JPS5892714A - Combustor for gas turbine - Google Patents

Abstract

PURPOSE:To improve the outside combustion in a burner and achieve the reduction in the emission of unburned component by an arrangement wherein air is previously mixed outside atomized fuel and then air is introduced through a swirler. CONSTITUTION:The fuel spray produced by a fuel injection valve 11 is conical as shown by M. The air intoduced through a swirler 12 is once drawn in by a guide passage 14 as shown by N1, and then allowed to flow by a guide passage 15 along the outer periphery of the cone M. As a result, the air is mixed in the fuel mainly in the outer periphery of M, but it hardly enters the inside of M. Subsequently, a required amount of air is introduced through a swirler 16 at a position where the cone M spreads further. Thus, a sufficient amount of air can be supplied into a liner 17 thereby enabling an excellent flame condition to be kept.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine combustor, and more particularly to a gas turbine combustor provided with an effective air introduction device.

The combustor of a gas turbine injects fuel into air compressed by a compressor, combusts it, and sends high-temperature combustion gas to the turbine side.

In a typical gas turbine combustor, a liner 2 is provided within a casing 1, as shown in FIG. 1, and a fuel injection valve 3 is provided at the center of the tip of the liner 2. A swirler 4 is provided on the outer peripheral side of the fuel injection valve 3 to introduce air into the liner 2 to mix fuel and air and maintain flame.

Air compressed by a compressor (not shown) enters the casing 1 like Po, passes through the swirler 4 and is introduced into the liner 2 like P, and on the other hand passes around the outer periphery of the liner 2 like P.

Fuel is introduced as indicated by QO in the figure, and is sprayed as indicated by Ql through the fuel injection valve 3. Usually, a spiral injection valve is used as the fuel injection valve 3, and therefore the spray Q1 has a conical shape.

The interior of the liner 2 is divided into three combustion zones.

That is, it is divided into a primary combustion region Pz that mainly performs flame stabilization, a secondary combustion region Bz that aims for complete combustion of fuel, and a dilution region Dz that cools the high temperature combustion gas with air to the turbine inlet temperature.

When ignited with an ignition device (not shown) to cause combustion, P
A stable flame is always maintained inside E3z, and P in the figure
Air is introduced to D for complete combustion, and air is introduced to D as shown at P4 in the figure to dilute it and lower it to the turbine inlet temperature.

There are various technical issues required of gas turbine combustors, but they can be roughly summarized as follows: (1) Low air pressure loss (2) Uniform temperature distribution near the outlet ( 3) High combustion efficiency 4) Low emission of air polluting components (5) Low combustion noise level (6) Good ignition performance and wide stable combustion range (7)
Insensitivity to changes in operating conditions (8) Simple structure, small size and light weight (9) Excellent durability, easy maintenance and inspection, and therefore low cost Solving the above technical problems Therefore, various improvements have been attempted in the past, but none can be said to be satisfactory.

An object of the present invention is to provide a combustor for a gas turbine in which combustion conditions are improved by introducing air through a swirler, re-atomizing fuel spray by the air, and promoting premixing of fuel and air.

A more detailed explanation will be given below with reference to the drawings.

FIG. 2 is a cross-sectional view of a waterway showing an example of a known air assist system.

The fuel injected from the fuel injection valve 5 spreads into a conical shape as shown by J in the figure. Air is introduced from swirlers 6, 7 as K, , K2. In the air assist method, air compressed by a compressor 8 is injected from a nozzle 9 and is blown into a fuel spray J that has spread into a conical shape. Since this air blowing is performed over the entire area of the fuel spray J, it has the effect of atomizing the entire fuel particles of the fuel spray J and helps premixing the fuel and air.

Although this air assist method greatly contributes to improving combustion, it also has the following drawbacks.

The air assist method requires a separate compressed air source and air control system, and also increases weight and cost.

Furthermore, when the fuel flow rate suddenly decreases, the flame tends to blow out due to atomized air.

In order to improve the above drawbacks, the following things are necessary.

First, air can be blown with a simple structure.

Second, fuel particles must be atomized efficiently by blowing air.

Next, the premixing of fuel and air effectively contributes to the promotion of combustion and stable flame holding.

The fuel particles injected by the spiral fuel injector are
It is desirable that the particle size be uniformly fine, but generally the particle size is large on the outer circumferential side of the conical spray and small on the inner circumferential side.

Therefore, it can be seen that simply atomizing the coarse droplets on the outer circumferential side of the conical fuel spray greatly contributes to improving combustion.

Then, as a result of introducing air to the outer circumferential side of the conical fuel spray and making the air flow follow the fuel spray only for a predetermined time or distance, the following was found.

By creating an air body along the cone of the fuel spray near the outer periphery of the conical fuel spray, blue flame combustion can be easily obtained and smoke generation can be reduced.

On the other hand, when air is introduced toward the outer periphery of the fuel spray near the injection valve, the fuel spray is re-atomized mainly on the outer periphery, fuel is promoted, and the high temperature gas on the outer periphery is circulated to form the fuel spray. It can flow into the inside of the flame and maintain stable flame stability.

Next, one embodiment of the present invention will be described with reference to FIG.

A swirler 12 is provided on the outer periphery of the spiral-wound fuel injection valve 11. The swirler 12 has a large number of air swirling vanes,
Creates an air flow along the air swirl vanes.

Further, a guide cylinder 13 is provided on the outer periphery of the injection valve 11. The guide cylinder 13 consists of a guide passage 14 that restricts the air flow introduced from the swirler 12, and a guide passage 15 that guides the restricted air flow along the outer periphery of the fuel spray.

The fuel injected from the injection valve 11 forms a conical spray as shown by M in the figure. The guide channel 15 has a conical spray M
It has a length that substantially coincides with the outer periphery of the cylinder, and allows re-atomization of coarse droplets and premixing of fuel and air at the same time.

Another swirler 16 is provided on the outer periphery of the guide tube 13 to introduce a required amount of air into the liner 17 and to provide a flame stabilizing effect.

The operation of the present invention configured as described above is as follows.

The spray from the injection valve 11 has a conical shape as shown in M. The air introduced from the swirler 12 is guided through the guide channel 1 as shown by N in the figure.
After being once narrowed down by the guide channel 15
The flow is along the outer periphery of.

Therefore, air is mixed into the fuel mainly at the outer periphery of M. However, the shape is such that almost no air can enter the inside of M.

The particle size of the fuel spray inside M is smaller than that on the outer circumferential side, so there is no need for re-atomization, and from the viewpoint of flame-holding performance, it is better not to allow atomization air to flow there.

Subsequently, the required amount of air is introduced from the swirler 16 at a position where M is further expanded. As a result, the amount of air flowing into the liner 17 becomes sufficient, and a good flame-holding state can be achieved.

Now, within the combustor, fuel injection and fuel are continuously performed.

Normally, in a combustor, as shown in Figure 4, a gas flow G that has been burned at a high temperature on the outside enters the inside, and a flow that flows back toward the injection valve side as shown in G2 occurs.1G2 further flows to the outside as shown in G. .

In this case, the better the mixing condition of the fuel and air on the outside, that is, the more the fuel and air are mixed before combustion, the better the combustion condition becomes, resulting in blue flame combustion.

In the present invention, air is mixed in advance on the outside of the fuel spray, unlike the conventional method, and then the air is introduced through a swirler as in the conventional method.

Therefore, combustion outside the combustor is improved, resulting in reduced emissions of end-combustion components.

FIG. 5 shows another embodiment of the present invention, in which the guide tube 18
A swirler 19 is provided to introduce air in the radial direction, and a combustion form similar to that of the embodiment shown in FIG. 3 can be obtained.

The effects of the present invention constructed and operated as described above are as follows.

(1) At the same time as the coarse droplets on the outside of the fuel spray are re-atomized, the fuel and air are better mixed, the flame blowout caused by the introduced air is eliminated, and the combustion performance is improved.

(2) Conventionally, the effective combustion region was at an equivalence ratio of around 1, so a lot of NOx was generated, but with the present invention, the equivalence ratio can be reduced to about 0.8 to 0.9, and the amount of NOx generated is also reduced. do.

(3) Better mixing of fuel and air outside the fuel spray reduces smoke generation.

(4) The device is simpler than the air-assist method, which requires a separate compressed air source.

(5) Desired air is mixed into the outer periphery of the fuel spray before combustion, so
Blue flame combustion is obtained without deterioration in flame holding performance, heating of the liner wall due to flame radiation is reduced, and liner durability is improved.

(6) Even if the flame flows back close to the injection valve, the tip of the injection valve is exposed to the airflow and cooled, so the injection valve does not become hot. Furthermore, since a fluidized bed of air is created near the tip of the injection valve, no carbon buildup occurs.

(7) Since combustion occurs in a premixed state of air and fuel, the length of the combustor can be made shorter than that of conventional combustors.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a gas turbine combustor, FIG. 2 is a schematic sectional view showing an example of a known air assist system, FIG. FIG. 5 is a schematic cross-sectional view showing another embodiment of the present invention. 11: Injection valve, 12, 19: Swirler, 13.18: Guide cylinder.

Claims (1)

[Claims] A first swirler and a guide cylinder are provided on the outer periphery of the tip of the fuel injection valve, and the guide cylinder includes a guide flow path that narrows the air introduced by the first swirler and an outer periphery of the conical fuel spray injected from the injection valve. one or more second swirlers are provided on the outer periphery of the guide tube, and coarse droplets on the outer periphery of the conical fuel spray before combustion are removed by airflow along the guide channel. A gas turbine combustor characterized by atomization and premixing at the same time.