FR3024751B1

FR3024751B1 - CONTROL UNIT FOR CONTROLLING A GAME BETWEEN AUBES AND A TURBINE RING

Info

Publication number: FR3024751B1
Application number: FR1457620A
Authority: FR
Inventors: Romain POMIER; Remy Viguier
Original assignee: Safran Aircraft Engines SAS; SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2014-08-05
Filing date: 2014-08-05
Publication date: 2019-07-19
Anticipated expiration: 2034-08-05
Also published as: FR3024751A1

Abstract

L'invention concerne une unité de commande pour le pilotage d'un jeu entre des sommets d'aubes d'un rotor de turbine d'un moteur d'aéronef à turbine à gaz et un anneau de turbine d'un carter entourant les aubes, l'unité de commande comprenant un module de commande (50) configuré pour déterminer un signal de commande (SC50) d'au moins une vanne pour agir sur un débit et/ou une température d'air dirigé vers le carter, ledit module de commande (50) comprenant un module de sélection (55) configuré pour sélectionner ledit signal de commande (SC50) parmi un premier, un deuxième, un troisième et un quatrième signal de commande (SC51, SC52, SC53, SC54) en fonction d'un premier, d'un deuxième et d'un troisième indicateurs de sélection (TOP51, TOP52, TOP53).The invention relates to a control unit for controlling a clearance between blade tips of a turbine rotor of a gas turbine engine engine and a turbine ring of a casing surrounding the blades. , the control unit comprising a control module (50) configured to determine a control signal (SC50) of at least one valve for acting on a flow rate and / or an air temperature directed towards the housing, said module controller (50) comprising a selection module (55) configured to select said control signal (SC50) from a first, a second, a third and a fourth control signal (SC51, SC52, SC53, SC54) as a function of first, second and third selection indicators (TOP51, TOP52, TOP53).

Description

Background of the invention

The present invention relates to the general field of turbomachines for aeronautical gas turbine engines. It aims more precisely the control of the game between, on the one hand, the tips of moving blades of a turbine rotor and, on the other hand, a turbine ring of an outer casing surrounding the blades.

The clearance between the top of the blades of a turbine and the ring around them is dependent on the differences in dimensional variations between the rotating parts (disk and blades forming the turbine rotor) and the fixed parts (external casing of which the turbine ring that he understands). These dimensional variations are both of thermal origin (related to variations in the temperature of the blades, the disk and the casing) and of mechanical origin (in particular related to the effect of the centrifugal force exerted on the rotor of turbine).

To increase the performance of a turbine, it is desirable to minimize the game as much as possible.

It is known to use an active steering system to control the blade tip clearance of a turbomachine turbine. A system of this type generally operates by directing on the outer surface of the turbine ring air taken for example at a compressor and / or the fan of the turbomachine. Fresh air sent to the outer surface of the turbine ring has the effect of cooling the latter and thus limiting its thermal expansion. The game is therefore minimized. Conversely, hot air promotes the thermal expansion of the turbine ring, which increases the game.

Such active control is controlled by a control unit, for example by the full authority control system (or FADEC) of the turbomachine. Typically, the control unit acts on a regulating position valve to control the flow rate and / or the temperature of the air directed on the turbine ring.

Document FR 2 997 443 describes such a control unit. This control unit comprises: a take-off management module configured to provide a first control signal and a first selection indicator associated with an aircraft take-off phase; a transient management module configured to provide a second control signal and a second selection indicator associated with a transient flight phase of the aircraft; • a cruise management module configured to provide a third control signal and a third selection indicator associated with a cruise phase of the aircraft; aircraft, and • a selection module.

The selection module selects a control signal of the position of the valve from the first, the second and the third control signals according to the first, second and third selection indicators.

Object and summary of the invention

The present invention proposes an improvement of the mechanism of the control unit described in the document FR 2 997 443. For this purpose, the present invention relates to a control unit for controlling a game between blade tips. a turbine rotor of a gas turbine engine engine and a turbine ring of a housing surrounding the vanes, the control unit comprising a control module configured to determine a control signal of at least one valve for acting on a flow rate and / or an air temperature directed to the casing, the control module comprising; a take-off management module configured to provide a first control signal and a first selection indicator associated with a take-off phase; a transient management module configured to provide a second control signal and a second selection indicator; associated with a transient phase, and - a high altitude cruise management module and mounted configured to provide a third control signal and a third selection indicator associated with a high altitude cruise phase or a climb phase, said control being characterized in that said control module further comprises: - a management module for other stabilized phases configured to provide a fourth control signal associated with the stabilized phases other than the high altitude cruise and the climb, - a selection module configured to select said control signal from the first, the second it, the third and the fourth control signal according to the first, second and third selection indicators. The invention is advantageous in that the game is controlled during the stabilized flight phases of the aircraft other than the high altitude cruise and the climb.

In a particular embodiment, the second selection indicator is determined as a function of a pressure, a running speed of the engine, a temperature, and an altitude.

Thus, the detection of the transient flight phase is improved, because it is no longer based on parameters reflecting only an intention of the turbojet to accelerate or decelerate.

In addition, taking into account the temperature for the determination of the second selection indicator makes it possible not to open at full hot flow the valve when the air sent on the outer surface of the turbine ring has the effect of cooling this latest.

In a particular embodiment, the transient management module configured to further provide a transient duration as a function of: a parameter calculated according to the formula N2.PS3 T3 where N2 is the operating speed of the motor, PS3 is a pressure and T3 is a temperature, and - the derivative ™ of said parameter.

Thus, the valve is folded for a period adapted to the variation of the game, which reduces the energy consumption of the engine.

In a particular embodiment, the first selection indicator is determined according to a management parameter of a thrust instruction applied to the engine and an indicator of the aircraft on the ground.

Thus, it is possible to differentiate a takeoff phase and a touch & go phase.

In a particular embodiment, the take-off management module comprises means for verifying the stability of an operating speed of the engine.

Checking the stability of the system allows waiting for the end of the mechanical expansion of the parts of the high-pressure turbine to open the valve. Thus no further reduction of the game is caused during the detection of the take-off phase, which reduces the risk of blade wear.

In a particular embodiment, the third control signal is determined as a function of a speed of the aircraft, an altitude, a first operating speed of the engine, a second operating speed of the engine and a temperature.

Thus, the risk of blade wear is decreased. The invention further relates to a gas turbine engine comprising a control unit as defined above and at least one valve for acting on a flow rate and / or a temperature of air directed towards the crankcase, in wherein said valve is controlled according to said control signal. The invention furthermore relates to a method for controlling a clearance between blade tips of a turbine rotor of a gas turbine engine engine and a turbine ring of a casing surrounding the blades, the method being implemented by a control unit and comprising determining a control signal of at least one valve to act on a flow rate and / or a temperature of air directed towards the housing, the method being characterized in it comprises, for determining the control signal: a step of supplying a first control signal and a step of providing a first selection indicator associated with a take-off phase, a step of providing a control signal; a second control signal and a step of providing a second selection indicator associated with a transient phase; a step of providing a third control signal and a step of providing a third selection indicator associated with a second selection indicator associated with a transient phase; a pha high altitude cruising or climbing phase, - a step of providing a fourth control signal associated with the stabilized flight phases other than the high altitude cruising and the climb, the control signal determined by the flight unit. control being selected from the first, second, third and fourth control signals according to the first, second and third selection indicators.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures: - Figure 1 is a schematic view in longitudinal section of a portion of a gas turbine engine engine according to one embodiment of the invention; FIG. 2 is an enlarged view of the engine of FIG. 1 showing in particular the high-pressure turbine thereof; FIG. 3 is a block diagram of a control module of a control unit according to one embodiment of the invention; FIG. 4 is a block diagram of a take-off management module of a control module of a control unit according to an exemplary embodiment of the invention; FIGS. 5 and 7 are flowcharts of steps of a game control method implemented by the takeoff management module of FIG. 4; FIG. 6 is a graph representing a conversion law used by the takeoff management module of FIG. 4; FIG. 8 is a block diagram of a transient management module of a control module of a control unit according to an exemplary embodiment of the invention; FIGS. 9 and 12 are step flowcharts of the game control method implemented by the transient management module of FIG. 8; FIG. 10 is a graph representing a conversion law used by the transient management module of FIG. 8; FIGS. 11a and 11b are graphs representing durations determined by the transient management module of FIG. 8; FIG. 13 is a block diagram of a management module for high altitude cruising and mounting of a control module of a control unit according to an exemplary embodiment of the invention; FIGS. 14 and 15 are flowcharts of steps of the game control method implemented by the management module for high altitude cruising and climb of FIG. 13; FIG. 16 is a graph representing a conversion law used by the management module for high altitude cruising and climbing of FIG. 13; FIG. 17 is a flowchart of steps of the game control method, implemented by a management module for other stabilized phases of a control module of a control unit according to an exemplary embodiment. of the invention; - Figure 18 is a block diagram of a module for selecting a control module of a control unit according to an exemplary embodiment of the invention.

Detailed description of an embodiment

FIG. 1 schematically represents a turbojet engine 10 of the double-flow, double-body type to which the invention applies in particular. Of course, the invention is not limited to this particular type of gas turbine engine, adapted to be mounted in an aircraft.

In a well known manner, the turbojet engine 10 of longitudinal axis XX comprises in particular a fan 12 which delivers a flow of air into a primary flow stream 14 and into a secondary flow stream 16 coaxial with the vein primary flow. From upstream to downstream in the flow direction of the gaseous flow therethrough, the primary flow flow channel 14 comprises a low-pressure compressor 18, a high-pressure compressor 20, a combustion chamber 22, a high turbine 24 and a low pressure turbine 26.

As shown more specifically in FIG. 2, the high-pressure turbine 24 of the turbojet engine comprises a rotor formed of a disc 28 on which a plurality of movable vanes 30 arranged in the flow vein of the primary flow 14 are mounted. rotor is surrounded by a turbine casing 32 comprising a turbine ring 34 carried by an outer turbine casing 36 by means of fixing struts 37. The turbine ring 34 may be formed of a plurality of sectors or adjacent segments. On the inner side, it is provided with a layer 34a of abradable material and surrounds the vanes 30 of the rotor, making with the apices 30a thereof a clearance 38.

This clearance 38 depends on differences in dimensional variations between the rotating parts (disk and vanes forming the turbine rotor) and the fixed parts (external casing including the turbine ring that it comprises). These dimensional variations are both of thermal origin (related to variations in the temperature of the blades, the disk and the casing) and of mechanical origin (in particular related to the effect of the centrifugal force exerted on the rotor of turbine).

According to the invention, there is provided a system for controlling the clearance 38 by modifying, in a controlled manner, the internal diameter of the outer casing of turbine 36. For this purpose, a control unit 46 controls the flow and / or the temperature of the air directed towards the turbine outer casing 36. The control unit 46 is for example the full authority control system (or FADEC) of the turbojet engine 10.

In the example shown, a control box 40 is arranged around the outer turbine casing 36. This housing receives fresh air by means of an air duct 42 opening at its upstream end in the duct. flow of the primary flow at one of the stages of the high-pressure compressor 20 (for example by means of a bailer known per se and not shown in the figures). The fresh air circulating in the air duct is discharged on the outer turbine casing 36 (for example by means of a multiperforation of the walls of the control box 40) causing a cooling thereof and therefore a decrease of its internal diameter.

As shown in FIG. 1, a valve 44 is disposed in the air duct 42. This valve 44 is controlled by the control unit 46.

The valve 44 is here a valve in a controlled position. The position of the valve 44 can be between 0%, corresponding to a closed valve, and 100%, corresponding to an open valve. When the valve 44 is open (100% position), the fresh air is supplied to the outer turbine casing 36, which has the effect of a thermal contraction of the latter and therefore a reduction of the clearance 38. On the contrary, when the valve 44 is closed (position 0%), the fresh air is not brought to the outer casing of turbine 36 which is heated by the primary flow, which has the effect of thermal expansion of the latter and a increased clearance 38. In the intermediate positions, the outer casing turbine 36 contracts or expands and the clearance 38 increases or decreases, to a lesser extent.

Of course, the invention is not limited to this particular type of control of the dimensions of the housing 32. Thus, another example not shown is to take air at two different stages of the compressor and to control valves to modulate the flow rate of each of these samples to adjust the temperature of the mixture to be directed on the outer turbine casing 36. This variant can be reduced by equivalence to control based on a control signal between 0% and 100% and n is not described in detail.

The control of the valve 44 by the control unit 46 is now described in more detail. The control unit 46 presents the hardware architecture of a computer and notably comprises a processor, a non-volatile memory, a volatile memory, etc. The non-volatile memory of the control unit 46 constitutes a recording medium, readable by the processor of the control unit 46 and on which is recorded a computer program comprising instructions for executing the steps of FIG. a control method according to the invention.

In known manner, the control unit 46 obtains, by measurement or by calculation, the values of various quantities characterizing the operation of the aircraft and the turbojet engine 10, and in particular the following quantities; RATING, a signal created by the thrust management function of the control unit 46, described in more detail below, Mach, the number of mach of the aircraft: this number, in known manner, is representative of the speed of the aircraft (reduced to the speed of sound), - ALT, the flight altitude of the aircraft, - NI, the low-pressure body of the turbojet engine, - N2, the body regime high-pressure turbojet engine, - Ps3, combustion chamber pressure 22, - Xnl2r, reduced low-pressure body speed, - T3, combustion chamber temperature 22, and - WOW (Weight On Wheel) , the indicator of the aircraft on the ground. Indeed, the turbojet engine 10 is adapted to be mounted in an aircraft.

The RATING signal is used by the thrust management function (or thrust command management function) of the control unit 46, and is known to those skilled in the art. It reflects here the different positions of the joystick (ie piloting) used by the pilot of the aircraft.

In the example envisaged here, the signal RATING can take 16 discrete values numbered 0 to 15 reflecting different levels of thrust applied to the turbojet engine 10, from which can be deduced an operating speed of the turbojet engine 10 (eg NI regime).

Table I indicates, by way of illustration, the name of the RATING associated with the numbers 0 to 15, which corresponds here to the value (or the range of values) of the thrust setpoint applied to the turbojet engine for each RATING. The third column of Table I will be described below.

Table I

In this table I; - MaxRev is the maximum thrust available in reverse mode (reverse thrust); - MinRev is the intermediate thrust available in reverse mode (thrust reversal) (the minimum thrust corresponding to the idle speed); - MCL (for Maximum CLimb rating) means the maximum recommended thrust for climbing phases; Maximum Cruise Rating (MCR) is the maximum recommended thrust for cruising; - NTO (for Normal Take Off) designates the thrust available at takeoff, during normal operation of the turbojet engine; - APR (Automatic Power Reserve) means the maximum thrust certified for takeoff in case of failure of the other turbojet engine of the aircraft; and MCT (Maximum ConTinous rating) means the maximum thrust available for a continuous operation of the turbojet engine, intended initially for emergency situations.

Figure 3 shows the control unit 46 according to one embodiment of the invention. This control unit 46 implements a control module 50, in which a control signal SC50 of the valve 44 is determined. The control module 50, which is described in the form of functional modules 51, 52, 53, 54 and 55, corresponds by

example to the execution of the aforementioned computer program by the control unit 46.

More specifically, the control module 50 comprises a take-off management module 51, a transient management module 52, a management module for high altitude cruising and mounted 53, a management module for other stabilized phases 54 and a module selection 55.

The management module for take-off 51 detects a take-off phase of the turbojet engine 10. By take-off phase is meant a phase of operation of the turbojet engine during which the aircraft leaves the ground.

The take-off management module 51 determines and provides a TOP5i take-off selection indicator whose value depends on the detection or non-detection of the take-off phase. This indicator specifies (in particular for the selection module 55) whether or not a control signal for take-off SC5i can be selected as control signal of the valve 44. Thus, the selection indicator for take-off TOP51 can take a value " 1 ", corresponding to a detection of a take-off phase and signifying that the control signal SC51 can be selected, or a value" 0 "corresponding to a no take-off phase detection.

In addition, the take-off management module 51 determines and provides the take-off control signal SC51 for controlling the opening of the valve 44 if this take-off command signal SC51 is selected by the selection module 55.

The control signal SC51 can take a predefined value Vfull corresponding to an opening of the valve 44 at full cold flow or a predefined value VLow, corresponding to an opening of the valve 44 at full hot flow. In one example, the opening of the valve 44 at full cold flow corresponds to a 100% valve opening. In addition, in one example, the opening of the valve 44 at full hot flow corresponds to a 35% valve opening.

The command signal for take-off SC51 is determined according to the parameter RATING. The TOP51 take-off indicator is determined based on RATING, WOW, N2, and engine shutdown time (before start, calculated by time at shutdown and time at start time) and idling time before taking off.

The transient management module 52 detects a transient phase of the turbojet engine 10. By transient phase is meant an operating phase of the turbojet engine 10 during which the temperatures of the parts of the high-pressure turbine 24, the casing 36 or the rotor 28 change. (For example following an acceleration or deceleration of the aircraft) and / or during which these parts expand under the effect of a centrifugal force or pressure. This evolution causes a variation of the game 38.

The transient management module 52 determines and provides a transient selection flag TOP52 whose value depends on the detection or non-detection of the transient phase. This indicator specifies (especially to the selection module 55) whether or not a transient control signal SC52 can be selected as the control signal of the valve 44. Thus, the transient selection indicator TOP52 can take a value " 1 ", corresponding to a detection of a transient phase of flight and signifying that the control signal SC52 can be selected, or a value" 0 ", corresponding to a no transient flight phase detection.

In addition, the transient management module 52 determines and provides the transient control signal SC52 for controlling the opening of the valve 44 if this transient control signal SC52 is selected by the selection module 55.

The control signal SC52 may take a predefined value VR corresponding to an opening of the valve 44 in fold or the predefined value VLow, corresponding to the opening of the valve 44 at full hot flow. The value VR is defined so as to overcome a hot air flow temperature insufficient to expand the outer casing 36 and thus not allowing to increase the clearance 38. In one example, the opening of the valve 44 in retract corresponds to a 0% valve opening (the valve being thus closed). In addition, in one example, the opening of the valve 44 at full hot flow corresponds to a 35% valve opening.

The transient control signal SC52 is determined according to the parameters WOW, ALT and N2. The transient selection flag TOP52 is determined according to the signals Ps3, N2, T3, ALT.

The management module for high altitude cruising and climb 53 detects a high altitude cruising phase or a rising phase of the turbojet engine 10. By high altitude cruising phase, is meant a phase of flight of the cruiser type aircraft, in the altitude of the aircraft is greater than 30,000 feet. Climb phase means a phase of flight of the aircraft following take-off, where the aircraft is moving towards a cruising altitude.

The management module for high altitude cruising and climb 53 determines and provides a selection indicator for high altitude cruise and climb TOP53 whose value depends on the detection or non-detection of the high altitude cruise phase or the climb phase. . This indicator specifies (in particular for the selection module 55) whether or not a control signal for high altitude cruise and climb SC53 can be selected as the control signal of the valve 44. Thus, the selection indicator for high altitude cruising and up TOP53 can take a value "1", corresponding to a detection of a high altitude cruise phase or a rising phase and meaning that the control signal SC53 can be selected, or a value "0" corresponding to a no high altitude cruise phase detection and no rise phase detection.

In addition, the high altitude cruise and climb management module 53 determines and provides the command signal for high altitude cruising and climb SC53 to control the opening of the valve 44 if this command signal for high altitude cruising and climb SC53 is selected by the selection module 55.

The command signal for high altitude cruising and climb SC53 is determined according to the signals Mach, ALT, N2, Xn12r and T3. The selection indicator for high altitude cruise and TOP53 cruise is determined according to the RATING, Mach and ALT signals.

The management module for other stabilized phases 54 determines and provides a control signal for other stabilized phases SC54, for controlling the opening of the valve 44 if this control signal for other stabilized phases SC54 is selected by the selection module 55 .

The control signal for other stabilized phases SC54 is determined according to the signals WOW, ALT and N2.

The other stabilized phases are the stabilized phases in which there is no objective of limiting the clearance 38, unlike the stabilized phases of high altitude cruising and climbing. Other stabilized phases include a ground idle phase, a descent phase and a low altitude cruise phase.

The idling phase on the ground corresponds to a phase following the landing of the aircraft. In addition, the descent phase corresponds to a phase of flight during which the aircraft leaves a cruising altitude to land. In addition, the low-altitude cruise phase corresponds to a flight phase of the cruise-type aircraft, in which the altitude of the aircraft is less than 30,000 feet.

The control signal SC54 can take the preset value VR corresponding to an opening of the valve 44 in fold or the preset value VLow, corresponding to the opening of the valve 44 at full hot flow. The value VR is defined so as to overcome a hot air flow temperature insufficient to expand the outer casing 36 and thus not allowing to increase the clearance 38. In one example, the opening of the valve 44 in retract corresponds to a 0% valve opening. In addition, in one example, the opening of the valve 44 at full hot flow corresponds to a 35% valve opening. The management module for other stabilized phases thus has the function of increasing the game 38.

The selection module 55 selects one of the control signals SC51, SC52, SC53 and SC54 respectively provided by the management modules 51, 52, 53 and 54, as a function of the operating speed of the turbojet engine 10, and more specifically in the mode of operation. embodiment described here, as a function of signals TOP51, TOP52 and TOP53. The selected signal is noted SC50. The control unit 46 then controls the opening of the valve 44 as a function of the control signal SC50 thus determined.

FIG. 4 represents the take-off management module 51 according to an exemplary embodiment of the invention.

This take-off management module 51 comprises means 60 for detecting a takeoff phase, means 70 for checking the stability of the speed N2, means 80 for calculating the opening time of the valve 44, means for determining computation 90 of the TOP51 takeoff selection indicator and calculating means 100 of the control signal SC51.

The detection means 60 detect a take-off phase, in a step S1, when a first take-off condition and a second take-off condition are verified (see FIG. 5).

The first takeoff condition is an aircraft on the ground for a first confirmation period Del. This first condition is verified, in a substep sl.l, by the detection means 60 when the next equality is verified during the whole of a first confirmation duration Del: wow = i

Indeed, the signal WOW takes the value "1" when the aircraft is on the ground. In one example, the first confirmation duration Del is 240 seconds.

The first condition for determining the take-off phase makes it possible to differentiate the take-off phase with a "touch &go" phase. By phase of "touch &go" is meant a landing phase where the aircraft does not stop completely and leaves immediately. The phases of "touch &go" can not be managed by the management module for takeoff 51, because the antecedent of the landing does not make it possible to ensure that the game is dilated (phases of acceleration possible). The phase of "touch &go" is therefore managed by the transient management module.

The second takeoff condition is an aircraft steering angle greater than 22 degrees for a second confirmation period. This first condition can be verified, in a substep si.2, by the detection means 60 when the following inequality is verified during the whole of a second confirmation duration Dc2:

RATING> NTO

Indeed, an aircraft throttle angle greater than 22 degrees corresponds in one example to the value of the minimum RATING parameter for which the aircraft can take off (this value corresponding to the take-off of an aircraft with a low mass) . In one example, the second confirmation duration Dc2 is 2 seconds.

When the take-off phase is detected by the detection means 60 (step S1), the verification means 70 verify, in a step S5, that the regime N2 is stable.

Indeed, at the beginning of the take-off phase, a mechanical expansion of the parts of the high-pressure turbine 24, correlated to the N2 regime, is observed. This expansion causes a tightening of the clearance 38. It is therefore advisable not to open the valve 44 during this expansion, since this would cause a further reduction of the clearance 38, which could wear the blades 30.

Verification of the stability of the speed N2 by the verification means 70 thus makes it possible to wait until the end of the mechanical expansion to open the valve 44.

The regime N2 is considered stable by the verification means 70 when the following inequality is verified during the whole of a third confirmation duration Dc3: dN2 -z- <Sl dt where is the derivative with respect to the time of the regime N2 and where SI is a first predetermined threshold.

In one example, the third confirmation duration Dc3 is 5 seconds. In one example, the first threshold S1 is 80 rpm / s.

When the regime N2 is considered stable by the verification means 70, the calculation means 80 calculate, in a step S10, the opening time Dvl of the valve 44. The means 80 thus make it possible to limit the duration of opening. of the valve 44 during take-off.

More specifically, the calculation means 80 implement, in a sub-step slO.l, a conversion law for determining a first duration Dvl.l as a function of the regime N2. An example of this conversion law is illustrated in FIG. 6. This figure shows that the higher the regime N2, the lower the first duration Dvl.l is important.

In a substep sl0.2, a second duration Dvl.2 is added to the first duration Dvl.l if two conditions are satisfied. Indeed, if these two conditions are verified, it means that the rotor did not have time to converge before takeoff. The duration of opening Dvl is then equal to the sum of the first duration Dvl.l and the second duration Dvl.2. Otherwise, the duration of opening is equal to the first duration Dvl.l.

The first condition is an engine stop time Da greater than a stopping time threshold. In one example, this threshold of stopping time is 3 hours. This calculation of the idle time Da is carried out thanks to the time before the stopping of the engine (recorded in NVM) and the time at the start of the engine.

The second condition is a slow Dra duration. In one example, this condition is verified when the regime N2 is greater than a predetermined speed threshold N2 for a predetermined duration. In one example, this regime threshold N2 is equal to 700 revolutions per minute and this predetermined duration is 15 minutes.

In one example, the second duration Dvl.2 is 50 seconds.

After calculating the opening time of the valve Dvl, the calculating means 90 of the take-off indicator TOP51 calculate, in a step S15, the value of the selection indicator for takeoff TOP51.

More precisely, the calculation means 90 put, in a sub-step sl5.1, the selection indicator for takeoff TOP51 to the value "1" during the opening time Dvl.

Then, the calculation means 90 put, in a sub-step sl5.2, the selection indicator for takeoff TOP51 to the value "0" for a predetermined duration. In one example, this predetermined duration is 200 seconds. This substep sl5.2 avoids two management too close to a takeoff phase.

The calculating means 100 of the control signal SC51 calculate, in a step S20, a value of the control signal SC51 (see FIG. 7). More precisely, the calculating means 100 of the control signal SC51 determine, in a sub-step s20.1, whether the following inequality is satisfied:

RATING> NTO

If this inequality is verified, the calculation means 100 of the control signal SC51 select, in a step s20.2, for the control signal SC51, the value VFull.

Thus, if the control signal SC51 is selected by the selection module 55, the opening of the valve 44 to full cold flow is controlled, which limits the play during the opening time of the valve Dvl.

This limitation of the opening of the clearance 38 makes it possible to limit the overtaking (or "overshoot" in English) of the limit set for the exhaust gas temperature (EGT Exhaust Gas Temperature) at the outlet of the high-pressure turbine 24 of the turbojet engine 10 (this limit may be greater than the temperature limit certified by the manufacturer of the turbojet engine 10 (or also known as the "EGT redline")).

If the previous inequality is not verified, the take-off management module 51 selects, in a step s20.3, the value VLow for the control signal SC5i. Sub-step s20.1 thus makes it possible not to open valve 44 at full cold flow if a take-off phase has been detected and then interrupted. At the end of the flow of the opening time of the valve Dvl, the selection indicator for takeoff TOP51 is set to the value "0", and the control signal SC51 is no longer selected. The opening of the valve 44 is then reduced, which makes it possible to increase the clearance 38 and thus to protect the mechanism of the valve 44.

FIG. 8 represents the transient management module 52 according to an exemplary embodiment of the invention.

This transient management module 52 comprises means 100 for detecting a transient phase and means 110 for calculating a duration for folding the valve 44, means 120 for setting the zero time folding of the valve 44, and calculation means 130 of the control signal SC52.

The detection means 100 of a transient phase detect a transient phase, in a step S25, when at least one condition, among an assembly comprising a first condition and a second condition, is verified (see FIG. 9).

The first condition corresponds to a deceleration of the aircraft. This first condition is verified, in a substep s25.1, by the detection means 100 as long as the following inequality is verified:

N2 PS3 where is the derivative with respect to the time of t3, and where S3 is a third predetermined threshold. In one example, the third threshold S3 is -40 rpm.bar/K.

The second condition corresponds to an acceleration of the aircraft at low altitude. This second condition is verified, in a sub-step s25.1, by the detection means 100 as long as the following inequalities are verified:

or

is the time derivative of Ν2 '™ 3, where S4 is a fourth predetermined threshold, and where S5 is a fifth predetermined threshold. In one example, the fourth threshold S4 is 50 rpm.bar/K. In one example, the fifth threshold is 30000 feet.

The first condition and the second condition are related to the variation of the parameter N2 '^ 3. Indeed, a variation of this parameter announces an evolution of the game 38.

The transient phase is not detected for an acceleration of the aircraft at high altitude, because at high altitude, the flow rate of the valve is set such that when the valve is full open at high altitude (that is to say at an altitude above 30000 feet) and at cruising speed, the game is not more tight than an objective game. In one example, this objective game is 0.3 millimeters. This adjustment is made via the valve design and the addition of a diaphragm in the supply pipe if necessary to reduce flow. Following the detection of a transient phase by the detection means 100 (step S25), these detection means 100 set, in a step S30, the transient selection flag TOP52 to the value "1". It can then be determined the duration Dtop having elapsed between

this current iteration of step S25 of setting "1" and the previous iteration of step S25 of setting "1".

The calculating means 110 implement, in a step S35, a conversion law for determining a transient duration Dt in a UN2.PS3 \ function of the parameter N2 ^ S3 and as a function of the derivative T3 of this parameter. Indeed, the parameter makes it possible to estimate the duration during which the game 38 will evolve.

An example of this conversion law is illustrated in Figure 10. x? V2 PS3

This FIG. 10 shows that the higher the parameter T3, the lower the transient duration Dt. Indeed, the higher the parameter t3 is, the longer the game 38 evolution time is short. In addition, FIG. 10 shows that the smaller the variation of parameter T3, the lower the transient duration Dt.

In addition, the calculating means 110 determine, in a step S40, an up-to-date preceding refolding duration Drpa (see FIG. 9). This last updated dropping time Drpa is calculated according to the equation:

Drpa = Drp - Dtop where Drp is a computation time calculated during the previous iteration of a comparison step S45 (described in more detail below).

The calculating means 110 compare, in a step S45, the transient duration Dt obtained in step S35 with the updated preceding retraction time obtained in step S40, and provide a current Dre folding time in according to this comparison. This current downtime is calculated according to the equation:

Dre = max (Dt; Drpa)

An exemplary implementation of step S45 is illustrated in FIGS. 11a and 11b. Figure 11a shows a curve 200 of a duration Dt starting at a time t0 and ending at a time t3. Figure 11a further shows a curve 210 of a duration Drp beginning at a time t1 and ending at a time t2. The time t0 corresponds to a first iteration of the step S30 of setting "1" of the indicator TOP52, said previous iteration. In addition, the instant t1 corresponds to a second iteration of the step S30 of setting "1" of the indicator TOP52, called current iteration. At the instant t1, the calculation means 110 compare (step S45) the remaining Drpa duration of the duration Drp and the duration Dt, and provide a duration Dre equal to the longest duration between Drpa and Dt. In this example, the time t2 being less than the time t3, the duration Dre is equal to the duration Drpa.

FIG. 11b represents a curve 220 of a duration Dt starting at a time t4 and ending at a time t6. FIG. 11b furthermore represents a curve 230 of duration Drp beginning at a time t5 and ending at a time t7. The instant t4 corresponds to a first iteration of the step S30 of setting "1" of the indicator TOP52, referred to as the preceding iteration. In addition, the time t5 corresponds to a second iteration of the step S30 of setting "1" of the indicator TOP52, called current iteration. At time t5, the computing means 110 compare (step S45) the remaining duration Drpa of the duration Drp and the duration Dt, and provide a duration Dre equal to the longest duration between Drpa and Dt. In this example, the time t6 being less than the time t7, the duration Dre is equal to the duration Dt.

Then, the detection means 100 put, in a step S50, the transient selection flag TOP52 to the value "1" during the fallback period Dre.

The steps S35, S40, S45 and S50 enable the detection of the transient phase as long as the game 38 has not finished evolving, as well as the adaptation of the duration Dre to the evolution time of the game 38.

When a transient phase is detected (step S30), the reset means 120 checks, in a step S55, whether the following conditions are satisfied:

where S6 is a sixth predetermined threshold and S7 is a seventh predetermined threshold. In one example, the sixth threshold S6 is equal to 30000 feet. In one example, the seventh threshold S7 is 40 rpm.bar/K.

If the preceding conditions are satisfied, the reset means 120 record, in a step S60, the first value VI of the parameter for which these conditions are satisfied, as well as the first value V2 of the parameter N2 for which these conditions are verified.

The reset means 120 checks, in a step S65, whether a first zeroing condition and a second zeroing condition are satisfied.

The first zeroing condition is checked when the following inequalities are verified during the entire fourth Dc4 confirmation period.

In one example, the fourth confirmation duration Dc4 is 10 seconds.

The second zeroing condition is checked when the following inequality is satisfied: N2> V2

When the first zeroing condition and the second zeroing condition are true, zeroing means 120

zero, in a step S70, the setback time Dre of the valve 44.

In addition, when the first zeroing condition and the second zeroing condition are satisfied, the detecting means 100 sets, in a step S75, the transient selection flag TOP52 to the value "0".

The steps S55, S60, S65, S70 and S75 make it possible to take into account the case where while a transient phase is detected following a significant change in the parametric --- this parameterized - returns 3 r T3 T3 rapidly to its initial value (that is, the value of the parameter before its significant evolution).

In this case, the temperatures of the parts of the high-pressure turbine 24 do not have time to evolve. The mechanical expansion of the parts of the high-pressure turbine 24 does not occur and the game 38 does not close. It is therefore not necessary to fold the valve 44, and to remain in the transient phase,

The steps S35, S40, S45, S50, S55, S60, S65, S70 and S75 thus allow to remain in the transient phase that the necessary time while keeping a safe behavior.

In a step S80, the calculation means 130 of the control signal SC52 satisfy three conditions (see FIG. 12).

The first condition is checked, in a step s80.1, when the following equality is satisfied: wow = 1

The second condition is satisfied, in a step s80.2, when the following equality and inequality are satisfied during the whole of a fifth confirmation duration Dc5: (WOW = 0 \ dALT - <0 v dt where is the time derivative of ALT. In one example, the fifth confirmation duration Dc5 is 5 seconds.

The third condition is satisfied, in a step s80.3, when the following equality and inequality are satisfied: rWOW = 0 t N2 <S8 where S8 is an eighth predetermined threshold. In one example, the eighth threshold is 14500 rpm.

In a step S85, the calculation means 130 of the control signal SC52 determine the value of the control signal SC52 according to the three preceding conditions.

More precisely, if at least one condition among the first condition, the second condition and the third condition is satisfied, the calculation means 130 select, during the whole duration of folding Dre of the valve 44, the value VR for the signal SC52. Thus, if the control signal SC52 is selected by the selection module 55, the valve 44 is placed in the folded position by the control signal SC52 for a time sufficient for the game 38 to stabilize, this fallback position being defined. so as to allow the injection of hot air on the outer casing 36 to expand it to the maximum. Thus, any contact between the blades and the turbine ring is avoided during the transient phase.

If none of the conditions of the first condition, the second condition and the third condition are satisfied, the calculation means 130 select, during the entire duration of setting Dre of the valve 44, the value VLow for the control signal SC52 . Thus, if the control signal SC52 is selected by the selection module 55, the opening of the valve 44 is reduced, which makes it possible to increase the clearance and thus to protect the mechanism of the valve 44.

Figure 13 shows the management module for high altitude cruise and mounted 53 according to an exemplary embodiment of the invention.

This management module for high altitude cruising and mounted 53 comprises means for detecting 140 a high altitude cruising phase or a climbing phase, and calculation means 150 of the control signal SC53.

The detection means 140 detect a high altitude cruising phase or a climb phase, in a step S100, when all of the conditions of the set including a first high altitude cruising / ascending condition, a second high altitude cruising condition. mounted, a third high altitude cruise / climb condition, and a fourth high altitude cruise / climb condition are verified (see Figure 14).

The first high altitude cruise / climb condition is verified, in a sub-step slOO.l, by the detection means 140 when the following double inequality is verified:

Slow motion <RATING <MCT

Indeed, in the high altitude cruising phase, the RATING parameter is between Idle and MCT.

The second high altitude cruise / climb condition is verified, in a step sl00.2, by the detection means 140 when the following inequality is verified:

Match> 59 where S9 is a ninth predetermined threshold. In one example, the ninth threshold S9 is equal to 0.3.

The third high altitude cruise / climb condition is verified, in a step sl00.3, by the detection means 140 when the following inequality is verified: ALT> 510 where S10 is a tenth predetermined threshold. In one example, the tenth threshold S10 is equal to 15000 feet. The second and third conditions make it possible not to inadvertently detect a high altitude cruise phase or a climb phase.

The fourth high altitude cruise / climb condition is that the aircraft is downhill. This fourth condition is verified in a step sl00.4 by the detection means 140 when the following inequality is verified during a sixth confirmation duration Dc6:

dALT -i- <θ dt

In one example, the sixth confirmation duration Dc6 is 10 seconds. Following the detection of a high altitude cruising phase or an ascending phase by the detection means 140, these detection means 140 put, in a step S10, the selection indicator for a high cruise phase. altitude / climb TOP53 to the value "1".

When the selection indicator for high altitude cruise and climb TOP53 takes the value "1", the calculation means 150 implement, in a step S120, a conversion law to determine a first valve opening parameter Povl. according to the Mach and altitude ALT (see Figure 15).

An example of this conversion law is illustrated by the graph of FIG. 16. This FIG. 16 shows that the higher the altitude ALT, the higher the first parameter Pov1 corresponds to a valve 44 open. From 30000 feet, the value of the first parameter Povl corresponds to a valve 44 open to 100%.

The calculation means 150 determine, in a step S130, a first coefficient C1 as a function of the regime N2. More precisely, the calculation means subtract the current value of the regime N2 from a maximum value of the regime N2, and determine, for example by means of a table, the first coefficient C1 as a function of this subtraction. When the value of this subtraction decreases, the first coefficient C1 becomes equal to 1.

The calculation means 150 determine, in a step S140, a second coefficient C2 as a function of the speed Xnl2r. More precisely, the calculation means subtract the current value of the speed Xnl2r from a maximum value of the speed Xnl2r, and determine, for example, average of a table, the second coefficient C2 as a function of this subtraction. When the value of this subtraction decreases, the second coefficient C2 becomes equal to 1.

The calculation means 150 determine, in a step S150, a third coefficient C3 as a function of the temperature T3. More precisely, the calculation means subtract the current value of the temperature T3 from a maximum value of the temperature T3, and determine, for example by means of a table, the third coefficient C3 as a function of this subtraction. When the value of this subtraction decreases, the third coefficient C3 becomes equal to 1.

In a step S160, the calculation means 150 calculate a second valve opening parameter Pov2 according to the following equation:

Pov2 = Povl. Cl. C2. C3

The first, second and third coefficients make it possible to ensure that, in the event of maximum acceleration, the vanes 30 do not touch the casing 32.

In a step S170, the calculation means 150 calculate the control signal SC53 according to the following equation: SC53 = Pov2 + Vmin where Vmin is a minimum valve opening value 44.

This minimum value Vmin makes it possible to ensure a minimum opening of the valve 44 during the cruise phase at high altitude or during the climb phase.

The cruise management module 53 has the function of limiting the clearance 38 during the high altitude cruising and climbing to improve the performance of the turbojet engine 10.

FIG. 17 shows a step S180 in which the management module for other stabilized phases 54 according to one embodiment of the invention satisfies three conditions.

The first condition is checked when the following equality is satisfied: WOW = 1

The second condition is satisfied when the following equality and inequality are satisfied during the entire fifth confirmation period: (WOW = 0

. dALT -i- <θ dt where is the time derivative of ALT.

The third condition is satisfied when the following equality and inequality are satisfied: (WCW = 0 t N2 <S8 where S8 is an eighth predetermined threshold. In one example, the eighth threshold is 14500 rpm.

In a step S185, the management module for other stabilized phases 54 determines the value of the control signal SC54 according to the three preceding conditions.

More precisely, if at least one condition among the first condition, the second condition and the third condition is satisfied, the management module for other stabilized phases 54 selects the value VR for the control signal SC54. Thus, if the control signal SC54 is selected by the selection module 55, the valve 44 is placed in the folded position by the command signal SC54, this folding position being defined so as to allow the injection of hot air on the outer casing 36 to expand it to the maximum. Thus, any contact between the blades and the turbine ring is avoided during the other stabilized phases.

If no condition among the first condition, the second condition and the third condition is satisfied, the management module for other stabilized phases 54 selects the value VLow for the control signal SC54. Thus, if the control signal SC54 is selected by the selection module 55, the opening of the valve 44 is reduced, which makes it possible to increase the clearance and thus to protect the mechanism of the valve 44.

Fig. 18 shows the selection module 55 according to an exemplary embodiment. This module comprises a module 160 and a selector 170.

The module 160 determines a selection signal S160, as a function of the indicators TOP51, TOP52 and TOP53. These indicators are representative of the operating speed of the turbojet and in particular of the current flight phase of the aircraft. The selection signal Siôo indicates to the selector 170 which control signal it must select, according to the following Table II:

Table II

Thus, in the control module 50, each of the management modules 51, 52 and 53 determines a control signal that is suitable for a particular situation. In addition, each of the management modules 51, 52, 53 and 54 determines a selection indicator making it possible to choose which of the control signals is most appropriate given the current operating speed of the turbojet engine.

Claims

A control unit (46) for controlling a clearance (38) between blade tips (30) of a turbine rotor of a gas turbine engine engine and a turbine ring ( 34) of a housing (32) surrounding the blades, the control unit (46) comprising a control module (50) configured to determine a control signal (SC50) of at least one valve (44) for acting on a flow rate and / or an air temperature directed to the housing (32), said control module (50) comprising: - a take-off management module (51) configured to provide a first control signal (SC51) and a first selection indicator (TOP51) associated with a take-off phase, - a transient management module (52) configured to provide a second control signal (SC52) and a second selection indicator (TOP52) associated with a phase transient, and - a high altitude cruise management module (53) configured to provide a third communication signal ande (SC53) and a third selection indicator (TOP53) associated with a high altitude cruise phase or a climb phase, said control unit being characterized in that said control module (50) further comprises: - a a management module for stabilized phases other than high altitude cruising and climb (54), configured to provide a fourth control signal (SC54) associated with the stabilized phases other than the high altitude cruising and the climb, - a selection module of a a control signal (55) configured to select said control signal (SC50) from the first, the first, the second and the fourth control signals (SC51, SC52, 5Cs3, SC54) based on the first, second and third indicators of selection (TOP51, TGPS2j TOP53).

2. Control unit according to claim 1, in which the second selection indicator (TOP52) is determined as a function of a pressure (Ps3), a speed (N2) of engine operation, a temperature (T3 ), and an altitude (ALT).

The control unit according to claim 1, wherein the transient management module (52) configured to further provide a transient duration (Dt) as a function of: a parameter calculated according to the formula N2.PS3 T3 where N2 is the operating speed of the engine, PS3 is a pressure and T3 is a temperature, and - the derivative of said parameter.

4. Control unit (46) according to one of claims 1 to 3, wherein the first selection indicator (TOP51) is determined according to a management parameter of a thrust instruction applied to the engine (RATÎNG) and an indicator (WOW) of the aircraft on the ground.

5. Control unit according to claim 1, wherein the takeoff management module (53) comprises means (70) for verifying the stability of a running speed of the engine (N2).

6. Control unit according to claim 1, in which the third control signal (SC53) is determined as a function of a speed (Mach) of the aircraft, an altitude (ALT), a first speed ( N2) of operation of the engine, a second engine operating speed (Xnl2r) and a temperature (T3),

7. A gas turbine engine engine comprising a control unit according to one of claims 1 to 6 and at least one valve for acting on a flow rate and / or an air temperature directed towards the housing (32), wherein said valve (44) is controlled according to said control signal (SC50).

8, method for controlling a clearance (38) between blade tips (30) of a turbine rotor of a gas turbine engine engine and a turbine ring (34) of a crankcase (32) surrounding said vanes, said method being implemented by a control unit (46) and comprising determining a control signal (SCso) of at least one valve (44) to act on a rate and / or an air temperature directed towards the housing (32), said method being characterized in that it comprises, for determining the control signal (SC5o): a step of supplying a first control signal (SC5i) and a step of providing a first selection indicator (TOP5 ·) associated with a take-off phase, - a step of providing a second control signal (SC52) and a step of providing a second selection indicator (TOP52) associated with a transient phase, - a step of providing a third control signal (SC53) and a step of e providing a third selection indicator (TOP53) associated with a high altitude cruise phase or a climb phase, - a step of providing a fourth control signal (SC54) associated with the stabilized flight phases other than the high altitude cruise and the climb, the control signal (SC50) determined by the control unit being selected from the first, second, third and fourth control signals (SC51, SC52, SC53, SC54) according to first, second and third selection indicators (TOP51, TOP52, TOP53),