JPH0118331B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a gas turbine incinerator, and in particular,
The present invention relates to a combustor that can adjust the amount of air flowing into the combustor in order to reduce unburned products in combustion gas and ensure stable combustion in a downstream combustion device.

[Conventional technology]

The exhaust gas emitted from a gas turbine combustor contains _NOx , CO, HC, etc., which are considered to be the cause of air pollution, and strict emission regulations are in place for _NOx in particular. The simplest method for reducing NO _x is to inject water or steam into the combustion gas to lower the temperature of the high temperature section where NO _x is generated. Although this method is easy to implement, it is rarely adopted because it has the decisive drawback of reducing the turbine output in order to lower the combustion gas temperature. In contrast, the fuel is distributed in multiple stages,
Attempts to suppress the occurrence of local hot spots and achieve low NO _x by reducing the combustion load per stage or performing lean combustion are becoming mainstream in gas turbine combustors. In the case of a gas turbine combustor, a so-called two-stage combustion method is adopted, in which fuel is injected from the upstream side and the downstream side of the combustor due to constraints such as the structure. FIG. 1 is a diagram showing an example of this two-stage combustion system. That is, the combustor liner 1 has a nozzle attachment port 3 on the upstream side into which the first stage fuel nozzle 2 is attached, and
An air swirler 4 that contributes to flame stabilization of a combustion fire is arranged around the attachment port 3. On the other hand, a second stage fuel nozzle in which an air swirler 5 and a fuel injection part 6 are connected is provided on the circumference of the liner near the downstream side of the liner 1,
Approximately 50% of the fuel is combusted in each nozzle.

[Problem to be solved by the invention]

Although this two-stage combustion method is certainly considered to be an effective means of reducing _NOx , it also has the problem that it tends to emit large amounts of unburned substances such as CO and HC. This problem occurs particularly when a large amount of unburned matter is discharged at the start of first-stage combustion and at the start of second-stage combustion. First, what occurs at the start of the first stage combustion is due to the following reasons. In a gas turbine, since the rotation of the turbine is constant regardless of the turbine output, the amount of air flowing into the liner 1 is also constant.
Therefore, during the first stage of low-load combustion, combustion is carried out with excess air, and as there are many regions where the excess air ratio is outside the flammable range (λ≒0.5 to 2.5), the fuel is discharged without being able to burn. The amount of unburned matter increases.

The amount of unburned emissions from the first stage decreases as the combustion load increases, and when the first stage is at 100% load, that is, when the gas turbine load is approximately 50%,
Combustion is complete to the extent that almost no unburned matter can be detected. Note that this discharge of unburned matter from the first stage has nothing to do with two-stage combustion, and occurs even in conventional one-stage combustion, and is not a problem unique to two-stage combustion. On the other hand, the generation of unburned matter that occurs when fuel is input into the second stage can be said to be a problem unique to two-stage combustion, since it occurs when the combustion load is already about 1/2 of the total. The generation of unburned matter is not only a problem of emissions, but also a problem of performance, which causes a decrease in turbine output, so it must be paid attention to. In particular, the cause of this occurrence is related to the problem of flame transfer from the first stage flame to the second stage fuel, and when the second stage fuel is input, the same as the first stage fuel,
Since the amount of air flowing in from the air swirl circuit is supplied in an excessive amount relative to the fuel, there are many cases where the air is in a lean state outside the flammable range, so it may not ignite or only part of the fuel will burn. This can be seen as resulting in an increase in the amount of unburned emissions.

The purpose of the present invention is to control the amount of air flowing into the vicinity of the second stage nozzle when fuel is input into the second stage in a gas turbine combustor that supplies fuel to two stages from the upstream side and the downstream side, and to mix fuel and air. by ensuring that the proportion in the exhaust gas is constantly in the flammable range.
An object of the present invention is to provide a combustor that can reduce the concentration of unburned substances such as CO and HC.

[Means to solve the problem]

In the two-stage combustion system, it is especially necessary that the flame formed in the first stage be able to move smoothly when fuel is input into the second stage. The condition is to set the air mixture ratio so that it is constantly within the flammable range.

In the present invention, in order to realize this condition and to freely change the mixing ratio of fuel and air in the second stage, there is a A movable cylindrical ring was installed in the 2nd stage, and the opening degree of the air intake near the 2nd stage fuel nozzle was adjusted when the 2nd stage fuel injection started, making it possible to control the amount of air mixed into the 2nd stage fuel. It is characterized by

[Effect]

According to the configuration of the present invention, when the second-stage fuel injection starts, the air from the air intake port near the second-stage nozzle is reduced, and the mixture ratio of the second-stage fuel and air is brought into a fuel-rich state. As a result, flame propagation from the upstream side is improved and emissions of unburned components are reduced.

〔Example〕

A specific example of the present invention is shown in FIGS. 2 to 6.

The main components of the gas turbine combustor include a liner section 1 for generating combustion gas, a fuel supply system, and an air supply system, which are installed in a pressure chamber 9 sealed with an outer cylinder 7 and an end cover 8. The liner 1 has an auxiliary chamber 10 on the upstream side whose diameter is narrower than that on the downstream side.
is provided, and the fuel supplied to the upstream side is combusted in this auxiliary chamber. On the other hand, on the downstream side of the liner 1, there is a main chamber part 11 made larger in diameter than the auxiliary chamber part, and in the main chamber part, the second stage fuel supplied from the downstream side and the unburned fuel in the auxiliary chamber 10 are stored. Burns combustibles such as CO,
In addition, the combustion gas is lowered to a predetermined temperature by air flowing in from the dilution air hole 12 located downstream of the main chamber.

In the present invention, the fuel supply system employs a two-stage supply system. That is, it consists of a first stage fuel nozzle 13 mainly involved in combustion in the auxiliary chamber 10 and a second stage fuel nozzle 14 mainly involved in combustion in the main chamber 11. The difference between the first stage fuel nozzle 13 and the second stage fuel nozzle 14 is as follows.
The first stage fuel nozzle 13 is not a nozzle fixed to the main body of the liner 1, but a separate nozzle is inserted into the liner 1 from the outside of the end cover 8 and installed, whereas the second stage fuel nozzle 14 is attached to the subchamber 1. A plurality of cones are installed around the circumference of the cone 15 connected to the main chamber 11. To explain this part in detail, an air swirling vane 16 is arranged on the circumference of the expanding cone 15, a fuel storage pipe 17 is connected to the upstream side of the air swirling vane 16, and the fuel is transported to the fuel storage pipe 17. Reservoir pipe 17
This is done via a plurality of fuel supply pipes 18 connected to the upstream side of the fuel supply pipe 18. A plurality of second-stage fuel nozzles 14 are mounted on the circumference of the air swirling vane so as to protrude from the fuel reservoir pipe into the air swirling vane.

Next, the air supply system and air control method related to the present invention will be explained.

Air supply systems can be broadly classified as follows. That is, 30 to 40% of the total amount of air supplied to the pre-chamber 10 passes through the air holes 20 provided on the liner outer tube 19, and passes through the primary combustion air holes 22 and 22 provided in the pre-chamber tube 21. Air that flows into the auxiliary chamber 10 from the secondary combustion air hole 23 and an air swirler 24 disposed around the tip of the upstream fuel nozzle 13
There is something that flows into the antechamber through . Since the latter air volume is about 4 to 5% of the total air volume, the subchamber 1
Most of the air flowing into the combustion chamber 0 is supplied from the primary combustion air hole 22 and the secondary combustion air hole 23.

On the other hand, regarding the amount of air supplied into the main chamber 11, the amount of air that passes through the air swirling vanes 16 is the largest at about 30% of the total amount of air, followed by the amount of air that enters through the dilution air hole which accounts for about 15% of the total amount of air. It is.

By appropriately distributing these air according to the combustion load, it is possible to suppress the generation of unburned matter when downstream fuel is input, and to suppress the generation of unburned matter during low-load combustion with upstream fuel. can.

This air control method will be described below.

In the present invention, air flowing into the auxiliary chamber 10 from the primary combustion air hole 22 and the secondary combustion air hole 23 is separated from air flowing into the main chamber 11 through the air swirl vane 16, and this is applied to the combustion load. Control accordingly. An annular air chamber 25 formed by the liner outer cylinder 19, the auxiliary inner cylinder 21, the liner end cover 26, and the enlarged cone 15 is separated into two air chambers by a partition plate 27 provided inside the annular air chamber 25. The upstream air chamber 28 is an air chamber for supplying to the auxiliary chamber 10, and the air in the downstream air chamber 29 is mixed with the second stage fuel by the air swirl vane 14 and used as combustion air for the second stage fuel. be exposed. Air flows into each air chamber from the annular air passage section 30 through a plurality of air holes 20 and 31 provided on the circumference of the liner outer cylinder, and the former air hole 20 flows into the upstream air chamber 28.
The latter air hole 31 is used as an air inflow hole to the downstream air chamber 29.

As a method of controlling the amount of air by closing or opening the air holes 20 or 31, a cylindrical ring 32 movable in the axial direction of the liner as shown three-dimensionally in FIG. 3 is used. The cylindrical ring 32 is the liner outer cylinder 19
It is supported by a plurality of support guides 33 attached above, and is attached so as to slide on the rails 34 of the support guides. The installation procedure involves inserting the cylindrical ring 32 into the support guide 33 from the upstream side of the liner.
At that time, the upstream end of the support guide 33 is cut open, and the cylindrical ring 32 is connected to the support guide 3.
After being inserted into the rail 34 of No. 3, the upstream end of the support guide is fastened by the stopper 35, and the cylindrical ring 32
The liner is installed so that it does not slip out in the axial direction of the liner. FIG. 4 shows a detailed view of the cylindrical ring 32. Support guide rails 34 are provided at the upstream and downstream ends of the cylindrical ring 32.
Side plates 36 and 37 which are somewhat taller than the above are attached, and these side plates are provided with a plurality of notches 38 and 39 for insertion into the guide rail 34.
When the notch is inserted into the guide rail, it is installed in such a size that there is a slight gap between the bottom surfaces 40, 41 of the side plates and the liner outer cylinder 19.

Next, the cylindrical ring 32 is driven in the axial direction of the liner using the following means. A plurality of support fittings 42 for fixing the push rods can be attached to the upstream side of the cylindrical ring 32. FIG. 4 shows two support fittings 42 as an example.
Shown with the attached. A push rod 43 is connected to the support fitting 42 . As shown in FIG. 3, the other end of the push rod 43 is connected to a piston drive device 45 that incorporates a pressure piston whose outer cylinder is installed in an end cover 44.
is connected to. By applying external pressure to the piston 46 of the piston drive device 45, the cylindrical ring 32 is moved downstream via the push rod 43. On the other hand, when the pressure applied to the piston is reduced, the piston 46 is pushed back upstream by the coil spring 47 at the bottom of the piston 46, and therefore the cylindrical ring 32 is also moved upstream.
In this way, when the push rod is driven by the piston, a control system is incorporated so that the displacement of the plurality of pistons from a predetermined position always falls within a predetermined allowable displacement position.

Next, how to move the cylindrical ring and control the amount of air according to the combustion load will be described below.

The solid line and broken line shown in Figure 5 are representative examples of unburned matter when air volume is not controlled and when appropriate control is applied, respectively.
The relative comparison of CO concentration is shown with combustion load on the horizontal axis. The CO concentration shows a distribution with a peak during low load combustion and at 2/4 load or higher. As explained earlier, the high level of CO generated during low-load combustion is due to excess air being supplied when fuel is input into the first stage, while the peak secondary that occurs after 2/4 load The excessive air condition continues over a certain load range from the time fuel is introduced into the stage, and the mixture ratio of air and fuel is outside the flammable range.
This occurs because the flame does not move completely from the upstream side, or only partially burns.

FIG. 6 shows an example of the upstream air hole and downstream air hole opening degree control, and the curve shown by the broken line in FIG. 5 is achieved by this. The basic idea behind this air hole opening control is to keep the upstream air holes fully closed from when the upstream fuel is injected until about 0/4 load to promote combustion in a fuel-rich state. Then, the opening of the air hole is increased from around 0/4 load, and the opening is controlled to 100% around 2/4 load. At this time, the opening degree of the downstream air hole is determined by the structure.
The opening is 100%. Subsequently, when downstream fuel is introduced, the cylindrical ring 32 is inserted into the downstream air hole 3.
1 is moved to a position where it is completely covered, that is, fuel injection is started with the downstream air hole opening degree being zero, and the downstream side is also rich in fuel and the flame from the upstream side is Completed the transfer, increased the opening of the air hole from around 3/4 load, and increased the opening to 100 at 4/4 load.
Control so that the opening degree is %. On the other hand, the upstream air hole is controlled to 10
The opening will remain at %.

〔Effect of the invention〕

According to the present invention, since the air-fuel ratio of the second stage fuel can be maintained within the flammable range when the second stage fuel is introduced, the generation of unburned components such as CO and HC after the second stage fuel is introduced is suppressed. Ru.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional combustor, FIG. 2 is a sectional view of a combustor of the present invention, FIG. 3 is a perspective view of a combustor of the present invention, FIG. 4 is a perspective view of a cylindrical ring, and FIG. The figure shows the relationship between combustion load and CO concentration, and FIG. 6 shows the relationship between combustion load and air hole opening degree. 13...First stage combustion nozzle, 14...Second stage fuel nozzle, 19...Liner outer cylinder, 20, 31...
Air hole, 21... Sub-inner cylinder, 22... Primary combustion air hole, 23... Secondary combustion air hole, 24... Air swirler, 25... Annular air chamber, 26... Liner end cover, 27 ... Partition plate, 28 ... Upstream air chamber, 29 ... Downstream air chamber, 30 ... Annular air passage section, 31, 32 ... Cylindrical ring, 33 ... Support guide, 34 ... Support guide rail , 35... Stopper fitting, 36, 37... Side plate, 38, 39... Notch, 42... Support fitting, 43, 44... Push rod,
44... Outer cylinder end cover, 45... Piston drive device, 46... Piston, 47... Coil spring.

Claims (1)

[Claims] 1 A first-stage fuel nozzle is provided on the upstream side of a cylindrical combustor liner, and a second-stage fuel nozzle is provided on the downstream side. In a low load region, fuel from the first stage fuel nozzle is combusted, and in a high load region, the fuel from the first stage fuel nozzle is combusted. and a gas turbine combustor that burns fuel from both second-stage nozzles, an air port provided near the second-stage fuel nozzle to take in combustion air to be mixed with the fuel from the second-stage nozzle; means for adjusting the opening area of the air port, and the amount of air passing through the air port is reduced by the means for adjusting the opening area at the start of the second stage fuel injection. Turbine combustor.