JPH0752015B2 - gas turbine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine, and more particularly to a gas turbine including means for controlling a flow rate of air supplied to a combustor.

[Conventional technology]

In gas turbine combustors, recently, a two-stage combustion system or other multi-stage combustors are being adopted for the purpose of achieving low NOx. In all of these, it is necessary to adjust the amount of combustion air according to the load of the gas turbine. For example, in Japanese Examined Patent Publication No. 53-43, a baffle is provided in the air passage between the primary combustion zone and the secondary combustion zone to reduce the primary air for combustion and increase the secondary air amount during low load operation. Therefore, it is disclosed that the primary combustion zone is prevented from being excessively leaned, and at the time of high load operation, the baffles are adjusted so that the respective air flows without resistance, and the combustor that suppresses the generation of NOx is disclosed. . However, there are problems of combustion performance and emission characteristics at the time of transition from the first-stage combustion to the second-stage combustion, and it is difficult to maintain good combustion performance before and after fuel switching by the known air control method.

[Problems to be solved by the invention]

In the above prior art, since the air control at the time of transition from the first-stage combustion to the second-stage combustion is performed only by baffle, the primary and secondary air amount control cannot be normally performed, and the combustion performance before and after the fuel switching is good. There was a problem keeping it.

An object of the present invention is to provide a gas turbine that can maintain good combustion performance during transition from diffusion combustion that is one-stage combustion to premixed combustion that is two-stage combustion, and that can maintain good emission characteristics. To provide.

[Means for solving problems]

In the gas turbine of the present invention, the fuel and air are supplied to the combustion chamber for diffusion combustion, and the fuel and air are premixed, and the mixture is supplied to the combustion chamber to perform premixed combustion. It is provided with a combustor having premixed combustion means for performing the operation, and a compressor for supplying air used in the combustor. Then, first air flow rate control means for extracting compressed air from the intermediate stage of the compressor and controlling the flow rate of the air supplied to the combustor; Second air flow rate control means for controlling the flow rate of air supplied to the mixed combustion means, and when the load of the gas turbine is in the vicinity of the load for starting the premixed combustion by the premixed combustion means, The second air flow rate control unit reduces the air flow rate supplied to the premixed combustion unit, and the first air flow rate control unit reduces the air flow rate supplied to the combustor. To do.

[Action]

In a gas turbine combustor of a two-stage combustion system comprising means for performing diffusion combustion and means for performing premixed combustion, the total amount of combustion air flowing into the combustor is adjusted by increasing or decreasing the amount of bleed air from the compressor, Further, the amount of air flowing into the second stage combustion section of the combustor is partially controlled by a mechanical movable device. In this way, in the two-stage combustion type gas turbine combustor, the amount of combustion air can be fully adjusted and partially adjusted, so that the combustion ratio within the combustor is within an appropriate range under all conditions. Can be controlled. In particular, it has the effect of maintaining good combustion performance and emission characteristics before and after the transition from first-stage combustion to second-stage combustion.

〔Example〕

FIG. 1 shows an embodiment of the present invention. In this figure, the gas turbine is composed of a compressor 1, a turbine 2, a combustor 3, and the like. The air 1a compressed by the compressor 1 is guided to the combustor 3 through the inside of the casing 4. The combustor 3 has an outer cylinder 5
A cover 10 having a primary fuel nozzle 9 for supplying the primary fuel 8 to the inner cylinders a and 5b and the front combustion chamber 7 is attached.
The inner cylinder 6 is formed of a front combustion chamber 7 and a rear combustion chamber 11 having a larger diameter than this. In addition, the front combustion chamber 7 and the rear combustion chamber
A premixed combustion section for performing premixed combustion is provided at a connecting section 12 with 11. This premix combustion section has an air supply hole
A secondary fuel 14 is jetted out here, premixed with secondary air, and supplied to the rear combustion chamber 11 to generate a secondary combustion flame.
Configured to form fifteen. Ignition of the primary fuel 8 ejected from the primary fuel nozzle 9 is performed by a spark plug (not shown) to form a primary combustion flame 16. On the other hand, the ignition of the secondary fuel 14 is achieved by the transfer from the primary combustion flame 16. Here, the configuration of the combustor 3 will be further described with reference to FIG. In the figure, the primary fuel 8 is jetted into the front combustion chamber 7 by the primary fuel nozzle 9 as described above, but the jetting portions 9a are plural so that the fuel is jetted in a dispersed manner. There is. Similarly, the secondary fuel 14 passes through the secondary fuel nozzle 17 that is sandwiched and fixed by the outer cylinders 5a and 5b, and is ejected from the tips of a plurality of protruding ejection portions 18. The primary fuel 8 is mixed with a large amount of combustion air 19 that has been ejected into the front combustion chamber 7 and has flowed through the casing 4 to diffuse, burn, and burn a lean low-temperature primary combustion flame 16 effective for reducing NOx. Form. The secondary combustion section mixes the secondary fuel ejected from the ejection section 18 and the combustion air 21 flowing from the opening section 20 downstream of the ejection section 18 and supplies the mixture into the rear combustion chamber 11. The opening 20 has a movable piece so as to cover it.
22 is provided, and is moved around the opening 20 by means of a link mechanism 23 or the like, whereby the flow rate of the combustion air 21 flowing in from the opening 20 can be adjusted. The flow rate of the combustion air 21 is adjusted according to the secondary fuel flow rate so that the combustion ratio (fuel flow rate / air flow rate) of the air-fuel mixture described above falls within an appropriate range. further,
In the low load operation range where the secondary fuel is not ejected, the combustion air that does not flow into the rear combustion chamber 11 but flows into the front combustion chamber 7
The flow rate of 19 is decreased by moving a large amount of combustion air 21 through the movement of the movable piece 22 through the opening 20 and bypassing it, and adjusting the fuel-air ratio of the primary combustion section to be within an appropriate range. The structure is also possible. Only the primary combustion is used in the range from the start of the gas turbine to the low load operation, and the range from the low load to the rated load operation is the primary,
Combustion of both secondary. When transitioning from primary combustion only to both primary and secondary combustion, it is necessary to ignite the secondary combustion mixture with the primary combustion flame. This ignition timing is performed during the low load operation of the gas turbine, as described above, but since the gas turbine is operated at a constant rated rotation speed, the rotation speed of the compressor is also constant, compressed air, That is, since the combustion air flow rate is constant, the combustion ratio depends only on the fuel flow rate, and in order to maintain good combustion characteristics and exhaust gas characteristics, it is essential to adjust the combustion air flow rate. There is. Therefore, when igniting the air-fuel mixture for secondary combustion, the flow passage area of the opening 20 is adjusted to be smaller by moving the movable piece 22 so that the fuel-air ratio of the air-fuel mixture can be ignited. If the fuel-air ratio is appropriate, the flow rate of the combustion air 21 becomes extremely small and the air-fuel mixture is ignited, but the inflow speed of the air-fuel mixture into the rear combustion chamber becomes very small and the combustion flame Flows back to the spout 18 and spouts 18
It burns out the vicinity, or the combustion flame fluctuates, causing abnormal conditions such as combustion vibration. Therefore, the movable piece 22
The movement is limited to the range where the combustion flame does not flow back. As a result, the fuel-air ratio of the secondary combustion mixture is
The amount of air becomes larger than the predetermined amount, which is a small value. Here, the control of the fuel flow rate in the case of shifting from only the primary combustion to both the primary and secondary combustion will be described. The output of the gas turbine is proportional to the fuel flow rate for power generation that is operated at a constant rotation speed, and the output is maintained only with the primary fuel during the low load operation of the primary combustion only. However, during the primary and secondary combustion, the output is maintained at the total fuel flow rate of the primary fuel flow rate and the secondary fuel flow rate, and when it comes to only the primary fuel, it shifts to the case of the primary combustion time and the primary and secondary combustion. In the case of time, the fuel flow rate is much smaller in the case of transition to the primary combustion and the secondary combustion, and the fuel-air ratio becomes smaller, which may adversely affect the combustion performance. Also,
As described above, in the secondary combustion section, the flow rate of combustion air is large and the fuel-air ratio is small. In order to solve these problems, as shown in FIG. 1, the combustion air being compressed by the compressor is extracted before reaching the inside of the casing 4 in which the combustor is mounted, and the pressure of the compressed air is higher than that of the compressed air. Low exhaust gas 23
Medium or, in communication with the exhaust chamber or the exhaust duct, and controlling the amount of bleed air by the flow rate adjusting valve 24, to reduce the amount of combustion air overall, so that the fuel-air ratio is in a corrected range There is. Here, high-temperature, high-pressure compressed air during work of the compressor, that is, combustion air is extracted without passing through not only the combustor but also the turbine 2, so that the passing combustion gas in the turbine 2 decreases and the output However, this decrease in output is compensated for by increasing the fuel flow rate, and this bleed air substantially increases the fuel flow rate and decreases the air flow rate, leading to an increase in the fuel-air ratio. . Moreover, this increase in the fuel-air ratio is very effective at the start of the primary and secondary combustion. FIG. 3 shows a control diagram. The horizontal axis represents the gas turbine load, the vertical axis represents the movable piece opening, the extraction amount and the fuel-air ratio, and the horizontal axis is the same scale. Normally, in order to achieve low NOx in a combustor, a lean low temperature combustion method with a low combustion flame temperature is effective, and the performance is almost determined by the combustion method and the fuel-air ratio. In FIG. 3, the fuel-air ratio shows the proper range when the lower combustion range is the primary combustion section when the diffusion combustion system is used, and the upper range is the proper range when the secondary combustion section is the premixed combustion system. Shows. In both ranges, the upper limit is determined by the limit value of NOx value resulting from the flame temperature rise due to the increase of the fuel-air ratio, and the lower limit is determined by the limit value of CO value caused by incomplete combustion, which is due to the combustible limit. However, in any case, if the combustion ratio cannot be controlled within this range, a combustor with satisfactory combustion performance and exhaust gas characteristics cannot be obtained. Here, regarding FIG.
The details will be described. Control from the start up to the rated speed is not shown in this figure, but the fuel flow rate is increased so that the specified fuel-air ratio is achieved in proportion to the increase in the air amount due to the increase in the speed with only primary combustion. The fuel / air ratio reaches the rated speed and the gas turbine load is 0 as shown in the figure. After reaching the rated speed, load operation starts, but during this load operation, the rotation speed is constant and the compressed air from the compressor, that is, the amount of combustion air flowing into the combustor. Is constant. Therefore, as will be described later, unless the amount of combustion air is specially adjusted, the load of the gas turbine is controlled by controlling the fuel flow rate. In low-load operation with only primary combustion, the fuel flow rate increases as the load increases from load 0 in the fully opened state without changing the opening of the movable piece that adjusts the air flowing into the secondary combustion section. It is rising within the proper fuel air ratio range. Furthermore, as the load increases, the fuel flow rate increases and the fuel-air ratio rises, but the NOx amount tends to increase near the upper limit of the fuel-air ratio. The amount is gradually reduced by moving the opening of the movable piece in the closing direction, and this operation increases the amount of air flowing into the head combustion chamber. The fuel-air ratio is almost constant, suppressing the increase in NOx concentration. The opening of the movable piece further moves in the closing direction as the load increases, and the movement is completed in a state where it is open to some extent before being fully closed. Incidentally, the reason why the movable piece is not fully closed is that, as described above, the air amount becomes extremely small when fully closed, which may cause backflow of combustion flame or abnormal combustion. After that, the load of secondary fuel is increased without changing the amount of air by increasing the primary fuel, but the fuel flow rate when transitioning from only primary combustion to primary and secondary combustion is Only the fuel flow rate, the total fuel flow rate of the primary fuel and the secondary fuel after the transition, and if the gas turbine load does not change before and after the transition, the total fuel flow rate must also be constant, in the case of only primary combustion The fuel-air ratio of the primary combustion part and the fuel-air ratio of each of the primary combustion part and the secondary combustion part at the time of primary and secondary combustion are within an appropriate fuel-air ratio range that can maintain good combustion performance and exhaust gas characteristics. Must be However, when attempting to shift from primary combustion to primary and secondary combustion with the air amount kept constant after the movement of the movable piece is completed, the fuel-air ratio changes as shown by the broken line in FIG. Results in falling below the lower limit of the fuel-air ratio, and as shown in Fig. 4, CO due to incomplete combustion is generated as shown by the broken line in the exhaust gas characteristics, and NO
Although the x concentration is low, it results in unstable combustion with extremely low combustion performance, resulting in various problems. Therefore, the present invention intends to extract and reduce the combustion air flowing into the combustor in a state where the movement of the movable piece is completed, so as to obtain an appropriate fuel-air ratio. Specifically, the air being compressed in the compressor is gradually extracted from the intermediate stage of the compressor as the load increases, and the primary combustion is transferred to the primary and secondary combustion.
It is designed to be controlled by the flow rate adjusting valve so that it becomes maximum. In the gas turbine, the amount of combustion air decreases due to bleeding, the amount of combustion gas decreases, and the output decreases, but the output is reduced in proportion to the amount of bleeding because it is controlled to perform constant load operation. The amount of fuel to be supplemented is further supplied, and as a result, the fuel-air ratio rises as seen in the change in the fuel-air ratio in FIG. Due to this bleed air, the combustion temperature rises due to the increase in the fuel-air ratio, and the NOx concentration rises somewhat as shown in FIG. 4, but it is lower than during rated operation and is not a problem. The CO concentration does not change much during primary combustion due to bleeding, but the fuel flow rate to compensate for the output that the fuel-air ratio of the primary and secondary combustion parts after transitioning to primary and secondary combustion has decreased due to bleeding As it increases and becomes in the proper fuel air ratio range, it is extremely reduced compared to the conventional case. As a result, the combustion performance can be improved as compared with the conventional case. After the primary and secondary combustion transitions, the fuel flow rate tends to increase as the load increases and the fuel-air ratio tends to increase.Therefore, the bleed air amount is gradually reduced by closing the flow rate adjustment valve, and the fuel-air ratio becomes The bleed volume is set to zero while keeping the fuel air ratio within a proper range. Further, as the load increases, the amount of air flowing into the secondary combustion section is moved to the fully open direction by moving the movable piece in the direction of full opening, and the movable piece is moved to full opening while being adjusted. . After that, the air amount is not adjusted, the load rises due to the increase in the fuel flow rate, and the fuel-air ratio rises due to the increase in the fuel amount, but in this high load range, when the air amount adjustment is completed Since the fuel-air ratio is adjusted so that it is close to the lower limit of the proper fuel-air ratio range, the air-fuel ratio only rises within the proper fuel-air ratio range even if the air amount is not adjusted. , The combustion performance and exhaust gas characteristics are not affected. As described above, the present invention is applicable to a two-stage combustor or other multi-stage combustors, and has an appropriate fuel-air ratio in all load zones in order to maintain good combustion characteristics and exhaust gas characteristics of the combustor. It is characterized in that the amount of combustion air can be adjusted in whole or in part so as to be within the range.

5 and 6 show modified examples of the present invention. In each case, the connection of the air extracted from the intermediate stage of the compressor is a modification of FIG. In FIG. 5, the air 1C that is being compressed in the compressor 1 is extracted from the compressor through the pipe 25 and is communicated with the low pressure stage 1b of the compressor 1 which is lower than the extraction pressure through the flow rate control valve 24. As a result, the air under compression is bleed to the low pressure part and communicated with it to reduce the amount of compressed air after the bleed part,
Finally, the amount of combustion air flowing into the combustor is reduced. FIG. 6 shows that the air 1C being compressed by the compressor 1 is extracted by the pipe 25 and communicated via the flow rate control valve 24 to the intermediate stage 2a of the turbine section having a lower pressure than that of the extracted air. Energy is recovered by merging the compressed air with the combustion gas of the turbine section, and the efficiency decrease due to extraction air is mitigated. That is, in both cases, the purpose is to adjust the amount of combustion air flowing into the combustor by the bleed air from the compressor.

〔The invention's effect〕

According to the present invention, the amount of combustion air in the combustor can be adjusted partially or wholly, so that it can be accurately controlled under all conditions so that it falls within an appropriate fuel-air ratio range. It is possible to maintain good combustion performance and exhaust gas characteristics of the combustor in the full load zone of the turbine, particularly when transitioning from diffusion combustion to premixed combustion. Further, by extracting compressed air from the intermediate stage of the compressor, energy loss in the compressor can be reduced.

[Brief description of drawings]

1 is a sectional view of an embodiment of the present invention, FIG. 2 is a sectional view of a combustor of the present invention, FIG. 3 is an explanatory view of a control method, and 4
FIG. 5 is an exhaust gas characteristic diagram, and FIGS. 5 and 6 are system diagrams showing modified examples of the present invention. 3 ... Combustor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Isao Sato 502 Jinritsu-cho, Tsuchiura-shi, Ibaraki Machinery Research Laboratory, Hiritsu Manufacturing Co., Ltd. (56) Reference JP-A-60-218535 (JP, A)

Claims (1)

[Claims] 1. A diffusion combustion means for supplying fuel and air to a combustion chamber to perform diffusion combustion and a fuel and air are mixed in advance,
A gas turbine comprising a combustor having premixed combustion means for supplying the mixture to the combustion chamber for premixed combustion, and a compressor supplying air used in the combustor, A first air flow rate control means for extracting compressed air from an intermediate stage of the compressor and controlling a flow rate of the air supplied to the combustor; and a premixed combustion means of the air supplied from the compressor to the combustor. Second to control the flow rate of the supplied air
When the load of the gas turbine is in the vicinity of the load for starting the premix combustion by the premix combustion means, the second air flow control means supplies the premix combustion means to the premix combustion means. A gas turbine characterized in that the flow rate of air supplied to the combustor is reduced by the first air flow rate control means in a state where the flow rate of air to be reduced is reduced.