Abstract:
It is desirable for a gas turbine system to operate in a wide range operating conditions. However, under certain conditions there exist dynamic boundaries that limit a combustor from reaching its designated condition. Perturbation devices formed of electromagnetic plates can be incorporated into fuel nozzles of the combustor to influence the dynamics so that the range of operating conditions can be widened. The perturbation devices vibrate according to the perturbation signals provided from a dynamics controller. The vibration characteristics of the perturbation devices can be controlled by controlling the attributes of the perturbation signals. The vibrations influence the dynamics of fluid—fuel, oxidant, or both—flowing past the perturbation devices within the fuel nozzles.

Description:
[0001]    One or more aspects of the present invention relate to method, apparatus and system for controlling combustion dynamics in a gas turbine combustor. In particular, one or more aspects relate to active control of fuel nozzle system to improve the combustion dynamics during combustion operation. 
       BACKGROUND OF THE INVENTION  
       [0002]    It is desirable for a gas turbine combustor to operate in a wide range operating conditions. However, under certain conditions there exist dynamic boundaries that limit a combustor from reaching its designated condition. Combustor dynamics refer to the pressure oscillations and/or pulsations that occur during combustion. These dynamics can become destructive to the gas turbine itself, for example, at resonant frequencies. Also, undesirable effects such as increase emission of NOx can occur. 
         [0003]    It would be desirable to utilize influence the combustion dynamics to mitigate harmful effects. 
       BRIEF SUMMARY OF THE INVENTION  
       [0004]    An aspect of the present invention relates to a perturbation device for use in a fuel nozzle of a combustor of a gas turbine system. The perturbation device can comprise a plurality of flexible plates including first and second flexible plates. Both the first and second flexible plates may be electromagnetic plates and respectively structured to receive first and second perturbation signals and generate corresponding first and second magnetic fluxes. The first and second flexible plates may be physically disposed relative to each other such that one or both of the first and second flexible plates vibrate due to an interaction between the first and second magnetic fluxes. The first flexible plate may be structured to receive an AC signal as the first perturbation signal and generate a corresponding AC magnetic flux as the first magnetic flux. 
         [0005]    Another aspect of the present invention relates to a control system for influencing dynamics in a combustor of a gas turbine system. The control system can comprise a plurality of perturbation devices for a plurality of fuel nozzles of the combustor, one or more pressure sensors, and a dynamics controller. Each fuel nozzle may be structured to deliver fluid to a combustion chamber of the combustor. The fluid can include fuel, oxidant, or mixture of fuel and oxidant. The one or more pressure sensors may be structured to measure pressure in the combustion chamber. The dynamics controller may be structured to analyze pressure dynamics based on the pressure measured by the one or more pressure sensors, and to output a plurality of perturbation signals to control the plurality of perturbation devices based on the analyzed pressure dynamics. The plurality of perturbation signals may include first and second perturbation signals, in which the first perturbation signal may be an AC signal. The plurality of perturbation devices may include a first perturbation device and the plurality of fuel nozzles may include a first fuel nozzle, in which the first perturbation device may be physically disposed within the first fuel nozzle upstream of the combustion chamber such that the fluid flows past the first perturbation device. The first perturbation device may comprise a plurality of flexible plates including first and second flexible plates, in which both may be electromagnetic plates. The first and second flexible plates may be physically disposed relative to each other such that one or both of the first and second flexible plates vibrate due to an interaction between the first and second magnetic fluxes. The dynamics controller may be structured to output the first and second perturbation signals to control vibration characteristics of the first flexible plate, the second flexible plate, or both based on the pressure dynamics. 
         [0006]    Another aspect of the present invention relates to a method for influencing dynamics in a combustor of a gas turbine system. The method may be relevant for a combustor that comprises a combustion chamber, a plurality of fuel nozzles including a first fuel nozzle, and a plurality of perturbation devices including a first perturbation device. Each of the plurality of fuel nozzles, including the first fuel nozzle, may be structured to deliver fluid to the combustion chamber. The fluid, being in a gas form preferably, can include fuel, oxidant, or mixture of fuel and oxidant. The first perturbation device may be physically disposed within the first fuel nozzle upstream of combustion chamber such that the fluid flows past the first perturbation device. The first perturbation device may comprise a plurality of flexible plates including first-first and first-second flexible plates, both of which may be electromagnetic plates. The first-first and first-second flexible plates may be respectively structured to receive the first-first and first-second perturbation signals and generate corresponding first-first and first-second magnetic fluxes. The first-first and first-second flexible plates may be physically disposed relative to each other such that one or both of the first-first and first-second flexible plates vibrate due to an interaction between the first-first and first-second magnetic fluxes. The method to influence the dynamics in such a combustor may comprise the steps of analyzing pressure dynamics based on measurements provided from one or more pressure sensors measuring pressure in the combustion chamber, and controlling attributes of the first-first and first-second perturbation signals provided to the first-first and first-second flexible plates to control vibration characteristics of the first perturbation device based on the analyzed pressure dynamics, in which the first perturbation may be AC signal. 
         [0007]    The invention will now be described in greater detail in connection with the drawings identified below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    These and other features of the present invention will be better understood through the following detailed description of example embodiments in conjunction with the accompanying drawings, in which: 
           [0009]      FIG. 1  illustrates a block diagram of an example gas turbine system according to an aspect of the present invention; 
           [0010]      FIG. 2  illustrates an example of a combustor according to an aspect of the present invention; 
           [0011]      FIG. 3  illustrates an example of a fuel nozzle with perturbation devices according to an aspect of the present invention; 
           [0012]      FIG. 4  illustrates an example of a perturbation device according to an aspect of the present invention; 
           [0013]      FIG. 5  illustrates a diagram of a control system to influence dynamics of a gas turbine system according to an aspect of the present invention; 
           [0014]      FIG. 6  illustrates a flow chart of an example method to influence dynamics of a gas turbine system according to an aspect of the present invention; and 
           [0015]      FIG. 7  illustrates a flow chart of an example process to control perturbation signals provided to perturbation devices according to an aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Novel method, system, and apparatus for actively controlling the combustor dynamics are described. In one aspect, the described method, system, and apparatus relate to actively controlling the combustion dynamics through using perturbation devices disposed in one or more fuel nozzles in which premixed fuel and oxidant (e.g., air) flow. Operating characteristics of the perturbation devices—frequencies, magnitudes (or amplitudes) and phases—may be controlled. Preferably, the operating characteristics of at least one perturbation device are controlled separately from all other perturbation devices. Most preferably, the operating characteristics of all perturbation devices are individually controlled. 
         [0017]      FIG. 1  illustrates an example of a gas turbine system  100 . As seen, the gas turbine system  100  may include a combustor  130  that generates high energy gases to drive a gas turbine  140  which can be used to drive a load  160  to perform useful work such as generating electricity. The turbine  140  may also include a shaft  150  operatively coupled to a compressor  110 , which compresses and provides compressed fluid containing oxidant, e.g., air, to the combustor  130 . The gas turbine system  100  may further include a fuel delivery unit  120  which delivers fuel to the combustor  130 . 
         [0018]    The gas turbine system  100  may include a system controller  170  that is structured to control the operation of the gas turbine system  100 . As seen, the system controller  170  may as inputs one or more sensor signals from sensors monitoring the system units (compressor  110 , fuel delivery unit  120 , combustor  130 , and turbine  140 ). While not shown, sensors can also be provided to monitor the load  160  and the shaft  150 . The system controller  170  can also receive operation inputs such as an instruction from an operator to start up, partial load operation, full load operation, shut down, and so on. Based on the received inputs, the system controller  170  may output control signals to the system units to control the system operation. The sensor signals from the system units  110 ,  120 ,  130  and  140  to the system controller  170  and the control signals from the system controller  170  to the units  110 ,  120 ,  130  and  140  are represented as dashed arrows. To minimize clutter in  FIG. 1 , the connections between system units  110 ,  120 ,  130  and  140  and the system controller  170  are omitted. 
         [0019]      FIG. 2  illustrates an example combustor  130 , which may include a plurality of fuel nozzles  220 , each of which may be structured to deliver fluid to the combustion chamber  230 . The fluid delivered by each fuel nozzle  220  may include fuel from the fuel delivery unit  120 , compressed oxidant such as air from the compressor  110 , or a mixture of fuel and oxidant. The fluid may be delivered in a gas form. The fuel/oxidant mixture is combusted within the combustion chamber  230 , and the resulting high energy gas to the turbine  140 . 
         [0020]      FIG. 3  illustrates an example fuel nozzle  220 . As seen, the fuel nozzle  220  may include one or more perturbation devices  310 . Preferably, perturbation devices  310  are disposed within the fuel nozzle  220  upstream of the combustion chamber  230  such that the fluid flows past the perturbation devices  310 . As an example, the perturbation devices  310  may be disposed at or in proximity to an end of the fuel nozzle  220  facing the combustion chamber  230 . In  FIG. 3 , the perturbation devices  310  are all illustrated to be disposed in a same longitudinal—along the direction of the fuel/oxidant/mixture flow—location within the fuel nozzle  200 . However, this is not a limitation. When there are multiple perturbation devices  310  within a particular fuel nozzle  220 , the locations of the perturbation devices  310  need not be the same between any two perturbation devices  310 . One or more perturbation devices can be attached to an inner surface  320  of the fuel nozzle  200 . 
         [0021]      FIG. 4  illustrates an example perturbation device  310 . The example perturbation device  220  may be a micro-electro-mechanical system (MEMS) device. As seen, the perturbation device  310  may include a plurality of flexible plates. For simplicity of explanation, only two flexible plates—first and second flexible plates  410 ,  420 —are illustrated. However, the number of flexible plates can be two or any number greater than two. In this figure, it is assumed that both the first and second flexible plates  410 ,  420  are electromagnetic plates. As an example, one or both electromagnetic plates can be made from thin flexible alloys and painted with high temperature ceramic which insulates the electric circuit from conducting metal. The first flexible plate  410  may receive a first perturbation signal and generate a first magnetic flux corresponding to the received first perturbation signal. Similarly, the second flexible plate  420  may receive a second perturbation signal and correspondingly generate a second magnetic flux. 
         [0022]    Note that when two magnetic fluxes interact, physical forces may be exerted on the flexible plates. Thus, in one aspect, the first and second flexible plates  410 ,  420  may be physically disposed relative to each other such that one or both of the first and second flexible plates  410 ,  420  vibrate due to the interaction between the first and second magnetic fluxes. For example, the first flexible plate  410  may be disposed in close proximity to the second flexible plate  420  so as to vibrate with respect to the second flexible plate  420  as indicated by the dashed lines in  FIG. 4 . 
         [0023]    In the upper right portion of this figure, the second flexible plate  420  is shown to be fixedly attached to an inner surface  320  of the fuel nozzle  220 . That is, only the first flexible plate  410  is shown to vibrate. However, this is not a limitation. In one alternative, the first flexible plate  410  may be fixed and the second flexible plate  420  may vibrate. In another alternative, both flexible plates  410 ,  420  may vibrate. Generally, of the plurality of flexible plates of a particular perturbation device  310 , at least one can be structured to vibrate. 
         [0024]    Also in the upper right portion, arrows indicate an example flow gradient of the fluid flowing within the fuel nozzle  220 . The vibrations can affect the gaseous fluid flowing past the perturbation device  310 . Then if the vibration characteristics of one or both of the first and second flexible plates  410 ,  420  can be controlled, the dynamics that occur within the combustor  130 , and in particular the dynamics occurring within the combustion chamber  230 , can be influenced. 
         [0025]    It is preferred that at least one flexible plate of the perturbation device  310  receives an AC signal as its perturbation signal. In  FIG. 4 , it is assumed that the first flexible plate  410  receives the AC signal as the first perturbation signal, and generates a corresponding AC magnetic flux as the first magnetic flux. Note that the characteristics of the first magnetic flux may significantly depend on the characteristics of the first perturbation signal including, among others, any one or more of an amplitude, frequency and phase. 
         [0026]    In one aspect, the second flexible plate  420  can receive a DC signal as the second perturbation signal, and generate a corresponding DC flux as the second magnetic flux. Note that the characteristics of the second magnetic flux may significantly depend on the characteristics of the second perturbation signal including, among others, one or both of magnitude and polarity. 
         [0027]    In another aspect, the second flexible plate  420  can also receive an AC signal as the second perturbation signal, and generate a corresponding AC flux as the second magnetic flux. For differentiation purposes, the AC signals received by the first and second flexible plates  410 ,  420  and the correspondingly generated magnetic fluxes will be referred to as first and second AC signals and first and second AC fluxes. The characteristics of the second AC flux may significantly depend on the characteristics of the second AC signal including, among others, any one or more of amplitude, frequency and phase. 
         [0028]    As indicated above, one or both of the first and the second flexible plates  410 ,  420  can vibrate due to the interaction between the first and second magnetic fluxes. The vibration characteristics may depend on the characteristics of the first and second magnetic fluxes. For example, when the second perturbation signal is a DC signal, the vibration characteristics may largely depend on the characteristics of the AC and DC fluxes and the interaction therebetween. When the second perturbation signal is a second AC signal, the vibration characteristics may largely depend on the characteristics of the first and second AC fluxes and the interaction therebetween. 
         [0029]    Note that the type of the perturbation signal a particular flexible plate receives need not bear any correlation with whether that particular flexible plate vibrates. For example, even though the first flexible plate  410  receives an AC signal as the first perturbation signal, the first flexible plate  410  can vibrate or be fixed. As another example, regardless of whether the second flexible plate  420  receives an AC or a DC signal as the second perturbation signal, the second flexible plate  420  can vibrate or be fixed. It is only necessary that among the plurality of flexible plates of the perturbation device  310 , at least one flexible plate vibrates. 
         [0030]      FIG. 5  illustrates a diagram of a control system  500  to influence the dynamics in a combustor  130 . From one perspective, the control system  500  may be viewed as being part of the gas turbine system  100 . As seen, the combustor  130  of the control system  500  may include a plurality of perturbation devices  310  for a plurality of fuel nozzles  220 . As indicated above, each fuel nozzle  220  may deliver fluid to the combustion chamber  230  of the combustor. The gaseous fluid delivered by each fuel nozzle  220  may include fuel, oxidant, or a mixture thereof. For simplicity, only the fuel nozzles  220  with at least one perturbation device  310  are illustrated. It should be noted however that the combustor  130  may include fuel nozzles that do not have any perturbation devices  310 . 
         [0031]    The control system  500  may also include one or more pressure sensors  510  structured to measure pressure in the combustor  130 , and particularly within the combustion chamber  230 . The control system  500  may further include a dynamics controller  570  to control the operation of influencing the dynamics of the combustor. The dynamics controller  570  in  FIG. 5  may be the same or a part of the system controller  170  in  FIG. 1 , or may be different altogether. 
         [0032]    The dynamics controller  570  may analyze the pressure dynamics based on the pressure measured by the one or more pressure sensors  510 . In this way, the pressure sensors  510  feedback to the dynamics controller  570 . Based on the analysis, the dynamics controller  570  may output a plurality of perturbation signals to control the plurality of perturbation devices  310 . It can be assumed that first and second perturbation signals are included among the perturbation signals output by the dynamics controller  570 . 
         [0033]    In  FIG. 5 , at least one fuel nozzle  220  includes at least one perturbation device  310 . For purposes of discussion, the one fuel nozzle  220  will be referred to as a first fuel nozzle  220  and the one perturbation device  310  will be referred to as a first perturbation device  310 . Then it can be said that the first perturbation device  310  is physically disposed within the first fuel nozzle  220  upstream of the combustion chamber  230  such that the fluid flows past the first perturbation device  310  within the first fuel nozzle  220 . 
         [0034]    The first perturbation device  310  may comprise a plurality of flexible plates. For discussion purposes, it is assumed that the first perturbation device  310  includes at least the first and second flexible plates  410 ,  420  as described with respect to  FIG. 4 . That is, it is assumed that the first and second flexible plates  410 ,  420  of the first perturbation device  310  are electromagnetic plates that generate magnetic fluxes corresponding to the received perturbation signals, and that the first and second flexible plates  410 ,  420  are physically disposed relative to each other such that one or both of the flexible plates  410 ,  420  vibrate due to an interaction between their respective magnetic fluxes. It is also assumed that the first and second flexible plates  410 ,  420  respectively receive the first and second perturbation signals from the dynamics controller  570 . It can then be said that the dynamics controller  570  is structured to output the first and second perturbation signals based on the pressure dynamics. The first and second perturbation signals can be output to control the vibration characteristics of one or both of the first and second flexible plates  410 ,  420  of the first perturbation device  310 . It is further assumed that the dynamics controller  570  outputs an AC signal as the first perturbation signal. 
         [0035]    Recall from above discussion that the vibration generated due to interactions between any two flexible plates can influence the dynamics of the combustor. Also recall that the vibration characteristics can largely depend on the magnetic fluxes generated by the flexible plates. The magnetic fluxes in turn are generated in accordance with the perturbation signals received by the flexible plates. 
         [0036]    Then between the first and second first and second flexible plates  410 ,  420  of the first perturbation device  310 , the dynamics controller  570  can control the vibration characteristics of the first second flexible plate  410 , of the second flexible plate  420 , or of both plates by controlling the characteristics of the first and second perturbation signals provided to the first and second flexible plates  420 . In this way, the dynamics controller  570  may influence the dynamics that occur within the combustor  130 . The degree of influence can increase as more and more perturbation devices  310 —of the same fuel nozzle  220  and/or of different fuel nozzles  220 —are controlled through controlling the plurality of perturbation signals. 
         [0037]    In one aspect, one of the first and second flexible plates  410 ,  420  may be stationary relative to the first fuel nozzle  220 . For example, one of the flexible plates may be fixedly attached to the inner surface  320  of the first fuel nozzle  220 . In this instance, the other flexible plate may vibrate, and the dynamics controller  570  may output first and second perturbation signals to control the vibration characteristics of the vibrating flexible plate. As another example, both of the flexible plates may vibrate. In this instance, the dynamics controller  570  may output first and second perturbation signals to control the vibration characteristics of both vibrating flexible plates. 
         [0038]    As indicated above, preferably the dynamics controller  570  outputs a first AC signal as the first perturbation signal. The dynamics controller  570  may output either a second AC or a DC signal as the second perturbation signal. In one aspect, the dynamics controller  570  may switch from outputting one of AC and DC signal to outputting the other from time to time. That is, the type of signal is not necessarily fixed for the second perturbation signal. 
         [0039]    It is also indicated above that the pressure sensors  510  provide feedback to the dynamics controller  570 . Thus, in an aspect, the dynamics controller  570  may continually analyze the pressure dynamics based on the pressure information from the pressure sensors  510  and adjust the characteristics of the first and second perturbation signals. That is, the dynamics controller  570  may adjust any one or more of the amplitude, frequency and phase of the first perturbation signal based on the pressure dynamics. If the second perturbation signal is a DC signal, the dynamics controller  570  may adjust any one or both of the magnitude and polarity of the second perturbation signal based on the pressure dynamics. If the second perturbation signal is the second AC signal, the dynamics controller  570  may adjust any one or more of the amplitude, frequency and phase of the second perturbation signal based on the pressure dynamics. 
         [0040]    It should be noted that all perturbation devices  310  need not be controlled in a same manner. In other words, between at least two perturbation devices  310 , the perturbation signals can be independently provided to the two perturbation devices  310 . Referring back to  FIG. 5 , assumed that in addition to the first perturbation devices  310 , there is also a second perturbation devices  310  disposed within a second fuel nozzle  220  upstream of the combustion chamber  230  such that the fluid flows past the second perturbation device  310 . Also assume that the second perturbation devices  310  includes at least third and fourth flexible plates  410 ,  420 , both of which are electromagnetic plates and generate third and fourth magnetic fluxes corresponding to the received perturbation signals. Further assume that the dynamics controller  570  can output third and fourth perturbation signals to the third and fourth flexible plates  410 ,  420 , in which the third perturbation signal is an AC signal. In one aspect, the dynamics controller  570  may output the third and fourth perturbation signals independent from the first and second perturbation signals. In other words, there is no requirement that common signals be provided to the first and second perturbation devices  310 . 
         [0041]    Then based on the feedback pressure dynamics, the dynamics controller  570  may adjust any one or more of an amplitude, a frequency and a phase of the third perturbation signal. Also, if the fourth perturbation signal is a DC signal, the dynamics controller  570  may adjust any one or more of the magnitude and polarity of the fourth perturbation signal based on the pressure dynamics. If the fourth perturbation signal is another AC signal, the dynamics controller  570  may adjust any one or more of the amplitude, frequency and phase of the fourth perturbation signal based on the pressure dynamics. 
         [0042]    Note that even when the first and second perturbation devices  310  are disposed within the same fuel nozzle  220 , the perturbation signals provided to the two perturbation devices  310  may still be independently provided. 
         [0043]      FIG. 6  illustrates a flow chart of an example method  600  to influence combustor dynamics. For discussion purposes, the gas turbine system  100  is assumed. The method  600  may be performed by the dynamics controller  570 . In step  610 , the pressure dynamics may be analyzed based on measurements provided from one or more pressure sensors that measure pressure in the combustion chamber  230 . Then in step  620 , based on the analyzed pressure dynamics, the attributes of the first and second perturbation signals provided to the first and second flexible plates ( 410 ,  420 ) may be controlled to control the vibration characteristics of the first perturbation device. The first perturbation signal is preferably an AC signal. 
         [0044]      FIG. 7  illustrates a flow chart of an example process to implement step  620 . In step  710 , it is determined whether a perturbation signal from the dynamics controller  570  is an AC or a DC signal. If the perturbation signal is an AC signal, then in step  720 , any one or more of the amplitude, frequency, and phase of the perturbation signal may be adjusted based on the analyzed pressure dynamics. If the perturbation signal is a DC signal, then in step  730 , any one or more of the magnitude and polarity of the perturbation signal may be adjusted based on the analyzed pressure dynamics. For example, since the first perturbation signal is an AC signal, the amplitude, frequency, and phase of the first perturbation signal may be adjusted. If the second perturbation signal is also an AC signal, then the amplitude, frequency, and phase of the second perturbation signal may be adjusted. If the second perturbation signal is a DC signal, then the magnitude and polarity thereof may be adjusted. 
         [0045]    When there are multiple perturbation devices  310 , the perturbation signals applied to each of the perturbation devices  310  may be controlled as well. That is, in step  620 , the third and fourth perturbation signals provided to the third and fourth flexible plates  410 ,  420  may be controlled based on the analyzed pressure dynamics to control the vibration characteristics of the second perturbation device  310 . In this instance, the third perturbation signal may be an AC signal, and thus, in steps  710  and  720 , any one or more of the amplitude, frequency and phase of the third perturbation signal may be adjusted. If the fourth perturbation signal is an AC signal, then the amplitude, frequency, and phase of the fourth perturbation signal may be adjusted. Otherwise, the magnitude and polarity of the fourth perturbation signal may be adjusted. 
         [0046]    There are significant flexibilities and benefits afforded by the disclose aspects. A non-exhaustive list of the flexibilities include:
       Multiple perturbation devices may be installed in a single fuel nozzle;   Each perturbation device can operate at different frequencies and magnitudes;   Within one fuel nozzle, several frequencies, amplitudes, and/or phase angles can be applied to achieve maximum benefits; and   Different fuel nozzles may operate their own perturbation devices in different operation modes to achieve maximum benefits.       
 
         [0051]    A non-exhaustive list of benefits include:
       eliminate dynamic walls in an operating window;   produce low turn downs;   enhance combustion;   reduce emissions;   mitigate variances caused by manufacturing tolerances; and   produce robust combustion flames.       
 
         [0058]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.