JPS59202324A - Low nox combustor of gas turbine - Google Patents

Abstract

PURPOSE:To reduce NOX generated by providing a hollow cylindrical member in the vicinity of the upstream of an inner cylinder at the head portion of a combustion chamber, igniting the fuel by the tip end of the cylindrical member and igniting a gaseous mixture introduced from a cylindrical gap between an inner cylinder and the hollow cylindrical member. CONSTITUTION:The gaseous mixture of the fuel injected from a nozzle 3 by an ignition plug 7 inserted into the vicinity of the fuel nozzle 3. With the rise of the combustion intensity, the fuel 29 is injected from a fuel header 14 and a pipe 16 into an annular hollow part 13, and is mixed with an air current 31 and is rotated and jet-streamed within a pre-mixing chamber 11. At the time of a high intensity combustion, further a fuel 32 is injected through a header 20 into an annular hollow part 23, and mixed with an air current 34 and introduced into a main combustion chamber 8 through an annular swirler 18. This gaseous mixture is ignited by a flame of the nozzle 3. By supplying to burn a premixed gas in two stages in correspondence to the load, the flame stability of the fuel nozzle can be improved and generation of NOX can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a combustor for a gas turbine that is improved to reduce the generation of NO.

[Background of the invention]

Conventionally used methods for reducing NO, tl in gas turbine combustors can be roughly divided into (
There are (a) a wet method that uses water, steam, etc., and (b) a dry method that is based on improving combustion performance.

Since the wet method described in item (a) above uses a medium such as water or steam, there is a risk of reducing turbine efficiency.

Further, the dry method described in item (b) above suppresses the generation of NO by performing lean combustion at a uniform temperature, and is subject to extremely strict conditions regarding the combustion form.

The principle of NO reduction in the above dry method will be briefly described below.

In general, NOx generation during combustion is dominated by the combustion gas in the local high-temperature area (over 1800 tons) 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 NO and 7-well NO. In particular, thermal NO is highly dependent on oxygen concentration and reaction time, and is strongly influenced by gas temperature. Therefore, if uniform low-temperature combustion (1500 U or less) is achieved in which no local high-temperature regions are formed during the combustion process, effective low-NO and chemical combustion will be possible.

Conventionally, combustion technology aimed at reducing NO in gas turbines is a lean diffusion combustion method in which excess air is introduced into the combustion region, and air, water, or steam is introduced into local high-temperature areas to suppress the high-temperature areas. Measures are being taken to do so. In particular, with this type of combustion, combustion continues while the fuel diffuses and mixes with the air, making it difficult to generate a homogeneous combustible mixture.During the combustion process, the fuel becomes concentrated, resulting in locally high temperature areas. In addition, the introduction of excess air, water, and steam can supercool the flame surface, increase unburned emissions such as co, and cause unstable combustion.If P1 water is introduced, the turbine efficiency This is a factor in the decline in therefore,
In order to ideally suppress the production of NOx and CO through only the combustion mode, it is necessary to thoroughly mix the fuel and air before combustion, and to perform specific soft low-temperature combustion with a uniform flame temperature. becomes.

Conventionally, as a means of achieving a uniform and low-temperature combustion mode as described above, the fuel and air are completely mixed (premixed) in the process of introducing the air into the combustion chamber, and then the air is introduced into the combustion chamber. The structure that enters is used. It is also conceivable to provide a mixing chamber in a part of the combustion chamber to perform the above-mentioned premixing, and to suppress the generation of flame as much as possible in this region to achieve uniform, low-temperature combustion.

However, if the above-mentioned premix combustion LRT technology is attempted, there is a risk of flashback occurring in the premix chamber, and in addition, unburned emissions such as CO will be generated due to the dilution of the premix mixture. It is unavoidable that the generation and flame holding stability deteriorate and a region where combustion oscillations occur is formed. In particular, in a gas turbine combustor, air is introduced based on the pressure difference between the inside and outside of the combustion chamber, and the combustion load control is performed based on the amount of fuel introduced for a constant amount of air in each combustion chamber. The big challenge is how to solve these problems.

To explain the above problem with a specific example of a combustion device in the prior art, a mixing chamber is installed in a part of the combustor,
If a fuel nozzle is placed on the downstream side of the fuel nozzle and the premixing chamber is partially constricted as a backfire prevention structure, then: Therefore, in a region where the fuel flow rate is low, the fuel becomes extremely lean, and in order to maintain stable combustion, it becomes necessary to apply a large combustion load to the fuel nozzle provided further downstream. This is a disadvantageous condition for reducing NO.

II) If an attempt is made to adopt a combustion mode that takes into account ignition start-up within the premixing chamber, partial unstable combustion will occur within the operating region, causing combustion oscillations, and if the combustion chamber is independent, ignition will occur. When flame propagation involves difficult technical problems.

(2) Since the above-mentioned throttle structure concentrates the flame in the center of the combustion chamber, a localized high temperature is generated in the flame concentration area, which hinders the reduction of NO.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a premixing type gas turbine combustor that can reduce the generation of NO.

[Summary of the invention]

In order to completely reduce NO by premix combustion, it is necessary to have a premixing mechanism that can perform effective premixing, a combustion mechanism that can perform stable combustion, and a combustion mechanism that can prevent backfire. Prevention measures are necessary.

In order to achieve the above object based on the above considerations, the present invention provides a hollow conical member inside near the upstream end of the inner cylinder at the head of the combustion chamber, and provides fuel at the downstream end of the hollow conical member. A nozzle is provided, an ignition plug is provided near the fuel nozzle,
An air and fuel supply means is provided at the upstream end of the cylindrical gap formed between the head inner cylinder and the hollow conical member, and the combustible material formed by the supplied air and fuel is provided. The percentage indicates that the air-fuel mixture can be ignited by the flame of the fuel nozzle.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

Fig. 1 is a longitudinal sectional view of an embodiment of the gas turbine low NO combustor of the present invention, Fig. 2 is a sectional view of A and -A in Fig. 1, and Fig. 3 is a cutaway near the head of the combustor. FIG.

1 is a combustor outer cylinder, 2 is an end cover fixed to the electrical diagram on the upstream side, 3 is a fuel nozzle, 4 and 5 are fuel introduction mechanisms, 6
is an inner cylinder, 7 is a spark plug, and each of the above members is a component of the combustor.

The head of the inner cylinder 6 (on the upstream side with respect to the combustion gas flow, the first
The cylindrical main combustion chamber 8 (left side in the figure) has a smaller cross-section than the cylindrical main combustion chamber 8 provided at the rear, and the outer frame is formed by an inner cylinder wall 9 whose cross-section gradually decreases in the direction of the head. A premixing chamber in which a tapered cylindrical cone portion 10 is protruded concentrically on the downstream side with a gap on the inner circumferential side corresponding to the inner cylinder wall 9, and a widening space is formed in the inner cylinder head. 11 Complete formation. Further, a fuel nozzle 3 having a swirler is disposed at the downstream end of the cylindrical cone portion 10, a first-stage current swirler 12 is attached near the head of the premixing chamber 11, and an annular swirler is installed at the upstream end of the fuel nozzle 3. An annular hollow part 13 is formed by extending the entire inner and outer frames of the effective opening of the container 12, a circular annular fuel ivy part 14 is provided on the outer circumferential side, and a fuel injection hole 15 is provided in the annular hollow part 13. pipe 16 (
(Fig. 3) are provided protrudingly from a large number to constitute the fuel introduction mechanism 4.

In this embodiment, as described above, the upstream of the inner cylinder at the head of the combustion chamber, =
, a hollow conical member is provided inside near Mt, a fuel nozzle is provided in all stages at the downstream end of the hollow conical member, a spark plug is provided near the fuel nozzle, and the head inner cylinder and An air and fuel supply means is provided at the upstream end of the cylindrical gap formed between the hollow conical member and the combustible mixture formed by the supplied carbon dioxide and fuel. A fuel nozzle is provided on the downstream side, and the premixed combustible mixture can be ignited by the flame of the fuel nozzle.

In this embodiment, a second-stage annular swirler 18 is further provided in the inner cylinder enlarged portion 17 connected to the main combustion chamber 8 near the outlet of the premixing chamber 11.
As described above, the annular hollow part 19 is formed in the effective opening on the upstream side of the annular swirler 18, and the ivy part 20 is attached to the outer circumference of the annular fuel pipe 22 having the fuel injection hole 21. A large number of protrusions are provided in the annular hollow portion 23 to form the fuel introduction mechanism 5. On the other hand, the downstream cross section of the main combustion chamber 8 of the inner cylinder is formed by a reduced cylinder, and the dilution air hole 25 is installed in the reduced cross section 24 near the rear of the inner cylinder.

Next, a method of operating the gas turbine combustor configured as above and its effects will be explained.

The ignition plug 7 is attached to the tip of the cylindrical cone part 10 from the outer frame part of the outer cylinder 1 and inserted to the vicinity of the fc fuel nozzle 3. At the beginning of combustion, the fuel 26 is guided to the fuel nozzle 3 via the fuel introduction pipe 27, and the surrounding It is introduced into the combustion chamber along with the air flow 28 introduced from the ignition plug 7, and ignited by the spark plug 7 described above. In addition, as the combustion load increases, the fuel 29 is guided through the entire fuel introduction pipe 30 to the ivy part 14, and is jetted from the jet hole 15 of the fuel pipe 16 into the annular hollow part 13 and mixed into the air flow 31. Then, the annular swirler 12 swirls the jet into the premixing chamber 11 . During high-load combustion, the fuel 32 is further ejected from the fuel introduction pipe 33 through the ivy part 20 and through the jet hole 21 of the pipe 22 protruding into the annular hollow part 23, and the air flow 3
4, the annular swirler 18 transforms the fuel into a swirling jet and introduces it into the main combustion chamber 8 to continue combustion.

In this embodiment, cooled fresh air 35 is supplied to the inner cylinder wall 9 of the premixing chamber and the wall surface of the main combustion chamber 8, and diluted air 37 is supplied near the downstream.
A mechanism for introducing the outer cylinder 1 and the inner cylinder 6 is provided respectively.
A portion of the air 36 flowing through the gap is guided into the combustion chamber.

FIG. 4 shows an example of fuel control in the gas turbine low NO combustor of this embodiment. In the figure, Fl is the inner cylinder cone part 1
The fuel flow rate to the fuel nozzle 3 installed at the tip of the engine operates from the time of ignition to near no-load. F2 is the amount of fuel introduced into the first stage annular swirler 12, which allows the turbine to operate at a partial load, and F3 is the fuel flow rate to the second stage annular swirler 18, which operates in a high load region.

That is, in the present invention, in the combustion method, the fuel nozzle 3 provided in the center of the combustion chamber constantly generates a flame, and the first and second stage annular swirlers 1 are operated in response to changes in load.
One of the features is that the premixture from No. 2 and 16 can be stably combusted. Therefore, flame holding stability of the fuel nozzle 3 is an important factor. Therefore, from the viewpoint of flame stability, the fuel nozzle 3 creates a state in which the mixture of fuel and air is not good in all parts, and forms a region (stoichiometric mixture ratio) with high combustibility generated by the concentration difference in the combustible mixture. Perform combustion to create a diffusion flame. However, since local high temperature areas are generated during the combustion process, it is desirable to reduce the amount of combustion as much as possible in order to reduce NO.

FIG. 5 shows a specific example of the fuel nozzle 3. The fuel 26 is introduced through the fuel introduction pipe 27 and is jetted against the swirling air flow through a fuel injection hole 38 provided in the swirler portion of the fuel nozzle 3 . In addition, the inner cylinder cone part 1 is tilted at an angle θ from the outer circumferential side of the swirler.
A flame stabilizing tube 39 is installed which is thicker than the tip of the flame stabilizing tube 39 and is formed to protrude into the premixing chamber 11, and cooled fresh air 40 is inserted along the wall surface of the flame stabilizing tube 39. The flame stabilizing cylinder 39 is designed to allow stable combustion of the combustible mixture from the fuel nozzle 3 without being directly influenced by the surrounding flow state (particularly the flow from the premixing chamber). By improving flame holding stability, the amount of combustion dedicated to the pilot flame can be reduced, and in addition, the flame holding tube 3
Flow 41 of a part of the combustible mixture generated in the downstream part of 9
This can be expected to improve the heat transfer.

As explained above, if the fuel nozzle 3 is configured to be surrounded by the flame stabilizing tube 39 and the tip J of the cross-sectional shape of the flame stabilizing tube 39 is also made thick, flame stabilization is achieved. Improving gender has a positive effect.

Next, as a means to prevent flashback of the combustible premixture e flowing from the first stage stage converter, the shape of the premixing chamber 11 is introduced downward, so that the flow velocity of the premixer flowing inside is reduced in the second flow direction. Make it flow. In other words, if the flow velocity is fully set under flashback conditions in the vicinity of the outlet of the premixing chamber 11, it is possible to prevent unexpected sudden flashbacks due to flame radiation, etc. occurring on the downstream side.

As in this embodiment, there is a first
A step annular swivel is provided, and the front! A swirler is provided at the tip of the fuel nozzle, and the cylindrical gap is formed so that its cross-sectional area expands toward the downstream side to form a head premixing chamber, and the combustion chamber The part of the head inner cylinder facing the hollow conical member is widened in a step-like manner most downstream to form a cylindrical main combustion chamber, and the premixing chamber and the king combustion straw are connected to each other. Boundary property 1 By installing a second-stage annular swirler nearby and combining it with the multiple annular swirler structure centered around the combustion nozzle, Mr.
It is particularly effective in preventing flashback.

) of the gas turbine low NO, combustor of this example,
1. Another feature other than the above is a premixing mechanism for air and fuel. In the process of introducing fuel into the annular hollow space into which the air flow shown above flows, a large number of nozzle ribs are protruded, and one or more fuel injection holes are provided in the nozzles to inject the air. By dispersing and supplying air into the fuel flow, effective mixing is possible even when the air is flowing at a low speed.In particular, installing a swirler in the upstream part of the premixing chamber increases the diffusion area of fuel and air in the premixing chamber. and promotes good mixing.

As in this example, a fuel introduction mechanism 4 as a fuel spraying means is provided in the first stage swirler 12 and the second stage swirler 18, respectively.
and 5 are effective for uniform combustion.

FIG. 6 is an enlarged view of the vicinity of the fuel introduction mechanism 4, and FIG. 7 is a sectional view taken along line BB in FIG. A fuel jet hole 15 is provided in a pipe 16 protruding from the fuel ivy 14, and turbulent flow members 42 and 43 are arranged in a staggered manner so as to face the jet hole 15, thereby forming a tile-like generating means. According to this example, the fuel can be mixed and diffused in a short space, and it is easy to construct a structure with relatively small pressure loss. Therefore, it is a very advantageous method as a means that requires a large amount of air from the opening. be.

FIG. 8 is an explanatory diagram showing the state of the flame generated in the embodiment of FIG. 1, where C is the pilot flame generated by the nozzle 3 equipped with a swirler, D is the flame generated by the premixture, and E is the fuel The flame is generated by the fuel supplied from the introduction means 5 and the air supplied from the second stage annular swirler 18.

〔Effect of the invention〕

As described in detail above, the low NO combustor of the present invention includes a hollow conical member provided inside near the upstream end of the inner cylinder at the head of the combustion chamber, and a downstream tip of the hollow conical member. A fuel nozzle is provided, an ignition plug is provided near the fuel nozzle, and air and fuel are introduced into the upstream end of the cylindrical gap formed between the head inner cylinder and the hollow conical member. means for igniting the combustible mixture formed by the injected air and fuel by the flame of said fuel nozzle, both in the radial and axial directions of the combustion chamber. No! Because it allows for uniform combustion and does not create localized high temperature areas. can reduce the occurrence of

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention, FIG. 2 is a sectional view taken along line A-A in FIG. FIG. 4 is a diagram showing an example of fuel control in the above embodiment, FIG. 5 is an enlarged sectional view of the nozzle tip, and FIG. 6 is a partially enlarged sectional view showing the vicinity of the fuel introduction mechanism. 7 is a sectional view taken along the line B-B in FIG. 6, and FIG. 8 is an explanatory diagram showing the state of flame generation in the embodiment of FIG. 1. 1... Combustor outer cylinder, 2... End cover, 3...
Fuel nozzle, 4, 5...Fuel introduction mechanism, 6...Inner cylinder, 7...Ignition plug, 8...Cylindrical main combustion chamber, 9...
- Inner cylinder wall, 1°...Cylindrical cone part as a hollow conical member, 11... Premixing chamber, 12... First stage annular swirler, 13... Annular hollow part, 20...・Fuel ivy part,
21...Fuel injection hole, 22...Pipe, 23...
Annular hollow part, 24... Reduced cross section part, 25... Dilution air hole, 26... Fuel, 27... Fuel introduction pipe, 28...
... air flow, 29 ... fuel, 30 ... fuel introduction pipe,
34... Air flow, 35... Cooling air, 36... Air, 3/7... Dilution air, 38... Fuel injection hole 139
...Flame-holding tube, 40...Cooling rush air flow, 41...Involving flow, House 3 Figure Condolence tJ-Figure 1 Nosfuhin'' (2) ``- Summer meeting B Continuation of page 1 0 Invention Yoshiyoshi Uchiyama, Hiroda -shi, Shintate -cho, Shinto -cho, Institute of Hitachi Machinery Institute, Institute, Machine Research Institute, Ritsuo Kuroda, Tsuchiura City, 502, Hitachi Machinery Institute, Katsuo Wada, Hitachi City, Hitachi City, 1st 1st. Number stock% formula% (

Claims (1)

[Claims] 1. A hollow conical member is provided inside the combustion chamber head inner cylinder near the upstream end, a fuel nozzle is provided at the downstream end of the hollow conical member, and a fuel nozzle is provided at the downstream end of the hollow conical member. A spark plug is provided nearby, and a means for supplying air and fuel is provided with a gold film at the upstream end of the cylindrical gap formed between the inner cylinder of the head and the hollow conical member,
A gas turbine low NO combustor, characterized in that a combustible mixture formed by introduced air and fuel can be ignited by the flame of the fuel nozzle. 2. The fuel nozzle provided in the hollow conical member shall be covered with a flame-holding tube, and the flame-holding tube shall be formed so as to have a cross-sectional shape that is larger than the tip of the hollow conical member. A gas turbine with low NO, combustor according to claim 1, characterized in that: 3. A first-stage annular swirler is provided near the upstream end of the inner cylinder at the head of the combustion chamber, the swirler is provided near the tip of the fuel nozzle, and the cylindrical gap is directed toward the downstream side. The head premixing chamber is formed by expanding the cross-sectional area of the head premixing chamber, and the combustion chamber head inner cylinder further expands in a stepwise manner on the downstream side of the part facing the hollow conical member. A cylindrical main combustion chamber is formed, and a second combustion chamber is formed near the boundary between the premixing chamber and the main combustion chamber.
2. The gas turbine low NO, combustor according to claim 1, characterized in that stages of annular swirlers are provided to form a multiple annular swirler structure centered around the combustion nozzle. 4. The gas according to claim 3, wherein the first stage annular swirler and the second stage annular swirler are each equipped with a fuel spraying means. Turbine low NO, combustor. 5. A patent claim characterized in that the fuel spraying means is provided with a turbulence generating means, and the turbulence generating means is arranged in a staggered manner with a plurality of turbulent flow members. The gas turbine low NO□ combustor according to item 4.