Method of stopping a rotorcraft engine in overspeed, and a system and a rotorcraft associated therewith

Abstract

A method of stopping an engine of a rotorcraft in overspeed, the engine comprising a gas generator and a power assembly. When the engine is in operation, the engine is automatically stopped when the following three conditions are satisfied simultaneously: a torque (Tq) measured on the power assembly is below a predetermined torque threshold (Tq1); and a speed of rotation referred to as a first speed of rotation (N1) of the gas generator is above a threshold referred to as a first speed threshold (S1); and a speed of rotation referred to as a second speed of rotation (N2) of the power assembly is above a threshold referred to as a second speed threshold (S2).

Claims

1. A method of stopping an engine of a rotorcraft in overspeed, the engine including a gas generator and a power assembly, the power assembly having a power turbine set in rotation by gas coming from the gas generator, the power assembly having a power shaft constrained to rotate with the power turbine; wherein when the engine is in operation, the engine is automatically stopped when the following three conditions are detected simultaneously: a torque (Tq) measured on the power assembly is below a predetermined torque threshold (Tq1); and a speed of rotation (N1) of the gas generator is above a first speed threshold (S1), the first speed threshold (S1) being determined based on a nominal speed of rotation of the gas generator; and a speed of rotation (N2) of the power assembly is above a second speed threshold (S2), the second speed threshold (S2) being determined based on a nominal speed of the power assembly.

2. The method according to claim 1, wherein the gas generator is fed by a fuel-metering device, the fuel-metering device is suitable for being set between a minimum limit inducing a zero fuel flow rate and a maximum limit inducing a maximum fuel flow rate, and the engine is stopped automatically by setting the fuel-metering device of the engine at the minimum limit when the three conditions are detected simultaneously.

3. The method according to claim 1, wherein the engine includes a cock on a fuel pipe, and the engine is automatically stopped by closing the cock when the three conditions are detected simultaneously.

4. The method according to claim 1, wherein the engine is fed with fuel by a pump, and the engine is automatically stopped by shutting down the pump when the three conditions are detected simultaneously.

5. The method according to claim 1, wherein the torque (Tq) is measured by arranging a torque measuring system on the power shaft.

6. An overspeed safety system for stopping an engine of a rotorcraft in overspeed, the engine including a gas generator and a power assembly, the power assembly having (i) a power turbine set in rotation by the gas generator and (ii) a power shaft constrained to rotate with the power turbine, the rotorcraft further including a rotor and a power transmission train connected to the rotor, the power assembly connected to the power transmission train for the engine to drive the power transmission train to drive the rotor, the overspeed safety system comprising: a first speed sensor for measuring a speed of rotation (N1) of the gas generator; a second speed sensor for measuring a speed of rotation (N2) of the power assembly; a torque sensor for measuring a torque (Tq) transmitted by the power assembly; a shutdown system configured to stop operation of the engine; a processor connected to the shutdown system, the first speed sensor, the second speed sensor, and the torque sensor; wherein the processor is configured to control the shutdown system to stop the engine automatically when the following three conditions are detected simultaneously: the torque (Tq) transmitted by the power assembly is below a predetermined torque threshold (Tq1); the speed of rotation (N1) of the gas generator is above a first speed threshold (S1), the first speed threshold (S1) being determined based on a nominal speed of rotation of the gas generator; and the speed of rotation (N2) of the power assembly is above a second speed threshold (S2), the second speed threshold (S2) being determined based on a nominal speed of rotation of the power assembly; wherein the three conditions are detected simultaneously when overspeed of the engine is caused by a breakage of the power transmission train.

7. The overspeed safety system according to claim 6 wherein: the shutdown system includes a fuel-metering device conveying fuel to the gas generator.

8. The overspeed safety system according to claim 6 wherein: the shutdown system includes a pump conveying fuel to the gas generator.

9. The overspeed safety system according to claim 6 further comprising: a shield ring surrounding the power turbine, the power turbine including a plurality of blades, each blade being fastened to a fuse member.

10. The overspeed safety system according to claim 6 wherein: the processor is a FADEC.

11. A rotorcraft comprising: a rotor; an engine, the engine driving a power transmission train connected to the rotor, the engine including a gas generator and a power assembly, the power assembly having a power turbine set in rotation by the gas generator, the power assembly further having a power shaft constrained to rotate with the power turbine; an overspeed safety system for the engine, the overspeed safety system including a shutdown system for stopping operation of the engine and a processor unit connected to the shutdown system; and wherein the overspeed safety system further includes a first speed sensor for measuring a speed of rotation (N1) of the gas generator, a second speed sensor for measuring a speed of rotation (N2) of the power assembly, and a torque measuring system for measuring a torque (Tq) transmitted by the power assembly, the processor unit being connected to the first speed sensor, the second speed sensor, and the torque measuring system, and the processor unit being configured to stop the engine automatically when the following three conditions are detected simultaneously: the torque (Tq) transmitted by the power assembly is below a predetermined torque threshold (Tq1); the speed of rotation (N1) of the gas generator is above a first speed threshold (S1), the first speed threshold (S1) being determined based on a nominal speed of rotation of the gas generator; and the speed of rotation (N2) of the power assembly is above a second speed threshold (S2), the second speed threshold (S2) being determined based on a nominal speed of rotation of the power assembly.

12. The rotorcraft according to claim 11, wherein the shutdown system comprises a fuel-metering device conveying fuel to the gas generator.

13. The rotorcraft according to claim 11, wherein the shutdown system comprises at least one pump conveying fuel to the gas generator.

14. The rotorcraft according to claim 11, wherein the overspeed safety system includes a shield ring surrounding the power turbine, the power turbine comprising a plurality of blades, each blade being fastened to a fuse member.

15. The rotorcraft according to claim 11, wherein the processor unit is a FADEC of the engine.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

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

(2) FIG. 1 shows a rotorcraft provided with a single engine; and

(3) FIG. 2 shows an aircraft provided with two engines.

DETAILED DESCRIPTION OF THE INVENTION

(4) FIG. 1 shows an aircraft 1, in particular a rotorcraft. The members of the aircraft that are not directly involved in the invention are not shown in the figure in order to avoid overloading the figure pointlessly.

(5) In particular, this aircraft 1 is a rotorcraft including a lift and/or propulsion rotor 2. This rotor 2 is rotated by a power plant including at least one engine 10 and one power drive train 3. Such a power drive train 3 includes for example a free wheel 56 and a main gear box 55. The main gearbox 55 is provided with a mast driving a hub of the rotor 2.

(6) Consequently, at least one engine 10 is mechanically connected to said power drive train 3.

(7) The engine 10 of the rotorcraft is in particular a turboshaft engine.

(8) Consequently, the engine 10 includes a gas generator 11. Conventionally, the gas 11 generator is provided with at least one compressor 12, a combustion chamber 13, and at least one expansion turbine 14. The expansion turbine 14 is connected rigidly to the compressor 12 by a shaft referred to as a drive shaft 13.

(9) FIG. 1 presents a single compressor 12 and a single expansion turbine 14. Nevertheless, the number of compressor(s), and expansion turbine(s) may be optimized according to requirements, and does not restrict the ambit of the invention at all.

(10) In addition, the compressor 12, the expansion turbine 14 and the drive shaft 13 are suitable for rotating jointly about a longitudinal axis AX of the engine 10. More precisely, the compressor 12, the expansion turbine 14, and the drive shaft 13 are constrained to rotate together about this longitudinal axis.

(11) The speed of rotation of the gas generator should thus be understood as being the speed referred to as the first speed of rotation N1 of the rotary assembly of the gas generator that includes the compressor 12 together with the expansion turbine 14 and the drive shaft 13.

(12) In addition, the engine 10 comprises a power assembly 19 located downstream from the gas generator. The power assembly is set in movement by the gas generated by the gas generator.

(13) The power assembly 19 comprises at least one power turbine 15 located downstream from the gas generator. The term downstream is to be considered relative to the direction of gas flow within the engine 10.

(14) This power turbine may be connected to the gas generator. However, in FIG. 1, the power turbine is a free turbine that is independent of the gas generator.

(15) Consequently, the power turbine 15 is secured to a power shaft 16 that is connected to the power transmission train 3. Conventionally, the power transmission train 3 is fastened to the power shaft by a member (not shown) for accommodating angular and axial misalignments.

(16) FIG. 1 shows a power assembly 19 including a single power turbine 15. Nevertheless, the number of power turbine(s) may be optimized depending on requirements, and does not restrict the ambit of the invention at all.

(17) The gas leaving the gas generator then sets in rotation the power assembly of the engine at a speed of rotation referred to as the second speed of rotation N2.

(18) In addition, the rotorcraft comprises at least one tank 4 of fuel 6 for feeding the combustion chamber 13 with fuel.

(19) Consequently, a fuel feed line provided with at least one pump 5 and a metering device 7 connects the tank 4 to the combustion chamber 13. The engine may further comprise a cock 100 on an internal fuel pipe.

(20) The rotorcraft is further provided with an overspeed safety system 20 in order to avoid overspeeding of the engine 10.

(21) This overspeed safety system 20 comprises a processor unit 21.

(22) The processor unit may include a logic circuit or equivalent.

(23) In the variant shown in FIG. 1, the processor unit 21 is for example provided with a storage device 23 and a computer 22. By way of example, the computer may include a processor or the equivalent for executing instructions stored in the storage device for applying the method of the invention. This storage device may include a non-volatile memory 24 storing such instructions and a volatile memory 25 storing parameter values, for example.

(24) The processor unit 21 may be an integral part of a system for controlling a turboshaft engine, such as a system known under the acronym ECU for Engine Control Unit or FADEC for Full Authority Digital Engine Control. Consequently, the computer of the processor unit is the computer of the control system, the storage device being the device for storing said control system.

(25) The processor unit 21 is connected by wired and/or wireless connections to a speed sensor referred to as the first speed sensor 65. The first speed sensor 65 is arranged on the gas generator in order to measure the first speed of rotation N1 of the gas generator.

(26) Consequently, the first speed sensor 65 transmits a signal conveying the first speed of rotation N1 to the processor unit.

(27) The processor unit 21 is also connected by wired and/or wireless connections to a speed sensor referred to as the second speed sensor 30. The second speed sensor 30 is arranged on the power assembly in order to measure the speed of rotation N2 of said power assembly.

(28) Consequently, the second speed sensor 30 transmits a signal conveying the second speed of rotation N2 to the processor unit.

(29) Furthermore, the processor unit 21 is also connected by wired and/or wireless connections to a torque measuring system 35.

(30) This torque measuring system 35 is arranged on the power assembly in order to measure the torque Tq exerted on the power assembly 19.

(31) Under such circumstances, the torque measuring system 35 transmits to the processor unit a signal conveying the torque transmitted by the power assembly to the power transmission train.

(32) In addition, the processor unit 21 is connected to a shutdown system 40 suitable for stopping the engine 10. This shutdown system comprises the metering device 7 and/or the cock 100 feeding the engine 10 with fuel.

(33) Under such circumstances, according to the method applied, the processor unit acts on the shutdown system 40 to stop the engine 10 when:

(34) the torque Tq transmitted by the power assembly 19 is below a predetermined torque threshold Tq1, such as a torque threshold Tq1 of the order of 5% to 10% of the torque obtained when the engine develops a power known as its maximum take-off power PMD, for example; and

(35) the first speed of rotation N1 of the gas generator is above a first speed threshold S1, such as a first speed threshold S1 of the order of 70% to 75% of a nominal speed of rotation of the gas generator obtained when the engine develops its maximum take-off power PMD, for example; and

(36) the second speed of rotation N2 of the power assembly is above a second speed threshold S2, such as a second speed threshold S2 of the order of 120% to 125% of the nominal speed of rotation of the power assembly, for example.

(37) In normal operation, the lift rotor is driven in rotation at a nominal speed, said nominal speed imparting a nominal speed of rotation of the power assembly known to the person skilled in the art.

(38) Consequently, when the three above-described criteria are satisfied simultaneously, the shutdown system makes it possible to stop the rotary movement of the power assembly 19 and of the gas generator 11.

(39) In the event of a crash, the risks of oil igniting because of hot gas escaping unduly from the engine are then reduced.

(40) If necessary, each pump 5 is also shut off.

(41) In addition to an electronic system, the overspeed safety system may include a mechanical system of the blade shedding type.

(42) Consequently, each blade 51 of the power turbine 15 may be fastened to a hub by a fuse member 52. This fuse member is dimensioned so as to break in the event of overspeed.

(43) In the example shown, each blade is fastened to the power shaft by a fuse member.

(44) In addition, the overspeed safety system comprises a shield ring 50 for containing the blades inside the engine 10.

(45) The invention applies to a rotorcraft provided with a single engine 10 in accordance with the embodiment of FIG. 1.

(46) Nevertheless, the invention also applies to a rotorcraft including a plurality of engines 10 in accordance with the embodiment of FIG. 2.

(47) Consequently, at least one engine 10 is provided with an overspeed safety system 20. Preferably, each engine 10 includes this overspeed safety system 20.

(48) Naturally, the present invention may be subjected to numerous variants as to its implementation. Although several implementations are described, it should readily be understood that it is not conceivable to identify exhaustively all possible implementations. It is naturally possible to envisage replacing any of the means described by equivalent means without going beyond the ambit of the present invention.