JPS6122106A - Gas turbine conbustor - Google Patents

Abstract

PURPOSE:To permit to keep a flame effectively and effect the lower NOx combustion in a combustion chamber at the head of a combustor by a method wherein fuel is injected at the position of an eddy flow area of head of the combustion chamber and after the air jetting portion from the outer wall of inner cylinder of the combustion chamber. CONSTITUTION:At first, the air 16 is introduced into the gap between an outer cylinder 1 and the inner cylinder 5 of a combustor, then, the air 10a, 11a, 12a, 13a, 14a, is introduced into a combustion chamber from the group of air leading holes which are provided at the wall surface of the inner cylinder 5, an inner cylinder cap 8 and inner cylinder cone 6. On the other hand, fuel 17 is fed to fuel injecting pipes 4a, 4b from the main body 3 of a fuel nozzle and injected into the annular combustion chamber 9 of an inner cylinder head from the nozzle 15 provided on each fuel injection pipe, then, igniting combustion is continued by the operation of a spark plug. According to this method, in the annular space forming the head combustion chamber, the fuel is injected effectively into the eddy flow and jet stream formed by the flowing air from the combustion head and annular inner cylinder side, therefore, the stable and low NOx combustion may be obtained by the combination of flame keeping under relatively lean condition and the fuel injection in the more leaned area.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to gas turbine combustors, in particular nitrogen oxides (
The present invention relates to the structure of a natural gas-fired low NOx combustor for the purpose of reducing NOx (hereinafter referred to as NOx).

[Background of the invention]

Methods for reducing NOx in gas turbine combustors can be roughly divided into wet methods that use water, steam, etc., and dry methods that are based on improving combustion performance. The former uses other media (water, steam, etc.), so there are factors that reduce turbine efficiency;
The latter combustion suppression method is superior to other methods, but because the objective is uniform low-temperature lean combustion, its combustion form is subject to extremely severe conditions such as an increase in CO generation in the direction of NOx reduction. .

In general, NOx generation during combustion is dominated by the combustion gas in the local high temperature area (1800 tZ' or higher) of the combustion area, and is mainly caused by the nitrogen content of unburned fuel exhaust and the oxidation of nitrogen in the combustion air. Occur. These are called Thermal A and Fuel A. In particular, Thermal stores are highly dependent on oxygen concentration and reaction time, and these phenomena are considerably influenced by gas temperature. Therefore, during the combustion process, localized high temperature regions are not formed and the temperature is uniformly lowered (approximately 15
00t:' or less), effective low NOx combustion will be possible.

Conventional combustion technology aimed at reducing NOx in gas turbines has a relatively large flow of air relative to the flow of fuel, and the air storage distribution within the combustion chamber can be selected with some degree of freedom. Lean diffusion combustion is the most advantageous. In particular, during combustion, the main objective is to achieve uniform low-temperature combustion by lowering the combustion temperature, promoting mixing, and shortening the NOx generation time.

As a means for realizing the above-mentioned combustion mode, a specific example of the conventional technology is shown in Japanese Patent Publication No. 55-20122, in which a plurality of fuel nozzles are arranged in an annular manner in a block-shaped combustion chamber, and the combustion chamber is It is constructed so that air, steam, etc. are introduced from the tip of an inner cylindrical cone provided at the center. The combustion mode of this combustor employs a combustion method that uniformizes the combustion temperature and lowers the gas temperature in the wake region of the combustion chamber by dispersing and supplying fuel in the cross-sectional direction of the combustion chamber.

In addition, a flame stabilizer that mainly uses air swirling flow is installed around the fuel nozzle, and its flame stabilizing mechanism does not stabilize the flame by the circulating flow region formed by the air swirling flow from the flame stabilizer. It is publicly known (Japanese Unexamined Patent Publication No. 57-202431). However, during combustion, relatively high-temperature gas is involved in the circulating flow region to maintain the flame near the fuel nozzle and stabilize it, so low NOx combustion provides a significant advantage.

In particular, a flame stabilizer with air swirling vanes requires a relatively high-speed air jet (V>39 m/s) due to its functional form (applicable range: Reynolds number e>ios). As a result of the shortened flame, rapid combustion is likely to occur near the fuel nozzle. Furthermore, the strength of the flame stabilization mechanism in the locally high temperature area within the circulating flow region, which is 1 to 2 times the diameter of the flame stabilizer, is conversely
It is a factor in the x generation mechanism. Therefore, even if fuel nozzles with conventional flame stabilizers are multiplied, it is not possible to achieve a significant reduction in NOx. Particularly in the case of sushi oxygen combustion, the flame holding mechanism that is advantageous for reducing NOx is not reliable, and the combustion form is greatly influenced by the flame holding characteristics. The present invention relates to a more effective low NOx combustor that compensates for the above-mentioned drawbacks.

[Purpose of the invention]

An object of the present invention is to provide a gas turbine combustor that enables effective flame stabilization in the head combustion chamber of the combustor to achieve lower NOx combustion.

[Summary of the invention]

Generally, the combustion state within the combustor is controlled by the -order combustion region, and the basis thereof is the flame holding mechanism. That is,
In the case of diffusion combustion aimed at low NOx combustion, the flame structure near the fuel nozzle is formed long and thin.
It is necessary to perform slow combustion that is effective in reducing NOx. Especially at the beginning of combustion, the combustion form differs depending on the concentration field of fuel and air. Therefore, if the fuel injection method that matches the air flow conditions during the combustion process allows for flame separation and combustion on the lean side, it is possible to create a combustion form that is advantageous for reducing NOx. can.

The present inventors have developed a fuel nozzle for the purpose of flame holding and a low NO
It was confirmed that by separating the fuel nozzle that mainly uses x-fuel, it is possible to perform stable lean combustion in a relatively narrow combustion chamber space. First, air is jetted from near the center of the combustor head to form a vortex around the outer periphery of the combustion chamber head. Combustion air is jetted from the outer wall of the inner cylinder near the head of the combustion chamber toward the center of the combustion chamber to strengthen the vortex flow. Fuel is injected into this vortex region for the purpose of flame stabilization. In particular, when fuel is injected into the vortex region, there is a difference in fuel concentration in the vortex region depending on the injection position, and by suppressing this fuel concentration, flame holding on the relatively lean side becomes possible. The most effective way to inject fuel to reduce NOx is to inject the fuel at a position after the air jet from the outer wall of the cylinder in the combustion chamber, and since the combustion mode is relatively lean, it is not necessary to inject fuel over a wide range. It is possible to achieve low NOx.

Therefore, the above-mentioned fuel injection method for flame holding and low NOx
By effectively combining the fuel injection method with combustion, it becomes possible to establish stable and low NOx combustion.

[Embodiments of the invention]

A specific embodiment of the present invention is shown in FIGS. 1 and 2. FIG. In a gas turbine combustor composed of a combustor outer cylinder 1, an end cover 2, a fuel nozzle main body 3, a fuel injection pipe 4, an inner cylinder 5, an inner cylinder cone 6, and a spark plug 7, an inner cylinder is installed at the head of the inner periphery 5. A cylinder cap 8 is installed, and a tapered inner cylinder cone 6 is protruded concentrically from the upstream end of the head to the downstream side with a gap on the inner circumferential side corresponding to the inner cylinder 5. An annular combustion chamber 9 is formed near the head. Further, a first stage combustion air introduction hole group 10 is provided on the head wall surface side of the inner cylinder 5, and a second stage combustion air introduction hole group 11 and an inner cylinder cooling hole group 12 are provided on the downstream side thereof. ,
A plurality of air introduction holes 13 are provided in a ring shape on the wall surface of the inner cylinder cap 8 corresponding to the annular combustion chamber 9. Furthermore, the inner cylinder cone 6
A group of cooling holes 14 is also installed on the wall surface of. Fuel nozzle body 3
is fixed to the end cover 2, and a fuel injection pipe 4 extending from the fuel nozzle body 3 passes through an air introduction hole 13 provided in the inner cylinder cap 8 and projects into the annular combustion chamber 9. A nozzle hole 15 is provided near the tip of the fuel injection pipe 4 to inject fuel toward the inner cylinder 5 and the inner cylinder cone 6.
The air introduction hole 13 provided in the inner cylinder cap 8 is larger than the outer wall of the fuel injection pipe 4 and installed with a gap provided therebetween. Also,
As shown in FIG. 3, the fuel injection pipe 4 is constructed by alternately combining long fuel injection pipes 4a and short fuel injection pipes 4b to change the position at which fuel is injected into the combustion chamber. For example, when the fuel injection position is based on the first stage combustion air introduction hole group 10, the fuel injection pipe 4a is downstream of the air introduction hole group 10, and the fuel injection pipe 4b is the same or upstream. It is configured so that fuel can be injected to the side.

Next, we will discuss the operating status of this combustor. First, the air 16 is introduced into the gap between the combustor outer cylinder 1 and the inner cylinder 5, and the air 10a, lla is introduced from each air introduction hole group provided in the wall surface of the inner cylinder 5, the inner cylinder cap 8, and the cylindrical cone 6.

12a, 13a, and 14a are introduced into the combustion chamber.

Meanwhile, the fuel F is removed from the fuel nozzle body 3 through the fuel injection pipe 4a.
, 4b, etc., and injected into the inner cylinder head annular combustion chamber 9 from the nozzle holes 15 provided in each fuel injection pipe, and the ignition plug 7 is operated to continue ignition combustion.

The feature of this combustor is that in the annular space forming the head combustion chamber, fuel is effectively injected into the vortex and jet stream formed by the air flowing from the combustion head and the annular inner cylinder side. The combination of flame holding under target lean conditions and fuel injection in a more diluted region achieves stability and low NOx.

FIGS. 4 and 5 show an example of the flow pattern of air and fuel near the head of the combustion chamber, which illustrates the key points of the present invention. The solid line in the figure represents air flow, and the chain line represents fuel flow.

Air flowing through the gap formed by the air introduction hole 13 provided in the cylindrical cap 8 of the head combustion chamber and the fuel injection pipe 4 flows along the fuel injection pipe, and is caused by the pressure difference between the jet and the space. The effect of backflow occurring in the internal and external directions, and a relatively weak vortex is formed around the upstream side of the fuel injection pipe. This vortex is further strengthened by a backflow component caused by an air jet from the outer wall of the cylinder 5 in the combustion chamber. In the air flow state, when the fuel is injected into the upstream part of the first stage air introduction hole 10 (L□>LF) through the fuel injection pipe 4, a large amount of fuel is drawn into the vortex region, and the fuel concentration is high. Become. In addition, after the air jet flowing through the air introduction hole 10 provided on the outer wall of the cylinder in the combustion chamber (LA<
When the fuel injection position is set at LF), the amount of fuel flowing into the vortex region A formed upstream of the fuel injection pipe becomes extremely small.

It has become clear that this difference in fuel concentration in the vortex region has a significant effect on flame holding performance and combustion characteristics.

FIGS. 6 and 7 show experimental results regarding flame stabilization and combustion characteristics depending on the protrusion length LF of the fuel injection pipe 4 from the inner cylinder cap 8. In terms of flame holding stability, the shorter the fuel injection pipe Lr is, the better it is, but the amount of NOx generated tends to increase. Furthermore, if the fuel injection pipe is lengthened, NOx will be reduced, but the amount of unburned emissions such as Co will increase and flame holding stability will also decrease.

On the other hand, in the structure of this combustor, the length of the inner cone constituting the combustion chamber, the position of the air introduction hole, etc. are other factors that greatly affect the combustion characteristics.

First, the air introduction hole provided in the combustion chamber head inner cylinder cap is
Even if multiple fuel injection pipes are installed around the fuel injection pipe, or if they are introduced from the inside and outside positions of the combustion chamber, the vortex region that is formed inside the combustion chamber will not be obstructed, but on the contrary, it will be possible to achieve the purpose as long as it is a means to strengthen it. . Particularly in this configuration, the position of the first stage air introduction hole is a factor that determines the size and strength of the vortex region, and has a great influence on flame holding performance. Figure 8 shows the flame blowout characteristics when the fuel injection position is constant at the distance LA from the width LC of the inner cylinder cap forming the head of the combustion chamber to the air introduction hole of the first stage on the downstream side. . Applicable range LA/: [1c=0.6 to 1.7, LA/
L c (In the case of 0.6, the vortex region that contributes to flame stabilization is reduced, and combustion becomes unstable due to dilution of the mixture due to air flow from the surroundings, lowering of combustion temperature, etc.)
．． If it is less than 5, it will be impossible to start ignition. Also, LA/
When L c (1,7), the vortex region is apparently enlarged, but a dead space is formed in part, and this region becomes a local high temperature area, which is disadvantageous in the direction of reducing NOx.

In particular, the flame holding mechanism in main combustion continues combustion by combustion products (high temperature gas) drawn in from downstream to upstream by the flow of air flowing in from the surroundings of the flame generated near the fuel injection hole of the fuel injection pipe. It plays an important role in stabilizing the flame.

Next, we will discuss the length of the protrusion of the inner cylinder cone and fuel injection pipe installed in the center of the inner cylinder. The role of the inner cylinder cone is to create a structure that makes it difficult for a high-temperature combustion zone to occur in the center of the combustion chamber than when there is no inner cylinder cone, and to form an annular combustion chamber, which naturally facilitates the dispersed injection of fuel. As a result, the mixture of air and fuel flowing in from the inner cylinder wall is promoted, and combustion is performed on a relatively lean side, which is advantageous for reducing NOx without causing extreme local high temperatures. combustion can be achieved. FIG. 9 shows the relationship between the inner cylinder cone length LII and the NOx emission concentration with respect to the maximum fuel injection pipe protrusion length Ly. When the length Lm of the inner cylinder cone increases, N
The amount of oz generated tends to decrease, but if the length is too long, the amount of air flowing toward the head combustion chamber will decrease, and the wall surface cooling of the inner cylinder and inner cylinder cone near the head will decrease, causing a drop in metal temperature. This is a disadvantage in terms of reliability. On the other hand, if the inner cylinder cone L1 is shortened, fuel and air will not mix well,
During the combustion process, as the combustion chamber expands from an annular combustion chamber to a cylindrical combustion chamber, the pressure difference between the inside and outside of the inner cylinder increases, resulting in an area where a large amount of air is introduced, and combustion progresses rapidly near the tip of the inner cylinder cone. This appears as an increase in the amount of NOx produced. Therefore, the applicable range of the inner cylinder cone is Lll/L
It is necessary to use it with F=2.0 to 5.0.

FIG. 10 shows a specific example of the state of air flow in the vicinity of the head of a combustion chamber that has the functions of each part of the present invention. The amount of air introduced is set so that it always falls within the flammable range during low-load and high-load combustion during gas turbine operation. The air introduction holes provided in the head inner cylinder cap account for 8 to 20% of the total air amount in the primary combustion area of the combustion chamber, and the air introduction holes for combustion in the first stage account for 10 to 23 percent, and are installed downstream of the air introduction holes for the first stage. The ratio of the amount of combustion air in the primary combustion area of the second and third stages is 5.
It is best to distribute it between 7 and 82 inches. In particular, in the head of this combustion chamber, the correlation between the amount of air from the air introduction hole installed in the inner cylinder cap and the amount of air from the first stage combustion air introduction hole creates a vortex region formed in the head combustion chamber. Since it controls the strength, etc., if it is outside the lower limit mentioned above, the flame holding performance will deteriorate mainly due to a decrease in the vortex strength. Furthermore, at low load combustion, the stoichiometric mixture ratio (λ=1.0) shifts to a fuel surplus direction, and at high load, it goes outside the flammable range, making good combustion impossible. On the other hand, when the upper limit is exceeded, the theoretical mixing ratio (λ = 1
．． 0), so there is no problem with overflow, but since the combustion is relatively lean at low loads, flame holding becomes unstable. Therefore, during combustion, it is necessary to operate with the air amount distribution described above.

The characteristics of each element of the present invention have been described above, but the fuel supply means, which is the most important in the present combustor configuration, will be explained next. First, to explain the above-mentioned embodiment, the short fuel injection pipe for flame stabilization protrudes to the vicinity of the first stage's combustion blast introduction hole, and the fuel injection pipe for mainly combustion is located at the first stage. It has a length 1.5 times longer than the position of the air introduction hole, and fuel injection pipes for flame stabilization and combustion are arranged alternately in the annular direction at a pitch that is approximately the same as the length of the protrusion for flame stabilization, The fuel injection direction of each injection pipe is configured to be introduced substantially perpendicularly to the axis of the combustion chamber. The combustion form of this combustion method is that the flame for the flame holding zone and the flame for combustion are formed apart in the axial and annular directions within the combustion chamber, so the flame dispersion effect results in a uniform low temperature direction for low NOx combustion. It is possible to achieve combustion close to that of As a means of making this combustion form more effective, it is possible to obtain even better performance by spacing the fuel in the axial and annular directions closer together (multi-staged fuel injection pipes), but the size of the combustor etc., are restricted from the shape. In addition, localized temperature increases occur due to flame interference.

On the other hand, if the number of fuel injection pipes is reduced, the fuel dispersion effect will be lost, making it impossible to achieve low NOx combustion. Therefore, as shown in the embodiments of the present invention, the divided introduction mechanism has three to four stages in the axial direction within the area corresponding to the amount of air flowing from the head of the combustion chamber and the amount of air from the combustion air introduction hole of the first stage. It is important that the flames are arranged in an annular direction at such intervals that the flames do not interfere with each other.

FIG. 11 shows a structure in which a single fuel injection pipe 4C has fuel injection holes 4d and 4e for flame stabilization and combustion. FIGS. 12(a) and 12(b) show an application example in which the fuel injection pipes 4f, 4g, 4h, and 4i protrude from the inner cylinder side or the inner cylinder cone side.

As described above, the present invention was established by clarifying the functions and effects of individual elements, and relates to a low NOx combustor that is the basis of lean, low-temperature combustion.

〔Effect of the invention〕

According to the present invention, a mechanism for injecting fuel for the purpose of flame stabilization into a vortex region formed by an air jet at the head of the combustion chamber and an air jet from the outer wall of the inner cylinder through a protruding fuel injection pipe, combustion air, etc. It has a function to inject fuel into the wake side where the combustion chamber is introduced, and by arranging the flame holding means and the fuel supply means to the lean side in an annular combination, it is possible to spread the fuel in the circumferential direction and the axial direction of the combustion chamber. As a result, an extremely high temperature region is not formed within the combustion chamber, and as a result, combustion for reducing NOx is extremely effective.

FIG. 13 shows an example of combustion test results with the combustor structure of the present invention. Compared to the conventional multi-burner combustion method that uses an air swirling flame stabilizer in an annular combustion chamber, it is expected that the NOx reduction rate can be improved by 30% at the gas turbine rating. Furthermore, we were able to confirm flame holding stability and stable combustion within the gas turbine load operating range.

Therefore, the present invention can provide a highly reliable low NOx combustor structure that achieves stable combustion as a gas turbine combustor.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of the combustor head of the present invention, FIG. 2 is a front view of FIG. 1, FIG. 3 is a three-dimensional view of the combustor head showing the arrangement of fuel injection pipes of the present invention, and FIG. Figure 4. Figure 5 shows the flow pattern of air and fuel at the head of the combustion chamber, Figure 6 shows the flame holding characteristics depending on the length of the protrusion of the fuel injection pipe, and Figure 7 shows the NOx, 00
Figure 8.9.10 shows the characteristics of each part, 11th and 12th
The figure shows another application example, and Fig. 13 shows the NOx concentration curve in the gas turbine operating range. 4...Fuel injection pipe, 4a...Fuel injection pipe, 4b...
・Fuel injection pipe, 6... Inner cylinder cone, 9... Annular combustion chamber, lO... First stage combustion air introduction hole, 13...
・Air introduction hole. 't11 Fig. 12 Fig. 13 Fig. ￥4121 Diagram on grass 'X' 7 Fig. 11 Hair tint's fusion seal (dragon) LA/L (:) white dew length 1〃odon-1j dimension tube
<te+/lp) ¥/2 Fig.- → Furnace i Nitrogen direction from the top □J giant (m>η) γ11
Figure χ12 Figure (6L) )X /2 Figure t is no

Claims (1)

[Scope of Claims] 1. An inner cylinder cone is installed so that the combustion chamber at the head of the inner cylinder inside the combustor outer cylinder is formed into an annular shape having a double cylindrical wall, and the annular space combustion chamber is The first stage combustion air is introduced almost perpendicularly to the downstream side by providing a plurality of air introduction holes in the inner cylinder cap portion, which has a head portion and a side closed end portion, corresponding to the air introduction holes. A hole is installed to fix the fuel nozzle main body to the center of the end cover that closes the outer cylinder side, and a fuel injection pipe connected from the fuel nozzle main body is passed through the air introduction hole of the inner cylinder cap. A gas turbine combustor characterized in that a plurality of fuel injection pipes are arranged in an annular manner and protrude in a combustion chamber, and fuel is injected and supplied from near the tip of a fuel injection pipe to maintain a flame on the upstream side of the fuel injection pipe. . 2. In claim 1, the air introduction hole is introduced around the fuel injection pipe from the inner cylinder cap part forming the head annular combustion chamber, and the first stage is introduced from a substantially perpendicular direction to the wake side. The position of the second combustion air introduction hole is determined by the ratio of the gap length L_C of the inner cylinder cap portion of the head annular combustion chamber to the first stage combustion air introduction hole position L_A, L_A/L_C=0.
The length of the inner cylinder cone L_B is set within the range of 6 to 1.7, and the length L_B of the inner cylinder cone is determined relative to the maximum length of the fuel injection position introduced via the fuel injection pipe.
/ A gas turbine combustor characterized in that the fuel injection position L_F is configured to be in a range of 2.0 to 5.0. 3. In claim 1, the air amount distribution in the primary combustion region of the combustion chamber is 8 to 20% from the air introduction hole provided in the head inner cylinder cap, and the first stage combustion air is introduced. A gas turbine combustor characterized in that the holes perform combustion in the range of 10 to 23%, and the combustion air amount in the second stage and subsequent stages installed downstream thereof is in the range of 57 to 82%. 4. A gas turbine combustor according to claim 1, characterized in that the fuel injection protrusions are arranged in combinations having different lengths to change the fuel injection position into the combustion chamber. 5. In claim 1, the fuel injection pipe is protruded upstream and downstream from the first-stage combustion air introduction hole which is installed on the downstream side of the cylinder cap part of the annular combustion chamber. A gas turbine combustor characterized in that it is configured to inject and supply fuel into a combustion chamber through a combination arrangement. 6. Claim 1 describes that the injection hole section provided near the tip of the fuel injection pipe protruding into the annular combustion chamber is installed in a direction substantially perpendicular to the axis of the combustion chamber to inject and supply fuel. Characteristic gas turbine combustor.