US20130115055A1

US20130115055A1 - System for controlling a pneumatic valve of a turbine engine

Info

Publication number: US20130115055A1
Application number: US13/669,999
Authority: US
Inventors: Lauranne Sophie MOTTET; Marie GENTILHOMME; Nicolas Potel
Original assignee: SNECMA SAS
Current assignee: Safran Aircraft Engines SAS
Priority date: 2011-11-07
Filing date: 2012-11-06
Publication date: 2013-05-09
Also published as: GB2496292A; GB201219325D0; FR2982319B1; FR2982319A1

Abstract

A system (110) for controlling a pneumatic valve (112) of a turbine engine, such as a bleed valve, the system comprising a directional control valve (140) for controlling air under pressure connected between the valve (112) that is to be controlled, a controlling solenoid valve (118), and means (144) for taking off air at a pressure P1, the solenoid valve also including a first inlet (132) connected to a source of fluid at a pressure P2 that is independent of P1, the opening and closing of the pneumatic valve being controlled by a flow of the air at pressure P1 delivered by the directional control valve that is controlled by the fluid at pressure P2 delivered by the solenoid valve.

Description

BACKGROUND OF THE INVENTION

The invention relates to a system for controlling a pneumatic valve of a turbine engine, and in particular a pneumatic bleed valve of a turbine engine.
Document EP-B1-0 374 004 describes a bleed valve for a turbine engine.
In general, a turbine engine has at least one bleed valve for bleeding air from the primary stream delivered by the high-pressure compressor of the turbine engine during certain stages of operation of the engine, such as starting, accelerating, deceleration, and idling. Air is bled into the secondary (bypass) stream and serves to impart a greater margin to the high-pressure compressor.
It is known to provide a turbine engine with a pneumatically controlled bleed valve, in which the opening of the valve is controlled by air under pressure taken form the high-pressure compressor of the turbine engine.
A bleed valve is designed to be in a closed position in normal operation mode. The bleed valve generally needs to be fed with air at a pressure greater than the bleed pressure from said valve in order to open the valve, i.e. the air for controlling the valve needs to be taken from a stage of the compressor that is situated downstream from the bleed valve. The valve is closed by interrupting the flow of air for controlling the valve.
In the prior art, the bleed valves of a turbine engine are connected to control means that include solenoid valves (i.e. electro-valves or electrically-controlled valves), each of those solenoid valves having an inlet connected to means for taking off air from the compressor and an outlet connected to the valve that is to be controlled so as to control the valve directly with the air taken from the compressor.
Such a solenoid valve includes an electrical portion that is sensitive to temperature. It is therefore necessary to avoid mounting solenoid valves close to the bleed valves where temperatures in operation are relatively high. Proposals have therefore been made to mount such solenoid valves in the nacelle of the turbine engine where ambient temperatures are much lower.
Furthermore, solenoid valves must not be fed with air that is too hot. The conventional components of such solenoid valves are designed to operate with feed temperatures of the order of 200° C. to 300° C., which is well below the temperature of the air used for controlling the bleed valves, which may be as high as 627° C. or even more (717° C.) in the event of a fuel metering valve failure leading to over speed.
There is therefore incompatibility between the requirement to have high pressure for controlling opening of the bleed valves and the requirement to have low temperature in the air that is fed to the solenoid valves for controlling the bleed valve.
Solutions have already been proposed to that problem.
A first solution consists in cooling the air fed to the solenoid valves, e.g. by convection. Under such circumstances, the air taken from the high-pressure compressor flows along pipework in which it is cooled by exchanging heat with the outside environment.
However, that solution cannot be implemented in certain engines, in particular in those where the air that is taken off is too hot and would require cooling that is greater than the cooling capacity available from heat exchange with the environment. Cooling capacity may be low for various reasons such as passing through an arm for passing services in an intermediate casing that is poorly ventilated, or the need to lag the pipework in the nacelle in order to avoid skin temperatures exceeding 200° C.
Another solution to the above-mentioned problem consists in feeding the bleed valves with air at a pressure that is substantially equal to the bleed pressure of those valves instead of with air at a higher pressure, thus making it possible to reduce the associated temperature. As described in U.S. Pat. No. 6,981,842, the bleed valve then needs to have a particular configuration (FIGS. 4-6 of U.S. Pat. No. 6,981,842).
That solution is not applicable to engines fitted with high-pressure bleed valves and with solenoid valves having a maximum feed air temperature of 200° C. Even if the control air for those solenoid valves is taken at a pressure equivalent to the bleed pressure, the temperature of the air remains too high since it may be as much as 461° C., or even more (543° C.) in the above-mentioned circumstances of a fuel metering valve failure leading to over speed.
Finally, a last known solution to the above-mentioned problem consists in feeding bleed valves with air at a pressure lower than the bleed pressure and thus at temperatures that are lower.
That solution is not satisfactory either since, in order to control a bleed valve with air under pressure, if the air is at a pressure lower than the bleed pressure of the valve, then the section of the valve must be greatly overdimensioned, such that the valve is generally impossible to incorporate in a turbine engine.

SUMMARY OF THE INVENTION

The object of the invention is to provide another solution to the above-mentioned problem, making it possible to satisfy both of the above requirements (high pressure for opening the bleed valves, and low temperature for the air fed to the solenoid valves that control the bleed valves).
To this end, the invention provides a system for controlling a pneumatic valve in a turbine engine, such as a bleed valve, the system comprising a controlling solenoid valve and means for feeding fluid at a pressure P2, the system being characterized in that it also includes a directional control valve for fluid at a pressure P1 that is connected to the bleed valve, to the solenoid valve, and to means for taking off air at the pressure P1 from the turbine engine in order to control the above-mentioned bleed valve, opening and closing of the bleed valve being controlled by the air at the pressure P1 delivered by the directional control valve that is itself controlled by a flow of fluid at the pressure P2 delivered by the solenoid valve, the pressure P1 being independent of the pressure P2.
In the system of the invention, the directional control valve (such as a distributor) mounted between the solenoid valve and the pneumatic valve that is to be controlled connects said pneumatic valve either to the means for taking off air at the pressure P1 in order to cause it to be opened, or else to the exhaust in order to cause it to be closed, while it is itself controlled by a fluid that is supplied by the solenoid valve at a pressure that is independent of the control pressure for the pneumatic valve and that can therefore be lower than said control pressure, so the fluid may consequently have a temperature that is acceptable for the solenoid valve, e.g. not exceeding 200° C., when the fluid is air taken from a stage of the compressor.
In the present application, the term “independent” is used of pressures to designate pressures of fluid coming from sources that are different and/or that have different values. These fluids may for example be taken from different stages of the same compressor of the turbine engine; the fluids then have pressures that are different, the pressure of the fluid taken from the stage that is further downstream being greater than the pressure of the fluid taken from the stage that is further upstream.
The system for controlling the pneumatic valve may thus be considered as a two-stage system, comprising a high-pressure stage including the directional control valve and a low-pressure stage including the solenoid valve (which stage is also a low temperature stage).
The directional control valve may be controlled pneumatically or hydraulically, i.e. the solenoid valve may control it with a flow of air or with a flow of liquid. By way of example, the solenoid valve obtains its control fluid by being connected to a fuel circuit or to means for taking off air from the turbine engine.
Advantageously, the directional control valve is of the type having three fluid inlet/outlet ports connected respectively to the valve that is to be controlled, to the solenoid valve, and to the ambient atmosphere, and it includes a movable member that is movable between two positions in which the valve that is to be controlled is connected respectively either to means for taking off air at the pressure P1 or to the ambient atmosphere, with the movement of the movable member being controlled by the fluid under pressure delivered by the solenoid valve.
The take-off means connected to the directional control valve may take air from the compressor of the turbine engine from a zone that is situated substantially in register with the bleed valve or else downstream from the bleed valve, relative to the flow direction of gas through the turbine engine. When this air is taken off downstream from the valve that is to be controlled, the taken-off air is at a pressure higher than the bleed pressure of the bleed valve, and when the air is taken off level with the bleed valve, the taken-off air is at a pressure that is substantially identical to the bleed pressure of the bleed valve. Under such circumstances, the bleed valve may include an additional chamber so as to be able to have a section against which the control pressure acts in order to open the valve that is greater than the section against which the pressure acts in order to close the valve. A valve of this type is described in document U.S. Pat. No. 6,981,842.
The solenoid valve may have two inlets for connecting respectively to a source of fluid under pressure and to the ambient atmosphere, and one outlet connected to a port of the directional control valve.
Advantageously, one inlet of the solenoid valve is for connecting to means for taking off air at a pressure P2 from the turbine engine, the pressure P2 being less than the pressure P1. The solenoid valve is thus connected to means for taking off air from the compressor of the turbine engine in a zone that is situated upstream from the zone from which air is taken off at the pressure P1 for feeding to the directional control valve, “downstream” being relative to the flow direction of air through the turbine engine. The solenoid valve is thus fed with air at a pressure and at a temperature that are lower than the temperature and pressure of the air that is taken off to feed the directional control valve that controls the bleed valve, and the directional control valve is itself controlled by a fluid at low pressure coming from the solenoid valve in order to switch between the high pressure required for operating the pneumatic valve, and ambient pressure.
By way of example, the solenoid valve has two chambers, one of which is for feeding a port of the directional control valve with fluid under pressure, and the other of which is for connecting said port to the ambient atmosphere. In a variant, the solenoid valve may be of the two-stage type having a first stage for feeding a port of the directional control valve with fluid under pressure or with the ambient atmosphere, and a second stage for controlling the switching of the first stage.
The present invention also provides a turbine engine, such as an airplane turboprop or turbojet, having an engine surrounded by a nacelle and including at least one pneumatic valve, such as a bleed valve, the turbine engine being characterized in that the or each pneumatic valve is controlled by a system as described above.
The turbine engine may have two or even more bleed valves, each bleed valve being controlled by a system of the above-described type.
The directional control valve of the system of the invention may be situated in the engine, close to the pneumatic valve that is to be controlled, or in the nacelle, close to the solenoid valve for controlling the directional control valve. Placing the directional control valve closer to the solenoid valve (in the nacelle) makes it possible to minimize the volume of the pipe connecting those two pieces of equipment together. Under such circumstances, it is possible to use a simple solenoid valve that has no impact on the configuration of the pneumatic valve. When the directional control valve is placed close to the pneumatic valve, it is preferably incorporated in the casing of that valve so as to reduce the weight of the system. It is then possible to use a simple solenoid valve or on the contrary a two-stage solenoid valve if the flow rate required for filling the pipework leading to the directional control valve is too great.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood and other details, advantages, and characteristics of the invention appear on reading the following description made by way of non-limiting example and with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of a prior art system for controlling turbine engine bleed valves;

FIG. 2 is a diagram showing a system for controlling a turbine engine bleed valve in accordance with the invention;

FIGS. 3 and 4 are diagrams showing the directional control valve and the solenoid valve of the FIG. 2 system, showing respectively the closed and open positions of those valves; and

FIG. 5 is a diagram of a variant embodiment of the control system of the invention.

MORE DETAILED DESCRIPTION

Reference is made initially to FIG. 1 which shows a prior art system 10 for controlling bleed valves in a bypass turbine engine.
In the example shown, the turbine engine has two bleed valves 12 and 14 (specifically “handling” bleed valves HBV1 and HBV2) that are controlled by a common system 10 that also controls an air take-off valve 16 for controlling clearance in the engine by using a high-pressure turbine active clearance control (HPTACC) system.
In known manner, the bleed valves 12 and 14 are mounted in the high-pressure compressor of the turbine engine and they enable air from the primary stream (at a pressure P0) flowing through that compressor to be bled off towards the secondary stream F2.
The bleed and take-off valves 12, 14 and 16 in this example are pneumatically controlled, and they are designed to occupy a closed position in normal operation mode. The bleed valves 12 and 14 need to be fed with air at a pressure P1 higher than the bleed pressure P0 for causing them to open. They are closed by connecting the pressurized air feed of the valves to ambient pressure.
Typically, each bleed valve 12, 14 may include a chamber that, when fed with air at a pressure P1, causes a movable member such as a piston to move from a valve-closed position to a valve-open position, in which air at the pressure P0 of the compressor is bled off into the secondary stream.
The valves 12, 14, and 16 are controlled by respective solenoid valves 18, 20, and 22, all of which are mounted in a common pneumatic control unit (PCU) 24.
The valves 12, 14, and 16 are located in the engine proper 26 of the turbine engine 18, and the solenoid valves 18, 20, and 22 are situated in the nacelle 28 of the turbine engine, where ambient temperature is lower than in the engine proper.
Each solenoid valve 18, 20 has a first inlet 32 connected to means 30 for taking air at the pressure P1 from the compressor of the turbine engine, a second inlet 34 connected to the ambient atmosphere Pamb, and an outlet 36 connected to an inlet 38 of the corresponding valve 12 or 14, and in particular to the inlet of the above-mentioned chamber of that valve.
The PCU 24 includes electrical control means for the solenoid valves 18 and 20, which means are suitable for applying a first signal to a solenoid valve in order to cause it to open, i.e. connect its first inlet 32 fed with air at pressure P1 to its outlet 36 connected to the corresponding bleed valve 12 or 14, and a second signal for causing the solenoid valve to close, i.e. to connect its second inlet 34 that is connected to the ambient atmosphere Pamb with its outlet 36 connected to the corresponding bleed valve.
As mentioned above, the valves 12 and 14 open when the solenoid valves 18 and 20 are open and fed with air at a pressure P1 (higher than the bleed pressure P0). Bleed air then passes through the valves from the primary stream through the compressor into the secondary stream F2 through the turbine engine. The valves 12 and 14 close when the solenoid valves are closed and connected to the ambient atmosphere Pamb via the solenoid valves.
This prior art control system 10 presents a major drawback associated with the fact that the solenoid valves 18 and 20 are fed with air at high pressure that is taken from the compressor and that is therefore at a high temperature. That technology is therefore not applicable to solenoid valves capable of withstanding only relatively low temperatures, e.g. not exceeding 200° C.
The present invention makes it possible to remedy that drawback by providing a bleed valve control system that is of the two-stage type, comprising a high-pressure first stage for controlling the bleed valves and a second stage at low pressure and at low temperature for controlling the first stage. The first stage comprises a directional control valve for air under pressure and the second stage comprises a solenoid valve that may be fed with fluid at a low pressure and at a temperature that is relatively low, e.g. no more than 200° C.
In the embodiment of the invention shown in FIGS. 2 to 4, the control system 110 has only one bleed valve HBV 112 that is mounted in the engine proper 126 of the turbine engine. This valve 112 is similar to the valves 12 and 14 of FIG. 1.
In the example shown, the two stages of the control system 110 are situated in the nacelle 128 of the turbine engine.
The directional control valve 140 forming the first stage of the control system is of the “3/2” type, i.e. it has three ports and two positions. The directional control valve 140 has an inlet 142 connected to means 144 for taking air at the pressure P1 from the high-pressure compressor of the turbine engine, an outlet 146 leading to the ambient atmosphere Pamb, a control inlet 148 connected to the outlet 136 of the solenoid valve 118, and an outlet 150 connected to the inlet 138 of the bleed valve 112, i.e. to the inlet of the valve chamber of the above-specified type.
The inlet 148 of the directional control valve 140 is connected to the outlet 136 of the solenoid valve 118 by a pipe 92 that is relatively short so that the solenoid valve and the directional control valve are as close together as possible (while still complying with temperature constraints) in order to minimize the internal volume of the pipe 92.
The directional control valve 140 may occupy two states, an open state in which the inlet 142 that is connected to the means for taking off air at the pressure P1 is connected via the outlet 150 to the bleed valve 112, and a closed state in which the inlet 146 leading to the ambient atmosphere is connected via the outlet 150 to the bleed valve 112.
The directional control valve 140 is shown diagrammatically on a larger scale in FIGS. 3 and 4. It comprises a member 160, such as a piston, that is mounted in leaktight manner in a cylindrical bore of a valve body. By way of example, the member 160 comprises two parallel disks 162 that are fastened to opposite ends of a longitudinal rod that keeps them spaced apart from each other.
The member 160 defines three chambers in the body of the valve 140. A first chamber 164 is defined between one of the disks 162 and an end wall of the body, this chamber communicating with the inlet 148 that is connected to the outlet 136 of the solenoid valve 118. A second chamber 166 is defined between the disks 162, this chamber communicating with the inlet 142 that is connected to the means for taking off air at the pressure P1 and capable of communicating with the outlet 150 of the directional control valve when it is in the above-mentioned open state. A third chamber 168 is defined between the other disk 162 and the other end wall of the body, this chamber communicating with the inlet 146 that is connected to the source of air at ambient pressure and being capable of communicating with the outlet 150 of the directional control valve when it is in the above-mentioned closed state.
Resilient return means 170, such as a compression spring, are mounted in the third chamber 168 and urge the member 160 into the closed position (shown in FIG. 3) of the directional control valve. The return force of this spring is less than the force exerted by air at pressure P2 on the member 160 when the directional control valve is fed by the solenoid valve 118.
The solenoid valve 118 that forms the second stage of the control system 110 has two inlets and one outlet. Its two inlets comprise respectively an inlet 132 connected to means 130 for taking off air at pressure P2 from the high-pressure compressor of the turbine engine, and an inlet 134 connected to a source of air at ambient pressure Pamb. The outlet 136 of the solenoid valve 118 is connected to the inlet 148 of the valve 140.
The pressure P2 is less than the pressure P1, and air at the pressure P2 is at a temperature that is acceptable for the solenoid valve, e.g. no more than 200° C. The means 130 for taking off air at the pressure P2 are situated upstream from the means for taking off air at the pressure P1 in the compressor and relative to the flow direction of air through the compressor.
The solenoid valve 118 is shown diagrammatically at a larger scale in FIGS. 3 and 4. It is of the simple or one-stage type and has two chambers 174 and 172 into which the above-mentioned inlets 130 and 134 lead respectively. The chambers 172 and 174 communicate with each other via a connection port 176, and the outlet 136 of the solenoid valve communicates with the chamber 174.
The solenoid valve 118 has a member 180 that is movable between an open position (shown in FIG. 4) in which the inlet 130 connected to the means for taking off air at the pressure P2 is connected to the outlet 136, and a closed position (shown in FIG. 3) in which the inlet 134 connected to the ambient atmosphere is connected to the outlet 136.
In this example, the member 180 is elongate in shape and has one end carrying a valve member for closing either the connection port 176 between the chambers 172 and 174, or else the inlet port 130 of the chamber 174. The opposite end of the member 180 carries a permanent magnet that is engaged in a cylindrical coil 182 that is connected to a computer of the electronic engine controller (EEC) type and to electrical power supply means.
When the coil 182 is powered, it generates a magnetic field causing the member 180 to move into its position shown in FIG. 3 for closing the solenoid valve 118, in which the valve member carried by the movable member closes the inlet port 130 of the chamber 174. The inlet 134 of the first chamber 172 then communicates with the outlet 136 of the second chamber via the connection port 176. The first chamber 164 of the valve 140 is then connected by the solenoid valve 118 to the ambient atmosphere. The return means 170 that exert a force on the movable member 160 greater the force exerted by air at ambient pressure urge the movable member into the closed position of FIG. 3, such that the bleed valve 112 is connected by the third chamber 168 of the directional control valve to the ambient atmosphere.
When the coil 182 of the solenoid valve 118 is not electrically powered, the movable member 180 is in its position shown in FIG. 4 for opening the solenoid valve 118, in which position the valve member carried by the movable member closes the port for connecting together the chambers 172 and 174. The inlet 130 of the chamber 174 then communicates with the outlet 136 of said chamber. The first chamber 164 of the valve 140 is then connected via the solenoid valve 118 to the means for taking off air at the pressure P2, thereby causing the movable member 160 of the directional control valve to move in the open position shown in FIG. 4, in which the bleed valve 112 is connected by the second chamber 166 of the valve 140 to the means for taking off air at the pressure P1.
In normal operation mode, the coil 182 of the solenoid valve 118 is powered electrically so that it is in its closed position as shown in FIG. 3. The valve 140 is in its closed position and it connects the bleed valve 112 to the source of air at ambient pressure. The bleed valve 112 thus remains closed.
When the valve 112 is to be opened in order to bleed air at the pressure P0 into the secondary stream, the electrical power supply to the coil 182 of the solenoid valve 118 is interrupted by the above-mentioned EEC type means, and the solenoid valve occupies its open position as shown in FIG. 4. The chamber 164 of the directional control valve is fed with air at the pressure P2, thereby causing the movable member 160 to move from its position shown in FIG. 3 to its position shown in FIG. 4. The directional control valve thus adopts an open position and connects the bleed valve 112 to the means for taking off air at the pressure P1, thereby causing the bleed valve to open. When electrical power to the coil 182 is reestablished, the solenoid valve 118 closes (FIG. 3), the chamber 164 of the directional control valve is connected to the ambient atmosphere, and the member 160 is urged by the means 170 to return to its position shown in FIG. 3. The bleed valve 112 is thus connected via the chamber 168 of the directional control valve to the ambient atmosphere, thereby closing the valve 112.
In a variant, the chambers 172 and 174 of the solenoid valve 118 may be connected to sources of fluid other than air. For example, they may be connected to a fuel circuit of the turbine engine. The valve 140 is then hydraulically controlled, the first chamber 164 being designed to be fed with fuel.
FIG. 5 shows a variant embodiment of the control system 110′ of the invention in which the valve 140 is mounted in the engine proper 126 of the turbine engine, and is no longer beside the solenoid valve 118 in the nacelle 182 of the turbine engine. The valve 140 may be mounted inside the casing 190 of the bleed valve 112.
The valve 140 is similar to FIGS. 2 and 4 and its inlet 148 is connected to the outlet 136 of the solenoid valve 118 via a pipe 192 that is longer than the pipe 92 of FIGS. 2 to 4.
The solenoid valve 118 may be similar to that of FIGS. 2 to 4. In a variant, and as shown in FIG. 5, it may be of the two-stage type. When the pipe 192 connecting the valve 140 to the solenoid valve 118 is long, its internal volume may be large, which may require the solenoid valve to deliver fluid at a high filling rate. Because of significant head losses in a simple solenoid valve of the type shown in FIGS. 2 to 4, a valve of that type may not be sufficient to deliver the desired flow rate. It is therefore preferable under such circumstances to use a two-stage solenoid valve, i.e. a solenoid valve having one stage for feeding the chamber 164 of the valve 140 with the pressure P2 or for connecting it to ambient pressure, and another stage for controlling the switching of the first stage.
The operation of the control system shown in FIG. 5 is similar to that of the control system shown in FIGS. 2 to 4.
In the above-described systems, the pressure P1 for controlling the bleed valve 112 is higher than the bleed pressure P0 of that valve, i.e. the means for taking off air at the pressure P1 are situated in the compressor downstream from the bleed valve.
In a variant, the control pressure P1 for the bleed valve may be equal to the bleed pressure P0 of that valve, i.e. the means for taking off air at the pressure P1 are situated in the compressor level with or in register with the bleed valve, i.e. substantially in the same transverse plane as that valve.
Under such circumstances, the pipe used for conveying air under pressure from the directional control valve to the bleed valve may be shorter. Furthermore, the bleed valve 112 then includes an additional chamber of the type described in document U.S. Pat. No. 6,981,842.
In yet another variant (not shown), the turbine engine may be fitted with two or more bleed valves that may be controlled independently of one another by distinct control systems, or that may be controlled simultaneously by a common control system having one or more directional control valves and one or more solenoid valves.
The system of the invention may be used for controlling valves other than bleed valves.

Claims

1. A system for controlling a pneumatic valve in a turbine engine, comprising a controlling solenoid valve and means for feeding fluid at a pressure P2, wherein the system further includes a directional control valve for fluid at a pressure P1 that is connected to the bleed valve, to the solenoid valve, and to means for taking off air at the pressure P1 from the turbine engine in order to control said bleed valve, opening and closing of the bleed valve being controlled by the air at the pressure P1 delivered by the directional control valve that is itself controlled by a flow of fluid at the pressure P2 delivered by the solenoid valve, the pressure P1 being independent of the pressure P2.

2. A system according to claim 1, wherein the directional control valve is pneumatically or hydraulically controlled by the solenoid valve.

3. A system according to claim 1, wherein the solenoid valve is connected to a fuel circuit or to means for taking off air from the turbine engine for the purpose of delivering its control action.

4. A system according to claim 1, wherein the solenoid valve is of the type having three fluid inlet/outlet ports connected respectively to the bleed valve that is to be controlled, to the solenoid valve, and to the ambient atmosphere, and includes a movable member that is movable between two positions in which the bleed valve that is to be controlled is connected respectively to the means for taking off air at the pressure P1, and to the ambient atmosphere, with the movement of the movable member being controlled by the fluid under pressure delivered by the solenoid valve.

5. A system according to claim 1, wherein the solenoid valve has two inlets for connecting respectively to a source of fluid under pressure and to the ambient atmosphere, and an outlet connected to a port of the directional control valve.

6. A system according to claim 1, wherein an inlet of the solenoid valve is for connecting to means for taking off air at a pressure P2 from the turbine engine, the pressure P2 being less than the pressure P1.

7. A system according to claim 1, wherein the solenoid valve has two chambers, one of which is for feeding a port of the directional control valve with fluid under pressure, and the other of which is for connecting said port to the ambient atmosphere.

8. A turbine engine, comprising an engine surrounded by a nacelle and including at least one pneumatic valve, wherein said at least one pneumatic valve is controlled by a system according to claim 1.

9. A turbine engine according to claim 8, wherein the directional control valve is situated in the engine close to the bleed valve or in the nacelle close to the solenoid valve.