JPH07280266A - Premixing device - Google Patents

Abstract

PURPOSE:To keep a stable combustion by a method wherein a flow rate of air is reduced when a low flow rate of fuel occurs, a back-fire and a self- ignition are prevented from being generated at a premixing part. CONSTITUTION:A supporting tube 12, an air supplying part 13 for supplying air into an inner side and a premixing tube 14 are connected in this sequence. A fuel injection valve 4 is slidably fitted within these members and there is provided a driving mechanism 17 for reciprocating the fuel injection valve 4 from the supporting tube 12 to the outlet port of the premixing tube 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a premixing device for premixing and supplying fuel and air to a combustion chamber of a gas turbine, and more particularly to a premixing device for performing stable combustion even at a low fuel flow rate.

[0002]

2. Description of the Related Art In a gas turbine or jet engine combustion apparatus, a premixer is provided between a combustor and a fuel injection nozzle to promote evaporation of fuel supplied to the combustor and mixing with air. I try to get a good combustion. In the case of such a premixing system, lean combustion is possible and NOx
It is possible to significantly reduce the emission amount of (nitrogen oxide) and the like.

FIG. 3 is a diagram showing an example of a combustion device equipped with a premixing device. The primary air A taken in from the primary air intake 7 is supplied to the premixing device 3 and the pilot burner 5 in the primary air supply unit 1. A fuel injection valve 4 is provided at the head of the premixing device 3, and mixes the fuel from the fuel pipe 6 with the primary air A and evaporates the fuel and injects it into the combustor 2 to burn it. The pilot burner 5 supplies the ignition source, and thereby reliably burns the mixture of the fuel and the air injected from the premixing device 3. The secondary air B is supplied to the combustor 2, burns, mixes with the combustion gas, becomes exhaust gas C, and is discharged from the combustor outlet 8 to drive the turbine.

[0004]

The gas turbine adjusts the fuel flow rate in response to load fluctuations and changes the output from low output to maximum output. The air flow rate must also be reduced in order to maintain stable combustion at low fuel flow rates. When the air flow rate decreases, the flow velocity of the primary air supplied to the premixing device 3 becomes slow, and flashback or self-ignition (auto ignition) occurs in the premixing device 3.

FIG. 4 is a diagram for explaining occurrence of flashback and self-ignition in the premixing device 3. In order to reduce the primary air flow rate according to the decrease in the fuel flow rate, the bypass 9 is provided, the valve 10 is opened, and a part A1 of the primary air is introduced into the combustor 2. As a result, the flow velocity of the air supplied to the premixing device 3 decreases, and the flow rate also decreases. When the flow velocity of air decreases and the injection speed of the fuel mixed with air becomes slower than the flame propagation speed from the combustor 2, flame propagation and self-ignition occur, and combustion occurs in the premixing device 3. This allows the premixing device 3
Damage is caused, and stable combustion cannot be sustained.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a premixing device capable of maintaining stable combustion without causing flashback or self-ignition even at a low fuel flow rate. To aim.

[0007]

In order to achieve the above object, a fuel injection valve for injecting fuel mixed with air, a support portion slidably fitted to the fuel injection valve on an inner surface thereof, and one end thereof supported. And an air supply part which is capable of passing the inside of the fuel injection valve and supplies air to the inside from the outside, and one end of which is connected to the other end of the air supply part and the other end of which is in communication with the combustion chamber. The premixing section is slidably fitted to the fuel injection valve on the inner surface, and the drive mechanism that reciprocates the fuel injection valve from the support section to the other end of the premixing section.

The position where the fuel injection valve injects the fuel is at the other end of the support part and the premixing part, and when the other end of the premixing part is located, the injection amount of air and fuel is smaller than that at the support part. It was done like this.

[0009]

The fuel injection valve is arranged in the support portion, and the fuel mixed with air is injected from the fuel injection valve to the premixing portion. Also, air is injected from the air supply unit to the premixing unit. As a result, fuel is vaporized and mixed with air in the premixing unit, and the fuel is diluted according to the amount of air supplied from the air supply unit and injected into the combustor to perform low NOx combustion. Air is supplied from the air supply unit at a flow velocity that does not cause flashback or self-ignition in the premixing unit.

Next, the drive mechanism moves the fuel injection valve to the end of the premixing section on the combustor side. As a result, the fuel mixed with air is directly injected from the fuel injection valve to the combustor, so that there is no problem of flashback or self-ignition in the premixing section. Since the air from the air supply unit is blocked by the fuel injection valve and cannot flow through the premixing unit to the combustor, the air supply state is suitable for combustion at a small fuel flow rate.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a combustion device provided with a premixing device of this embodiment, (a) shows a medium fuel flow rate, and (b).
Indicates a small fuel flow rate. FIG. 2 shows the configuration of the premixing apparatus of this embodiment, (a) shows the state at the time of medium and large fuel flow rate,
(B) shows a state at a small fuel flow rate.

In FIG. 1, primary air A is taken into a primary air supply unit 1 from a primary air inlet 7, and is supplied to a premixing device 3 and a pilot burner 5. Premixing device 3
A fuel injection valve 4 is slidably fitted in the. Fuel is supplied from a fuel pipe 6 to the fuel injection valve 4 and the pilot burner 5. A combustor 2 is provided to separate the primary air supply unit 1 from the partition wall 11, and the premixer 3 and the pilot burner 5 are provided.
The fuel mixed with the air injected from is burned. Further, a bypass 9 is provided from the primary air supply unit 1 to the combustor 2 and the valve 10 is opened and closed to bypass the primary air to the combustor 2. The secondary air B is supplied to the combustor 2 and burns, mixes with the combustion gas and becomes exhaust gas C, which is discharged from the combustor outlet 8 and rotates the turbine. In addition, D represents the flame during combustion.

In FIG. 1A, a fuel injection valve 4 is arranged on the inlet side of the premixing device 3, and air a1 is supplied and mixed with fuel to be injected into the premixing device 3. Air a2 is further supplied into the premixing device 3 to dilute the fuel and enable low NOx combustion. The air a3 is supplied to the pilot burner 5, but the amount of fuel is increased with respect to the air flow rate, and the fuel functions as a pilot fire so that combustion is always performed when the fuel is injected into the combustor 2.

In FIG. 1 (b), the fuel injection valve 4 is moved to the outlet side of the premixing device 3, and the fuel mixed with the air a1 is directly injected into the combustor 2. The air a2 is blocked by the fuel injection valve 4 and is not sent to the combustor 2 side. Therefore, the excess primary air A1 opens the valve 10 and is supplied to the combustor 2 from the bypass 9. The flow rate of the secondary air B is also reduced in accordance with the decrease in the fuel flow rate.

In FIG. 2, the premixing device 3 has a structure in which a support pipe 12 and a premixing pipe 14 are connected by an air supply portion 13, and a fuel injection valve 4 is slidably fitted inside these. ing. The air supply unit 13 includes a first annular ring 13a and a second annular ring 13a.
It has an annulus 13b, and is configured to blow air a2 into the inside from each annulus 13a, 13b. A fuel supply pipe 15 is connected to the fuel injection valve 4 for supplying fuel and transmitting the reciprocating motion of the drive mechanism 17. The fuel supply pipe 15 is supplied with fuel from a flexible tube 16, and the tube 16 is connected to the fuel pipe 6 of FIG. Drive mechanism 1
Reference numeral 7 may be a reciprocating cylinder or screw mechanism that reciprocates by air pressure or hydraulic pressure.

In FIG. 2A, the fuel injection valve 4 is a support pipe 1.
At the position 2, the fuel mixed with the air a1 is further blown with the air a2 from the air supply unit 13, and the fuel is evaporated in the premixing pipe 14 and mixed with the air to be diluted. The flow rate of the air a2 is set so that the flow velocity of the diluted fuel becomes faster than the flame propagation velocity from the combustor 2 and the flashback does not occur. In this state, at a high fuel flow rate or a medium fuel flow rate, the air flow rate is supplied more than theoretically required for combustion to dilute the fuel and reduce the NO
x Suitable for burning.

In FIG. 2B, the fuel injection valve 4 has a premixing pipe 14
The air a2 from the air supply unit 13 is cut off by the fuel injection valve 4 and the fuel mixed with the air a1 is injected into the combustor 2 at the outlet side of the. In this state, the air a2 is automatically shut off by the movement of the fuel injection valve 4, so that it is suitable for maintaining stable combustion at a small fuel flow rate.
In this case, since the fuel mixed with the air is directly injected into the combustor 2, there is no occurrence of flashback or self-ignition in the premixing pipe 14.

In the above-mentioned embodiments, the support pipe, the air supply portion, and the premixing pipe have a circular cross section, but they are not necessarily circular, and may be square, for example.

[0019]

As is apparent from the above description, according to the present invention, the fuel injection valve moves in the premixing device to make the air flow rate variable, and the fuel mixed with air can be directly injected to the combustor. The air flow rate is automatically reduced at the time of fuel flow rate to prevent flashback and self-ignition in the premixing device, low NOx combustion is performed at medium and large fuel flow rate, and stable from small fuel flow rate to large fuel flow rate Burning can be performed.

[Brief description of drawings]

FIG. 1 shows a configuration of a combustion apparatus using a premixing apparatus of the present embodiment, (a) shows a medium fuel flow rate, and (b) shows a small fuel flow rate.

FIG. 2 shows a configuration of a premixing apparatus of the present embodiment, (a) shows a state of medium and large fuel flow rate, and (b) shows a state of small fuel flow rate.

FIG. 3 is a diagram showing combustion by a conventional premixing device.

FIG. 4 is a diagram showing a state where flashback and self-ignition occur in a conventional premixing device.

[Explanation of symbols]

 1 Primary Air Supply Section 2 Combustor 3 Premixing Device 4 Fuel Injection Valve 5 Pilot Burner 6 Fuel Tube 7 Primary Air Inlet 8 Combustor Exit 9 Bypass 10 Valve 11 Partition Wall 12 Support Pipe 13 Air Supply Section 13a First Ring 13b Second annular ring 14 Premixing pipe 15 Fuel supply pipe 16 Tube 17 Drive mechanism

Claims (2)

[Claims] 1. A fuel injection valve for injecting fuel mixed with air, a support portion slidably fitted to the fuel injection valve on an inner surface, one end connected to the support portion, and the fuel injection valve And an air supply unit that supplies air from the outside to the inside, one end of which is connected to the other end of the air supply unit and the other end of which communicates with the combustion chamber, and which slides on the inner surface of the fuel injection valve. A premixing device comprising: a premixing part that is movably fitted and a drive mechanism that reciprocates a fuel injection valve from a support part to the other end of the premixing part. 2. The position where the fuel injection valve injects fuel is at the other end of the support part and the premixing part, and when it is at the other end of the premixing part, the injection amount of air and fuel is smaller than when it is in the support part. The premixing device according to claim 1, wherein: