System for measuring the pressure of a pressurized airflow from the primary intake of a turbomachine and turbomachine incorporating such a measurement system

Abstract

Pressure measurement system of a pressurized airflow from the primary flow of a turbomachine and turbomachine comprising such a measurement system. One aspect of the invention relates to a pressure measurement system (100) of a pressurized airflow taken from a primary flow (13) of a turbomachine, downstream of a stage of a high-pressure compressor, said measurement system comprising a conduit (101) for conveying the pressurized airflow from the primary flow to an electronic pressure measurement unit (102), said electronic unit being disposed in a cold compartment (14) containing air at a temperature lower than the temperature of the pressurized airflow from the primary flow.This system comprises a mixing chamber (120) positioned in the cold compartment and connected to the pressurized air supply line. The mixing chamber receives, on the one hand, a pressurized airflow (F1) exiting the pressurized air supply line through a drain passage (111) and, on the other hand, a cold airflow (F2) from the cold compartment. Figure to be published with the abbreviation: Figure 4.

Description

Title of the invention: System for measuring the pressure of a pressurized airflow from the primary intake of a turbomachine and turbomachine comprising such a measuring system. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a system for measuring the pressure of a pressurized airflow taken from the primary intake of an aircraft turbomachine. It also relates to a turbomachine equipped with such a measuring system.

[0002] The invention finds applications in the field of turbomachinery and in particular in the field of monitoring static pressure upstream of the combustion chamber of the turbomachine. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] In an aircraft turbomachine, such as a turbofan or turbofan engine, a turboprop, or an open rotor architecture, incoming air is compressed in a low-pressure (LP) compressor and a high-pressure (HP) compressor before being mixed with fuel and burned in a combustion chamber. The hot gases produced in the combustion chamber then drive one or more turbines before being ejected from the turbomachine.

[0004] The turbomachine also includes a computer that provides power regulation and general electronic management functions; the computer manages, for example, the fuel flow, the stop positions, the wastegates, etc. Since the role of the LP and HP compressors is to compress the air to bring it to optimal speed, pressure, and temperature at the combustion chamber inlet, it is essential that the static pressure at the HP compressor outlet be monitored and measured. This static pressure measurement is used, in particular, for turbojet control and fuel metering.

[0005] Figure 1 schematically represents an example of a turbomachine 10 of the twin-spool, twin-flow turbojet type with a bypass ratio between 10 and 18. This turbomachine, with a central axis XX, comprises an HP compressor, referenced 11, comprising one or more compressor stages, each stage comprising a row of moving blades (called a rotor blade) followed by a row of fixed blades (called a stator blade). The turbomachine further comprises a combustion chamber, referenced 12, a primary intake runner, referenced 13, and a cold compartment, referenced 14. The turbomachine 10 also comprises a static pressure measurement system 100 for the pressurized airflow circulating in the primary intake runner 13. This static pressure measurement system 100 for the pressurized airflow—called more Simply put, the measuring system includes a pressurized airflow conduit 101 that draws a portion of the pressurized airflow from the primary stream 13, at the outlet 15 of the high-pressure compressor 11, and directs it to a remote electronic pressure measurement unit 102 located in a so-called "cold" compartment. Indeed, the electronic pressure measurement unit—more simply called the electronic unit 102—contains electronic components sensitive to high temperatures and which cannot withstand the high temperatures found in or near the primary stream 13. Therefore, the electronic unit 102 is located in a so-called "cold" compartment, that is, one containing air at a temperature lower than the temperature of the pressurized airflow from the primary stream 13.Such a compartment, simply called a cold compartment, can be, for example, a fan compartment, a pylon area of ​​a turbofan engine, or any other compartment located at a distance from the primary stream and containing air that is relatively cold compared to the air in the primary stream.

[0006] However, when the temperature in the cold compartment is below 0°C in the vicinity of the pipes, in particular if the aircraft is on the ground, for example during taxiing, and the ambient temperature is very negative (for example around -15°C) or if the aircraft is in flight and the weather conditions are typical (for example an ISA atmosphere of +15°C on the ground and -55°C at 37,000 feet altitude), these negative temperatures may cause the water present in the supply pipe 101 and accumulated by condensation in this supply pipe to freeze.To prevent the accumulation of condensation in the pressurized airflow delivery pipe 101 (more simply called the delivery pipe), and thus avoid disturbing or distorting the static pressure measurement of the pressurized airflow, drainage holes are generally provided at the lowest points of said delivery pipe to allow the condensation to be evacuated. An example of a portion of a delivery pipe 101 is shown in [Fig. 2]. This delivery pipe 101, which carries the pressurized airflow from the outlet 15 of the primary vein to the electronic housing 102, has at least one drainage hole 110 made in one of the lowest points of the pipe to allow the condensation to be evacuated to a drainage device (not shown in the figure).

[0007] These drainage holes are small, i.e., less than approximately 1 mm, while the supply pipe has a diameter of approximately 10 mm. Despite the small size of these drainage holes, during most of the aircraft's flight, the high pressure and high temperature prevailing downstream of the HP 11 compressor (the pressure can reach and even exceed 40 bar and (The temperature reaching 600°C) can lead to a significant leakage of hot air through the drainage holes 110, into the cold compartment. These hot air leaks have the disadvantage of damaging surrounding parts, particularly when these parts are made of composite materials, such as a composite housing or hood, or when they contain electronic equipment. To protect surrounding parts from damaging hot air, solutions exist to ensure that the air received by these surrounding parts, near the drainage holes, does not exceed the temperature limits acceptable to these parts. These solutions generally have a jet-break function, that is, they protect the surrounding parts by dispersing the flow of hot air to prevent a direct jet of air onto the surrounding parts. These solutions, called "jet breakers," can consist of, as schematically represented in [Fig.3], in a jet-breaking plate 16 positioned opposite a drainage hole 110 of the supply pipe 101, along the surrounding part 17 to be protected, the role of this jet-breaking plate 16 being to disperse the flow of hot air Fl so that it does not directly impact the part to be protected 17. Indeed, the flow of hot air Fl exiting through the drainage hole 110 impacts the jet-breaking plate 16 and disperses along said jet-breaking plate. The impact therefore takes place on the jet-breaking plate 16 and not on the surrounding part 17.

[0008] Even though these jet-break solutions protect surrounding parts from direct impact, they do not alter the leak temperature, which can reach 300°C despite heat loss along the supply line 101. Such a leak temperature can violate fire prevention criteria, which require maintaining temperatures below the auto-ignition threshold of fuel vapors that may be present in the cold compartment. Indeed, fuel vapors originating, for example, from a leak in a component of the fuel system (such as a line, a pump, or a heat exchanger) can reach the central compartment 18 (called the core compartment) or the cold compartment 14.These fuel vapors can self-ignite under the effect of a high ambient temperature exceeding a predetermined threshold, typically around 200°C, which is likely to occur if they encounter the aforementioned leaky airflow which is at a high temperature.

[0009] There is therefore a real need for a solution to address the problems caused by leaks from drainage holes, not only by protecting the parts surrounding said drainage holes but also by reducing the ambient temperature of the cold compartment. Summary of the invention

[0010] To address the aforementioned problems of hot air leakage through the drain holes of the pressurized air supply duct, the applicant proposes a pressurized airflow pressure measurement system in which a mixing chamber is installed in the cold compartment to mix the leaky pressurized airflow with cold air from the cold compartment so that the exhaust air is cooled to a temperature below the auto-ignition threshold. In addition to cooling the leaky airflow, the mixing chamber also acts as a jet breaker, protecting surrounding components.

[0011] According to a first aspect, the invention relates to a pressure measurement system for a pressurized airflow taken from a primary channel of a turbomachine, downstream of a high-pressure compressor and upstream of a combustion chamber of said turbomachine, said measurement system comprising a conduit for conveying the pressurized airflow from the primary channel to an electronic pressure measurement unit, said electronic unit being disposed in a cold compartment containing air at a temperature lower than the temperature of the pressurized airflow from the primary channel.This measurement system comprises a mixing chamber positioned in the cold compartment and connected to the pressurized air supply line; the mixing chamber receives, on the one hand, a pressurized airflow exiting the pressurized air supply line through a drainage passage and, on the other hand, a cold airflow from the cold compartment.

[0012] This measuring system not only has the advantage of providing a jet-break function protecting surrounding parts from hot air leaks from drainage passages but also of cooling the temperature of the pressurized leak air flows when they are evacuated into the cold compartment.

[0013] In the description, the terms "exterior" and "external" refer to the surfaces or parts of parts furthest from the central axis XX of the primary flow of the turbomachine (i.e. the central axis of the turbomachine), as opposed to the terms "interior" and "internal" which refer to the surfaces and parts of these same parts closest to said central axis XX.

[0014] In addition to the characteristics mentioned in the preceding paragraph, the measurement system according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or according to all technically possible combinations: • the mixing chamber includes at least one first inlet connected to a drain passage of the pressurized air supply duct, and at least one second inlet receiving, by Venturi effect, a flow of cold air from the cold compartment, said cold air flow mixing with the pressurized airflow in the mixing chamber to form an intermediate airflow, and at least one outlet through which the intermediate airflow is discharged. the first inlet of the mixing chamber is crossed by a drainage pipe connecting the drainage passage of the supply pipe to the mixing chamber, said drainage pipe having a diameter less than or equal to the diameter of the supply pipe of the pressurized airflow. The first and second inlets of the mixing chamber have openings positioned in the same first wall of said mixing chamber, said first wall extending in a direction substantially parallel to that of the duct supplying the pressurized airflow. The fact that the first and second inlets are located in the same wall, in close proximity to each other, allows for the intake of cold air by the Venturi effect. The mixing chamber has at least one outlet, preferably at least two, positioned at a distance from the first and second inlets of the mixing chamber, in a wall of the mixing chamber separate from the first wall. The fact that the outlet(s) are located at a distance from the first and second inlets provides a sufficiently large volume to allow for efficient mixing of the hot air stream with the cold air stream. The mixing chamber outlets are positioned in a second wall of the mixing chamber, extending substantially parallel to the first wall. Positioning the mixing chamber outlets opposite the first and second inlets allows the outgoing airflow to be dispersed around the surrounding room to be protected. The drainage pipe extends along a drainage pipe axis which forms an axis of symmetry for the mixing chamber wall, distinct from the first wall. The outlet ports of the mixing chamber are arranged in a third wall of the mixing chamber and are positioned at the level of the same plane substantially perpendicular to the axis of the drainage pipe. a distal end of the drainage pipe located in the mixing chamber includes a nozzle shaped to increase by venturi effect the velocity of the pressurized airflow introduced into the mixing chamber.

[0015] A second aspect of the invention relates to an aircraft turbomachine comprising a central compartment traversed by a primary duct and a cold compartment extending around the central compartment. This turbomachine includes a system for measuring the pressure of a pressurized airflow taken from the primary duct. BRIEF DESCRIPTION OF FIGURES

[0016] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which:

[0017] [Fig.1], already described, represents a schematic view of a turbomachine according to the prior art;

[0018] [Fig.2], already described, represents a schematic front view of a passage of drainage in a pressurized airflow conveying pipe according to the state of the art;

[0019] [Fig.3], already described, represents a schematic cross-sectional view of a break- jet according to the state of the art; and

[0020] [Fig.4] represents a schematic cross-sectional view of a measurement system of the pressure of a pressurized airflow according to the invention.

[0021] In the figures, identical elements are identified by identical reference numerals. For the sake of readability, the size scales between represented elements are not always respected. DETAILED DESCRIPTION

[0022] An example of an embodiment of a pressure measurement system for a pressurized airflow taken from the primary intake of a turbomachine, in which a mixing chamber is installed in a cold compartment to prevent any risk of hot air flowing into the cold compartment, is described in detail below, with reference to the accompanying drawings. This example illustrates the features and advantages of the invention. It should be noted, however, that the invention is not limited to this example.

[0023] An example of a schematic view of the measuring system according to the invention is shown in [Fig. 4]. This [Fig. 4] functionally represents the portion of the measuring system 100 of the invention housed in a cold compartment 14 of a twin-spool turbomachine 10 such as that shown in [Fig. 1]. In this example in [Fig. 4], the cold compartment 14 can be, for example, the outer compartment of the fan (called the fan compartment). The measuring system 100 of the invention can, of course, be installed in any cold compartment of any type of turbomachine, such as the nacelle compartment of a twin-spool turbomachine or the mid-fan compartment of a triple-spool turbomachine. The pressurized airflow supply pipe 101 The fluid taken from the primary flow 13 of the turbomachine passes through several compartments and / or zones of the turbomachine to reach the cold compartment 14 where the electronic control unit 102 is located. Figure 4 shows only the portion of the supply line 101 located in the cold compartment 14. This portion of the supply line 101 passes through the cold compartment 14 until it reaches the electronic control unit 102, whose role is, in particular, to measure the static pressure of the primary flow downstream of the high-pressure compressor 11 and upstream of the combustion chamber 12. It should be noted that, in the invention, no modification of the path of the supply line 101 is necessary compared to the prior art and that, consequently, its impact on the mass of the turbomachine is negligible.

[0024] The portion of the conveying pipe 101 shown in [Fig. 4] extends along an axis B substantially parallel to the central axis X of the turbomachine and includes, upstream of the electronic housing 102, a drainage passage 111. Those skilled in the art will understand that the conveying pipe may include several drainage passages 111 distributed at different locations, particularly if the conveying pipe 101 extends over a long distance or if it has a sinuous shape, a drainage passage 111 being then located at each lowest point of the pipe and connected to a mixing chamber 120 as described below. Each drainage passage 111 has a predefined diameter, on the order of the diameter of the conveying pipe 101, so as to avoid any pressure loss.The drainage passage 111, or drainage hole, constitutes the inlet of a drainage pipe 112 connecting the supply pipe 101 to the mixing chamber 120 described later. Air expansion occurs at the outlet 112b of the drainage pipe 112 (for example, at the nozzle 113), the diameter of the outlet 112b being smaller than that of the drainage pipe 112, for example, equal to the diameter of a drainage hole 110 of the prior art system. The ejection velocity downstream of the drainage pipe 112 is thus maximized, which optimizes the Venturi effect and mixing in the mixing chamber 120.With a drainage assembly as described above (drainage pipe 112, drainage passage 111 and outlet 112b and / or nozzle 113), the data collected by the electronic unit 102 of the measuring system are not modified in any way and can therefore be used in the same way as in the prior art.

[0025] In the embodiment shown in [Fig. 4], the drainage passage 111 formed in the supply pipe 101 is fluidly connected to the mixing chamber 120 by the drainage pipe 112. This drainage pipe 112, for example tubular and of a diameter adapted to the drainage passage 111, extends between said drainage passage 111 and a first inlet 122 formed in the chamber of mixing 120 to allow the flow of pressurized leak air from the drain passage to the mixing chamber 120. The drain line 112 extends along a drain line axis A which may be perpendicular to the axis B of the supply line 101, as shown in [Fig. 4], or conversely not perpendicular to the axis B of the supply line 101; an angle between the axis A of the drain line and the axis B of the supply line can typically be between 30° and 90°. The drain line 112 has two ends: a proximal end 112a connected to the drain passage 111 and forming the inlet of the drain line, and a distal end 112b opening into the mixing chamber 120 and forming the outlet of the drain line.A nozzle 113 may be provided at the distal end 112b of the drainage pipe 112 to increase, by venturi effect, the velocity of the leaky airflow introduced into the mixing chamber 120 for reasons explained later. The nozzle 113 then enters the mixing chamber 120 through the first inlet 122 of said chamber. The nozzle 113 may be formed as a single unit with the distal end 112b of the drainage pipe 112, for example, by restricting the cross-section of said drainage pipe.

[0026] The mixing chamber 120, also called the mixing cavity, comprises at least one inner wall 123 – also called the first wall – and an outer wall 125 – also called the second wall – facing each other. According to the embodiment of [Fig. 4], the inner wall 123 and the outer wall 125 extend substantially parallel to each other, along a principal direction substantially parallel to that of the conveying pipe 101. In other words, in this embodiment, the conveying pipe 101 extends along the axis B and the inner walls 123 and outer walls 125 extend mainly along this same direction B. According to some embodiments, the inner walls 123 and outer walls 125 can be substantially flat walls extending in the XZ plane of the XYZ coordinate system (embodyment of [Fig. 4].4]), or curved and concentric walls that extend concentrically around the supply pipe 101, which ensures greater compactness. .

[0027] According to other embodiments, not shown in the figures, the inner wall 123 and outer wall 125 are not parallel to the axis B of the supply pipe 101; the drainage pipe 112 may, for example, not be linear and may have a bend allowing the mixing chamber 120 to be offset longitudinally (along the X-axis) or transversely (along the Z-axis) relative to the drainage passage 111, without affecting the operation of the system. These embodiments also ensure a certain compactness of the measuring system.

[0028] Regardless of the embodiment, the mixing chamber 120 includes a third wall 124 – also called a transverse wall – for example, of circumferential shape. The mixing chamber 120 then has a substantially cylindrical shape, with a circular cross-section. The third wall 124 may then be concentric with respect to the outlet 112b of the drainage pipe 112 or to the nozzle 113. Alternatively, the cross-section of the mixing chamber 120 may be polygonal, for example, square or hexagonal.

[0029] As explained previously, the inner wall 123 has a first inlet 122 receiving a flow Fl corresponding to the pressurized leakage air flow from the drainage passage 111. The inner wall 123 also has one or more second inlets 121 through which the cold air flow F2 from the cold compartment 14 enters the mixing chamber 120. This / these second inlets 121 can be openings of various shapes and dimensions, adapted to the dimensions of the mixing chamber 120 and / or the drainage pipe 112. In some embodiments, the second inlet(s) 121 are positioned near the first inlet 122, for example on either side of said first inlet, in the same inner wall 123 as said first inlet 122.In the embodiment where the mixing chamber 120 is cylindrical, the inner wall 123 may have a single second inlet 121 of annular shape, concentric with respect to the outlet 112b of the drainage pipe or the nozzle 113. In a variant, the part of the inner wall 123 which is radially internal to the second inlet 121, i.e. the part of the inner wall 123 in the vicinity of the drainage pipe 112, may be formed by an annular shoulder of the nozzle 113 or a collar.

[0030] Thus, following the introduction of the leakage airflow Fl into the mixing chamber 120 with a Venturi effect provided by the outlet 112b or the nozzle 113, a cold airflow F2 is drawn into the mixing chamber 120, as explained previously, locally creating a depression allowing the leakage airflow Fl (i.e. the hot air) to enter the mixing chamber 120 at a high speed, which generates a lamination effect (or Venturi effect), causing the cold airflow F2 to be drawn into the mixing chamber 120 by the second inlet(s) 121.In the embodiment where the drainage pipe 112 is equipped with a nozzle 113 at its outlet 112b, the pressure ratio between the inside and outside of the drainage pipe 112 is even higher, generating a leakage airflow Fl with an even higher velocity, resulting in an even stronger local vacuum around said drainage pipe 112 to draw a flow of cold air F2 into the mixing chamber. For example, if the outlet 112b of the drainage pipe, or the nozzle 113, is considered to be a convergent-divergent nozzle, and when the expansion ratio between the upstream and downstream sides of the drainage pipe (Pamont / Pavai) is high, . Then the Mach number at the throat is equal to 1 and the mass flow rate becomes independent of the downstream pressure; the nozzle is then said to be primed. The flow rate of the cold air stream F2 can then easily be sized via the dimensions of the second inlets 121, so that the temperature of the mixture of the cold air streams F2 and the leaky air stream Fl reaches the desired value. It should be noted that the cold air stream F2 is air that comes directly from the environment of the mixing chamber, which has no impact on the thermodynamic balance of the engine.

[0031] Regardless of the embodiment (with or without a nozzle), when the cold air stream F2 has been drawn into the mixing chamber 120, this cold air stream F2 mixes with the hot leaky air stream Fl.Indeed, under the influence of the velocities and pressures of the flows Fl and F2 inside the mixing chamber 120, the flows mix and form a resulting airflow F3 whose temperature is intermediate between the temperature of the hot air in flow Fl and the temperature of the cold air in flow F2. This resulting airflow F3 is called the intermediate airflow or enthalpy airflow; its temperature corresponds approximately to the average of the temperatures of the hot air in the leaky airflow Fl and the cold air in the cold airflow F2, weighted by the mass flow rates. Thus, the temperature T3 of the resulting airflow F3 is given by: T3 = (W1 * T1 + W2 * T2) / (W1 + W2), where T1 and T2 are the respective temperatures of the airflows Fl and F2, and W1 and W2 are the respective mass flow rates of the airflows Fl and F2.For example, at identical mass flow rates, if the leakage airflow Fl contains hot air at a temperature of around 300°C, and the cold airflow F2 contains cold air at a temperature of around 100°C, then the intermediate airflow F3 contains air at an average temperature of approximately 200°C. This intermediate temperature has the advantage of being well below the auto-ignition threshold temperature of fuel vapors. The intermediate airflow F3, which is discharged into the cold compartment 14, as explained below, therefore meets the fire prevention criteria.

[0032] The intermediate airflow F3 is designed to be exhausted from the mixing chamber 120. To this end, the mixing chamber 120 includes, in addition to the first and second inlets 121 and 122, one or more outlets allowing the exhaust of the intermediate airflow F3. Indeed, the intermediate airflow F3 can only be exhausted through specific outlet ports 126. These outlet ports 126, more simply called outlets, are located at a distance from the first and second inlets 121, 122 in order to provide a maximum volume available for the mixing of the airflows F1 and F2 within the mixing chamber 120. They may be located in the same wall of the mixing chamber or in several walls of said mixing chamber. In the example of [Fig.4], the outlet ports 126 are positioned in the junction angles of the outer wall 125 and the transverse walls 124. In the embodiment where the mixing chamber 120 is cylindrical, the outlets 126 can be formed by several orifices arranged on the circumference of the mixing chamber, for example at the junction of the outer wall 125 and the third wall 124 or circumferential wall. If the outlet orifices 126 are formed in the circumferential wall 124, the drilling axes of said orifices may not be perpendicular to said wall and oriented so that the ejection of the intermediate airflow F3 via these outlet orifices 126 directs this flow F3 away from the second fresh air inlets 121. In other embodiments, the outlet orifices 126 can be positioned in the outermost portion of the transverse walls 124a, 124b (i.e., the parts furthest from the inner wall 123) or in the outer wall 125.Regardless of the positioning of the outlet ports 126, the intermediate airflow F3 exiting the mixing chamber 120 is of a temperature that is tolerable by the surrounding parts and therefore does not cause any damage to said surrounding parts. However, the positioning of the outlet ports 126 as shown in the example in [Fig. 4] offers an additional advantage insofar as it ensures optimal dispersion of the intermediate airflow F3; the external wall 125 of the mixing chamber 120 then acts as a jet breaker identical to that of the prior art sheets.

[0033] According to one embodiment of the invention, the mixing chamber 120 can be connected via its outlet ports 126 to a drainage flow evacuation device, a device not shown in the figures but already used in certain turbomachines. Alternatively, the intermediate airflow F3 exiting the mixing chamber 120 can be directed directly to the outside of the turbomachine.

[0034] A person skilled in the art will understand that the mixing chamber 120 of the measuring system 100 of the invention offers at least two advantages: reducing the temperature of the leakage airflow circulating in the cold compartment and protecting the parts located near the drainage passages 111. An optimal shape of the mixing chamber 120 makes it possible, in addition to the advantages already described, to limit noise generation. An optimal orientation of the outlet ports 126 of the intermediate airflow also makes it possible to avoid recirculation of the intermediate airflow.

[0035] Although described through a number of examples, variants and embodiments, the pressure measurement system of a pressurized airflow taken from the primary flow of a turbomachine includes various variants, modifications and improvements which will be obvious to a person skilled in the art.

Claims

Demands

1. A pressure measurement system (100) for a pressurized airflow taken from a primary channel (13) of a turbomachine (10), downstream of a stage of a high-pressure compressor (11) and upstream of a combustion chamber (12) of said turbomachine, said pressure measurement system comprising a conduit (101) for conveying the pressurized airflow from the primary channel to an electronic pressure measurement unit (102), said electronic unit being disposed in a cold compartment (14) containing air at a temperature lower than the temperature of the pressurized airflow from the primary channel (13), characterized in that it comprises a mixing chamber (120) positioned in the cold compartment (14) and connected to the conduit (101) for the pressurized airflow, the mixing chamber (120) receiving, on the one hand,a pressurized airflow (Fl) exiting the pressurized airflow supply duct through a drainage passage (111) and, on the other hand, a cold airflow (F2) coming from the cold compartment.

2. Measurement system according to claim 1, characterized in that the mixing chamber (100) comprises: - at least one first inlet (122) connected to the drainage passage (111) of the supply pipe (101) of the pressurized airflow, - at least one second inlet (121) receiving, by Venturi effect, the cold airflow (F2) from the cold compartment, said cold airflow mixing with the pressurized airflow (F1) in the mixing chamber to form an intermediate airflow (F3), and - at least one outlet (126) through which the intermediate airflow (F3) is discharged.

3. Measurement system according to claim 2, characterized in that the first inlet (122) of the mixing chamber is traversed by a drainage channel (112) connecting the drainage passage (111) of the supply channel to the mixing chamber, said drainage channel having a diameter less than or equal to the diameter of the supply channel of the pressurized airflow.

4. Measurement system according to claim 2 or 3, characterized in that the first inlet (122) and the second inlet (121) of the mixing chamber (120) have openings positioned in the same first wall (123) of said mixing chamber, said first wall extending in a direction (B) substantially parallel to that of the pressurized air flow conveying duct.

5. Measurement system according to claim 4, characterized in that the mixing chamber has at least two outlet ports (126) positioned at a distance from the first and second inlets (122, 121) of the mixing chamber, in a wall (124, 125) of the mixing chamber distinct from the first wall.

6. Measurement system according to claim 5, characterized in that the outlet ports (126) of the mixing chamber are positioned in a second wall (125) of the mixing chamber (120) extending substantially parallel to the first wall (123) of said mixing chamber.

7. A measuring system according to any one of claims 5 and 6, characterized in that the drainage channel (112) extends along a drainage channel axis (A) which forms an axis of symmetry for the wall (124, 125) of the mixing chamber separate from the first wall.

8. Measurement system according to claim 7, characterized in that the outlet ports (126) of the mixing chamber are arranged in a third wall (124) of the mixing chamber and are positioned at the level of the same plane substantially perpendicular to the axis of the drainage pipe (A).

9. A measuring system according to any one of the preceding claims, characterized in that a distal end (112b) of the drainage pipe (112) located in the mixing chamber (120) comprises a nozzle (113) shaped to increase by venturi effect the velocity of the pressurized airflow (Fl) introduced into the mixing chamber.

10. Aircraft turbomachine (10) comprising a central compartment (18) traversed by a primary flow (13) and a cold compartment (14) extending around the central compartment, characterized in that it further comprises a pressure measurement system (100) of a pressurized airflow taken from the primary vein according to any one of the preceding claims.

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