Method for controlling a turbomachine comprising an electric motor

Abstract

A method for controlling a turbomachine comprising an electric motor forming a torque injection device on a high-pressure rotation shaft, in which method a fuel flow setpoint Q.sub.CMD and a torque setpoint TRQ.sub.CMD provided at the electric motor are determined, the control method comprising: • a step of implementing a first fuel control loop in order to determine the fuel flow set point QCMD, • a step of implementing a second, torque control loop in order to determine the torque setpoint TRQ.sub.CMD comprising i. a step of determining a torque correction variable ΔTRQ.sub.CMD as a function of a transitory speed setpoint NHTrajAccelCons, NHTrajDecelCons and ii. a step of determining the torque setpoint TRQ.sub.CMD as a function of the torque correction variable ΔTRQ.sub.CMD.

Claims

1. A method for controlling a turbomachine comprising a fan positioned upstream of a gas generator and delimiting a primary airflow and a secondary airflow, the primary airflow passing through said gas generator which comprises a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine and a low-pressure turbine, said low-pressure turbine being connected to said low-pressure compressor by a low-pressure rotation shaft and said high-pressure turbine being connected to said high-pressure compressor by a high-pressure rotation shaft, the turbomachine comprising an electric motor forming a torque injection device on the high-pressure rotation shaft, method wherein a fuel flow set point Q.sub.CMD in the combustion chamber and a torque set point TRQ.sub.CMD provided to the electric motor are determined, the control method comprising: a step of implementing a first fuel regulation loop in order to determine the fuel flow set point Q.sub.CMD comprising: i. a step of detecting a speed transient intent TopAccel, TopDecel as a function of a difference between a current speed NH and a determined set point speed NH.sub.CONS, ii. a step of determining a transient speed set point NHTrajAccelCons, NHTrajDecelCons, iii. a step of determining a fuel correction quantity ΔQ.sub.CMD as a function of the transient speed set point NHTrajAccelCons, NHTrajDecelCons; and iv. a step of determining the fuel flow set point Q.sub.CMD as a function of the fuel correction quantity ΔQ.sub.CMD a step of implementing a second torque regulation loop in order to determine the torque set point TRQ.sub.CMD comprising i. a step of determining a torque correction quantity ΔTRQ.sub.CMD as a function of the transient speed set point NHTrajAccelCons, NHTrajDecelCons, and ii. a step of determining the torque set point TRQ.sub.CMD as a function of the torque correction quantity ΔTRQ.sub.CMD.

2. The control method according to claim 1, comprising: during the step of implementing the first fuel regulation loop, a step of detecting a fuel set point stop TopButeeAccel, TopButeeDecel, during the step of implementing the second torque regulation loop, a step of zero resetting the torque set point TRQ.sub.CMD, the step of zero resetting the torque set point TRQ.sub.CMD being inhibited in the case of detection of a speed transient intent TopAccel, TopDecel and detection of a fuel set point stop TopButeeAccel, TopButeeDecel.

3. The control method according to claim 2, wherein the torque set point TRQ.sub.CMD is gradually zero reset.

4. The control method according to claim 3, wherein the reduction gradient is a function of the response time of the first fuel regulation loop.

5. The control method according to claim 1, comprising a step of doubly integrating the torque correction quantity ΔTRQ.sub.CMD in order to determine the torque set point TRQ.sub.CMD.

6. The control method according to claim 1, wherein the torque set point TRQ.sub.CMD is bounded between a maximum torque value TRQ.sub.max determined by the structure of the electric motor ME and a minimum torque value TRQ.sub.min determined by the structure of the electric motor ME.

7. A computer program comprising instructions for executing the steps of the control method according to claim 1 when said program is executed by a computer.

8. An electronic control unit for a turbomachine comprising a memory comprising instructions of the computer program according to claim 7.

9. A turbomachine comprising the electronic unit according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be better understood upon reading the following description, given only by way of example, and referring to the appended drawings in which:

(2) FIG. 1 is a schematic representation of a turbomachine according to prior art,

(3) FIG. 2 is a schematic representation of a fuel flow set point regulation system according to prior art,

(4) FIG. 3 is a schematic representation of the increase in engine speed and the fuel flow set point as a result of a pilot's acceleration command according to prior art,

(5) FIG. 4 is a schematic representation of a turbomachine according to an embodiment of the invention,

(6) FIG. 5 is a schematic representation of a fuel flow set point and torque set point regulation system according to the invention,

(7) FIG. 6 is a schematic representation of a first fuel regulation loop of the regulation system of FIG. 5,

(8) FIG. 7 is a schematic representation of a second torque regulation loop of the regulation system of FIG. 5,

(9) FIG. 8 is a schematic representation of an integration module of the second torque regulation loop of FIG. 7 and

(10) FIG. 9 is a schematic representation of the increase in engine speed, fuel flow set point and torque set point as a result of a pilot's acceleration command according to the invention.

(11) It should be noted that the figures disclose the invention in a detailed manner in order to implement the invention, said figures may of course be used to better define the invention if necessary.

DETAILED DESCRIPTION

(12) With reference to FIG. 4, a turbomachine T of the twin-spool turbofan engine type for an aircraft is schematically represented. In a known manner, the turbomachine T comprises, from upstream to downstream in the direction of gas flow, a fan 10, a low-pressure compressor 11, a high-pressure compressor 12, a combustion chamber 13 which receives a fuel flow set point Q.sub.CMD, a high-pressure turbine 14, a low-pressure turbine 15 and an exhaust primary nozzle 16. The low-pressure (LP) compressor 11 and the low-pressure turbine 15 are connected by a low-pressure shaft 21 and together form a low-pressure spool. The high-pressure (HP) compressor 12 and the high-pressure turbine 14 are connected by a high-pressure shaft 22 and, with the combustion chamber 13, together form a high-pressure spool. Fan 10, which is driven by the LP shaft 21, compresses the ingested air. This air is divided downstream of the fan into a secondary airflow which is directed directly towards a secondary nozzle (not represented) through which it is ejected to participate in the thrust provided by the turbomachine 100, and a so-called primary airflow which enters the gas generator, consisting of the low-pressure spool and the high-pressure spool, and is then ejected into the primary nozzle 16. In a known manner, to change the speed of the turbomachine T, the aircraft pilot changes the position of a control lever which allows the fuel flow set point Q.sub.CMD in the combustion chamber 13 to be changed.

(13) With reference to FIG. 4, turbomachine T further comprises an electric motor ME configured to provide additional torque to the high-pressure shaft 22. The operation of the turbomachine T is controlled by an electronic unit 20 which obtains signals representing operating parameters of the turbomachine T, especially the speed NH of the turbomachine T, to provide the fuel flow set point Q.sub.CMD and a torque set point TRQ.sub.CMD to the electric motor ME.

(14) As illustrated in FIG. 5, the electronic unit 20 comprises a regulation system comprising a first fuel flow set point Q.sub.CMD regulation loop B1, hereinafter referred to as “first fuel loop B1”, and a second electrical torque set point TRQ.sub.CMD regulation loop B2, hereinafter referred to as “second torque loop B2”.

(15) As illustrated in FIG. 5, the first fuel loop B1 comprises: a speed NH input of the turbomachine T a set point speed NH.sub.CONS input defined by the position of the control lever handleable by the aircraft pilot, a fuel flow set point Q.sub.CMD output transmitted to the turbomachine T and a plurality of output indicators: an indicator of an acceleration transient request TopAccel an indicator of a deceleration transient request TopDecel an indicator of an acceleration stop TopButeeAccel defined by the saturation of the control of the correctors by the acceleration C/P stop an indicator of a deceleration stop TopButeeDecel defined by the saturation of the control of the correctors by the shutdown C/P stop a speed trajectory set point for acceleration NHTrajAccelCons a speed trajectory set point for deceleration NHTrajDecelCons

(16) Still with reference to FIG. 5, the second torque loop B2 receives as an input all the output indicators generated by the first fuel loop B1, that is TopAccel, TopDecel, TopButeeAccel, TopButeeDecel, NHTrajAccelCons, NHTrajDecelCons, as well as the speed NH input of the turbomachine T. Advantageously, by virtue of this regulation system, the second torque loop B2 makes it possible to provide a torque set point TRQ.sub.CMD being adaptive as a function of the behavior of fuel loop B1, which remains a priority.

(17) In this example, the first fuel loop B1 also comprises a static pressure input to the combustion chamber PS3.

(18) The structure and operation of each loop B1, B2 will now be set forth in detail.

(19) First Fuel Regulation Loop B1

(20) In a known manner, with reference to FIG. 6, the first fuel loop B1 comprises a stabilized management module 301, a transient intent detection module 302, a speed trajectory generation module 303, a selection module 304, an integration module 305 and a stop management module 306 which fulfills a saturation function of the integration and therefore of the fuel control Q.sub.CMD.

(21) As will be set forth later, the speed trajectory generation module 303 is also configured to generate a command for the control of this trajectory.

(22) The stabilized management module 301 provides a correction quantity to the selection module 304 as a function of the difference between the speed NH of the turbomachine T and the set point speed NH.sub.CONS. Such a stabilized management module 301 is known to those skilled in the art and will not be set forth in more detail.

(23) The purpose of the transient intent detection module 302 is to detect a transient intent desired by the pilot. The transient intent detection module 302 determines a difference between the speed NH of the turbomachine T and the set point speed NH.sub.CONS. When the control lever remains in a constant position and the stabilized management module 301 is implemented, the actual speed NH of the turbomachine T is stationary and equal to the set point speed NH.sub.CONS. If the pilot moves the control lever, the set point speed NH.sub.CONS varies instantaneously. On the contrary, the speed NH does not vary instantaneously due to the inertia of the turbomachine T and the stabilized management module 301. Thus, the transient intent detection module 302 detects a transient intent when the difference between the set point speed NH.sub.CONS and the actual speed NH is greater than a predetermined threshold S3.

(24) According to the invention, the transient intent detection module 302 also provides an indicator of acceleration transient request TopAccel and an indicator of deceleration transient request TopDecel. In the case of acceleration, if the speed deviation is greater than the predetermined threshold S3 (NH.sub.CONS−NH>S3), the indicator of acceleration transient request TopAccel is activated. This function is implemented in an acceleration sub-module 302a which is a comparator. Similarly, in the case of deceleration, if the speed deviation is greater than the predefined threshold S3 (NH−NH.sub.CONS>S3), the indicator of deceleration transient request TopDecel is activated. This function is implemented in a deceleration sub-module 302d which is a comparator. By way of example, the threshold S3 is 200 rpm.

(25) When a transient phase is detected, the transient intent detection module 302 generates an activation signal, which is transmitted to the speed trajectory generation module 303 and the selection module 304 as illustrated in FIG. 6.

(26) In the case of acceleration, the speed trajectory generation module 303 determines a speed set point for acceleration (acceleration trajectory) NHTrajAccelCons. Similarly, in the case of deceleration, the speed trajectory generation module 303 determines a speed NH set point for deceleration (deceleration trajectory) NHTrajDecelCons. Such a speed trajectory generation module 303 is known to those skilled in the art and will not be set forth in more detail. In addition, the generation module 303 is also configured to generate a correction quantity that allows the trajectory set point to be followed if necessary.

(27) In this example, when the selection module 304 receives an activation signal from the transient intent detection module 302, the selection module 304 selects the correction quantity from the stabilized management module 301 if no activation signal is received and selects the correction quantity from the speed trajectory generation module 303 in the case of receipt of an activation signal. Such a selection module 304 is known to those skilled in the art and will not be set forth in more detail.

(28) The selected fuel correction quantity ΔQ.sub.CMD is provided to the integration module 305. The integration module 305 determines the fuel flow set point Q.sub.CMD by integrating the fuel correction quantity ΔQ.sub.CMD.

(29) The stop management module 306 limits the value of the fuel flow set point Q.sub.CMD determined by the integration module 305. In a known manner, the stop management module 306 implements a so-called C/P stop, known to those skilled in the art. In this example, the stop management module 306 allows definition of stop set points in acceleration and deceleration. For this purpose, in the case of acceleration, the stop management module 306 allows definition of an indicator of saturation of the control of the correctors by the acceleration C/P stop TopButeeAccel. Similarly, in the case of deceleration, the stop management module 306 allows definition of an indicator of saturation of the control of the correctors by the shutdown C/P stop TopButeeDecel. Such stops are known to those skilled in the art and will not be set forth in more detail. Preferably, the stop management module 306 determines the stops as a function of the static pressure in the combustion chamber PS3 and the speed NH (high-pressure spool speed).

(30) As previously indicated, such a regulation is optimal for limiting the fuel set point Q.sub.CMD transmitted to turbomachine T but induces significant response times.

(31) To eliminate this drawback, a second torque loop B2 is coupled to the first fuel loop B1 to determine an optimum torque set point TRQ.sub.CMD. For this purpose, unlike prior art, the first fuel loop B1 communicates to the second torque loop B2 the various output indicators: TopAccel, TopDecel, NHTrajAccelCons, NHTrajDecelCons, TopButeeAccel, TopButeeDecel.

(32) Second Torque Regulation Loop B2

(33) The aim of the second torque regulation loop B2 is to use the electric motor ME sparingly. Thus, a torque set point TRQ.sub.CMD is activated only when the trajectories are limited (TopButeeAccel or TopButeeDecel) and the deviation between the NH.sub.CONS speed set point and the actual speed NH indicates a need for activating the transient controls (TopAccel or TopDecel). In other words, a torque set point TRQ.sub.CMD is only activated when the fuel set point Q.sub.CMD is restricted within its operating range.

(34) As will be set forth later, the electrical torque TRQ.sub.CMD provided allows the operating point to be deviated from the operating limits and thus provides the control margin to adapt the fuel set point Q.sub.CMD again. By virtue of the invention, the first fuel loop B1 and the second torque loop B2 are interchanged to improve operability of the turbomachine T (response time, etc.) while at the same time limiting power consumption by the electric motor ME.

(35) With reference to FIG. 7, the second torque regulation loop B2 comprises a command determination module 401, a zero reset module 402, an integration module 403 and a switch 404.

(36) The command determination module 401 comprises: a current speed NH input of the turbomachine the speed NH set point for acceleration (acceleration trajectory) NHTrajAccelCons providing a set point quantity for the torque command the speed NH set point for deceleration (deceleration trajectory) NHTrajDecelCons providing a set point quantity for the torque command.

(37) The command determination module 401 comprises a deceleration sub-module 401d and an acceleration sub-module 401a which are respectively configured to calculate a torque command for acceleration (acceleration torque) TRQTrajAccelCmd and a torque command for deceleration (deceleration torque) TRQTrajDecelCmd.

(38) In this example, the acceleration sub-module 401a calculates a correction quantity, of the second derivative type, for acceleration (acceleration torque) TRQTrajAccelCmd as a function of the speed NH set point for acceleration (acceleration trajectory) NHTrajAccelCons, and the current speed NH input. Preferably, the acceleration sub-module 401a is in the form of an integral dual-integrator type corrector that fulfills the following transfer function:

(39) ${\mathrm{RC}}_{\mathrm{NHTrans}}\left(p\right)=K_{\mathrm{NH}}^{-1}.Math.\frac{\left(1+{\tau }_{\mathrm{NH}}.Math.p\right)\left(1+{\tau }_{\mathrm{Transit}}.Math.p\right)}{{\tau }_{\mathrm{BF}}.Math.{\tau }_{\mathrm{Transit}}{p}^2}$
in which function: K is a predetermined inverse constant and τ.sub.NH, τ.sub.Transit and τ.sub.BF are predetermined time constants.

(40) The structure of such an acceleration sub-module 401a is known to the those skilled in the art. The structure and function of the deceleration sub-module 401d are analogous.

(41) With reference to FIG. 7, the selection of the command before integration by the integration module 403 is performed by a switch 404 in order to select the deceleration command in deceleration or the acceleration command in acceleration.

(42) The zero reset module 402 comprises a plurality of input indicators from the first fuel loop B1: the indicator of an acceleration transient request TopAccel the indicator of a deceleration transient request TopDecel the indicator of an acceleration stop TopButeeAccel defined by the saturation of the control of the correctors by the acceleration C/P stop the indicator of a deceleration stop TopButeeDecel defined by the saturation of the control of the correctors by the shutdown C/P stop.

(43) The aim of the zero reset module 402 is to zero reset the torque set point TRQ.sub.CMD. As will be set forth later, zero resetting is not abrupt but gradual. The zero reset module is implemented continuously. Nevertheless, zero resetting is inhibited: when an acceleration is requested and when the acceleration stop is already reached (TopAccel and TopButeeAccel activated) or when deceleration is requested and when the deceleration stop is already reached (TopDecel and TopButeeDecel activated).

(44) When the fuel set point Q.sub.CMD of the first fuel loop B1 wants to deviate from the allowed operating range, the zero reset module 402 is not zero reset. Thus, the torque set point TRQ.sub.CMD enables the operating point to deviate from the operating limits. zero resetting the torque set point TRQ.sub.CMD is only initiated when regulation by the fuel set point Q.sub.CMD is possible.

(45) In other words, the second torque loop B2 acts synergistically with the first fuel loop B1. The second torque loop B2 supports the first fuel loop B1. In a stabilized speed, the torque set point TRQ.sub.CMD is thus zero reset to limit power consumption and improve efficiency.

(46) With reference to FIG. 7, the integration module 403 comprises: a correction input receiving a torque correction quantity ΔTRQ.sub.CMD from switch 404 a maximum torque value TRQ.sub.max determined by the structure of the electric motor ME a minimum torque value TRQ.sub.min determined by the structure of the electric motor ME a zero reset RAZ input provided by the zero reset module 402 a torque set point TRQ.sub.CMD output.

(47) In this example, the integration module 403 is a double integrator, in order to integrate the torque correction quantity ΔTRQ.sub.CMD. This ensures a permanent zero speed error and thus a predetermined acceleration or deceleration time.

(48) An example of an integration module 403 is represented in detail in FIG. 8. In this example of implementation, the integration module 403 allows the torque set point TRQ.sub.CMD to be defined according to several ramps or gradients. With reference to FIG. 8, the integration module 403 contains two modules for calculating the saturation values of the integrators 51, 52.

(49) As illustrated in FIG. 8, the two calculation modules 51, 52 will be saturated in order to fulfill the maximum torque TRQ.sub.MAX limitations and minimum torque TRQ.sub.MIN limitations related to the constraints of the electric machine ME and also to avoid divergence of the calculation modules 51, 52 in case their requests are limited by the physical structure of the electric motor ME.

(50) Each calculation module 51, 52 comprises a zero reset RAZ input in order to gradually reduce the value of the torque set point TRQ.sub.CMD.

(51) Indeed, the additional or deficit mechanical torque set point TRQ.sub.CMD has to be suppressed once the transient is over. Indeed, the torque used for a transient cannot be maintained because it no longer necessarily corresponds to a current need and would generate undesired excessive power consumption.

(52) By way of example, in the case of deceleration, the second torque loop B2 imposes a resistive torque TRQ.sub.CMD in order to allow the speed NH to drop according to the determined trajectory, the turbomachine T reaches idle speed at the end of the transient. If the resistive torque TRQ.sub.CMD is maintained during deceleration on the stabilized idle phase, the fuel then required to maintain idle will have to compensate unnecessarily for this resistive torque which is no longer useful on this operation phase. Efficiency would then be penalized. This reasoning applies in an acceleration end phase as well as in a phase in which acceleration and deceleration alternate.

(53) As illustrated in FIG. 7, the zero reset RAZ indicator allows each of the integrators 51, 52 to be zero reset when activated. However, in order to avoid disturbance of the speed NH due to the electrical torque TRQ being suppressed too quickly, the torque set point TRQ.sub.CMD is reduced slowly according to a predetermined gradient, in this example a reduction gradient QKGS (not represented). In practice, in this example, the values of the integrators are stored and are gradually zero reset as a function of the past values. When the zero reset RAZ indicator is no longer to zero, the values of the integrators start to increase again.

(54) Advantageously, the reduction gradient QKGS is predetermined as a function of the response time of the first fuel loop B1, the response time being obtained by test and simulation. Thus, the integration module 403 of the second torque loop B2 reduces its influence on the speed NH, which advantageously allows the first fuel loop B1 to adapt the fuel set point Q.sub.CMD effectively, since the electrical torque being fed has allowed the operating point to deviate from the limits Q.sub.MAX, Q.sub.MIN. The compensation achieved by the first fuel loop B1 is natural and controlled.

(55) In other words, the second torque loop B2 relieves the first fuel loop B1 during a transient. The torque set point TRQ.sub.CMD is thus zero reset when the conditions for activating torque regulation have disappeared.

(56) Suppressing the torque set point TRQ fed by the electric machine ME has to be simultaneously compensated for by adapting the fuel set point Q.sub.CMD, otherwise a disturbance of the speed NH would be systematic. Advantageously, adapting the fuel set point Q.sub.CMD is automatic and it is not necessary to calculate new indicators in the second torque loop B2 for the first fuel loop B1.

(57) An example of implementation of a turbomachine control method wherein a fuel flow set point Q.sub.CMD and an electrical torque set point TRQ.sub.CMD are determined will now be set forth.

(58) In this example of implementation, the pilot handles the control lever to increase the speed of the turbomachine T at a time t1=5 seconds as illustrated in FIG. 9.

(59) The first regulation loop B1 detects a speed transient via the transient intent detection module 302 and emits an indicator of acceleration transient request TopAccel. Similarly, the speed trajectory generation module 303 determines a speed set point for acceleration (acceleration trajectory) NHTrajAccelCons. As illustrated in FIG. 9, the acceleration trajectory is in the form of a slope. In addition, stop management module 306 limits the value of the fuel flow set point Q.sub.CMD and defines an acceleration stop set point TopStopAccel that imposes a maximum fuel set point Q.sub.MAX.

(60) During the period P1-2, defined between times t1 and t2, the current speed NH is lower than the acceleration trajectory set point NHTrajAccelCons because the fuel set point Q.sub.CMD is limited by the maximum fuel set point Q.sub.MAX.

(61) During this period P1-2, the torque set point TRQ.sub.CMD gradually increases (by convention in FIG. 9, a torque increase has a negative value) until time t2. As the torque set point TRQ.sub.CMD increases, the current speed NH increases due to the additional electrical torque and allows the acceleration trajectory NHTrajAccelCons to be followed reactively, which is very advantageous. Furthermore, as the torque set point TRQ.sub.CMD increases, the fuel set point Q.sub.CMD deviates from the maximum fuel set point Q.sub.MAX, thus providing a regulation range for the fuel set point Q.sub.CMD that is no longer restricted.

(62) Also, during the period P2-3, defined between times t2 and t3, the first fuel loop B1 allows the fuel set point Q.sub.CMD to be adapted so that the current speed NH will reactively follow the acceleration trajectory NHTrajAccelCons. As the fuel set point Q.sub.CMD is deviated from the maximum fuel set point Q.sub.MAX, the acceleration stop set point TopStopAccel is no longer activated. Also, zero resetting the torque set point TRQ.sub.CMD can be implemented over the period P2-3. As illustrated in FIG. 9, zero resetting is performed gradually so as not to abruptly reduce the current speed NH and allow the first fuel loop B1 to take over for regulation.

(63) At time t3, similarly to time t1, the fuel set point Qcmp is limited by the maximum fuel set point Q.sub.MAX. The acceleration stop set point TopStopAccel is then activated, inhibiting the zero reset of the torque set point TRQ.sub.CMD which increases again. At time t3, the torque set point TRQ.sub.CMD did not have time to be cancelled. Similarly, over the period P3-4, defined between times t3 and t4, the current speed NH is lower than the acceleration trajectory set point NHTrajAccelCons because the fuel set point Q.sub.CMD is limited by the maximum fuel set point Q.sub.MAX. The torque set point TRQ.sub.CMD gradually increases until time t4.

(64) By virtue of the invention, the electric motor ME is used sparingly to allow optimum trajectory following, offering a margin of regulation for the fuel set point Q.sub.CMD. The first fuel loop B1 and the second torque loop B2 are implemented synergistically to optimize following of the speed trajectory and thus improve operability of the turbomachine T.

(65) It goes without saying that only some of these indicators could be used. Similarly, it goes without saying that other indicators could be used to refine torque set point regulation.