System for measuring the pressure of a pressurized air flow of the primary duct of a turbine engine, and turbine engine comprising such a measurement system

Abstract

One aspect of the invention relates to a system (100) for measuring the pressure of a pressurized air flow taken from a primary duct (13) of a turbine engine, downstream of a stage of a high-pressure compressor, the measurement system comprising a line (101) for conveying the pressurized air flow from the primary duct to an electronic unit (102) for measuring the pressure, the electronic unit being arranged in a cold compartment (14) comprising air at a temperature colder than the temperature of the pressurized air flow of the primary duct. This system comprises a mixing chamber (120) positioned in the cold compartment and connected to the line for conveying the pressurized air flow, the mixing chamber receiving a pressurized air flow (F1) discharged through a drainage passage (111) from the line for conveying the pressurized air flow, and a cold air flow (F2) coming from the cold compartment.

Description

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

[0002] The invention has 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 expelled from the turbomachine.

[0004] The turbomachine also includes a computer that performs 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 low-pressure (LP) and high-pressure (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. Measuring this static pressure is used, in particular, for controlling the turbojet engine and for 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, includes an HP compressor, referenced 11, comprising one or more compressor stages, each stage comprising a row of moving blades (called rotor blades) followed by a row of fixed blades (called stator blades). The turbomachine further includes a combustion chamber, referenced 12, a primary flow, referenced 13, and a cold compartment, referenced 14. The turbomachine 10 also includes a static pressure measurement system 100 for the pressurized airflow circulating in the primary flow 13. This static pressure measurement system 100 for the pressurized airflow – more simply called the measurement system – includes a pressurized airflow delivery pipe 101 that draws a portion of the pressurized airflow from the primary flow 13, at the outlet 15 of the HP compressor 11, and delivers 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 that cannot withstand the so-called hot temperatures found in or near the primary stream 13. The electronic unit 102 is therefore located in a so-called cold compartment, that is, one containing air at a temperature lower than the temperature of the pressurized airflow in the primary stream 13. Such a compartment, simply called a cold compartment, could be, for example, a fan compartment, a pylon area of ​​a turbofan engine, or any other compartment located away 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 near the pipes, particularly if the aircraft is on the ground, for example during taxiing, and the ambient temperature is very low (for example, around -15°C), or if the aircraft is in flight and the weather conditions are typical (for example, an ISA of +15°C on the ground and -55°C at 37,000 feet), these negative temperatures can cause the water present in the supply pipe 101 to freeze due to condensation. To prevent the accumulation of condensation in the pressurized airflow supply pipe 101 (more simply called the supply pipe), and thus avoid disrupting or distorting the static pressure measurement of the pressurized airflow, drainage holes are generally provided at the points bottom of said conveying pipe so as to evacuate the condensation water. An example of a portion of conveying pipe 101 is shown in Figure 2. This conveying pipe 101, which ensures the transport of the pressurized air flow 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 evacuation of condensation water to a drainage flow evacuation device (not shown in the figure).

[0007] These drainage holes are small, less than approximately 1 mm in diameter, while the supply pipe has a diameter of around 10 mm. Despite their small size, during most of the aircraft's flight, the high pressure and temperature downstream of the HP 11 compressor (pressure can reach and even exceed 40 bar and temperatures up to 600°C) can cause a significant leak of hot air through the drainage holes 110 into the cold compartment. This hot air leakage can damage surrounding components, especially those made of composite materials, such as a composite housing or cowling, or those containing electronic equipment.To protect surrounding parts from damaging hot air, solutions exist to ensure that the air received by these parts, located near drainage holes, does not exceed acceptable temperature limits. These solutions generally function as jet breakers, meaning they protect the surrounding parts by dispersing the hot air flow to prevent a direct jet of air onto them. These solutions, called "jet breakers," can consist, as schematically represented in Figure 3, of a jet breaker 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 breaker plate 16 is to disperse the hot air flow F1 so that it does not directly impact the part 17 to be protected.Indeed, the hot air flow F1 exiting through the drainage hole 110 impacts the deflector plate 16 and disperses along said plate. The impact therefore occurs on the deflector plate 16 and not on the surrounding part 17.

[0008] Even though these jet-breaking solutions protect surrounding parts from direct impact, they do not change the leak temperature, which can reach 300°C despite heat loss along the pipe. of the delivery 101. However, 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 auto-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 leak airflow, the temperature of which is high.

[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. This system incorporates a mixing chamber installed in the cold compartment to blend the leaky pressurized airflow with cold air from the cold compartment, thus cooling the exhaust air 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 system for measuring the pressure of a pressurized airflow taken from a primary intake of a turbomachine, downstream of a high-pressure compressor and upstream of a combustion chamber of said turbomachine. This measuring system comprises a conduit for conveying the pressurized airflow from the primary intake to an electronic pressure measurement unit. This electronic unit is located in a cold compartment containing air at a temperature lower than that of the pressurized airflow from the primary intake. This measuring system includes a mixing chamber positioned in the cold compartment and connected to the pressurized air supply pipe, the mixing chamber receiving, on the one hand, a pressurized air flow evacuating from the pressurized air supply pipe through a drainage passage and, on the other hand, a cold air flow coming from the cold compartment.

[0012] This measurement 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 streams as they are evacuated into the cold compartment.

[0013] In the description, the terms "outside" and "external" refer to the surfaces or parts of parts furthest from the central axis XX of the primary turbomachine (i.e., the central axis of the turbomachine), as opposed to the terms "inside" 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 complementary characteristics from among the following, considered individually or according to all technically possible combinations: the mixing chamber has at least one first inlet connected to a drainage passage of the pressurized airflow conduit, at least one second inlet receiving, by Venturi effect, a cold airflow from the cold compartment, said cold airflow 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 evacuated.The first inlet of the mixing chamber is traversed 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 for 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 along a... The direction is substantially parallel to that of the pressurized air supply duct. 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 outlets of the mixing chamber are positioned in a second wall of the mixing chamber extending substantially parallel to the first wall of said mixing chamber.Positioning the mixing chamber outlets opposite the first and second inlets disperses the outgoing airflow around the surrounding area to be protected. The drainage duct extends along a drainage duct axis that forms an axis of symmetry for the mixing chamber wall, distinct from the first wall. The mixing chamber outlets are located in a third wall of the mixing chamber and are positioned on the same plane, substantially perpendicular to the drainage duct axis. A distal end of the drainage duct, located within the mixing chamber, includes a shaped nozzle to increase, through the 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 flow 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 vein according to any one of the preceding claims. BRIEF DESCRIPTION OF THE 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 state of the art;

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

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

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

[0021] In the figures, identical elements are identified by identical references. For the sake of readability, the size scales between represented elements are not always strictly adhered to. 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 Figure 4. This Figure 4 functionally represents the portion of the measuring system 100 of the invention housed in a cold compartment 14 of a turbofan 10 such as that shown in Figure 1. In this example in Figure 4, the cold compartment 14 can be, for example, the outer compartment of the blower (called the fan compartment). The system of The device 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 supply line 101 for the pressurized airflow taken from the primary stream 13 of the turbomachine passes through several compartments and / or areas 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 stream 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 conveying pipe 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 supply pipe 101 shown in Figure 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 supply pipe may include several drainage passages 111 distributed at different locations, particularly if the supply pipe 101 extends over a long distance or has a sinuous shape, in which case a drainage passage 111 is 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 supply pipe 101, in order 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 chamber. mixture 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 box 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 Figure 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 mixing chamber 120 to allow the flow of the pressurized leakage air from the drainage passage to the mixing chamber 120. The drainage pipe 112 extends along a drainage pipe axis A which may be perpendicular to the axis B of the supply pipe 101, as shown in Figure 4, or on the contrary not be perpendicular to the axis B of the supply pipe 101; The angle between axis A of the drainage pipe and axis B of the supply pipe can typically be between 30° and 90°.The drainage pipe 112 has two ends: a proximal end 112a connected to the drainage passage 111 and forming the inlet of the drainage pipe, and a distal end 112b opening into the mixing chamber 120 and forming the outlet of the drainage pipe. A nozzle 113 may be provided at this 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 one outer wall 125 – also called the second wall – facing each other. According to the embodiment shown in Figure 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 internal walls 123 and external walls 125 extend mainly along this same direction B. According to some embodiments, the internal walls 123 and external walls 125 can be substantially flat walls extending in the XZ plane of the XYZ frame (embodyment of figure 4), or curved and concentric walls extending concentrically around the conveying 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, circumferential in shape. The mixing chamber 120 then has a substantially cylindrical shape, with a circular cross-section. The third wall 124 can 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 can be polygonal, for example, square or hexagonal.

[0029] As explained previously, the inner wall 123 has a first inlet 122 receiving a flow F1 corresponding to the pressurized leak air flow from the drain 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 sizes, adapted to the dimensions of the mixing chamber 120 and / or the drain 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 wall internal 123 may include a single second inlet 121 of annular shape, concentric with respect to the outlet 112b of the drainage pipe or the nozzle 113. In one variant, the part of the internal wall 123 which is radially internal to the second inlet 121, i.e. the part of the internal 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 F1 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, creating locally a depression allowing the leakage airflow F1 (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 F1 with an even higher velocity, creating an even stronger local pressure drop 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 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 be easily adjusted using the dimensions of the second inlets 121, so that the temperature of the mixture of the cold air stream F2 and the leaky air stream F1 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 engine's thermodynamic balance.

[0031] Regardless of the embodiment (with or without a nozzle), when the cold airflow F2 is drawn into the mixing chamber 120, this cold airflow F2 mixes with the hot leakage airflow F1. Indeed, under the influence of the velocities and pressures of the flows F1 and F2 inside the mixing chamber 120, the flows... These air streams mix and form a resulting airflow F3 whose temperature is intermediate between the temperature of the warm air in the leakage stream F1 and the temperature of the cold air in the leakage stream F2. This resulting airflow F3 is called the intermediate airflow or enthalpy airflow; its temperature is approximately the average of the temperatures of the warm air in the leakage airflow F1 and the cold air in the leakage 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 F1 and F2, and W1 and W2 are the respective mass flow rates of the airflows F1 and F2.For example, at identical mass flow rates, if the exhaust airflow F1 contains hot air at a temperature of approximately 300°C, and the cold airflow F2 contains cold air at a temperature of approximately 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 for exhausting 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 and 122 to maximize the available volume for mixing 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 in Figure 4, the outlet ports 126 are positioned at the corners where the outer wall 125 meets the transverse walls 124.In the embodiment where the mixing chamber 120 is cylindrical, the outlets 126 may 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 such that. The ejection of the intermediate airflow F3 via these outlet ports 126 moves this flow F3 away from the second fresh air inlets 121. In other embodiments, the outlet ports 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 an airflow whose temperature is tolerable by the surrounding parts and which, consequently, does not cause any damage to said surrounding parts.However, the positioning of the outlet ports 126 as shown in the example of Figure 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 plays a role of 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] Those 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, in addition to the advantages already described, helps to limit noise generation. An optimal orientation of the intermediate airflow outlets 126 also prevents recirculation of the intermediate airflow.

[0035] Although described through a number of examples, variants and embodiments, the system for measuring the pressure of a pressurized airflow taken from the primary channel of a turbomachine includes various variants, modifications and improvements which will be obvious to the 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 conveying line (101) for 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 conveying line (101) for the pressurized airflow, the mixing chamber (120) receiving, on the one hand,a pressurized airflow (F1) 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. A measuring 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 pressurized airflow supply line (101), - 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 evacuated.

3. Measurement system according to claim 2, characterized in that the first inlet (122) of the mixing chamber is traversed by a drain pipe (112) connecting the drain passage (111) of the supply pipe to the mixing chamber, said drain pipe having a diameter less than or equal to the diameter of the supply pipe 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 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 (F1) 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 comprises in addition to a system for measuring (100) the pressure of a pressurized airflow taken from the primary vein according to any one of the preceding claims.

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