Emergency ventilation device for a turbine of a turbine engine, triggered by the melting of a locking means

Abstract

An aircraft turbomachine module comprising a ventilation device configured to have a cooling air flow circulate in the turbomachine module, the ventilation device comprising an air outlet, blocking means fixed to the air outlet and mobile between a blocking position of the air outlet and an opening position of the air outlet, and locking means configured to maintain the blocking means in one of the blocking position and the opening position when the temperature within the module is less than a predetermined threshold value, the blocking means being configured to adopt the other of the blocking position and the opening position when the temperature within the module is greater than said predetermined threshold value.

Claims

1. An aircraft turbomachine turbine comprising a ventilation device configured to have a cooling air flow circulate in the turbine, the turbine comprising a annular vein of hot airflow, a sub-vein cavity coaxial to the hot airflow vein, the ventilation device comprising: an injection device configured to inject cooling air into the sub-vein cavity, at least one tube extending into the sub-vein cavity, a first end of the tube being fixed to a wall of the sub-vein cavity, a second end of the tube being an air outlet, blocking means fixed to the second end and mobile between a blocking position of the air outlet and an opening position of the air outlet, and locking means configured to maintain the blocking means in the blocking position when the temperature within the sub-vein cavity is less than a predetermined threshold value, the locking means comprising a fusible material configured to melt so as to let the blocking means adopt the opening position when the temperature within the module is greater than said predetermined threshold value wherein the blocking means are a flap mobile between the blocking position and opening position by means of a hinge fixed to the second end of the tube.

2. The turbine according to claim 1, wherein, when the temperature within the turbine is less than the predetermined threshold value, the locking means present a volume of between 5 and 20 mm.sup.3.

3. The turbine according to claim 1, wherein the locking means are a deposit of eutectic material in an angle between the flap in blocking position and the wall of the tube.

4. The turbomachine comprising the turbine according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and its advantages will be better understood from the following detailed description of different embodiments of the invention given by way of non-limiting examples, this description making reference to the pages of appended figures, in which:

(2) FIG. 1 is a longitudinal sectional view of a turbomachine,

(3) FIG. 2 is a longitudinal and partial sectional view of a high-pressure and low-pressure turbine of the turbomachine of FIG. 1,

(4) FIG. 3 is a sectional view (at left) and a perspective view (at right) of an air outlet of a ventilation device of the turbine of FIG. 2, with blocking means in blocking position,

(5) FIG. 4 is a sectional view (at left) and a perspective view (at right) of the air outlet of FIG. 3, with the blocking means in opening position,

(6) FIG. 5 is a sectional view of a nacelle of the turbomachine of FIG. 1, with blocking means in opening position (at left), and in blocking position (at right).

DESCRIPTION OF THE EMBODIMENTS

(7) A first embodiment of the present disclosure will be presented in reference to FIGS. 1 to 4.

(8) The terms ‘upstream’ and ‘downstream’ are defined hereinbelow relative to the direction of flow of gases through a turbomachine, indicated by the arrow F in FIGS. 1 and 2.

(9) FIG. 1 illustrates a dual-flow turbomachine 100 comprising in a manner known per se from upstream to downstream successively at least one fan 10, an engine part comprising successively at least one low-pressure compressor stage 20, high-pressure compressor stage 30, combustion chamber 40, at least one high-pressure turbine stage 50 and low-pressure turbine stage 60. In the present embodiment, the turbomachine module is a high-pressure turbine stage 50 or low-pressure turbine stage 60.

(10) Rotors, rotating around the main axis X of the turbomachine 100 and which can be joined together by different transmission and gear systems correspond to these different elements.

(11) As is known, a fraction of air is drawn on the high-pressure compressor 30 and is forwarded by means of a cooling conduit 32 for cooling of the warmer zones of the turbomachine 100, especially the high-pressure turbine 50 and the low-pressure turbine 60.

(12) FIG. 2 is an enlargement of a zone of the turbomachine 100, a simplified illustration of the downstream part of the high-pressure turbine 50 and the upstream part of the low-pressure turbine 60.

(13) The downstream part of the high-pressure turbine 50 shown here illustrates a stage 51 comprising at least one mobile vane 52 assembled on a mobile disc 53 solid in rotation with a high-pressure shaft 101.

(14) 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 of the latter, comprise a set of fixed distributors 70 and 65 respectively. Each stage 61, 62 also comprises a mobile disc 63 on which a set of vanes 64 driven in rotation by the disc 63 mobile is mounted. The first stage 61 of the low-pressure turbine 60 comprises at least one mobile vane 64, as well as at least one hollow distributor 70 in which cooling air circulates. In the example illustrated in FIG. 2, the distributor 70 forms a single part with a housing 66 constituting the turbine and is hollow to allow cooling air through, exiting by way of an injection device 80 joined to the distributor 70, comprising a plurality of injectors. The following stages 62, located downstream of the low-pressure turbine 60, each comprise at least one mobile vane 64 and a distributor 65 in the form of fixed blading. The mobile disc 63 is solid in rotation with a low-pressure shaft 102 extending according to the axis X-X, while each stator 65 is connected to the housing 66. Each turbine stage 61, 62 also comprises a turbine ring 67 located opposite the mobile vanes 64, and which is attached to the housing 66.

(15) According to the present disclosure, the turbomachine comprises a cooling device for conveying the fraction of air drawn on the high-pressure compressor 30 via the cooling conduit 32 to at least one stage of the high-pressure turbine 50 and of the low-pressure turbine 60. In the embodiment described hereinbelow, the fraction of cooling air drawn is distributed in the region of a downstream stage of the high-pressure turbine 50 and an upstream stage of the low-pressure turbine 60. The high-pressure and low-pressure turbines 50, 60 are cooled accordingly. However, the invention is not limited to this embodiment, with the fraction of air drawn also able to be distributed to other stages of the turbines.

(16) In the embodiment illustrated in FIG. 2, the fraction of air drawn in the high-pressure compressor 30 flows into the cooling conduit 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 injection devices 80 into a sub-vein cavity 58, 68. The distributed air especially cools the discs 53, 63 of the turbines, as illustrated by the arrows 75. The cooling air injected by the injection devices 80 also allows purging of hot air present in the high-pressure turbine 50 and in the low-pressure turbine 60, ensuring cooling of the latter. More precisely, the cooling air collected in the high-pressure compressor and conveyed as far as the sub-vein cavities 58, 68 constitutes a pressure barrier or purge, preventing hot air coming from the combustion chamber and flowing into the main air circulation vein of the turbines, that is, into the primary air circulation vein of the turbomachine 100, to enter the sub-vein cavities 58, 68. Purging of the hot air of the high-pressure turbine 50 and of the low-pressure turbine 60 is symbolised here by arrows 73, 76 respectively. The risks of overheating of the rotors of turbines are then limited. In particular, preventing air from the primary vein from re-entering the sub-vein cavity makes this cavity cooler than the vein, and the turbine rotors can therefore resist higher centrifugal forces and be dimensioned on lower limit stresses.

(17) As is known, one or more conduits 32 for cooling air circulation each draw a fraction of cooling air of airflow circulating in the high-pressure compressor 30, and convey the fraction of drawn air in the region of at least one stage of the high-pressure turbine 50 and of the low-pressure turbine 60.

(18) A cooling malfunction of the turbines 50, 60 can have several causes. One cause of the cooling malfunction can be malfunction of a conduit 32, for example accidental breakage or blocking of one of the conduits 32 for air circulation. Another cause of this malfunction can result from excessive wear or breakage of one or more sealing joints, or dynamic seal of the high-pressure turbine 50 or of the low-pressure turbine 60. By way of example a cooling malfunction of the turbine 50, 60 results from a defect in a labyrinth seal 69 ensuring pressure insulation of the sub-vein cavity 58, 68 of the high-pressure or low-pressure turbine 50, 60.

(19) The injection device 80 comprises a plurality of first injectors 81, and a plurality of second injectors 82, the first and second injectors 81, 82 being distributed over a wall of the distributor 70 around the axis X. For a simpler description of this embodiment a single first injector 81 and a single second injector 82 are shown in FIG. 2 in each sub-vein cavity 58, 68. Also, throughout the description the embodiment is described in reference to the low-pressure turbine 60, for the sake of conciseness. Yet, the characteristics described hereinbelow apply also to the high-pressure turbine 50.

(20) The first injector 81 is an orifice made in the wall of the distributor 70 for injecting permanently, that is, continuously when the turbomachine is in operation, a first cooling air flow into the sub-vein cavity 68. This first debit ensures cooling, more precisely the purge 76 and the temperature maintenance of the low-pressure turbine 60 in nominal operation conditions of the latter, that is, in the absence of one of the malfunctions mentioned hereinabove. The dimensions of the orifice are determined so that the first flow is between 270 and 310 g/s for example.

(21) The second injector 82 (ventilation device) comprises a tube 84 a first end of which is fixed to the distributor 70, and a second end comprising an air outlet blocked by a flap 86, acting as blocking means during nominal operation of the turbine 60. The flap 86 is fixed to the second end of the tube 84 by means of a hinge 861. Other means of fastening the flap 86 to the tube 84 are possible, such as for example a stop chain, once the flap 86 stays attached mechanically to the tube 84 even if the temperature within the sub-vein cavity 68 is greater than the melting temperature defined hereinbelow.

(22) In nominal operation of the turbine 60, the flap 86 is kept in blocking position, preventing the air present in the tube 84 from entering the sub-vein cavity 68. This holding in blocking position is achieved by means of locking means 87. The locking means 87 are a mechanical part fixed and inserted in between the internal wall of the tube 84 and the wall of the flap 86 on the cavity side. This mechanical part acts as a wedge preventing the flap from opening, that is, moving to opening position, by resisting forces exerted by air on the inner wall side of the tube 84 of the flap 86.

(23) The locking means 87 can be produced by deposit of eutectic material comprising for example 88% aluminium and 12% silicon, and having a melting temperature of 577° C. This melting temperature, and consequently the material selected for the locking means 87, is determined so that in nominal operation conditions the temperature within the sub-vein cavity 68 remains under this melting temperature of the locking means 87. In this way, in nominal operation conditions the flap 86 completely blocks the second end of the tube 84, so that the cooling air cannot be injected into the sub-vein cavity by way of the second injector 82. The locking means 87 are configured to resist differences in pressure in nominal operation conditions when the flap 86 is blocking the end of the tube 84, between the air present in the tube 84 and the sub-vein cavity 68. The locking means 87 are configured for example to resist a pressure differential between the air present in the tube 84 and the sub-vein cavity 68 of the order of 3 bars.

(24) When malfunctions as mentioned hereinabove occur, the temperature within the sub-vein cavity 68 rises and reaches values greater than temperatures representative of nominal operation. When the temperature within the sub-vein cavity 68 reaches the melting temperature of the locking means 87, the latter melts, thus releasing the flap 86, the latter being able to pivot around the hinge 861 under the effect of pressure exerted by air in the tube 84. An additional cooling air flow, for example between 80 and 90 g/s, can thus be injected into the sub-vein cavity 68 by means of the second injector in addition to the first flow injected by the first injector. The sum of the first and second flows is greater than the ranges of flows representative of nominal operation, and covers instances of malfunctions, characterised by a rise in temperature in the turbine. In this way, it is possible to emphasise the cooling of discs 63, before these elements become damaged by an excessive rise in temperature. In particular, injection of the additional cooling air flow boosts the purge rate 76, also preventing hot air from the vein entering the sub-vein cavity 68.

(25) A second embodiment of the present disclosure will be presented in reference to FIG. 5.

(26) In the present embodiment, the turbomachine module is a turbomachine nacelle 110. The nacelle 110 has an annular form and defines an annular flow vein of a secondary flow. The nacelle 110 comprises an internal face 110a defining said annular vein, and an external face 110b in contact with the ambient air. Between the internal face and the external face the nacelle comprises an internal compartment 116 housing equipment such as electronic accessory cases, pumps and oil and fuel tanks, and others (not shown).

(27) A ventilation device comprises air admission means 112 on the external face 110b, and an air outlet on the internal wall 110a. As an alternative, the air admission means 112 can be arranged on the internal wall 110a, and the air outlet can be arranged on the external face 110b. The air admission means 112 can be a bailer for example, via which cooling air can enter the internal compartment 116. The air outlet can comprise an air outlet grille 114, via which the cooling air circulating in the internal compartment 116 can be evacuated. The circulation of a cooling air flow by means of the ventilation device (arrows in FIG. 5 to the left) ensures the thermal resistance of equipment present in this compartment.

(28) Malfunction of equipment present in the internal compartment 116 can cause a fire inside the latter. The effect of airflow circulating in the compartment is to fuel this fire.

(29) Blocking means 120 block the air outlet grille 114 in the event of fire. The blocking means 120 comprise a lid 122, or detachable door, and a spring 121. The spring 121 is fixed to the lid 122 on one side and to a wall of the air outlet fixed to the nacelle 110 and immobile relative to the latter. The spring 121 is configured to work under compression so as to push the lid 122 towards the air outlet grille 114.

(30) In nominal operation, that is, in the absence of an anomaly causing a fire, the lid 122 must be kept in opening position so as to let the cooling air present in the internal compartment 116 be evacuated via the air outlet grille 114, accordingly maintaining a cooling air flow in the internal compartment 116 necessary for the thermal resistance of the equipment. To this end, locking means 130 are inserted in between the internal wall 110a of the nacelle 110 and the lid 122, acting as a wedge to retain an adequate flow cross-section for ejection of air via the air outlet grille 114.

(31) The locking means 130 can be a fusible rod constituting eutectic material comprising for example 45% silver, 38% gold and 17% germanium, and having a melting temperature of 525° C. This melting temperature, and consequently the material selected for the locking means 130, is determined so that, in nominal operation conditions, the temperature within the internal compartment 116 stays under this melting temperature of the locking means 130. In this way, in nominal operation conditions, the lid 122 remains in opening position, so that the cooling air can circulate in the internal compartment 116. The fusible rod 130 is configured to be sufficiently thick so as to resist the force exerted by the spring 121, and sufficiently fine to leave an adequate flow cross-section to have limited or no impact on the cooling air flow.

(32) When a malfunction as mentioned hereinabove does occur, the temperature within the internal compartment 116, in particular the temperature of the cooling air circulating in the internal compartment 116, rises due to the fire and reaches values greater than temperatures representative of nominal operation. When this temperature reaches the melting temperature of the locking means 130, the latter melts, consequently releasing the lid 122, the latter able to move to the blocking position under the effect of pressure exerted by the spring 121 (FIG. 5, at right). In this blocking position of the air outlet grille 114, the cooling air can no longer circulate in the internal compartment 116, such that the fire present in the latter is snuffed out.

(33) Even though the present invention has been described in reference to specific exemplary embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention such as defined by the claims. In particular, individual characteristics of the different embodiments illustrated/mentioned can be combined in additional embodiments. Consequently, the description and the drawings must be considered in an illustrative rather than a restrictive sense.

(34) It is also evident that all the characteristics described in reference to a process are transposable, singly or in combination, to a device, and inversely all the characteristics described in reference to a device are transposable, singly or in combination, to a process.