CA2745138A1 - Probe for measuring the total pressure of a flow and method for implementing the probe - Google Patents
Probe for measuring the total pressure of a flow and method for implementing the probe Download PDFInfo
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- CA2745138A1 CA2745138A1 CA 2745138 CA2745138A CA2745138A1 CA 2745138 A1 CA2745138 A1 CA 2745138A1 CA 2745138 CA2745138 CA 2745138 CA 2745138 A CA2745138 A CA 2745138A CA 2745138 A1 CA2745138 A1 CA 2745138A1
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- probe
- temperature
- nose
- pitot tube
- heating
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft
- G01P5/14—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring differences of pressure in the fluid
- G01P5/16—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft by measuring differences of pressure in the fluid using Pitot tubes, e.g. Machmeter
- G01P5/165—Arrangements or constructions of Pitot tubes
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- Aviation & Aerospace Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Fluid Pressure (AREA)
Abstract
The invention relates to a probe (10) for measuring the total pressure of a flow and a method for implementing the probe (10). The probe (10) is intended to be fitted on an aircraft. The probe (10) comprises a Pitot tube (14) and means (22) for heating the probe assembly (10). According to the invention, the probe (10) also comprises means (38) for measuring a local temperature of a nose (37) of the Pitot tube (14) independently of an average temperature of the probe (10). According to the method, if the temperature delivered by the means (38) for measuring a local temperature of the nose (37) is less than the first reference temperature (T0), then an additional heating of the nose (37) is triggered until a delivered temperature is reached that is at least equal to a second reference temperature (T1) greater than the first reference temperature (T0).
Description
Probe for measuring the total pressure of a flow and method for implementing the probe The invention relates to a probe for measuring the total pressure of a flow and a method for implementing the probe.
Piloting any aircraft requires a knowledge of its speed relative to the air, that is to say, to the relative wind. This speed is determined using probes for measuring the static pressure Ps and the total pressure Pt, and sensors for measuring the angle of angle of attack a and the angle of slideslip P. a and R provide the direction of the speed vector in a reference system, or coordinate system, linked to the aircraft and Pt - Ps provides the modulus of this speed vector. These four aerodynamic parameters therefore make it possible to determine the speed vector of any aircraft, such as, for example, an aeroplane or a helicopter.
The measurement of the total pressure Pt is usually done when using a tube called the Pitot tube. This is a tube that is open at one of its ends and obstructed at the other. The open end of the tube roughly faces the flow.
The stream of air situated upstream of the tube is progressively slowed down to almost zero speed at the tube inlet. The slowing down of the air speed increases the air pressure. This increased pressure forms the total pressure Pt of the air flow. Inside the Pitot tube, the prevailing air pressure is measured.
To be able to function regardless of the atmospheric conditions encountered, this Pitot tube is electrically heated. The heating prevents the tube from being obstructed by ice, during flights in icing conditions. This tube is provided with one or more drain holes and water traps, to avoid any risk of obstructing the total pressure tubing, in case of flight in a water-filled atmosphere (passing through clouds, rainy conditions, etc.), or in flights in icing conditions, to discharge the liquid water deriving from the deicing by the heating device.
The nominal operation of the Pitot tube requires that the heating of the tube to be sufficiently effective to avoid any accumulation of ice or re-freezing in the most extreme flight conditions and that the drain holes should not be totally or partially blocked, which would be detrimental to their function which is that of discharging water that penetrates in flight or on the ground into the total pressure tap situated inside the Pitot tube.
On an aeroplane, a malfunction of the pressure probes, and in particular of the Pitot tubes, may lead to catastrophic situations. Protecting the deicing capabilities of a Pitot tube and detecting its correct operation are therefore imperative.
In current aircraft, the security of its heating capabilities is obtained mainly by monitoring the electric current consumed by each probe. In effect, the heating is generally done by means of a resistive element embedded in the body of the probe and whose resistivity changes with temperature. A
resistive element whose resistance increases with temperature can be chosen. Consequently, if the current consumed by the resistive element is greater than a certain value, then the probe is considered capable of being deiced correctly, otherwise the pressure information that it delivers is not taken into account and the probe is considered to be defective. The applicant realized in-house that this protection device is not totally safe because, in flights in severe or very severe icing conditions, the current consumed may be correct, while the temperature of the nose of the Pitot tube is insufficient to ensure the deicing or anti-icing conditions necessary to a secure flight.
Furthermore, the redundancy of the total pressure measurements which is usually present on aircraft in commercial use is inherently incapable of resolving the problem, given that these extreme conditions are experienced simultaneously by all the Pitot tubes used on the aircraft.
The checking of the effectiveness of the heating device of the Pitot tubes is currently done in a predetermined manner. During type-qualification tests on such a probe, it is made to undergo an entire series of correct operation tests for predetermined icing conditions. The Pitot tube is considered capable of correct operational use when it has successfully undergone all these tests. The series production tests must then ensure that the available heating power is always greater than or at least equal to that of the Pitot tube having successfully undergone the type qualification tests.
These arrangements have a major handicap. They do not make it possible to guarantee the correct operation of the Pitot tube if the icing conditions encountered in flight are different from and more severe than those defined for the qualification tests.
Piloting any aircraft requires a knowledge of its speed relative to the air, that is to say, to the relative wind. This speed is determined using probes for measuring the static pressure Ps and the total pressure Pt, and sensors for measuring the angle of angle of attack a and the angle of slideslip P. a and R provide the direction of the speed vector in a reference system, or coordinate system, linked to the aircraft and Pt - Ps provides the modulus of this speed vector. These four aerodynamic parameters therefore make it possible to determine the speed vector of any aircraft, such as, for example, an aeroplane or a helicopter.
The measurement of the total pressure Pt is usually done when using a tube called the Pitot tube. This is a tube that is open at one of its ends and obstructed at the other. The open end of the tube roughly faces the flow.
The stream of air situated upstream of the tube is progressively slowed down to almost zero speed at the tube inlet. The slowing down of the air speed increases the air pressure. This increased pressure forms the total pressure Pt of the air flow. Inside the Pitot tube, the prevailing air pressure is measured.
To be able to function regardless of the atmospheric conditions encountered, this Pitot tube is electrically heated. The heating prevents the tube from being obstructed by ice, during flights in icing conditions. This tube is provided with one or more drain holes and water traps, to avoid any risk of obstructing the total pressure tubing, in case of flight in a water-filled atmosphere (passing through clouds, rainy conditions, etc.), or in flights in icing conditions, to discharge the liquid water deriving from the deicing by the heating device.
The nominal operation of the Pitot tube requires that the heating of the tube to be sufficiently effective to avoid any accumulation of ice or re-freezing in the most extreme flight conditions and that the drain holes should not be totally or partially blocked, which would be detrimental to their function which is that of discharging water that penetrates in flight or on the ground into the total pressure tap situated inside the Pitot tube.
On an aeroplane, a malfunction of the pressure probes, and in particular of the Pitot tubes, may lead to catastrophic situations. Protecting the deicing capabilities of a Pitot tube and detecting its correct operation are therefore imperative.
In current aircraft, the security of its heating capabilities is obtained mainly by monitoring the electric current consumed by each probe. In effect, the heating is generally done by means of a resistive element embedded in the body of the probe and whose resistivity changes with temperature. A
resistive element whose resistance increases with temperature can be chosen. Consequently, if the current consumed by the resistive element is greater than a certain value, then the probe is considered capable of being deiced correctly, otherwise the pressure information that it delivers is not taken into account and the probe is considered to be defective. The applicant realized in-house that this protection device is not totally safe because, in flights in severe or very severe icing conditions, the current consumed may be correct, while the temperature of the nose of the Pitot tube is insufficient to ensure the deicing or anti-icing conditions necessary to a secure flight.
Furthermore, the redundancy of the total pressure measurements which is usually present on aircraft in commercial use is inherently incapable of resolving the problem, given that these extreme conditions are experienced simultaneously by all the Pitot tubes used on the aircraft.
The checking of the effectiveness of the heating device of the Pitot tubes is currently done in a predetermined manner. During type-qualification tests on such a probe, it is made to undergo an entire series of correct operation tests for predetermined icing conditions. The Pitot tube is considered capable of correct operational use when it has successfully undergone all these tests. The series production tests must then ensure that the available heating power is always greater than or at least equal to that of the Pitot tube having successfully undergone the type qualification tests.
These arrangements have a major handicap. They do not make it possible to guarantee the correct operation of the Pitot tube if the icing conditions encountered in flight are different from and more severe than those defined for the qualification tests.
It may be that the icing conditions encountered in flight at high altitude or in particular weather conditions are not always covered by the type qualification tests which are necessarily limited to predefined domains.
It is in particular worth stressing that the severity of the icing conditions encountered depends on very many parameters such as the water concentration, the temperature of the atmosphere, the distribution of the size of the water or ice droplets, whether or not they are supercooled, and, obviously, on the parameters of the flight - speed, altitude, angle of attack -and on the conditions of installation of the probes which may be more or less io affected by the concentration of the clouds depending on their position on the fuselage (areas of over-concentration, depletion, etc). The combination of all these parameters cannot be fully replicated in the type qualification tests.
Thus, the risk of encountering, in flight, icing conditions leading to a risk of malfunctioning of the Pitot tubes is not a zero risk.
The invention aims to overcome all or some of the problems mentioned above by improving the protection of the operation of a Pitot tube in icing conditions, by monitoring the temperature of the nose of the Pitot tube and, if necessary, by adjusting the heating power locally available at the nose as a function of the temperature measured there.
To this end, the subject of the invention is a probe for measuring the total pressure of a flow, the probe being intended to be fitted in an aircraft, the probe comprising a Pitot tube, means for determining an average temperature of the probe and means for heating the probe assembly driven by the means for determining the average temperature of the probe, characterized in that it also comprises means for determining a local temperature of a nose of the Pitot tube independently of the means for determining the average temperature of the probe, the nose being formed regions of the Pitot tube likely to accumulate particles conveyed by the flow.
Another subject of the invention is a method according to which, if the local temperature delivered by the means for measuring a local temperature of the nose of the Pitot tube is less than the first reference temperature, then the additional heating of the nose of the Pitot tube is triggered until a measured local temperature is reached that is at least equal to a second reference temperature greater than the first reference temperature.
It is in particular worth stressing that the severity of the icing conditions encountered depends on very many parameters such as the water concentration, the temperature of the atmosphere, the distribution of the size of the water or ice droplets, whether or not they are supercooled, and, obviously, on the parameters of the flight - speed, altitude, angle of attack -and on the conditions of installation of the probes which may be more or less io affected by the concentration of the clouds depending on their position on the fuselage (areas of over-concentration, depletion, etc). The combination of all these parameters cannot be fully replicated in the type qualification tests.
Thus, the risk of encountering, in flight, icing conditions leading to a risk of malfunctioning of the Pitot tubes is not a zero risk.
The invention aims to overcome all or some of the problems mentioned above by improving the protection of the operation of a Pitot tube in icing conditions, by monitoring the temperature of the nose of the Pitot tube and, if necessary, by adjusting the heating power locally available at the nose as a function of the temperature measured there.
To this end, the subject of the invention is a probe for measuring the total pressure of a flow, the probe being intended to be fitted in an aircraft, the probe comprising a Pitot tube, means for determining an average temperature of the probe and means for heating the probe assembly driven by the means for determining the average temperature of the probe, characterized in that it also comprises means for determining a local temperature of a nose of the Pitot tube independently of the means for determining the average temperature of the probe, the nose being formed regions of the Pitot tube likely to accumulate particles conveyed by the flow.
Another subject of the invention is a method according to which, if the local temperature delivered by the means for measuring a local temperature of the nose of the Pitot tube is less than the first reference temperature, then the additional heating of the nose of the Pitot tube is triggered until a measured local temperature is reached that is at least equal to a second reference temperature greater than the first reference temperature.
The probe generally comprises a heating resistor making it possible to globally reheat the probe assembly. In some probes, the average temperature is not measured and the heating power is permanently at maximum. Advantageously, the probe may include means for determining its average temperature. To this end, the resistor may be made of a material whose resistivity varies as a function of its temperature. In its use, it is possible to measure the value of the resistor 22 and thus to determine an average temperature of the probe 10.
Whether or not the average temperature of the probe is measured, the measurement of the local temperature of the nose is independent of the average temperature of the probe. In practice, even if the action of the heating resistor, making it possible to globally reheat the probe assembly, also makes it possible to vary the temperature of the nose, factors external to the probe 10 may cause these two temperatures to vary separately from one another. The object of the invention is precisely to distinguish these two temperatures.
The invention will be better understood and other advantages will become apparent from reading the detailed description of an embodiment given as an example, the description being illustrated by the appended drawing in which:
Figure 1 represents a probe for measuring total pressure according to the invention;
Figures 2 and 3 represent exemplary embodiments of a probe for measuring total pressure.
Figure 1 represents a probe for measuring total pressure 10 intended to be fixed across an opening 11 produced in the skin 12 of an aircraft. The probe 10 comprises a portion 13 external to the skin 12 and formed by a Pitot tube 14 borne by a mast 15. The probe 10 also comprises an internal portion 16 mainly comprising an electrical connector 17 and an air connector 18. The connector 18 allows the Pitot tube 14 to be pneumatically connected to a pressure sensor situated inside the skin 12 of the aircraft.
The probe 10 is positioned on the skin 12 of the aircraft so that the Pitot tube 14 is oriented substantially according to a longitudinal axis of the aircraft, outside the boundary layer, so that the direction of flow, represented by an arrow 19, roughly faces an inlet orifice 20 situated at a first end 21 of the Pitot tube 14.
A second end 22 of the Pitot tube 14, opposite the end 21, is closed so as to form a breakpoint in the air stream sampled from the flow and penetrating into the tube 14 through its orifice 20. At the level of the end 22 of the tube, an air jet pipe not represented in Figure 1 opens in the tube 14 to 5 form therein a pressure tap where the air pressure is to be measured. The jet pipe is, for example, linked to a pressure sensor or to another pressure measuring device. The pressure sensor makes it possible to effectively measure the pressure of the air prevailing inside the tube 14 at its end 22.
The pressure sensor may belong to the probe or else be remote from it. In this case, the pressure sensor is connected to the probe 10 by means of the air connector 18.
At the end 22, the tube 14 has one or more drain holes 23 making it possible to discharge particles inside the tube 14. Apart from the drain hole or holes 23, the section is small relative to that of the tube 14, the tube 14 is closed at its end 22. The pressure measured at this end therefore represents the total pressure Pt of the air flow.
In the example represented, the Pitot tube 14 is fixed relative to the skin 12 of the aircraft. It is obviously possible to mount the Pitot tube on a mobile mast, such as, for example, a vane that can be oriented in the axis of the flow, as is described for example in the patent published under the number FR 2 665 539 and filed on August 3, 1990. Thus, when the local angle of attack of the flow in the vicinity of the probe 10 changes, the orientation of the Pitot tube 14 follows this angle of attack in order to always face the flow. The total pressure measurement is thereby enhanced on variations of local angle of attack.
The connector 17 is used to electrically connect the probe 10 to the aircraft, notably to connect the means for heating the probe assembly 10.
These heating means comprise, for example, a heating resistor 24 that makes it possible to reheat the mast 15 and the Pitot tube 14 over its entire length. The heating resistor 24 may be made of a material whose resistivity varies as a function of its temperature. When it is in use, it is possible to measure the value of the resistance 24 and thus determine an average temperature of the probe 10.
Whether or not the average temperature of the probe is measured, the measurement of the local temperature of the nose is independent of the average temperature of the probe. In practice, even if the action of the heating resistor, making it possible to globally reheat the probe assembly, also makes it possible to vary the temperature of the nose, factors external to the probe 10 may cause these two temperatures to vary separately from one another. The object of the invention is precisely to distinguish these two temperatures.
The invention will be better understood and other advantages will become apparent from reading the detailed description of an embodiment given as an example, the description being illustrated by the appended drawing in which:
Figure 1 represents a probe for measuring total pressure according to the invention;
Figures 2 and 3 represent exemplary embodiments of a probe for measuring total pressure.
Figure 1 represents a probe for measuring total pressure 10 intended to be fixed across an opening 11 produced in the skin 12 of an aircraft. The probe 10 comprises a portion 13 external to the skin 12 and formed by a Pitot tube 14 borne by a mast 15. The probe 10 also comprises an internal portion 16 mainly comprising an electrical connector 17 and an air connector 18. The connector 18 allows the Pitot tube 14 to be pneumatically connected to a pressure sensor situated inside the skin 12 of the aircraft.
The probe 10 is positioned on the skin 12 of the aircraft so that the Pitot tube 14 is oriented substantially according to a longitudinal axis of the aircraft, outside the boundary layer, so that the direction of flow, represented by an arrow 19, roughly faces an inlet orifice 20 situated at a first end 21 of the Pitot tube 14.
A second end 22 of the Pitot tube 14, opposite the end 21, is closed so as to form a breakpoint in the air stream sampled from the flow and penetrating into the tube 14 through its orifice 20. At the level of the end 22 of the tube, an air jet pipe not represented in Figure 1 opens in the tube 14 to 5 form therein a pressure tap where the air pressure is to be measured. The jet pipe is, for example, linked to a pressure sensor or to another pressure measuring device. The pressure sensor makes it possible to effectively measure the pressure of the air prevailing inside the tube 14 at its end 22.
The pressure sensor may belong to the probe or else be remote from it. In this case, the pressure sensor is connected to the probe 10 by means of the air connector 18.
At the end 22, the tube 14 has one or more drain holes 23 making it possible to discharge particles inside the tube 14. Apart from the drain hole or holes 23, the section is small relative to that of the tube 14, the tube 14 is closed at its end 22. The pressure measured at this end therefore represents the total pressure Pt of the air flow.
In the example represented, the Pitot tube 14 is fixed relative to the skin 12 of the aircraft. It is obviously possible to mount the Pitot tube on a mobile mast, such as, for example, a vane that can be oriented in the axis of the flow, as is described for example in the patent published under the number FR 2 665 539 and filed on August 3, 1990. Thus, when the local angle of attack of the flow in the vicinity of the probe 10 changes, the orientation of the Pitot tube 14 follows this angle of attack in order to always face the flow. The total pressure measurement is thereby enhanced on variations of local angle of attack.
The connector 17 is used to electrically connect the probe 10 to the aircraft, notably to connect the means for heating the probe assembly 10.
These heating means comprise, for example, a heating resistor 24 that makes it possible to reheat the mast 15 and the Pitot tube 14 over its entire length. The heating resistor 24 may be made of a material whose resistivity varies as a function of its temperature. When it is in use, it is possible to measure the value of the resistance 24 and thus determine an average temperature of the probe 10.
According to the invention, in order to more accurately determine the temperature of a critical area of the probe 10, the latter comprises means for determining a local temperature of a nose 37 of the Pitot tube 14.
Figure 2 represents an exemplary embodiment of a probe measuring total pressure comprising a Pitot tube 14 into which an airstream is intended to penetrate through the end 21. At the end 22, a jet pipe 25 forms the pressure tap of the probe. Between the ends 21 and 22, the air penetrating into the tube 14 passes in succession through an inlet channel 26, a water trap 27 and a tranquillization chamber 28 separated from the water trap 27 by a chicane 29 that is used to stop any particles from being able to penetrated into the tube 14 through the end 21. These particles are discharged from the tube 14 through the drain hole 23. The difference in air pressure between the interior of the tube 14 and the exterior enables the particles present in the water trap 27 to exit from the tube 14 through the drain hole 23.
It is important for the areas of the tube 14 likely to accumulate particles, notably of water, to be maintained at a temperature at which the water does not freeze. In the exemplary embodiment of Figure 2, these areas comprise the inlet channel 26, the water trap 27, and form the nose 37 of the Pitot tube 14. The invention makes it possible to determine specifically the temperature of these areas, notably to determine whether these areas are likely to ice up.
Figure 3 represents another exemplary embodiment of a probe for measuring total pressure comprising a Pitot tube 14. In this example, there are once again the inlet channel 26, the water trap 27 and the tranquillization chamber 28. The water trap 27 and the tranquillization chamber 28 are in this case separated by a wall 30 that is passed through by a nozzle 31 that is open in the water trap 27 and in the tranquillization chamber 28. To prevent particles from penetrating into the nozzle 31, the latter opens into the water trap 27 perpendicularly to a main axis 32 of the air stream penetrating into the tube 14. The inlet channel 26, the water trap 27 and the tranquillization chamber 28 are, for example, of revolution about the axis 32.
To determine the local temperature of the nose 37, it is possible to place, in the nose 37 or immediate proximity thereto, a temperature sensor.
However, advantageously, the means for measuring a local temperature are able to locally to reheat the nose 37 of the Pitot tube 14. For this, the probe may comprise a second heating resistor 38 whose resistivity varies as a function of temperature. The resistive element is suitable for use as a temperature sensor and as a reheater complementing the means for heating 5 the probe assembly. The heating resistor 38 is, for example, formed by a coaxial cable whose core is the actual heating element. The core is electrically insulated for example by means of a mineral insulator which may be welded into a wall forming the Pitot tube 14. The cable is wound in the nose 37 and follows a more linear run in the rest of the probe 10 to the 10 electrical connector 17. In a preferred embodiment, a nickel alloy, or even pure nickel, whose resistance varies greatly with temperature and does so in a relatively linear manner within the temperature ranges of use for a probe 10 fitted in an aircraft, is used for the core. The heating resistors 24 and 38 may be wound in helical form and welded onto the internal walls of the probe 10.
Inside the nose 37, it is possible to wind the two heating resistors 24 and 38 one inside the other both following the internal walls of the inlet channel 26 and of the water trap 27.
Alternatively, the resistive element and the means for heating the probe assembly are formed by a single two-wire coaxial cable. A first wire of the two-wire cable forms the means for heating the probe assembly and a second wire of the cable forms the resistive element intended to reheat the nose 37. This variant simplifies the manufacturing of the probe 10, while retaining the principle of separation of the means for heating the probe assembly 10 and those of the nose 37, which makes it possible to optimize the heating. The second wire is produced in such a way that the value of its resistance is greater at the level of the nose 37 than over the rest of its running in the probe 10 with the first wire.
The probe 10 comprises electronic means 40 for regulating the power supply of the means for heating the probe assembly 10 and electronic means 41 for regulating the means for heating the nose 37. Advantageously, the means 40 and 41 are separate. Exemplary embodiments of the means and 41 are, for example, given in the patent applications published under the numbers FR 2 726 148 and FR 2 849 339. The means 40 and 41 both receive an electrical power supply from the aircraft. Advantageously, the 35 power supply intended for the means for heating the probe assembly 10 and the power supply intended for the means for heating the nose 37 come from separate circuits of the aircraft. To power the electronic regulation means 40 and 41, the probe 10 includes separate power supply terminals, respectively 42 and 43, intended for connection to separate power supply circuits of the aircraft. In other words, the means for heating the probe assembly are powered via the power supply terminals 42. The means for measuring a local temperature of the nose 37 are powered via the power supply terminals 43.
The terminals 42 and 43 are separate.
The probe may include means for comparing the temperature delivered by the means for measuring the temperature of the nose 37 to a first reference temperature To and means for triggering an additional heating of the nose 37 of the Pitot tube 14. In Figure 1, these two means are grouped together in the box 45 with the means for measuring the temperature of the nose 37.
The subject of the invention is also a method whereby, if the temperature delivered by the means for measuring a local temperature of the nose 37 of the Pitot tube 14 is less than the first reference temperature To, then an additional heating of the nose 37 is triggered until a delivered temperature is reached that is at least equal to a second reference temperature T1 greater than the first reference temperature To. The fact that the reference temperature T1 is greater than the reference temperature To makes it possible to avoid numerous and frequent triggerings and stoppages of the heating of the nose 37 around the temperature To.
Advantageously, if, after triggering the additional heating of the nose 37 of the Pitot tube 14, the temperature delivered by the means for measuring a local temperature of the nose 37 of the Pitot tube 14 remains less than the reference temperature To, then the probe is declared to have failed. It is possible to wait for a given time before declaring the probe 10 to have failed. To this end, the probe 10 includes a module 46 generating a validity indication concerning the probe 10. This indication may take two binary values, one being that the probe 10 is valid and the other when the probe 10 is declared to have failed. The probe 10 includes terminals 47 for transmitting the validity indication to a display of the aircraft, for example situated in the cockpit of the aircraft and available to a pilot.
Figure 2 represents an exemplary embodiment of a probe measuring total pressure comprising a Pitot tube 14 into which an airstream is intended to penetrate through the end 21. At the end 22, a jet pipe 25 forms the pressure tap of the probe. Between the ends 21 and 22, the air penetrating into the tube 14 passes in succession through an inlet channel 26, a water trap 27 and a tranquillization chamber 28 separated from the water trap 27 by a chicane 29 that is used to stop any particles from being able to penetrated into the tube 14 through the end 21. These particles are discharged from the tube 14 through the drain hole 23. The difference in air pressure between the interior of the tube 14 and the exterior enables the particles present in the water trap 27 to exit from the tube 14 through the drain hole 23.
It is important for the areas of the tube 14 likely to accumulate particles, notably of water, to be maintained at a temperature at which the water does not freeze. In the exemplary embodiment of Figure 2, these areas comprise the inlet channel 26, the water trap 27, and form the nose 37 of the Pitot tube 14. The invention makes it possible to determine specifically the temperature of these areas, notably to determine whether these areas are likely to ice up.
Figure 3 represents another exemplary embodiment of a probe for measuring total pressure comprising a Pitot tube 14. In this example, there are once again the inlet channel 26, the water trap 27 and the tranquillization chamber 28. The water trap 27 and the tranquillization chamber 28 are in this case separated by a wall 30 that is passed through by a nozzle 31 that is open in the water trap 27 and in the tranquillization chamber 28. To prevent particles from penetrating into the nozzle 31, the latter opens into the water trap 27 perpendicularly to a main axis 32 of the air stream penetrating into the tube 14. The inlet channel 26, the water trap 27 and the tranquillization chamber 28 are, for example, of revolution about the axis 32.
To determine the local temperature of the nose 37, it is possible to place, in the nose 37 or immediate proximity thereto, a temperature sensor.
However, advantageously, the means for measuring a local temperature are able to locally to reheat the nose 37 of the Pitot tube 14. For this, the probe may comprise a second heating resistor 38 whose resistivity varies as a function of temperature. The resistive element is suitable for use as a temperature sensor and as a reheater complementing the means for heating 5 the probe assembly. The heating resistor 38 is, for example, formed by a coaxial cable whose core is the actual heating element. The core is electrically insulated for example by means of a mineral insulator which may be welded into a wall forming the Pitot tube 14. The cable is wound in the nose 37 and follows a more linear run in the rest of the probe 10 to the 10 electrical connector 17. In a preferred embodiment, a nickel alloy, or even pure nickel, whose resistance varies greatly with temperature and does so in a relatively linear manner within the temperature ranges of use for a probe 10 fitted in an aircraft, is used for the core. The heating resistors 24 and 38 may be wound in helical form and welded onto the internal walls of the probe 10.
Inside the nose 37, it is possible to wind the two heating resistors 24 and 38 one inside the other both following the internal walls of the inlet channel 26 and of the water trap 27.
Alternatively, the resistive element and the means for heating the probe assembly are formed by a single two-wire coaxial cable. A first wire of the two-wire cable forms the means for heating the probe assembly and a second wire of the cable forms the resistive element intended to reheat the nose 37. This variant simplifies the manufacturing of the probe 10, while retaining the principle of separation of the means for heating the probe assembly 10 and those of the nose 37, which makes it possible to optimize the heating. The second wire is produced in such a way that the value of its resistance is greater at the level of the nose 37 than over the rest of its running in the probe 10 with the first wire.
The probe 10 comprises electronic means 40 for regulating the power supply of the means for heating the probe assembly 10 and electronic means 41 for regulating the means for heating the nose 37. Advantageously, the means 40 and 41 are separate. Exemplary embodiments of the means and 41 are, for example, given in the patent applications published under the numbers FR 2 726 148 and FR 2 849 339. The means 40 and 41 both receive an electrical power supply from the aircraft. Advantageously, the 35 power supply intended for the means for heating the probe assembly 10 and the power supply intended for the means for heating the nose 37 come from separate circuits of the aircraft. To power the electronic regulation means 40 and 41, the probe 10 includes separate power supply terminals, respectively 42 and 43, intended for connection to separate power supply circuits of the aircraft. In other words, the means for heating the probe assembly are powered via the power supply terminals 42. The means for measuring a local temperature of the nose 37 are powered via the power supply terminals 43.
The terminals 42 and 43 are separate.
The probe may include means for comparing the temperature delivered by the means for measuring the temperature of the nose 37 to a first reference temperature To and means for triggering an additional heating of the nose 37 of the Pitot tube 14. In Figure 1, these two means are grouped together in the box 45 with the means for measuring the temperature of the nose 37.
The subject of the invention is also a method whereby, if the temperature delivered by the means for measuring a local temperature of the nose 37 of the Pitot tube 14 is less than the first reference temperature To, then an additional heating of the nose 37 is triggered until a delivered temperature is reached that is at least equal to a second reference temperature T1 greater than the first reference temperature To. The fact that the reference temperature T1 is greater than the reference temperature To makes it possible to avoid numerous and frequent triggerings and stoppages of the heating of the nose 37 around the temperature To.
Advantageously, if, after triggering the additional heating of the nose 37 of the Pitot tube 14, the temperature delivered by the means for measuring a local temperature of the nose 37 of the Pitot tube 14 remains less than the reference temperature To, then the probe is declared to have failed. It is possible to wait for a given time before declaring the probe 10 to have failed. To this end, the probe 10 includes a module 46 generating a validity indication concerning the probe 10. This indication may take two binary values, one being that the probe 10 is valid and the other when the probe 10 is declared to have failed. The probe 10 includes terminals 47 for transmitting the validity indication to a display of the aircraft, for example situated in the cockpit of the aircraft and available to a pilot.
The electronic regulation means 40 and 41, the box 45 and the module 46 may be grouped together on an electronic card 50 which may be arranged inside the internal path 16. The terminals 42, 43 and 47 then belong to the electrical connector 17.
Claims (11)
1. Probe for measuring the total pressure of a flow, the probe (10) being intended to be fitted in an aircraft, the probe (10) comprising a Pitot tube (14), means (38) for determining an average temperature of the probe (10) and means (22) for heating the probe assembly (10) driven by the means (38) for determining the average temperature of the probe (10), characterized in that it also comprises means (38) for determining a local temperature of a nose (37) of the Pitot tube (14) independently of the means (38) for determining the average temperature of the probe (10), the nose (37) being formed by regions of the Pitot tube (14) likely to accumulate particles conveyed by the flow.
2. Probe according to Claim 1, characterized in that the regions of the Pitot tube (14) likely to accumulate particles conveyed by the flow comprise an inlet channel (26) and a water trap (27).
3. Probe according to one of the preceding claims, characterized in that the means (38) for determining a local temperature are suitable for locally heating the nose (37) of the Pitot tube (14).
4. Probe according to Claim 3, characterized in that the means for measuring a local temperature comprise a heating resistor (38) whose resistivity varies as a function of the temperature, and in that the heating resistor (38) is suitable for use as a temperature sensor and as a heater complementing the means (22) for heating the probe assembly (10).
5. Probe according to Claim 4, characterized in that the heating resistor (38) is wound in the nose (37) of the Pitot tube (14).
6. Probe according to Claim 5, characterized in that the heating resistor (38) is formed by a coaxial cable whose core is the heating element and in that the core is electrically insulated by means of a mineral insulator.
7. Probe according to Claim 5, characterized in that the heating resistor (38) and the means (22) for heating the probe assembly (10) are formed by a coaxial two-wire cable, in that a first wire of the cable forms the means for heating the probe assembly (10), in that a second wire of the cable forms the resistive element (38) and in that the second wire is produced in such a way that the value of its resistance is greater at the level of the nose (37) of the Pitot tube (14) than over the rest of its run in the probe (10) with the first wire.
8. Probe according to one of the preceding claims, characterized in that the means (22) for heating the probe assembly (10) are fed through first power supply terminals (42) of the probe (10), in that the means (38) for measuring a local temperature of the nose (37) of the Pitot tube (14) are fed through second power supply terminals (43) of the probe (10) and in that the first and second terminals (42, 43) are separate.
9. Probe according to one of the preceding claims, characterized in that it comprises means (41) for comparing the temperature delivered by the means (38) for measuring a local temperature of the nose (37) of the Pitot tube (14) to a first reference temperature (T0) and means (41) for triggering an additional heating of the nose (37) of the Pitot tube (14).
10. Method for implementing a probe (10) according to Claim 8, characterized in that, if the temperature delivered by the means (38) for measuring a local temperature of the nose (37) of the Pitot tube (14) is less than the first reference temperature (T0), then the additional heating of the nose (37) of the Pitot tube (14) is triggered until a delivered temperature is reached that is at least equal to a second reference temperature (T1) greater than the first reference temperature (T0).
11. Method according to Claim 10, characterized in that, if, after triggering the additional heating of the nose (37) of the Pitot tube (14), the delivered temperature remains less than the first reference temperature (T0), then the probe (10) is declared to have failed.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR1002806 | 2010-07-02 | ||
| FR1002806 | 2010-07-02 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2745138A1 true CA2745138A1 (en) | 2012-01-02 |
Family
ID=43478217
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2745138 Withdrawn CA2745138A1 (en) | 2010-07-02 | 2011-06-30 | Probe for measuring the total pressure of a flow and method for implementing the probe |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2745138A1 (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106706015A (en) * | 2015-10-08 | 2017-05-24 | 霍尼韦尔国际公司 | Air data probe with double helical coil heater cable |
| US9891083B2 (en) | 2016-01-08 | 2018-02-13 | Honeywell International Inc. | Probe tip for air data probe |
| CN110856280A (en) * | 2018-08-21 | 2020-02-28 | 霍尼韦尔国际公司 | Enhanced skin-tug power management system and method |
| US10877062B2 (en) | 2018-05-09 | 2020-12-29 | Rosemount Aerospace Inc. | Aft-located heated ramp for ice and water management of angle of attack sensors |
| US10928416B2 (en) | 2018-05-09 | 2021-02-23 | Rosemount Aerospace Inc. | Dual heated ramp for ice and water management in angle of attack sensors |
| US11142323B2 (en) | 2018-01-05 | 2021-10-12 | Rosemount Aerospace Inc. | Features to prevent ice accumulation on heated faceplate |
| US11162970B2 (en) | 2019-06-17 | 2021-11-02 | Rosemount Aerospace Inc. | Angle of attack sensor |
| US11181545B2 (en) | 2017-08-17 | 2021-11-23 | Rosemount Aerospace Inc. | Angle of attack sensor with thermal enhancement |
| US11649057B2 (en) | 2019-12-13 | 2023-05-16 | Rosemount Aerospace Inc. | Static plate heating arrangement |
-
2011
- 2011-06-30 CA CA 2745138 patent/CA2745138A1/en not_active Withdrawn
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3173797A1 (en) * | 2015-10-08 | 2017-05-31 | Honeywell International Inc. | Air data probe with double helical coil heater cable |
| US9856027B2 (en) | 2015-10-08 | 2018-01-02 | Honeywell International Inc. | Air data probe with double helical coil heater cable |
| CN106706015A (en) * | 2015-10-08 | 2017-05-24 | 霍尼韦尔国际公司 | Air data probe with double helical coil heater cable |
| US9891083B2 (en) | 2016-01-08 | 2018-02-13 | Honeywell International Inc. | Probe tip for air data probe |
| US10605637B2 (en) | 2016-01-08 | 2020-03-31 | Honeywell International Inc. | Probe tip for air data probe |
| US11768219B2 (en) | 2017-08-17 | 2023-09-26 | Rosemount Aerospace Inc. | Angle of attack sensor with thermal enhancement |
| US11181545B2 (en) | 2017-08-17 | 2021-11-23 | Rosemount Aerospace Inc. | Angle of attack sensor with thermal enhancement |
| US11142323B2 (en) | 2018-01-05 | 2021-10-12 | Rosemount Aerospace Inc. | Features to prevent ice accumulation on heated faceplate |
| US10877062B2 (en) | 2018-05-09 | 2020-12-29 | Rosemount Aerospace Inc. | Aft-located heated ramp for ice and water management of angle of attack sensors |
| US10928416B2 (en) | 2018-05-09 | 2021-02-23 | Rosemount Aerospace Inc. | Dual heated ramp for ice and water management in angle of attack sensors |
| CN110856280A (en) * | 2018-08-21 | 2020-02-28 | 霍尼韦尔国际公司 | Enhanced skin-tug power management system and method |
| US11162970B2 (en) | 2019-06-17 | 2021-11-02 | Rosemount Aerospace Inc. | Angle of attack sensor |
| US11649057B2 (en) | 2019-12-13 | 2023-05-16 | Rosemount Aerospace Inc. | Static plate heating arrangement |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AZWI | Withdrawn application |