JPH0874604A - Combustion method for liquid fuel, and device for the same - Google Patents

Abstract

PURPOSE: To satisfactorily keep frame stability in the case that liquid fuel is burned and reduce an exhaust rate of NOx. CONSTITUTION: Fuel for premixture combustion is atomized to a mixture chamber 17 by the use of atomizing air from an atomizer 11 for premixture combustion, and mixed with air for combustion, and forms premixture frame in a combustion chamber 12. Atomized fuel grain is so controlled that its velocity and velocity of combustion air inside the mixture chamber 17 have proper ratio according to a load of a gas turbine. The atomized condition is controlled by varying a gas-liquid weight ratio (atomized air mass flow rate/fuel mass flow rate). A proper gas-liquid weight ratio is selected under the respective load of the gas turbine by means of an atomized air flow determining device 23. A flow rate of atomizing air is determined based on the selected result and the fuel flow rate. At the same time, combustion oscillation intensity of the combustion chamber is analized by means of a combustion oscillation intensity analizing device 21. When pressure fluctuation is larger than the preset value, a flow rate of the air for atomization which is previously determined is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid fuel combustion method and apparatus.

[0002]

2. Description of the Related Art Conventionally, diffusion combustion has been used as a combustion method in a practical combustor, in which fuel and air are supplied from different jet outlets and burned while being mixed in a combustion chamber. On the other hand, recently, premixed combustion, in which fuel and air are mixed and then burned, is being used.

The main advantages of using premixed combustion are the following two points. One is that the use of premixed combustion makes it possible to reduce the reaction area of combustion, that is, the flame can be shortened, and combustion with a higher load than in the past can be performed. The other is that NOx emissions are reduced by using the lean fuel premix combustion method.
In diffusion combustion, even if the fuel is burned under lean conditions, there is always a region where the air ratio is near 1 in the process of mixing the fuel and air in the combustion chamber, so it is generally difficult to reduce NOx. It is supposed to be. On the other hand, in premixed combustion with a high air ratio, that is, in the combustion method in which excess air and fuel are premixed and burned, the fuel burns under lean conditions in all regions, so NOx It is easy to reduce. Such a lean premixed combustion method is a gas turbine
It is being used in bottle combustors, etc.
-35016 publication). The lean premixed combustion method can be realized relatively easily when the fuel is gas. that is,
This is because the gaseous fuel is jetted into the air and is naturally mixed after a certain period of time.

Lean premixed combustion of liquid fuels is also known in the art (eg, US Pat. No. 4,246,757) but is difficult to achieve. This is because premixed combustion does not occur only by mixing the liquid fuel with air, and a process of further vaporizing the liquid fuel is required. In order to accelerate the evaporation of the liquid fuel, a technology for atomizing the fuel is necessary, and various innovations have been made so far, such as the combustor described in, for example, U.S. Pat.Nos. 3483701, 3530667, 3657885. However, it is difficult for a practical combustor to completely evaporate the liquid fuel. On the other hand, the Aeronautical Technology Research Institute TM-470 examines the relationship between the structure of the fuel injection valve and the NOx concentration, and examines the NOx emission characteristics when the liquid fuel is not completely evaporated. In this report, even if the liquid fuel could not be completely evaporated, the structure of the fuel injection valve was devised to reduce the NOx concentration during complete premixed combustion (completely evaporating the fuel and mixing it with air. It can be reduced to the extent that there is no great difference in practical use with other combustion conditions).

On the other hand, in order to put such lean premixed combustion of liquid fuel into practical use, not only the NOx concentration but also flame stability such as blowout limit, oscillatory combustion occurrence limit, flashback limit, etc. are considered. Although necessary, flame stability was not considered in the above-mentioned prior art.

[0006]

As described above, the prior art has proposed a combustor and a liquid fuel spraying device necessary for reducing the NOx concentration when the liquid fuel is subjected to lean premix combustion. However, it was not described whether flame stability would be improved or decreased by adopting the proposed combustor and liquid fuel spraying device. Moreover, the method for improving flame stability was not described.

It is an object of the present invention to provide a liquid fuel combustion method, a liquid fuel combustion apparatus operating method, and a liquid fuel combustion apparatus, which maintain good flame stability and reduce NOx emissions. Is.

[0008]

In order to achieve the above object, the present invention provides a method in which atomized liquid fuel is sprayed into an air stream, mixed with air, and a part of the mixed liquid fuel is evaporated. In the method of burning a liquid fuel, wherein the mixed fuel is burned to form a flame, a ratio of a spray velocity of the atomized liquid fuel and a velocity of the air flow corresponding to a flow velocity of the air flow. It is characterized by controlling.

The above object is also to spray atomized liquid fuel into an air stream to mix it with air, evaporate a part of the mixed liquid fuel, and then burn the mixed fuel to produce a flame. In the liquid fuel combustion method to be formed, it can also be achieved by controlling the ratio between the atomization speed of the atomized liquid fuel and the flow speed of the air flow in accordance with the intensity of combustion vibration in the combustion.

The above object is also formed by an atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer and an air stream flowing in a predetermined direction, and the mixing chamber. In a method of operating a combustion apparatus including a combustion chamber for injecting and burning a mixture of fuel and air, the velocity of fuel particles sprayed from the atomizer and the air flow in the mixing chamber, corresponding to the load of the combustion apparatus. It is also achieved by controlling the ratio of the flow velocities.

Here, as a method of controlling the ratio of the velocity of the fuel particles sprayed from the atomizer and the velocity of the air flow in the mixing chamber, as described above, the method of controlling in accordance with the load of the combustion device is used. In addition, there are a method of controlling according to the flow velocity of the air flow in the mixing chamber and a method of controlling according to the intensity of combustion vibration in the combustion chamber.

The above object is further formed by an atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer and an air stream flowing in a predetermined direction, and the mixing chamber. In a combustion device including a combustion chamber for injecting and burning a mixture of fuel and air, the velocity of the fuel particles sprayed from the atomizer and the flow velocity of the air flow in the mixing chamber are corresponded to the load of the combustion device. Optimum spray condition determination means for determining a spray condition such that the ratio is optimum, and spray for controlling the spray condition of the fuel particles in response to the optimum spray condition signal output from the optimum spray condition determination means for the fuel particles. It is also achieved by providing condition control means.

The above object is further formed by an atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer and an air stream flowing in a predetermined direction, and the mixing chamber. In a combustion device including a combustion chamber for injecting and burning a mixture of fuel and air, the velocity of the fuel particles sprayed from the atomizer and the air flow in the mixing chamber, corresponding to the air velocity in the mixing chamber. Optimum spray condition determination means for determining the spray condition such that the ratio of the flow velocities is optimal and outputting the optimum spray condition signal, and the optimum spray condition signal output from the optimum spray condition determination means as an input It is also achieved by providing a spray condition control means for controlling the spray condition.

The above object is further formed by an atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer and an air stream flowing in a predetermined direction, and the mixing chamber. In a combustion device including a combustion chamber for ejecting and burning a mixture of fuel and air, the velocity of the fuel particles sprayed from the atomizer and the air flow in the mixing chamber corresponding to the combustion vibration intensity in the combustion chamber. Of the fuel particles by inputting the optimum spray condition signal outputted from the optimum spray condition judging means for judging the spray condition such that the ratio of the flow velocities is optimum and outputting the optimum spray condition signal. It is also achieved by providing a spray condition control means for controlling the spray condition of.

It is desirable that the atomizer be supplied with atomizing air having a pressure higher than that of the air flow mixed with the fuel in the mixing chamber.

The optimum spraying condition determining means may specifically be means for selecting a flow rate ratio between the fuel supplied into the atomizer and the atomizing air.

Specifically, the optimum spraying condition signal may be a signal indicating a flow rate ratio between the fuel supplied to the atomizer and the atomizing air, or a signal indicating the flow rate of the atomizing air.

Specifically, the atomizing condition control means may be means for controlling the flow rate of the atomizing air supplied into the atomizer.

In the combustion apparatus of the present invention, a program representing the relationship between the load of the combustion apparatus and the optimum flow rate ratio of the fuel to be supplied into the atomizer at that time and the atomization air is further added to the optimum spray. It is desirable that the condition determining means be provided.

In the combustion apparatus of the present invention, the program representing the relationship between the flow velocity of air in the mixing chamber and the optimum flow rate ratio of the fuel to be supplied into the atomizer and the atomizing air at that time is described above. It is desirable that the means is provided in the optimum spray condition determination means.

The combustion apparatus of the present invention further comprises means for measuring the time variation of the pressure in the combustion chamber, means for frequency-analyzing the time variation of the pressure, and outputting combustion vibration intensity.
When the combustion vibration intensity exceeds a predetermined allowable value,
It is desirable to include means for increasing the flow rate ratio of the fuel supplied into the atomizer and the atomizing air.

[0022]

In the gas turbine combustor and the like, it is required at the same time to reduce the NOx emission amount and prevent flame misfire and flashback. To reduce NOx emissions, flame misfires,
Which is the most important issue, which is to prevent flashback and form a stable flame, depends on the operating conditions, load, etc. of the combustor.

FIG. 5 shows general results of flame blowout limit and flashback limit when the liquid fuel was pre-evaporated and premixed and burned, which was obtained as a result of experiments conducted by the inventors using various liquid fuels. The characteristic is shown with the air ratio of the premixed gas on the horizontal axis and the ejection speed on the vertical axis. In the figure, the curve A on the high air ratio side represents the blowout limit, and the curve B on the low air ratio side represents the flashback limit. Stable combustion occurs when the air ratio and ejection speed of the premixed gas are between the curve A indicating the blowout limit and the curve B indicating the flashback limit in the figure. Further, the ejection speed on the vertical axis in the figure is the average flow velocity of the combustion air in the mixing chamber.

As shown in FIG. 5, when the ejection speed is kept constant and the air ratio is decreased, flashback occurs, and when the air ratio is increased, blowout occurs. Further, the NOx emission amount tends to decrease as the air ratio of the premixed gas increases.

When the load is low, the jet speed of the premixed gas is low, and at this time, the flame is likely to be extinguished and the flashback is likely to occur, so that it is more important to form a stable flame. On the other hand, when the load is high, the ejection speed of the premixed gas is high, and at this time there is not much risk of flashback. In addition, blowing out is less likely to occur than when the load is low. However, the amount of combustion increases, so the NO emitted
The total amount of x increases. Therefore, when the load is high, the reduction of NOx emissions is more important than when the load is low.

In FIG. 5, the blowout limit and the flashback limit are shown by one curve, but when liquid fuel is used, the blowout limit and the flashback limit are changed by changing the fuel spray conditions. Change. At the same time, the NOx emission characteristic also changes. Therefore, it is necessary to control the fuel spray conditions so that the stable combustion range is widened when the load is low and the NOx emission amount is reduced when the load is high.

The fuel spray conditions necessary for the reduction of NOx and the expansion of the stable combustion range found by the inventors as a result of the study are as follows.

(1) In order to reduce NOx, it is most important to increase the degree of evaporation of fuel particles as much as possible. However, there is no relation between the degree of evaporation of fuel particles and the width of the stable combustion range.

(2) In order to expand the stable combustion range, it is most important to minimize the difference between the velocity of fuel particles and the velocity of combustion air. However, there is no relationship between the difference between the velocity of the fuel particles and the velocity of the combustion air and the NOx emission concentration.

Therefore, in order to reduce NOx and expand the stable combustion range, it is necessary to control different factors in the spray conditions. In particular, when the combustion load is low, it is necessary to finely control the fuel spray conditions in accordance with the flow velocity of the combustion air in order to prevent blowout and flashback.

Generally, before the blowout and the flashback occur, combustion vibration often occurs in advance, and at this time, a strong pressure fluctuation occurs. Therefore, the pressure fluctuations in the combustion device were measured, and the combustion conditions were controlled so that the gas-liquid weight ratio was reduced when the pressure fluctuation strength exceeded a certain value. it can.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a gas turbine power generation facility to which an embodiment of the present invention is applied.

The illustrated equipment includes a fuel tank 35, a combustion device 100 connected to the fuel tank 35, a gas turbine 7 driven by the combustion gas generated by the combustion device 100, and the gas turbine 7. The generator 8 and the air compressor 6 to be driven are included. The air compressor 6 is connected to the combustion device 100 and supplies compressed air.

The illustrated combustion system 10 is an embodiment of the present invention.
Reference numeral 0 denotes a fuel supply device 36 that is connected to the fuel tank 35 to feed the fuel under pressure, and a premixed combustion fuel flow rate control valve 27 that is connected in parallel to the outlet side of the fuel supply device 36.
And a diffusion combustion fuel flow rate control valve 28, a combustor 200 connected to these valves and supplied with fuel, a combustion air pipe 45A connecting the discharge port of the air compressor 6 and the combustor 200, A boosting compact compressor 3 connected to the combustion air pipe 45A through a spraying air flow control valve 4, and a spraying air pipe 2A connecting the discharge port of the boosting compact compressor 3 and the combustor 200. And the basic control device 32 for determining the fuel flow rate and the diluted air amount by inputting the load signal 33.
And a premixed combustion fuel flow rate control device 26 connected to the basic control device 32 to control the opening degree of the premixed combustion fuel flow rate control valve 27, and the diffusion combustion connected to the basic control device 32. Diffusion combustion fuel flow rate control device 25 for controlling the opening of the fuel flow rate control valve 27, combustion vibration intensity analysis device 21 connected to the pressure sensor 19 of the combustor 200 for receiving the pressure fluctuation signal 20, and the combustion vibration intensity. The spray air flow rate determination device 23 connected to the analysis device 21 and the basic control device 32, and the spray air flow rate control signal 24 output from the spray air flow rate determination device 23 are input to the spray air flow rate control valve 4. The atomizing air flow rate control device 5 for controlling the opening degree and the position of the slide ring 37 of the combustor 200 using the dilution air flow rate control signal 18 output by the basic control device 32 as an input. Controlling the dilution air amount control device 14
And are included.

The combustor 200 includes a cylindrical combustor casing shell 15A, a casing end plate 15B attached so as to close the fuel supply side (upstream side) end of the combustor casing shell 15A, and the combustor casing. A stepped cylindrical inner case 15C concentrically installed in the case 15A and the inner case 15C inside the casing end plate 15B side (small diameter portion) of the inner case 15C.
A plurality of cylindrical mixing chambers 17 that are arranged inscribed in C and have open downstream ends, and support plates 39 at the downstream ends of the mixing chambers 17.
And a flame stabilizer 16 supported and disposed in the center of the plurality of mixing chambers 17, that is, the casing end plate 15 of the inner case 15C.
A cylindrical diffusion combustion atomizer section 15D arranged on the B-side center line, and a double-tube premix combustion atomizer 11 arranged so as to penetrate the casing end plate 15B in each of the plurality of mixing chambers 17. A double tubular diffuser combustion atomizer 13 disposed in the diffusion combustion nozzle section 15D so as to penetrate through the center of the casing end plate 15B, and a large-diameter portion of the combustor casing body 15A and the inner body 15C. A pressure sensor 19 arranged to detect the pressure in the large diameter portion (combustion chamber 12) of the inner shell 15C and output a pressure fluctuation signal 20.
And a dilution air hole 15E formed on the circumferential wall surface of the large diameter portion of the inner case 15C, and a slide ring 3 for opening and closing the dilution air hole 15E by advancing and retracting in the axial direction on the outer peripheral surface of the inner case 15C.
7 and are included.

The premixed combustion atomizer 11 is composed of a double pipe, and the inner pipe has a premixed combustion fuel flow control valve 2
7, the space between the outer pipe and the inner pipe is connected to the discharge port of the booster compact compressor 3 by the spray air pipe 2A.
The downstream end of the inner pipe is arranged at a predetermined distance from the downstream end of the outer pipe, and the downstream end face of the inner pipe is provided with a small hole for injecting fuel. Fuel is atomized on the downstream end surface of the outer pipe to mix chamber 17
There is a small hole that gushes out.

Like the premixed combustion atomizer 11, the diffusion combustion atomizer 13 is constituted by a double pipe, and the inner pipe is connected to the diffusion combustion fuel flow rate control valve 28 so that it is between the outer pipe and the inner pipe. This space is connected to the discharge port of the booster compact compressor 3 by the atomizing air pipe 2A. The downstream end of the inner pipe is arranged at a predetermined distance from the downstream end of the outer pipe, and the downstream end face of the inner pipe is provided with a small hole for injecting fuel. A small hole for atomizing fuel and ejecting it into the combustion chamber 12 is provided on the downstream end surface of the outer tube. In the diffusion combustion nozzle section 15D, a concentric cylindrical flow path of the combustion air 45 is formed so as to surround the outer periphery of the diffusion combustion atomizer 13, and the downstream end thereof is provided with a swirler 38. An opening is formed in the combustion chamber 12.

A combustion air flow passage section 15F is formed between the combustor casing body 15A and the inner body 15C, and the combustion air pipe 45A is provided at the downstream end of the combustion air flow passage section 15F. It is connected. Combustion air flow path section 15
F is also communicated with the upstream end of the mixing chamber 17 and the upstream end of the flow path of the cylindrical combustion air 45 that is concentrically formed so as to surround the outer periphery of the diffusion combustion atomizer 13. It is designed to supply combustion air.

The operation of the apparatus having the vapor structure will be described below.
The liquid fuel is supplied from the fuel tank 35 to the combustor 200 via the fuel supply device 36. Here, a pump or the like is used for the fuel supply device 36. The fuel sent from the fuel supply device 36 is divided into two systems, that is, the fuel for premixed combustion and the fuel for diffusion combustion, and the flow rate is controlled by the fuel flow control valve 27 for premixed combustion and the fuel flow rate control valve 28 for diffusion combustion, respectively. Adjusted. After the flow rate is adjusted, the premixed combustion fuel is sprayed from the premixed combustion atomizer 11 into the mixing chamber 17 and mixed with the combustion air 45. The fuel and air mixed in the mixing chamber 17 are ejected into the combustion chamber 12 to form a premixed flame. This premixed flame is held by the flame stabilizer 16. The diffusion combustion fuel is directly sprayed from the diffusion combustion atomizer 13 into the combustion chamber 12 and mixed with the combustion air 45 in the combustion chamber 12 to form a diffusion flame.

The air 1 is sucked into the air compressor 6 and boosted in pressure. Most of the pressurized air is sent as combustion air 45 to the combustion air flow passage section 15F of the combustor 200 via the combustion air pipe 45A. Most of the combustion air 45 is used to form a premixed flame or a diffusion flame. The air for forming the premixed flame is preheated in the combustion air flow passage section 15F, and then jetted into the combustion chamber 12 through the mixing chamber 17. The air for forming the diffusion flame does not pass through the mixing chamber 17 and the combustion air flow passage section 15
From F through the diffuser combustion atomizer 13 and the swirler 3
It is jetted into the combustion chamber 12 through 8. Combustion air 45
A part of the air is used as the diluted air 46, and the combustion air flow passage section 1
5F is fed directly to the downstream side of the combustion chamber 12 through the diluted air hole 15E. The amount of this diluted air 46 is adjusted by the slide ring 37. Normally, the opening of the dilution air hole 15E is adjusted by moving the slide ring 37 so that the diluted air flow rate is large when the gas turbine load is small, and the diluted air flow rate is small when the gas turbine load is large. By adjusting the amount of the diluted air 46 in this way, the amount of air supplied to the mixing chamber 17 can be set to a desired value. Although not shown in FIG. 1, part of the combustion air 45 is also used for cooling the wall surface of the combustor.

Part of the air boosted by the air compressor 6 is
The compressed air is sent to the compact compressor 3 and used as the atomizing air 2. The atomizing air 2 is a premixed combustion atomizer 11,
Also, it is supplied to the atomizer 13 for diffusion combustion and used for atomizing the fuel. The flow rate of the atomizing air 2 is adjusted by the atomizing air flow rate control valve 4.

The high temperature combustion gas 10 discharged from the combustor 200 is guided to the gas turbine 7 to drive the gas turbine 7, and the gas turbine 7 drives the generator 8 and the air compressor 6 connected to each other. To do. The combustion exhaust gas 9 after driving the gas turbine 7 is discharged from a stack (not shown) through a waste heat recovery boiler (not shown) and a flue gas denitration device.

Next, a method of controlling the fuel flow rate and the air flow rate will be described.

The fuel flow rate and the diluted air amount are determined by the basic control device 32. A load signal 33 output from a device (not shown) is sent to the basic control device 32 based on the load request of the gas turbine, and based on the load signal 33 and the fuel injection plan provided in the basic control device 32, The fuel flow rate and the diluted air flow rate are determined, and the fuel flow rate control signal 3
1, the premixed combustion fuel flow rate control signal 29, the diffusion combustion fuel flow rate control signal 30, and the diluted air flow rate control signal 18 are output.

The fuel supply device 36 controls the rotation speed of the motor connected to the pump in the fuel supply device 36 based on the fuel flow rate control signal 31. The premixed combustion fuel flow rate control device 26 determines the opening degree of the premixed combustion fuel flow rate control valve 27 based on the premixed combustion fuel flow rate control signal 29, and is provided in the premixed combustion fuel flow rate control device 26. The opening degree of the premixed combustion fuel flow rate control valve 27 is adjusted by the selected motor. The diffusion combustion fuel flow rate control device 25 determines the opening degree of the diffusion combustion fuel flow rate control valve 28 on the basis of the diffusion combustion fuel flow rate control signal 30, and a mode provided in the diffusion combustion fuel flow rate control device 26. The opening of the diffusion combustion fuel flow rate control valve 28 is adjusted by a counter. The diluted air flow rate control device 14 determines the opening degree of the diluted air hole 15E on the basis of the diluted air flow rate control signal 18, and moves the slide ring 37 by the motor provided in the diluted air flow rate control device 14. The opening of the diluted air hole 15E is adjusted to the determined opening. In addition to the control signals described above, the basic control device 32 outputs a premixed combustion fuel flow rate signal 34 to the atomizing air flow rate determination device 23.

The flow rate of the atomizing air 2 is determined by the atomizing air flow rate determining device 23. The atomizing air flow rate determination device 23 is provided with a program that represents the load of the gas turbine and the optimum gas-liquid weight ratio (atomizing air mass flow rate / fuel mass flow rate) at that time. The liquid weight ratio is selected. The atomizing air flow rate determination device 23 then
The optimum spray air flow rate is determined based on the selected gas-liquid weight ratio and the input fuel flow signal for premixed combustion 34, and the spray air flow rate control signal 24 is output to the spray air flow rate control device 5. The atomizing air flow rate control device 5 determines the opening degree of the atomizing air flow rate control valve 4 based on the atomizing air flow rate control signal 24, and atomizes by a motor provided in the atomizing air flow rate control device 5. The opening degree of the air flow rate control valve 4 is adjusted to the determined opening degree.

The pressure sensor 19 provided in the combustor 200 in FIG. 1 outputs the pressure fluctuation signal 20 to the combustion vibration intensity analysis device 21. The combustion vibration intensity analysis device 21 analyzes the frequency of the pressure fluctuation signal 20 to obtain the magnitude of the pressure fluctuation and the frequency at which the pressure fluctuation becomes the maximum, and when the magnitude of the pressure fluctuation is larger than a predetermined value, the pressure fluctuation is determined. The combustion vibration intensity signal 22 representing the magnitude of the above is output to the atomizing air flow rate determination device 23 and the basic control device 32. When the combustion vibration intensity signal 22 is output, the atomizing air flow rate determining device 23 responds to the load of the gas turbine by the atomizing air flow rate determining device 23 according to the magnitude of the input combustion oscillation intensity signal 22. Correct the optimum gas-liquid weight ratio selected. Normally, when the combustion vibration intensity signal 22 is large, the gas-liquid weight ratio is corrected so that the gas-liquid weight ratio becomes small.

FIG. 2 shows a modification of this embodiment, in which only the vicinity of the mixing chamber 17 is shown enlarged. In the embodiment of FIG. 1, the atomization air flow rate is controlled by one valve (atomization air flow rate control valve 4), but in the combustion apparatus of FIG. 2, a plurality of booster compact compressors 3 are arranged in parallel on the discharge side. Is provided, and atomized air is supplied to the atomizer for premixed combustion and the atomizer for diffusion combustion from one valve each. Therefore, the atomizing air flow rate is controlled for each atomizer. The atomizer characteristics such as the particle size and speed of atomized particles are slightly different for each atomizer due to the influence of dimensional error during manufacturing.
By controlling the atomizing air flow rate for each atomizer, the most desirable atomizing condition can be set for each atomizer.

The spray conditions include the fuel flow rate and the atomized air flow rate. The fuel flow rate control signal 31, the premixed combustion fuel flow rate control signal 29, and the premixed combustion fuel flow rate signal 34 are used to determine the fuel flow rate. There are a spray air flow rate control signal 24 and a diluted air flow rate control signal 18 for determining the spray air flow rate. These signals are output from each output source as signals indicating values forming the optimum spray condition, that is, the optimum spray condition signal. Each output source determines a value such that the spraying condition is optimum and outputs a signal, and each output source is also an optimum spraying condition determination means. On the other hand, the spray condition control means for controlling the spray condition based on the optimum spray condition signal is premixed for the fuel supply device 36 for the fuel flow rate control signal 31 and for the premixed combustion fuel flow rate control signal 29. Combustion fuel flow rate control device 26, spray air flow rate determination device 23 for premixed combustion fuel flow rate signal 34, spray air flow rate control device 5 for spray air flow rate control signal 24, diluted air flow rate control signal 18 On the other hand, it is the diluted air amount control device 14. The desirable spraying conditions here are spraying conditions such that the ratio between the speed of the fuel particles sprayed from the atomizer 11 and the flow speed of the air flow in the mixing chamber 17 is an appropriate value.

FIG. 3 is a diagram showing an example of a fuel injection plan in the gas turbine power generation facility of FIG. 1 or 2 in which the horizontal axis represents the load of the gas turbine and the vertical axis represents the fuel flow rate to determine the relationship between the two. . In the illustrated example, only the diffusion combustion fuel is supplied from the start of the gas turbine to a certain intermediate load, and after the certain intermediate load I is reached, the supply of the premixed combustion fuel is started. . Further, after the supply of the premixed combustion fuel is started, the supply amount of the diffusion combustion fuel is reduced.

FIG. 4 shows an example of the relationship between the gas turbine load and the optimum gas-liquid weight ratio at that time when fuel is supplied as shown in FIG. 3, with the gas turbine load as the horizontal axis. It is a figure which shows each container weight ratio on the horizontal axis. In addition,
FIG. 4 shows only the gas-liquid weight ratio of the atomizer for premixed combustion. Under the condition of load I at which the supply of the fuel for premixed combustion is started, the gas-liquid weight ratio is made small. This is to prevent flashback of the flame. When the premixed combustion atomizer shown in FIG. 1 or 2 is used, when the gas-liquid weight ratio is reduced, the NOx emission amount is slightly increased, but flashback is unlikely to occur. On the other hand, flashback is likely to occur under the load I combustion conditions.
When a flashback occurs, the combustor is destroyed, so under the load I combustion condition, the gas-liquid weight ratio should be small.
On the other hand, the gas turbine load is close to 100% I
Under the condition of I, the flashback is unlikely to occur, but the amount of fuel supply is large, and therefore the amount of NOx emission tends to be large. Therefore, under this condition, it is desirable to operate under a condition where the NOx emission amount can be reduced and the gas-liquid weight ratio is large.

The reason why it is desirable to control the gas-liquid weight ratio according to the gas turbine load as shown in FIG. 4 will be further explained by the experimental results obtained by using the combustion apparatus of FIG.
In the combustion device of FIG. 6, in addition to changing the gas-liquid weight ratio,
By moving the atomizer 11 in the flow direction, the pre-evaporation pre-mixing distance L can be changed. Therefore, the fuel spray conditions in this combustor can be changed in two ways, by changing the gas-liquid weight ratio and by changing the pre-evaporation premixing distance (L, L '). In addition, this combustor can observe the spray state such as the speed and concentration of the spray particles through the measurement window 46.

FIG. 7 is a vertical sectional view of the atomizer 11 used in the combustor of FIG. The atomizer is composed of double tubes. The fuel 42 flows into the central pipe (inner pipe) and is ejected at a high speed from a plurality of holes at the tip (for example, three holes arranged so as to form the apexes of a triangle). At this time, the fuel ejected from the plurality of holes collides with the atomizing air 2 introduced from the outer pipe (between the inner pipe and the outer pipe) to be atomized. A mixed fluid of atomized fuel (for example, naphtha or kerosene) and air is further atomized at the ejection end face A and ejected from the atomizer.

FIG. 8 shows the blowout limit and the flashback limit when the combustor of FIG. 6 is used, with the horizontal axis representing the air ratio and the vertical axis representing the jet speed of the premixed gas. Tin represents the temperature of the combustion air in the mixing chamber, and wa / wl represents the gas-liquid weight ratio. The line on the low air ratio side is the flashback limit, and the line on the high air ratio side is the blowout limit. The absolute values of the air ratios of the blowout limit and the flashback limit differ depending on the fuel. However, when the jet velocity is high, the air ratio at the flashback limit is low. When the jet velocity is 30 m / s or less, the smaller the jet velocity is, the narrower the range of stable air ratio is. The same. When a flashback occurs in the combustor shown in FIG. 6, strong combustion vibration occurred prior to that.

FIG. 9 shows the results of measuring the concentration of spray particles by changing the gas-liquid weight ratio (wa / wl) while keeping the pre-evaporation premixing distance (L ') constant and the gas-liquid weight ratio on the horizontal axis. Concentration (relative value)
Is plotted on the vertical axis. λ is the air ratio, and V is the combustion air velocity in the mixing chamber. Figure 10
Is the result of measuring the concentration of spray particles by changing the pre-evaporation pre-mixing distance while keeping the gas-liquid weight ratio constant, the pre-evaporation pre-mixing distance (L ') on the horizontal axis, and the particle concentration (relative value) on the vertical axis. It has been shown to. A decrease in the concentration of atomized particles means that evaporation was promoted. From these results,
It can be seen that evaporation is promoted when the gas-liquid weight ratio is increased and the pre-evaporation premixing distance is increased.

FIG. 11 shows the influence of the gas-liquid weight ratio on the NOx emission concentration, the blowout limit air ratio, and the flashback limit air ratio. If the gas-liquid weight ratio is increased and evaporation is accelerated, NO
Although the x emission concentration decreases, the range of the air ratio for stable combustion becomes narrow.

FIG. 12 shows the influence of the pre-evaporation pre-mixing distance on the NOx emission concentration and the stable combustion range. Pre-evaporation If the pre-mixing distance is increased and evaporation is accelerated, the NOx concentration will decrease,
The range of air ratio for stable combustion is also widened.

Considering the results of FIGS. 11 and 12, the NOx concentration decreases when evaporation is promoted regardless of whether the gas-liquid weight ratio or the pre-evaporation premixing distance is changed. That is,
There is a correlation between the NOx concentration and the ratio of evaporated fuel. On the other hand, regarding flame stability, when the gas-liquid weight ratio is changed, the range of the air ratio that can be stably combusted becomes narrower when the evaporation is promoted, whereas when the pre-evaporation premixing distance is changed, the evaporation is promoted. The range of stable air ratio is wide, and the effect on flame stability is opposite when the gas-liquid weight ratio is changed and when the pre-evaporation premixing distance is changed. Therefore, there is no correlation between flame stability and percentage of evaporated fuel. Flame stability is believed to be influenced by the behavior of unvaporized particles.

Among the behaviors of the particles which have not been evaporated yet, the velocity and the particle size of the particles are considered to be important. The results of measuring the particle size and velocity of the non-evaporated particles are shown in FIGS.

13 and 14 show the measurement results of the atomized particle size. As shown in FIG. 13, when the gas-liquid weight ratio is decreased, the particle size is increased, and at this time, flame stability is improved. Considering only this result, it is considered that flame stability is improved by increasing the size of the spray particles. However, FIG.
As shown in FIG. 4, although the difference in the pre-evaporation premixing distance has little effect on the particle size, the flame stability is improved when the pre-evaporation premixing distance is increased. Therefore, FIG.
Considering the results of both Nos. 14 and 14, it can be judged that there is not much relation between the particle size of the spray particles and the flame stability.

FIGS. 15 and 16 show the measurement results of the spray particle velocity. Here, the vertical axis represents the value obtained by dividing the time average value of the particle velocity by the average velocity of the combustion air, and the horizontal axis represents the gas-liquid weight ratio (FIG. 15) or the pre-evaporation premixing distance (FIG. 16). Indicated. Regardless of whether the gas-liquid weight ratio or the pre-evaporation premixing distance is changed, the smaller the difference between the average velocity of the spray particles and the air velocity, and the smaller the velocity fluctuation of the spray particles, the higher the flame stability.

Summarizing the above results, it is the velocity of the fuel particles that has the greatest effect on the flame stability. The smaller the difference between the velocity of the fuel particles in the pre-evaporation premix chamber and the velocity of the combustion air, the more stable the flame is. The sex is good. On the other hand, it is the degree of evaporation of the fuel particles that affects the NOx emission concentration, and the higher the ratio of evaporated fuel, the lower the NOx emission concentration.

Considering these results, the following two conditions are necessary to form a flame with low NOx emission concentration and good stability.

(1) The evaporation degree of fuel particles is made as high as possible.

(2) Pre-evaporation The difference between the particle velocity and the combustion air velocity in the pre-mixing chamber is minimized.

Increasing the pre-evaporation pre-mixing distance is the best measure because the above-mentioned problems (1) and (2) can be achieved at the same time. However, in practical combustors, the pre-evaporation pre-mixing distance cannot always be set to a necessary and sufficient length due to design restrictions and the like. In this case, in addition to the pre-evaporation pre-mixing distance, it is necessary to change the fuel spray conditions.

One of the typical methods for changing the spraying conditions is to change the gas-liquid weight ratio, but as described above, in the method for changing the gas-liquid weight ratio, the above (1) is used. , (2) cannot be achieved at the same time.

Therefore, in order to always form a flame having a low NOx emission concentration and good stability in a practical combustor,
It is necessary to change the fuel spray conditions according to the load.
In the present embodiment, when the load is low, it is blown off, and since the prevention of flashback is more important, the gas-liquid weight ratio is made small, and the difference between the particle velocity and the combustion air velocity in the pre-evaporation pre-mixing chamber,
Since it is more important to reduce the amount of NOx as much as possible and to reduce NOx when the load is high, the vapor-liquid weight ratio is increased to control the evaporation degree of the fuel particles as high as possible. Shape data of the mixing chamber, pressure and temperature on the discharge side of the air compressor 6,
Air property data such as the flow velocity, the opening data of the atomizing air flow control valve 4, the opening data of the slide ring 37, etc. are constantly input to the basic control device 32, and the mixing chamber is based on these data. The average flow velocity of the combustion air in the inside is calculated by the basic control device 32, and the spray air flow rate determination device 23
Is output to The particle velocity of the liquid fuel is calculated by the atomizing air flow rate determination device 23 by inputting the opening degree data of the atomizing air flow rate control valve 4, the atomizer shape data, the atomizing air pressure, and the fuel flow rate. Spray air flow rate determination device 23
Is the ratio of the two using the average velocity of the combustion air in the input mixing chamber and the calculated particle velocity of the liquid fuel.
To calculate. As described above, the atomizing air flow rate determination device 23 selects the gas-liquid weight ratio based on the input load signal 33. However, when the average flow velocity of the combustion air is input, it is determined at that point. When the gas turbine load is lower than a preset limit value and the difference between the calculated flow velocity ratio value and 1 exceeds the allowable range, the gas-liquid weight ratio to be selected is selected lower by a predetermined amount. Thus, by correcting the gas-liquid weight ratio to be selected based on the input average velocity of the combustion air in the mixing chamber, the particle velocity of the liquid fuel becomes the average velocity of the combustion air in the mixing chamber. Is blown away,
The flashback is effectively prevented.

Generally, before the blowout and flashback occur, combustion vibration often occurs in advance, and at this time, strong pressure fluctuation occurs. Therefore, the pressure fluctuation in the combustion device is measured by the pressure sensor 19, the measurement result is analyzed by the combustion vibration strength analysis device 21, and when the strength of the pressure fluctuation exceeds a certain value, the combustion vibration strength signal 22 is sprayed. It is output to the air flow rate determination device 23. Spray air flow rate determination device 23
When the combustion vibration intensity signal 22 is input, the combustion condition is controlled so as to reduce the gas-liquid weight ratio, blown off, and flashback is prevented.

FIG. 5 shows the general results of the flame blowout limit and flashback limit when the liquid fuel was pre-evaporated and premixed and burned, which was obtained as a result of experiments conducted by the inventors using various liquid fuels. Characteristic. In the figure, the curve A on the high air ratio side represents the blowout limit, and the curve B on the low air ratio side represents the flashback limit. Stable combustion occurs when the air ratio and the ejection speed of the premixed gas are between the blowout limit curve A and the flashback limit curve B in the figure.

The jet speed on the vertical axis in the figure is the average flow velocity of the combustion air in the mixing chamber. Shape data of the design mixing chamber, property data such as pressure and temperature of air, opening data of the atomizing air flow rate control valve 4, opening data of the slide ring 37, etc. are constantly input to the basic control device 32. Based on these data, the average flow velocity of combustion air in the mixing chamber is calculated. The speed of the liquid fuel is calculated by the basic control device 32 by inputting the opening data of the atomizing air flow rate control valve 4, the atomizer shape data, the atomizing air pressure, and the fuel flow rate.

As shown in FIG. 5, when the jet speed is kept constant and the air ratio is decreased, flashback occurs, and when the air ratio is increased, blowout occurs.

When the gas turbine load is low like the load I, the jet speed of the premixed gas is low, and the flame is easily extinguished and a flashback is likely to occur.

[0074]

According to the present invention, when burning a liquid fuel for combustion, it is possible to reduce the NOx emission concentration and at the same time maintain good flame stability, and blow out the flame particularly when the load is low, You can prevent flashback.

[Brief description of drawings]

FIG. 1 is a system diagram of a gas turbine power generator that is an embodiment of the present invention.

FIG. 2 is a system diagram (partial cross-sectional view) showing an example in which a part of the embodiment shown in FIG. 1 is modified.

FIG. 3 is a conceptual diagram showing an example of the relationship between the gas turbine load and the supplied fuel amount when the gas turbine power generator is operating, which is an embodiment of the present invention.

FIG. 4 shows a gas-liquid weight ratio (weight of supplied fuel / weight of atomized air), which is one of gas turbine load and fuel spray conditions when the gas turbine power generator is operating, which is one embodiment of the present invention. It is a conceptual diagram which shows an example of a relationship.

FIG. 5 is a conceptual diagram showing general characteristics of a stable combustion range when liquid fuel is premixed and burned.

FIG. 6 is a cross-sectional view showing a configuration of a combustion device used for verifying the principle of the present invention.

7 is a cross-sectional view showing a configuration of an atomizer provided in the combustion device shown in FIG.

8 is a graph showing a stable combustion range obtained when the liquid fuel is premixed and burned, which is obtained by using the combustion apparatus of FIG.

9 is a graph showing the relationship between the gas-liquid weight ratio and the concentration of atomized particles, obtained using the combustion apparatus of FIG.

10 is a graph showing the relationship between the premixing preevaporation distance and the concentration of atomized particles obtained by using the combustion apparatus of FIG.

FIG. 11 is a graph showing the effect of changes in the gas-liquid weight ratio on the NOx emission characteristics and the stable combustion range, obtained using the combustion apparatus of FIG.

FIG. 12 is a graph showing the effect of changes in the premixing preevaporation distance on the NOx emission characteristics and the stable combustion range, obtained using the combustion apparatus of FIG.

13 is a graph showing the relationship between the gas-liquid weight ratio and the particle size of atomized particles, obtained using the combustion apparatus of FIG.

FIG. 14 is a graph showing the relationship between the premixing preevaporation distance and the particle size of spray particles, obtained using the combustion apparatus of FIG.

15 is a graph showing the relationship between the gas-liquid weight ratio and the velocity of atomized particles, obtained using the combustion apparatus of FIG.

16 is a graph showing the relationship between the premixing preevaporation distance and the velocity of atomized particles obtained by using the combustion apparatus of FIG.

[Explanation of symbols]

1 Air 2 Air for Spraying 2A Air Pipe for Spraying 3 Small Compressor for Boosting 4 Air Flow Control Valve for Spraying 5 Air Flow Control Device for Spraying 6 Air Compressor 7 Gas Turbin 8 Generator 9 Combustion Exhaust Gas 10 High Temperature Combustion Gas 11 Premixed combustion atomizer 12 Combustion chamber 13 Diffusion combustion atomizer 14 Dilution air amount control device 15A Combustor casing body 15B Casing end plate 15C Inner body 15D Diffusion combustion atomizer compartment 15E Dilution air hole 15F Combustion air flow passage compartment 16 Flamer 17 Mixing chamber 18 Dilution air flow rate control signal 19 Pressure sensor 20 Pressure fluctuation signal 21 Combustion vibration intensity analysis device 22 Combustion vibration intensity signal 23 Spray air flow rate determination device 24 Spray air flow rate control signal 25 Diffusion combustion fuel flow rate control device 26 Premixed Combustion Fuel Flow Rate Control Device 27 Premixed Combustion Fuel Flow Rate Control valve 28 Fuel flow rate control valve for diffusion combustion 29 Fuel flow rate control signal for premixed combustion 30 Fuel flow rate control signal for diffusion combustion 31 Fuel flow rate control signal 32 Basic control device 33 Load signal 34 Fuel flow rate signal for premixed combustion 35 Fuel tank 36 Fuel Supply Device 37 Slide Ring 38 Swirler 39 Support Plate 40 Premixed Combustion Spray Air Control Valve 41 Diffusion Combustion Spray Air Control Valve 42 Premixed Combustion Fuel 43 Diffusion Combustion Fuel 45 Combustion Air 45A Combustion Air Pipe 100 Combustor 200 Combustor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiichi Kirikami 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory

Claims (17)

[Claims] 1. Atomized liquid fuel is sprayed into an air stream to be mixed with air, a part of the mixed liquid fuel is evaporated, and then the mixed fuel is burned to form a flame. In the method for burning liquid fuel, the method for burning liquid fuel is characterized in that the ratio between the atomizing velocity of the atomized liquid fuel and the velocity of the air flow is controlled according to the velocity of the air flow. 2. Atomized liquid fuel is sprayed into an air stream to be mixed with air, a part of the mixed liquid fuel is evaporated, and then the mixed fuel is burned to form a flame. In a liquid fuel combustion method, detecting the intensity of combustion oscillation in the combustion, and controlling the ratio between the atomization velocity of the atomized liquid fuel and the flow velocity of the air flow in accordance with the detected intensity. Characteristic liquid fuel combustion method. 3. An atomizer for atomizing and spraying a liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer with an air stream flowing in a predetermined direction, and a fuel and air formed in the mixing chamber. In a method of operating a combustion apparatus comprising a combustion chamber for jetting and burning a mixture of, a velocity of fuel particles sprayed from the atomizer and a flow velocity of an air flow in the mixing chamber, corresponding to the load of the combustion device. A method for operating a combustion device, comprising controlling a ratio. 4. An atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer with an air stream flowing in a predetermined direction, and the fuel and air formed in the mixing chamber. In a method of operating a combustion device comprising a combustion chamber for jetting and burning a mixture of, in accordance with the flow velocity of the air flow in the mixing chamber, the velocity of the fuel particles sprayed from the atomizer and the mixing chamber A method for operating a combustion device, comprising controlling the ratio of the velocity of an air flow. 5. An atomizer for atomizing and atomizing a liquid fuel, a mixing chamber for mixing the fuel atomized from the atomizer with an air stream flowing in a predetermined direction, and a fuel and air formed in the mixing chamber. In a method of operating a combustion apparatus comprising a combustion chamber for jetting and combusting a mixture of, the velocity of the fuel particles sprayed from the atomizer and the air in the mixing chamber corresponding to the intensity of combustion vibration in the combustion chamber. A method for operating a combustion device, comprising controlling a ratio of flow velocities. 6. An atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer with an air stream flowing in a predetermined direction, and a fuel and air formed in the mixing chamber. In a combustion apparatus including a combustion chamber that ejects and combusts the mixture of, the ratio of the speed of the fuel particles sprayed from the atomizer and the flow rate of the air flow in the mixing chamber is optimal according to the load of the combustion apparatus. And a spray condition control means for controlling the spray condition of the fuel particles in accordance with the optimum spray condition signal output from the optimum spray condition determination means for the fuel particles. And a combustion device. 7. An atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer and an air stream flowing in a predetermined direction, and the fuel and air formed in the mixing chamber. In a combustion device including a combustion chamber for jetting and burning the mixture of, the velocity of the fuel particles sprayed from the atomizer and the velocity of the air flow in the mixing chamber, corresponding to the velocity of the air flow in the mixing chamber. To determine the optimum spraying condition and output the optimum spraying condition signal, and the spraying of the fuel fine particles with the optimum spraying condition signal output from the optimum spraying condition determining means as an input. A spraying condition control means for controlling the conditions, and a combustion device. 8. An atomizer for atomizing and spraying liquid fuel, a mixing chamber for mixing the fuel sprayed from the atomizer with an air stream flowing in a predetermined direction, and a fuel and air formed in the mixing chamber. In a combustion apparatus including a combustion chamber for jetting and combusting the mixture of, the velocity of the fuel particles sprayed from the atomizer and the velocity of the air flow in the mixing chamber corresponding to the intensity of combustion vibration in the combustion chamber. Of the fuel particles by inputting the optimum spraying condition signal output from the optimum spraying condition judging means for judging the spraying condition such that the ratio is optimum and outputting the optimum spraying condition signal. A spraying condition control means for controlling the conditions, and a combustion device. 9. The combustion device according to claim 6, wherein at least one of the atomizers is supplied with atomizing air having a pressure higher than that of an air flow flowing through the mixing chamber. Combustion device characterized by being. 10. The combustion apparatus according to claim 9, wherein the optimum spray condition determination means is means for selecting a flow rate ratio between the fuel supplied into the atomizer and the atomizing air. apparatus. 11. The combustion device according to claim 9,
The combustion apparatus, wherein the optimum spraying condition signal is a signal indicating a flow rate ratio of the fuel supplied into the atomizer and the atomizing air. 12. The combustion device according to claim 9,
The combustion apparatus, wherein the optimum spraying condition signal is a signal indicating a flow rate of the atomizing air supplied into the atomizer. 13. The combustion device according to claim 9,
The combustion apparatus, wherein the spray condition control means is means for controlling a flow rate of the atomizing air supplied into the atomizer. 14. The optimum spraying condition determination means is a program that represents the relationship between the load of the combustion device and the optimum flow rate ratio of the fuel supplied into the atomizer and the atomizing air, which is determined according to the load. The combustion device according to claim 9, wherein the combustion device is provided inside. 15. A program representing the relationship between the flow rate of the air flow in the mixing chamber and the optimum flow rate ratio of the fuel to be supplied into the atomizer and the atomizing air, which is determined according to the flow rate. The combustion apparatus according to claim 9, which is provided in the spray condition determination means. 16. A means for measuring the time fluctuation of the pressure in the combustion chamber, a means for frequency-analyzing the time fluctuation of the pressure and outputting the strength of the combustion vibration, and the combustion vibration strength having a predetermined allowable value. 16. The combustion apparatus according to claim 6, further comprising: a means for increasing a flow rate ratio between the fuel supplied into the atomizer and the atomizing air when the flow rate exceeds the above. 17. A combustion apparatus according to claim 6, an air compressor for supplying compressed air to the combustion apparatus, and a combustion gas discharged from the combustion apparatus. A gas turbine power generation facility including a gas turbine and a generator driven by the gas turbine.