FR3092134A1 - turbine with improved balancing device - Google Patents

Abstract

T urbine with improved balancing device Turbine (60) for an aircraft turbomachine, comprising an annular hot air flow stream, a sub-stream cavity (68) coaxial with the hot air flow stream, and a rotor comprising at least one movable disc (63) supporting movable vanes (64), wherein the at least one movable disc (63) comprises a balancing device, the balancing device being configured to maintain the vibrations of the turbine (60) within a range of predetermined values, when the temperature within said sub-vein cavity (68) is below a predetermined threshold temperature value, and to change state so as to generate vibrations greater than the vibrations of the predetermined value range, when the temperature within said sub-vein cavity (68) is greater than or equal to said predetermined threshold temperature value. Figure for the abstract: Fig. 2.

Description

turbine with improved balancing device

The invention relates to the field of turbomachines. More specifically, the invention relates to the detection of a cooling anomaly of a turbine in an aircraft turbomachine, and a method for detecting an anomaly of such a turbomachine.

It is common in a turbomachine to take air from a compressor placed upstream, for example a high-pressure compressor to cool parts in downstream stages presenting a hotter environment. Upstream and downstream are defined according to the direction of air flow in the turbomachine. The cooling air taken from the high pressure compressor is for example routed to the low pressure turbine, or to the high pressure turbine of the turbomachine. The supplied air then allows the hot air to be purged and the ventilation of certain parts (e.g. discs, moving blades) of these turbines. Such cooling thus makes it possible to limit the risks of overheating of the moving parts of the turbines, which could lead to their degradation and, in the worst case, to a breakage of these parts.

Furthermore, in order to guarantee the compliance of the cooling devices with aeronautical standards, it is common practice to oversize these cooling devices.

By way of example, it is possible to produce a device comprising several air bleed channels on the high pressure compressor, these channels also ensuring the circulation of the air bleed towards the low pressure turbine or towards the high pressure turbine in order to to cool them. Such channels thus form a device for cooling these turbines. Oversizing this cooling device can then consist of making channels with a larger diameter than necessary, these channels then conveying more air than necessary to cool the low pressure or high pressure turbine, or even increasing the number of canals. Advantageously, this oversizing makes it possible to guarantee in the event of a malfunction, for example in the event of partial obstruction or partial drilling or rupture of a channel, that the device continues to deliver sufficient cooling air to the low pressure turbine or high pressure. Another example of malfunction can be caused by a degradation of the sealing of the turbine, due for example to the wear of a labyrinth seal of the low or high pressure turbine, resulting in a cooling air leak and therefore a decrease in hot air purge flow.

Although reliable, the oversizing of the cooling devices described above leads to more air being taken from the high-pressure compressor than is really necessary in a nominal operating situation of the turbomachine, for example in the absence of failure of a air circulation channel, such failures being otherwise exceptional. Such over-bleeding of air then has a non-negligible impact on the specific fuel consumption (SFC) of the aircraft, and induces a degradation in engine performance.

It is therefore desirable to improve the performance of the turbomachine, in particular to limit the impact of the cooling systems on the fuel consumption of the aircraft.

This presentation relates to a turbine for an aircraft turbomachine, comprising an annular hot air flow duct, a cavity under the duct coaxial with the hot air flow duct, and a rotor comprising at least one mobile disc supporting moving blades, wherein the at least one moving disk comprises a balancing device, the balancing device being configured to maintain the vibrations of the turbine within a range of predetermined values, when the temperature within said cavity under is lower than a predetermined temperature threshold value, and to change state so as to generate vibrations greater than the vibrations of the range of predetermined values, when the temperature within said cavity under a vein is greater than or equal to said threshold value predetermined temperature.

The hot air flowing in the annular vein is the air coming from the combustion of the engine of the turbomachine, and making it possible to drive the blades of the turbine. The sub-vein cavity is an enclosure arranged, for example, radially inside the annular vein. In the remainder of the description, nominal operation of the turbine designates operation in which there is no failure of the cooling circuit of the turbine. It should be noted that this nominal operation can include the wear of the turbomachine, but not the cases of breakdowns such as the rupture of an air supply channel.

Nominal operation of the engine is further characterized by vibrations of the turbine, these vibrations remaining within a range of predetermined values corresponding to nominal operation. These vibrations can be characterized by the vibration frequencies of the turbine, or by the amplitudes of these vibrations, for example.

Thus, a sufficient hot air purging flow rate from the turbine is characterized by a temperature, within this cavity, remaining below a threshold value, and by vibrations remaining within the range of predetermined values.

Exceeding this temperature threshold value indicates an insufficient flow of cooling air, caused by an anomaly that appeared in the cooling circuit of the turbomachine. The turbomachine cooling circuit is understood to mean the circuit followed by the cooling air, from its intake at the level of the compressor, until its injection into the under-vein cavity. Consequently, the faulty element of the turbomachine cooling circuit may be an element at the level of the compressor air intake, one of the channels conveying the air from the compressor to the turbines, an air distribution box, purge passages between the moving blades and fixed parts, and dynamic seals between the moving and fixed parts of the under-vein cavity.

Exceeding the temperature threshold value causes a change of state of the balancing device, preventing the latter from maintaining the vibrations of the turbine within the range of predetermined values corresponding to nominal operation. Thus, this change of state generates vibrations greater than the vibrations of the range of predetermined values, this increase in vibrations being due to the exceeding of the predetermined temperature threshold value. A change in state of the balancing device may include degradation of the latter, melting, creeping, or detachment of the latter.

It is thus possible, by increasing the vibrations beyond the range of predetermined values, to detect the presence of a malfunction or failure, without requiring permanent oversizing of the cooling device. The impact of the cooling system on fuel consumption is thus limited, which improves engine performance. Moreover, this configuration makes it possible to detect the presence of an anomaly without requiring the addition of additional sensors such as a temperature sensor, for example.

In some embodiments, the temperature threshold value is between 550 and 600°C.

This threshold temperature is preferably lower than a critical temperature from which the elements of the turbine such as the blades deteriorate. Thus, when the temperature threshold value within the cavity is reached, the change of state of the balancing device, and thus the generation of significant vibrations of the turbine, makes it possible to detect the presence of an anomaly before the blades, or the disc carrying the blades, from deteriorating.

In certain embodiments, the at least one mobile disc comprises an internal annular web extending between a rim and an internal base, the balancing device being fixed to said rim.

The internal annular veil is the part of the disc arranged in the cavity under the vein. The rim is the part of the disc comprising the cells in which the blades of the turbine are fixed. This arrangement makes it possible to fix the balancing device, without disturbing the flow of hot air in the air stream.

In certain embodiments, the rotor comprises a plurality of mobile discs, and the balancing device is fixed on an upstream mobile disc of the plurality of mobile discs, the upstream mobile disc being arranged upstream of the plurality of mobile discs according to the direction of flow of hot air in the vein.

The upstream disc being the first stage of the discs to be exposed to hot air in the event of a malfunction of the hot air purge, the fact of arranging the balancing device allows the latter to change state more quickly in the event of an increase in temperature due to an anomaly, and thus to improve the efficiency of detecting such an anomaly by the increase in vibration.

In certain embodiments, the rim comprises an upstream face and a downstream face depending on the direction of flow of the hot air in the vein, the balancing device being fixed on the upstream face of the rim.

This arrangement makes it possible to fix the balancing device as close as possible to the hot air purge flow, and thus to further improve the efficiency of anomaly detection.

In certain embodiments, the balancing device is configured to pass from a first state in which it has a first geometric structure, when the temperature within said cavity under the vein is lower than the predetermined threshold value, to a second state in which it has a second geometric structure different from the first geometric structure, when the temperature within said sub-vein cavity is greater than or equal to said predetermined threshold value.

The balancing device has the first geometric structure when the temperature within said subduct cavity is lower than the predetermined threshold value, that is to say during nominal operation. This first geometric structure corresponds to the initial shape of the balancing device, when the latter is fixed to the disc. This first geometric structure allows the balancing device to ensure its function of balancing the turbine in operation, by maintaining the vibrations of the turbine within the range of predetermined values.

When the balancing device changes state, due to exceeding the temperature threshold value, and presents a second geometric structure, different from the first geometric structure, an imbalance of the turbine in operation is generated. This imbalance generates vibrations above the predetermined range of values. It will be understood that the second geometric structure is not limited to a particular structure, but may have any shape different from the first geometric structure, and sufficient to generate such an imbalance. Alternatively, the second state may correspond to at least partial detachment of the balancing device from the disk.

In certain embodiments, the balancing device comprises at least one balancing weight having a predetermined initial mass of between 2 and 100 g, preferably between 2 and 50 g, more preferably between 2 and 10 g.

The mass of each flyweight may vary depending on the number of flyweights in the balancing device. When the balancing device comprises a single flyweight, this may have a mass of approximately 100 g.

In some embodiments, the at least one balancing weight comprises a fusible material configured to melt at least in part when the temperature within the underflow cavity reaches the predetermined threshold value.

In other words, the predetermined threshold value corresponds to the melting temperature of the feeder. The material of the flyweight must therefore preferably be chosen so that its melting temperature is lower than the critical temperature from which the elements of the turbine such as the blades deteriorate. Thus, in the event of partial melting, causing the flyweight to creep, or total, said flyweight passes from the first state in which it has the first geometric structure, to a second state in which it has a second geometric structure, thus causing the imbalance of the turbine in operation, and therefore an increase in vibrations. Alternatively, the second state may include the detachment of at least one flyweight from its attachment point to the disc, also causing the turbine to become unbalanced in operation, and therefore an increase in vibrations.

This presentation also relates to an aircraft turbine engine comprising:
- at least one turbine according to any one of the preceding embodiments,
- a means of measuring vibrations for measuring the vibrations in the turbine,
- A computer connected to the vibration measuring means, and configured to deliver an anomaly signal when the vibrations detected by the measuring means are greater than the vibrations of the predetermined range.

The vibration measurement means may for example be a vibration frequency sensor. In known manner, such a sensor is present in the turbines of turbomachines. Consequently, the turbomachine of this presentation allows the detection of anomalies in the cooling air circuit, using a sensor already present in the turbomachine, without the need to add a new sensor. Moreover, it is not necessary to oversize the cooling device in order to permanently cover abnormal increases in temperature in the event of failures. Indeed, the identification of an anomaly by the computer, as soon as the vibrations exceed the values characteristic of nominal operation, allows a user to take the necessary measures, such as stopping the engine and identifying the origin of the 'anomaly. The impact of the cooling system on fuel consumption is thus limited, which improves engine performance.

This presentation also relates to a method for detecting an anomaly of the turbomachine of this presentation, comprising the following steps:
- detection of vibrations in the turbine, via the vibration measuring means,
- comparison of the vibrations in which, if the vibrations measured during the detection step are greater than the vibrations of the predetermined range, an anomaly signal is delivered by the computer.

This process has the advantage of using equipment already present in the turbomachine, such as vibration sensors and a computer, without requiring the addition of new sensors dedicated solely to the detection of anomalies. Furthermore, the identification of an anomaly by the computer, as soon as the vibrations exceed the values characteristic of nominal operation, allows a user to take the necessary measures, such as stopping the engine and identifying the origin of the 'anomaly. The impact of the cooling system on fuel consumption is thus limited, which improves engine performance.

Figure 1 is a longitudinal sectional view of a turbomachine equipped with an injection device,

Figure 2 is a longitudinal and partial sectional view of a high and low pressure turbine in a turbomachine according to the present description.

Figure 3 is a detailed view of an upstream stage of the low pressure turbine of Figure 2.

The terms "upstream" and "downstream" are subsequently defined with respect to the direction of gas flow through a turbomachine, indicated by the arrow F in Figures 1, 2 and 3.

FIG. 1 illustrates a dual-flow turbomachine 100 comprising in known manner from upstream to downstream successively at least one fan 10, an engine part successively comprising at least one stage of low-pressure compressor 20, high-pressure compressor 30, a combustion 40, at least one stage of high pressure turbine 50 and low pressure turbine 60.

Rotors, rotating around the main axis X of the turbomachine 100 and able to be coupled together by different transmission and gear systems, correspond to these different elements.

In a known manner, a fraction of air is taken from the high pressure compressor 30 and is routed via a cooling duct 32 in order to cool hotter zones of the turbomachine 100, in particular the high pressure turbine 50 and the low pressure turbine 60.

Figure 2 is an enlargement of a zone of the turbomachine 100, illustrating in a simplified manner the downstream part of the high pressure turbine 50 and the upstream part of the low pressure turbine 60.

The downstream part of the high pressure turbine 50 represented here illustrates a stage 51 comprising at least one moving blade 52 assembled on a moving disc 53 integral in rotation with a high pressure shaft 101.

The low pressure turbine 60 illustrated here comprises a plurality of turbine stages 61, 62. A first stage 61, as well as the stages 62 located downstream thereof respectively comprise a set of fixed distributors 70 and 65. Each stage 61, 62 further comprises mobile discs 63 on which is mounted a set of vanes 64 fixed in cells arranged in a rim 631 of the discs 63, the blades 64 being driven in rotation by the mobile disc 63. The mobile discs 63 are fixed axially to each other along the main axis X, to form the various stages 61, 62 of the turbine 60. Each mobile disc 63 comprises an internal base 633 whose central axis is the axis main X, the base 633 being disposed radially towards the inside of the turbine 60, that is to say closer to the main axis X than the rim 631, in the radial direction.

The first stage 61 of the low pressure turbine 60 comprises at least one upstream mobile disk 63a, as well as at least one hollow distributor 70, in which cooling air circulates. In the example illustrated in Figure 2, the distributor 70 forms a single piece with a casing 66 constituting the turbine and is hollow to allow cooling air to pass, exiting via an injection device 80 associated with the distributor 70, comprising a plurality of injectors 81. The following stages 62, located downstream of the first stage 61 of the low pressure turbine 60, each comprise at least one moving blade 64 and a distributor 65, or stator, having the form of a fixed blading. The mobile discs 63 are integral in rotation with a low-pressure shaft 102 extending along the axis XX, while each stator 65 is connected to the casing 66. Each stage 61, 62 of the turbine further comprises a turbine ring 67 located opposite the blades 64 moving, and which is integral with the housing 66.

The turbomachine comprises a cooling device making it possible to convey, via the cooling duct 32, the fraction of air taken from the high pressure compressor 30 to at least one stage of the high pressure turbine 50 and of the low pressure turbine 60. In the embodiment described below, the cooling air fraction withdrawn is distributed at the level of a downstream stage of the high pressure turbine 50 and an upstream stage of the low pressure turbine 60. The high and low pressure 50, 60 are thus cooled. However, the invention is not limited to this embodiment, the fraction of air sampled can also be distributed to other stages of the turbines.

In the embodiment illustrated in Figure 2, the fraction of air taken from the high-pressure compressor 30 flows into the cooling duct 32, then into the hollow distributor 70. The direction of circulation of the fraction of air through the hollow distributor 70 is illustrated by the arrows 71. The fraction of air is then injected via the injectors 81 into a cavity under the vein 58, 68. The distributed air allows in particular to cool the discs 53, 63 of the turbine, as illustrated by the arrows 75. The cooling air injected by the injectors 81 also allows the hot air present in the high pressure turbine 50 and in the turbine to be purged low pressure 60, thus ensuring the cooling thereof. More specifically, the cooling air taken from the high pressure compressor 30 and routed into the inlet cavities 58, 68 constitutes a pressure barrier, or purge, preventing hot air from the combustion chamber and flowing in the primary stream of air circulation of the turbomachine 100, to penetrate into the cavities under stream 58, 68. By primary stream is meant the main stream of air circulation of the turbines. The hot air purge from the high pressure turbine 50 and the low pressure turbine 60 are symbolized here respectively by the arrows 73, 76. The risks of the turbine rotors overheating are thus limited. In particular, by preventing the air from the primary stream from entering the sub-stream cavity, this cavity is cooler than the stream, and the turbine rotors can therefore withstand higher centrifugal forces and be sized to limit stresses. lower.

In known manner, one or more cooling air circulation ducts 32 each take a fraction of cooling air from an air flow circulating in the high pressure compressor 30, and convey the fraction of air taken at least one stage of the high pressure turbine 50 and of the low pressure turbine 60.

A malfunction in the cooling of the turbines 50, 60 can have several causes. One cause of the cooling malfunction may be the malfunction of a duct 32, for example the rupture or accidental blockage of one of the air circulation ducts 32. Another cause of this malfunction may result from excessive wear or the rupture of one or more seals, or dynamic seal of the high pressure turbine 50 or of the low pressure turbine 60. A malfunction in the cooling of the turbine 50, 60 results, for example, from a failure of a labyrinth seal 69 ensuring the pressure insulation of the cavity under the vein 58, 68 of the high or low pressure turbine 50, 60.

The injection device 80 comprises a plurality of injectors 81 distributed on a wall of the distributor 70 around the axis X. In order to simplify the description of this embodiment, a single injector 81 is represented in FIG. 2 in each cavity under vein 58, 68. Moreover, in the rest of the description, the embodiment is described with reference to the low pressure turbine 60, for the sake of brevity. Nevertheless, the characteristics described below are also applicable to the high pressure turbine 50.

FIG. 3 schematically represents a detailed view of an upstream stage of the low-pressure turbine 60. The upstream disc 63a, carrying a plurality of moving blades 64, comprises several annular portions, in particular the rim 631, comprising teeth and the cells in which are mounted the blades 64, the radially internal base 633, and a veil 632 between the rim 631 and the base 633. The dotted line I represents the interface between a blade 64 and the disc 63. This interface I is the mechanically most sensitive part of the blade and disc assembly. Arrow C represents the flow of hot air at high pressure, coming from the combustion chamber and flowing into the primary stream, and arrow 76 represents the purge flow preventing the hot air C from entering the cavity under vein 68.

The injector 81 is an orifice made in the wall of the distributor 70, making it possible to permanently inject, that is to say continuously when the turbomachine is in operation, a flow of cooling air into the cavity under stream 68. This flow makes it possible to ensure the cooling, more precisely the purge 76 and the maintenance of the temperature of the low pressure turbine 60 under nominal operating conditions of the latter, that is to say in the absence one of the malfunctions mentioned above. The dimensions of the orifice are determined so that the flow rate is for example between 270 and 310 g/s.

The turbine 60 further comprises a balancing device making it possible to create a balancing plane of the rotor, and thus to balance the rotor during operation of the turbomachine 100. This balancing makes it possible to maintain a level of vibration of the turbine in a given range of amplitudes and frequencies, this given range corresponding to nominal operation of the turbine. More specifically, the balancing device makes it possible to balance the turbine over a turbomachine speed range ranging from 5,000 to 25,000 revolutions/min. In known manner, a vibration frequency sensor V is arranged in the turbine, for example being fixed to the casing 66 of the turbine 60, and makes it possible to measure the frequencies of the vibrations and amplitudes of the vibrations of the turbine 60 generated by the rotation of the rotor. The V sensor is connected to a computer 110 arranged in the turbine engine, making it possible to record the data detected by the V sensor. The computer 110 is also configured to transmit information to the user of the turbine engine, in particular on the values of the frequencies vibration detected by the V-sensor, or anomaly messages. The computer 110 can be of the FADEC (Full Authority Digital Engine Control) type, or any other type making it possible to perform these functions.

The balancing device comprises at least one balancing weight 90. The number and mass of these weights 90 depend on the balancing requirements. By way of non-limiting example, each flyweight has a mass of between 2g and 10g. A single flyweight is shown in Figures 2 and 3.

According to this embodiment, the flyweight(s) 90 are fixed on the upstream face of the upstream disc 63a, by being for example screwed onto the rim 631 in holes provided for this purpose. The flyweight 90 is thus fixed in the turbine as close as possible to the hot air purge stream 76 of the low pressure turbine 60.

More specifically, the flyweight 90 is arranged so as to be as close as possible to the hot source in the event of a malfunction, in particular when the purge flow rate 76 is insufficient and the hot air C from the vein enters the cavity under the vein. 68. In addition, the weight 90 must not be too close to the vein so as not to melt in the event of only local ingestion of hot air, but it must also not be placed too deeply in the cavity under the vein 68 to melt sufficiently early in the event of a malfunction, and to protect the disc 63 and the attachment between the disc and the blade, at the level of the interface I. Thus, the flyweight 90 is arranged in the radial direction, perpendicular to the axis X, preferably on rim 631 of disk 63, and extends between rim 631 and base 633 of upstream disk 63a.

Furthermore, the flyweight 90 may comprise, for example, a eutectic material comprising 88% aluminum and 12% silicon, and have a melting or creep temperature of 577°C. This melting temperature, and consequently the material chosen for the flyweight 90, is determined so that, under nominal operating conditions, the temperature within the cavity under the vein 68 remains lower than this melting temperature of the counterweight 90. Thus, under nominal operating conditions, the counterweight 90 has a constant mass and shape, thus ensuring that the vibrations of the turbine are maintained within a given range. The weight 90 can for example be a mass pierced at its top, so as to pass through it a fixing screw and part of which is immersed in the flow of hot air. It may have a shape allowing it to be pressed against the disc, for example against the veil 632, so as to prevent any rotation of the weight 90, by means of a rotation stop system (a shoulder resting on the disc for example).

When one of the malfunctions mentioned above occurs, the temperature within the cavity under the conduit 68 increases and reaches values higher than the temperatures representative of nominal operation. When the temperature within the cavity under the vein 68 reaches the melting temperature of the riser 90, the latter melts at least in part and/or deforms under the effect of creep, thus causing a modification of its geometric structure. This fusion can also lead to the complete detachment of the flyweight 90 from its point of attachment to the upstream disc 63a. This deformation due to creep, or the reduction in the mass of the balance weight 90, or even the detachment of the latter, generates an imbalance of the disk 63 of the rotor. The eccentric mass, or unbalance, thus created increases the level of vibrations of the turbine 60 during operation of the turbomachine. Preferably, the balancing device can be configured to generate an eccentric mass on the disc at least equal to 60 g, in the event of creep or detachment of a flyweight 90, corresponding to an imbalance of between 4000 and 4500 cm. g. This range of values depends on the diameter of the turbine (the unbalance being expressed in gram centimeters, i.e. the mass in g multiplied by the radius of the turbine in cm). These values make it possible to guarantee an imbalance capable of generating significant vibration amplitudes, indicating the presence of an anomaly.

The vibration frequency sensor V then detects vibration frequencies at amplitudes above the given range of nominal vibration amplitudes at the corresponding frequencies. When the computer 110 determines such a significant increase in the vibration amplitudes, it then transmits to the user an alert message, indicating the presence of an anomaly having caused an increase in temperature. For example, a failure of the labyrinth seal 69 ensuring the pressure insulation of the cavity under the duct 68 of the low pressure turbine 60 leads to a cooling air leak (see the arrows crossing the labyrinth seals 69), and therefore a reduction of the hot air purge flow 76, causing an increase in temperature within the cavity under the vein 68.

The detection of such an anomaly thus allows the user to take the necessary measures, such as for example replacing the defective labyrinth seal 69 responsible for the increase in temperature in the cavity under the vein 68, then replacing the weights 90 having been degraded by the increase in temperature, by new weights 90 having a mass equal to the initial weights, and a shape identical to these.

Although the present invention has been described with reference to specific embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the different illustrated/mentioned embodiments can be combined in additional embodiments. Accordingly, the description and the drawings should be considered in an illustrative rather than restrictive sense.

It is also obvious that all the characteristics described with reference to a method can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a method.

Claims (10)

Turbine (60) for an aircraft turbomachine, comprising an annular hot air flow path, an under-vein cavity (68) coaxial with the hot air flow path, and a rotor comprising at least one mobile disc (63) supporting moving blades (64), wherein the at least one moving disc (63) includes a balancing device, the balancing device being configured to maintain the vibrations of the turbine (60) within a range of predetermined values, when the temperature within said in-vein cavity (68) is lower than a predetermined temperature threshold value, and to change state so as to generate vibrations greater than the vibrations of the range of predetermined values, when the temperature within said in-vein cavity (68) is greater than or equal to said predetermined temperature threshold value. Turbine (60) according to Claim 1, in which the threshold temperature value is between 550 and 600°C. Turbine (60) according to Claim 1 or 2, in which the at least one mobile disc (63) comprises an internal annular web (632) extending between a rim (631) and an internal base (633), the device for balancing being fixed on said rim (631). Turbine (60) according to any one of claims 1 to 3, in which the rotor comprises a plurality of mobile discs (63), and in which the balancing device is fixed to an upstream mobile disc (63a) of the plurality of mobile discs (63), the upstream mobile disc (63a) being arranged upstream of the plurality of mobile discs (63) in the direction of flow of the hot air in the stream. Turbine (60) according to claim 3 or 4, in which the rim (631) comprises an upstream face and a downstream face according to the direction of flow of the hot air in the stream, the balancing device being fixed on the upstream face of the rim (631). Turbine (60) according to any one of Claims 1 to 5, in which the balancing device is configured to pass from a first state in which it has a first geometric structure, when the temperature within the said cavity under a stream (68) is less than the predetermined threshold value, to a second state in which it has a second geometric structure different from the first geometric structure, when the temperature within said cavity under the vein is greater than or equal to said predetermined threshold value. Turbine (60) according to any one of Claims 1 to 6, in which the balancing device comprises at least one balancing weight (90) having a predetermined initial mass of between 2 and 100 g, preferably between 2 and 50 g, more preferably between 2 and 10 g. Turbine (60) according to claim 7, wherein the at least one balancing weight (90) comprises a fusible material configured to melt at least in part when the temperature within the underflow cavity (68) reaches the threshold value predetermined. Aircraft turbomachine (100) comprising:
- at least one turbine (60) according to any one of the preceding claims,
- a vibration measuring means (V) for measuring the vibrations in the turbine (60),
- a computer (110) connected to the vibration measuring means (V), and configured to deliver an anomaly signal when the vibrations detected by the measuring means (V) are greater than the vibrations of the predetermined range. A method of detecting an anomaly of the turbomachine (100) according to claim 9, comprising the following steps:
- detection of vibrations in the turbine (60), via the vibration measuring means (V),
- comparison of the vibrations in which, if the vibrations measured during the detection step are greater than the vibrations of the predetermined range, an anomaly signal is delivered by the computer (110).