Method and a system for reliably starting a turbine engine

1. A starting system for reliably starting a turbine engine comprising a storage battery, a DC starter, an electronic regulation computer, a transmission gearbox, starting accessories for managing the distribution of fuel to injectors and for igniting the fuel during a starting stage, a gas generator comprising a compressor, a combustion chamber, a high pressure turbine, and a free turbine, the system comprising:

a first circuit and a second circuit connected in parallel between said storage battery and said DC starter, wherein the first circuit comprises a DC-DC converter connected in series with a first switch, and the second circuit comprises a second switch;

at least one sensor configured to sense a speed of rotation of the compressor;

a sensor configured to sense a temperature at an inlet to the free turbine; and

a control circuit configured to control the first and second switches as a function of information supplied by the at least one sensor configured to sense the speed of rotation of the compressor and by the sensor configured to sense the inlet temperature of the free turbine.

2. The starting system according to claim 1 , further comprising a diode connected in the first circuit in series with the DC-DC converter and the first switch.

3. The starting system according to claim 1 , wherein the DC starter is a starter-generator.

4. The starting system according to claim 1 , further comprising a sensor configured to sense a speed of rotation of the DC starter, wherein the DC-DC converter is configured to be servo-controlled by the sensor configured to sense the speed of rotation of the DC starter when said first switch is closed.

5. The starting system according to claim 4 , wherein the electronic regulation computer is configured to prepare a speed setpoint Nref corresponding to a preferred ignition window of the turbine engine and is configured to transmit the speed setpoint Nref to the DC-DC converter.

6. The starting system according to claim 1 , wherein the DC-DC converter is configured to be servo-controlled by the sensor configured to sense the speed of rotation of the compressor when said first switch is closed.

7. The starting system according to claim 6 , wherein the electronic regulation computer is configured to prepare a speed setpoint Nref corresponding to a preferred ignition window of the turbine engine, is configured to prepare a torque setpoint Cref, and is configured to transmit the torque setpoint Cref to the DC-DC converter.

8. The starting system according to claim 1 , wherein the DC-DC converter includes an electromagnetic compatibility filter, a pre-load circuit, and a buck type chopper.

9. The starting system according to claim 1 , wherein the electronic regulation computer is configured to prepare respective logic signals SL 1 , SL 2 that are applied for actuating the first and second switches.

10. The starting system according to claim 1 , wherein the electronic regulation computer is configured to detect that the speed of rotation NG of the compressor has exceeded a predetermined threshold and is configured to deactivate the first and second switches and the starting accessories.

11. The starting system according to claim 1 , further comprising a control circuit for the DC-DC converter, the control circuit for the DC-DC converter comprising both a speed servo-control loop and a current servo-control loop.

12. The starting system according to claim 11 , wherein said speed servo-control loop and said current servo-control loop are incorporated in an independent controller circuit configured to control the DC-DC converter.

13. The starting system according to claim 11 , wherein said speed servo-control loop is incorporated in said electronic regulation computer and said current servo-control loop is incorporated in an independent controller circuit configured to control the DC-DC converter.

14. The starting system according to claim 1 , wherein said system is applied to an aircraft turbine engine.

15. A starting method for reliably starting a turbine engine comprising a storage battery, a DC starter, an electronic regulation computer, a transmission gearbox, starting accessories for managing the distribution of fuel to injectors and for igniting the fuel during a starting stage, a gas generator comprising a compressor, a combustion chamber, a high pressure turbine, and a free turbine, the starting method comprising:

connecting a first circuit and a second circuit in parallel and interposing said first and second circuits between said storage battery and said DC starter, the first circuit comprising a DC-DC converter connected in series with a first switch, and the second circuit comprising a second switch;

measuring a speed of rotation of the compressor;

measuring a temperature at an inlet of the free turbine; and

controlling said first and second switches as a function of measurement information concerning the speed of rotation of the compressor and the temperature at the inlet of the free turbine.

16. The starting method according to claim 15 ,

wherein when initializing the starting, the starting accessories are activated and simultaneously a speed setpoint Nref is transmitted to said DC-DC converter, the speed setpoint corresponding to a preferred ignition window of the turbine, and said first switch is closed while activating the DC-DC converter to accelerate the compressor and then to regulate the voltage delivered to the starter so as to regulate the acquisition of speed by said compressor to the speed setpoint Nref, and

wherein when said speed setpoint Nref is reached, the combustion chamber of the turbine engine is ignited, the temperature at the inlet of the free turbine is measured, and once a rise in temperature is detected confirming that the combustion chamber has ignited, the second switch is closed, the first switch is opened, and the DC-DC converter is deactivated, and after detecting that the speed of rotation of the compressor has exceeded an end-of-starting threshold, the starting accessories are deactivated and the second switch is opened.