FR3064670A1 - ELECTRIC PRODUCTION INSTALLATION WITH FREE TURBINE - Google Patents

Abstract

The invention relates to an electrical production plant (10) for an aircraft comprising a gas generator (12), a free turbine (20) driven in rotation by the gas flow generated by the gas generator and an electric generator (14). coupled to the free turbine. The invention further comprises a speed sensor (34) for measuring the rotational speed of the free turbine, an electrical module (38) for adjusting the resistive torque applied by the stator (18) to the rotor (16). ) of the electric generator (14) and a control device (36) of the electrical module configured to control the electric module according to the speed of rotation of the free turbine.

Description

(57) The invention relates to an electrical production installation (10) for aircraft comprising a gas generator (12), a free turbine (20) rotated by the gas flow generated by the gas generator and an electric generator. (14) coupled to the free turbine. The invention further comprises a speed sensor (34) for measuring the speed of rotation of the free turbine, an electrical module (38) for adjusting the resistive torque applied by the stator (18) to the rotor (16 ) of the electric generator (14) and a control device (36) of the electric module configured to control the electric module as a function of the speed of rotation of the free turbine.

Invention background

The present invention relates to the field of auxiliary power sources for aircraft such as airplanes, helicopters or any other type of flying object.

Auxiliary single-shaft power generators for aircraft are known, comprising a gas generator whose shaft directly rotates the rotor of an electric generator.

Traditionally, the gas generator comprises at least one compressor and one turbine which are linked in rotation on the same shaft, the turbine being then said to be linked. The operating principle is as follows: the fresh air entering the compressor is compressed due to the rotation of the compressor before being sent to a combustion chamber where it is mixed with a fuel. The burnt and expanded gases due to the combustion are then discharged at high speed to the linked turbine.

There is then a transfer of the power of the expanded gases to the linked turbine, restored in the form of a mechanical torque on the shaft, one part of which keeps the compressor in rotation and the other part of which allows drive a receiving member, such as the rotor of a helicopter or the rotor of an electric generator.

However, this distributed use of the torque does not allow an optimization of the fuel consumption and, consequently, does not offer a good yield.

Subject and summary of the invention

An object of the present invention is to provide an electrical production installation for an aircraft, overcoming the aforementioned drawbacks and in particular making it possible to meet the needs of the aircraft in electrical energy while improving the efficiency of the production of electrical energy.

To do this, the invention relates to an electrical production installation for an aircraft having an electrical network, said electrical production installation comprising:

• a gas generator;

• a free turbine driven in rotation by a gas flow generated by the gas generator, the free turbine having a shaft;

• an electric generator comprising a stator electrically connected to the electrical network and a rotor driven in rotation by the shaft of the free turbine, the stator applying a resistive torque to the rotor of the electric generator;

• a speed sensor to measure the speed of rotation of the free turbine;

• an electric module for adjusting said resistive torque applied to the rotor of the electric generator, the electric module being connected to the stator of the electric generator; and • an electrical module control device configured to control the electrical module as a function of the speed of rotation of the free turbine measured by the speed sensor.

The gas generator includes a compressor and a linked turbine. The linked turbine of the gas generator does not absorb all the kinetic energy of the burnt gases and the excess kinetic energy corresponds to the flow of gas generated by the gas generator.

The latter therefore supplies kinetic energy to the free turbine so that there is a second expansion in the free turbine which transforms this kinetic energy into mechanical energy in order to drive the shaft of the free turbine in rotation.

According to the invention, the shaft of the free turbine is coupled to the rotor of the electric generator, so that the latter is also rotated during the operation of the gas generator. This allows the electric generator to transform the mechanical energy of rotation, coming from the shaft of the free turbine, into electrical energy in order to supply the electrical network of the aircraft.

It is therefore understood that the shaft of the free turbine is not connected to the shaft of the gas generator.

The electric generator is here electrically connected to the electrical network of the aircraft so that the installation according to the invention is particularly suitable for airplanes, in which it is necessary to use auxiliary electrical energy production devices to provide for the high electricity requirements of the device.

By electrical network is meant all of the electrical devices of the aircraft, capable of consuming electrical energy and being connected to each other. The electrical network may include, for example, the main engine of the aircraft, various actuators or the heating or lighting circuits of the aircraft.

The electric generator takes part of the kinetic energy of rotation on the shaft of the free turbine. Also, a resistive torque is applied by the stator on the rotor of the electric generator and therefore indirectly by the stator of the electric generator on the shaft of the free turbine. This resistive torque is oriented opposite to the direction of rotation of the rotor of the electric generator and that of the shaft of the free turbine.

The electric generator being electrically connected to the electrical network of the aircraft, it is subjected to load variations which may appear on said electrical network.

The inventors have found that the low inertia of the assembly constituted by the free turbine, its shaft and the electric generator implies that an abrupt variation in the electrical energy demand of the electric network on the electric generator leads to a strong variation in the resistive torque. applied to the rotor of the electric generator. These variations have the consequence of significantly increasing or reducing the speed of rotation of the free turbine.

In this situation, the speed of rotation of the free turbine is no longer controlled while it is necessary to make it tend quickly to its nominal value.

Subsequently, the term “nominal speed” of rotation of the free turbine will refer to a predetermined ideal rotation speed of the free turbine, guaranteeing its optimum efficiency and a production of electrical energy by the electric generator sufficient to provide for the electrical demand, during normal operation of the electrical production installation, i.e. without incidents.

Thus, when the demand for electrical energy on the electrical generator suddenly drops, for example in the event of a breakdown on the electrical network of the aircraft, the resistive torque applied by the stator to the rotor of the electrical generator and therefore to the shaft. of the free turbine decreases sharply and the free turbine then has an excessive speed of rotation. In other words, the free turbine goes into overspeed, which is liable to damage it.

Conversely, when the demand for electrical energy increases suddenly, the resistive torque applied by the stator to the rotor of the electric generator increases and the free turbine is braked too much, causing the gas generator and the turbine to overheat. free, which can also damage them.

It is understood that, according to the invention, the speed sensor makes it possible to supply the control device with an instantaneous value of the speed of rotation of the free turbine. Depending on this instantaneous speed value, the electric module is controlled by the control device so as to adapt the resistive torque applied to the rotor of the electric generator according to the measured speed, in order to control the speed of rotation. of the free turbine. The invention therefore makes it possible to reduce the speed of rotation of the free turbine to its nominal value.

In other words, the invention makes it possible to quickly control the speed of rotation of the free turbine, by acting directly on the shaft of said free turbine and no longer solely by adjusting the flow of fuel injected into the combustion chamber of the gas generator. . This allows efficient management of electrical energy production and fuel consumption. The efficiency of the installation is therefore improved. As fuel consumption is reduced, the impact on the environment is reduced. In addition, the overspeed of the turbine in the event of a power grid failure is notably contained.

Preferably, and in a nonlimiting manner, in the event of a large variation in the demand for electrical energy and therefore in the resistive torque applied by the stator to the rotor of the electric generator, a setpoint can be sent to the gas generator in order to adapt the fuel supply to the combustion chamber, so as to restore the speed of rotation of the free turbine to its nominal value.

In this situation, the invention makes it possible to immediately control the speed of rotation of the free turbine before the generator reaches the new adequate operating speed, after which the management of the speed of rotation of the free turbine is regulated by increase or reduction in the flow of fuel injected.

Advantageously, the control device is configured to control the electrical module according to a first control mode in which the electrical module acts as an electrical load or according to a second control mode in which the electrical module acts as an energy source electric.

The term “electrical charge” is understood here to mean any component or device electrically connected to a circuit and capable of consuming electrical energy. In other words, the electrical charge is a consumer of electrical energy.

An interest is to overcome the two incidents that can occur: a sudden fall or a sudden increase in the demand for electrical energy on the electric generator.

In the event of a sudden drop in demand for electrical energy caused, for example, by a breakdown in the aircraft's electrical network, the speed sensor measures an increase in the speed of rotation of the free turbine, due to a reduction in the resistive torque applied to the rotor of the electric generator. The electrical module is then controlled according to the first control mode, in which it is configured to behave like an electrical load connected to the stator of the electric generator.

In other words, according to the first control mode, everything happens as if we had electrically connected to the electric generator a component intended to consume part of the electric energy which it supplies and thus compensate for the low demand of the network. electric into electric energy. This results in an increase in the resistive torque, which makes it possible to limit the increase in the speed of rotation of the free turbine, to stabilize the speed of rotation of the free turbine, or even to brake the free turbine.

Conversely, in the case of a sudden increase in the demand for electrical energy caused, for example, by a significant acceleration of the aircraft's electric motors or by the activation of electrical circuits, for example the heating or lighting, the speed sensor measures a decrease in the speed of rotation of the free turbine, due to an increase in the resistive torque applied to the rotor of the electric generator. The electrical module is then controlled according to the second control mode, in which it is configured to behave like a source of electrical energy.

In other words, according to the second control mode, everything takes place as if one had electrically connected to the electric generator a component intended to bring a quantity of additional electric energy to the electric network, adding to that provided by the electric generator, to assist the latter. This results in a reduction in the resistive torque, which makes it possible to limit the reduction in the speed of rotation of the free turbine, to stabilize the speed of rotation of the free turbine or even to accelerate the free turbine.

Advantageously, in the first control mode, the electrical module acts as an electrical charge when the measured rotational speed of the free turbine is greater than a first predetermined high threshold, in order to increase the resistive torque applied to the generator rotor. electric.

It is understood that when the speed of rotation of the free turbine, measured by the speed sensor, is greater than the first high threshold, and therefore that the free turbine is in an overspeed situation, the control device is configured to control the electrical module so that it acts as an electrical charge, i.e. as a consumer of electrical energy. In this way, the resistive torque applied by the stator to the rotor of the electric generator and therefore to the shaft of the free turbine increases. This has the effect of limiting the increase in the speed of rotation of the free turbine, preferably stabilizing it, more preferably, braking the free turbine. The speed of rotation of the free turbine is thus reduced in a controlled manner.

Preferably, the control of the electrical module according to the first control mode is accompanied by a reduction in the speed of the gas generator. The first control mode can therefore, for example, make it possible to control the speed of rotation of the free turbine until the gas generator reaches the new speed, takes over and behaves again autonomously.

The first predetermined high threshold may be, for example, a speed value above which bringing the speed of rotation of the free turbine back to its nominal level would involve reducing the flow of fuel injected and would be likely to cause the extinction of combustion in the chamber of the gas generator. The first high threshold may for example correspond to a speed of rotation of the free turbine equal to 105% of the nominal speed of rotation of the free turbine. The first high threshold can be adjusted according to the conditions of use. The electrical module acts as an electrical charge until a speed of rotation of the free turbine is lower than the first high threshold and / or until the new regime of the gas generator is put in place.

In particular, by controlling the electrical module, according to the first control mode, beyond the first predetermined high threshold, the risk of an inadvertent extinction of combustion in the chamber of the gas generator is avoided and therefore the unavailability of the auxiliary power source, during a re-ignition period of the gas generator. Also, exceeding the first high threshold indicates an accidental and flagrant increase in the speed of rotation of the free turbine.

Preferably, the electrical module acting as an electrical charge comprises at least one heating resistor. The advantage is to use an inexpensive electric charge, capable of rapidly consuming a quantity of energy by the Joule effect, the quantity of energy consumed being conditioned in particular by the choice of the value of the resistance. Without departing from the scope of the invention, the electrical module may include a variable heating resistance, a resistance bank or any other device making it possible to consume energy by the Joule effect. This heating resistor can for example be used to heat the passenger compartment of the aircraft.

Preferably, the gas generator comprises a compressor and said at least one heating resistor is disposed at the outlet of the compressor to increase the temperature of the compressed air leaving the compressor. One thus cleverly uses the caloric energy produced by the electric charge in order to heat the compressed air. This increase in temperature improves the thermodynamic characteristics of the combustion chamber, which reduces the fuel consumption necessary for the operation of the gas generator.

According to a particularly advantageous aspect, the electrical module acting as an electrical charge comprises at least one device for storing electrical energy, preferably a super capacity. In addition to allowing the reduction of the speed of rotation of the free turbine, another advantage is to be able to store part of the energy supplied by the electric generator and to store this electric energy for later use. This accumulated electrical energy can be reused, for example, by the electrical devices of the aircraft when they need this electrical energy.

Without limitation, the storage device can also be a battery, a capacitor or any other component capable of storing and restoring electrical energy.

In the first control mode, the storage device functions as a receiver, that is to say that it accumulates electrical energy.

Advantageously, in the second control mode, the electrical module acts as a source of electrical energy when the measured rotation speed of the free turbine is less than a predetermined low threshold, in order to reduce the resistive torque applied to the rotor of the electric generator.

It is understood that when the speed of rotation of the free turbine is less than the low threshold, a control order is transmitted by the control device to the electrical module, so that it acts as a source of electrical energy, so as to provide additional electrical energy to the electrical network making it possible to limit the amount of electrical energy to be taken from the electrical generator to meet the demand for electrical energy from the electrical network of the aircraft. The resistive torque applied by the stator to the rotor of the electric generator and therefore to the shaft of the free turbine decreases. This limits the fall in the speed of rotation of the free turbine in a controlled manner.

The predetermined low threshold may for example be a speed of rotation value below which the free turbine drives the rotor of the electric generator at a speed of rotation insufficient to produce electrical energy guaranteeing the proper functioning of the aircraft and of its electrical devices. Preferably, in order to assist the electric generator, the control of the electric module according to the second control mode is accompanied by an increase in the speed of the gas generator.

Below the low threshold, the electrical module acts as a source of electrical energy, for example until a speed of rotation of the free turbine is greater than the low threshold and / or until the installation of the new gas generator regime.

The low threshold may for example correspond to a speed of rotation of the free turbine equal to 80% of the nominal speed of rotation of the free turbine.

In addition, this control of the speed of rotation of the free turbine, using the electrical module acting as a source of electrical energy, makes it possible, in parallel, to slowly increase the speed of the gas generator. This prevents overfueling and overheating of the gas compressor, while reducing fuel consumption.

In a particularly advantageous manner, the electrical module acting as a source of electrical energy comprises said at least one device for storing electrical energy. It is understood that said at least one storage device restores all or part of the electrical energy which it has stored during a situation of excessive speed of the free turbine, in order to relieve the electric generator and limit the resistive torque. Said at least one storage device therefore operates as an electrical source supplying the electrical network of the aircraft.

In other words, said at least one storage device acts as an electrical charge, in the first control mode, or as a source of electrical energy, in the second control mode. This versatility allows the adjustment of the resistive torque applied to the rotor of the electric generator, according to the speed of rotation of the free turbine, using the storage device, whereby the number of components necessary for regulating the speed of rotation of the free turbine.

Furthermore, the control device makes it possible to maintain the charge of said at least one storage device at an intermediate level, so that its charge is not insufficient to supply electrical energy when it acts as a source of electrical current. , and so that it is not fully charged when caused to act as an electric charge.

The invention also relates to a method for regulating the speed of rotation of the free turbine of the electrical production installation according to the invention, comprising a gas generator, a free turbine having a shaft, an electric generator comprising a rotor. and a stator, an electric module for adjusting the resistive torque applied to the rotor of the electric generator, electrically connected to the stator of the electric generator, a device for controlling the electric module and a speed sensor of the free turbine, process in which:

• the rotational speed of the free turbine is measured using the speed sensor;

• the resistive torque applied by the stator to the rotor of the electric generator, connected to the shaft of the free turbine, is adapted as a function of the speed of rotation of the free turbine measured by the speed sensor.

Preferably, the electrical module is controlled according to a first control mode, so that it acts as an electrical charge, or according to a second control mode so that it acts as a source of electrical energy.

According to a first mode of implementation, when the speed of rotation of the free turbine, measured by the speed sensor, is greater than a first high threshold and is less than a second high threshold, the electrical module is controlled according to the first mode control so as to increase the resistive torque applied by the stator to the rotor of the electric generator.

The first high threshold can be, for example, a predetermined speed value above which reducing the speed of rotation of the free turbine to its nominal value would involve reducing the flow of fuel injected and would be likely to cause the gas generator chamber shutdown. This threshold can be equal for example to 105% of the nominal rotation speed of the free turbine.

According to a second embodiment, when the speed of rotation of the free turbine, measured by the speed sensor, is greater than a second high threshold:

• the electric module is controlled according to the first control mode, so as to increase the resistive torque applied by the stator to the rotor of the electric generator;

• the operation of the gas generator is interrupted.

The second high threshold can be, for example, a predetermined speed value above which the free turbine can be destroyed, for example 110% of the nominal speed of the free turbine. By interrupting the operation of the gas generator, the speed of rotation of the free turbine is reduced more quickly and the risk of damage is limited.

According to a third embodiment, when the speed of rotation of the free turbine, measured by the speed sensor, is less than a low threshold, the electrical module is controlled according to the second control mode, so as to reduce the resistive torque applied to the rotor of the electric generator.

As mentioned above, the low threshold may be, for example, a predetermined speed value below which the free turbine drives the rotor of the electric generator at a speed of rotation insufficient to produce the electrical energy guaranteeing the proper functioning of the aircraft and its electrical devices, for example 80% of the nominal speed of rotation of the free turbine.

Brief description of the drawings

The invention will be better understood on reading the following description of exemplary embodiments of the invention given by way of nonlimiting examples, with reference to the appended drawings, in which:

- Figure 1 illustrates an electrical production installation according to the invention, in which the electrical module is controlled according to a first control mode;

- Figure 2 illustrates an electrical production installation according to the invention, in which the electrical module is controlled according to a second control mode;

- Figure 3A illustrates an ascending step of the demand for electrical energy on the electric generator;

- Figure 3B illustrates the evolution of the resistive torque applied to the stator of the electric generator in response to the ascending level of the demand for electric energy on the electric generator;

- Figure 3C illustrates revolution of the speed of rotation of the free turbine in response to the ascending step of the demand for electrical energy on the electric generator;

- Figure 3D illustrates the evolution of the power supplied by the gas generator in response to the ascending level of the demand for electric energy on the electric generator;

- Figure 4A illustrates a descending step of the demand for electrical energy on the electric generator;

- Figure 4B illustrates the evolution of the resistive torque applied to the stator of the electric generator, in response to the downward step of the demand for electric energy on the electric generator;

- Figure 4C illustrates the speed of rotation of the free turbine in response to the downward step of the demand for electrical energy on the electric generator; and

- Figure 4D illustrates the evolution of the power supplied by the gas generator in response to the downward step of the demand for electric energy on the electric generator.

Detailed description of the invention

FIG. 1 represents an electrical production installation 10 for an aircraft, called an auxiliary power unit, comprising a gas generator 12, an electric generator 14 comprising a rotor 16 and a stator 18, and a free turbine 20 capable of being driven in rotation by a gas flow F generated by the gas generator 12.

The gas generator comprises a rotary shaft 22 on which are mounted a centrifugal compressor 24 and a linked turbine 26, as well as a combustion chamber 28 disposed between the centrifugal compressor 24 and the linked turbine 26.

Fresh air is admitted into the enclosure of the gas generator 12, then is compressed by the centrifugal compressor 24 which discharges it towards the combustion chamber 28 in which it is mixed with fuel.

In the figures, the air and gas flows are represented by empty arrows while the solid arrows schematize the electrical consumption.

The combustion which takes place in the combustion chamber 28 causes the burnt gases to be evacuated at high speed to the linked turbine 26, which has the effect of rotating the shaft 22 of the gas generator 12 and, consequently, , the centrifugal compressor 24. The gas generator 12 therefore operates autonomously.

The speed of rotation of the shaft 22 of the gas generator 12 is determined by the flow of fuel entering the combustion chamber 28.

Despite the extraction of kinetic energy by the linked turbine 26, the gas flow F leaving the gas generator 12 has significant kinetic energy.

As can be understood with the help of FIG. 1, the gas flow F is directed towards the free turbine 20 which has the effect of causing an expansion in the free turbine 20 leading to the rotation of said free turbine.

The free turbine 20 has a shaft 30 which is coupled to the rotor 16 of the electric generator 14, so as to transmit the rotational movement of the free turbine to the rotor of the electric generator. The latter transforms the mechanical energy of rotation into electrical energy which it delivers in particular to the electrical network 32 of the aircraft.

In addition, a reduction gear 31 is placed between the shaft 30 of the free turbine 20 and the rotor 16 of the electric generator to adapt the speed of rotation of the rotor 16 relative to the speed of rotation of the shaft 30.

The installation also includes a speed sensor 34, for measuring the speed of rotation of the shaft 30 of the free turbine 20. The speed sensor 34 transmits the instantaneous measured speed value to a control device 36.

The control device 36 controls the distribution and consumption of the energy supplied by the electric generator.

The stator 18 of the electric generator applies a resistive torque C to its rotor 16 and therefore indirectly to the shaft 30 of the free turbine 20. This resistive torque opposes the rotational movement of the free turbine and therefore tends to slow it down .

It is also known that the demand for electrical energy, for example that of the electrical network 32, may be caused to increase or drop suddenly. In which case, the resistive torque C can respectively increase or decrease significantly, which results in a decrease or an increase in the speed of rotation of the free turbine.

20.

According to the invention, when the speed of rotation of the free turbine, measured by the speed sensor 34, is greater than a first high threshold or less than a low threshold, the control device 36 is configured to control an electrical module 38 for adjusting the resistive torque C applied to the rotor 16 of the electric generator 14. The electric module 38 is electrically connected to the stator 18 of the electric generator 14. The first high threshold corresponds, for example, to a rotation speed of the free turbine, measured by the speed sensor, equal to 105% of the nominal speed of rotation of the free turbine 20. The low threshold corresponds, for example, to a speed of rotation of the free turbine, measured by the speed 34, equal to 80% of the nominal speed of rotation of the free turbine.

In the event of a sudden drop in the demand for electrical energy caused, for example, by a breakdown in the electrical network 32 of the aircraft, the resistive torque C applied to the rotor of the electric generator decreases, as a result of which the free turbine tends to start suddenly in overspeed. Thanks to the invention, when the speed of rotation of the free turbine is greater than the first high threshold, the electrical module 38 is controlled, according to a first control mode, so as to behave like an electrical load connected to the stator 18 of the electric generator.

An electrical production installation 10 provided with an electrical module 38 controlled according to this first control mode is shown in FIG. 1. The electrical module 38 consumes part of the electrical energy supplied by the electrical generator 14, so as to increase the resistive torque on the rotor 16 of the electric generator 14, which has the consequence of limiting the increase in the speed of rotation of the free turbine 20 and, preferably, of braking the free turbine 20.

In the nonlimiting example of FIG. 1, the electrical module is composed of a pair of heating resistors 40, arranged at the outlet of the compressor 24 and of a storage device 42, such as a super-capacity.

The heating resistors 40 and the storage device 42 constitute electrical charges intended to consume part of the electrical energy supplied by the electric generator 14 and therefore to consume part of the kinetic energy of the shaft 30 of the free turbine. 20. The resistors 40 and the storage device 42 thus make it possible to increase the resistive torque C on the rotor of the electric generator, which makes it possible to limit the increase in the speed of rotation of the free turbine 20. Preferably, the resistors make it possible to stabilize the speed of rotation of the free turbine, more preferably, they make it possible to brake the free turbine 20.

In this example, when the speed of rotation of the free turbine 20 is greater than a second high threshold, for example equal to 110% of the nominal speed of rotation of the free turbine, the operation of the gas generator 12 is interrupted, so as to reduce the speed of rotation of the free turbine 20.

The heating resistors 40 make it possible to consume the electrical energy of the electric generator by the Joule effect. In addition, the storage device 42 operates here in receiver mode, that is to say that it stores the electrical energy supplied by the electric generator 14.

In this example, the storage device 42 is a super-capacity that can very quickly store the electrical energy supplied by the electric generator.

Conversely, in the case of a sudden increase in the demand for electrical energy caused, for example, by a significant acceleration of the aircraft's electric motors or by the activation of cabin heating, air conditioning or even the lighting, the electrical module 38 is controlled according to a second control mode, so as to act as a source of electrical energy.

FIG. 2 represents the electrical production installation 10 according to the invention, in which the electrical module 38 is controlled according to the second control mode. It will be understood that the electrical module 38 is controlled according to the second control mode in response to a high demand for electrical energy, for example from the electrical network 32 of the aircraft on the electrical generator 14.

In this example, the electrical module 38 is controlled according to the second control mode by the control device 36 when the speed of rotation of the free turbine 20, measured by the speed sensor 34, is less than a predetermined low threshold.

According to the invention, the electrical module 38 will provide additional electrical energy, in addition to that provided by the electrical generator 14 so as to assist it and limit the amount of electrical energy taken from said electrical generator. This has the consequence of limiting or reducing the resistive torque applied by the stator 18 on the rotor 16 of the electric generator 14 and therefore in limiting the deceleration of the free turbine.

In the example of FIG. 2, representing the second control mode, the electrical module comprises the storage device 42 described above, for example the super capacity, which was recharged during a situation of excessive speed of the free turbine 20.

The storage device 42 then operates in generator mode, that is to say that it restores the electrical energy that it has previously stored. This additional electrical energy makes it possible to meet a significant demand for electrical energy from the electrical network 32. This limits the electrical energy taken from the electric generator 14, limits the resistive torque applied to the shaft 30 of the free turbine 20 and limits the braking and the reduction in the speed of rotation of the free turbine 20.

In FIGS. 1 and 2, the small arrows represent a low consumption or a low supply of electrical energy. The arrows of medium size schematize a consumption or an average contribution in electrical energy and the arrows of large size schematize a high consumption or a significant contribution in electrical energy.

FIGS. 3A to 3D illustrate, without limitation, the evolution of the resistive torque of the stator 18, of the speed of rotation of the free turbine 20 and of the power supplied by the gas generator 12, in response to an ascending step of the electrical energy demand on the electric generator, so that:

• in the graph in FIG. 3A, there is an ascending step in the demand for electrical energy, reflecting a sudden increase in said demand for electrical energy by the electrical network 32 of the aircraft on the electric generator, as a function of time;

• in the graph in FIG. 3B, the evolution, as a function of time, of the resistive torque applied by the stator 18 on the rotor 16 of the electric generator is observed, in response to the ascending level of the demand for electrical energy ;

• in the graph in FIG. 3C, the evolution, as a function of time, of the speed of rotation of the free turbine 20 is observed, in response to the ascending step of the demand for electrical energy; and • on the graph of FIG. 3D, the evolution, as a function of time, of the power supplied by the gas generator 12 is observed, in response to the ascending level of the demand for electrical energy. Furthermore, FIGS. 4A to 4D illustrate, without limitation, the evolution of the resistive torque of the stator 18, of the speed of rotation of the free turbine 20 and of the power supplied by the gas generator 12, in response to a downward step in the demand for electrical energy on the electric generator, so that:

• in the graph in FIG. 4A, there is a descending step in the demand for electrical energy, reflecting a sudden drop in said demand for electrical energy, by the electrical network 32 of the aircraft on the electric generator, as a function of time ;

• in the graph in FIG. 4B, the evolution, as a function of time, of the resistive torque applied by the stator to the rotor of the electric generator is observed, in response to the descending level of the demand for electrical energy;

• in the graph in FIG. 4C, the evolution, as a function of time, of the speed of rotation of the free turbine is observed, in response to the downward step in the demand for electrical energy; and • on the graph of FIG. 4D, the evolution, as a function of time, of the power supplied by the gas generator 12 is observed, in response to the descending step of the demand for electrical energy. It will be noted that the power of the gas generator 12 is regulated so as to cause the speed of rotation of the free turbine 20 to tend towards its nominal value.

The curves shown in the graphs of FIGS. 3A to 3C and 4A to 4C have the sole purpose of showing, schematically, an overall trend illustrating the behavior of an electrical production installation according to the invention.

The electrical energy demand of the graphs of FIGS. 3A and 4A was chosen arbitrarily so that it presents an initial energy demand at time t ₀ , then describing, in ti, respectively an ascending and descending step of the request, until a stabilized speed is obtained at an instant t2, for which the speed of rotation of the free turbine 20 returns to its nominal value, thanks in particular to the power supplied by the gas generator 12.

In the graphs of FIGS. 3B and 4B, the curves C1 in fine lines represent the evolution of the resistive torque applied by the stator 18 on the rotor 16 of the electric generator 14 for an electrical production installation 10 in which the resistive torque n ' is not adjusted. Note that the unadjusted resistive torque follows the evolution of the demand for electrical energy abruptly. When the demand for electrical energy increases, the unadjusted resistive torque increases and vice versa.

The curves C2 in bold in the graphs of FIGS. 3B and 4B represent the evolution of the adjusted resistive torque applied by the stator 18 on the rotor 16 of the electric generator 14 for an electrical production installation 10 according to the invention, in which the module electric 38 provides a smoother evolution of the resistive torque.

In the graphs of FIGS. 3C and 4C, the curves VI in fine lines represent the evolution of the speed of rotation of the free turbine 20, measured by the speed sensor 34, for an electrical production installation 10, in which the torque resistive is not adjusted. It is noted that the unregulated rotation speed changes abruptly and inversely with respect to the demand for electrical energy. In fact, when the demand for electrical energy increases, the unadjusted resistive torque suddenly increases and the speed of rotation of the free turbine also suddenly decreases, before returning to its nominal value. Conversely, when the demand for electrical energy decreases, the unadjusted resistive torque suddenly decreases and the speed of rotation of the free turbine suddenly increases before returning to its nominal value.

The curves V2 in bold of the graphs of FIGS. 3C and 4C represent the evolution of the speed of rotation of the free turbine 20 for an electrical production installation 10 according to the invention, in which the electrical module 38 makes it possible to adjust the torque resistive and therefore limit the increase or decrease in the speed of rotation of the free turbine and, consequently, the deviations from its nominal.

On the 3D and 4D graphs, the PI curves in fine lines represent the evolution of the power supplied by the gas generator 12, for an electrical production installation 10, in which the resistive torque is not adjusted. It is noted that said power changes abruptly and follows the evolution of electrical demand. In fact, when the demand for electrical energy increases, the unadjusted resistive torque increases and the speed of rotation of the free turbine decreases before returning to its nominal value. The gas generator 12 is then forced to supply more power in order to compensate for the loss of speed of rotation of the free turbine. Conversely, when the demand for electrical energy decreases, the unadjusted resistive torque decreases and the speed of rotation of the free turbine increases before returning to its nominal value. The gas generator 12 is then forced to supply less power, so as to limit the speed of rotation of the free turbine.

The curves P2 in bold in the graphs of FIGS. 3D and 4D represent the evolution of the power of the gas generator 12 for an electrical production installation 10 according to the invention, in which the electrical module 38 makes it possible to adjust the resistive torque and therefore limiting the increase and decrease in the speed of rotation of the free turbine and, consequently, the deviations from its nominal value. It is also noted that, thanks to the invention, the power supplied by the gas generator does not vary appreciably and in particular does not increase suddenly, which makes it possible to reduce fuel consumption.

Claims (13)

1. Electrical production installation (10) for an aircraft having an electrical network (32), said electrical production installation comprising: • a gas generator (12); • a free turbine (20) driven in rotation by a gas flow (F) generated by the gas generator, the free turbine having a shaft (30); • an electric generator (14) comprising a stator (18) electrically connected to the electrical network and a rotor (16) driven in rotation by the shaft of the free turbine, the stator applying a resistive torque to the rotor of the electric generator; • a speed sensor (34) for measuring the speed of rotation of the free turbine; • an electric module (38) for adjusting said resistive torque applied to the rotor of the electric generator, the electric module being connected to the stator of the electric generator; and • a control device (36) of the electrical module configured to control the electrical module as a function of the speed of rotation of the free turbine measured by the speed sensor. 2. Installation according to claim 1, in which the control device (36) is configured to control the electrical module (38) according to a first control mode in which the electrical module acts as an electric charge or according to a second control mode wherein the electrical module acts as a source of electrical energy. 3. Installation according to claim 2, in which, in the first control mode, the electrical module (38) acts as an electrical charge when the measured rotational speed of the free turbine (20) is greater than a first predetermined high threshold. , in order to increase the resistive torque applied to the rotor of the electric generator (14). 4. Installation according to claim 3, wherein the electrical module (38) acting as an electrical load comprises at least one heating resistor (40). 5. Installation according to claim 4, wherein the gas generator (12) comprises a compressor (24) and said at least one heating resistor (40) is disposed at the outlet of the compressor to increase the temperature of the compressed air leaving the compressor. 6. Installation according to any one of claims 3 to 5, wherein the electrical module (38) acting as an electrical charge comprises at least one electrical energy storage device (42), preferably a super capacity. 7. Installation according to claim 2, in which, in the second control mode, the electrical module (38) acts as a source of electrical energy when the measured rotational speed of the free turbine (20) is less than a threshold. predetermined low, in order to decrease the resistive torque applied to the rotor (16) of the electric generator (14). 8. Installation according to claim 7, wherein the electrical module (38) acting as a source of electrical energy comprises at least one device for storing electrical energy (42). 9. Method for regulating the speed of rotation of the free turbine of the installation according to any one of claims 1 to 8, the installation comprising a gas generator (12), a free turbine (20) having a shaft (30), an electric generator (14) comprising a rotor (16) and a stator (18), an electric module (38) for adjusting the resistive torque applied to the rotor of the electric generator, electrically connected to the stator of the electric generator, a control device (36) of the electric module and a speed sensor (34) of rotation of the free turbine, method in which: • the rotational speed of the free turbine is measured using the speed sensor; • the resistive torque applied by the stator of the electric generator to the rotor of the electric generator connected to the shaft of the free turbine is adapted, as a function of the speed of rotation of the free turbine measured by the speed sensor. 10. The regulation method as claimed in claim 9, in which the electrical module (38) is controlled according to a first control mode, so that it acts as an electric charge or according to a second control mode, so that it acts as a source of electrical energy. 11. The control method as claimed in claim 10, in which, when the speed of rotation of the free turbine (20), measured by the speed sensor (34), is greater than a first high threshold and less than a second high threshold , the electric module (38) is controlled according to the first control mode, in which it acts as an electric charge, so as to increase the resistive torque applied by the stator (18) to the rotor (16) of the electric generator ( 14). 12. A method of regulation according to claim 10, in which, when the speed of rotation of the free turbine (20), measured by the speed sensor (34), is greater than a second high threshold: • the electric module (38) is controlled according to the first control mode, so as to increase the resistive torque applied by the stator (18) on the rotor (16) of the electric generator (14); • the operation of the gas generator (12) is interrupted. 13. The control method as claimed in claim 10, in which, when the speed of rotation of the free turbine (20), measured by the speed sensor (34), is less than a low threshold, the electrical module (38) is controlled. ) according to the second control mode, so as to reduce the resistive torque applied to the rotor (16) of the electric generator (14).