FR3117169A1 - NOZZLE FOR A TURBOMACHINE COMPRISING A CATALYTIC CONVERTER - Google Patents

Abstract

The nozzle (1) for an aircraft turbomachine comprises an annular wall (4) comprising an orifice (6) for discharging an air flow likely to include oil or fuel residues. The annular wall (4) has an inner face (4A) to which is attached a catalytic converter (8) which filters at least part of the air flow to treat oil or fuel residues. Their treatment by the catalytic converter (8) makes it possible to avoid the risk of fouling of an exchanger or of leaving black marks in the nozzle (1) and to limit the emissions of unburnt hydrocarbons. Figure for abstract: Figure 1

Description

NOZZLE FOR A TURBOMACHINE COMPRISING A CATALYTIC CONVERTER

Technical field of the invention

The present invention relates to a nozzle for an aircraft turbomachine, in particular a helicopter or airplane, comprising a catalytic converter, as well as a turbomachine comprising such a nozzle.

Technical background

Conventionally, a turbomachine comprises, from upstream to downstream, that is to say in the direction of flow of the gas flows, possibly a fan, one or more compressors, a combustion chamber, one or more turbines, and an ejection nozzle for the combustion gases leaving the turbine or turbines.

The turbines and/or the compressor, which form rotating assemblies, must be equipped with sealing devices. These sealing devices are generally made by seals of the pressurized labyrinth type arranged in the vicinity of the rotating assemblies. To do this, air is taken directly from the air stream of the turbomachine. This air then passes through the turbomachine through the various labyrinths provided for this purpose, then is evacuated to the outside of the turbomachine to limit the rise in pressure of the other zones of the turbomachine, in particular the reduction gear, the accessory box, etc. .

However, this air having passed through different zones of the turbomachine, it is loaded with oil used for cooling and lubricating the bearings and pinions of the rotating assemblies. To prevent the discharge of oil-laden air, mitigate the ecological impact of turbomachines, reduce oil consumption and limit oil tank filling operations, it is important to provide degassers that allow the separation of the oil from the air before venting the air to the outside of the turbomachine.

In known manner, such a degasser comprises at least one chamber for centrifugal separation of the air/oil mixture forming at least one air circulation vein arranged around a hollow shaft and delimited by an external annular wall and an internal annular wall. The degasser also comprises an axial inlet for supplying the enclosure with the air/oil mixture, at least one radial oil outlet provided in the external wall and an oil-free air outlet provided in the internal annular wall or between the inner and outer annular walls. Thus, during the rotation of the degasser, obtained conventionally by means of a pinion of the accessory box or the reducer, the oil is naturally driven by centrifugal force towards the outlet(s) of spare oil(s) on the periphery of the degasser. The oil-free air is evacuated to the outside of the degasser via the hollow shaft and then discharged out of the turbomachine via a ventilation duct leading to an orifice in the nozzle. There are also radial-centrifugal degassers.

Some deaerators, such as those described in applications FR-A1-3 064 304, FR-A1-3 071 418 and FR-A1-3 083 570, also include filters arranged in the enclosure of the deaerator to improve capture drops of oil and thus promote the de-oiling of the mixture. Indeed, the filters increase the contact surface available and therefore improve the probability that a drop of oil transported by the mixing flow will be attached to the wall. These filters are generally made up of an alveolar structure of the foam or metal mesh type.

Despite the presence of these filters, oil residues may be present in the air evacuated from the degasser to the exhaust nozzle and generate traces on the aircraft and emissions of unburnt hydrocarbons.

Moreover, the efficiency of the degassers also depends on their dynamic sealing devices which are generally replaceable elements in line (“ Line Replacable Unit ”). These elements have a limited lifetime which can vary from a few tens of hours if they are mounted defectively to a thousand hours or even an entire period between two overhauls if they are mounted correctly. Any failure of these sealing devices can lead to a loss of efficiency of the degasser. The air expelled from the turbomachine via the exhaust nozzle is then loaded with drops of oil. These polluting emissions lead to the appearance of traces in the exhaust nozzle and possibly on the tail booms in the case of helicopter turbine engines.

In addition, some turbomachines operate on a recovered cycle principle in which at least one heat exchanger is arranged at the outlet of the exhaust nozzle in order to use the temperature of the exhaust gases to preheat the air compressed by the compressor or compressors before it burns in the combustion chamber. In order to optimize the layout of the heat exchanger and the degasser on a turbomachine, the exhaust air outlet of the degasser is located upstream of the heat exchanger. However, the presence of oil residues in the air exiting through the orifice risks clogging the inlet of the heat exchanger, or even leading to its clogging in the exhaust nozzle. Such a situation presents risks relating to the safety and proper operation of a turbine engine.

In addition, some turbomachines or their equipment have systems for draining fluids, such as oil or fuel. These drains are sometimes introduced into the nozzle to be burned more or less efficiently. This return to the drain nozzle can also constitute a source of pollution comparable to oil leaks from a degassing system.

Objectives of the invention

The object of the present invention is to overcome this drawback by proposing a nozzle for an aircraft turbomachine allowing the treatment of the oil residues present in the filtered air and evacuated by the degasser, or the oil or fuel residues of the drains from the turbomachine or its equipment.

To this end, the invention relates to a nozzle for an aircraft turbomachine, in particular a helicopter, comprising an annular wall comprising an orifice for discharging an air flow likely to comprise oil or fuel.

According to the invention, said annular wall comprises an internal face on which is fixed a catalytic converter, said catalytic converter being configured to filter at least part of said air flow to treat said oil or fuel residues.

Thus, thanks to the invention, the oil residues present in the flow of air evacuated from the deaerator in the nozzle are captured and treated by the catalytic converter instead of risking clogging an exchanger or leaving black traces in the nozzle. In addition, the temperature of the nozzle, including when the turbomachine is operating at idle speed, makes it possible to trigger the catalysis process allowing the treatment of oil residues in the catalytic converter in an autonomous manner.

In a similar way, the catalytic converter can also be used to treat the oil and fuel residues discharged into the nozzle by the drainage systems of the turbomachine or its equipment.

The nozzle according to the invention may also have one or more of the following characteristics, taken alone or in combination with each other:

• the catalytic converter may be formed of a casing comprising at least one inlet face for said part of the air flow and at least one outlet face for a flow of filtered air,
• the catalytic converter may comprise at least one catalytic element arranged between said at least one inlet face and said at least one outlet face,
• the catalytic converter can be arranged directly above the said evacuation orifice,
• the catalytic converter can be arranged downstream of said discharge orifice with respect to a direction of flow of said flow,
• the catalytic converter may also comprise a collection element forming a plate arranged directly above said discharge orifice and fixed to the housing by an upstream edge,
• the catalytic converter can have a flat shape and is arranged parallel to the internal face of said annular wall,
• said at least one catalytic element of the catalytic converter can be made of one of the following materials: Palladium, Platinum, Rhodium,
• the catalytic converter can be attached to the annular wall by brazing, welding, riveting or bolting, and
• the catalytic converter has a bypass zone configured to allow the evacuation of oil or fuel residues in the event of clogging of the catalytic element.

The present invention also relates to an aircraft turbomachine, in particular a helicopter, comprising at least one nozzle as described above.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

there shows a partial schematic perspective view of a nozzle according to one embodiment;

there shows a partial longitudinal schematic view of a nozzle according to one embodiment and comprising a heat exchanger;

there illustrates a partial schematic perspective view of a catalytic converter attached to the nozzle according to one embodiment;

there is a partial schematic perspective view of a catalytic converter attached to the nozzle according to another embodiment; there is a partial schematic view in longitudinal section of the catalytic converter fixed to the nozzle according to the other embodiment;

there is a partial schematic perspective view of the nozzle according to a first embodiment;

there is an enlarged schematic perspective view of the catalytic converter of the nozzle according to the first embodiment;

there shows a partial longitudinal schematic view of a nozzle according to the first embodiment;

there is a partial schematic perspective view of the nozzle according to a variant of the first embodiment;

there is an enlarged schematic perspective view of the catalytic converter of the nozzle according to the variant of the first embodiment;

there shows a partial longitudinal schematic view of a nozzle according to a second embodiment;

there is a schematic view of a structure of a catalytic element of the catalytic converter according to one embodiment;

there is a schematic view of a nozzle according to a third embodiment; And

there is a schematic view of a nozzle according to a fourth embodiment.

Detailed description of the invention

In the following description, the invention applies generally to a nozzle 1 for an aircraft turbine engine, in particular a helicopter or airplane, as previously described in the technical background of the present asked. A turbomachine can be a turboshaft engine, a turbojet or a turboprop.

By convention, in the present application, the terms “upstream” and “downstream”, and “internal/central” and “external/peripheral” are used in reference to a positioning with respect to a flow axis of the exhaust gases coming out of a turbine 2 of the turbomachine. Thus, a cylinder extending along the X-X axis has an inner face turned towards the X-X axis and an outer face, opposite its inner face. “Longitudinal” or “longitudinally” means any direction parallel to the X-X axis, and “transversely” or “transverse” means any direction perpendicular to the X-X axis.

The nozzle 1 is arranged downstream of the turbine or turbines 2 of the turbomachine so as to channel the exhaust gases, as shown in the . The nozzle 1 is provided with a central body 3 (hereinafter "body 3") and a peripheral annular wall 4 (hereinafter "wall 4") mounted coaxially around the body 3. The nozzle 1 comprises also a plurality of support arms 5 extending transversely between the body 3 and the wall 4. Each of the support arms 5 is fixed, by a radially internal end 5A, to an external surface 3A of the body 3 and, by the opposite end 5B radially external, to an internal surface 4A of the wall 4 so that the space between the wall 4 and the body 3, in the transverse direction, is constant. This space forms a channel through which the gases from the turbine(s) 2 escape.

In a preferred embodiment, the wall 4 comprises an evacuation orifice 6 (hereinafter “orifice 6”) which passes right through it in the transverse direction. By way of example, it has a circular section although it may have a different section. The orifice 6 is arranged between the fixings of two adjacent support arms 5 . As represented in FIGS. 5A, 7A and 11, the orifice 6 is connected to one end 7A of an outlet pipe 7 of a degasser (not represented) or of a drainage system so as to evacuate, in the nozzle 1, an air flow. The circulation of the exhaust gases in the nozzle 1 generates a transverse pressure and a longitudinal pressure so that at least part of the flow of air leaving the orifice 6 is evacuated along the internal surface 4A of the wall 4, in a direction of flow represented by the arrow F. This direction of flow F is substantially parallel to the longitudinal axis XX. The passage of this part of the air flow over the internal surface 4A of the wall 4 forms a flow path. The high temperature present in the nozzle 1 can also cause evaporation of another part of the air flow evacuated by the orifice 6 in the exhaust gases.

Despite the filtering of the air/oil mixtures in the degasser, air/oil or air/fuel in a drainage system, the flow of air evacuated by the orifice 6 is likely to include oil or fuel residues which can generate corrosive black traces from the orifice 6 to a downstream end 1A of the nozzle 1. The presence of these residues in the air flow can also lead to the clogging of a heat exchanger 15 arranged in the nozzle 1, downstream of the orifice 6 as shown in the .

In a preferred embodiment, the wall 4 also comprises a catalytic converter 8. This catalytic converter 8 is fixed on the internal surface 4A of the wall 4. The catalytic converter 8 is fixed by brazing although it can be fixed by any other mechanical assembly technique. In a variant, the fixing of the catalytic converter 8 can be carried out by welding. In another variant, the fixing of the catalytic converter 8 can be carried out by plates 16 riveted in the wall 4, as shown in Figure 3. Alternatively, the fixing is carried out by rivets or bolts 17 crossing both the housing 9 and the wall 4 of the nozzle, as shown in Figures 4A and 4B.

In a preferred embodiment, the catalytic converter 8 filters the part of the air flow evacuated by the orifice 6 and circulating along the flow path in the direction of flow F. By filtering a part of the flow d air, the catalytic converter 8 treats the oil or fuel residues that it comprises by catalytic reaction. In the context of the present invention, the term "treating" the oil or fuel residues means the action of capturing and degrading these residues into non-polluting residues inside the catalytic converter 8.

As shown in Figures 5B and 7B, the catalytic converter 8 is formed of a housing 9 which comprises a framework 10 and a plurality of faces 12 porous. The framework 10 can be of rectangular section so that the box 9 is of parallelepiped shape. The framework 10 comprises peripheral ends 11 by which the catalytic converter 8 is fixed to the internal surface 4A of the wall 4. Among the plurality of faces 12, the casing 9 comprises at least one inlet face 12A by which part of the air flow penetrates inside the catalytic converter 8. The housing 9 also comprises at least one outlet face 12B through which a flow of filtered air can exit.

As shown in Figures 5B and 7B, the housing 9 may also include side faces 12C arranged along the X-X axis in a plane perpendicular to the internal surface 4A. The catalytic converter 8 comprises, between the inlet face(s) 12A and the outlet face(s) 12B, at least one catalytic element 13. From a certain temperature, the catalytic element 13 initiates a catalytic reaction of the residues oil or fuel present in the part of the flow entered by the entry face 12A. These oil or fuel residues are captured and degraded inside the catalytic element 13 so that the flow of air exiting through the exit face(s) 12B is a flow of filtered air without residues of oil or fuel.

The activation temperature of the catalytic element 13 is comparable to the temperature present in the nozzle 1 when the turbomachine is in operation, including at idle speed. Such an activation temperature can be of the order of 400 degrees Celsius. The catalytic element 13 can in particular be made from a metal or ceramic substrate with additives in a material capable of promoting the oxidation of hydrocarbons. By way of example, these materials can be Palladium, Platinum, Rhodium. Other materials or alloys can also be used. The catalytic element 13 may have a honeycomb structure (for example, of the NIDA type), as shown in the . Alternatively, it may have a more complex shape such as a concentric stack of structured sheets, for example EMITEC® catalysts.

Furthermore, the catalytic converter 8 comprises a bypass zone also called bypass. This bypass zone is configured to allow the evacuation of oil or fuel residues in the event of clogging of the catalytic element 13.

In a first embodiment, the catalytic converter 8 is arranged downstream of the orifice 6 with respect to the direction of flow F of the air flow leaving the pipe 7. As shown in Figures 5A, 5B and 6, the casing 9 is fixed against the wall 4 by the peripheral ends 11 of the frame 10 so that an outer face of the casing 9 is in contact with the inner surface 4A. The inlet face 12A of the casing 9 is arranged in a plane transverse to the internal surface 4A of the wall 4 and perpendicular to the direction of flow F. The casing 9 also comprises at least one outlet face 12B which is arranged parallel to the inlet face 12A downstream of the catalytic converter 8. An internal face 12D parallel to the internal surface 4A can also represent an outlet face 12B for the flow of filtered air, just like the side faces 12C. The flow of air evacuated by the orifice 6 is pressed against the internal surface 4A by the pressure exerted during the passage of the gases in the exhaust channel. Part of this airflow flows along the inner surface 4A until it enters the catalytic converter 8 through the inlet face 12A. The oil or fuel residues present in this part of the air flow are treated in the catalytic element 13 whose activation is triggered by the temperature present in the nozzle 1. The air flow filtered from the residues of oil or fuel is evacuated via the outlet face(s) 12B in the direction of flow.

According to a variant to this first embodiment, the catalytic converter 8 also comprises a collection element forming a plate 14 arranged plumb with the orifice 6. In the present invention, the expression “plumb” means the arrangement of an element opposite the orifice 6 and inside the nozzle 1 in the transverse direction. As shown in Figures 7A and 7B, the wafer 14 has a flat shape. It is arranged parallel to the internal surface 4A and spaced from the orifice 6. By way of example, the value of this space is approximately a few millimeters. Plate 14 has an upstream end 14A whose shape represents an arc of a circle similar to part of orifice 6 and arranged plumb with an upstream edge of orifice 6. Plate 14 also has an end 14B downstream which is fixed to an upstream edge of the frame 10, the catalytic converter 8 is arranged in the extension of the wafer 14 in the direction of flow F. The end 14B of the wafer 14 can also have a shape in arc. Plate 14 collects the part of the air flow flowing in the flow direction F and the other part of the evaporated air flow. The width of the plate 14 is comparable to the space between the side faces 12C of the housing 9 so that the parts of the air flow collected enter directly into the catalytic converter 8 through the inlet face 12A without risking clogging the port 6.

According to a second embodiment, and as shown in the , the catalytic converter 8 is arranged directly above the orifice 6. A part of the air fluid comprising oil or fuel residues enters the catalytic converter 8 through the inlet face 12A which is then arranged opposite the orifice 6, in a plane locally parallel to the internal surface 4A. In this third embodiment, the arrangement of the catalytic converter 8 has the advantage of capturing the vast majority of the flow of air leaving the outlet pipe 7. In order to prevent the risk of clogging of the orifice 6 by the residues of oil or fuel present in the air flow, the nozzle 1 can also include a monitoring unit (not shown). Such a monitoring unit is configured to monitor the clogging of the catalytic element 13 from pressure data in the piping. The monitoring unit may include elements offset with respect to the nozzle 1.

According to a third embodiment, the catalytic converter 8 has a flat shape. As shown on the , it can be arranged parallel to the wall 4 downstream of the orifice 6 with respect to the flow direction F of the air flow. The catalytic converter 8 has a surface shape fixed against the internal surface 4A of the wall 4 and comprises a single face 12 which represents both the inlet face 12A of part of the air flow and the outlet face 12B filtered airflow. Catalytic element 13 is arranged between face 12 and internal surface 4A and also has a flat shape. This embodiment aims mainly to oxidize the oil or fuel residues flowing into the nozzle 1.

According to a fourth embodiment, the nozzle 1 may include a suction element which generates a depression against the wall 4 so as to force the flow of the air flow exiting the orifice 6 towards the face or faces of inlet 12A of the catalytic converter 8 as shown in FIG. 11. The suction element can be fixed to the internal surface 4A or it can be part of the wall 4 of the nozzle 1. suction uses the pre-existing pressure difference between the wall 4 of the nozzle 1 and the ejector of a secondary flow. As shown on the , when the transverse pressure generated by the exhaust gases on one side of the wall 4 along the direction P2 is greater than the transverse pressure generated by the ejection of the secondary flow on the opposite side of the wall 4 along the direction P1, local suction causes the air flow to enter the catalytic converter 8.

The nozzle 1 according to the invention has the particular advantage of locally filtering the flow of air evacuated in the degasser and of treating the oil or fuel residues by a catalytic reaction triggered by the temperature already present in the nozzle 1. It allows to treat the residues of the oil and fuel drainage systems of the turbomachine or its equipment

Furthermore, the presence of a local catalytic converter 8 makes it possible to capture all of the oil or fuel residues resulting from the air flows flowing along the internal surface 4A of the wall 4 as well as the residues of oil or fuel possibly evaporated in the exhaust gases.

Claims (11)

Nozzle for an aircraft turbomachine, comprising an annular wall (4) comprising an orifice (6) for discharging an air flow likely to comprise oil or fuel residues,
characterized in that said annular wall (4) has an internal face (4A) on which is fixed a catalytic converter (8), said catalytic converter (8) being configured to filter at least a part of said air flow to treat said oil or fuel residues. Nozzle according to the preceding claim,
characterized in that the catalytic converter (8) is formed of a casing (9) comprising at least one inlet face (12A) of said part of the air flow and at least one outlet face (12B) of a flow of filtered air. Nozzle according to the preceding claim,
characterized in that the catalytic converter (8) comprises at least one catalytic element (13) arranged between the said at least one inlet face (12A) and the said at least one outlet face (12B). Nozzle according to any one of the preceding claims,
characterized in that the catalytic converter (8) is arranged directly above said discharge orifice (6). Nozzle according to any one of claims 1 to 3,
characterized in that the catalytic converter (8) is arranged downstream of said discharge orifice (6) with respect to a direction of flow (F) of said flow. Nozzle according to the preceding claim,
characterized in that the catalytic converter (8) also comprises a collecting element forming a plate (14) arranged directly above the said evacuation orifice (6) and fixed to the casing (9) by an upstream edge. Nozzle according to claim 1,
characterized in that the catalytic converter (8) has a flat shape and is arranged parallel to the internal face (4A) of the said annular wall (4). Nozzle according to any one of the preceding claims,
characterized in that said at least one catalytic element (13) of the catalytic converter (8) is made of one of the following materials: Palladium, Platinum, Rhodium. Nozzle according to any one of the preceding claims,
characterized in that the catalytic converter (8) is attached to the annular wall (4) by brazing, welding, riveting or bolting. Nozzle according to any one of the preceding claims,
characterized in that the catalytic converter (8) comprises a bypass zone configured to allow evacuation of said oil or fuel residues in the event of clogging of said catalytic element (13). Aircraft turbomachine, in particular a helicopter, comprising at least one nozzle (1) according to any one of the preceding claims.