METHOD FOR KEEPING COMBUSTION OF GAS TURBINE STABLE IN DYNAMIC PROCESS, COMPUTER READABLE MEDIUM, AND GAS TURBINE CONTROL SYSTEM

Abstract

The present disclosure provides a method for maintaining stable combustion of a gas turbine during a dynamic process, a computer-readable medium, and a gas turbine control system. The method comprises: compensating a fuel control valve stroke command δ.sub.f,CLC with a fuel flow compensation function G.sub.f,COMP(s); and compensating a VIGV command θ.sub.VIGV,CLC with an air flow compensation function G.sub.air,COMP(s), wherein the fuel flow compensation function G.sub.f,COMP(s) and the air flow compensation function G.sub.air,COMP(s) satisfy the following relation: G.sub.f,COMP(s).Math.G.sub.f(s)=G.sub.air,COMP(s).Math.G.sub.air(s), and an fuel-to-air ratio is directly proportional to δ.sub.f,CLC/θ.sub.VIGV,CLC even during the dynamic process, where G.sub.f(s) represents an overall transfer function of a fuel channel from a fuel control valve servo system to an inlet of a combustion chamber, and G.sub.air(s) represents an overall transfer function of an air channel from a VIGV servo system to the inlet of the combustion chamber.

Claims

1. A method for maintaining stable combustion of a gas turbine during a dynamic process, comprising: compensating a fuel control valve stroke command δ.sub.f,CLC with a fuel flow compensation function G.sub.f,COMP(s); and compensating a VIGV command θ.sub.VIGV,CLC with an air flow compensation function G.sub.air,COMP(s), wherein the fuel flow compensation function G.sub.f,COMP(s) and the air flow compensation function G.sub.air,COMP(s) satisfy the following relation: G.sub.f,COMP(s).Math..Math.G.sub.f(s)=G.sub.air,COMP(s).Math.G.sub.air(s), and a fuel-to-air ratio is directly proportional to $\frac{{\delta }_{f,\mathrm{CLC}}}{{\theta }_{\mathrm{VIGV},CLC}}$ during the dynamic process, wherein G.sub.f(s) represents an overall transfer function of a fuel channel from a fuel control valve servo system to an inlet of a combustion chamber; and G.sub.air(s) represents an overall transfer function of an air channel from a VIGV servo system to the inlet of the combustion chamber.

2. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1, comprising: fuel mass flow at the inlet of the combustion chamber being represented by {dot over (m)}.sub.f=G.sub.f,COMP(s).Math.K.sub.VG.sub.f(s).Math.δ.sub.f,CLC, wherein K.sub.V is a transformation coefficient between the stroke and the flow determined by valve characteristics; and air mass flow at the inlet of the combustion chamber being represented by {dot over (m)}.sub.air=G.sub.air,COMP(s).Math.K.sub.CG.sub.air(s).Math.θ.sub.VIGV,CLC wherein K.sub.C is a transformation coefficient between VIGV angle and the mass flow of an air compressor.

3. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 2, wherein the fuel-to-air ratio is: $\frac{{\dot{m}}_f}{{\dot{m}}_{\mathrm{air}}}=\frac{G_{f,\mathrm{COMP}}\left(s\right).Math.K_V{G}_f\left(s\right).Math.{\delta }_{f,\mathrm{CLC}}}{G_{\mathrm{air},COMP}\left(s\right).Math.K_C{G}_{\mathrm{air}}\left(s\right).Math.{\theta }_{\mathrm{VIGV},CLC}}=\frac{K_V{\delta }_{f,\mathrm{CLC}}}{K_C{\theta }_{\mathrm{VIGV},CLC}}.$

4. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1, further comprising: adding an additional compensator G.sub.ACCEL to the fuel channel and the air channel to accelerate the gas turbine process and improve responsiveness of the fuel channel and the air channel; the fuel mass flow at the inlet of the combustion chamber being represented by {dot over (m)}.sub.f=G.sub.ACCEL.Math.G.sub.f,COMP(s).Math.K.sub.VG.sub.f(s).Math.δ.sub.f,CLC; and the air mass flow at the inlet of the combustion chamber being represented by {dot over (m)}.sub.air=G.sub.ACCEL.Math.G.sub.air,COMP(s).Math.K.sub.CG.sub.air(s).Math.θ.sub.VIGV,CLC.

5. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 4, wherein the compensator G.sub.ACCEL is: $G_{ACCEL}=\frac{1+t_{1}s}{1+t_{2}s};$ wherein t.sub.1 and t.sub.2 are time constants, and t.sub.1>t.sub.2; and s is a complex variable of the Laplace transform.

6. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1, wherein when only the air channel is compensated to match dynamic characteristics of the fuel channel, the fuel flow compensation function is G.sub.f,COMP(s)=1, and the air flow compensation function is $G_{\mathrm{air},\mathrm{COMP}}\left(s\right)=\frac{G_f\left(s\right)}{G_{\mathrm{air}}\left(s\right)}.$

7. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1, wherein when only the fuel channel is compensated to match the dynamic characteristics of the air channel, the air flow compensation function is G.sub.air,COMP(s)=1, and the fuel flow compensation function is $G_{f,\mathrm{COMP}}\left(s\right)=\frac{G_{\mathrm{air}}\left(s\right)}{G_f\left(s\right)}.$

8. The method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1, wherein the fuel channel comprises a fuel gas channel and a fuel oil channel, and during a fuel gas operation and a fuel oil operation, the fuel control valve stroke command δ.sub.f,CLC is compensated as follows:
G.sub.f_g,COMP(s).Math.G.sub.f_g(s)=G.sub.air,COMP(s).Math.G.sub.air(s)
G.sub.f_o,COMP(s).Math.G.sub.f_o(s)=G.sub.air,COMP(s).Math.G.sub.air(s) wherein the transfer function for the fuel gas channel is G.sub.f_g(s), and the transfer function for the fuel oil channel is G.sub.f_o(s).

9. A computer-readable medium for storing computer instructions, wherein when the computer instructions are executed, the method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1 is performed.

10. A gas turbine control system, comprising a memory and a processor, wherein the memory stores computer instructions executable on the processor, and when the processor executes the computer instructions, the method for maintaining stable combustion of a gas turbine during a dynamic process of claim 1 is performed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The forgoing summary of the present disclosure and the following detailed description of embodiments of the present disclosure will be better understood when read in conjunction with the accompanying drawings. It should be noted that the drawings are merely examples of the claimed disclosure. In the figures, the same reference signs represent the same or similar elements.

[0032] FIG. 1 illustrates two processes of premixed combustion;

[0033] FIG. 2 illustrates dynamic characteristics of an air channel and a fuel channel during a dynamic operation of a gas turbine;

[0034] FIG. 3 illustrates a gas turbine control system according to one embodiment of the present disclosure;

[0035] FIG. 4 illustrates a schematic diagram of transfer functions of the fuel channel and the air channel according to one embodiment of the present disclosure;

[0036] FIG. 5 illustrates a schematic diagram of transfer functions of the entire system after compensation for a fuel control valve command δ.sub.f,CLC and a VIGV angle command θ.sub.VIGV,CLC according to one embodiment of the present disclosure;

[0037] FIG. 6 is a simplified diagram of FIG. 5;

[0038] FIG. 7 illustrates a gas turbine control system having a compensator according to one embodiment of the present disclosure;

[0039] FIG. 8 illustrates a fuel-to-air flow ratio without compensation; and

[0040] FIG. 9 illustrates a fuel-to-air flow ratio with a compensator according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0041] The detailed features and advantages of the present disclosure will be described in detail below in the detailed description of embodiments. The content is sufficient to enable those skilled in the art to understand the technical scheme of the present disclosure and implement it accordingly, and the related objectives and advantages of the present disclosure can be readily appreciated for those skilled in the art from the description, the claims, and the accompanying drawings disclosed in the present specification.

[0042] In order to ensure stable combustion and reduce NOx emissions during a dynamic process, it is necessary to accurately control the ratio of fuel flow to air flow which enters the combustion chamber. However, there is difficulty in practice because the air channels and fuel channels have different dynamic characteristics. The present disclosure discloses a new control method that can improve the fuel-to-air ratio control at an inlet of a combustor (or a burner) during the dynamic process.

[0043] FIG. 3 illustrates a gas turbine control system according to one embodiment of the present disclosure. A gas turbine is composed of an air compressor, a combustion chamber, and a turbine. Air is compressed by the air compressor, mixed with fuel in the combustion chamber for combustion, and then expands to do work in the turbine. The air flow, or the air mass flow, is adjusted by variable inlet guide vane (VIGV) at an inlet of the air compressor. The fuel flow, or the fuel mass flow, is adjusted by a fuel control valve on a fuel delivery pipe. A variable inlet guide vane (VIGV) servo system and the fuel control valve are controlled based on an electrical signal received from the gas turbine control system. An input/output card is configured to convert a digital signal into the electrical signal. The digital signal includes, but is not limited to, a fuel control valve stroke command δ.sub.f,CLC and a VIGV angle command δ.sub.VIGV,CLC As shown in FIG. 3, the fuel control valve stroke command δ.sub.f,CLC is generated in a closed-loop controller. The VIGV angle command δ.sub.VIGV,CLC is also calculated in the closed-loop controller.

[0044] As shown in FIG. 4, the fuel control valve stroke command δ.sub.f,CLC and the fuel mass flow {dot over (m)}.sub.f,B-i that enters the i-th burner (referred to as burner i) or the i-th combustor (referred to as combustor i) in the combustion chamber have the relation as follows:

{dot over (m)}.sub.f,B-i=K.sub.VG.sub.V(s).Math.G.sub.FDS(s).Math.K.sub.f,B-iG.sub.f,B-i(s).Math.δ.sub.f,CLC [0045] where K.sub.V is a transformation coefficient between the stroke and the flow, determined by valve characteristics; G.sub.V(s) denotes the dynamic characteristics of the valve servo; G.sub.FDS(s) denotes a transfer function of a fuel distribution system; and K.sub.f,B-i denotes the ratio of Burner i fuel mass flow to the total fuel mass flow. G.sub.f,B-i(s) is a transfer function of a fuel branch pipe before the Burner i. s denotes a complex variable of the Laplace transform.

[0046] Also as shown in FIG. 4, the variable inlet guide vane (VIGV) angle command θ.sub.VIGV,CLC and the air mass flow {dot over (m)}.sub.air,B-i that enters Burner i have the relation as follows:

{dot over (m)}.sub.air,B-i=G.sub.VIGV(s).Math.K.sub.CG.sub.C(s).Math.K.sub.air,B-i.Math.θ.sub.VIGV,CLC [0047] where G.sub.VIGV(s) is the transfer function of the VIGV servo. K.sub.C is the transformation coefficient between the VIGV angle and the mass flow of the air compressor. G.sub.C(s) is the transfer function of the dynamic characteristics of the air compressor. K.sub.air,B-i is the ratio of Burner I air mass flow to the total air mass flow.

[0048] From the above two equations, it can be seen that the fuel channel and the air channel have different dynamic characteristics (different transfer functions). As shown in FIG. 5, a compensator can be added after the fuel control valve strole command f,CLC and the VIGV angle command δ.sub.VIGV,CLC wherein the compensator is realized through a fuel command compensation function and an air command compensation function. The fuel command compensation function G.sub.f,B-i,COMP(s) is added for the fuel channel of burner i, and the air command compensation function G.sub.air,B-i,COMP(s) is added for the air channel.

[0049] The compensator in FIG. 5 is designed for burner i. In practice, only one combustor can be selected for compensation. The combustor may be the most critical combustor, or may be a virtual average combustor. With the burner to be compensated already selected, FIG. 5 can be simplified to FIG. 6. The above two equations can also be simplified as follows:

{dot over (m)}.sub.f=G.sub.f,COMP(s).Math.K.sub.VG.sub.f(s).Math.δ.sub.f,CLC

{dot over (m)}.sub.air=G.sub.air,COMP(s).Math.K.sub.CG.sub.air(s).Math.θ.sub.VIGV,CLC [0050] where G.sub.f,COMP(s) is the compensator added to the fuel control valve stroke command, and G.sub.f(s) is the overall transfer function of the fuel channel from the control valve to the inlet of the burner (or the combustor). G.sub.air,COMP(s) is the compensator added to the VIGV angle command, and G.sub.air(s) is the overall transfer function of the air channel from the VIGV servo system to the inlet of the burner.

[0051] Depending on the purpose, the two compensators can be designed in different ways. For example, in order to ensure that the dynamic behavior of the fuel-to-air ratio at the inlet of the combustion chamber is as designed, the two compensators can be designed in a way to fulfill the following relation:

G.sub.f,COMP(s).Math.G.sub.f(s).Math.G.sub.air,COMP(s).Math.G.sub.air(s)

[0052] The compensator is introduced for the purpose as follows.

[0053] As shown in FIG. 7, it is considered to increase the fuel mass flow and the air mass flow linearly to keep the fuel-to-air flow ratio constant. Although the fuel control valve stroke command and VIGV angle command can be correctly generated in the closed-loop controller to linearly increase the fuel mass flow and the air mass flow, the actual fuel-to-air flow ratio at the inlet of the combustion chamber fluctuates as shown in FIG. 8. This is because the fuel channel and the air channel have different dynamic characteristics (transfer functions). For example, the maximum fuel-to-air flow ratio is 0.5076, which is 0.076 higher than is 0.5. This is equivalent to a fluctuation of about 22° C. in the flame temperature, which is enough to cause the combustion stability problem. By using the compensators disclosed in the present disclosure, the fuel-to-air flow ratio can be reduced as shown in FIG. 9. It should be noted that the compensator cannot be perfect, and a small fluctuation may still exist.

[0054] The specific embodiments of the present disclosure are implemented in a straightforward way. As shown in FIG. 7, the fuel control valve stroke command δ.sub.f,CLC is compensated with the fuel flow compensator G.sub.f,COMP(s) before being sent to the input/output card. Similarly, the VIGV command θ.sub.VIGV,CLC is compensated with the air flow compensator G.sub.air,COMP(s) before being sent to the input/output card. The two compensators can be implemented directly into the gas turbine control system in the form of programs.

[0055] For the specific design for the compensators, reference can be made to the description below.

[0056] The transfer function of the fuel channel from the fuel control valve to the inlet of the combustor (or the burner) is different from the transfer function of the air channel from the VIGV to the inlet of the combustor (or the burner). As shown in FIG. 6, the control valve stroke command and the VIGV angle command can be compensated. As a result, the fuel mass flow and the air mass flow at the inlet of the combustor (or burner) can be respectively calculated using the following formulas:

{dot over (m)}.sub.f=G.sub.f,COMP(s).Math.K.sub.VG.sub.f(s).Math.δ.sub.f,CLC

{dot over (m)}.sub.air=G.sub.air,COMP(s).Math.K.sub.CG.sub.air(s).Math.θ.sub.VIGV,CLC

[0057] In order to make that the dynamic behavior of the fuel-to-air ratio at the inlet of the combustion chamber is as designed, the two compensators can be designed in a way to fulfill the following relation:

G.sub.f,COMP(s).Math.G.sub.f(s)=G.sub.air,COMP(s).Math.G.sub.air(s)

[0058] Obviously,

[00006]$\frac{{\dot{m}}_f}{{\dot{m}}_{\mathrm{air}}}=\frac{G_{f,\mathrm{COMP}}\left(s\right).Math.K_V{G}_f\left(s\right).Math.{\delta }_{f,\mathrm{CLC}}}{G_{\mathrm{air},COMP}\left(s\right).Math.K_C{G}_{\mathrm{air}}\left(s\right).Math.{\theta }_{\mathrm{VIGV},CLC}}=\frac{K_V{\delta }_{f,\mathrm{CLC}}}{K_C{\theta }_{\mathrm{VIGV},CLC}}$

[0059] since K.sub.V and K.sub.C are transformation coefficients, the fuel-to-air ratio is directly proportional to

[00007]$\frac{{\delta }_{f,\mathrm{CLC}}}{{\theta }_{\mathrm{VIGV},CLC}}$

even during the dynamic process.

[0060] In one embodiment, only the air channel is compensated to match the dynamic characteristics of the fuel channel, and in this case the compensator can be designed as follows:

[00008]$G_{f,\mathrm{COMP}}\left(s\right)=1$$G_{\mathrm{air},\mathrm{COMP}}\left(s\right)=\frac{G_f\left(s\right)}{G_{\mathrm{air}}\left(s\right)}$

[0061] Obviously,

G.sub.f,COMP(s).Math.G.sub.f(s)=G.sub.air,COMP(s).Math.G.sub.air(s)=G.sub.f(s)

[0062] In one embodiment, only the fuel channel is compensated to match the dynamic characteristics of the air channel, and in this case the compensator can be designed as follows:

[00009]$G_{f,\mathrm{COMP}}\left(s\right)=1$$G_{\mathrm{air},\mathrm{COMP}}\left(s\right)=\frac{G_f\left(s\right)}{G_{\mathrm{air}}\left(s\right)}$

[0063] Obviously,

G.sub.f,COMP(s).Math.G.sub.f(s)=G.sub.air,COMP(s).Math.G.sub.air(s)=G.sub.air(s)

[0064] In one embodiment, since fuel gas is compressible while fuel oil is incompressible, the transfer function G.sub.f_g(s) of the fuel gas channel is significantly different from the transfer function G.sub.f_o(s) of the fuel oil channel. As a result, the control valve stroke command should be compensated differently during the fuel gas operation and the fuel oil operation.

G.sub.f_g,COMP(s).Math.G.sub.f_g(s)=G.sub.air,COMP(s).Math.G.sub.air(s)

G.sub.f_o,COMP(s).Math.G.sub.f_o(s)=G.sub.air,COMP(s).Math.G.sub.air(s)

[0065] In one embodiment, an additional compensator G.sub.ACCEL may also be added to both the fuel channel and the air channel.

{dot over (m)}.sub.f=G.sub.ACCEL.Math.G.sub.f,COMP(s).Math.K.sub.VG.sub.f(s).Math.δ.sub.f,CLC

{dot over (m)}.sub.air=G.sub.ACCEL.Math.G.sub.air,COMP(s).Math.K.sub.CG.sub.air(s).Math.θ.sub.VIGV,CLC

[0066] When the fuel channel or the air channel has a relatively large volume, or when the control valve servo and the VIGV servo are relatively slow, the fuel mass flow f and the air mass flow {dot over (m)}.sub.air at the inlet of the combustor have a larger delay than the command in the control system. G.sub.ACCEL is designed to accelerate the process and improve the response of the fuel channel and the air channel. For example, G.sub.ACCEL can be designed as the transfer function as follows:

[00010]$G_{ACCEL}=\frac{1+t_{1}s}{1+t_{2}s}$ [0067] where t.sub.1 and t.sub.2 are time constants, and t.sub.1>t.sub.2; and s is a complex variable of the Laplace transform.

[0068] As indicated in the present application and the claims, the words “a”, “an” and/or “the” do not refer in particular to the singular but may also include the plural, unless the context clearly indicates an exception. In general, the terms “comprising” and “including” only indicates the inclusion of clearly identified steps and elements, but these steps and elements do not constitute an exclusive list, and a method or a device may also include other steps or elements.

[0069] Although the present application makes various references to some modules in the system according to the embodiments of the present application, any number of different modules can be used and operated in the gas turbine control system. The modules are illustrative only, and different modules may be used in different aspects of the system and the method.

[0070] Also, in the present application, specific words are used to describe the embodiments of the present application. For instance, the expressions “one embodiment”, “an embodiment” and/or “some embodiments” refer to a certain feature, structure, or characteristic associated with at least one embodiment of the present application. Therefore, it should be emphasized and noted that two or more references to “an embodiment”, “one embodiment”, or “an alternative embodiment” in different places in the present specification do not necessarily refer to the same embodiment. In addition, some of the features, structures, or characteristics of one or more embodiments of the present application can be combined as appropriate.

[0071] Further, those skilled in the art can understand that the aspects of the present application may be illustrated and described in terms of several patentable categories or circumstances, including any new and useful process, machine, product or combination of substances, or any new and useful improvements to them. Accordingly, the aspects of the present application may be entirely executed by hardware, or entirely executed by software (including firmware, resident software, microcode, etc.), or executed by a combination of hardware and software. The above hardware or software may be referred to as “data block”, “module”, “engine”, “unit”, “component” or “system”. In addition, the aspects of the present application may be embodied as a computer product, including computer-readable program, on one or more computer-readable media.

[0072] A computer-readable signal medium may include a data propagating signal that contains a computer program, for example, on baseband or as part of a carrier. The propagating signal may be in many forms, including electromagnetic form, optical form, etc., or a suitable combination. A computer-readable signal medium may be any computer-readable medium other than a computer-readable storage medium, which can be connected to an instruction executable system, apparatus, or device to communicate, propagate, or transmit a program for use. The program code on a computer-readable signal medium may be transmitted over any suitable medium, including radio, a cable, a fiber optic cable, RF, or the like, or a combination of any of the above media.

[0073] The computer program codes required for the operation of the present application can be written in any one or more programming languages, including object-oriented programming languages (such as Java, Scala, Smalltalk, Eiffel, JADE, Emerald, C++, C #, VB.NET, and Python), conventional programming languages (such as C language, Visual Basic, Fortran 2003, Perl, COBOL 2002, PHP, and ABAP), dynamic programming languages (such as Python, Ruby, and is Groovy) or other programming languages. The program codes may entirely run on the user computer, or run on the user computer as an independent software package, or run partly on the user computer and partly on a remote computer, or entirely run on the remote computer or a server. In the latter case, the remote computer can be connected to the user computer through any form of network, such as local area network (LAN) or wide area network (WAN), or connected to an external computer (such as through the Internet), or used in a cloud computing environment, or used as a service, such as Software as a Service (SaaS).

[0074] The terms and expressions used herein are for description only, and the present disclosure should not be limited to those terms and expressions. Using those terms and expressions does not mean to exclude any equivalent features shown and described (or partially), and it should be recognized that various modifications may also be included within the scope of the claims. There may also be other modifications, changes, and substitutions. Accordingly, the claims should be considered to cover all such equivalents.

[0075] Similarly, it should be noted that, although the present disclosure has been described with reference to the present particular embodiments, the ordinary skilled in the art should appreciate that the forgoing embodiments are only for illustrating purpose, and various equivalent changes or replacements can be made without departing from the spirit of the present disclosure. Therefore, changes and variations to the forgoing embodiments within the spirit of the present disclosure shall all fall within the scope of the claims of the present application.