GENERAL TECHNICAL FIELD AND PRIOR ART
The invention relates to the regulation of power turboprops.
In modern turbo, speed of rotation of the propeller and the power transmitted to the propeller are controlled by means of regulators acting on two parameters: the setting of the propeller of the turboprop and the fuel flow injected into the combustion chamber.
Two control modes are conventionally used and alternate depending on the operating phases.
In a mode called "speed mode" ( "speed mode" according to English terminology), the fan speed is controlled by controlling its angle of incidence. In this mode, the fuel flow is used to secure the torque or the power delivered to the propeller.
In another mode, called "beta mode", the speed of rotation of the helix is ​​controlled by the fuel flow, the timing of the helix being set as a function of flight conditions and the throttle.

In this configuration, the timing is usually set to match a minimum pitch below which the propeller stopped working in propulsion mode and dissipates therefore more energy that is transmitted to it.

In a turboprop, the propeller rotational speed can be expressed by an equation derived from the energy balance of the power train:

The external powers applied to the system is the power delivered by the Pw power turbine T and the power dissipated by the propeller Pw H This equation reflects a change in kinetic energy of the screw, via the moment of inertia J Tot of the propeller, turbine and power transmission shaft and the speed of rotation of the propeller ωρ when the powers applied to the propeller balance more. The means for controlling the rotational speed of the propeller are thus modulate the power delivered by the engine via the fuel injection rate, and the power dissipated by the propeller.

The power dissipated by the propeller can be expressed as:

PwH = CP * p * n3 * D5

The power coefficient is noted (CP), where p is the density of air, n is the rotational speed of the propeller (revolutions per minute), the diameter D of the helix.

The power of a propeller coefficient is given to express the power dissipated by the propeller, and therefore the performance of this propeller.

During the operating phases of the aircraft, it may happen that the power coefficient fall, which may even be canceled in some cases. The pulling power of the propeller is canceled, and the energy from the engine to the propeller is no longer dissipated. This stored energy is reflected by increased rotation speed of the propeller outside its operating range, the propeller is then considered overspeed.

In more critical cases, the action of the relative wind on the propeller transmits the extra energy, so by passing the value of the power coefficient CP in the negative range, reflecting the energy input from the propeller to engine mechanical elements. This phenomenon of self-acceleration is not only a danger to the behavior of the aircraft but also for its mechanical components.

It is therefore necessary to ensure the thruster propeller operation by controlling the parameters affecting the power coefficient CP to maintain above a minimum limit value CPmin power coefficient determined by consideration when designing. The minimum limit of CPmin power coefficient can take different values ​​depending on various flight parameters, including the speed and altitude. Tables minimum limit values ​​CPmin power coefficient are then determined based on these parameters.

The difficulty of estimating the minimum power factor CPmin leads the manufacturer to adopt significant operating margins in the choice of a minimum pitch stop βηιίη, corresponding to the timing of the propeller when the power coefficient CP has value minimum limit CPmin. The power control system is deprived of part of its exploitable operating range. This loss is especially felt during operating steps requiring a very short step, and downhill or idling. This therefore causes instability of the control system that fails to keep the engine speed in the case of operation.

OVERVIEW OF THE INVENTION

A general object of the invention to solve the problems of the prior art.

In particular, an object of the invention is to increase the estimation accuracy of the minimum setting value guaranteeing the propeller to stay in his booster operating mode.

Another object of the invention is to continuously estimate and by iteration the minimum setting value guaranteeing the propeller to remain in its propellant operation mode.

In one aspect, the invention relates to a method of regulating the speed and power of a turbomachine impeller, wherein implement is placed at least two operating modes:

· One, said "speed mode", wherein the control timing of the helix (β) as a function of the desired speed of propeller, while the fuel flow is controlled according to the desired torque, • another, called "β mode", in which controls the fuel flow depending on the desired rate of propeller, stalling of the helix being set at an abutment angle which limits the setting of the propeller in both operating modes,

characterized in that the angle stop is calculated and updated continuously during flight as a function of parameters relating to the flight conditions estimated in real time.

Such a method advantageously further includes the various following characteristics taken individually or in all possible combinations:

• the stop angle is calculated and updated continuously by an estimation loop iterations by correcting the stop angle based on the parameters relating to the flight conditions estimated in real time as well as a coefficient value design estimated minimum power;

• a flight condition parameter estimated in real time and used in the calculation and the continuous update of the abutment angle is a helical Mach and / or an advancing coefficient;

· Estimation loop implements each iteration the following treatment:

- Acquisition of flight conditions parameters

- Determination based on these parameters and a stop angle of the previous iteration of a power coefficient associated with these parameters and this abutment angle

- Comparison of the coefficient of power with minimal power coefficient defined design

- Depending on the error output signal of this comparing step, updating of the stop angle by a correction function;

• during the determination step, the value of the power coefficient is determined according to a table previously stored power coefficients;

• the value of the minimum power coefficient varies depending on one or more parameters;

• it comprises an impairment detection of the abutment angle, the detection triggering the toggling of the "speed mode" to "fashion

3 » ;

• regulating the fuel flow implementing a power control loop and a tracking loop of the propeller speed set point;

• it comprises a common integrator to said loops of the different fuel flow control modes.

The invention also relates to a turbomachine comprising processing means implementing a control method of the aforementioned type.

PRESENTATION OF FIGURES

Other features and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting and should be read with reference to the appended figures in which:

- Figure 1 is a schematic representation of the operation of the system for estimating the value of the corresponding pmin wedging stop the real-time flight conditions.

- Figure 2 is a schematic representation in block diagram form the operation of the corrector used in the calculation loop of the stop timing pmin.

- Figure 3 is a representation in flowchart form of the steps of the estimation method continuously by iteration of the abutment timing pmin.

- Figure 4 shows a map of the CP propeller power coefficient as a function of the coefficient of advance J, of 70% helical Mach propeller Mw radius and the timing β helix.

- Figure 5 is a schematic representation of the operation of the comparison system between the β value and the pmin for detecting the reaching of the stop value β.

- Figure 6 is a schematic representation of the operation of the control system of the fuel flow injected into the combustion chamber.

DESCRIPTION OF ONE OR MORE MODES OF IMPLEMENTATION AND REALIZATION

continuously estimate iteration of the timing abutment

The proposed method estimates and updates continuously during flight the minimum timing abutment angle βηιίη according to parameters relating to the flight conditions estimated in real time.

This estimation is carried out by a computer which is installed in an aircraft for controlling the turboprop and regulate the power. This computer implements a control loop of the type of loop 1 shown in Figure 1.

The control loop 1 comprises three input parameters:

- the power of minimum propeller coefficient CPmin initially determined by design sensitivity studies,

- a helical Mach expressed in 70% of the propeller radius Mw (t),

- a progress coefficient J (t).

CPmin the value of minimum power coefficient CPmin is for example a reference value used for all flight conditions.

It can also be variable and take different discrete values ​​over time according to different parameters such as speed or altitude.

The minimum power coefficient CPmin (t) is injected into a comparator 11 with a power coefficient identified CP.Id (t). The error ε output from the comparator 11 (the difference between the minimum power coefficient CPmin and the power coefficient identified CP.Id (t)) is injected into a corrector 12.

This corrector 12 retained can be a proportional integral corrector following expression:

1 Too

C (z-1)

Gain2 Te " ^ (1 - z"*)

or :

z is the input parameter

- Te Gain2 and Xi are correcting settings

The corrector 12 converts the differential error it receives as input a signal corresponding to the wedge thrust value βη-ιίη (t) ensuring the propulsion mode of operation of the propeller to the flight conditions at this time t.

The output value min (t) of the corrector 12 is then injected into a memory of the computer used for the turboprop power control, where it replaces the old calibration stop value.

This output value is also sent, with the instantaneous value of Mach helical Mw (t) and the progress coefficient J (t), the input of a block 13 storing a mapping CP power coefficients.

This block 13 and mapping it stores enable the identification of a minimum power coefficient CP.Id (t + l) based on its input parameters. The CP.Id coefficient (t + l) is then fed back into the comparator 11 to be compared to the minimum coefficient defined CPmin design.

This example describes an embodiment in which the mapping of PC power coefficient values ​​takes into account three parameters is not limited. It is possible to consider a different number of parameters to refine and simplify this mapping.

This loop is iterated continuously during the entire flight.

Referring to Figure 2, the corrector 12 receives as input the difference between the minimum power coefficient CPmin and the power coefficient Cpld identified. This entry is injected into two static gains 121 and 122.

The output of the static gain 121 is fed into an integrator 123 and a summer 124.

The adder 124 subtracts the output of the integrator 123 to the output of the static gain 121.

The output of summer 124 is injected into a static gain 125, whose output is summed by an adder 126 to the output of the static gain 122.

The output of summer 126 is then injected into a static gain 127 whose output is fed into an adder 128 adding the output of the static gain 127 to the output signal βηΊ ίη.

The output of this adder 128 is fed into an integrator 129, including the initialization value is a security value βηι ίηθ.

The coefficients of various static gains 121, 122 are set empirically.

Static gains 125 and 127 correspond to the sampling period and calculating the corrector.

Figure 3 shows the same process in the form of a flowchart. A first step (step 1) corresponds to the acquisition of parameters that will perform the identification method of the pmin wedge stop, in this case the wedge abutting memory min (t), the helical Mach Mw ( t) and the coefficient of advance J (t).

During system initialization, the first step iterative thus takes value pmin as a safety value βηι independent ίηθ external parameters.

These parameters are used in a second step (step 2) to identify the CP.Id power coefficient (t) corresponding to the mapping 13 of CP power coefficient.

After a record of the minimum power coefficient value

CPmin (t) defined design (step 3), the two power coefficient values ​​are injected into the comparator 11 (step 4).

The difference is then corrected in the corrector 12 to transform the input information into a dunnage min abutment modification instruction (t + l) (step 5).

The minimum clamping abutment βηι ί η is calculated continuously and iteratively comparing a CP.Id power coefficient matched continuously to a minimum power coefficient CPmin defined design ensuring operation in propulsive mode of the helix.

Mapping Power Coefficient

Referring to Figure 4, a mapping of the PC power coefficient as used in the block 13 is determined at the design stage and takes into account three parameters of influence are:

- The Mach helical Mw expressed at a distance from the axis of rotation equivalent to 70% of the radius of the helix. It can be expressed in terms of the speed of flight here VTAS noted, the propeller tip speed here denoted UTIP and the speed of sound WNSC here denoted by the formula:

VTAS 2 + (0.7 - Utip) 2

Mw = - cson

With Utip = π * η * ϋ in the exprimant hélice the diameter D and the diet of rotation of the n hélice en tours / second.

- The progress coefficient J can be expressed as a function of VTAS flight speed, the rotational speed n and the helix diameter D according to the formula:

_ CRPS

~ n - D

- The angle full of hélice β.

These three parameters evolving continuously during the flight according to the conditions, it follows that the propeller power coefficient CP also varies according to the aircraft operating phases.

This CP power coefficient, defined by the propeller manufacturer during the design according to the request of the manufacturer, is then mapped according to the variations of the parameters chosen to express it. The mapping 13 is refined during the design by the propeller manufacturer and by the manufacturer to minimize the estimation uncertainty.

The different webs of CP power coefficient values ​​corresponding to different values ​​of Mw helical mach included here between 0.30 and 0.80. These terminals are not however limiting and, being clear that the change in Mw helical Mach continues, such representation is intended only to highlight the impact of different parameters.

wedging stop detection

The use of this minimal wedge abutment identification βηιίη occurs during the power control mode called "speed mode", adjusting the speed of rotation of the propeller by influencing the timing β.

When the stop is reached, the propeller speed can be maintained. The system must pass the control mode known as "speed mode" to "β mode."

Referring to Figure 5, the switchover from one mode to another is triggered by means of a detection system reached minimum clamping abutment 2.

The loop timing abutment achieving detection comprises four input parameters:

- The calibration abutment pmin (t)

- The timing of the helix p (t)

- The timing not stop updating Δβηιίη

- An operating margin H resulting in a hysteresis effect in loop input, the timing of the β helix (ί) and the stop timing βηιίη :) are injected into a comparator 21. The comparator 21 subtracts the wedge abutment βηιίη :) at the timing of the β helix (ί).

The other two inputs, the operating margin H and no update ΔβηΊίη wedging the stop are injected into an adder 22.

The summing of the output signal 22 and injected into a selector 3 registers 23 outputting the output signal of the adder 22.

The output signals of the comparator 21 and the selector 23 are injected into a logical operator 24, which emit an output signal when both input signals are equal.

A binary signal Τορβηιίη is transmitted to a logic level associated with one when the difference between the β timing and the stop βη-ιίη timing is less than the variation of the wedge abutment ΔβηΊίη added to a defined margin design causing effect hysteresis. This margin avoids switching from one control mode to another repeatedly in the case of a stabilized operation at the limit of the tilt value.

This can result in the equation:

TorvMii = TRUE si: b = + vMii DvMii +/- H

When the output signal Τορβηιίη by this control interchanging system is true, the control mode changes from the "speed mode" to "β mode".

Τορβηιίη returned to selector 23 via an integrator 25.

Switching between the "speed mode" and "β mode"

Referring to Figure 6, a power control system 3 makes it possible to modulate the fuel flow to monitor the propeller speed reference. Specifically, the existence of two fuel flow control loops is detailed.

One loop corresponds to a power control via the fuel flow 31, associated with the operation of the "speed mode."

Engine power setpoint 311 is compared with the measured power 312. The difference is injected into a corrector 313 to be converted into fuel flow variation setpoint 314 for adjusting the power to follow the setpoint.

The second loop corresponds to a propeller rotation speed control 32, more precisely to support the propeller speed by adapting the power via the fuel flow, associated with the operation of the "β mode".

The desired propeller system 321, so engine speed because the β timing is set in this mode, is compared with the measured speed 322. The difference is injected into a corrector 323 to be converted into fuel flow variation setpoint 324 to monitor the engine speed setpoint.

When the output signal of the detector Τορβηιίη abutment is detected as true, these two instructions 314, 324 are compared by an operator 33.

The fuel flow control loop offering the largest fuel flow variation control will therefore take precedence over the other, corresponding to a "max" operator.
The term integrator 34 of the correction is switched at the end of loop 33 after the operator max so as not integrate the difference between the actual control system 35 and the response thereby avoiding effect "wind up" of the system.

CLAIMS

Method for regulating the speed and power of a turbomachine impeller, wherein implement is placed at least two operating modes:

- one, said "speed mode", wherein the control timing of the helix (β) as a function of the desired speed of propeller, while the fuel flow is controlled according to the desired torque,

- the others, said "β mode" on commande est le débit de combustible en fonction de la vitesse d'hélice souhaitée, the full de l'hélice (β) étant Fixe a fall angle (βηΊ ί η) here the full limit of the hélice dans les deux modes of fonctionnement, unfrankierte en que angle of fall (βηι ί η :)) is not updated and en continu during a flight en fonction de Paramètres relatifs aux conditions de vol estimés in Lingfield.

Control method according to claim 1, characterized in that the abutment angle (βηιίη :)) is calculated and updated continuously by an estimation loop (1) by correcting iterations the abutment angle (βηιίη: )) as a function of parameters relating to the flight conditions estimated in real time and with a minimum output coefficient value (CPmin) estimated design.

Control method according to one of Claims 1 or 2, characterized in that a parameter estimated flight conditions in real time and used in the calculation and the continuous update of the abutment angle is a helical Mach ( Mw (t)) and / or a Q advance coefficient (t)).

Control method according to claim 2, characterized in that the estimation loop (1) implements at each iteration the following treatment:

- Acquisition of flight conditions parameters (w (t)) and (J (t))

- Determination based on these parameters and a stop angle ^ min (t)) of the previous iteration of a power coefficient associated (CP.Id (t)) to these parameters and this abutment angle ^ min (t))

- Comparison of the power coefficient (CP.Id (t)) with a minimum power coefficient (CPmin) defined design

- Depending on the error output signal of this comparing step, updating of the stop angle ^ min (t + l)) by a correction function.

Control method according to claim 4, characterized in that during the step of determining the value of the power coefficient (CP.Id (t)) is determined based on a table (13) of power coefficients ( CP) previously stored.

A method according to claim 2, characterized in that the value of the minimum power coefficient (CPmin (t)) varies depending on one or more parameters.

Method according to one of the preceding claims, characterized in that it comprises an impairment detection (2) of the stop angle (pmin), this detection triggering the toggling of the "speed mode" to "β mode".

Method according to one of the preceding claims, characterized in that the control fuel flow (3) implements a power control loop (31) and a tracking loop of the propeller speed reference (32).

A method according to claim 8, characterized in that it comprises an integrator (34) common to said loops (31, 32) different fuel flow control modes.

lO.Turbomachine comprising processing means implementing a power control method as defined in the preceding claims.