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 LINE FOR A COMPRESSOR An aircraft turbomachine and anti-icing method for an air duct 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 in a compressor for an aircraft turbomachine and to an aircraft turbomachine comprising this anti-icing system. The invention also relates to a method for anti-icing an air stream in 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 typically comprises a compressor, a combustion chamber, and a turbine. The role of the turbine is to drive the compressor in rotation by capturing some of the pressure energy from the hot gases exiting the combustion chamber and converting it into mechanical energy.

[0004] A compressor consists of a rotating part, a rotor comprising a rotational axis, a fixed part, the stator, and a casing, the housing and the stator being rigidly connected to each other. The rotor comprises a drum made up 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 rotor's axis of rotation but can rotate about their own axis) fixed circumferentially to the housing or to ferrules. Each row of fixed stator blades, called stator vanes, constitutes a stator. One row of rotating blades and one row of fixed blades form a compressor stage.

[0005] When an aircraft including 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 degradation such as a decrease in aerodynamic performance, mechanical damage, loss of thrust.

[0006] Ice accretion under conditions of high-altitude ice crystal clouds does not cause frost formation. Indeed, under these conditions, the ice crystals merely rebound and break upon impact with the turbomachine walls. Frost formation therefore requires the presence of liquid water, for example, near a heat source.

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

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

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

[0010] Among the existing defrosting and anti-icing solutions, the following examples can be cited: - de-icing and anti-icing of certain parts such as the air inlet 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 streams; - electric defrosting and anti-icing; - draining or purging of air and ice flow via the VBV doors, from the acronym "Variable bleed valve".

[0011] However, there is currently no anti-icing system that is active only when frost formation conditions are met and that can act selectively on the portions of the walls where frost formation is favored, without disrupting the airflow in the main air duct. Summary of the invention

[0012] The invention offers a solution to the problems mentioned above by proposing an anti-icing system capable of drawing hot air circulating in an air stream of a turbomachine and reinjecting it further upstream, so as to obtain an anti-icing effect on the outer wall of the compressor. The reinjection of hot air into the Airflow occurs only when frost accretion conditions are met. Furthermore, reinjection is carried out using a carefully chosen injection angle, so as not to disrupt the main flow in the airflow during the 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 ferrule, externally delimiting an air channel, the outer ferrule 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 a terminal portion extending from the air reinjection slot, the angle between a tangent of the outer wall ferrule at the level of the air reinjection slot and the terminal portion of the pipe being between 10° and 30°; - a valve positioned in the pipe to interrupt the airflow inside the pipe.

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

[0015] The partial melting of ice crystals forms a solid / liquid mixture that adheres to the compressor wall, namely the outer shell. For example, this situation occurs in the part of the duct forming the air stream, shaped like a gooseneck between the low-pressure compressor and the high-pressure compressor of a twin-spool, twin-flow turbomachine.

[0016] Since the air intake slot is located downstream of the reinjection slot, the intake 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 frost formation 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 heating of the outer shell without generating a disturbing 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 conditions for frost accretion are met. Furthermore, the inventors have verified that the presence of the air injection and sampling slits does not disrupt the main flow in the air stream.

[0019] According to one embodiment, the outer shell has a circular cross-section along a cutting plane normal to an axis of rotation of the turbomachine. In one example, the shell comprises a plurality of air reinjection slots distributed around the x-axis, and 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 through an air sampling slot.

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

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

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

[0024] Advantageously, this embodiment allows hot air to be drawn 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 gates. An air discharge system of a turbomachine includes a shutter t, commonly referred to as a VBV gate. Such a VBV gate is pivotally mounted about a pivot axis on a portion of the inter-compressor housing so that the VBV gate can be moved between a closed position, in which the VBV gate closes the orifice by masking it, and an open position, in which the VBV gate uncovers all or part of the orifice and thus allows air to flow 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 duct is external to the air vein.

[0029] A second aspect of the invention relates to an aircraft turbomachine comprising a blower, 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 turbomachine compressor comprising an anti-icing system according to the first aspect of the invention, said anti-icing method comprising the following steps: • Determine if 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 taken 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 process according to the third aspect of the invention, the reinjection of air is carried out only in the event of a risk of frost formation on the outer shell externally delimiting the air vein.

[0032] According to one embodiment, the method according to the third aspect of the invention further includes a step of sending a risk of icing 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 of digital control of a turbomachine engine, the opening of the valve being triggered by the digital control system of a turbomachine engine.

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

[0035] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which:

[0036] Fig. 1 schematically illustrates one embodiment of the anti-icing system according to the first aspect of the invention;

[0037] Figure [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 inter-compressor gooseneck air stream;

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

[0040] Figures [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 example of an 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 features and advantages of the invention.

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

[0043] For the purposes of understanding the invention, the radial (R), tangential (T), and axial (A) orientations will be adopted according to the RTA frame shown in the figures, whose tangent (T) and axial (A) axes extend in a horizontal plane along the orientation shown 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 with respect to the direction of air flow from the air inlet into the turbomachine to the air outlet out of the turbomachine.

[0045] Figure 1 illustrates an embodiment of the anti-icing system 1 according to the first aspect of the invention. According to the embodiment illustrated in Figure 1, the anti-icing system 1 comprises an outer wall 30 externally delimiting an air channel. The outer wall 30 may be in one or more parts, including at least one ferrule. The wall includes an air intake 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 formation on the outer wall ferrule 30.

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

[0048] The anti-icing system according to the embodiment illustrated in [Fig.1] further includes a valve 70 positioned in the pipe 60 and allowing the airflow inside the pipe 60 to be interrupted. Thanks to the valve 70, the hot air is reintroduced into the air stream only if the conditions for ice accretion on the outer wall ferrule 30 are met.

[0049] In the example illustrated in [Fig.1], the air stream is further delimited internally by a turbomachine hub 2.

[0050] According to the embodiment illustrated in [Fig. 1], the air stream has a low-pressure compressor inlet and outlet, a high-pressure compressor inlet and outlet, and an inter-compressor gooseneck shape, namely a gooseneck connecting an air supply channel from the high-pressure compressor inlet to outlet and from the turbomachine's low-pressure compressor inlet to outlet. The outer wall 30 then has a first portion 11, comprising at least the previously described ferrule, and a second portion 12, comprising a high-pressure compressor housing. The first portion 11 extends between the low-pressure compressor outlet and the high-pressure compressor inlet. The second portion 12 extends between the high-pressure compressor inlet and the high-pressure compressor outlet. The first portion 11 includes the air reinjection slot 40. The second portion includes the air intake slot 50.

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

[0052] The pipe 60 may further, in addition to the terminal portion 65, comprise an initial portion 67, extending from the sampling slot 50, having a larger cross-section than an intermediate portion of the pipe 60 connecting the initial portion to the portion terminal 65. Preferably, the high-pressure compressor housing includes a plurality of slots, only one of which is shown, to pressurize and supply the pipe 60. The pipe 60 can thus include 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 near the air intake slot 50, that is, closer to the air intake slot 50 than to the air reinjection slot 40. In this particular example, the valve 70 is located at the end of the intermediate section connected to the initial section. The location of the valve 70 may depend on the available volume in the turbomachine. In this example, the advantage of having the valve 70 closer to the air intake slot 50 than to the air reinjection slot 40 is that the air in the initial section is warmer than in the opposite case shown in [Fig. 2], explained below. The fact that the air is warmer allows the volume of air to be supplied in the pipe to be reduced when the valve is closed and to maintain a higher pressure on the valve 70 in the closed state so that when it opens it produces a flow of pressurized air.

[0054] Figure 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 further advantage 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 cross-section between the terminal portion 65 and the air sampling slot 50.

[0057] Figure 3 illustrates a portion of the air stream, specifically representing the first portion 11, namely the outer wall ferrule 30, according to one embodiment. In 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 part of an inter-compressor gooseneck. The reinjection slot 40 is positioned in the upstream part of the gooseneck, near the slope reversal. For example, the axial distance x between the air reinjection slot 40 and the outlet of the low-pressure compressor 111 can be between 0.1 L and 0.3 L, where L is the axial distance measured between the outlet of the low-pressure compressor 111 and the inlet of the high-pressure compressor 112.

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

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

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

[0061] If the conditions for ice accretion on the outer wall shell 30 are met, the process 500 includes a step of opening the valve 70 positioned between the air intake slot 50 and the air reinjection slot 40. Opening the valve allows warmer air to be reinjected at the reinjection slot 40 into the upstream part of the gooseneck, 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 valve 70 can, if necessary, be triggered by an operator who has received a signal indicating a risk of icing. Alternatively, the valve can be opened by a digital control system of a turbomachine engine, for example a FADEC-type system.

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

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

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

Claims

Demands

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 intake slot (50) and the air reinjection slot (40) so as to bring the air taken from the air intake slot (50) to the air reinjection slot (40), said pipe (60) having a terminal portion (65) extending from the air reinjection slot (40), the angle between a tangent (100) of the outer wall ferrule (30) at the level of the air reinjection slot (40) and the terminal portion (65) of the pipe (60) being between 10° and 30°; • a valve (70) positioned in the pipe (60) to interrupt the airflow inside the pipe.

2. Anti-icing system (1) according to any 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 are between 0.1L and 0.3L, where L is an axial projection distance measured axially between the low pressure compressor outlet and the high pressure compressor inlet.

4. Anti-icing system (1) according to claim 2 or claim 3, wherein the first part (11) of the outer wall (30) has a gooseneck shape.

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

6. Aircraft turbomachine comprising a blower, a low pressure compressor, a high pressure compressor, an air stream through the high pressure compressor and the low pressure compressor and an anti-icing system (1) according to any 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 any one of claims 1 to 5, said anti-icing method comprising the following steps: - Determining (510) whether ice accretion conditions on the outer shell of the outer wall (30) 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 (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 taken by the sampling slot (50) into the air stream through 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) a risk of icing signal to an operator, the opening of the valve (70) being triggered by the operator.

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

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