GB2450515A - Turbine engine fuel supply system - Google Patents

Abstract

A turbine engine fuel supply system includes a plurality of fuel nozzles 10 and valves 100, a fuel manifold 24, and an actuator 26 which controls the operation of the valves 100. The actuator 26 is operatively connected to the valves 100 by a mechanical linkage 200, which may be a unison ring. Where the mechanical linkage (200) includes a unison ring, the mechanical linkage 200 preferably further includes a plurality of sub-linkages, each sub-linkage connecting the unison ring to a respective valve 100. The system may be used for the synchronous control of groups or sub-groups of burners nozzles in a turbine engine.

Description

FUEL SUPPLY SYSTEM

The present invention relates to a fuel supply system suitable for a turbine engine, in particular a multi-stage combustor of a gas turbine engine.

There are a number of known fuel supply systems for staged gas turbine combustion systems. For example, US7,036,302 discloses a multi-stage gas turbine engine fuel supply system including a plurality of fuel injectors and at least first and second stage fuel injection circuits in each of the fuel injectors. Each of the first and second stage fuel injection circuits has first and second fuel injection points and at least first and second fuel nozzle valves controllably connected to the first and second staged fuel injection circuits, respectively.

A fuel supply circuit includes a single fuel supply manifold connected in fuel supplying relationship to all of the fuel nozzle valves. The first and second fuel nozzle valves are operable to open at different first and second crack open pressures, respectively, and all of the first and second fuel nozzle valves are controllably connected to a single fuel signal manifold in a signal circuit. The signal circuit includes a signal fuel return line leading from the fuel signal manifold to a signal fuel return inlet to a fuel pump.

The system further includes a pressure difference measuring means for sensing a pressure difference between a signal pressure of the signal circuit and a fuel supply pressure of the fuel supply circuit.

A fuel controller in feedback signal relationship to the pressure difference measuring means controls a pressure regulator controllably connected to a fuel controller.

The fuel controller, by controlling the pressure regulator, controls and regulates pressure through the signal circuit and, thus, controls the crack open pressures sent to the fuel nozzle valves from the single fuel signal manifold in the signal circuit.

The first fuel nozzle valves open and remain open when the pressure in the signal circuit equals or exceeds the first crack open pressure. The second fuel nozzle valves open and remain open when the pressure in the signal circuit equals or exceeds the second crack open pressure.

This allegedly eliminates the need for multiple fuel and signal lines to each injector for each stage.

As can be seen, US7,D36,302 relies on sophisticated valve technology to achieve the staging control. Examples of the valves are shown in Figs. 13 to 16 of US7,036,302.

Similar valves are disclosed in tJS6,955,040. However, the valves are located close to the hostile environment of the burner of the gas turbine. As a consequence, such valves may be prone to failure, or at least will be subject to frequent maintenance checks to ensure safe and effective operation is maintained in view of their relative sophistication.

Another similar valve is also disclosed in tJS5,442,922, where the nozzle shut-off valves are controllable via a separate signal pressure line.

For instance, it is disclosed that each shut-off valve includes a spring-biased valve member, located between an inlet port and an outlet port, which is normally biased in the open position. The backside of each shut-off valve is coupled to a branch of the signal pressure line to receive high pressure fuel, and in turn drive the respective valve member into a closed position.

US5,442,922 discloses that such valves are included in a fuel staging system in which metered fuel from a fuel metering unit is directed into a fuel inlet line coupled to a sequence valve. The signal pressure line is also supplied by the sequence valve.

A main fuel manifold is coupled downstream of the sequence valve, and a plurality of main fuel nozzles are each coupled to the main fuel manifold through a respective main nozzle shut-off valve.

A first set of pilot nozzles is coupled to the main fuel manifold through the sequence valve, and a second set of pilot nozzles is also coupled to the main fuel manifold through the sequence valve.

At low engine speeds, in the first and/or second pilot open positions, fuel flows to either pilot nozzle through the main fuel manifold, and the main fuel nozzles are isolated from the main fuel manifold by the main nozzle shut-off valves.

Then, at higher engine speeds, the main nozzle shut-off valves are opened, and the sequence valve splits the fuel flow from the fuel inlet line between the main fuel manifold and the first and second pilot nozzles. The fuel in the main fuel manifold flows to the main fuel nozzles, and the remainder of the fuel split off by the sequence valve flows to the first and second pilot nozzles.

Again, the nozzle shut-off valves are likely to be positioned close to the hostile burner environment, and therefore are likely to suffer from similar problems to that outlined above in respect of the valves of US7, 036,302.

Therefore, in general, an aim of the present invention is to provide a fuel supply system suitable for a turbine engine, e.g. a gas turbine engine, which overcomes the problems set forth.

In a first aspect, a turbine fuel supply system according to the present invention, e.g. a gas turbine fuel supply system, may include a plurality of first fuel nozzles for injecting fuel into a combustor of a turbine engine, a plurality of valves operable to communicate fuel to respective of the first fuel nozzles, a fuel manifold for communicating fuel to the valves from a fuel source, and an actuator which controls the operation of the valves, the actuator being operatively connected to the valves by a mechanical linkage.

Preferably, the valves are nozzle shut-off valves which control the flow of fuel, from the fuel manifold, to the combustor of the turbine engine. The valves may be adapted for mounting to a casing of the combustor.

The actuator and mechanical linkage may be configured to operate the valves of one or more groupings of valves in unison.

The actuator may be situated in a region of the turbine engine which is cooler, during operation of the engine, than the casing of the combustor. For example, the actuator may be situated in a region of the engine between the casing of the combustor and a fancase of the turbine engine incorporating the combustor.

The actuator and mechanical linkage may be configured to allow fuel flow to the first fuel nozzles to be altered.

For example, the actuator and mechanical linkage may be configured to allow fuel flow to the first fuel nozzles to be opened or shut off. Theactuator and mechanical linkage may be configured to allow variation in the extent of fuel flow to the first fuel nozzles, e.g. by varying the extent to which the valves are open, or shut.

The actuator and mechanical linkage may be configured to allow fuel flow to one or more predetermined groupings of the first fuel nozzles to be opened while the other of the first fuel nozzles are shut off. For example, the actuator and mechanical linkage may be configured to allow fuel flow to a grouping of mains 1 nozzles to be opened, although a grouping of mains 2 nozzles are shut off.

The actuator and mechanical linkage may be configured to allow all the respective valves (e.g. of one or more particular groupings of valves) to communicate fuel to the combustor at a similar, or at substantially the same, rate of flow -for example, all the respective valves (e.g. of one or more particular groupings) may be opened, or shut off, to a similar extent.

The actuator and mechanical linkage may be at opposing sides of a fireproof seal. An operating member may operatively connect the actuator and mechanical linkage via the fireproof seal.

The actuator may be situated in a region of the engine, which is relatively cool during operation of the engine, whereas the mechanical linkage may be situated in a region of the engine which is relatively hot during operation of the engine, e.g. relatively closer to the combustor than the actuator.

The mechanical linkage may include a unison ring, which provides the actuator with operative control of each of the valves of one or more groupings of the valves. Such valves may be operable in unison. The unison ring may allow simultaneous control of the valves, e.g. in one or more groupings of the valves, to which it is connected.

The unison ring may be adapted for mounting to a casing of the combustor. The actuator and unison ring may be at opposing sides of the fireproof seal.

Where the mechanical linkage includes a unison ring, the mechanical linkage preferably further includes a plurality of sub-linkages, each sub-linkage connecting the unison ring to a respective valve. Movement of the unison ring preferably results in a corresponding movement of each sub-linkage. Movement of a sub-linkage preferably alters the extent to which the respective valve is opened, or shut off.

The combustor may be a multi-stage combustor (e.g. it may be a combustor of a multi-stage turbine engine, and thus referred to as a multi-stage combustor) and the first fuel nozzles may be mains fuel nozzles, the system further having a plurality of pilot fuel nozzles for injecting fuel into the combustor.

To provide some control over the staging of the system, the system may further have means for varying the amount of fuel communicated to the mains fuel nozzles relative to the amount of fuel communicated to the pilot fuel nozzles.

For example, the actuator and mechanical linkage may be configured to allow the amount of fuel communicated to the mains fuel nozzles to be varied relative to the amount of fuel communicated to the pilot fuel nozzles.

The means for varying the amount of fuel may additionally, or alternatively, include a splitter valve, up stream of and in communication with the fuel manifold, for controlling the relative split of fuel flow between the mains fuel nozzles and the pilot nozzles.

It is desirable to avoid fuel stagnating in the fuel passages, e.g. the fuel manifold. Fuel subject to heat soakage from high temperatures, e.g. at the core of the engine, can degrade. This can result in coking, which can form deposits in the fuel passages, thereby causing blockages in the system and hence loss of function.

Therefore, a fuel supply system according to the present invention may include a recirculating conduit in fluid communication with the fuel manifold and the fuel source, the recirculating conduit allowing fuel not communicated to the combustor by the valves of one or more groupings of the valves to be returned to the fuel source.

Thus, in all operating modes fuel may be able to flow in the fuel manifold, regardless of whether the valves are open or closed. This can also allow for rapid transitions between each staging mode of the turbine.

A measurement assembly for determining the rate of flow of fuel into the, or each, fuel manifold may be provided.

The measurement assembly may include a hydromechanical unit (HMU) and/or a flowmeter. A fuel metering assembly for determining the rate of flow of fuel in the recirculating conduit may be provided. -Aspects and embodiments of the present invention will now be illustrated, by way of example, with reference to the accompanying figures in which: Fig. 1 shows a fuel supply system according to the present invention; and Fig. 2 shows an alternative fuel supply system according to the present invention.

Further aspects and embodiments will be apparent to those skilled in the art.

A fuel supply system 1 according to the present invention is illustrated in Fig. 1, in which the fuel supply system provides a plurality of mains fuel supply nozzles (mains FSNs) 10 (which may be grouped into one or more respective groupings of valves, such as mains 1 and mains 2 groupings) and one or more pilot fuel supply nozzles (pilot FSNs) 12 for a multi-stage turbine engine.

It is possible to operate such a multi-stage engine in a -variety of modes. Generally, such modes include: a pilot only mode, in which the pilot nozzles 12 inject fuel into the combustor, but the mains nozzles 10 do not inject fuel into the combustor; a mains 1 mode, in which a grouping of mains 1 nozzles and the pilot nozzles inject fuel into the combustor, but other mains nozzle groupings do not inject fuel into the combustor; and, mains 2 mode, in which groupings of both mains 2 and mains 1 nozzles and the pilot nozzles all inject fuel into the combustor.

However, variations on these modes are possible, and whilst the present invention is described in relation to such modes by way of example, it should not be considered to be limited to operating only in such modes.

Fuel is communicable to a high pressure (HP) pump 16 via a fuel flowmeter 14. The fuel flowmeter 14 is capable of determining the rate of flow of fuel communicated to the HP pump 16. The HP pump 16 is capable of pressurizing the fuel to a suitably high pressure e.g. for injection into a combustor of a (gas) turbine engine via the mains and/or pilot nozzles 10, 12. The HP pump 16 may be a device capable of varying the pressure of the pumped fuel. For example, the HP pump 16 may be controllable to pump fuel at a higher pressure when one or more groupings of the mains nozzles 10 are staged-in than when the system is in pilot mode only.

A hydromechanical unit (HMU) 18 may be in fluid communication with the HP pump 16. The HMU 18 may be used to determine the rate of flow of fuel through it.

In the present embodiment, the HMtJ 18 is arranged to measure the rate of fuel which is supplied to the (or each) fuel manifold 22, 24.

Fuel is communicated from the HMU 18 to a splitter valve 20, and thereafter to the pilot fuel manifold 22 and the mains fuel manifold 24. Fuel is able to be communicated to the or each pilot nozzle 12 from the pilot fuel manifold 22.

The splitter valve 20 is preferably adapted to allow the amount of fuel communicated to the mains fuel manifold 24 to be varied relative to the amount of fuel communicated to the pilot fuel manifold 22. Therefore, under certain conditions, the splitter valve 20 is adapted to allow the amount of fuel communicated to the mains fuel nozzles 10 to be varied relative to the amount of fuel communicated to the pilot fuel nozzles 12. Throughout the operation of the system, the amount of fuel communicated to the mains nozzles 10 and the pilot nozzles 12 may be varied to optimise the combustion efficiency (e.g. by controlling the combustion temperatures), preferably whilst avoiding potentially destructive thermoacoustic instability.

Each valve 100 controls the flow of fuel from the mains fuel manifold 24 to a respective mains nozzle 10. The valves can be operated over a range of settings between fully open and shut-off, thereby providing control of the fuel flow rate into the combustor via mains nozzles 10.

The range of operational settings for each valve may be a range of discrete operating positions, each position allowing a predetermined flow of fuel to be communicated to the respective nozzle for a given fuel pressure. This can provide flexibility in the staging strategy and in the operation of a system 1 according to the present invention.

When the valves 100 are shut-off, no fuel can flow through them to the mains nozzles 10. Thus, to avoid fuel stagnating e.g. in the mains fuel manifold 24, a recirculating conduit 28 is provided. The recirculating conduit 28 allows fuel not communicated to the mains nozzles 10 to be recirculated to the fuel source, e.g. to a region upstream of the HP pump 16. Preferably, the recirculated fuel is recirculated via a flow regulating valve 29, which may be capable of determining the recirculated fuel flow. A preferred recirculating fuel flow is approximately 400pph in all modes of operation.

The flow regulating valve may allow the recirculating flow to be altered e.g. by providing a variable flow restriction. The variable flow restriction may allow the fuel flow to be maintained at the desired rate.

The recirculated fuel may be communicated via a surface air cooler 34 to cool it down. The surface air cooler 34 may form a portion of the recirculating conduit 28.

Provision of the recirculating conduit 28 allows for rapid transitions between each staging mode with little or no adverse effect on engine operability. Furthermore, as a safety consideration, maintaining pressurized fuel in an un-staged fuel manifold can help to prevent air ingress into the system.

The operation of the mains valves 100 is controlled by a fuel staging actuator 26. The actuator 26 is preferably a servo powered actuator. The actuator 26 is operatively connected to the valves 100 by a mechanical linkage 200.

The mechanical linkage 200 may be arranged substantially circumferentially around the engine, e.g. the combustor of the engine. The mechanical linkage 200 may be adapted to transmit an actuation force from the actuator to the valves 100 in order to operate them.

The mechanical linkage 200 may include sub-linkages (not shown) respectively operatively connected to the valves 100. Operation of the mechanical linkage 200 by the actuator 26 allows operation of each of the valves 100 operatively connected to the mechanical linkage 200.

The mechanical linkage 200 preferably includes a unison ring (not shown) . Preferably, the unison ring is adapted for mounting to the casing of the combustor.

The skilled person knows how to make a unison ring which can operate close to the combustor. US4,720,237, the contents of which are incorporated herein by reference, discloses an example of a unison ring actuator assembly.

Another unison ring type assembly is disclosed in tJS4,497,170, the contents of which are also incorporated herein by reference.

According to the present invention, a unison ring is adapted to operate one or more groupings of the valves 100 to which it is operatively connected, under the action of the actuator 26. The unison ring 200 may allow all such valves 100 to be operated in unison.

The unison ring allows each of the valves 100 operatively connected to it to be controlled in the same way. Each valve 100 operatively connected to the unison ring can be opened or shut-off to the same extent as all the other valves 100 operatively connected to it.

This is particularly advantageous for controlling the valves 100, which are situated in a high temperature environment near to the combustor of a turbine engine, leading to a steep temperature gradient between the valves 100 and the actuator 26.

The configuration of the actuator 26 may be representative of the operational setting of the valves 100. However, thermal fluctuations in environment of the mechanical linkage may result in, for example, a thermal expansion or contraction of the mechanical linkage 200 and therefore produce an unwanted change in the operational setting of each of the valves 100 operatively connected to the mechanical linkage 200 (i.e. the operational setting of such valves may not correspond to the configuration of the actuator 26) Indeed, a unison ring 200 according to the present invention is preferably operatively connected to the actuator 26 by an operating assembly 210, preferably through a fireproof seal 30. However, the operating assembly 210 may be influenced by fluctuations in the temperature gradient between the actuator 26 and the unison ring 200, which may change the arrangement of the unison ring 200 relative to the valves 100 and therefore result in an unwanted change in the operational setting of the valves 100 operatively connected to the unison ring 200 (i.e. the operational setting of such valves may not correspond to the configuration of the actuator 26) Thermal fluctuations leading to changes in configuration of the mechanical linkage, of the operating assembly and/or of the actuator can be accounted for by providing the mechanical linkage, the operating assembly and/or the actuator with one or more spacers as described in US200610013683, the contents of which are incorporated herein by reference.

The mechanical linkage 200 may be arranged such that: a first movement opens a first grouping of the valves operatively connected to the mechanical linkage (e.g. a grouping of mains 1 valves); a second movement opens a second grouping of the valves operatively connected to the mechanical linkage (e.g. a grouping of mains 2 valves); and a third movement opens all the valves operatively connected to the mechanical linkage. A fourth movement may result in shut-off of all the valves operatively connected to the mechanical linkage. The second movement may close the first grouping of the valves (e.g. a grouping of mains 1 valves) . The first to fourth movements described above may be sequential, although this is not necessary. A respective unison ring may be provided for each valve grouping of a plurality of groupings of valves.

An EEC (electronic engine controller) 32 may be provided to control the fuel supply system. The actuator 26 may be under the control of the EEC 32, e.g. via an electrical harness 36. The EEC 32 may be in communication, e.g. via an electrical harness 36, with the flowmeter 14, the HMU 18 and/or the flow regulating valve 29. The EEC may register the fuel flow rate determined by the flowmeter 14, by the flow regulating valve 29 and/or by the HMU 18.

On the basis of one or more of these determinations, in particular the determination of the flow regulating valve 29, the EEC may control the operation of the splitter valve 20 to vary the amount of fuel communicated to the mains fuel nozzles 10 relative to the amount of fuel communicated to the pilot fuel nozzles 12. In other words, the determined recirculation flow can be accounted for in the positioning of the splitter valve.

On the basis of one or more of the determinations, in particular the determination of the flow regulating valve 29, the EEC may configure the actuator 26 and mechanical linkage 200 to vary the amount of fuel communicated to the mains fuel nozzles 10 relative to the amount of fuel communicated to the pilot fuel nozzles 12.

An alternative arrangement of a fuel supply system according to the present invention is shown in Fig. 2.

The alternative arrangement differs from the arrangement shown in Fig. 1. in that the valves 101 are operated to control the staging of the system, without the additional control which can be provided by the splitter valve 20 of Fig. 1.

The valves 101 may be operated in groupings such that one or more groupings of the valves 101 allow fuel flow to a grouping of pilot nozzles only, whilst one or more further groupings of the valves may allow fuel to flow to a grouping of mains nozzles. Operation of the mechanical linkage, such as a unison ring, may allow the respective groupings to be operated in unison or respectively independently.

An acceptably accurate flow split ratio allowing staging control between mains and pilot stages can be achieved with eight discrete valve positions. Control of the pilot and mains staging modes is achievable by using different operational settings for the respect,ive valve groupings 101.

A recirculation conduit 28 may not be included in this embodiment as only a single fuel manifold 124 is necessary to supply all nozzles 110 (both pilot and mains nozzles), and thus fuel is able to flow in it in all staging modes. Hence, the concern of thermal degradation of stagnating fuel is eliminated.

In this arrangement, the flowmeter 14' may be re-positioned downstream of the HL4U 18 to determine the flow of fuel into the (or each) manifold 124. As there is no re-circulation of fuel the fuel flow determined by the flowmeter 14' is the flow of fuel burned by the system.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure.

Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention. --For the avoidance of doubt, all the references mentioned herein are incorporated by reference.

Claims (13)

1. A turbine fuel supply system having: a plurality of first fuel nozzles for injecting fuel into a combus.tor of a turbine engine, a plurality of valves operable to communicate fuel to respective of the first fuel nozzles, a fuel manifold for communicating fuel to the valves from a fuel source, and an actuator which controls the operation of the valves, the actuator being operatively connected to the valves by a mechanical linkage.

2. A turbine fuel supply system according to claim 1, wherein the valves are adapted for mounting to a casing of the combustor.

3. A turbine fuel supply system according to claim 1 or 2, wherein the mechanical linkage comprises a unison ring.

4. A turbine fuel supply system according to claim 3, wherein the unison ring is adapted for mounting to a casing of the combustor.

5. A turbine fuel supply system according to claim 3 or 4, wherein the mechanical linkage further comprises a plurality of sub-linkages, each sub-linkage connecting the unison ring to a respective valve.

6. A turbine fuel supply system according to any one of the previous claims, wherein the actuator and mechanical linkage are at opposing sides of a fireproof seal.

7. A turbine fuel supply system according to any one of the previous claims, wherein the actuator and mechanical linkage are configured to allow fuel flow to the first fuel nozzles to be opened or shut off.

8. A turbine fuel supply system according to any one of the previous claims, wherein the actuator and mechanical linkage are configured to allow fuel flow to one or more predetermined groupings of the first fuel nozzles to be opened while the other of the first fuel nozzles are shut off.

9. A turbine fuel supply system according to any one of the previous claims, wherein the combustor is a multi-stage combustor and the first fuel nozzles are mains fuel nozzles, the system further having: a plurality of pilot fuel nozzles for injecting fuel into the combustor.

10. A turbine fuel supply system according to claim 9, further having means for varying the amount of fuel communicated to the mains fuel nozzles relative to the amount of fuel communicated to the pilot fuel nozzles.

11. A turbine fuel supply system according to claim 10, wherein the actuator and mechanical linkage are configured to allow the amount of fuel communicated to the mains fuel nozzles to be varied relative to the amount of fuel communicated to the pilot fuel nozzles.

12. A turbine fuel supply system according to claim 10, wherein the means for varying, the amount of fuel includes a splitter valve up stream of and in communication with the fuel manifold.

13. A turbine engine having the fuel supply system of any one of the previous claims.