Patent Application
20160312706
The invention relates to the general field of aircraft engine fuel circuit architectures having a fuel return (“Motive Flow”) tapping an engine fuel system.
This aircraft pump needs to be supplied with electricity.
To avoid having systematic recourse to this aircraft pump, a jet pump 12 operating using the venturi effect, is also immersed in the tank 10 and makes it possible to take over from the aircraft pump under certain conditions.
This jet pump 12 needs a hydraulic power source which is in known fashion supplied by a fuel return pipe 2 connected to the engine fuel system 20.
This return pipe 2 makes it possible to send into the jet pump 12 pressurized fuel taken from the engine fuel system 20.
To accomplish this, a fuel return valve 30 C Motive Flow Valve') can be positioned along the return pipe 2 so as to block it, under certain conditions depending on the design and the performance of the fuel system and in particular based on the rotation speed N2 of the aircraft engine.
It often happens that the valve has a failure and remains blocked in the open position so that it allows fuel from the engine fuel system 20 to be sent into the fuel tank 10 when it should not do so. This causes deterioration in the performance of the engine because the stream of fuel withdrawn to be sent into the fuel tank causes a reduction in the flow rate (pressure) of the flow sent to the engine.
Consequently there exists a need to detect a failure in the fuel return valve.
The invention responds to this need and proposes, according to a first aspect, a method for detecting a failure in a fuel return valve of an aircraft engine fuel circuit, said fuel circuit including:
a fuel tank;
an engine fuel system connected to the fuel tank, said fuel system including a high pressure pump delivering a flow rate Q, depending on a power setting of said engine, to an actuating ram capable of actuating variable geometries, a cutoff valve capable of supplying the actuating ram positioned in a supply pipe of said engine;
a fuel return pipe connected on the one hand downstream of the high-pressure pump and upstream of the cutoff valve and, on the other hand, to the fuel tank;
a fuel return valve arranged to switch between an open position and a closed position, said fuel return valve being capable of blocking, in the closed position, the fuel return pipe and to put, in the open position, the fuel return pipe into communication with the fuel tank;
the method including the following steps, implemented in a calculator:
starting the engine at a power setting NO;
increasing the engine power setting until the flow rate Q reaches a predetermined value Q0 sufficient for opening the cutoff valve;
measuring, on the one hand, the position of the actuating ram and on the other hand the engine power setting N corresponding to the opening of said cutoff valve.
The invention is advantageously supplemented by the following features, taken alone or in any one of their technically possible combinations:
a fuel tank;
an engine fuel system connected to the fuel tank, said fuel system including a high pressure pump delivering a flow rate Q, depending on the power setting of said engine, to an actuating ram capable of actuating variable geometries, a cutoff valve capable of feeding the actuation ram positioned in a supply pipe of said engine;
a fuel return channel connected on the one hand downstream of the high-pressure pump and upstream of the cutoff valve, and on the other hand to the fuel tank;
a fuel return valve arranged to switch between an open position and a closed position, said fuel return valve being capable of blocking, in the closed position, the fuel return pipe and, in the open position, to put into communication the fuel return pipe with the fuel tank;
a calculator configured to implement the following steps:
starting the engine at an engine power setting N0;
increasing the engine power setting until the flow rate Q reaches a predetermined value Q0 sufficient for opening the cutoff valve;
measuring, on the one hand, the position of the actuating ram, and on the other hand of the engine power setting N corresponding to the opening of said cutoff valve.
Advantageously, the high-pressure pump is a positive displacement pump.
According to a third aspect, the invention proposes an aircraft including an engine supplied with fuel by a fuel circuit according to the second aspect of the invention.
Other characteristics, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings wherein, besides
In all the figures, similar elements have identical reference symbols.
With relation to
This cutoff valve 22 opens when the flow rate applied to it makes it possible to reach a precisely known setting threshold of its spring 22a. It allows, on the one hand, the activation of one or more ram(s) 23 providing for movement of variable geometries (not shown) through an associated servo-valve 24 connected by an upstream pipe 25 to the high-pressure pump and by a downstream pipe 26 to a cutoff valve 22, and on the other hand supply of the engines (not shown) by putting them into communication with the high pressure pump 21.
The fuel system 20 further includes a calculator 28 connected to the different components of the fuel system 20 and provides for its general control based on various data, such as the desired engine power setting N or the displacement of the piston 23a of the ram 23 measured by a linear variable displacement transducer (LVDT) sensor 23b.
In the embodiment described here, a single ram 23 is illustrated, but naturally in the case where there are several rams 23, each includes a sensor 23b for measuring the displacement of the piston.
In addition, a flow recirculating pipe 27 of the cutoff valve is connected to the downstream pipe 26 by means of the cutoff valve 22.
Of course, the fuel system 20 includes other known components (for example filters, valves, exchangers, . . . ) the description of which does not seem necessary for understanding the invention, and which are therefore not shown.
The feeding of the high-pressure pump 21 (preferably a positive displacement pump) being provided for by a low-pressure pump (not shown) located upstream, this high pressure pump 21 delivers a flow rate Q depending on the engine power setting N2 toward the ram 23 (through the servo-valve 24) and the cutoff valve 22.
When the cutoff valve 22 is in a closed state (
As soon as the pressure level of the cutoff valve 22 exceeds a setting threshold of the spring 22a, that is when the flow rate that it sees is sufficiently high, it switches into a state of complete opening (
The ram being equipped with an LVDT sensor 23b, it is then possible, by means of the calculator 28, to detect precisely the moment when the piston is moved, thus corresponding to the opening of the cutoff valve 22, and to read the associated engine power setting N2.
According to the invention, to detect a failure in the fuel return valve, the applicant has noted that the engine power setting for which the ram opens is linked to the state of the fuel return valve.
Indeed, the cutoff valve is displaced depending on the flow rate passing through it (hence the power setting), and when it reaches a certain position, it opens an opening which makes it possible to free the movement of the ram. It is only at this moment that the variable geometries can move and follow their set point in position.
So as not to prevent this operation, it is necessary to keep the fuel return valve closed before movement of the cutoff valve. Indeed, tapping of the fuel flow by the fuel return valve, being located upstream of the cutoff valve, the tapped flow is one less flow passing through it and thus influences the power setting which actuates it if ever it was open at the time when the variable geometries are moving. If it therefore the detection of an offset in the opening operation of the ram which makes it possible to detect a failure in the fuel return valve.
The detection of a failure in the fuel return valve is implemented in the calculator according to a method described below in relation to
The engine is started (step E1) at a low initial power setting N0 and the cutoff valve 22 is closed.
First of all, the calculator 28 proceeds with the activation command (step E2) of the ram 23. However, the cutoff valve being closed, the ram cannot respond to this command and therefore remains immobile. In parallel with this command, the engine power setting N is progressively increased (step E3). As long as the flow rate sent to the cutoff valve 22 is not sufficient, the latter remains closed and the ram 23 does not move. When the flow rate is sufficient (predetermined value Q0 corresponding to the setting threshold of the spring 12A), the cutoff valve 22 opens and the ram 23 then goes into movement.
The engine power setting N corresponding to the opening of the cutoff valve 22 and therefore to the movement of the ram is read thanks to the LVDT 23b of the ram 23 to which the calculator 28 is connected, and stored in the latter (step E4 and step E5).
If the power setting for which the ram begins to move is greater than a predetermined threshold, then the fuel return valve has failed and a failure is detected (step E6 and step E7).
On the other hand, if the power setting for which the ram begins to move is equal to the predetermined threshold, then the fuel return valve is operating correctly.
This threshold depends on several factors and particularly on the type of fuel used, the temperature of the fuel, manufacturing tolerances as well as the aging of the equipment.
It is noted in relation with
If a movement of the ram 23 is detected from an N2 of X1%, then the fuel return valve has not failed (curve 43) and if a movement of the ram 23 is detected later at at least an N2 of X2% (X2>X1) and preferably 8% later than an N2 of X1% then the fuel return valve has failed (curve 44). Typically, X1% amounts to 22% and X2% is at least 30%.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1360634 | Oct 2013 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FR2014/052724 | 10/27/2014 | WO | 00 |
