Redundant electro-hydraulic servo valve (EHSV) control in fuel metering system

Abstract

A redundant fuel metering system and method for a multi-stage combustion chamber that uses a fuel metering valve EHSV of a less critical combustion chamber stage fuel metering system as a redundant backup for a main metering valve EHSV. In the event of a failure of the primary FMV EHSV, the control module signals the delivery system to switch control of the primary FMV to a less critical combustion chamber stage fuel metering system EHSV, thus maintaining control of the primary combustion chamber FMV. When doing so, the delivery valve then drives the less critical combustion chamber stage fuel metering system (FMV) to its fail-safe position while maintaining control of the main system.

Description

Technical Field

[0001] The present invention relates generally to multi-stage gas turbine fuel systems and, more particularly, to a multi-stage gas turbine fuel system where redundant control of fuel metering units is required to ensure continued primary combustor operation in the event of a primary fuel control failure. Background Art

[0002] A typical multi-stage gas turbine fuel system, such as that described in U.S. Pat. No. 7,096,658, entitled Centrifugal Pump Fuel System and Method for a Gas Turbine Engine, to Wernberg et al. (hereinafter "the '658 patent," the teachings and disclosure of which are incorporated herein by reference in their entirety), utilizes a single fuel metering unit (FMU) to meter fuel flow downstream to a main combustor stage as needed (e.g., to power an aircraft). The FMU typically includes a single main reliable fuel metering valve (FMV). The FMV may include a dual-channel linear variable displacement transducer (LVDT) to provide feedback of the fuel metering valve position. The position of the FMV is used by an electronic engine controller (EEC) to regulate the metered fuel flow. The EEC positions the FMV by providing an electrical signal to an electrohydraulic servo valve (EHSV), which provides hydraulic muscle to adjust the FMV to the desired position.

[0003] To increase the redundancy of fuel control for applications such as that described in the '658 patent, and in view of the increasing criticality of the main combustor stage in such and other applications, the main fuel metering system 101 utilizes redundant EHSVs 103, 105 to control the FMV 107 of the FMU, such as Figure 1 To provide this redundancy, a transfer system including a transfer valve 109 is included to allow the EEC to select which of the two redundant EHSVs 103, 105 to use to control the FMV 107. In the event of a control failure to the EHSV 103, the EEC can then signal the transfer system to switch control to the second EHSV 105 via the transfer valve 107, thereby maintaining control of the FMV 107.

[0004] As described in the '658 patent, such a multi-stage system may also include additional combustor stages, each of which may include a similar fuel control system 111. In the exemplary embodiment described in the '658 patent, such additional combustor stages may include afterburner zones, each of which may utilize an afterburner or secondary fuel control system 111 to provide a metered flow to each secondary zone. Figure 1 Only a single additional secondary fuel control system 111 is shown in FIG. 1 , but multiple additional fuel control systems may be utilized for additional secondary combustor stages.

[0005] The secondary fuel metering system 111 includes a single FMV 113 and a dual channel LVDT to provide feedback of the FMV position. The EEC uses the position of the FMV 113 to regulate the metered fuel flow to each secondary zone. As with the main combustor stage fuel control 101, the EEC positions each FMV 113 by providing an electrical signal to an EHSV 115, which provides the hydraulic muscle to adjust the FMV 113 to the desired position. Unlike the main combustor stage, which has evolved to include redundant EHSV controls, these additional combustor stages are generally less critical and therefore the added cost and weight of such redundant control components is generally not justified.

[0006] Although Figure 1 The figure shows the normal operating mode of the existing fuel metering system with redundant EHSVs 103, 105, but Figure 2 The diagram shows the operation when a fault occurs in controlling the EHSV 103. Figure 1 In the process, the delivery valve 109 (see also Figure 5 ) is positioned so that control pressure from the main channel A EHSV 103 is supplied via solid lines 117, 119 to position the main FMV 107. Control pressure from the main channel B EHSV 105, as shown by dashed line 121, is blocked from the main FMV 107 at the delivery valve 109. Control of the additional combustor stage metering system EHSV 115 is not tied to the main metering system, even though it is in a parallel fluid circuit (or in some embodiments a separate fluid circuit).

[0007] exist Figure 2, the delivery system is positioned so that control pressure from the main channel B EHSV 105 is supplied via solid lines 121, 119 to position the main FMV 107. Control pressure from the main channel A EHSV 103, now shown as dashed line 117, is blocked from the main FMV 107 at the delivery valve 109. This switching of the control EHSV represents a failure of the main channel A EHSV 103. The control of the secondary metering system EHSV 115 is not linked to the main metering system and is therefore not affected by the failure and switching of metering control in the main combustor stage.

[0008] Figure 5 A more detailed flow diagram of this prior art redundant system is provided, showing details of three EHSVs 103, 105, 115, a transfer valve 109 (a tri-land transfer valve in the illustrated embodiment), and FMVs 107, 113 for the primary combustor stage and one of the secondary combustor stages, respectively. Note that this prior art system utilizes single coil EHSVs 103, 105 to redundantly control the primary FMV 107, while a dual coil EHSV 115 is used for the secondary FMV 113. In embodiments including multiple additional stages, for example, in Figure 5 Two additional stages are shown in FIG. 1 , and similarly controlled EHSVs and FMVs for additional combustor stages may also be used as appropriate.

[0009] As will be apparent from the foregoing, redundant EHSVs 103, 105 are provided to maintain operation and control of the critical main combustor stage FMV 107 in the event of a failure of the control EHSV 103, resulting in the use of three EHSVs 103, 105, 115 to control two combustor stages. Unfortunately, this redundancy of the main combustor stage comes at the expense of increased weight and cost. For embodiments deployed on an aircraft, this additional weight carries its own additional cost in addition to the component cost due to increased fuel burn.

[0010] What is needed is a fuel control system for a multi-stage combustor that provides redundant FMV EHSVs to ensure primary reliability of the primary combustor metering system, but does not add undesirable cost, weight, size, and complexity to the engine. Embodiments of the present invention provide such a system that eliminates dedicated redundant EHSVs and minimizes hardware associated with connectors, wiring harnesses, and EECs. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. Summary of the invention

[0011] In view of the above, embodiments of the present invention provide a new and improved fuel control system for a multi-stage gas turbine engine. More specifically, embodiments of the present invention provide a new and improved fuel control system for a multi-stage gas turbine engine that provides redundant fuel metering control for at least one critical combustor. More specifically, embodiments of the present invention provide such redundant control by utilizing FMV EHSVs that are utilized during trouble-free operation to control fuel metering to different stages, thereby ensuring the primary reliability of the main combustor metering system. Such embodiments do not add undesirable cost, weight, size and / or complexity to the system. Embodiments of the present invention provide such a system while eliminating dedicated redundant EHSVs for the main combustor stage and also minimizing the hardware associated with connectors, wiring harnesses, and EECs.

[0012] In one embodiment, the system uses only two dual-channel servo valves total to provide normal, trouble-free operation of the primary and secondary combustor stages, and to provide redundant, fail-safe operation of the primary combustor stage during failure of one of the dual-channel servo valves controlling fuel metering to the primary combustor stage. In one embodiment, a multi-land transfer valve is utilized to transfer fuel metering control from the failed dual-channel servo valve of the primary combustor stage to the operative dual-channel servo valve of the secondary combustor stage. In such a preferred embodiment, the multi-land transfer valve also drives the FMV of the secondary combustor stage to a fail-safe mode of operation. In an embodiment, the multi-land transfer valve may be a quad-land transfer valve.

[0013] Such an embodiment reduces the space usage / weight of the overall fuel metering system and increases the mean time between failures (MTBF) by reducing electrical components. In one embodiment, the servo valve is a standardized dual coil servo valve.

[0014] Other aspects, objects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the present invention. In the drawings:

[0016] Figure 1 is a simplified block diagram of a prior art fuel metering system for a multi-stage combustor having redundant fuel metering control of a primary stage combustor, illustrating normal, trouble-free operation;

[0017] Figure 2 for Figure 1A simplified block diagram of a prior art fuel metering system for a multi-stage combustor having redundant fuel metering control of a primary stage combustor illustrating redundant fuel metering operation of the primary stage combustor during a failure of the primary FMV control;

[0018] Figure 3 A simplified block diagram of an embodiment of a fuel metering system for a multi-stage combustor having redundant fuel metering control of a main stage combustor constructed in accordance with the teachings of the present invention, illustrating normal, trouble-free operation;

[0019] Figure 4 for Figure 3 A simplified block diagram of a fuel metering system for a multi-stage combustor having redundant fuel metering control of a main stage combustor, illustrating redundant fuel metering operation of the main stage combustor during a primary FMV control failure;

[0020] Figure 5 for Figure 1 A partially detailed illustration of certain fuel metering components of a prior art fuel metering system; and

[0021] Figure 6 According to the teachings of the present invention, Figure 3 A partial detailed illustration of certain fuel metering components of an embodiment of a fuel metering system.

[0022] While the present invention will be described in conjunction with certain preferred embodiments, it is not intended to be limited to those embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents included within the spirit and scope of the present invention as defined by the appended claims. DETAILED DESCRIPTION

[0023] Turning now to the drawings, and in particular to Figure 3 , Figure 4 and Figure 6 , there is illustrated an embodiment of a fuel control system for a multi-stage combustor system that provides redundant fuel metering control of a primary combustor stage by utilizing a control valve from a secondary combustor stage. In the illustrated embodiment and as will be discussed more fully below, a multi-land transfer valve is used to switch control of a fuel metering valve from a failed servo valve to an operating servo valve of a secondary, less critical staged combustor. The transfer valve also drives the fuel metering valve of the secondary, less critical staged combustor to a fail-safe position. However, it should be noted that the present invention is not limited to the illustrated embodiment, and such embodiment should be considered as an example and not a limitation.

[0024] Figure 3An embodiment of the invention is shown having a primary fuel metering system 100 and at least one secondary (e.g., afterburner) fuel metering system 102 each operating in a normal operating mode. The delivery valve 102 is positioned so that control pressure from the primary EHSV 104 is supplied to position the primary FMV 106, as shown in solid lines 108, 110. Control pressure from the EHSV 112 of the secondary combustor fuel metering system 102, or a designated area of ​​a secondary zone (as described in the '658 patent discussed above and incorporated by reference), is blocked from the primary FMV 106 at the delivery valve 102, as shown in dashed line 114. During this normal operation, the designated area of ​​the secondary fuel system is available, and fuel flow to that area is metered by the secondary zone FMV 116 as commanded by the EEC via the secondary zone EHSV 112, as shown in solid line 118.

[0025] Figure 4 The diagram shows Figure 3 106 . The embodiment of the invention is in its backup operating mode, which provides redundant FMV 106 control during a failure of the primary EHSV 104. In this mode, the transfer valve 102 is positioned so that the control pressure from the EHSV 112 of the designated area of ​​the secondary fuel metering system is supplied to position the primary FMV 106, as shown by the solid lines 114, 110. The control pressure from the primary EHSV 104 is blocked from the primary FMV 106 at the transfer valve 102, as shown by the dashed line 108. In this position, the transfer valve 102 provides a hydraulic signal (hereinafter referred to as Figure 6 ), the hydraulic signal drives the secondary region FMV 116 to its fail-safe, e.g., closed, position.

[0026] Figure 6 Show Figure 3 A more detailed fuel flow diagram of an embodiment of the present invention is shown in FIG. 1 , which is in and operating in its normal operating mode. The delivery system including the delivery EHSV 120 driving the multi-land delivery valve 102 is positioned so that the control pressure supplied from the main EHSV 104 is used to position the main FMV 106. Although the Figure 3 A multi-land piston is shown for the transfer valve 102, but as one skilled in the art will recognize from the foregoing, additional lands may be added to add additional functionality. The control pressure from the EHSV 112 of the designated zone of the secondary fuel system is blocked from the primary FMV 106 at the transfer valve 102. During this normal operation, the designated zone of the secondary fuel system is available and fuel flow to that zone is metered by the secondary zone FMV 116 as commanded by the EEC via the secondary EHSV 112.

[0027] If the primary EHSV 104 fails, the transfer EHSV 120 moves the piston of the transfer valve 102 so that the control pressure from the EHSV 112 of the designated zone of the secondary fuel system is now supplied to position the primary FMV 106. The control pressure from the primary EHSV 104 is blocked from the primary FMV 106 by the land of the transfer valve 102. In this position, the transfer valve 102 provides a hydraulic signal at a pressure Ps that drives the secondary zone FMV 116 to its fail-safe, e.g., closed position, via line 122.

[0028] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference in its entirety and were set forth herein.

[0029] The use of the terms "a" (indefinite article "a" or "an") and "the" and similar references in describing the present invention (especially in the following claims) is interpreted to cover the singular and the plural, unless otherwise stated herein or clearly contradicted by the context. The terms "comprising", "having", "including" and "containing" are interpreted as open terms (i.e., meaning "including, but not limited to"), unless otherwise noted. The statement of numerical ranges herein is intended only to be used as a shorthand for individually referring to each individual numerical value falling within the range, unless otherwise stated herein, and each individual numerical value is incorporated into this specification as if it were individually stated herein. All methods described herein can be performed in any suitable order, unless otherwise stated herein or clearly contradicted by the context. Any and all examples provided herein, or the use of exemplary language (e.g., "such as") are intended only to better illustrate the present invention and do not cause limitation on the scope of the present invention, unless otherwise required. No language in the specification should be interpreted as indicating any unclaimed element as necessary for the practice of the present invention.

[0030] Preferred embodiments of the present invention are described herein, including the best modes known to the inventors for carrying out the present invention. Variations of these preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors expect that skilled persons will appropriately adopt such variations, and the inventors intend to practice the present invention in a manner different from that specifically described herein. Therefore, as permitted by applicable law, the present invention includes all variations and equivalents of the subject matter recorded in the appended claims. Moreover, the present invention is included in any combination of the above elements in all possible variations, unless otherwise stated herein or clearly contradicted by the context.

Claims

1. A fuel metering system for a multi-stage combustion system having a primary combustion stage and at least one secondary combustion stage, comprising: a main fuel metering system configured to supply fuel to the main combustion stage, the main fuel metering system having a main electrohydraulic servo valve (EHSV) fluidly coupled to a main system fuel metering valve (FMV) through a transfer valve; a secondary fuel metering system configured to supply fuel to the secondary combustion stage, the secondary fuel metering system having a secondary electrohydraulic servo valve (EHSV) fluidly coupled to a secondary fuel metering valve (FMV) and the primary system fuel metering valve (FMV) via the transfer valve; and Wherein the transfer valve includes a multi-land piston configured to provide control pressure from a primary EHSV to a primary FMV to control its positioning during a normal mode of operation and to provide control pressure from a secondary EHSV to a primary FMV to control its positioning during a backup mode of operation.

2. The system according to claim 1, wherein: The transfer valve is further configured to provide a hydraulic control signal to a secondary FMV to drive it to a fail-safe position during the backup mode of operation.

3. The system according to claim 1, wherein: The multi-land piston of the delivery valve is at least a four-land piston.

4. The system according to claim 1, wherein: The transfer valve is configured to block control pressure from the secondary EHSV to the primary FMV during a normal mode of operation and to block control pressure from the primary EHSV to the primary FMV during a backup mode of operation.

5. The system according to claim 1, wherein: The multi-land piston of the delivery valve is positioned by the delivery EHSV.

6. The system according to claim 5, wherein: The delivery EHSV is a double-coil EHSV.

7. The system according to claim 1, wherein: The primary EHSV and the secondary EHSV are each a dual-coil EHSV.

8. A fuel metering system for a combustion system having a first combustion chamber and a second combustion chamber, comprising: a first fuel metering system configured to supply fuel to the first combustion chamber, the first fuel metering system having a first electrohydraulic servo valve (EHSV) fluidly coupled to a first system fuel metering valve (FMV) via a delivery system; as well as a second fuel metering system configured to supply fuel to the second combustion chamber, the second fuel metering system having a second electrohydraulic servo valve (EHSV) fluidly coupled to a second fuel metering valve (FMV) and the first fuel metering valve (FMV) via the delivery system; and Wherein, the delivery system includes a fuel delivery valve having a multi-land piston, and the multi-land piston is configured to provide control pressure from the first EHSV to the first FMV to control its positioning during a normal mode of operation, and to provide control pressure from the second EHSV to the first FMV to control its positioning during a standby mode of operation.

9. The system according to claim 8, wherein: The transfer valve is further configured to provide a hydraulic control signal to the second FMV to drive it to a fail-safe position during a backup mode of operation.

10. The system according to claim 8, wherein: The multi-land piston of the delivery valve is at least a four-land piston.

11. The system according to claim 8, wherein: The transfer valve is configured to block control pressure from the second EHSV to the first FMV during a normal mode of operation and to block control pressure from the first EHSV to the first FMV during a backup mode of operation.

12. The system according to claim 8, wherein: The multi-land piston of the delivery valve is positioned by the delivery EHSV.

13. The system according to claim 12, wherein: The delivery EHSV is a double-coil EHSV.

14. The system according to claim 8, wherein: The first EHSV and the second EHSV are each a double-coil EHSV.

15. A method of metering fuel for a multi-stage combustion system having a primary combustion stage and at least one secondary combustion stage, comprising the steps of: During a normal mode of operation, the position of the main system fuel metering valve (FMV) is controlled via the main electrohydraulic servo valve (EHSV); During a normal mode of operation, controlling the position of a secondary system fuel metering valve (FMV) via a secondary electrohydraulic servo valve (EHSV); and During a backup mode of operation, the position of the main system fuel metering valve (FMV) is controlled via the secondary electrohydraulic servo valve (EHSV).

16. The method of claim 15 further comprising the step of actuating the secondary system fuel metering valve (FMV) to a fail-safe position during a standby mode of operation.

17. The method of claim 15, further comprising the step of blocking the master EHSV from controlling the position of the master FMV during a standby mode of operation.

18. The method of claim 15, further comprising the step of blocking said secondary EHSV from controlling said position of said secondary FMV during a standby mode of operation.

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