JP2651304B2 - Premix nozzle with diffusion pilot and gas turbine combustor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

This application is technically related to the applicant's U.S. Patent Application No. 501,439 (filed March 22, 1990) and U.S. Patent Application No. 934,885.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine combustor, and more particularly to an improvement in a gas turbine combustor for reducing air pollutants such as nitrogen oxides (NOx).

[0003]

BACKGROUND OF THE INVENTION In order to reduce the amount of NOx in the exhaust gas of a gas turbine, Wilkes and Hilt of the inventor have been employed.
Devised a two-stage dual mode combustor, which is assigned to the assignee of U.S. Pat. No. 4,292,801 (19).
Issued on October 6, 1981). In this patent,
If the two combustion chambers are set so that, under normal operating load conditions, the upstream primary combustion chamber functions as a premix chamber and the actual combustion takes place in the downstream second combustion chamber, It has been discovered that the amount of exhaust NOx can be significantly reduced as compared to a typical single stage single fuel nozzle combustor. Under the operating conditions described here, there is no flame in the primary chamber, which has led to reduced NOx formation. Under these operating conditions, the secondary or central nozzle provides a flame source for operating the combustor. In certain configurations of the patented invention,
An annular arrangement of a plurality of primary nozzles, each having a discharge port in the primary combustion chamber, and a central secondary nozzle having a discharge port in the secondary combustion chamber are provided. All of these nozzles have an axial fuel feed pipe, each nozzle is surrounded by an air swirler at the discharge end, and the air swirler supplies air for combustion to the discharge fuel from the fuel nozzle, It can be described as a diffusion nozzle.

[0004] In the aforementioned US Patent Application No. 501,439, we have developed a central or secondary nozzle design.
It has been discovered that NOx production can be further reduced by making modifications that can be referred to as premix / diffusion nozzles. In operation, a relatively small amount of fuel is used to hold the diffusion pilot while providing additional fuel from the premixing portion of the nozzle to ignite the main fuel supply sent from the upstream primary nozzle to the primary combustion chamber. I do.

In the foregoing invention, a premix swirler is located at the boundary of the secondary flame zone and serves to stabilize and hold the flame in various modes of operation. However, this premix swirler element is exposed to high flame temperatures that affect the life of the swirler.

[0006]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to rearrange the swirler so as not to come into direct contact with the flame while maintaining the overall structure of the nozzle of the prior application. That is, the present invention places the premix swirler upstream of the fuel injection point to prevent the swirler from directly contacting the flame under any operating conditions, thereby extending the life of the swirler.

[0007]

SUMMARY OF THE INVENTION The invention of the prior application is particularly suitable for gas turbine combustors of the type having two combustion chambers separated by a venturi throat region. Fuel is discharged from an annularly arranged primary nozzle to an upstream or primary combustion chamber. The method of operation requires that, under basic load, the primary nozzle flame be eliminated while a single center or secondary nozzle maintain the combustion of the premixed fuel from the primary nozzle. According to the invention, a single central or secondary nozzle, which was characterized as a diffusion nozzle, is replaced by a premix nozzle with a diffusion pilot,
This reduces the fuel flow to the central diffusion flame from about 20% of the total fuel flow to about 2% of the total fuel flow to the entire combustor. To accomplish this, an air feed pipe is positioned around the smallest fuel feed pipe to support diffusion flame combustion while maximizing fuel feed in the secondary nozzle through multiple radial fuel distribution tubes. The fuel is pumped from each of these tubes to a premixing chamber surrounding a diffusion pilot consisting of an axial fuel feed pipe and an air feed pipe surrounding it. In this way, the diffusion flame can ignite the center nozzle premix chamber stream using a relatively small amount of fuel, but the required amount ignites the main premix stream from the remaining surrounding primary nozzle. Significantly less than required for Therefore, this design simultaneously (NOx
Minimizing the proportion of the total fuel flow in the combustor burning as a (high emission) diffusion flame, but using a pilot premix flow (low NOx emissions) to ignite the main premix flow Sufficient heat input is obtained.

At the same time, the premix swirler element, which was previously located at the boundary of the secondary flame zone, is rearranged to a point upstream of the fuel injection point in the present invention. Specifically, the premix swirler is an integral part of the secondary fuel nozzle and is located behind or upstream of the radial fuel distribution tube. The swirler is constructed by arranging a series of vanes circumferentially at an angle to the axial centerline of the fuel nozzle.

[0009] In another embodiment, a venturi is provided at the discharge end of the secondary premix chamber to assist in stabilizing the secondary flame.

[0010] Other objects and advantages of the present invention will become apparent from the following detailed description.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view showing a gas turbine engine in a partial cross section. The gas turbine 12 includes a compressor 14, a combustor 16, and a turbine 18 represented by a single blade. Although not specifically shown, as is well known, the turbines are drivingly connected to the compressor along a common axis. The compressor 14 pressurizes the inlet air, and then turns or backflows the pressurized air to the combustor 16,
Here, air is used to cool the combustor and also to supply air to the combustion process. In the gas turbine, a plurality of combustors 16 (only one is shown) are arranged along the periphery of the gas turbine. In one example of a gas turbine, 16 such combustors are provided. Transition duct 20
Connects the outlet end 18 of each combustor to the inlet end of the turbine to deliver hot combustion products from the combustion process to the turbine.

The present invention is disclosed in US Pat. No. 4,292,80.
It is particularly useful for two-stage dual mode low NOx combustors of the type described in No. 1. As described in that patent and here, as shown in FIG. 2, each combustor 16 includes a primary or upstream combustion chamber 24 and a secondary or downstream combustion chamber 26 separated therefrom by a venturi throat region 28. And The combustor 16 is surrounded by a combustor flow sleeve 30 that directs compressor discharge air flow to the combustor. The combustor 16 is further surrounded by an outer casing 31 (FIG. 1) bolted to the turbine casing 32.

A plurality of primary nozzles 36 for supplying fuel to the upstream combustor 24 are arranged in an annular arrangement around a central secondary nozzle 38. In one example of a gas turbine, each combustor is provided with six primary nozzles and one secondary nozzle. As a summary of the combustor description, fuel is delivered to the nozzle through line 42 in a manner well known in the art and described in detail in the patent. Also, as is well known in the art, the primary combustor includes a spark plug 48 shown in FIG.
In the next combustor, ignition is performed by the crossfire tube 50, respectively.

US Pat. No. 4,292,801 states that the fuel nozzles are the same for both the primary and secondary nozzles, ie, that the nozzles are all diffuse. Referring to FIG. 2, the diffusion nozzle 36 includes a fuel feed nozzle 54.
And an annular swirler 56. The nozzle 54 delivers only the fuel, which is then mixed with the swirler air for combustion. According to the patent, the secondary nozzle is also a diffusion nozzle, which will be described later.

During basic load operation, the two-stage dual mode combustor is designed to operate in a premix (premix) mode. That is, all primary nozzles 36 merely mix fuel and air, and the fuel-air mixture is ignited by a diffusion flame supported by a secondary or central diffusion nozzle 38. As a result of this premixing of the primary nozzle fuel and ignition by the secondary diffusion nozzle, the NOx emissions of the combustor are reduced. However, the systems described above have at least one fundamental disadvantage. For example, in a laboratory test,
The ratio of fuel in the secondary nozzle is determined by NOx under certain operating conditions.
At the lowest value at which emissions can be minimized, the same low proportion of secondary nozzle fuel may not provide sufficient heat input to properly burn the main premixed stream under different operating conditions. ,all right.

The present inventors have disclosed US Patent Application No. 501,4.
In No. 39, it was found that by using a minimum diffusion pilot in combination with a central nozzle premix chamber, a suitable pilot flame for the main premix flow from the upstream premix (primary) nozzle 36 could be maintained. Therefore,
The present invention ensures sufficient heat input to ignite the main premixed stream using a premixed secondary or pilot stream, while at the same time providing a combustor in a combustor burning as a diffusion flame (high NOx emissions). Minimize the percentage of total fuel.

Referring to FIGS. 2 and 3, there is shown the premix (or secondary) nozzle 100 with diffusion pilot of our earlier application. This nozzle, also called a secondary nozzle, includes a diffusion pilot 62 having a fuel feed pipe 64. The fuel delivery pipe 64 includes an axial pipe section 66 and a plurality of closed-ended radial fuel distribution tubes 68 extending radially outward from the axial pipe section. In a preferred embodiment, six such fuel distribution tubes are provided. As is apparent from FIG. 3, each of the fuel distribution tubes 68 is provided with a plurality of fuel discharge holes or orifices 70 for sending the fuel downstream toward the discharge end of the dual-purpose nozzle. The fuel distribution holes are dimensioned to provide a desired rate of fuel flow to the premix chamber described below.

The diffusion pilot 62 further includes an air feed pipe 74 coaxial with and surrounding the axial section 66 of the fuel feed pipe. The air input to the air feed pipe 74 is
The compressor discharge air is directed around the combustor 16 into a space 76 defined by the flow sleeve 30 and the combustion chamber liner 78.
(See FIGS. 1 and 2). Diffusion pilot 62 includes at its discharge end a first or diffusion pilot swirler 82 for directing the discharge air of air feed pipe 74 to the diffusion pilot flame.

The premixing chamber 84 is defined by a sleeve-shaped truncated cone 85 surrounding the diffusion pilot 62, the discharge end of which (as viewed in the direction of the flow arrow) terminates near the diffusion pilot discharge end. . Here, the air discharged from the compressor is caused to flow backward from the space 76 to the premixing chamber 84 in a manner similar to the manner in which air is supplied to the air feed pipe 74. A plurality of radial fuel distribution tubes 68 are provided in the air feed pipe 7.
4 and extends into the premix chamber 84, thus mixing the fuel and air and providing a second or premix chamber swirler ring 86 between the diffusion pilot 62 and the premix chamber cone member 85. Send to

A third or center nozzle swirler 90 has a diffusion pilot 62 downstream of the discharge end of the secondary nozzle 100.
Is located between the extension or cup 92 of the discharge end of the first combustion chamber and the central body wall 95 of the primary combustion chamber. Again, the compressor air is drawn from the space 76 surrounding the combustor liner
Flow back to zero. The purpose of this third swirler 90 is to provide stability to the diffusion and premix nozzle flame when combined with the primary premix stream from the primary combustor.

The required designs for the first, second and third swirlers 82, 86 and 90, respectively, are well known to combustion technicians and will not be described further. The cone 85 defining the premix chamber 84 may be formed of any suitable metal for use in a gas turbine environment.

FIG. 4 shows the secondary nozzle 102 of the present invention. The premix nozzle with a diffusion pilot includes a diffusion pilot 104 having a fuel feed pipe 106. The fuel delivery pipe 106 includes an axial pipe section 108 and a plurality of closed-ended radial fuel distribution tubes 110 extending radially outward from the axial pipe section. As in FIG. 3, the preferred embodiment has six such fuel distribution tubes. Fuel distribution tube 1
A plurality of fuel discharge holes or orifices each for delivering fuel downstream toward the discharge end of the secondary nozzle;
2 are provided. As described above, the fuel distribution holes 112
Are dimensioned to provide a desired rate of fuel flow to the premix chamber as described below.

The diffusion pilot 104 further includes an air feed pipe 114 coaxially surrounding the axial portion of the fuel feed pipe 106. Air input to the air feed pipe 114 is obtained by flowing compressor discharge air back around the combustor 16 as described in connection with the embodiment of FIG. Diffusion pilot 104 includes a first swirler ring 116 at its discharge end for directing the discharge air of air feed pipe 114 to the diffusion pilot flame.

The premixing chamber 118 contains the diffusion pilot 104
Is defined by a sleeve 120 surrounding its discharge end 119
Is near the diffusion pilot discharge end, that is, the first swirler 1
Terminates near 16. Here, too, the compressor discharge air flows back into the premixing chamber 118 as described above. A plurality of radial fuel distribution tubes 110 extend through the air feed pipe 114 to the premix chamber 118. However, in this embodiment, the second swirler ring 122 is located upstream of the radial fuel distribution tube 110. By arranging the swirler 122 in this manner, the swirler 12
2 never touches the flame directly at any time,
The life of the swirler can be extended while maintaining the function of the swirler 86 described above. In other words, the airflow is substantially the same as described in the embodiment of FIG. The risk of thermal damage is minimized. Therefore, assuming that the flame characteristics are the same as in the previous embodiment, the result should be the same or similar premixed combustion performance as a whole.

In a presently preferred configuration, the second swirler 122 is an integral part of the secondary fuel nozzle 102, and the swirler moves a series of vanes to the axial centerline of the fuel nozzle, as will be apparent to those skilled in the art. They are arranged at a certain angle in the circumferential direction. The vane may be cast as part of the nozzle or may be made separately and mechanically attached to the nozzle by welding or brazing. The vanes may or may not be aerodynamic, and a corresponding aerodynamic or detached flow will be obtained from the vanes. While it is presently preferred to use a non-aerodynamic scheme, aerodynamic vanes can be utilized as well.

In another embodiment shown in FIG. 5, a premix nozzle with a diffusion pilot is shown, which is the same as the nozzle shown in FIG. 4, but located at the end of the secondary premix chamber. The added Venturi component 124 is added. Venturi 124 is not an integral part of the secondary fuel nozzle. The venturi 124 supplements the recirculation flow to the swirl provided by the upstream swirler 122, which acts to enhance the strong swirl stabilization.

In summary, according to the present invention, N
The possibility of increasing the fuel flow through the secondary nozzle is obtained because the amount of Ox generation is small and the amount of NOx generation is small,
On the other hand, the diffusion pilot receives the pilot's premix flow rather than all of the overall premix flow from the surrounding primary nozzles, thus significantly increasing the turndown ratio, i.e., the ability to operate under various conditions.

At the same time, the service life of the premix swirler, which was previously located at the discharge end of the premix chamber, is increased by rearranging it upstream of the diffusion pilot fuel injection orifice.

Although the present invention has been described with reference to the embodiments which are considered most practical and suitable, the present invention is not limited to the disclosed embodiments, and various modifications and equivalent arrangements are within the scope of the gist of the present invention. Included within.

[Brief description of the drawings]

FIG. 1 is a side view showing a gas turbine engine in a partial cross section.

FIG. 2 is an enlarged schematic sectional view of a combustor portion of the gas turbine engine.

FIG. 3 is a schematic view of a diffusion / premix nozzle for prior application.

FIG. 4 is a schematic diagram of a combined diffusion / premix nozzle according to the present invention.

FIG. 5 is a schematic view of another example of the diffusion / pre-mix nozzle shown in FIG. 4;

[Explanation of symbols]

 24 Primary (upstream) combustion chamber 26 Secondary (downstream) combustion chamber 28 Throat area 36 Primary nozzle 38 Central secondary nozzle 100 Premix nozzle with diffusion pilot 104 Diffusion pilot 106 Fuel feed pipe 108 Axial section 110 Fuel distribution tube 112 Distribution Hole 114 Air feed pipe 116 First swirler 118 Premix chamber 120 Sleeve 122 Second swirler 124 Venturi

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Richard Joseph Bokowick United States of America, New York, Ballston Spa, Timbleberry Road, No. 235 (56) References JP-A-59-101551 (JP, A) JP-A-1-179822 (JP, A) JP-A-2-183720 (JP, A)

Claims (3)

(57) [Claims] 1. A fuel delivery system having a sleeve (120) and a diffusion pilot (104) disposed within the sleeve (120), the diffusion pilot having an inlet end and a discharge end. A pipe (106);
The air feed pipe (11 ) surrounding the fuel feed pipe
4), wherein the fuel delivery pipe (106) further includes a plurality of fuel distribution tubes (110); and a diffusion pilot (104) disposed within the sleeve and the diffusion pilot (10).
4) a premixing chamber (118) surrounding the premixing chamber (118) including an inlet end and a discharge end (119); A premix chamber (118) extending into the chamber (118); and a premix air swirler (122) mounted in the premix chamber (118) upstream from the fuel distribution tube (110). The premixed air swirler is connected to the fuel feed pipe (106) and the air feed pipe (11).
4) and a premixed air swirler (122) with a premixed air swirler (122) receiving the air in the sleeve and swirling the air outside the diffusion pilot (104). Mixing nozzle (102). 2. A gas turbine combustor of the type comprising first and second combustion chambers (24, 26) interconnected by a throat region (28), wherein said throat region (28) is , The first and second combustion chambers (24, 2
6) having a dimension smaller than that of the first combustion chamber (24) and being provided in an annular arrangement upstream of the first combustion chamber (24) for introducing fuel into the first combustion chamber (24). A primary fuel nozzle (54), each of said diffusion nozzles being a first swirler for introducing pressurized air into said first combustion chamber (24) to produce a combustible fuel-air mixture. A plurality of diffusion-type primary fuel nozzles (54), including an annulus (56), disposed upstream of the second combustion chamber (26), toward the second combustion chamber (26); A premix nozzle with a diffusion pilot (102) having a discharge end directed toward the end, the premix nozzle with a diffusion pilot (102) comprising an axial fuel feed pipe (106) and the axis. Encircling the directional fuel feed pipe (106) along substantially its entire length. A diffusion swirler ring (122) located near the inlet end of the premixing nozzle with diffusion pilot (102). Includes gas turbine combustor. 3. A pre-mixing nozzle with a diffusion pilot (102), a third swirler ring (1) provided between the fuel feed pipe (106) and the air feed pipe (114).
16), a premixing chamber (118) surrounding the diffusion pilot (104), and the premixing chamber passing radially outward from the fuel feed pipe (106) through the air feed pipe ( 114 ). (1
18) A plurality of fuel discharge tubes (1) extending into
10) wherein at least one of the radial fuel discharge tubes (110) is provided with the premix chamber (118).
At least one fuel discharge hole (112) directed toward the discharge end of the fuel mixing tube (118), whereby fuel is distributed into the premixing chamber (118). 110) and includes a second swirler ring (122), a gas turbine combustor according to claim 2 which is disposed upstream of the fuel discharge tube (110).