balancing diaphragm (30) for balancing the air flow going through said pipe, the characteristics of each diaphragm being individualised according to the air pipe (24) in which said diaphragm is placed.
2. A device according to claim 1, characterised in that each diaphragm (30) is disposed at an entrance of the air pipe (24) so as to create additional head losses,
3. A device according to claim 2, characterised in that each diaphragm (30) comes in the form of a ring having an inside diameter (d1) that is smaller than the inside diameter (d2) of the air pipe (24).
4. A turbomachine including at least one device for tuning clearance at rotor blade tips in a rotor according to any one of claims 1 to 3.

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