TECHNICAL FIELD

The present invention relates to a gas turbine.

Priority is claimed on Japanese Patent Application No. 2017-066598, filed Mar. 30, 2017, the contents of which are incorporated herein by reference.

BACKGROUND ART

A gas turbine has a compressor, a combustor accommodated in a casing, a diffuser, and a turbine.

The compressor generates compressed air. The generated compressed air is supplied to a space in the casing.

The combustor generates combustion gas using the compressed air. The turbine rotates a rotor with the combustion gas.

The diffuser connects an outlet of the compressor and an entrance side of the casing. A flow path whose cross-sectional area gradually increases from the compressor toward the casing is defined in the diffuser. The diffuser converts a dynamic pressure of the compressed air into a static pressure.

The dynamic pressure of the compressed air is preferably converted into the static pressure by the diffuser as much as possible. However, if an angle of a circumferential wall of the diffuser becomes too large with respect to a main flow of the compressed air, a boundary layer may be separated from an inner wall surface of the diffuser. When such separation of the compressed air occurs, pressure loss increases and efficiency of the entire gas turbine decreases.

In addition, a flow rate distribution (in other words, a pressure distribution) in a radial direction of a rotating shaft of the gas turbine is formed in the compressed air flowing into the flow path in the diffuser. For this reason, the separation of the compressed air easily occurs on an inner surface side of the flow path in the diffuser. Thus, there is a possibility of increasing the pressure loss in the casing.

Patent Document 1 discloses that, by disposing a splitter unit inside a flow path in a diffuser, the compressed air is divided into two flows and supplied to a space in a casing.

CITATION LIST

Patent Literature

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2010-223223

SUMMARY OF INVENTION

Technical Problem

Meanwhile, in the case of disposing the splitter unit inside the flow path in the diffuser as in Patent Document 1, it is required to enlarge a diameter of the flow path of the diffuser at a portion where the splitter unit is disposed. When the diameter of the flow path (diffuser) in the diffuser is enlarged, there is a possibility that a boundary layer may be separated from an inner wall surface of the diffuser and pressure loss in the casing may increase.

In addition, in the case of disposing the splitter unit inside the flow path in the diffuser as in Patent Document 1, since it is difficult to sufficiently reduce a flow rate of the compressed gas, there is a possibility that pressure loss in the casing may increase.

Therefore, it is an object of the present invention to provide a gas turbine which can inhibit pressure loss from being reduced in a casing.

Solution to Problem

In order to solve the above problems, a gas turbine according to one aspect of the present invention includes a compressor which compresses gas to generate compressed gas, a casing in which a space is formed, a combustor which is disposed in the space of the casing and generates combustion gas using the compressed gas, a turbine which is provided downstream from the combustor and is driven by the combustion gas, a diffuser which connects an outlet of the compressor and an entrance of the casing, is gradually enlarged in diameter from the outlet of the compressor toward the entrance of the casing, and defines a flow path that guides the compressed gas to the space, a flow guide provided on an outlet side of the diffuser in the space formed in the casing, and a rotor disposed from the compressor to the turbine. The flow guide includes a first guide surface which is provided on the rotor side and delays turning of a flow direction of the compressed gas that has passed through the diffuser, and a second guide surface which is disposed outside the first guide surface and turns the flow direction of the compressed gas that has passed through the diffuser.

According to the present invention, by providing the flow guide having the first and second guide surfaces on the outlet side of the compressor in the space formed in the casing, it is possible to delay turning of the compressed gas whose flow rate has been reduced by the diffuser. Moreover, it is possible to cause a portion in the casing provided with the flow guide to serve as a diffuser. That is, a length of a portion serving as the diffuser can be increased.

As a result, since it is possible to sufficiently reduce the flow rate of the compressed gas flowing into the space in the casing, pressure loss in the casing can be reduced.

Also, in the gas turbine according to one aspect of the present invention, a leading edge of the flow guide may be disposed downstream from an outlet of the diffuser.

In this way, by disposing the leading edge of the flow guide downstream from the outlet of the diffuser, the entire flow guide can be disposed in the space formed in the casing.

Also, in the gas turbine according to one aspect of the present invention, the leading edge of the flow guide may be disposed at a position which coincides with the outlet of the diffuser or at a position upstream from the outlet of the diffuser.

In this way, by disposing the leading edge of the flow guide at the position which coincides with the outlet of the diffuser, or at the position upstream from the outlet of the diffuser, turning of the flow direction of the compressed gas inside the diffuser can be delayed by the first guide surface, and the flow direction of the compressed gas can be turned by the second guide surface.

Also, in the gas turbine according to one aspect of the present invention, the first guide surface may be parallel to an axis of the rotor.

In this way, by making the first guide surface parallel to the axis of the rotor, turning of the compressed gas flowing along the first guide surface can be delayed.

Also, in the gas turbine according to one aspect of the present invention, the first guide surface may be inclined in a direction approaching the axis of the rotor from the leading edge toward a trailing edge of the flow guide.

In this way, by inclining the first guide surface in the direction approaching the axis of the rotor from the leading edge toward the trailing edge of the flow guide, turning of the compressed gas can be further delayed as compared with a case in which the first guide surface is set to be parallel to the axis of the rotor.

Also, in the gas turbine according to one aspect of the present invention, the second guide surface may be a curved surface which curves in a direction going away from the axis of the rotor from the leading edge toward the trailing edge of the flow guide.

In this way, by using the curved surface, which curves in the direction going away from the axis of the rotor from the leading edge toward the trailing edge of the flow guide, as the second guide surface, turning of the compressed gas flowing along the second guide surface can be smoothly performed.

Also, in the gas turbine according to one aspect of the present invention, the diffuser may include a first tubular portion, and a second tubular portion which is disposed outside the first tubular portion and defines the flow path between the first tubular portion and the diffuser, and the flow guide may have an annular shape, and may include a plurality of struts which connect the first tubular portion and the second tubular portion in a radial direction of the rotor, are disposed in a circumferential direction of the rotor, and support the flow guide.

By having the plurality of struts configured in this way, the flow guide can be disposed at a predetermined position with respect to the flow path formed between the first tubular portion and the second tubular portion.

Also, in the gas turbine according to one aspect of the present invention, shapes of the plurality of struts may be blade shapes.

In this way, by making the shapes of the plurality of struts into blade shapes, the compressed gas can be efficiently passed in a direction from leading edges to trailing edges of the plurality of struts.

Also, in the gas turbine according to one aspect of the present invention, the plurality of struts may be disposed to partially overlap the combustor in the circumferential direction of the rotor, and inner sides of leading edge portions of the plurality of struts may be inclined to form an acute angle with respect to the axis of the rotor.

In this way, by inclining the inner sides of the leading edge portions of the plurality of struts to form an acute angle with respect to the axis of the rotor, it is possible to inhibit a local pressure increase on the outlet side of the diffuser due to influence of a potential at leading edges of the plurality of struts. Thus, since it is possible to reduce the flow rate of the compressed gas which flows into the space in the casing, pressure loss in the casing can be inhibited.

Also, in the gas turbine according to one aspect of the present invention, the first tubular portion may include an outer circumferential surface facing the second tubular portion, the second tubular portion may include an inner circumferential surface facing the first tubular portion, and a first angle formed by the axis of the rotor and the outer circumferential surface may be smaller than a second angle formed by the axis of the rotor and the inner circumferential surface.

In this way, by making the first angle formed by the axis of the rotor and the outer circumferential surface of the first tubular portion smaller than the second angle formed by the axis of the rotor and the inner circumferential surface of the second tubular portion, a turning angle of the compressed gas flowing along the first guide surface can be reduced.

In addition, since it is possible to increase a cross-sectional area of the flow path in the diffuser by making the second angle larger than the first angle, the function of the diffuser (specifically, the function of converting the dynamic pressure of the compressed gas into a static pressure) can be enhanced.

Advantageous Effects of Invention

According to the present invention, pressure loss in the casing can be reduced.

