JP3809465B2 - Premixed combustor for gas turbine and fuel supply control device and method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a premix combustor for a gas turbine and an apparatus or method for controlling the fuel supply thereof.
[0002]
[Prior art]
In conventional combustors for gas turbines, diffusion combustion that provides stable combustion is used, so the adiabatic flame temperature has reached about 2000 ° C. Therefore, even when a fuel having a small nitrogen component, for example, natural gas, is used as fuel, it is inevitable that so-called thermal NOx is generated due to oxidation of nitrogen in the air.
[0003]
Since this thermal NOx can be reduced by lowering the flame temperature, instead of diffusion combustion, premixed combustion is performed in which fuel is mixed with combustion air in advance to form a lean mixed gas, which is burned at a relatively low temperature. Therefore, a technique for suppressing the generation of NOx has been attempted.
[0004]
However, when the fuel gas is diluted, there is a problem that the stable combustion range is narrowed, and it is difficult to ensure ignition and stable combustion. Also, in order to uniformly mix the fuel with the combustion air in advance, generally a relatively long premix flow path or a large premix space is required, and when the premix space is limited and uniform mixing cannot be performed, As the fuel concentration becomes a rich mixture, the production of NOx increases. In order to solve this problem, Japanese Patent Application Laid-Open No. Sho 63-217141 discloses that premixed combustion is stabilized by using both diffusion combustion and premixed combustion and controlling the flow rate of combustion air according to the load. Techniques for making them disclosed are disclosed.
[0005]
Furthermore, Japanese Patent Laid-Open Nos. H5-296412, H5-340273, and H8-128636 have an ignition gas injection hole at the center, and primary and secondary combustion premixes around it. A technology that can achieve low NOx by premixed combustion from ignition to stable combustion with a combustion device with a relatively simple structure by providing gas injection holes concentrically and controlling the fuel supply of these three systems. It is disclosed.
[0006]
[Problems to be solved by the invention]
However, with these configurations, for example, an instantaneous transition from maximum output operation to zero output is difficult due to imperfect flame stability, or during a sudden transition from zero output to maximum output operation. There is a problem that the premixed gas concentration in the premixed passage becomes too thick due to a sudden increase in fuel, causing a backfire and the like, and there is a problem that it cannot cope with a load fluctuation of about 1 second.
[0007]
Also, in order to control the amount of combustion air, a mechanism for varying the amount of air is required, and adding a variable air mechanism or the like immediately before the combustor complicates the structure of the combustor, ensuring reliability. There is a problem that miniaturization is difficult.
[0008]
In addition, in the case of a combustor having a plurality of fuel supply systems, there is a problem in that the combustion space is divided and air is distributed to each of them, so that there is less combustion air at the time of ignition and the ignition possible range is limited. In this way, if the possible ignition range is narrow and ignition does not occur, a large amount of premixed gas will flow into the combustor without forming a flame, and it may cause deflagration when ignited thereafter. In order to prevent ignition and ensure reliable ignition without ignition delay and subsequent smooth acceleration, it is necessary to perform advanced combustion control in the ignition system.
[0009]
Further, in the conventional premixed combustor, fluctuations in the intake conditions (pressure and temperature) are not taken into consideration, and it has been difficult to achieve low NOx and high combustion efficiency in a wide operating range. Furthermore, in order to cope with instantaneous deceleration and acceleration, the fuel supply control is complicated in the multi-stage fuel supply premixed combustor, and it is difficult to cope with it.
[0010]
Therefore, the present invention can achieve low NOx and high combustion efficiency in a wide operating range with a simple configuration, despite reliable ignition and start-up, and changes in intake conditions and sudden load fluctuations. It is an object of the present invention to provide a premixed combustor for a gas turbine, its fuel supply control device, and a control method.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, a premixed combustor for a gas turbine according to the present invention is formed around a substantially cylindrical combustion chamber, a diffusion fuel nozzle disposed in an upstream center portion of the combustion chamber, and a periphery thereof. A premixed combustor for a gas turbine comprising: an air passage communicating with the upstream end of the combustion chamber; and a premixed fuel nozzle for injecting fuel into the air passage, And an air flow path communicating with the upstream, a premix fuel nozzle is disposed upstream of the premix flow path, and the premix flow path is provided with a swirling device that imparts a swirl speed to the passing airflow. A first flow path that is disposed upstream and guides the swirling airflow from the outside toward the axial center; a second flow path that redirects the direction of the airflow that has passed through the first flow path in the axial direction; Decrease gradually and accelerate the airflow that passed through the second flow path in the axial direction Both the angle of the provisions with respect to the axial direction On the outside Spout into the combustion chamber An annular channel A third channel. The diffusion fuel nozzle is disposed at the axial center portion of the third flow path, and an air nozzle hole is disposed between the diffusion fuel nozzle and the annular flow path. It is characterized by.
[0012]
By configuring the air passage in this way, the fuel injected from the premixed fuel nozzle and the air introduced through the air flow path are efficiently mixed by the swirl device. In addition, the generated premixed gas is guided to the axial center direction and gradually accelerated to be turned in the axial direction, so that the premixed flow path having a relatively short space size is uniform both spatially and temporally. Premixed gas is supplied to the combustion chamber. Thereby, a lean premixed flame can be formed and generation of thermal NOx can be suppressed.
[0014]
The flame formed in the combustion chamber is turbulently diffused by the air injected from the air injection holes to promote combustion, and the space temperature distribution in the combustion chamber is kept uniform. In addition, since the diffusion fuel nozzle faces the combustion chamber, there is no time delay of fuel injection into the combustion chamber due to fuel switching when instantaneous deceleration or acceleration is performed. Does not cause overheating.
[0015]
It is more preferable that a plurality of the air nozzle holes are arranged and each air nozzle hole communicates with the air flow path.
[0016]
By arranging the plurality of air injection holes, the flame is separated from the diffusion fuel nozzle, the second flow path outlet, and the wall surface therebetween, thereby suppressing the temperature rise of the wall surface and the like. Furthermore, the cooling effect by the airflow which passes an air nozzle hole is also acquired. In addition, there is an effect that carbon or the like adhering to the end surface around the diffusion fuel nozzle can be blown off.
[0017]
In order to solve the above problems, a fuel supply control device for a gas turbine premixed combustor according to the present invention is a control device that controls the fuel supply of the gas turbine premixed combustor according to the present invention described above, Electromagnetic valves respectively disposed on fuel pipes for supplying fuel to each of the diffusion fuel nozzle and the premixed fuel nozzle, rotation speed variable means for changing the rotation speed of the gas turbine, and opening and closing of each of these solenoid valves Control is performed to switch between diffusion combustion and premixed combustion, and by changing the rotation speed of the gas turbine by means of variable rotation speed, the fuel equivalence ratio or the exhaust gas temperature is maintained constant and the control to respond to the required load And a section.
[0018]
According to this configuration, since diffusion combustion and premixed combustion are selectively used according to operating conditions, unlike the case where both are combined at the same time, it is not necessary to control the ratio of each, so it is relatively simple and low-cost fuel supply The system can be realized. For example, during normal load operation, operation is performed by premixed combustion, and during ignition, unstable combustion, or acceleration / deceleration, operation is performed by diffusion combustion. Low NOx and high combustion efficiency can be achieved.
[0019]
Furthermore, optimal lean combustion can be performed at all times regardless of the intake conditions of the gas turbine compressor, and if the exhaust gas temperature is maintained approximately constant, a power generation system or cogeneration system using a gas turbine can be used. The overall efficiency of the system can be kept relatively high.
[0020]
The fuel supply system further includes pressure feeding means for pressurizing and feeding the fuel, and the controller preferably adjusts the fuel flow rate by controlling the operation of the pressure feeding means. In this way, the driving load required at the time of fuel supply can be minimized.
[0021]
On the other hand, a fuel control method for a premixed combustor for a gas turbine according to the present invention is a fuel control method for a premixed combustor for a gas turbine described above, and supplies fuel to each of a diffusion fuel nozzle and a premixed fuel nozzle. A solenoid valve is arranged on each fuel pipe to switch between diffusion combustion and premixed combustion according to operating conditions by controlling the opening and closing thereof, and both the turbine speed and the exhaust gas temperature are predetermined. When the value is equal to or greater than the threshold value, the fuel supply to the diffusion fuel nozzle is stopped, and only the fuel supply to the premixed fuel nozzle is performed.
[0022]
According to this configuration, since diffusion combustion and premixed combustion are selectively used according to operating conditions, unlike the case where both are combined at the same time, it is not necessary to control the ratio of each, so it is relatively simple and low-cost fuel supply The system can be realized. When both the turbine speed and exhaust gas temperature are above the specified threshold, lean combustion can be continued stably, so operation is performed by premixed combustion, and operation is performed by diffusion combustion at the time of ignition or unstable combustion Thus, it is possible to achieve reliable ignition and startup, low NOx and high combustion efficiency over a wide operating range.
[0023]
Here, during sudden deceleration / acceleration, it is preferable to adjust the fuel flow rate by opening the diffusion fuel solenoid valve and switching the premixed fuel solenoid valve to the closed state. In this way, it is possible to prevent the combustion from becoming unstable due to switching, and it is possible to shift to the required operating state in the shortest time, and it is possible to continue stable combustion.
[0024]
During load operation with premixed combustion, it is possible to measure the compressor outlet pressure and calculate the corresponding fuel flow rate, and to respond to the required load by controlling the turbine speed so that the fuel equivalent ratio or exhaust gas temperature is constant. preferable.
[0025]
In this way, the optimum lean combustion can always be performed without being influenced by the intake conditions of the gas turbine compressor, and if the exhaust gas temperature is maintained substantially constant, the power generation system using the gas turbine and The overall efficiency of the cogeneration system can be maintained at a relatively high level.
[0026]
The solenoid valve arranged on the fuel pipe that supplies fuel to the diffusion fuel nozzle is configured by combining a shut-off valve and a flow rate adjustment valve. When starting the gas turbine, the flow rate adjustment valve is set to a predetermined opening degree. After the turbine rotation speed reaches the predetermined rotation speed, the shut-off valve is opened and fuel supply to the diffusion fuel nozzle is started, ignition is performed by the ignition device, and the turbine rotation speed, exhaust gas temperature, compressor outlet It is preferable to determine the success or failure of ignition from any increase in air pressure and the rate of change thereof.
[0027]
In this way, since the time delay until the fuel supply amount reaches a predetermined flow rate at the start can be reduced, reliable ignition can be performed. And since the success or failure of ignition can be determined reliably, reliable ignition and subsequent smooth acceleration can be realized, and troubles such as deflagration do not occur.
[0028]
It is preferable to adjust the fuel flow rate by controlling a pumping device arranged in the fuel supply system. In this way, the driving load required at the time of fuel supply can be minimized.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0030]
FIG. 1 is a longitudinal sectional view showing a preferred embodiment of a premixed combustor for a gas turbine according to the present invention, and FIG. 2 shows a diffusion fuel nozzle of the combustor and a portion of an air injection hole provided around the nozzle. It is the figure seen from the end surface side.
[0031]
The combustor 2 is a can-type combustor in which a substantially cylindrical inner cylinder 22 is disposed in a substantially cylindrical outer cylinder 21. In FIG. 1, air compressed by the compressor 1 described later is sent from the right end. It leads to the air flow passage 29 which is the space between the outer cylinder 21 and the inner cylinder 22, and leads from its end (right end) 29a to the annular premixing flow path 26 formed inside the end of the inner cylinder 22 together with the fuel. This is a reverse flow type combustor that reverses the flow, guides it into the inner cylinder 22 and burns it, then flows it out from the right end and supplies it to the turbine 3 described later. That is, the inner cylinder 22 is a combustion chamber liner that forms a combustion chamber. The inner cylinder 22 is provided with a dilution hole 30 for introducing combustion air to the inside and diluting the combustion gas.
[0032]
The fuel supply into the combustor 2 is arranged at substantially equal intervals on the circumference of the diffusion fuel nozzle 23 arranged at the axial center of the inner cylinder 22 and the air passage 29a on the upstream side of the premix channel 26. The plurality of premixed fuel nozzles 24 are used. Fuel supply to the nozzles 23 and 24 is performed by two systems of fuel supply pipes L1 and L2, which will be described later, connected to the left end in the outer cylinder 21.
[0033]
A plurality of swirl vanes 27 are arranged at the upstream end of the premix channel 26. The premixed fuel nozzle 24 described above is arranged on the upstream side closest to the swirl vane 27. The swirl vanes 27 are not arranged along the radial direction, but are arranged with a predetermined inclination with the swirl vanes 27. The annular premixing channel 26 is formed with a channel toward the axial center, the upstream introduction portion 26a where the swirl vanes 27 are arranged, the inlet side opens in the radial direction, and the outlet side in the axial direction. A curved portion 26b that is open and connected by a curved flow path, and a central axis that is common to the inner cylinder 22, and gradually decreases the cross-sectional area of the flow path from the upstream side to the downstream side along the axial direction. It is comprised from the pipe line part 26c. The opening 26d into the combustion chamber is an annular opening as shown in FIG. The premixed gas jetted from the annular opening 26d is jetted outward at an angle of about 15 ° to 30 ° with respect to the axial direction as indicated by an arrow A by the pipe 26c and burned. It flows into the chamber 22.
[0034]
A diffusion fuel nozzle 23 is arranged at the center inside the annular opening 26d, and its six injection holes 23a are arranged at equal intervals on the circumference centered on the axial center. Between the nozzle hole 23a and the opening 26, a plurality of nozzle holes 28a communicating with the passage 28 connected to the air passage 29a are arranged on two concentric circles. In the figure, six are arranged on the inner circumferential side and 12 are arranged on the outer circumferential side.
[0035]
Here, the inner diameter D1 and the outer diameter D2 of the opening 26d satisfy the relationship D2 / D1 ≦ 1.5, and D1 is 2 ≦ D3 / D1 with respect to the maximum inner diameter D3 of the combustion chamber, that is, the inner cylinder 22. It is preferable to satisfy the relationship of ≦ 4.
[0036]
FIG. 3 is a schematic view showing a power generation system using a gas turbine using the premixed combustor 2. The combustor 2 is disposed between the compressor 1 and the turbine 3, injects fuel into the air compressed by the compressor 1 and burns it, and rotates the turbine 3 with the obtained high-temperature gas to obtain an output. For example, a generator 4 is connected to the output shaft of the turbine 3 (disposed on the compressor 1 side in the figure). The generator 4 is connected to an inverter 5 that controls the rotational speed.
[0037]
The above-described fuel supply lines L1 and L2 of the combustor 2 are a part of the fuel supply system 6, and on the main pipe L0 connected to the city gas supply pipe, a gas compressor 61, a shut-off valve 62, A fuel adjustment valve 63 is arranged, and is branched into lines L1 and L2 on the downstream side thereof. Further, a line L3 branched from a line L0 extending to the fuel adjustment valve 63 downstream from the shutoff valve 62 is provided, and this line L3 is connected to the line L1 immediately before the combustor 2. A shutoff valve 65 is disposed in the line L1, a shutoff valve 64 is disposed in the line L2, and an orifice 66 and a shutoff valve 67 are disposed in the line L3.
[0038]
An engine control unit (hereinafter referred to as ECU) 7 that controls the operation of the system includes a pressure gauge 71 that measures the outlet pressure of the compressor 1, a combustor inlet air thermometer 74 that measures the outlet temperature, a turbine In addition to the output of the thermometer 72 that measures the exhaust gas temperature at the 3 outlets, the state signal of the inverter 5 is input, and in addition to the exciter 73 that sparks the spark plug, the valves 62 to 65 and 67 and the gas compressor 61 Control the operation of
[0039]
Next, the operation of the combustor 2 will be described. First, the startup operation will be described with reference to FIG. FIG. 4 is a time chart showing the control at the start. Hereinafter, unless otherwise specified, control of the control is performed by the ECU 7.
[0040]
Time t ₀ , The flow regulating valve 63 is opened to a predetermined opening a with the shut-off valves 62, 64, 65, 67 closed, and the generator 4 connected to the compressor 1 and the turbine 3 is driven as a starting motor. The compressor 1 is started by rotating and the air purge is performed in the turbine 3 and the exhaust duct. At the same time, the gas compressor 61 for supplying fuel is driven. At this time, the shut-off valves 62, 64, 65, and 67 remain closed, and the city gas that is fuel is not supplied to the combustor 2.
[0041]
Then time t ₁ The spark plug 25 is intermittently ignited by driving the exciter 73 at or slightly before the point of time.
[0042]
Time t when the supply pressure of the gas compressor 61 reaches the specified pressure and the specified air purge time has elapsed. ₂ At this point, the shut-off valves 62, 65, 67 are opened, and fuel supply to the diffusion fuel nozzle 23 via the line L1 is started. At this time, the shutoff valve 64 disposed in the line L2 connected to the premixed fuel nozzle 24 remains closed, and no fuel is supplied to the premixed fuel nozzle 24. The amount of fuel supplied to the diffusion fuel nozzle 23 is controlled by adjusting the opening of the flow rate adjusting valve 63 while controlling the outlet pressure of the gas compressor 61 measured by the pressure gauge 68 to be constant. . The fuel supply amount may be adjusted by making the rotational speed of the gas compressor 61 variable instead of using the flow rate adjusting valve 63.
[0043]
The fuel supplied from the nozzle hole 23a at the tip of the diffusion fuel nozzle 23 is caused by the air flow supplied from the nozzle hole 28a opened on the wall surface located on the axial center side from the opening 26d of the premixing channel 26. It is turbulently diffused and diffused to the periphery of the spark plug 25 to ignite with a spark ignited from the spark plug 25. A relatively small flame generated by the ignition from the spark plug 25 propagates toward the diffusion fuel injection hole 23a, and a swirling air flow ejected in an angular direction of 15 ° to 30 ° from the opening 26d generates a combustion chamber. By being taken in and expanded into the circulating vortex space formed in 22, a stable and steady diffusion flame can be formed. Thereby, a diffusion combustion flame is formed in the inner cylinder 22.
[0044]
Since the diffusion combustion flame formed in this manner is turbulently diffused by the air flow ejected from the nozzle hole 28a, the diffusion combustion flame is separated from the inner wall surface of the inner cylinder 22 and the inner wall surface 22b located on the axial center side from the opening 26d. It is possible to suppress thermal damage to the wall surface 22d and the inner cylinder 22 or carbon adhesion. Further, combustion can be promoted by this turbulent flow effect, and the spatial temperature distribution in the combustion chamber can be made uniform.
[0045]
By the diffusion flame formed in this way, the high-temperature gas obtained in the combustion chamber 22 is guided to the turbine 3 and the turbine 3 is driven, whereby the rotational speed of the turbine 3 increases. By detecting the increase in the rotational speed, it is possible to reliably determine whether the diffusion fuel has been ignited. In addition, when ignition is successful, the temperature of the exhaust gas measured by the thermometer 72 and the outlet pressure of the compressor 1 measured by the pressure gauge 71 rise, and are supplied for driving the motor of the generator 4. Since the power to be generated decreases and eventually the load of power generation increases, the success or failure of ignition may be determined based on these changes.
[0046]
If it is determined that ignition is successful (time t _Three ), The amount of fuel supplied to the diffusion fuel nozzle 23 is increased by gradually increasing the opening degree of the flow rate adjusting valve 63. Thus, reliable ignition and smooth start-up can be performed by the diffusion combustion flame.
[0047]
Next, the operation during load operation will be described. FIG. 5 is a graph for explaining a combustion control state with respect to a power generation output when a 50 kW class gas turbine system is configured as the gas turbine power generation system of FIG. 3. After the ignition, the shutoff valves 65 and 67 are both opened and the shutoff valve 64 is controlled to close and the fuel is supplied only from the diffusion fuel nozzle 23 to perform the diffusion combustion operation with the pilot fuel.
[0048]
After reaching the predetermined rotation speed, the shutoff valve 65 is closed and the shutoff valve 64 is opened. The fuel injected from the premix fuel nozzle 24 is guided to the introduction portion 26 a of the premix flow path 26 together with the combustion air sent from the compressor 1 through the passage 29, and swirled by the swirl vanes 27. After being mixed well, the flow direction is turned in the axial direction by the curved portion 26b, and then accelerated by passing through the tubular portion 26c to burn the inner cylinder 22 from the annular opening 26d. It is injected into the room. In this way, a uniform air-fuel mixture is formed in the pre-mixing flow path 26, so that the temporal and spatial distribution of the pre-air mixture injected into the combustion chamber can be made uniform. Further, by adopting such a premixing channel configuration, the object can be achieved with a relatively short space dimension, and the combustor itself can be made compact. The injected premixed gas is ignited by the diffusion flame formed inside thereof, thereby forming a premixed flame. Thus, the pilot-assisted premixed combustion operation is performed by simultaneously forming the premixed flame and the diffusion flame.
[0049]
Further, after the rotational speed increases and the output reaches a predetermined output, the shutoff valve 67 is also closed and the fuel supply to the diffusion fuel nozzle 23 is completely stopped. As a result, complete premixed combustion using only the premixed gas that has passed through the premixed flow path 26 is performed. The formed premixed flame is also turbulently diffused by the air flow ejected from the nozzle hole 28a as in the case of the diffusion flame, and therefore is positioned closer to the axial center than the inner wall surface of the inner cylinder 22 and the opening 26d. It can be separated from the inner wall surface 22b, and thermal damage to the wall surface 22e and the inner cylinder 22 can be suppressed. Further, combustion can be promoted by this turbulent flow effect, and the spatial temperature distribution in the combustion chamber can be made uniform. Moreover, the cooling effect of the inner wall surface 22b by the air which passes the air flow path 29 can also be expected.
[0050]
Here, as described above, when the relationship of D2 / D1 ≦ 1.5 is satisfied, the premixed flame formed inside the opening 26d and the premixed flame formed outside the opening 26d are There is no complete separation in space, and the stability of the flame is maintained and enhanced, so that complete combustion can be performed reliably.
[0051]
Further, when the relationship of D3 / D1 ≦ 4 is satisfied, the inner and outer flames are not significantly separated when the premixed gas supplied from the opening 26d burns in the combustion chamber, and combustion Uniform combustion is possible without wasting space, and the spatial temperature distribution in the combustion chamber can be made uniform. Further, if the relationship of 2 ≦ D3 / D1 is satisfied, the flame does not extend abnormally long in the axial direction, so there is no need to make the combustion chamber elongated, and the combustion chamber liner 22 can be made compact. The effect of suppressing the temperature rise is obtained.
[0052]
During combustion control, the number of revolutions of the generator 4 connected to the compressor 1 is controlled by the inverter 5 so that the optimum supply air amount for the injected fuel is adjusted and the equivalence ratio is kept constant. The combustion temperature can be controlled to be constant.
[0053]
FIG. 6 shows the NOx concentration in the exhaust gas, CO 2 when the inverter 5 is operated with the rotational speed of the generator 4 controlled so that the exhaust gas temperature (corresponding to the combustion temperature) measured by the thermometer 72 is constant. It is a graph showing a density | concentration. In this example, diffusion combustion is used up to an output of 20 kW, pilot premixed combustion is used up to 20 to 42 kW, and complete premixed combustion is used up to 42 kW or more.
[0054]
In the complete premixed combustion region, the NOx concentration is less than 6 ppm, the CO concentration is less than 5 ppm, and the combustion efficiency is more than 99.99% in terms of oxygen concentration of 16%. In the pilot premixed combustion region, the NOx concentration is less than 8 ppm, the CO concentration is less than 90 ppm, and the combustion efficiency is over 99.5%. In the diffusion combustion region, the NOx concentration is less than 75 ppm, the CO concentration is less than 250 ppm, and the combustion efficiency is over 98%. The power generation efficiency is 20 to 28% in the pilot premixed combustion and fully premixed combustion regions of 20 kW to 50 kW, maintaining relatively high power generation efficiency even in partial load operation, and operating at low NOx, low CO, and high combustion efficiency. Was able to do.
[0055]
Here, an example of switching between pilot premixed combustion and complete premixed combustion at about 42 kW has been described. However, the entire high-load region may be operated with pilot premixed combustion or with complete premixed combustion. It may be performed at a low load, for example, 30 kW, or at a higher load.
[0056]
If you want to instantly decelerate from a maximum output of 50 kW to an output of 0 kW, or if you want to accelerate from an output of 0 kW to a maximum output of 50 kW in less than 1 second, open the diffusion fuel solenoid valves 65 and 67. At the same time, by closing the solenoid valve 64 and switching to diffusion combustion instantaneously, a stable diffusion flame can be formed and the transition can be made smoothly and in the shortest time.
[0057]
Next, fuel supply control according to the present invention will be described. FIG. 7 is a longitudinal sectional view showing an example of a premix combustor for gas turbine to which fuel supply control of the premix combustor for gas turbine according to the present invention is applied. FIG. It is the figure which looked at from the end surface side.
[0058]
This combustor 2a differs from the combustor 2 shown in FIG. 1 only in the structure of the axial center portion of the combustor. Therefore, description of common parts is omitted, and only different parts are described.
[0059]
In the combustor 2a, the spark plug 25 is disposed in a hole 22a provided at the center of the upstream side of the combustion chamber cylinder 22 (pointing to the left side in the figure). Six injection holes 23a of the diffusion fuel nozzle 23 connected to the fuel supply pipe L1 are arranged on the circumference centering on the hole 22a.
[0060]
FIG. 9 is a schematic view showing a power generation system using a gas turbine using the premixed combustor 2a. The main configuration is the same as that of the gas turbine power generation system shown in FIG. 3, and is different from the system of FIG. 3 in that the line L3 is not provided.
[0061]
First, fuel supply control at startup will be described with reference to FIG. FIG. 10 is a time chart showing the control at the start. This control is also performed by the ECU 7.
[0062]
Time t ₀ , The flow regulating valve 63 is opened to a predetermined opening degree a with the shut-off valve 62 closed, and the compressor 1 is started by driving and rotating the generator 4 as a starter motor. And air purge the exhaust duct. At the same time, the gas compressor 61 for supplying fuel is driven. At this time, the shutoff valves 62, 64, 65 remain closed, and the city gas as fuel is not supplied to the combustor 2.
[0063]
Then time t ₁ The spark plug 42 is intermittently ignited by driving the exciter 73 at or shortly before.
[0064]
Time t when the supply pressure of the gas compressor 61 reaches the specified pressure and the specified air purge time has elapsed. ₂ At this time, the shutoff valve 65 on the line L1 and the shutoff valve 62 upstream thereof are opened, and the fuel supply to the diffusion fuel nozzle 23 is started. Here, the fuel supply amount is controlled by adjusting the opening degree of the flow rate adjustment valve 63. The fuel supplied from the nozzle hole 23 circulates to the tip of the spark plug 25 by the circulating flow formed in the combustion chamber, and is ignited by the spark ignited from the spark plug 25, so that the diffusion combustion flame is generated in the inner cylinder 22. Formed.
[0065]
By driving the turbine 3 by guiding the high-temperature gas obtained in the combustion chamber 22 to the turbine 3 by the diffusion flame formed in this way, the rotational speed of the turbine 3 increases. By detecting the increase in the rotational speed, it is possible to reliably determine whether the diffusion fuel has been ignited. In addition, when ignition is successful, the temperature of the exhaust gas measured by the thermometer 72 and the outlet pressure of the compressor 1 measured by the pressure gauge 71 rise, and are supplied for driving the motor of the generator 4. Since the power to be generated decreases and eventually the load of power generation increases, the success or failure of ignition may be determined based on these changes.
[0066]
If it is determined that ignition is successful (time t _Three ), The amount of fuel supplied to the diffusion fuel nozzle 23 is increased by gradually increasing the opening degree of the flow rate adjusting valve 63. Thus, reliable ignition and smooth start-up can be performed by the diffusion combustion flame.
[0067]
Next, the operation during load operation will be described. When the rotational speed of the turbine 3 becomes equal to or higher than the predetermined rotational speed and the exhaust gas temperature measured by the thermometer 72 reaches a predetermined temperature (for example, 600 ° C.) or higher, the shutoff valve 64 on the line L2 is opened. Fuel supply to the premix fuel nozzle 24 is started.
[0068]
The fuel injected from the premixed fuel nozzle 24 is mixed with the combustion air sent from the compressor 1 through the passage 29 when passing through the premixed flow path 26, and the inner cylinder 22 is connected from the annular outlet 26 a. Are injected into the combustion chamber and ignited by a diffusion flame formed on the inside thereof to form a premixed flame.
[0069]
When the rotation speed of the turbine 3 and the exhaust gas temperature are stable and the ignition of the premixed flame is confirmed, the fuel supply from the diffusion fuel nozzle 23 is stopped by closing the shutoff valve 65 on the line L1 after a predetermined time, and diffusion combustion To switch to premixed combustion.
[0070]
Thus, at the time of switching from diffusion combustion to premixed combustion, both shut-off valves 64 and 65 are temporarily opened to provide an overlap time for supplying fuel from both the diffusion fuel nozzle 23 and the premixed fuel nozzle 24. Thus, the transition (switching) from diffusion combustion to premixed combustion can be performed reliably.
[0071]
After shifting to the premixed combustion, the fuel supply amount is adjusted by the rotation speed of the gas compressor 61 and the flow rate adjusting valve 63 so that the exhaust gas temperature is maintained at a predetermined temperature (for example, 650 ° C.), and the pressure gauge 71 The rotational speed of the generator 4 is controlled by the inverter 5 on the basis of the outlet pressure of the compressor 1 measured in the above, so that the rotational speed of the compressor 1 directly connected to the generator 4 is changed to the injected fuel. Adjust to the optimal supply air volume. Thereby, load operation can be performed so that a desired output can be obtained while keeping the equivalence ratio constant.
[0072]
Since the equivalence ratio is kept almost constant in this way, stable combustion at a lean air-fuel ratio can be performed over a wide operating load range, so high-efficiency combustion with less than 10 ppm (several ppm) low NOx and low CO is possible. Achieved. Further, by adjusting the fuel supply amount using the rotation speed control of the gas compressor 61 and the flow rate adjusting valve 63, the driving load of the gas compressor 61 can be minimized. Here, the adjustment of the fuel supply amount may be performed only by either the rotation speed control of the gas compressor 61 or the opening degree adjustment of the flow rate adjustment valve 63.
[0073]
On the other hand, when the turbine outlet gas temperature falls below a specified temperature level (for example, 600 ° C.), this time, the shutoff valve 65 on the line L1 is opened, fuel is injected from the diffusion fuel nozzle 23, and the premixed flame is injected. A diffusion flame is formed inside. When the rotational speed of the turbine 3 and the exhaust gas temperature are stabilized and the formation of the diffusion flame is confirmed, the supply of the premixed fuel is stopped by closing the shutoff valve 64 on the line L2 after a predetermined time, and the diffusion combustion Finish switching to.
[0074]
In this way, when switching from premixed combustion to diffusion combustion, the transition can be performed smoothly and reliably by switching instantaneously at the same time or by providing an overlap time. Furthermore, in premixed combustion, in a region where combustion is likely to be unstable, diffusion combustion is performed, so that non-combustible fuel is not discharged and CO concentration does not increase, so that stable operation can be performed.
[0075]
The fuel supply control device and control method for a gas turbine premixed combustor according to the present invention are not applied only to the gas turbine premixed combustor as shown in FIGS. And can be applied to various premixed combustors capable of switching premixed combustion.
[0076]
FIG. 11 is a longitudinal sectional view showing another gas turbine premixed combustor 2b to which the present invention can be applied, and FIG. 12 is a view of an upstream end in the combustor as viewed from the downstream side.
[0077]
In this combustor 2b, like the combustor 2 shown in FIGS. 1 and 2, a spark plug 25 is attached to the side of the inner cylinder 22 of the combustor 2b. By arranging the spark plug 25 on the side, the structure in the vicinity of the diffusion fuel nozzle 23 can be simplified, and the manufacturing can be facilitated.
[0078]
The fuel supply control according to the present invention can also be suitably applied to this combustor 2b.
[0079]
Instead of the gas compressor 61 and the fuel adjustment valve 63 constituting part of the fuel supply system 6, the fuel flow rate may be controlled by, for example, a gas compressor having a rotation speed variable mechanism. In the above description, city gas is used as the fuel. However, for example, other gaseous fuels such as LNG, LPG, biomass fuel, or hydrogen, or liquid fuel can be used in the same manner.
[0080]
【The invention's effect】
As described above, according to the premixed combustor for a gas turbine of the present invention, uniform premixed gas is burned spatially and temporally in a premixed flow path having an axially symmetric configuration and a relatively short space size. Since it can be supplied to the chamber, the overall size of the combustor can be made compact, and a lean premixed flame can be formed to suppress the generation of thermal NOx.
[0081]
Further, according to the fuel control method according to the present invention, since the diffusion combustion and the premixed combustion are switched in accordance with the operation conditions in the same combustor, the operation can always be performed under the optimum conditions, and NOx, CO Emissions can be reduced. Further, since switching can be performed only by electromagnetic valve control, it is possible to cope with instantaneous deceleration and acceleration, and the structure of the fuel supply system can be simplified. Therefore, reliable ignition and start-up are possible.
[0082]
Furthermore, by adjusting the rotational speed of the gas turbine, the air flow rate is adjusted, and the fuel flow rate is adjusted to maintain combustion at a constant equivalence ratio or combustion temperature regardless of the load. Stable combustion with low NOx is possible.
[Brief description of the drawings]
FIG. 1 is a view showing an example of a premixed combustor for a gas turbine according to the present invention.
FIG. 2 is a view showing a combustion chamber inlet portion in FIG. 1;
FIG. 3 is a schematic view of a co-generation system using the premixed combustor of FIG. 1;
4 is a flowchart for explaining an operation at the time of startup of the system of FIG. 3;
FIG. 5 is a graph for explaining a combustion control state with respect to a power generation output in the system of FIG. 3;
6 is a graph showing NOx concentration and CO concentration in exhaust gas in the system of FIG.
FIG. 7 is a diagram showing an example of a premixed combustor for a gas turbine to which a fuel supply control device according to the present invention is applied.
8 is a view showing a combustion chamber inlet portion in FIG. 7; FIG.
FIG. 9 is a schematic view of a cogeneration system using a gas turbine to which a fuel supply control device according to the present invention is applied.
10 is a time chart when the system of FIG. 9 is started up.
FIG. 11 is a view showing another example of a premixed combustor for a gas turbine to which a fuel supply control device according to the present invention is applied.
12 is a view showing a combustion chamber inlet portion in FIG. 11. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Compressor, 2 ... Premix combustor, 3 ... Turbine, 4 ... Generator, 5 ... Inverter, 6 ... Fuel supply system, 7 ... ECU, 21 ... Outer cylinder, 22 ... Inner cylinder (combustion chamber liner), DESCRIPTION OF SYMBOLS 23 ... Diffusion fuel nozzle, 24 ... Premix fuel nozzle, 25 ... Spark plug, 26 ... Premix flow path, 29 ... Air flow path, 61 ... Gas compressor, 62, 64, 65 ... Shut-off valve, 63 ... Flow control valve .

Claims (10)

A substantially cylindrical combustion chamber; a diffusion fuel nozzle disposed in an upstream central portion of the combustion chamber; an air passage formed therearound and communicating with an upstream end of the combustion chamber; and in the air passage A premixed combustor for a gas turbine comprising a premixed fuel nozzle for injecting fuel,
The air passage is composed of a premixing flow path and an air flow path communicating with the upstream, the premixing fuel nozzle is disposed upstream of the premixing flow path, and the premixing flow path includes: A swirling device that imparts a swirling speed to the passing airflow is disposed on the upstream side, a first flow path that guides the swirling airflow from the outside toward the axial center, and the direction of the airflow that has passed through the first flow path is the axial direction A second flow path that is turned to the outside, and gradually reduces the flow path area to accelerate the airflow that has passed through the second flow path in the axial direction and toward the outside at a specified angle with respect to the axial direction. A third flow path that is an annular flow path that is ejected to the center, and the diffusion fuel nozzle is disposed at an axial center portion of the third flow path, and the diffusion fuel nozzle and the annular flow path Antofagasta, characterized in that the air Kibuki holes are arranged between the Premixed combustors bottle. The premixed combustor for a gas turbine according to claim 1, wherein the specified angle is 15 ° to 30 ° . The premixed combustor for a gas turbine according to claim 1, wherein a plurality of the air injection holes are arranged, and each air injection hole communicates with the air flow path. A control device for controlling fuel supply of the premixed combustor for a gas turbine according to any one of claims 1 to 3 ,
Solenoid valves respectively disposed on fuel pipes for supplying fuel to each of the diffusion fuel nozzle and the premix fuel nozzle;
A rotation speed variable means for changing the rotation speed of the gas turbine;
Switching between diffusion combustion and premixed combustion is controlled by controlling the opening and closing of each solenoid valve, and the fuel equivalence ratio or exhaust gas temperature is kept constant by changing the rotation speed of the gas turbine by the rotation speed variable means. While controlling the required load,
A fuel supply control device for a premixed combustor for a gas turbine. The fuel supply system is further provided with a pumping means for pressurizing and feeding the fuel,
The fuel supply control device for a premixed combustor for a gas turbine according to claim 4, wherein the control unit adjusts a fuel flow rate by controlling an operation of the pumping means. In the fuel control method of the premixed combustor for gas turbines in any one of Claims 1-3 ,
Solenoid valves are respectively arranged on fuel pipes for supplying fuel to each of the diffusion fuel nozzle and the premixed fuel nozzle, and by controlling the opening and closing thereof, diffusion combustion and premixed combustion are performed according to operating conditions. As well as switching
When both the turbine speed and the exhaust gas temperature are equal to or higher than a predetermined threshold, the fuel supply to the diffusion fuel nozzle is stopped and only the fuel supply to the premix fuel nozzle is performed. Fuel control method.   7. The fuel control method for a premixed combustor for a gas turbine according to claim 6, wherein the fuel flow rate is adjusted by opening the electromagnetic valve of the diffusion fuel during sudden deceleration / acceleration and switching the electromagnetic valve of the premixed fuel closed. .   During load operation with premixed combustion, the required load is calculated by measuring the compressor outlet pressure or combustion chamber inlet temperature, calculating the corresponding fuel flow rate, and controlling the turbine speed so that the fuel equivalent ratio or exhaust gas temperature is constant. The fuel control method for a premixed combustor for a gas turbine according to any one of claims 6 and 7, wherein the fuel control method corresponds to.   The solenoid valve arranged on the fuel pipe that supplies fuel to the diffusion fuel nozzle is configured by combining a shut-off valve and a flow rate adjustment valve. When starting the gas turbine, the flow rate adjustment valve is set to a predetermined opening degree. After the turbine rotation speed reaches a predetermined rotation speed, the shut-off valve is opened and fuel supply to the diffusion fuel nozzle is started, ignition is performed by an ignition device, and the turbine rotation speed, exhaust gas temperature, compressor The fuel control method for a premixed combustor for a gas turbine according to any one of claims 6 to 8, wherein the success or failure of ignition is determined from any increase in outlet air pressure and the rate of change thereof.   The fuel control method for a premixed combustor for a gas turbine according to any one of claims 6 to 9, wherein the fuel flow rate is adjusted by controlling a pumping device disposed in the fuel supply system.

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