The present invention relates to the general field of turbomachines for aircraft.

Prior art

Currently, during take-off of an aircraft which includes a turbomachine which is cold, for example during the first cycle of the turbomachine of the day, a current turbomachine may experience a peak in the temperature of the exhaust gases.

In fact, when the turbomachine reaches its take-off thrust, the exhaust temperature of the gases may reach a temperature peak, which contributes to deteriorating the turbomachine. In addition, in order to take this phenomenon into account, a margin is provided between the maximum temperature not to be exceeded and the design temperature at which the turbomachine is intended to operate, this margin negatively impacting the efficiency of the turbomachine.

In addition, this exhaust gas temperature peak phenomenon occurs at each cycle, but is all the more important when the turbomachine is cold.

Disclosure of the invention

The main aim of the present invention is therefore to provide a solution responding to the problem described above.

According to a first aspect, the invention relates to a method of regulating a temperature of the exhaust gases of a turbomachine, the method comprising the following steps:

regulating the injection of fuel into a combustion chamber of the turbomachine so that the turbomachine generates a target thrust;

regulation of the injection of mechanical power by an electric motor on a shaft driven in rotation by a turbine, the electric motor being activated when a clearance between a casing and the blades of the turbine exceeds a threshold value.

The Applicant has in fact noticed that the overheating of the turbomachine is caused by a phenomenon of temporary opening of the clearance at the top of the blades of the turbine, and in particular of the high pressure turbine. The opening of the clearance occurs due to a difference in thermal expansion between the casing and the blades of the turbine. Indeed, the casing of the turbine has a thermal inertia which is generally lower than the thermal inertia of the disks of the turbine. This increase in the clearance between the casing and the top of the turbine blades negatively impacts the efficiency of the turbine, thus leading to an increase in fuel consumption, the increase in fuel consumption causing an increase in the temperature of the gases. exhaust of the turbomachine, at given thrust.

Advantageously, the invention relates to a method of regulating the temperature of the exhaust gases from the turbomachine of an aircraft for a take-off phase of said aircraft.

According to one possible characteristic, the regulation of the injection of mechanical power by the electric motor is carried out by determining an exhaust gas temperature of the turbomachine, the electric motor injecting mechanical power onto the shaft driven in rotation by the engine. turbine when the temperature of the exhaust gases from the turbomachine reaches a predetermined threshold value.

According to one possible characteristic, the injection of mechanical power on the shaft driven in rotation by the turbine is variable as a function of the exceeding of the temperature of the exhaust gases of the turbomachine with respect to the predetermined threshold value. Thus, the injection of mechanical power can be all the greater as the temperature of the exhaust gases from the turbomachine exceeds the predetermined threshold value.

According to one possible characteristic, the temperature of the exhaust gases from the turbomachine is determined from the injection of fuel into the combustion chamber.

According to one possible characteristic, the temperature of the exhaust gases from the turbomachine is determined by measurement with a sensor.

According to one possible characteristic, the regulation of the injection of mechanical power by the electric motor is carried out by determining the clearance between the casing and the blades of the turbine, the electric motor injecting mechanical power onto the shaft driven in rotation by the turbine when the clearance between the casing and the turbine blades reaches the threshold value.

According to one possible characteristic, the injection of mechanical power on the shaft driven in rotation by the turbine is variable as a function of the clearance between the casing and the turbine blades being exceeded with respect to the threshold value. Thus, the injection of mechanical power can be all the greater as the clearance between the casing and the blades of the turbine exceeds the threshold value.

According to one possible characteristic, the clearance between the casing and the blades of the turbine is determined by measurement with a sensor.

According to one possible characteristic, the clearance between the casing and the blades of the turbine is determined from a model constructed from engine parameters measured by the control system. Thus, according to a possible characteristic, the clearance between the casing and the blades of the turbine is determined from a temperature of a temperature of the air in the turbine (the temperature of the stream) and of a temperature of the air in the turbine. turbine housing.

According to another possible characteristic, the clearance between the casing and the blades of the turbine is determined from a temperature of the casing of the turbine and from a temperature of a disk of the turbine.

According to one possible characteristic, the regulation of the injection of mechanical power by the electric motor is carried out by measuring the thrust generated by the turbomachine, the electric motor injecting mechanical power on the shaft driven in rotation by the turbine when the thrust generated by the turbomachine reaches a threshold value.

According to one possible characteristic, the electric motor is activated for a period of between 100 seconds and 400 seconds.

According to a second aspect, the invention relates to a turbomachine for an aircraft comprising:

a turbine which is located downstream of a combustion chamber and which is connected to a shaft, the turbine comprising a casing and a plurality of blades;

- a fuel injection device which is configured to inject fuel into the combustion chamber;

a thrust calculating device which is configured to calculate the thrust generated by the turbomachine;

- an electric motor which is connected to the shaft;

a control system connected to the thrust calculation device, to the fuel injection device and to the electric motor, the control system being configured to implement the method according to any one of the preceding characteristics.

According to one possible characteristic, the turbomachine has a double body and double flow, the turbine being a high pressure turbine and the shaft being a high pressure shaft.

According to a third aspect, the invention relates to an aircraft comprising a turbomachine according to any one of the preceding characteristics.

Brief description of the drawings

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an exemplary embodiment thereof without any limiting nature.

[Fig. 1] FIG. 1 schematically represents a turbomachine for an aircraft.

[Fig. 2] FIG. 2 represents a comparison of the evolution of the temperature of the exhaust gases of a turbomachine of the state of the art and of a turbomachine according to the invention.

Description of the embodiments

FIG. 1 schematically illustrates a turbomachine 1 for an aircraft with a double body and double flow comprising, from upstream to downstream, in the direction of flow of the air flow, a fan 2, a low pressure compressor (LP ) 3, a high pressure compressor (HP) 4, a combustion chamber 5, a high pressure turbine (HP) 6, and a low pressure turbine (LP) 7. However, the invention can be applied to a turbomachine having a different structure.

The high pressure turbine 6 is connected to the high pressure compressor 4 by a high pressure shaft 8, and the low pressure turbine 7 is connected to the low pressure compressor 3 and to the fan 2 by a low pressure shaft 9.

The high pressure turbine 6 comprises a plurality of vanes 61 which are surrounded by a casing 62. The vanes 61 include a top which is situated opposite the casing 62, the apex of the vanes 61 being spaced from said casing 62 by a clearance.

The turbomachine 1 also comprises an electric motor 10 which is connected to the high pressure shaft 8, the electric motor 10 making it possible to drive said high pressure shaft 8. The electric motor 10 can for example be placed in the housing of accessories (AGB or "accessory gearbox" according to the English terminology) of the turbomachine 1. The electric motor 10 can for example be powered by a battery 11.

The turbomachine 1 comprises a fuel injection device 12 which makes it possible to inject the fuel into the combustion chamber 5. The fuel injection device 12 may in particular comprise a pump which is connected to a fuel tank.

The turbomachine 1 also comprises a thrust calculating device 13 which is configured to calculate the thrust generated by the turbomachine 1 during its operation. The thrust generated by the turbomachine 1 can for example be calculated from the rotational speed of the fan 2, the total pressure upstream of the turbomachine 1, the total temperature upstream of the turbomachine 1, and the difference outside air temperature and standard atmosphere (ISA, for “International Standard Atmosphere”). The thrust generated by the turbomachine 1 can also be calculated from the air pressure in the fan 2 and the air pressure in the low pressure turbine 7. Thus,

The turbomachine 1 comprises a control system 14 which is connected to the electric motor 10, to the fuel injection device 12, and to the thrust calculating device 13. The control system 14 can also be connected to the battery 11. The control system 14 thus ensures the control of the electric motor 10 and of the fuel injection device 12, and the control system 14 acquires the thrust calculated by the thrust calculation device 13. According to a possible variant, the electric power necessary for the operation of the electric motor is supplied by an electric source which is located in the aircraft, and therefore outside the turbomachine 1. This electric source in the aircraft can for example be comprise the auxiliary power unit (APU, for " Auxiliary Power Unit ”according to English terminology).

The control system 14 is configured to implement a method of regulating a temperature of the exhaust gases of the turbomachine 1. To do this, the control system 14 can comprise on the one hand a memory on which the method is recorded, and on the other hand a processor in order to execute the process recorded on the memory.

The method for regulating the temperature of the exhaust gases from the turbomachine 1 comprises the following steps:

- regulation of the injection of fuel into the combustion chamber 12 so that the turbomachine 1 generates a target thrust;

regulation of the injection of mechanical power by the electric motor 10 on the high pressure shaft 8, the electric motor 10 being activated when the clearance between the top of the blades 61 and the casing 62 exceeds a threshold value. The threshold value of the clearance may for example be 0.6 mm.

The process steps are carried out simultaneously.

The Applicant has in fact realized that, due to the fact that the clearance between the blades 61 and the casing 62 is too great, and that thus the efficiency of the high pressure turbine 6 decreases, it is preferable to inject mechanical power via the electric motor 10 rather than injecting more fuel into the combustion chamber 5 to compensate for the loss of efficiency.

The regulation method is particularly advantageous for the take-off phase of the aircraft, and even more particularly during the first start-up of the turbomachine of the day. The target thrust value can thus be equal to the take-off thrust.

The injection of mechanical power by the electric motor 10 can be carried out for a period of between 100 seconds and 400 seconds, or alternatively between 100 seconds and 300 seconds, or alternatively between 200 seconds and 300 seconds. The Applicant has in fact realized that the clearance between the casing 62 and the vanes 61 tends to open for a period which can generally reach 400 seconds, the opening of the clearance reaching a peak at the start and gradually decreasing thereafter. .

Such a method can be implemented according to three possible variants.

According to a first possible variant, the fact that the clearance between the blades 61 and the casing 62 is greater than the threshold value is detected by using the temperature of the exhaust gases from the turbomachine 1 (EGT temperature, for “exhaust gas temperature” ). The Applicant has in fact noticed the link between the temperature of the exhaust gases from the turbomachine 1 and the clearance between the blades 61 and the casing 62, an excessively high temperature of the exhaust gases from the turbomachine 1 being due to the overconsumption of fuel caused by the increased clearance between the vanes 61 and the casing 62.

Thus, according to the first variant, the regulation of the mechanical power injection by the electric motor 10 is carried out by the control system 14 by determining the temperature of the exhaust gas from the turbomachine 1, the control system 14 controlling the injection of the mechanical power by the electric motor 10 on the high pressure shaft 8 when the temperature of the exhaust gases from the turbomachine 1 reaches a predetermined threshold value. The regulation of the electric motor 10 by the control system 14 is carried out in a closed loop.

The temperature of the exhaust gases of the turbomachine 1 can be determined from the injection of fuel into the combustion chamber using a physical model which is entered into the control system and which gives the temperature of the exhaust gases. depending on the fuel injected.

The temperature of the exhaust gases from the turbomachine 1 can also be determined by measuring said temperature of the exhaust gases with a sensor

temperature sensor located in the exhaust casing of the turbomachine 1, said temperature sensor being connected to the control system. 14. The temperature sensor can, according to another alternative, be located in a low pressure distributor or at the level of the low pressure distributor. The low pressure distributor is formed by fixed vanes of the low pressure turbine 7.

According to a second possible variant, the regulation carried out by the control system 14 of the injection of mechanical power by the electric motor 10 is carried out by determining the clearance between the casing 62 and the blades 61 of the high pressure turbine 6, the system control 14 activating the injection of mechanical power by the electric motor 10 on the high pressure shaft 8 when the clearance between the casing and the blades of the turbine reaches the threshold value. The regulation of the electric motor 10 by the control system 14 is carried out in a closed loop.

The clearance between the top of the blades 61 and the housing 62 can be determined by means of a sensor installed on the high pressure turbine 6 which measures the distance between the top of the blades 61 and the housing 62.

The clearance between the casing 62 and the vanes 61 can also be determined from an air temperature at the level of the high pressure turbine 6 (the temperature of the duct) and the temperature of the casing 62, thus making it possible to determine the difference in thermal expansion between the disc of the high pressure turbine 6 and the housing 62.

According to another possible solution, the clearance between the blades 61 and the casing 62 can be determined from the temperature of the casing 62 and the temperature of the disc of the high pressure turbine 6, thus making it possible to determine the difference in thermal expansion between the high pressure turbine disc 6 and the housing 62.

According to a third possible variant, the regulation of the mechanical power injection is carried out in an open loop, and not in a closed loop as is the case in the first variant and the second variant. In the third variant, the control system 14 controls the electric motor 10 to inject mechanical power onto the high pressure shaft 8 when the thrust generated by the turbomachine 1 reaches a threshold value.

The injection of mechanical power on the high pressure shaft 8 when the thrust generated reaches a threshold value is carried out according to a profile which is predetermined and which is recorded on the control system 14. According to an advantageous variant, the injection profile mechanical power is based to take into account the worst case, the case in which the efficiency of the turbomachine 1 is negatively impacted by the opening of the clearance between the casing 62 and the blades 61.

Advantageously, the control system 14 activates the electric motor 10 to inject mechanical power when the thrust generated by the turbomachine 1 reaches the target value, and in particular the take-off thrust.

The Applicant has in fact noticed that the play between the casing 62 and the vanes 61 tends to increase at the end of acceleration of the turbomachine 1, the maximum of the play occurring approximately 1 minute after the end of the acceleration.

As can be seen in FIG. 2 which illustrates the difference in the evolution of the temperature of the exhaust gases between a turbomachine of the state of the art and a turbomachine according to the invention, the invention makes it possible to reduce, or even to eliminating the peak temperature of the outlet gases from the turbomachine 1 during the first take-off of the aircraft.

In the embodiment described above, the monitored clearance is the clearance of the high pressure turbine 6 and the electric motor 10 injects mechanical power onto the high pressure shaft 8, however the invention can also be applied to the turbine. low pressure 7, the electric motor 10 injecting mechanical power onto the low pressure shaft 9.

WE CLAIMS

[Claim 1] A method of regulating a temperature of the exhaust gases of a turbomachine (1), the method comprising the following steps:

- regulation of the injection of fuel into a combustion chamber (5) of the turbomachine (1) so that the turbomachine (1) generates a target thrust;

- regulation of the mechanical power injection by an electric motor (10) on a shaft (8, 9) driven in rotation by a turbine (6, 7), the electric motor (10) being activated when a clearance between a casing (62) and blades (61) of the turbine (6, 7) exceeds a threshold value.

[Claim 2] The method of claim 1, wherein the regulation of the injection of mechanical power by the electric motor (10) is performed by determining an exhaust gas temperature of the turbomachine (1), the electric motor ( 10) injecting mechanical power onto the shaft (8, 9) driven in rotation by the turbine (6, 7) when the temperature of the exhaust gases from the turbomachine (1) reaches a predetermined threshold value.

[Claim 3] A method according to claim 2, wherein the temperature of the exhaust gas from the turbomachine (1) is determined from the injection of fuel into the combustion chamber (5).

[Claim 4] The method of claim 3, wherein the temperature of the exhaust gas from the turbomachine (1) is determined by measurement with a sensor.

[Claim 5] The method of claim 1, wherein the regulation of the injection of mechanical power by the electric motor (10) is performed by determining the clearance between the housing (62) and the blades (61) of the turbine ( 6, 7), the electric motor (10) injecting mechanical power onto the shaft (8, 9) driven in rotation by the turbine (6, 7) when the clearance between the housing (62) and the vanes (61 ) of the turbine (6, 7) reaches the threshold value.

[Claim 6] A method according to claim 5, wherein the clearance between the housing (62) and the blades (61) of the turbine (6, 7) is determined by measurement with a sensor.

[Claim 7] A method according to claim 5, wherein the clearance between the casing (62) and the blades (61) of the turbine (6, 7) is determined from a temperature of the air in the turbine ( 6, 7) and a temperature of the casing (62) of the turbine (6, 7).

[Claim 8] The method of claim 5, wherein the clearance between the casing (62) and the vanes (61) of the turbine (6, 7) is determined from a temperature of the casing (62) of the turbine. (6, 7) and a temperature of a turbine disk (6, 7).

[Claim 9] The method of claim 1, wherein the regulation of the injection of mechanical power by the electric motor (10) is carried out by measuring the thrust generated by the turbomachine (1), the electric motor (10) injecting the mechanical power on the shaft (8, 9) driven in rotation by the turbine (6, 7) when the thrust generated by the turbomachine (1) reaches a threshold value.

[Claim 10] Turbomachine (1) for an aircraft comprising:

- a turbine (6, 7) which is located downstream of a combustion chamber (5) and which is connected to a shaft (8, 9), the turbine (6, 7) comprising a housing (62) and a plurality of vanes (61);

- a fuel injection device (12) which is configured to inject fuel into the combustion chamber (5);

- a thrust calculating device (13) which is configured to calculate the thrust generated by the turbomachine (1);

- an electric motor (10) which is connected to the shaft (8, 9);

- a control system (12) connected to the thrust calculation device (13), to the fuel injection device (12) and to the electric motor (10), the control system (12) being configured to implement the method according to any one of claims 1 to 9.

[Claim 11] A turbomachine (1) according to claim 10, in which the turbomachine (1) has a double body and double flow, the turbine (6) being a high pressure turbine and the shaft (8) being a high shaft. pressure.

[Claim 12] An aircraft comprising a turbomachine (1) according to any one of claims 10 or 11.