Anti-icing system for an air intake duct for a compressor of an aircraft turbomachine and anti-icing method for an air intake duct for a compressor of an aircraft turbomachine

Abstract

ANTI-ICING SYSTEM FOR AN AIR LINE FOR A COMPRESSOR FOR AN AIRCRAFT TURBOMACHINE AND ANTI-ICING METHOD FOR AN AIR LINE FOR A COMPRESSOR FOR AN AIRCRAFT TURBOMACHINE Anti-icing system for an air line for a compressor for an aircraft turbomachine comprising: an outer wall (30) externally delimiting the air line, comprising an air reinjection slot (40) and an air sampling slot (50), the air reinjection slot (40) being upstream of the air sampling slot (50); An anti-icing device, said anti-icing device comprising a pipe (60) connecting the air intake slot (50) and the air reinjection slot (40) so as to carry the air drawn in by the air intake slot (50) to the air reinjection slot (40); a valve (70) positioned in the pipe (60) to interrupt the airflow inside the pipe. Figure to be published with the abbreviation: Figure 1

Description

Title of the invention: ANTI-ICING SYSTEM FOR AN AIR VENT FOR A COMPRESSOR FOR AN AIRCRAFT TURBOMACHINE AND METHOD FOR ANTI-ICING AN AIR VENT FOR A COMPRESSOR FOR AN AIRCRAFT TURBOMACHINE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of aeronautics and particularly to the field of anti-icing devices and methods for a turbomachine compressor.

[0002] The invention relates to an anti-icing system for an air stream for a compressor for an aircraft turbomachine and an aircraft turbomachine comprising this anti-icing system. The invention also relates to an anti-icing method for an air stream for a compressor of a turbomachine comprising an anti-icing system according to the first aspect of the invention. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] An aeronautical turbomachine conventionally comprises a compressor, a combustion chamber and a turbine. The role of the turbine is to ensure the rotational drive of the compressor by taking part of the pressure energy from the hot gases leaving the combustion chamber and transforming it into mechanical energy.

[0004] A compressor consists of a rotating part, a rotor comprising an axis of rotation, a fixed part, the stator, and a casing, the casing and the stator being integral with each other. The rotor comprises a drum consisting of an assembly of several discs on which rotating blades are circumferentially fixed. The stator consists of a plurality of fixed blades (because they do not rotate around the axis of rotation of the rotor but can be mobile in rotation along their own axis) fixed circumferentially on the casing or on shells. Each row of fixed blades of the stator, called rectifiers, constitutes a rectifier. A row of moving blades and a row of fixed blades form a compressor stage.

[0005] When an aircraft comprising a turbomachine passes through a cloud of water droplets or ice crystals under certain flight conditions, the latter can form a layer of ice called frost in the turbomachine and thus cause degradations such as a reduction in aerodynamic performance, mechanical damage, a loss of thrust.

[0006] The accretion of ice in conditions of presence of clouds of ice crystals at high altitude does not cause the formation of frost. Indeed, under these conditions the ice crystals only bounce and break on impact with the walls of the turbomachine. Icing therefore requires the presence of liquid water, for example near a heat source.

[0007] For example, ice crystals will partially melt with the heating of the flow caused by compression and generate these icing conditions.

[0008] The frost accretion process can be schematized as follows: - ingestion of ice crystals from the turbomachine; the crystals bounce off the walls of the turbomachine and fragment; - heating and partial melting of crystals near a compressor wall; - adhesion to the compressor walls and formation of a liquid film in contact with the hot wall; - evaporation of the film and impact of new crystals with heat removal from the wall; - formation of a layer of ice when the wall temperature reaches 0°C.

[0009] There are defrosting technologies to remove frost accumulated on solid walls, and anti-frosting technologies to prevent ice formation.

[0010] Among the existing defrosting and anti-frosting solutions, the following examples can be cited: - defrosting and anti-frosting of certain parts such as the air intake lips and nacelle or the cone; in this case a flow of hot air circulates inside the turbomachine without coming into contact with the air veins; - electric defrosting and anti-frosting; - draining or purging of air and ice flow via the VBV doors of the acronym “Variable bleed valve”.

[0011] However, there is currently no anti-icing system which is active only when the conditions for frost formation are met and which can act selectively on the portions of the walls on which frost formation is favored, without disturbing the air flow in the main air stream. Summary of the invention

[0012] The invention provides a solution to the problems mentioned above by proposing an anti-icing system capable of taking hot air circulating in an air stream of a turbomachine to reinject it further upstream, so as to obtain an anti-icing effect on the external wall of the compressor. The reinjection of hot air into the air stream only occurs when frost accretion conditions are met. In addition, reinjection is carried out using a suitably chosen injection angle, so as not to disturb the main flow in the air stream during operation of the anti-icing system.

[0013] A first aspect of the invention relates to an anti-icing system for an air stream for a compressor for an aircraft turbomachine comprising: • an outer wall formed of at least one outer shell, externally delimiting an air stream, the outer shell comprising an air reinjection slot and the outer wall further comprising an air sampling slot, the air reinjection slot being upstream of the air sampling slot; • an anti-icing device, said anti-icing device comprising: - a pipe connecting the air sampling slot and the air reinjection slot so as to bring the air sampled by the air sampling slot to the air reinjection slot, said pipe having an end portion extending from the air reinjection slot, the angle between a tangent of the shell of the outer wall at the air reinjection slot and the end portion of the pipe being between 10° and 30°; - a valve positioned in the pipe to interrupt the flow of air inside the pipe.

[0014] An air sampling or reinjection slot is understood to mean an opening in the outer wall delimiting the air stream and allowing the passage of air.

[0015] The partial melting of the ice crystals forms a solid / liquid mixture which adheres to the wall of the compressor, namely the outer shell. For example, this situation is observed in the part of the duct forming the air stream, in the shape of a swan neck between the low pressure compressor and the high pressure compressor of a double-spool - double-flow turbomachine.

[0016] Since the air sampling slot is located downstream of the reinjection slot, the sampled air has a higher temperature than the air circulating in the upstream part of the air stream. It is therefore possible to use the warmer air to prevent the formation of frost on the outer shell.

[0017] The angle between the terminal part or cavity of the pipeline and the tangent of the outer shell at the level of the reinjection slot is chosen to allow the outer shell to be heated without generating a disruptive effect with respect to the main flow in the vein.

[0018] The valve allows the reinjection of hot air only when needed, namely if the frost accretion conditions are met. Furthermore, the inventors have checked that the presence of the air injection and sampling slots does not disturb the main flow in the air stream.

[0019] According to one embodiment, the outer shell has a circular section along a section plane normal to an axis of rotation of the turbomachine. According to one example, the shell comprises a plurality of air reinjection slots distributed around the x axis, and in that the duct comprises a circular portion surrounding the slots to supply them

[0020] According to another example, the shell comprises a plurality of air reinjection slots distributed around the x axis, the wall further comprises a plurality of air sampling slots distributed around the x axis, each located downstream of an air reinjection slot and in that the defrosting device comprises a plurality of pipes and valves each positioned in a pipe to supply one or more air reinjection slots via an air sampling slot.

[0021] According to one embodiment, the wall comprises an external casing of the high-pressure compressor and in that the external casing comprises a plurality of slots around the axis x of rotation to supply and pressurize the supply channel.

[0022] According to one embodiment, the air stream is delimited internally by a turbomachine hub.

[0023] According to one embodiment, the outer wall comprises a first part and a second part, the first part comprising the outer shell and extending between a low-pressure compressor outlet in the air stream and a high-pressure compressor inlet in the air stream and the second part extending between a high-pressure compressor inlet in the air stream and a high-pressure compressor outlet in the air stream, the first part comprising the air reinjection slot and the second part comprising the air sampling slot. According to one example, the second part extends from the outer shell forming the first part. According to another example, the wall comprises at least one intermediate part between the two parts. According to one example, the outer shell of the wall comprises the first and second parts. According to another example, the second part is formed by a compressor casing.

[0024] Advantageously, this embodiment makes it possible to take hot air from the high-pressure compressor. This ensures a temperature difference of between 20K and 30K between the reinjected air and the air flowing in the air stream at the reinjection slot.

[0025] According to an example of this embodiment, an axial projection distance measured axially between the low pressure compressor outlet and the air reinjection slot is between 0.1L and 0.3L, L being a projection distance axial measured axially between the low pressure compressor outlet and the high pressure compressor inlet.

[0026] According to one example, the air reinjection slot is located upstream of the VBV doors. An air discharge system of a turbomachine comprises a shutter t, commonly called a VBV door. Such a VBV door is pivotally mounted about a pivot axis on a portion of the inter-compressor casing so that the VBV door is movable between a closed position, in which the VBV door closes the orifice by masking the latter, and an open position, in which the VBV door uncovers all or part of the orifice and thus allows air to circulate through the orifice.

[0027] According to one embodiment, the first part of the outer wall has a swan neck shape.

[0028] According to one embodiment, the pipe is external to the air stream.

[0029] A second aspect of the invention relates to an aircraft turbomachine comprising a fan, a low pressure compressor, a high pressure compressor, an air stream passing through the low pressure compressor and the high pressure compressor and an anti-icing system according to the first aspect of the invention.

[0030] A third aspect of the invention relates to an anti-icing method for a compressor of a turbomachine comprising an anti-icing system according to the first aspect of the invention, said anti-icing method comprising the following steps: • Determine whether conditions for ice accretion on the outer shell of the outer wall are met by comparing a temperature measurement in the air stream to a threshold value; • If the conditions for ice accretion on the outer shell of the outer wall are met, open the valve positioned between the air sampling slot and the air reinjection slot, so as to reinject the air sampled by the sampling slot into the air stream through the air reinjection slot, the air reinjected by the air reinjection slot being warmer than the air entering the air stream.

[0031] Thanks to the method according to the third aspect of the invention, the reinjection of air is carried out only in the event of a risk of frost forming on the outer shell externally delimiting the air stream.

[0032] According to one embodiment, the method according to the third aspect of the invention further comprises a step of sending an icing risk signal to an operator, the opening of the valve being triggered by the operator.

[0033] According to one embodiment, the method according to the third aspect of the invention comprises a step of sending an icing risk signal to a system digital regulation of a turbomachine engine, the opening of the valve being triggered by the digital regulation system of a turbomachine engine.

[0034] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0035] Other advantages and characteristics of the invention will appear on reading the following description, illustrated by the figures in which:

[0036] [Fig.l] schematically illustrates an embodiment of the anti-icing system according to the first aspect of the invention;

[0037] [Fig.2] schematically illustrates a second embodiment of the anti-icing system according to the first aspect of the invention;

[0038] [Fig.3] schematically illustrates the reinjection angle and the position of the reinjection slot for an intercompressor swan-neck shaped air stream;

[0039] [Fig.4] illustrates a flowchart of the anti-icing method according to the third aspect of the invention.

[0040] [Fig.5a] and [Fig.5b] illustrate the temperature inside the air stream respectively without and with the anti-icing system according to the first aspect of the invention. DETAILED DESCRIPTION

[0041] An exemplary embodiment of an anti-icing system for an air stream for an aircraft turbomachine according to the first aspect of the invention is described below. This example illustrates the characteristics and advantages of the invention.

[0042] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0043] For the understanding of the invention, the radial R, tangential T and axial A orientations will be adopted according to the reference RTA indicated in the figures, the tangent T and axial A axes of which extend in a horizontal plane according to the orientation in the figures. The axial axis A is parallel to an axis of rotation X of an aircraft turbomachine comprising the anti-icing system according to the first aspect of the invention.

[0044] In the description, the terms “upstream” and “downstream” are defined in relation to the direction of air flow from the air inlet into the turbomachine to the air outlet from the turbomachine.

[0045] [Fig.l] illustrates an embodiment of the anti-icing system 1 according to the first aspect of the invention. According to the embodiment illustrated in [Fig.l], the anti-icing system 1 comprises an outer wall 30 externally delimiting an air stream. The outer wall 30 may be in one or more parts, including at least one shell. The wall comprises an air sampling slot 50 and a reinjection slot air 40 at the level of the ferrule. The two slots are connected by a pipe 60. The air reinjection slot 40 is located upstream of the air reinjection slot 50.

[0046] Thanks to this arrangement of the slots 40 and 50 connected by the pipe 60, it is possible to reinject air having a higher temperature than the air circulating in the air stream at the level of the reinjection slot 40, so as to eliminate the risk of frost forming on the shell of the outer wall 30.

[0047] The pipe 60 has an end portion 65 comprising the cavity extending from the air reinjection slot 40. The end portion 65 has walls inclined relative to the shell of the outer wall 30 so as to form with the tangent to the shell of the outer wall 30 an angle of between 10° and 30°. This angle allows heating of the entire shell of the outer wall 30 without generating a disruptive effect relative to the main flow in the vein.

[0048] The anti-icing system according to the embodiment illustrated in [Fig.l] further comprises a valve 70 positioned in the duct 60 and making it possible to interrupt the air flow inside the duct 60. Thanks to the valve 70, the hot air is reintroduced into the air stream only if the conditions for accretion of the ice on the shell of the outer wall 30 are met.

[0049] In the example illustrated in [Fig.l], the air stream is further delimited internally by a turbomachine hub 2.

[0050] According to the embodiment illustrated in [Fig.l], the air stream has a low pressure compressor inlet and outlet and a high pressure inlet and outlet and an intercompressor swan neck shape, namely a swan neck connecting an air supply channel, from the inlet to the outlet of the high pressure compressor and from the inlet to the outlet of the low pressure compressor of the turbomachine. The outer wall 30 then has a first part 11, comprising at least the previously described shell and a second part 12, comprising a high pressure compressor casing. The first part 11 extends between the low pressure compressor outlet and the high pressure compressor inlet. The second part 12 extends between the high pressure compressor inlet and the high pressure compressor outlet. The first part 11 comprises the air reinjection slot 40. The second part comprises the air sampling slot 50.

[0051] For example, the temperature difference between the air circulating in the swan neck at the reinjection slot 40 and the reinjected air is approximately 30 K. Under conditions favorable to the accretion of ice, the air leaving the low-pressure compressor has a temperature of between -10°C and +5°C.

[0052] The pipe 60 may further comprise the terminal portion 65 an initial part 67, extending from the sampling slot 50 having a larger section than an intermediate part of the pipe 60 connecting the initial part to the portion terminal 65. Preferably, the casing of the high pressure compressor comprises a plurality of slots, only one of which is shown for pressurizing and supplying the pipe 60. The pipe 60 can thus comprise one or more initial parts 67 each connected to at least one air sampling slot 50 at the valve 70.

[0053] In the example illustrated in [Fig. 1], the valve 70 is positioned close to the air bleed slot 50, that is to say closer to the air bleed slot 50 than to the air reinjection slot 40. In this case, in this example the valve 70 is located at the end of the intermediate part connected to the initial part. The location of the valve 70 may depend on the volume available in the turbomachine. In this example, the advantage of having the valve 70 closer to the air bleed slot 50 than to the air reinjection slot 40 is that the air in the initial part is hotter than in the opposite case shown in [Fig. 2] explained below. The fact that the air is warmer makes it possible to reduce the volume of air to be supplied into the pipeline when the valve is closed and to maintain greater pressure on the valve 70 in the closed state so that when it opens it produces a flow of pressurized air.

[0054] [Fig. 2] illustrates a second embodiment of the anti-icing device according to the first aspect of the invention identical to the first embodiment except that the valve 70 is positioned closer to the air reinjection slot 40 than to the air sampling slot 50, for example at the end of the intermediate part connected to the terminal portion 65.

[0055] In this example, the additional benefit of having the pump close to the air reinjection slot 40 is to have a reactivity of the air flow when the valve 70 is opened on the air reinjection slot 40.

[0056] According to another embodiment, the pipe could have a constant section between the terminal portion 65 and the air sampling slot 50.

[0057] [Fig. 3] illustrates a portion of the air stream representing in particular the first portion 11, in this case the shell of the outer wall 30 according to an example of one of the embodiments. According to this example, the first portion 11 extends between the outlet of a low-pressure compressor 111 and the inlet of a high-pressure compressor 112. In other words, the first portion 11 of the outer wall 30 forms the initial portion of an intercompressor swan neck. The reinjection slot 40 is positioned in the upstream portion of the swan neck, close to the slope inversion. For example, the axial distance x between the air reinjection slot 40 and the low-pressure compressor outlet 111 may be between 0.1 L and 0.3 L, L being the axial distance measured between the low-pressure compressor outlet 111 and the high-pressure compressor inlet 112.

[0058] [Fig. 3] further illustrates the angle alpha formed between the terminal portion 65 of the pipe 60 and the tangent 100 to the shell of the outer wall 30 at the level of the reinjection slot 40. The tangent 100 is identical to the slope of the air stream relative to the axial direction A at the level of the reinjection slot 40.

[0059] [Fig. 4] illustrates a flowchart of an embodiment of the anti-icing method 500 according to the third aspect of the invention. The method 500 comprises, according to the embodiment illustrated in [Fig. 4], a step 510 of determining whether conditions for ice accretion on the shell of the outer wall 30 are met. For example, this step may comprise a comparison of a temperature measurement in the air stream with a threshold value. According to one embodiment, step 510 further comprises a measurement of the atmospheric pressure.

[0060] In the example illustrated in [Fig.4], the method 500 further comprises a step 520 of sending, if the ice accretion conditions are met, an icing risk signal to an operator or to a digital regulation system of a turbomachine engine.

[0061] If the conditions for ice accretion on the shell of the outer wall 30 are met, the method 500 comprises a step of opening the valve 70 positioned between the air sampling slot 50 and the air reinjection slot 40. The opening of the valve makes it possible to reinject warmer air at the level of the reinjection slot 40 in the upstream part of the swan neck, which eliminates the risk of ice accretion on the outer shell.

[0062] According to one embodiment, the flow rate of hot air reinjected through the reinjection slot 40 is between 1% and 3% of the overall flow rate of the air stream in the swan neck.

[0063] The opening of the valve 70 can, if necessary, be triggered by an operator having received a signal of risk of icing. Alternatively, the valve can be opened by a digital regulation system of a turbomachine engine, for example a Fadec type system.

[0064] It is important to note that the valve 70 is closed for the majority of the aircraft's flight time; it will only be open at operating points at risk from accretion.

[0065] [Fig.5a] illustrates the temperature profile inside the air stream in the absence of the device 1 according to the first aspect of the invention or when the valve 70 is closed. It is obvious how the temperature of the air stream is close to 0°C near the shell of the outer wall 30. These temperature values, the presence of a slope inversion in the shape of the air stream and the presence of irregularities due to technological integrations such as openings or junctions can promote the accretion of ice on the shell of the outer wall 30.

[0066] [Fig.5b] illustrates the temperature profile inside the air stream in the presence of the device 1 according to the first aspect of the invention, when the valve 70 is open. In this case the temperature of the air near the outer shell is of the order of 20 to 30°C, which prevents the formation of ice without disturbing the flow of air in the stream.

Claims

Claims

1. Anti-icing system for an air stream for a compressor for an aircraft turbomachine comprising: - an outer wall (30) formed of at least one outer shell externally delimiting an air stream, the outer shell comprising an air reinjection slot (40) and the outer wall (30) further comprising an air sampling slot (50), the air reinjection slot (40) being upstream of the air sampling slot (50);- an anti-icing device, said anti-icing device comprising: • a pipe (60) connecting the air sampling slot (50) and the air reinjection slot (40) so as to bring the air sampled by the air sampling slot (50) to the air reinjection slot (40), said pipe (60) having an end portion (65) extending from the air reinjection slot (40), the angle between a tangent (100) of the shell of the outer wall (30) at the air reinjection slot (40) and the end portion (65) of the pipe (60) being between 10° and 30°; • a valve (70) positioned in the pipe (60) to interrupt the air flow inside the pipe.;

2. Anti-icing system (1) according to one of the preceding claims wherein the outer wall (30) comprises a first (11) and a second part (12), the first part (11) comprising the outer shell and extending between a low pressure compressor outlet in the air stream and a high pressure compressor inlet in the air stream and the second part (12) extending between a high pressure compressor inlet in the air stream and a high pressure compressor outlet in the air stream, the first part (11) comprising the air reinjection slot (40) and the second part (12) comprising the air sampling slot (50).

3. Anti-icing system (1) according to the preceding claim in which an axial projection distance (x) measured axially between the low pressure compressor outlet and the air reinjection slot is between 0. IL and 0.3L, L being an axial projection distance measured axially between the low pressure compressor outlet and the high pressure compressor inlet.

4. An anti-icing system (1) according to claim 2 or claim 3, wherein the first portion (11) of the outer wall (30) has a swan neck shape.

5. Anti-icing system (1) according to one of the preceding claims in which the pipe (60) is external to the air stream.

6. Aircraft turbomachine comprising a fan, a low pressure compressor, a high pressure compressor, an air stream passing through the high pressure compressor and the low pressure compressor and an anti-icing system (1) according to one of the preceding claims.

7. Anti-icing method (500) of an air stream for a compressor of a turbomachine comprising an anti-icing system according to one of claims 1 to 5, said anti-icing method comprising the following steps: - Determining (510) whether conditions for ice accretion on the outer shell of the outer wall (30) are met by comparing a temperature measurement in the air stream with a threshold value; - If the conditions for ice accretion on the outer shell of the outer wall (30) are met, open (530) the valve positioned between the air sampling slot (70) (50) and the air reinjection slot (40), so as to reinject the air sampled by the sampling slot (50) into the air stream using the air reinjection slot (40), the air reinjected by the air reinjection slot (40) being warmer than the air entering the air stream.

8. Anti-icing method (500) according to the preceding claim comprising a step of sending (520) an icing risk signal to an operator, the opening of the valve (70) being triggered by the operator.

9. Anti-icing method (500) according to claim 7 comprising a step of sending (520) an icing risk signal to a system digital regulation of a turbomachine engine, the opening of the valve (70) being triggered by a digital regulation system of a turbomachine engine.

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