JPS59183202A - Low nox burner - Google Patents

Abstract

PURPOSE:To provide a low NOX burner which prevents the occurrence of backfire and is excellent in reliability, by constituting such that the speed of fluid flowing through a gap between a burner liner and a fuel nozzle is increased on the upstream side and decreased on the downstream side. CONSTITUTION:A one-stage nozzle 13, of which a burner consists, is formed in the shape of a cone such that it is of a large size on the upstream side and of a small size on the downstream side to provide an internal nozzle inner chamber 14, and a number of nozzle holes 26 are provided in its chamber wall. A relation size between a burner liner and the cone-shaped part of a fuel nozzle is set so that a velocity of flow in a premixture chamber is increased on the upstream side, and the velocity of flow in the premixture chamber is set to a maximum value higher than a backfire limit. Namely, the maximum velocity of flow in the premixture chamber is set to a value which is increased over the rate of flame propagation, for example, 40m/s, of backfire under the most adverse condition. This causes to prevent the occurrence of backfire as a result of backfire flame being carried away by a premixture stream, resulting in the possibility to perform stable low NOX combination.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a low NO combustor for a gas turbine, and in particular, to a low NO combustor using premixing.
This invention relates to a low NO combustor that prevents problematic backfire in order to achieve sufficient premixing.

NO, which is generated from various combustion equipment, has become a problem of air pollution, but especially for gas turbine combustors, it can be reduced by a dry method based on improving combustibility and a wet method using water or steam. NOx reduction technology is being advanced. However, the NO generation mechanism during combustion is extremely complex, making it technically difficult, and no definitive reduction technology has yet been established. In particular, the dry method has the advantage of not requiring any other medium, but its combustion mode is lean, low temperature, and under severe conditions of 01 low NO.

Although it is possible to some extent, CO emissions tend to increase. In general, the production of NO during combustion is dominated by the combustion gas in a localized high-temperature part of the combustion region, and is mainly generated by the nitrogen content of unburned fuel exhaust and the oxidation of nitrogen in the combustion air. These are called TSUEL N08 and thermal NOx, and are particularly highly dependent on thermal NO, a oxygen concentration, and reaction time, and are strongly influenced by gas temperature. Therefore, if low-temperature combustion is achieved in which no localized high-temperature regions are formed during the combustion process, effective low-NO combustion becomes possible.

Conventionally, as a combustion method for reducing NO in a gas turbine combustor, there is a method to lower the flame temperature by injecting water or steam (the so-called wet method), as described above. Since it has the drawback of decreasing efficiency, research and development efforts are currently underway to realize lean, low-temperature combustion.

To achieve the above objective, even if a large amount of air is simply circulated near the fuel spray, the combustion rate is high and the fuel burns before the air and fuel are sufficiently mixed, resulting in uneven fuel concentration. As a result, localized high temperatures occur, making it impossible to significantly reduce NOx. In addition, the introduction of excess air supercools the flame surface, causing an increase in unburned emissions such as CO and unstable combustion, which tends to occur mainly in diffusive combustion.

Therefore, depending only on the combustion form, it is possible to ideally
In order to reduce O, it is necessary to thoroughly mix fuel and air before combustion to equalize the flame temperature and suppress the occurrence of localized high temperatures.

As mentioned above, combustion methods that completely mix fuel and air to equalize the flame temperature are generally premixed.)
Yo? ), No! and is effective for CO reduction. A known example of this combustion system is shown in Figs. 1 and 2. In the case of the combustor shown in Fig. 1, the operating method is to ignite the fuel injected through nozzle F2 at startup, and to reduce the load. When the fuel becomes large, the flame is transferred to the fuel to be injected from the nozzle Ft, and then the flame of F2 is extinguished, and the fuel is injected only from the nozzle F1. It is used to burn it. On the other hand, in the example shown in FIG. 2, the nozzle Fl is started, and when the load becomes large, combustion is injected through the nozzle F2, and after being mixed with air in the premixing chamber 51, it is combusted in the main chamber 53.

In both of the above-mentioned known examples, the diaphragm portions 42° and 52 are provided to prevent backfire, but the back 7-year conditions vary, and the fixed diaphragm portions as in both of the above-mentioned known examples cannot be used. Stability.

Not reliable enough.

[Purpose of the invention]

The purpose of the present invention is to answer NO! A low NO that prevents backfire, which is an obstacle to reduction, has stable combustion characteristics, and has excellent reliability! The purpose is to provide a combustor. By preventing backfire, the N08 reduction of the premixing method can be effective.

[Summary of the invention]

To achieve the above object, the present invention provides a combustor for a gas turbine in which the upstream end of the combustor liner is open, a cone-shaped fuel nozzle is provided near the center of the combustor liner, and the cone-shaped fuel nozzle is provided near the center of the combustor liner. The shape is thick on the upstream side and narrow on the downstream side, so that the gap between the combustor liner and the fuel nozzle is small on the upstream side of the nozzle and wide on the downstream side, so that the velocity of the fluid passing through this gap is on the upstream side. It is characterized by being configured so that it is fast and slow on the downstream side.

[Embodiments of the invention]

FIG. 3 is a sectional view of one embodiment of the low NO combustor of the present invention, showing an air compressor 1 for a gas turbine. Turbine 3. load 4
FIG. The outline is that compressed air 5 discharged from the compressor 1 is introduced into the combustor liner 6, and the fuel injected from the first stage nozzle 13 is combusted to generate high temperature and high pressure working fluid, which rotates the turbine 3. let 2 is a combustor outer cylinder.

Specifically, the compressed air 5 is supplied to the dilution air hole 7 provided in the combustor liner 6. Swirler installed in the rear combustion chamber 8.
And, it is configured to be introduced into the combustor from the upstream end of the combustor liner 6. Further, a portion of the compressed air 5 is configured to be introduced into the combustor liner 6 as cooling air 9.

Further, the fuel 10 is controlled by a control valve 11 that controls the required amount of fuel.
The fuel enters the first-stage nozzle 13 from the fuel inlet pipe 12 through the nozzle, and then enters the nozzle inner chamber 4. Along the cone of the first-stage nozzle 13, it becomes premixed fuel 19 in the premixing chamber 15 and is used for starting the ignition section. At step 16, premix combustion is performed. On the other hand, fuel is supplied to the second stage swirler 8 provided in the rear combustion chamber 18 of the combustor liner 6 via the control valve 17, and is ejected together with the air flow to perform lean low-temperature combustion in the rear combustion chamber 18. Furthermore, during combustion operation, cooling air 9 is introduced through cooling air holes provided in the combustor liner 6 to improve wall cooling of the combustor litchi 6 and uniformity of combustion gas temperature. In addition, the dilution air hole (
The set temperature of the combustion gas is determined by introducing an air flow from the engine (not shown).

FIG. 4 is a chart showing the flow rate of fuel fed into the combustor configured as described above. The horizontal axis of the figure shows the gas turbine load factor, and the curve shown in the figure shows the gas turbine load factor of O.
This figure shows an increase in the fuel flow rate when the fuel flow rate changes from 100% to 100%. As shown in this figure, the partial load of the gas turbine (
Low-temperature combustion is performed mainly through the first-stage nozzle 13 (i.e., premixing nozzle) until the turbine load approaches 50%, and then fuel is sprayed from the second-stage nozzle (described later with reference to FIG. 5), resulting in rear combustion. Air is also jetted from the swirler 8 provided in the chamber 18 to achieve stable lean and low temperature combustion at the rated load (100%). That is, it is an important issue that the first-stage nozzle 13 can always perform stable and good premix combustion in the operating range from ignition to 1/2 partial load.

Furthermore, with reference to FIGS. 5 and 6, the configuration 1 function of the present invention will be explained in detail.

70 sleeve 2 installed inside the outer cylinder 21 as shown in FIG.
The combustor inner cylinder 6 is connected to the combustor cylinder 3 by a straight line 25.
, 1st stage nozzle 13 provided in the center of the combustor. 1st stage nozzle 13
Cup to install (-22, 2 to inject fuel into swirler 8)
Stage nozzle 27. A combustor is constituted by a swirler 20 that adds a swirling flow to the air flowing into the first stage nozzle inner chamber 14, and a spark plug 28 that ignites at startup.

The first stage nozzle 13 is formed into a cone shape, with the upstream side (left side in the figure) of the combustor being thicker and the downstream side being narrower.
A nozzle internal chamber 14 is provided inside, and a large number of nozzle holes 26 for ejecting fuel are provided in the chamber wall.

FIG. 6 shows the flow velocity distribution in the above example, where the horizontal axis represents the position in the length direction of the cone-shaped part at the tip of the nozzle, with the large diameter side (upstream side) end being the 0 position, and the small diameter side (downstream side ) The end is shown as the 100 position. The vertical axis represents the flow velocity within the premixing chamber 15 formed around the outer periphery of the cone-shaped portion.

When implementing the present invention, the flow velocity distribution does not necessarily have to be the same as in this example, but at least the combustor liner should be designed so that the flow velocity in the premixing chamber is high on the upstream side (in this figure, the upper left is a curved line). and the cone-shaped portion of the fuel nozzle, and set the maximum value of the premixing chamber flow velocity higher than the backfire limit.

That is, the maximum flow velocity in the premixing chamber is made faster than the flame propagation velocity of the backfire under the worst conditions (for example, 40 m/s). As a result, the flame of the backfire is swept away by the premixed flow and no backfire occurs, so that stable low-No.

Next, an application example of the present invention will be described. The structure of the present invention has a direct purpose of forming a substantially uniform decelerated flow in the premixing chamber as described above, so the fuel nozzle is made into a straight pipe and the open end of the combustor liner is made into a small diameter pipe. A similar effect can be obtained by configuring the expansion tube to be tapered in depth.

However, since the open end of the combustor liner is determined by the flow rate, the rear combustion chamber has a large diameter, which is disadvantageous in terms of cost.

The embodiments shown in FIGS. 3 and 5 have the following advantages: (1) As shown in FIG. 6, the flow velocity in the premixing chamber can be made sufficiently higher than the normal backfire limit speed; (10) Stable combustion can be obtained because the ignition occurs at the stagnation part of the nozzle tip even at startup, and even if the fire conditions change,
Stability can be maintained only by expanding the combustion range slightly toward the upstream side.

〔Effect of the invention〕

As detailed above, the present invention provides a combustor for a gas turbine in which the upstream end of the combustor liner is open,
A cone-shaped fuel nozzle is provided near the center of the combustor liner, and the above cone shape is thicker on the upstream side and narrower on the downstream side, so that the gap between the combustor liner and the fuel nozzle is smaller on the upstream side of the nozzle and narrower on the downstream side. By making the gap larger on the side and configuring the gap so that the velocity of the fluid passing through it is faster on the upstream side and slower on the downstream side, an almost uniform decelerated flow is formed in the premixing chamber and backfire is suppressed. This greatly contributes to low NO and improved reliability of the combustor, as it prevents this and provides stable fuel characteristics.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views for explaining known examples of low NOx combustors, FIG. 3 is a sectional view of a gas turbine equipped with the low NOx combustor of the present invention, and FIG. 4 is the above-mentioned example. Figure 5 is a diagram showing the fuel flow control of the gas turbine.
The low NO shown in the figure. FIG. 6, an enlarged cross-sectional view of the combustor, is also a chart showing the velocity distribution. 5... Compressed air, combustor liner, 7... Dilution air,
8...Swirler, 9...Cooling air, 10...Fuel,
11... Control valve, 12... Fuel introduction pipe, 13...
1st stage nozzle, 14... Nozzle inner chamber, 15... Premixing chamber, 16... Starting ignition part, 17... Control valve, 18...
... Rear combustion chamber, 19... Premixed fuel, 20... Swirler, 21... Outer cylinder, 22... Cover, 23...
Flow sleeve, 25... Stopper, 26... Nozzle hole, 27... Two-stage nozzle, 28... Spark plug,
29...Upstream end of nozzle cone part, hair/Fig. 4

Claims (1)

[Claims] 1. In a combustor for a gas turbine, the upstream end of the combustor liner is open, and a cone-shaped fuel nozzle is provided near the center of the combustor liner, with the cone shape being thicker on the upstream side and thicker on the downstream side. The 1141 gap between the combustor liner and the fuel nozzle is made smaller on the upstream side of the nozzle and larger on the downstream side, so that the velocity of the fluid passing through this gap is faster on the upstream side and slower on the downstream side. A low NO combustor characterized by having the following configuration.