Fuel circuit of an aircraft engine with a fuel recirculating valve controlled by a pressure differential of a low-pressure pump of the fuel system

1. A fuel circuit of an engine of an aircraft comprising:

a fuel tank;

an engine fuel system comprising:

a low-pressure pump connected to the fuel tank, the low-pressure pump being capable of raising a pressure of a low-pressure stream of fuel from the fuel tank by a pressure difference which is variable; and

a high-pressure pump connected to the low-pressure pump, the high-pressure pump being capable of converting, the low-pressure stream of fuel into a high-pressure stream of fuel;

a fuel return line connected to the engine fuel system, the fuel return line being capable of bringing the high-pressure stream into the fuel tank; and

a motive flow valve arranged to switch between an open position and a closed position, as a function of the pressure difference of the low-pressure pump, the motive flow valve being capable of blocking the fuel return line in the closed position, and of putting the fuel return line in communication with the fuel tank, in the open position.

2. The fuel circuit of an aircraft engine according to claim 1 , wherein the motive flow valve switches from the closed position to the open position as a function of a taring threshold of a spring of the motive flow valve.

3. The fuel circuit of an aircraft engine according to claim 1 , comprising an actuating line connected, on one hand, upstream of the low-pressure pump and on the other hand, downstream of the low-pressure pump, the motive flow valve being disposed in said actuating line and is arranged to switch between the open and closed position as a function of the pressure difference prevailing in said actuating line.

4. The fuel circuit of an aircraft engine according to claim 1 , wherein the high-pressure pump is a positive displacement pump.

5. The fuel circuit of an aircraft engine according to claim 1 , further comprising a computer configured to implement the following steps:

starting of the aircraft engine in such a way as to increase an engine speed Ni from a zero speed to a minimum idle speed N0; and

during the increase of said engine speed, measuring, for several values of the engine speed Ni, of a corresponding temperature Ti of the low-pressure stream of fuel from the fuel tank.

6. The fuel circuit of an aircraft engine according to claim 5 , wherein the minimum idle speed N0 of the aircraft engine is at least equal to 50% N2, wherein N2 is a maximum rotation speed of the aircraft engine.

7. The fuel circuit of an aircraft engine according to claim 5 , wherein the computer is further configured to implement a step of determining a variation in a temperature of the low-pressure stream of fuel for an engine speed Ni<35% N2 and, if the variation is constant, a step of detecting a failure of the motive flow valve, the failure being that said motive flow valve is locked in the open position, wherein N2 is a maximum rotation speed of the aircraft engine.

8. The fuel circuit of an aircraft engine according to claim 5 , wherein the computer is further configured to implement a step of determining a variation in a temperature of the low-pressure stream of fuel for an engine speed Ni<35% N2 and, if the variation is constant and if an evolution of the temperature between 35% N2 and 50% N2 has no inflexion point, a step of detecting a failure of the motive flow valve, the failure being that said motive flow valve is locked in the open position, wherein N2 is a maximum rotation speed of the aircraft engine.

9. The fuel circuit of an aircraft engine according to claim 8 , wherein the measuring of the temperature Ti of the low-pressure stream of fuel from the fuel tank is carried out by means of a temperature sensor disposed along a line connecting the fuel tank to the engine fuel system.

10. An aircraft comprising an engine supplied with fuel by a fuel circuit according to claim 1 .