JPH0125907Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a gas turbine combustor, and specifically relates to an improvement of a gas turbine combustor that stabilizes combustion under low load.

[Technical background of the invention and its problems]

Although a wide variety of fuels can be used in gas turbines, in practice there are considerable limitations depending on the fuel used. In particular, special consideration is required when using low-calorie gas such as coal gasified fuel. Low calorie gas has a low calorific value
The calorific value is about 600 to 1200 Kcal/Nm ³ , which is extremely low at 1/7 to 1/16 compared to general fuel. When using such low calorie gas, the gas fuel will reduce the total flow rate.
It ranges from 20 to 40%. Furthermore, the stable flame range of such low-calorie gases is much narrower than that of general fuels, and the mixing ratio of air and fuel must be kept close to the stoichiometric ratio in the combustion region. Even if the combustor is designed with these considerations in mind, the flame will become unstable at low loads due to the nature of gas turbines. This is because in a normal gas turbine, when the load is reduced, the fuel flow rate decreases in approximately proportion to the load, but the intake air flow rate of a gas turbine is reduced as long as the rotation speed is constant unless controlled by an inlet guide vane. It does not decrease even if dropped. In other words, when the load becomes low, the air firing ratio in the combustion region increases, the flame becomes unstable, and there is a risk of it blowing out. This is noticeable when low calorie gas is used, but the same can be said for general fuels.

[Purpose of invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a gas turbine combustor that maintains a constant air-fuel ratio in the combustion zone and maintains a stable flame when the gas turbine is under low load.

[Summary of the idea]

In order to achieve the above object, the present invention has a transient piece that is slidably joined to one end of an inner cylinder incorporated in an outer cylinder, and an injection valve provided at the other end of the inner cylinder. In a gas turbine combustor that sends combustion gas from the combustion chamber to the turbine through a transient piece, vent holes whose opening axes coincide with each other are provided at the junction between the inner cylinder and the transient piece to reduce heat transfer during high combustion loads. Accordingly, the vent shaft is characterized in that the shafts of the respective vent holes are moved.

[Example of idea]

Embodiments of the present invention will be described below, but prior to that, the points of view of the present invention will be explained.

In current gas turbines, the combustor outlet temperature is approximately 1100°C at base load, and when the load is reduced, this temperature drops to approximately 800°C at 50% load and to approximately 500°C at no load. The elongation difference Δl due to the temperature change inside the combustor is expressed as Δl=l×ΔT×α. Here, l is the total length of the combustor, α is the coefficient of linear expansion,
ΔT is the temperature difference. Now, the total length of the combustor is approximately 2,
000mm, and if the load changes from no load to base load, the combustor will extend by about 14mm. If the combustor cylinder is a two-cylinder type (liner and transition piece), supported at both ends, and has a structure that absorbs expansion and contraction at the joint, the cylinder will expand by approximately 14 mm at the joint due to changes in gas turbine operation. I will have to move. Therefore, this joint part is made appropriately long, overlapped, and a large number of ventilation holes are provided in that part. During no-load operation, these holes are fully opened, allowing a large amount of air to flow and reducing the amount of air flowing into the combustion area. As the combustion temperature increases, the vents shift due to thermal expansion and gradually close, becoming fully closed at base load, increasing the amount of air flowing into the combustion zone. By structuring the combustor in this manner, the air-fuel ratio in the combustion zone does not change significantly depending on the load, making stable combustion possible.

A specific example of the present invention will be explained below.

In FIG. 1, reference numeral 1 indicates an outer cylinder of a gas turbine, and an inner cylinder 2 extends along the axis of the outer cylinder 1, forming a combustion chamber 6. As shown in FIG. In addition, the inner cylinder 2
An injection valve 1a is provided at one end of the fuel injection valve 1a, and fuel from the injection valve 1a is sprayed into the combustion chamber 6 to generate high-temperature combustion gas.

High-pressure air from, for example, an air compressor is introduced into the outer cylinder 1 through an inlet 5, and the introduced high-pressure air passes through a passage 5b defined by a side wall 5a and an inner cylinder 2, and from the injection valve 1a. contributes to the combustion of

A transient piece 3 is slidably joined to the other end of the inner cylinder 2, and this transient piece 3 has the function of a diff user so that the mouth becomes looser and narrower toward the tip. High-speed combustion gas is fed to a turbine (not shown).

The other end of the transient piece 3 is an enlarged opening, and this enlarged opening overlaps with the end of the inner cylinder 2 to form a free end 4 which can be expanded and contracted. This free end 4 is
Ventilation holes are drilled so that the axes of the openings coincide when it is static. That is, FIGS. 2 and 3 are partially enlarged views showing the operation of the vent due to heat transfer, and when the gas turbine is under extremely low load, as shown in FIG. The vent 7b provided in the inner cylinder 2 and the vent 7a provided in the free end 4 of the inner cylinder 2 have their through-hole axes aligned, so that the high-pressure air introduced from the outer cylinder 1 flows as shown by the arrow.

Next, when the load becomes relatively high, the vent holes 7a and 7b provided in the free end 4 move due to heat, and as shown in FIG. almost no longer flows into the combustion chamber. Therefore, when low-calorie fuel is used as fuel for the gas turbine, high-pressure air does not flow near the injection valve in large amounts during ignition or at extremely low load, so the phenomenon of flame blow-out can be prevented. Furthermore, when the load is high, the vents 7a and 7b enter in the direction of closing, so that a large amount of high-pressure air flows near the injector, which greatly contributes to the combustion of the injector.

[Effect of idea]

As mentioned above, since the present invention provides a vent at the joint between the free end of the inner cylinder and the free end of the transient piece, it is possible to send high-pressure air suitable for low-calorie fuel, and as a result, good combustion gas is produced. is expected to produce.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the gas turbine combustor according to the present invention, Figure 2 is an operational diagram showing the flow of air from the joint between the inner cylinder and the transient piece at extremely low loads, and Figure 3 is a FIG. 6 is an operation diagram showing the flow of air from the joint between the inner cylinder and the transient piece under load. 1...Outer cylinder, 2...Inner cylinder, 3...Transient piece, 4...Free end, 7a, 7b...Vent hole.

Claims (1)

[Scope of utility model registration request] It has a transient piece that is slidably joined to one end of the inner cylinder that is incorporated into the outer cylinder, and the combustion gas from the injection valve provided at the other end of the inner cylinder is sent to the turbine through the transient piece. In a gas turbine combustor, vents with matching axes are provided at the junction between the inner cylinder and the transient piece, and the axes of the vents are moved by heat transfer during high combustion loads. A gas turbine combustor characterized by a gas turbine combustor.