COMBUSTION NOZZLE

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2024-006691 filed on January 19, 2024, incorporated herein by reference in its entirety.

BACKGROUND

Technical Field

The present disclosure relates to the technical field of combustion nozzles.

DESCRIPTION OF RELATED ART

Gas turbines that use hydrogen as fuel have been proposed as devices in which a combustion nozzle is used (Japanese Unexamined Patent Application Publication No. 2016-109309 (JP 2016-109309 A), Japanese Unexamined Patent Application Publication No. 2020-106258 (JP 2020-106258 A), and Japanese Unexamined Patent Application Publication No. 2003-148734 (JP 2003-148734 A)).

SUMMARY

When hydrogen is to be used as fuel for a gas turbine, NOx tends to be generated, since hydrogen has a higher combustion temperature than that of hydrocarbon-based fuel that has been commonly used so far. Further, backfire in which combustion flows backward in a fuel flow path tends to occur, since the combustion rate of hydrogen is higher than that of the hydrocarbon-based fuel and the extinction distance (0.64 mm) of hydrogen is shorter than the extinction distance (about 2 mm) of the hydrocarbon-based fuel.

The present disclosure has been made in view of the above issue, for example, and an object thereof is to provide a combustion nozzle capable of both reducing NOx emission and suppressing backfire.

An aspect of the present disclosure provides a combustion nozzle that injects compressed air and fuel to be combusted into a combustion chamber of a combustor of a gas turbine, including: an air flow path through which the compressed air flows out from the combustion nozzle opening toward the combustion chamber to the combustion chamber; and a fuel flow path through which the fuel flows out to the air flow path, in which the combustion nozzle is shaped to expand toward the combustion chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a perspective view illustrating a combustion nozzle according to an embodiment;

FIG. 2 is a cross-sectional view of II-II of FIG. 1;

FIG. 3 is a diagram showing airflow and fuel-flow; and

FIG. 4 is a diagram illustrating an example of a temperature distribution during combustion.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of a combustion nozzle will be described with reference to FIGS. 1 to 4. In the embodiment, hydrogen is used as an example of the fuel. However, the fuel is not limited to hydrogen. A configuration of the combustion nozzle 1 according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view illustrating a combustion nozzle according to an embodiment. FIG. 2 is a cross-sectional view taken along II-II line of FIG. 1.

In FIGS. 1 and 2, the combustion nozzle 1 has a nozzle port 1a. The combustion nozzle 1 is arranged so that the nozzle port 1a comes into contact with a combustion chamber (for example, the combustion chamber 30 shown in FIG. 3) of a combustor of a gas turbine using, for example, hydrogen gas as a fuel. As shown in FIG. 2, the diameter of the nozzle port 1a increases as it approaches the end of the combustion nozzle 1 (the left end of the combustion nozzle 1 in FIG. 2).

The combustion nozzle 1 has an air supply hole 11. Compressed air is supplied to the combustion nozzle 1 from the outside via the air supply holes 11. The combustion nozzle 1 has a swirler 12 through which the compressed air supplied through the air supply holes 11 passes. The swirler 12 is an annular member in which a plurality of stationary blades is arranged in a circumferential direction. The swirler 12 may have a center cone 12a extending along the central axis of the combustion nozzle 1 and a plurality of airfoil 12b (corresponding to the plurality of stationary blades described above) extending radially from the center cone 12a. The swirler 12 may be referred to as an air swirler. In FIG. 2, the nozzle port 1a may mean an area on the left side of the end portion of the center cone 12a.

The combustion nozzle 1 includes a fuel supply pipe 21, a fuel supply passage 22, and a fuel supply hole 23. As shown in FIGS. 1 and 2, the fuel supply hole 23 opens to the nozzle port 1a. Hydrogen gas as fuel is supplied from the fuel supply hole 23 to the nozzle port 1a via the fuel supply pipe 21 and the fuel supply passage 22.

Air flow and fuel flow will be described with reference to FIG. 3. FIG. 3 is a diagram illustrating an air flow and a fuel flow. In FIG. 3, the combustion nozzle 1 is arranged such that the nozzle port 1a is in contact with the combustion chamber 30 of the combustor of the gas turbine. An air supply pipe 40 is connected to the air supply hole 11 of the combustion nozzle 1.

In FIG. 3, solid arrows indicate air flow and dotted arrows indicate fuel flow. As shown in FIG. 3, the compressed air supplied from the air supply pipe 40 to the combustion nozzle 1 via the air supply hole 11 is supplied to the nozzle port 1a via the swirler 12. As described above, the hydrogen gas is supplied from the fuel supply hole 23 to the nozzle port 1a via the fuel supply pipe 21 and the fuel supply passage 22. The compressed air and the hydrogen gas may be mixed in an area indicated by a broken line circle C (i.e., near the border between the nozzle port 1a and the combustion chamber 30).

It can be said that the air supply hole 11, the swirler 12, and the nozzle port 1a of the combustion nozzle 1 constitute a part of the air flow path. Therefore, it can be said that the combustion nozzle 1 includes an air flow path. Similarly, it can be said that the fuel supply pipe 21, the fuel supply passage 22, and the fuel supply hole 23 of the combustion nozzle 1 constitute a part of a flow path of hydrogen gas (i.e., fuel). Therefore, it can be said that the combustion nozzle 1 includes a fuel flow path. As is apparent from FIGS. 2 and 3, in the combustion nozzle 1, the fuel supply hole 23 is formed on the downstream side of the air flow path relative to the air supply hole 11.

As described above, the diameter of the nozzle port 1a increases as it approaches the end portion of the combustion nozzle 1 (the left end portion of the combustion nozzle 1 in FIG. 2). Therefore, the air flow path in the combustion nozzle 1 expands toward the combustion chamber 30. That is, the air flow path in the combustion nozzle 1 gradually increases from the upstream side to the downstream side. Therefore, it can be said that the shape of the combustion nozzle 1 is a shape expanding toward the combustion chamber 30. In other words, the combustion nozzle 1 has a shape that expands toward the combustion chamber 30.

Technical effect

As described above, in the combustion nozzle 1, the flow path is enlarged toward the combustion chamber 30. Therefore, in the region indicated by the broken line circle C in FIG. 3, compressed air (that is, air having a high density) can be actively caused to collide with the hydrogen gas as the fuel. As a result, air and hydrogen gas can be efficiently mixed. Now, description will be given with reference to FIG. 4. FIG. 4 is a diagram illustrating an example of a temperature distribution during combustion. As shown in FIG. 4, the combustion chamber 30 has a relatively high temperature as a whole. This is evidence that air and hydrogen gas are properly mixed.

The flame temperature during combustion of the hydrogen gas is relatively high (e.g., 2000 degrees Celsius or higher). Therefore, if there is a portion where the air-fuel ratio is rich locally due to insufficient mixing between the air and the hydrogen gas, the emission of NOx is increased. On the other hand, in the combustion nozzle 1, since the air-hydrogen gas is appropriately mixed, it is possible to reduce the discharge of NOx. In the combustion nozzle 1, compressed air and hydrogen gas may be supplied so that the air-fuel ratio becomes lean. With this configuration, it is possible to further reduce the emission of NOx.

In order to reduce the emission of NOx, a premixed combustion method has been proposed in which air-fuel (e.g., hydrogen-gas) is mixed in advance. Since the combustion rate of the hydrogen gas is extremely high, in the premixed combustion method, a backfire in which the flame is reversed to the unburned gas (that is, air-fuel pre-mixture) is likely to occur. On the other hand, in the combustion nozzle 1, the compressed air and the hydrogen gas are separately supplied to the nozzle port 1a (further, the combustion chamber 30). That is, the combustion nozzle 1 is a diffusion combustion type combustion nozzle.

In the diffusion combustion system, backfire is less likely to occur than in the premixed combustion system. Now, description will be given with reference to FIG. 4. In the embodiment shown in FIG. 4, a relatively high-temperature area exists near the end of the center cone 12a in the combustion nozzle 1, but it can be said that the inside of the combustion nozzle 1 is kept at a relatively low temperature. This is evidence that there is no flame penetration due to flashback in the combustion nozzle 1.

From the above, according to the combustion nozzle 1, it is possible to reduce the emission of NOx by promoting the mixing of air and hydrogen gas as fuel. According to the combustion nozzle 1, it is possible to suppress the breakage of the component due to flashback and the reduction in the life of the component. In other words, according to the combustion nozzle 1, it is possible to achieve both a reduction in the discharge of NOx and a prevention of flashback.

Aspects of the disclosure derived from the above-described embodiments are described below.

A combustion nozzle according to an aspect of the present disclosure is a combustion nozzle that ejects compressed air and fuel to be combusted into a combustion chamber of a combustor of a gas turbine, the combustion nozzle comprising: an air flow path through which compressed air flows out of the combustion nozzle that opens toward the combustion chamber to the combustion chamber; and a fuel flow path through which fuel flows out to the air flow path, wherein a shape of the combustion nozzle is a shape that expands toward the combustion chamber.

The combustion nozzle has a nozzle port opening toward the combustion chamber, and the nozzle port has a shape expanding toward the combustion chamber. Here, the nozzle port constitutes a part of the air flow path, and the air flow path gradually increases from the upstream side toward the downstream side.

The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope and spirit of the disclosure that can be read from the claims and the entire specification, and a combustion nozzle with such a modification is also included in the technical scope of the present disclosure.