The present disclosure relates to a gas turbine control system, and in particular to a control method for a gas turbine control system.
The market requirements with regard to the flexibility of gas turbines have been increasing. In addition to normal frequency response, dynamic operations such as fast start-up, load rejection, island-mode operation, and extended frequency response are also often requested by the customers. The stability of the gas turbine during these dynamic operations is becoming more and more important.
In order to reduce NOx emissions, premixed combustion is adopted in modern gas turbines. As shown in
The premixed combustion has generally two limits: flame flashback (which typically occurs when too much fuel is present) and flame extinction (which typically occurs when little fuel is present). When combustion condition is close to the two limits, combustion vibration occurs. Premixed flames have usually a much narrower operation range in terms of fuel-to-air ratios as compared to diffusional flames.
As shown in
This is one of the main reasons that a more than enough margin has to be kept between the operation line and the lean combustion limit. This results in a higher NOx emission. In addition, the difficulty of fuel-to-air ratio control during such a transient process also limits the dynamic performance of the gas turbine.
Therefore, there is a need for a method that can improve the accuracy of the fuel-to-air ratio control for the gas turbine during dynamic process.
The present disclosure proposes a new control method applicable to a gas turbine control system. Fuel flow and air flow which enter a combustion chamber are dynamically matched such that the purposes of maintaining stable combustion during a dynamic process and reducing NOx emissions, etc. are achieved.
The present disclosure provides a method for maintaining stable combustion of a gas turbine during a dynamic process. The method comprises:
during the dynamic process,
In one embodiment, the method comprises:
In one embodiment, the fuel-to-air ratio is:
In one embodiment, the method further comprises:
In one embodiment, the compensator GACCEL is:
In one embodiment, when only the air channel is compensated to match the dynamic characteristics of the fuel channel, the fuel flow compensation function is Gf,COMP(s)=1, and the air flow compensation function is
In one embodiment, when only the fuel channel is compensated to match the dynamic characteristics of the air channel, the air flow compensation function is Gair,COMP(s)=1, and the fuel flow compensation function is
In one embodiment, 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 δf,CLC is compensated as follows:
G
f_g,COMP(s)·Gf_g(s)=Gair,COMP(s)·Gair(s)
G
f_o,COMP(s)·Gf_o(s)=Gair,COMP(s)·Gair(s)
The present disclosure further provides a computer-readable medium storing computer instructions, wherein when the computer instructions are executed, the method for maintaining stable combustion of a gas turbine during a dynamic process is performed.
The present disclosure further provides 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 is performed.
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.
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.
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.
As shown in
{dot over (m)}
f,B-i
=K
V
G
V(s)·GFDS(s)·Kf,B-iGf,B-i(s)·δf,CLC
Also as shown in
{dot over (m)}
air,B-i
=G
VIGV(s)·KCGC(s)·Kair,B-i·θVIGV,CLC
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
The compensator in
{dot over (m)}
f
=G
f,COMP(s)·KVGf(s)·δf,CLC
{dot over (m)}
air
=G
air,COMP(s)·KCGair(s)·θVIGV,CLC
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
f,COMP(s)·Gf(s)·Gair,COMP(s)·Gair(s)
The compensator is introduced for the purpose as follows.
As shown in
The specific embodiments of the present disclosure are implemented in a straightforward way. As shown in
For the specific design for the compensators, reference can be made to the description below.
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
{dot over (m)}
f
=G
f,COMP(s)·KVGf(s)·δf,CLC
{dot over (m)}
air
=G
air,COMP(s)·KCGair(s)·θVIGV,CLC
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
f,COMP(s)·Gf(s)=Gair,COMP(s)·Gair(s)
Obviously,
since KV and KC are transformation coefficients, the fuel-to-air ratio is directly proportional to
even during the dynamic process.
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:
Obviously,
G
f,COMP(s)·Gf(s)=Gair,COMP(s)·Gair(s)=Gf(s)
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:
Obviously,
G
f,COMP(s)·Gf(s)=Gair,COMP(s)·Gair(s)=Gair(s)
In one embodiment, since fuel gas is compressible while fuel oil is incompressible, the transfer function Gf_g(s) of the fuel gas channel is significantly different from the transfer function Gf_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
f_g,COMP(s)·Gf_g(s)=Gair,COMP(s)·Gair(s)
G
f_o,COMP(s)·Gf_o(s)=Gair,COMP(s)·Gair(s)
In one embodiment, an additional compensator GACCEL may also be added to both the fuel channel and the air channel.
{dot over (m)}
f
=G
ACCEL
·G
f,COMP(s)·KVGf(s)·δf,CLC
{dot over (m)}
air
=G
ACCEL
·G
air,COMP(s)·KCGair(s)·θVIGV,CLC
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)}air at the inlet of the combustor have a larger delay than the command in the control system. GACCEL is designed to accelerate the process and improve the response of the fuel channel and the air channel. For example, GACCEL can be designed as the transfer function as follows:
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.
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.
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.
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.
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.
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).
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.
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.
Number | Date | Country | Kind |
---|---|---|---|
202011249514.2 | Nov 2020 | CN | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/CN2021/080289 | 3/11/2021 | WO |