Method and a device for detecting icing at an air inlet of a turboshaft engine

Abstract

A method of detecting that an aircraft is flying in icing conditions. A processor unit determines a real power developed by the turboshaft engine and a theoretical power that the engine can develop in theory, the theoretical power being determined using a theoretical model supplying a power as a function at least of a speed of rotation of a gas generator of the engine. The processor unit determines a difference between the real power and the theoretical power. The processor unit generates a warning to indicate the presence of icing conditions when the power difference is greater than a predetermined power threshold for a length of time longer than a time threshold, and when a temperature outside the aircraft lies between a low temperature threshold and a high temperature threshold.

Claims

1. A method of detecting that an aircraft is flying in icing conditions, the aircraft having a turboshaft engine receiving air coming from an outside medium situated outside the aircraft via an air inlet, the engine including a gas generator provided with at least one compressor and a combustion chamber, the engine further including a power assembly having at least one power turbine driven in rotation by exhaust gas from the combustion chamber, the method comprising: a processor unit determining a real power developed by the engine as a function of a torque developed by the power assembly as measured by a torque measurement system and of a speed of rotation of the power assembly as measured by a speed measurement system, the speed of rotation of the power assembly being referred to as a second speed of rotation; the processor unit determining a theoretical power that the engine can develop in theory, the theoretical power being determined by the processor unit as a function at least of a theoretical model of the engine, the theoretical model of the engine providing the theoretical power as a function at least of a speed of rotation of the gas generator as measured by a speed measurement sensor, the speed of rotation of the gas generator being referred to as a first speed of rotation; the processor unit determining a power difference between the real power and the theoretical power; and the processor unit generating a warning to indicate a presence of icing conditions when: the power difference is greater than a predetermined power threshold for a duration longer than a time threshold; and an outside temperature of the outside medium as measured by a temperature sensor lies between a low temperature threshold and a high temperature threshold.

2. The method according to claim 1, wherein the processor unit determines the theoretical power as a function of a power referred to as a bench guaranteed minimum power, the theoretical model of the engine providing the bench guaranteed minimum power as a function of a pressure and a temperature of the air in the outside medium, of the first speed of rotation, and of the second speed of rotation.

3. The method according to claim 1, wherein the processor unit determines the theoretical power as a function of a power referred to as a bench guaranteed minimum power as corrected using at least an installation loss representing power losses resulting from arranging the engine on an aircraft, and an operating margin of the engine representing a power margin of the engine compared to the bench guaranteed minimum power.

4. The method according to claim 3, wherein the processor unit: determines a power referred to as an engine-installed guaranteed minimum power that the engine can develop while arranged on the aircraft; and determines the theoretical power: by adding to the engine-installed guaranteed minimum power an operating margin obtained during an engine health check; and/or by subtracting from the engine-installed guaranteed minimum power the installation loss.

5. The method according to claim 3, wherein the processor unit: determines a power referred to as an engine-installed guaranteed minimum power that the engine can develop while arranged on the aircraft; and determines the theoretical power: by adding to the engine-installed guaranteed minimum power an operating margin obtained during an engine health check; and by subtracting from the engine-installed guaranteed minimum power the installation loss.

6. The method according to claim 3, wherein the processor unit: determines a power referred to as an engine-installed guaranteed minimum power that the engine can develop while arranged on the aircraft; and determines the theoretical power: by adding to the engine-installed guaranteed minimum power an operating margin obtained during an engine health check; or by subtracting from the engine-installed guaranteed minimum power the installation loss.

7. The method according to claim 1, wherein the processor unit: determines a power referred to as an engine-installed guaranteed minimum power that the engine can develop while arranged on the aircraft; determines an operating margin relative to the engine-installed guaranteed minimum power, the operating margin being established and transmitted to the processor unit by an engine health monitoring system; and determines the theoretical power, the theoretical power being equal to a sum of the operating margin plus the engine-installed guaranteed minimum power.

8. The method according to claim 7, wherein the processor unit: determines a power referred to as a bench guaranteed minimum power that the engine can develop while arranged on a bench; determines an installation loss representing power losses resulting from arranging the engine on an aircraft as a function of a stored installation loss model; determines the engine-installed guaranteed minimum power, the engine-installed guaranteed minimum power being equal to a difference between the bench guaranteed minimum power and the installation loss.

9. The method according to claim 8, wherein the installation loss model supplies the installation loss as a function of a pressure and of a temperature of the air in the outside medium and as a function of a travel speed of the aircraft.

10. The method according to claim 8, wherein the processor unit determines the bench guaranteed minimum power from the theoretical model of the engine, the theoretical model of the engine providing the bench guaranteed minimum power as a function of a pressure and of a temperature of the air in the outside medium, of the first speed of rotation, and of the second speed of rotation.

11. The method according to claim 1, wherein the low temperature threshold is 10 degrees Celsius.

12. The method according to claim 1, wherein the high temperature threshold is +5 degrees Celsius.

13. The method according to claim 1, wherein the time threshold is 30 seconds.

14. The method according to claim 1, wherein the power threshold is 150 newton-meters.

15. A detector device for detecting that an aircraft is flying in icing conditions, the aircraft having a turboshaft engine receiving air coming from an outside medium situated outside the aircraft via an air inlet, the engine including a gas generator having at least one compressor and a combustion chamber, the engine further including a power assembly having at least one power turbine driven in rotation by exhaust gas from the combustion chamber, the detector device comprising: a torque measurement system for measuring a torque developed by the power assembly; a first speed measurement system for measuring a speed of rotation of the power assembly and a second speed measurement system for measuring a speed of rotation of the gas generator; a warning system; a temperature sensor for measuring a temperature of the air in the outside medium situated outside the aircraft; and a processor unit connected to the torque measurement system, to the first speed measurement system, to the second speed measurement system, to the warning system, and to the temperature sensor, the processor unit including a storage device storing a theoretical model of the engine; wherein the processor unit determines a real power developed by the engine as a function of the torque developed by the power assembly and of the speed of rotation of the power assembly; wherein the processor unit determines a theoretical power that the engine can develop in theory, the theoretical power being determined by the processor unit as a function at least of the theoretical model of the engine, the theoretical model of the engine providing the theoretical power as a function at least of the speed of rotation of the gas generator; wherein the processor unit determines a power difference between the real power and the theoretical power; and wherein the processor unit generates a warning via the warning system to indicate a presence of icing conditions when: the power difference is greater than a predetermined power threshold for a duration longer than a time threshold; and an outside temperature of the outside medium as measured by the temperature sensor lies between a low temperature threshold and a high temperature threshold.

16. The detector device according to claim 13, the detector device further comprising an engine health monitoring system co-operating with the processor unit.

17. The detector device according to claim 13, the detector device further comprising an installation loss model stored in the memory of the processor unit.

18. The detector device according to claim 13, the detector device further comprising a pressure sensor for measuring a pressure of the air outside the aircraft.

19. The detector device according to claim 15, the detector device further comprising a speed measurement device for measuring a travel speed of the aircraft.

20. An aircraft comprising: a turboshaft engine receiving air coming from an outside medium situated outside the aircraft via an air inlet, the engine including a gas generator having at least one compressor and a combustion chamber, the engine further including a power assembly having at least one power turbine driven in rotation by exhaust gas from the combustion chamber; a detector device to detect that the aircraft is flying in icing conditions, the detector device including a torque measurement system for measuring a torque developed by the power assembly; a first speed measurement system for measuring a speed of rotation of the power assembly; a second speed measurement system for measuring a speed of rotation of the gas generator; a warning system; a temperature sensor for measuring a temperature of the air in the outside medium situated outside the aircraft; and a processor unit connected to the torque measurement system, to the first speed measurement system, to the second speed measurement system, to the warning system, and to the temperature sensor, the processor unit having a storage device storing a theoretical model of the engine; wherein the processor unit determines a real power developed by the engine as a function of the torque developed by the power assembly and of the speed of rotation of the power assembly; wherein the processor unit determines a theoretical power that the engine can develop in theory, the theoretical power being determined by the processor unit as a function at least of the theoretical model of the engine, the theoretical model of the engine providing the theoretical power as a function at least of the speed of rotation of the gas generator; wherein the processor unit determines a power difference between the real power and the theoretical power; and wherein the processor unit generates a warning via the warning system to indicate a presence of icing conditions when: the power difference is greater than a predetermined power threshold for a duration longer than a time threshold; and an outside temperature of the outside medium as measured by the temperature sensor lies between a low temperature threshold and a high temperature threshold.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The invention and its advantages appear in greater detail from the context of the following description of examples given by way of illustration and with reference to the accompanying figures, in which:

(2) FIG. 1 is a view of the device of the invention; and

(3) FIG. 2 is a diagram explaining the method of the invention.

(4) Elements that are present in more than one of the figures are given the same references in each of them.

DETAILED DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows an aircraft 1 of the invention.

(6) In particular, the aircraft 1 includes a lift and/or propulsion rotor 2. The rotor 2 is driven in rotation by a power plant comprising at least one turboshaft engine 10 and at least one main gearbox 3.

(7) The engine 10 includes a gas generator 11. The gas generator is conventionally provided with at least one compressor 12, a combustion chamber 13, and at least one expansion turbine 14 connected to the compressor 12 by a main shaft 13.

(8) FIG. 1 shows a single compressor 12 and a single expansion turbine 14. Nevertheless, the numbers of compressors and of expansion turbines can be optimized depending on requirements, and put no restriction on the scope of the invention.

(9) Furthermore, the compressor 12, the expansion turbine 14, and the main shaft 13 connecting them together mechanically are suitable for rotating together about a longitudinal axis AX of the engine. More precisely, the compressor 11, the expansion turbine 14, and the main shaft 13 are constrained to rotate together about this longitudinal axis.

(10) The speed of rotation of the gas generator must thus be understood as being the first speed of rotation N1 of the rotary assembly of the gas generator that comprises the compressor 12 together with the expansion turbine 14 and the main shaft 13.

(11) Furthermore, the engine 10 has a power assembly 19 situated downstream from the gas generator. The power assembly is driven by the gas generated by the combustion chamber.

(12) The power assembly 19 comprises at least one power turbine 15 situated downstream from the combustion chamber 13. The power turbine may be connected to the gas generator or it may be independent of the gas generator, as shown in FIG. 1.

(13) Under such circumstances, the power turbine 15 is secured to a power shaft 16 suitable for driving an element outside the engine, such as the main gearbox 3, for example.

(14) FIG. 1 shows a power assembly including a single power turbine 15. Nevertheless, the number of power turbines may be optimized depending on requirements, and puts no restriction on the scope of the invention.

(15) The gas leaving the combustion chamber then causes the power assembly of the engine to rotate at a second speed of rotation N2.

(16) Furthermore, the aircraft 1 has an air inlet 17 conveying the air present in the outside medium EXT surrounding the aircraft to the gas generator 11.

(17) This air inlet may include filter means 18, such as a grid, for example.

(18) Furthermore, the aircraft 1 has a detector device 20 for detecting whether the aircraft is flying under icing conditions.

(19) The detector device 20 includes a processor unit 21. The processor unit 21 has a storage device 23 and a calculation unit 22. By way of example, the calculation unit may comprise a processor or the equivalent executing instructions stored in the storage device. The storage device may include a non-volatile memory storing such instructions and a volatile memory storing parameter values, for example.

(20) The processor unit may be an integral portion of a control system of a turboshaft engine, such as a system known as an engine control unit (ECU) or as a full authority digital engine control (FADEC). Under such circumstances, the calculation unit of the processor unit is the calculation unit of the control system, the storage device being the storage device of the control system.

(21) The storage device stores a theoretical model 24 of the operation of the engine. This theoretical model 24 is usually obtained by testing. Under such circumstances, the theoretical model 24 determines the power delivered by the power assembly of the engine as a function of at least the first speed of rotation N1 of the engine.

(22) In particular, the theoretical model 24 can provide a bench guaranteed minimum power Wmini of the engine. This bench guaranteed minimum power Wmini represents the power that the manufacturer guarantees throughout the lifetime of the engine. This bench guaranteed minimum power Wmini is determined by performing tests on test benches, and thus away from an aircraft.

(23) The theoretical model 24 can then deliver the bench guaranteed minimum power Wmini as a function: of the outside pressure P0 and of the outside temperature T0 of the air penetrating into the engine, and thus of the air present in the outside medium EXT situated outside the aircraft; of the first speed of rotation N1 of the gas generator; and of the second speed of rotation N2 of the power assembly.

(24) This theoretical model 24 may be in the form of a mathematical relationship stored in the storage device 23, or in a database, for example.

(25) In order in particular to determine the values of the parameters used in the theoretical model 24, the processor unit is connected via wired and/or wireless connections to:

(26) a temperature sensor 45 that continuously measures the outside temperature T0 of the air in the outside medium EXT;

(27) a pressure sensor 50 that measures the outside pressure P0 of that air;

(28) speed measurement means 65 measuring the first speed of rotation N1; and a conventional speed measurement system 35 measuring the second speed of rotation N2.

(29) Furthermore, the storage device can store a model 25 of installation losses. This model 25 of installation losses is usually obtained by testing. Under such circumstances, the model of installation losses serves to determine the installation losses Wpi of the engine continuously during a flight, these installation losses Wpi representing a loss of power in newton meters (Nm) resulting from the engine being installed on an aircraft.

(30) The installation loss model 25 can then deliver the installation losses Wpi as a function: of the outside pressure P0 and of the outside temperature T0 of the air penetrating into the engine, and thus of the air present in the outside medium EXT situated outside the aircraft 1; and of a travel speed IAS of the aircraft.

(31) In particular for the purpose of determining the value of the travel speed IAS, the processor unit is connected by wired and/or wireless links to a conventional speed measurement device 60 that measures the travel speed IAS of the aircraft.

(32) Furthermore, the processor unit is connected by wired and/or wireless connections to a conventional torque measurement system 30 that measures the torque developed by the power assembly 19.

(33) In addition, the detector device 20 may include a conventional engine health monitor system 55 co-operating with the processor unit 21.

(34) This engine health monitoring system 55 may be an integral portion of an ECU or FADEC control system of the engine.

(35) Under such circumstances, the engine health monitoring system 55 may be embodied by a segment of code stored in a storage device, the processor unit having another segment of code stored in the storage device.

(36) Furthermore, the detector device is provided with a warning system 40 suitable for generating a visible or audible warning 41 on order from the processor unit 21.

(37) The detector device 20 serves to apply the method of the invention as shown in FIG. 2 at a predetermined sampling frequency.

(38) During a first stage STP 1, the processor unit determines a theoretical power Wt that ought in theory to be developed by the engine 10. This theoretical power Wt thus represents the power that the engine ought to be developing under normal conditions, i.e. in the absence of failures or clogging, e.g. as a result of ice being deposited.

(39) Consequently, the processor unit runs the theoretical model of the engine in order to determine this theoretical power Wt.

(40) For example, during a first step STP 1.1 of the first stage STP 1, the processor unit 32 determines a bench guaranteed minimum power Wmini by applying the theoretical model 24.

(41) The theoretical power may be equal to this bench guaranteed minimum power Wmini.

(42) Nevertheless, the processor unit 21 can determine the theoretical power by correcting the bench guaranteed minimum power Wmini with the help of at least one parameter selected from a list including the installation losses Wpi and the operating margin CSM.

(43) Thus, during a second step STP 1.2 of the first stage STP 1, the processor unit can correct the bench guaranteed minimum power Wmini as a function of the installation losses Wpi.

(44) Thereafter, the processor unit determines the installation losses Wpi as a function of a stored installation loss model 25.

(45) Under such circumstances, the processor unit injects, e.g. into the installation loss model 25, the measured values of the outside pressure P0, of the outside temperature T0, and of the travel speed IAS.

(46) The processor unit then deduces therefrom the installation losses Wpi.

(47) Under such circumstances, the processor unit determines an engine-installed guaranteed minimum power on the basis of the following relationship in which Wins represents said engine-installed guaranteed minimum power, Wmini represents said bench guaranteed minimum power, and Wpi represents the installation loses, and represents the subtraction sign:
Wins=WminiWpi

(48) The theoretical power can then be equal to the engine-installed guaranteed minimum power Wins.

(49) Nevertheless, during a third step STP 1.3 of the first stage STP 1, the processor unit can correct the engine-installed guaranteed minimum power Wins as a function of operating margins.

(50) Under such circumstances, the processor unit consults the operating margin determined during the most recent health check of the engine.

(51) An engine health check is performed periodically by the engine health monitoring system. On each health check, the detector device stores the operating margin as determined.

(52) Consequently, the processor unit determines the theoretical power from the following sum, where Wt represents said theoretical power, Wins represents said engine-installed guaranteed minimum power, CSM represents the operating margin, and + represents the addition sign;
Wt=Wins+CSM

(53) In a variant, the theoretical power is obtained by correcting the bench guaranteed minimum power by adding thereto the operating margin, and then deducting therefrom the installation losses.

(54) In another variant, the theoretical power is obtained by correcting the bench guaranteed minimum power by adding thereto the operating margin and subtracting therefrom simultaneously the installation losses.

(55) In another variant, the theoretical power is obtained by correcting the bench guaranteed minimum power solely by adding thereto the operating margin.

(56) Independently of the variant, the processor unit acts during a second stage STP 2 to determine a real power Wr as developed by the engine 10.

(57) This stage is referred to as the second stage for convenience. Nevertheless, the second stage can be performed at the same time as the first stage STP 1, or even before the first stage STP 1.

(58) Consequently, the processor unit determines the real power by applying the following relationship where Wr represents said real power, Tq represents the torque measured by the torque measurement system 30, N2 represents the second speed of rotation as measured by the speed measurement system 35, and * represents the multiplication sign:
Wr=Tq*N2

(59) During a third stage STP 3, the processor unit determines whether three conditions are satisfied.

(60) Under such circumstances, the processor unit determines a power difference between the real power Wr and the theoretical power, using the following relationship:
=WrWt

(61) If the power difference is greater than a power threshold SP, then the processor unit deduces that the first condition is satisfied.

(62) The power threshold SP may have a value of 150 Nm.

(63) In addition, when the power threshold is exceeded, a time count is started, this time count being compared with a time threshold. If the power difference remains greater than the power threshold until the time count reaches the time threshold SIPS, then the processor unit deduces that the second condition is satisfied.

(64) Consequently, the first condition and the second condition are both satisfied if the power difference is greater than the predetermined power threshold SP for a continuous duration that is greater than a time threshold SIPS.

(65) For example, the power difference needs to remain greater than the power threshold SP for 30 second(s) in order to cause the processor unit to consider that both the first and second conditions are satisfied.

(66) Furthermore, the processor unit compares the outside temperature T0 with a low temperature threshold SINF, of the order of 10 degrees Celsius ( C.) and to a high temperature threshold SSUP, of the order of +5 C.

(67) If the outside temperature lies between the low threshold SINF and the high threshold SSUP, the processor unit considers that the third condition is satisfied.

(68) Under such circumstances, during a fourth stage STP 4, the processor unit triggers a warning by sending a warning signal to the warning system 40 when all three above conditions are satisfied simultaneously.

(69) Naturally, the present invention may be subjected to numerous variations as to its implementation. Although several embodiments are described, it will readily be understood that it is not conceivable to identify exhaustively all possible embodiments. It is naturally possible to replace any of the means described by equivalent means without going beyond the ambit of the present invention.