Unit for controlling a controlled valve for abstracting an airflow from a pressurized airflow of an aircraft

Abstract

A system for regulating a thermal parameter associated with a heat exchange assembly of a turbomachine includes at least one device for measuring or estimating the thermal parameter, a controlled valve acting on the flow rate of a fluid in the assembly, and a regulator including a comparator determining the sign of an error signal relating to the difference between the thermal parameter and a setpoint. The regulator further includes a switch configured to deliver, based on the sign, to a valve control system, a maximum control current switching the valve in a closed state or a minimum control current switching the valve in an open state, and a phase-shifter configured to apply on the error signal a phase advance determined from an estimate of a time constant of the control system.

Claims

1. A system for regulating a thermal parameter associated with a heat exchange assembly of a turbomachine, comprising: at least one means for measuring or estimating said thermal parameter, a valve controlled by an at least partly electric control system, the valve including a shutter, formed for example by at least one flap, said shutter being configured to vary the flow rate of passage of a fluid in said heat exchange assembly in order to affect said thermal parameter, and a regulator comprising a comparator configured to determine the positive or negative sign of an error signal relating to the difference between a value of the thermal parameter measured or estimated by said means and a setpoint, wherein the regulator further comprises: a switch coupled to the output of the comparator and configured to deliver to the valve control system a maximum control current or a minimum control current based on the positive or negative sign of the error signal, the maximum control current making it possible to switch the shutter of said valve in a first position defining a fully closed state of the valve and the minimum control current making it possible to switch the shutter of said valve in a second position defining a fully open state of the valve, and a phase-shifter configured to apply on the error signal a phase advance determined from an estimate of a time constant of the valve control system.

2. The regulation system according to claim 1, wherein the phase-shifter comprises a diverter configured to provide a time derivative of the error signal, the phase lead applied on the error signal at a given instant being calculated by multiplying the time constant by the time derivative at this instant.

3. The regulation system according to claim 1, wherein the phase-shifter comprises an amplifier configured to apply to the time constant of said valve control system a positive adjustment gain less than or equal to one.

4. The regulation system according to claim 3, wherein the adjustment gain is comprised between 0.4 and 0.6.

5. The regulation system according to claim 1, wherein the valve control system comprises a valve member actuated by an electric motor, as well as pneumatic control means controlled by the valve member and able to actuate the opening and closing of the valve.

6. A turbomachine of an aircraft, comprising a heat exchange assembly and a system for regulating a thermal parameter associated with said heat exchange assembly according to claim 1.

7. The turbomachine according to claim 6, wherein the fluid supplying said heat exchange assembly which thermal parameter is regulated by said regulation system is air led downstream of a fan of the turbomachine and is intended to cool the heat exchange assembly.

8. The turbomachine according to claim 7, wherein the heat exchange assembly which thermal parameter is regulated by said regulation system comprises: a first duct bleeding a first pressurized air stream downstream of a compression stage of the turbomachine, a second duct bleeding a second air stream formed by said air bled downstream of the fan, the temperature of the second bled air stream being lower than the temperature of the first bled air stream, a heat exchanger to which said first and second ducts are connected, said heat exchanger being able to lower the temperature of the first air stream at the outlet of the exchanger by heat exchange with the second air stream, the regulation system further comprising a temperature sensor adapted to measure said thermal parameter, the thermal parameter corresponding to the temperature of the first air stream in the first duct at the outlet of the heat exchanger, and said valve of said regulation system being coupled to the second duct so as to vary the flow rate of the second air stream in order to regulate said temperature of the first air stream in the first duct at the outlet of the heat exchanger.

9. The turbomachine according to claim 6, wherein the heat exchange assembly comprises: at least one duct for bleeding said fluid, the fluid including air bled downstream of a fan of the turbomachine and/or downstream of a compression stage of the turbomachine, and a turbine ring having an outer surface able to be ventilated by said bled air so as to modify the temperature of said ring, said valve being arranged so as to vary the bled air flow rate, in order to control a clearance of turbine blade tips by a regulation of the thermal parameter consisting of the state of expansion of the turbine ring.

10. A method for regulating a thermal parameter associated with a heat exchange assembly of a turbomachine, the method being intended to be implemented in a regulation system which comprises at least one means for measuring or estimating said thermal parameter, a valve controlled by an at least partly electric control system, the valve including a shutter configured to vary the flow rate of passage of a fluid in said heat exchange assembly in order to affect said thermal parameter, the method comprising: comparing in which the positive or negative sign of an error signal relating to the difference between a value of the thermal parameter measured or estimated by said measurement and estimation means and a setpoint is determined, control current switching in which a maximum control current or a minimum control current is delivered to the valve control system based on the positive or negative sign of the error signal, the maximum control current making it possible to switch the shutter of said valve in a first position defining a fully closed state of the valve and the minimum control current making it possible to switch the shutter of said valve in a second position defining a fully open state of the valve, and phase-shifting in which a phase advance determined from an estimate of a time constant of the valve control system is applied on the error signal, the phase-shifting preceding the comparing.

11. The method according to claim 10, wherein the phase-shifting comprises a derivation sub-step in which a time derivative of the error signal is calculated, the phase lead applied on the error signal at a given instant being calculated by multiplying the time constant by said time derivative at this instant.

12. The method according to claim 10, wherein the phase-shifting comprises an amplification sub-step in which a positive adjustment gain less than or equal to one is applied to the time constant of said valve control system.

13. The method according to claim 12, wherein the adjustment gain is comprised between 0.4 and 0.6.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood upon reading the following, for illustrative purposes and without limitation, with reference to the appended drawings in which:

(2) FIG. 1 represents a graph expressing the position of the flaps based on the control current according to the state of the art;

(3) FIG. 2 schematically represents a turbomachine provided with a heat exchange assembly according to one embodiment of the invention;

(4) FIG. 3 schematically represents a control unit according to one embodiment of the invention;

(5) FIG. 4 presents a flowchart of a control method according to one mode of implementation of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

(6) FIG. 2 schematically represents a turbomachine 1 of an aircraft provided with a heat exchange assembly according to one embodiment of the invention.

(7) The turbojet engine 1 is of the turbofan and double-body type and has a longitudinal axis X. The turbojet engine comprises in particular a fan 2 which delivers an air stream divided into a primary stream F.sub.P flowing in a primary flowpath 3 of the primary stream F.sub.P and into a secondary stream F.sub.S flowing in a secondary flowpath 4 of the secondary stream F.sub.S coaxial with the primary flowpath 3. The primary flowpath 3 extends between a core shroud 30 and an inter-flowpath compartment 34, and the secondary flowpath 4 extends between the inter-flowpath compartment 34 and an outer shroud 40. From upstream to downstream in the direction of flow of the primary stream F.sub.P, the primary flowpath 3 comprises a low-pressure compressor 5, a high-pressure compressor 6, a combustion chamber 7, a high-pressure turbine 8 and a low-pressure turbine 9.

(8) The turbojet engine 1 comprises a heat exchange assembly 10 mounted in the inter-flowpath compartment 34. The heat exchange assembly 10 comprises a system for bleeding a hot air stream and a cold air stream, configured to cool the hot air with the cold air and provide at the outlet of the heat exchange assembly 10 a cooled air regulated to a desired temperature and a desired pressure for installations 11 of the aircraft and/or of the turbomachine using such air, such as for example the installation for conditioning the air of the aircraft cabin, the installation for de-icing the aerodynamic surfaces of the turbomachine, etc.

(9) The heat exchange assembly 10 comprises a hot air bleed duct 12, a cold air bleed duct 13 and a heat exchanger 14.

(10) The hot air bleed duct 12 fluidly connects the primary flowpath 3, and more particularly at a compression stage 5 or 6, to the installations 11 via the heat exchanger 14. The hot air bleed duct 12 thus bleeds a portion of the primary stream F.sub.p and conveys it to the installations 11 via the heat exchanger 14. The hot air bleed duct 12 opens into the primary flowpath 3 at a compression stage 5 or 6 and thus connects the latter to the inlet of the heat exchanger 14.

(11) The cold air bleed duct 13 bleeds a portion of the secondary stream F.sub.S in the secondary flowpath 4 and, after having passed through the heat exchanger 14, delivers the portion of air thus bled from the secondary flowpath downstream of the bleed location relative to the direction of the secondary stream F.sub.S. The cold air bleed duct 13 opens for a first time into the secondary flowpath 4 to bleed a portion of the secondary stream F.sub.S and opens for a second time into the secondary flowpath 4 to re-inject the portion of stream thus bled from the secondary stream F.sub.S downstream of the bleed location after having been heated during the passage through the heat exchanger 4. The cold air bleed duct 13 thus puts the secondary flowpath 4 receiving the secondary stream F.sub.S delivered by the fan 2 in communication with the heat exchanger 14.

(12) The cold air coming from the fan 2 thus transversely passes through the heat exchanger 14 to cool the hot air bled from the compressor stage 4 and circulating in the exchanger 14 from its inlet to its outlet. The hot air circulating in the hot air bleed duct 12 and the cold air circulating in the cold air bleed duct 13 remain in separate ducts within the heat exchanger 14 and never mix.

(13) To bleed the cold air stream from the secondary flowpath 4, the heat exchange assembly 10 comprises a controlled valve 15 of the scoop-valve type mounted on the air intake provided in the inter-flowpath compartment 34. The valve 15 comprises mechanical flaps actuated by a cylinder controlled by a control system 35 including a torque motor.

(14) The valve 15, and more particularly the torque motor 35 of the valve 15, is controlled by a control unit 20.

(15) The control unit 20 comprises a temperature sensor 21 mounted in the hot air bleed duct 12 on a portion of the duct extending between the heat exchanger 14 and the installations 11, and a regulator 22 of the temperature of the air stream output from the heat exchanger 14.

(16) The temperature sensor 21 is configured to measure the temperature of the air stream delivered to the installations 11, that is to say the temperature of the hot air stream circulating in the hot air bleed duct 12 at the outlet of the heat exchanger 14.

(17) As schematically illustrated in FIG. 3, the regulator 22 is of the all-or-nothing type and comprises a subtractor 23 receiving as input a temperature setpoint T.sub.C and a measurement of the actual temperature T.sub.M delivered by the temperature sensor 21. The subtractor 23 is configured to determine the error ε, that is to say the difference, between the setpoint temperature T.sub.C and the measured temperature T.sub.M.

(18) The regulator 22 further comprises a phase lead module, or phase-shifter 24, including a bypass block 26, an amplifier 28, a multiplier 29 and an adder 31.

(19) The bypass block 26, or diverter, calculates from the error signal ε delivered by the subtractor 23 the time derivative of the error signal dε/dt. The diverter 26 delivers the time derivative of the error signal dε/dt to the multiplier 29.

(20) The amplifier 28 receives as input a time constant corresponding to the time constant τ of the torque motor 35 of the controlled valve 15. The amplifier 28 applies a positive adjustment gain G less than or equal to one to the time constant τ received as input and outputs a signal corresponding to the multiplication of the time constant τ with the gain G and with the time derivative of the error signal dε/dt.

(21) The adjustment gain allows adjusting the phase lead. A gain of 1 allows a maximum phase lead for this type of regulator 22, which will cycle the control a lot. A gain less than 1 allows limiting the cycle frequency and thus lengthens the service life of the valve 15. A gain of 0.5 brings a good compromise between regulation performance and cycle frequency of the control.

(22) The adder 31 receives as input the signal delivered by the multiplier 29 and the error signal ε delivered by the subtractor 23, and thus outputs an error signal with a phase lead.

(23) The regulator 22 further comprises a comparator 32 and a switch 33. The signal resulting from the adder 31 is sent to the comparator 32 which determines the sign of the resulting signal delivered by the adder 31 of the phase-shifter 24. The sign is then output from the comparator 32 to the switch 33 configured to output a control current value of the torque motor 35 of the valve 15 capable of switching between a first value corresponding to a minimum current Min and a second value corresponding to a maximum current Max.

(24) The high-pressure turbine 8 of the turbojet engine 1 comprises a rotor formed of a disc on which a plurality of movable blades disposed in the primary flowpath 3, are mounted. The rotor is surrounded by a turbine casing comprising a turbine ring carried by an outer turbine casing by means of fixing spacers.

(25) The turbine ring can be formed of a plurality of adjacent sectors or segments. On the internal side, it is provided with a layer of abradable material and surrounds the rotor blades by arranging a clearance with the tips of said blades.

(26) The turbojet engine 1 can further comprise a secondary air bleed system, similar to the heat exchange assembly 10 and not represented in FIG. 2, making it possible to control the clearance by modifying in a controlled manner the internal diameter of the outer turbine casing. To this end, a control unit, similar to the control unit 20 of the heat exchange assembly 10, monitors the bled air flow rate in order to vary the temperature of the air directed towards the outer turbine casing and thus control a clearance of turbine blade tips by a regulation of the thermal parameter consisting of the state of expansion of the turbine ring.

(27) FIG. 4 illustrates a flowchart of a method for controlling a controlled valve for bleeding an air stream in a pressurized air stream of an aircraft according to one mode of implementation of the invention.

(28) In a first step 400, the temperature sensor 21 of the control unit 20 performs a measurement of the temperature T.sub.M of the gas stream circulating in the hot air duct 12 at the outlet of the heat exchanger 14.

(29) In a next step 410, the regulator 22 of the control unit 20 calculates the difference ε existing between the setpoint temperature T.sub.C and the measured temperature T.sub.M in the preceding step 400.

(30) In a next step 420, the regulator applies a phase lead on the difference ε calculated in the preceding step 410.

(31) In a next step 430, the sign of the signal relating to the error ε to which the phase lead has been applied is determined by the comparator 32 of the regulator 22.

(32) The sign determined in the preceding step 430 is then delivered to the switch 33 which outputs a control current whose value corresponds to a maximum value for opening the flaps of the valve 15 or to a minimum value for closing the flaps of the valve 15.

(33) The invention allows providing a control unit for regulating the temperature of the bled stream making it possible to compensate for the dead range of the control current of the control law of the controlled valve.