JP4446150B2 - Gas turbine purge air blowing method and blowing structure - Google Patents

Description

  The present invention relates to a gas turbine purge air blowing method and a blowing structure.

  FIG. 3 is a schematic configuration diagram of a turbojet engine, which includes an air intake 101, a compressor 102, a combustor 103, a gas turbine 104, an afterburner 105, a jet nozzle 106, and the like. In such a turbojet engine, air is introduced from the air intake port 101, this air is compressed by the compressor 102, fuel is combusted in the combustor 103, and high-temperature combustion gas is generated. The turbine 104 is driven, the compressor 102 is driven by the gas turbine 104, the fuel is again combusted by the exhaust gas discharged from the turbine by the afterburner 105, the high-temperature combustion exhaust gas is expanded by the jet nozzle 106, and is ejected backward. It is designed to generate thrust. This configuration is the same for jet engines other than turbojet engines.

  FIG. 4 is a partially enlarged view of the gas turbine 104 of FIG. As shown in this figure, a gas turbine of a jet engine includes a stationary blade row in which a plurality of stationary blades 1 are arranged in the circumferential direction, and a moving blade in which a plurality of moving blades 3 that rotate together with a shaft 107 are arranged in the circumferential direction. It consists of columns. A stationary blade inner band 2 and a moving blade inner band 4 are connected to the radially inner ends of the stationary blade 1 and the moving blade 3, and between the stationary blade inner band 2 and the moving blade inner band 4, respectively. The gap 10 for blowing out purge air is formed over the entire circumference. Further, the rotor blade inner band 4 includes a platform 4a facing the combustion gas flow path, a protruding portion 4c positioned radially inward of the tip end portion of the platform 4a and extending in the axial direction, the tip end portion of the platform 4a, and the protruding portion. It has the connection part 4b which connects the rear-end part of 4c.

  In the gas turbine configured as described above, the flow direction of the combustion gas generated in the combustor 103 is directed to the direction suitable for the moving blade 3 by the stationary blade 1, and the moving blade 3 is rotationally driven by this combustion gas. In addition, the cooling air 9b (purge air) for cooling the turbine disk front and the like is supplied from the radially inner side to the combustion gas main flow 9a, blows out from the gap 10 through the flow path 21, and mixes with the main flow 9a. It flows into the moving blade 3 on the downstream side. In this figure, the stationary blades 1 and the moving blades 3 are shown one by one, but usually two or more rows of stationary blades and moving blades including the uppermost stage are provided. The gas turbine purge air blowing technique as described above is disclosed in, for example, Patent Document 1 below.

JP 2002-221001

  In recent years, the amount of cooling air (purge air 9b) tends to increase as the temperature at the turbine inlet increases and the load increases. However, since the purge air 9b is mixed with the main flow at a relatively large angle φ with respect to the axial direction as shown in FIG. 4, this mixing causes an energy loss called a mixing loss, which lowers the aerodynamic performance of the turbine.

  That is, the purge air 9b at the turbine disk front, which is a part of the cooling air, has a relatively large angle with respect to the flow direction of the main flow 9a at the turbine stationary blade outlet where the flow of the main flow 9a is supersonic (Mach number 1 or more). Since the air is blown out, the mixing loss per flow rate is large compared to the cooling air in other parts, and there is a problem that the aerodynamic performance of the turbine is also adversely affected. As a means for solving such a problem, it is possible to reduce the mixing loss by reducing the supply amount of the purge air 9b. However, since the necessity of the purge air 9b is large as described above, the supply amount is reduced. It is difficult to reduce it.

  The present invention has been developed to solve such problems. That is, an object of the present invention is to reduce mixing loss caused by purge air blown out from between the stationary blade inner band and the moving blade inner band (turbine disk front) and mixed with the main flow without reducing the supply amount of the purge air. An object of the present invention is to provide a gas turbine purge air blowing method and a blowing structure capable of improving aerodynamic performance.

In order to achieve the above object, according to the present invention, there is provided a gas turbine purge air blowing method in which purge air is blown from between a stationary blade inner band and a moving blade inner band and mixed with a main flow of a combustion gas flow path. The blade inner band includes a platform facing the combustion gas flow path, a front portion extending radially inward from the tip of the platform, and a radially inner side of the platform tip than the radially inner end of the front portion. A projecting portion that is located radially outward and projects forward in the axial direction from the front portion, and the front portion includes a connecting portion that forms a portion from a tip of the platform to a base portion of the projecting portion, and An inward forming portion that constitutes a portion from the base portion of the projecting portion to the radially inner end portion of the front portion. -Platform and the connection portion surface between the connecting portion and a curved shape, a through hole for passing the purge air supplied from the radially inward root portion of the protruding portion is provided, the base entirety of the projecting portion of the through hole And the outer peripheral surface of the through hole that defines the through hole is closed, and the through hole extends from the radially inner side to the radially outer side in the root portion. A purge air that passes through the base portion in a direction along the surface of the rectangular forming portion and the surface of the connecting portion, and that flows radially inward along the surface of the inner forming portion, passes through the through hole in the radial direction. A gas turbine purge air characterized in that it is blown outward and flows along the surface of the connecting portion, and the blown purge air is mixed with the main flow of the combustion gas flow path along the connection portion surface by the Coanda effect. Balloon method is provided.

Further, according to the present invention, there is a gas turbine purge air blowing structure in which purge air is blown out from between the stationary blade inner band and the moving blade inner band and mixed with the main flow of the combustion gas flow path, and the moving blade inner band includes: A platform facing the combustion gas flow path, a front portion extending radially inward from the tip of the platform, and positioned radially inward of the platform tip and radially outward of the radially inner end of the front portion And a projecting portion projecting forward in the axial direction from the front portion, wherein the front portion comprises a connecting portion constituting a portion from a tip of the platform to a base portion of the projecting portion, and a base portion of the projecting portion And an inwardly forming portion constituting a portion from the front portion to the radially inner end of the front portion. The surface of the connecting portion with the connecting portion has a curved surface shape, and the base portion of the protruding portion passes along the surface of the inner forming portion and allows the purge air supplied from radially inward to pass along the surface of the connecting portion. And the entire through hole is located at the base of the protruding portion, the outer peripheral surface of the through hole defining the through hole is closed, and the through hole is A gas turbine characterized in that, at the base portion, the base portion is penetrated from the radially inward side to the radially outward side in a direction along the surface of the inner forming portion and the surface of the connecting portion. A purge air blowing structure is provided.

  According to the present invention, the surface of the connecting portion between the platform and the connecting portion has a curved surface shape, and the through hole through which purge air supplied from the radially inner side passes is provided at the base portion of the protruding portion, and the connecting portion is connected to the through hole. Since the purge air is blown out along the surface of the part, the blown out purge air is mixed with the main flow of the combustion gas flow path along the surface of the connecting part by the Coanda effect. That is, the purge air is blown out in the direction along the platform, and the mixing angle of the purge air and the main flow can be reduced. Therefore, mixing loss due to purge air mixed with the main stream can be reduced, and turbine aerodynamic performance can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

  The mixing loss that occurs when the main flow 9a and the purge air 9b are mixed can be expressed by (Equation 1). In this equation, the subscript g is the main flow, the subscript c is the cooling air (purge air), the subscript t is the mixing loss, and P, M, W, T, and V are the pressure, Mach number, mass flow rate, absolute temperature, and flow velocity, respectively. is there. Further, κ represents a specific heat ratio, and φ represents a blowing angle. The blowing angle φ is an angle formed by the rotation axis of the gas turbine and the purge air blowing direction as shown in FIG.

  From (Equation 1), it can be seen that the mixing loss ΔPt decreases as the blowing angle φ approaches 0 degrees, and the mixing loss ΔPt increases as the blowing angle φ increases (closer to 90 degrees). That is, as long as the mass flow rate Wc, the absolute temperature Tc, and the flow velocity Vc of the entire purge air are the same, the mixing loss can be reduced if the blowing angle φ can be reduced.

  On the other hand, in the conventional gas turbine purge air blowing means shown in FIG. 4, since the barge air is blown at a large angle with respect to the main flow, it is clear from (Equation 1) that a large mixing loss occurs.

  FIG. 1 and FIG. 2 are diagrams for explaining an embodiment of a gas turbine purge air blowing method and its structure according to the present invention. As shown in FIG. 1, a stationary blade inner band in which the stationary blade 1 and the moving blade 3 are arranged in the flow direction of the combustion gas (main flow 9 a) and connected to the radially inner ends of the stationary blade 1 and the moving blade 3, respectively. A gap 10 for blowing out purge air is formed between 2 and the rotor blade inner band 4 over the entire circumference.

  FIG. 2 is a perspective view of the rotor blade 3 and the rotor blade inner band 4, and will be described below with reference to FIG. 2 in conjunction with FIG. The rotor blade inner band 4 includes a platform 4a facing the combustion gas flow path, a projecting portion 4c extending radially inward of the tip end portion of the platform 4a and extending in the axial direction, and a tip end portion of the platform 4a and the projecting portion 4c. And a connecting portion 4b for connecting the rear end portion. This is the same as in FIG.

  Further, as shown in FIGS. 1 and 2, the surface of the connecting portion between the platform 4a and the connecting portion 4b has a curved surface shape, and at least the curved surface portion has a Coanda effect when a fluid flows on the surface. Has sufficient curvature to cause Further, two through holes 11 through which the purge air 9b supplied from the inside in the radial direction is passed are provided at the base portion (rear end portion) of the protruding portion 4c. The through holes 11 pass through the purge air 9b that has passed therethrough. Is formed so as to flow along the surface of the connecting portion 4b. In the present embodiment, two through holes 11 are provided, but the number is not particularly limited to two.

  During operation of the gas turbine, purge air is supplied from the inside in the radial direction as shown in FIG. The supplied purge air is divided into one that passes through the through hole 11 and one that passes through the flow path 21. Of these, the purge air 9b that has passed through the through-hole 11 flows along the surface of the connecting portion 9b, and when it reaches the connecting portion between the platform 9a and the connecting portion 9b, it is bent along the surface of the connecting portion due to the Coanda effect. That is, the purge air 9b is blown out in the direction along the platform 4a. Therefore, according to the present invention, the mixing angle between the main flow 9a flowing through the combustion gas passage 20 and the barge air 9b is reduced, mixing loss due to purge air mixed with the main flow can be reduced, and turbine aerodynamic performance can be improved. The purge air 9b that has passed through the flow path 21 without passing through the through hole 11 is blown out of the gap 10 at the same angle as the blowing angle in FIG. 4, but the size and number of the through holes 11, and the flow path Mixing loss can be reduced as a whole by adjusting the flow passage area of 21 and designing the flow rate of purge air passing through the through-hole 11 as much as possible.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.

It is a figure which shows embodiment of this invention. It is a perspective view of a moving blade and a moving blade inner band. It is a typical block diagram of a turbojet engine. It is the elements on larger scale of the gas turbine of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator blade 2 Stator blade inner band 3 Rotor blade 4 Rotor blade inner band 4a Platform 4b Connection part 4c Protrusion part 9a Mainstream (combustion gas)
9b Purge air 11 Through hole 20 Combustion gas flow path 21 Flow path 101 Air intake 102 Compressor 103 Combustor 104 Gas turbine 105 Afterburner 107 Shaft

Claims (2)

A gas turbine purge air blowing method in which purge air is blown out from between a stationary blade inner band and a moving blade inner band and mixed with the main flow of the combustion gas flow path,
The blade inner band includes a platform that faces the combustion gas flow path, a front portion that extends radially inward from a tip of the platform, a radially inner end of the front portion that is radially inward of the platform tip. A projecting portion that is located radially outside and projects axially forward from the front portion, and the front portion includes a connecting portion that forms a portion from the tip of the platform to the base of the projecting portion. The inner forming portion constituting a portion from the base portion of the projecting portion to the radially inner end portion of the front portion,
The surface of the connecting portion between the platform and the connecting portion is curved, and a through hole is provided at the base of the protruding portion to allow purge air supplied from the radially inner side to pass . The outer peripheral surface of the through hole that is located at the root portion and that defines the through hole is closed, and the through hole is formed in the root portion from the radially inward side to the radially outward side. Penetrating the root portion in a direction along the surface of the inner forming portion and the surface of the connecting portion,
Purge air that flows from the radially inner side along the surface of the inner forming portion is blown radially outward through the through hole and flows along the surface of the connecting portion. A gas turbine purge air blowing method, characterized in that the gas turbine purge air is mixed with a main flow of a combustion gas flow path along a connection portion surface. A gas turbine purge air blowing structure for blowing purge air from between a stationary blade inner band and a moving blade inner band and mixing it with the main flow of the combustion gas flow path,
The blade inner band includes a platform that faces the combustion gas flow path, a front portion that extends radially inward from a tip of the platform, a radially inner end of the front portion that is radially inward of the platform tip. A projecting portion that is located on the radially outer side and projects forward in the axial direction from the front portion,
The front portion includes a connecting portion that forms a portion from a tip of the platform to a base portion of the protruding portion, and an inner portion that forms a portion from the base portion of the protruding portion to a radially inner end portion of the front portion. Consisting of a forming part,
The connecting portion surface of the platform and the connecting portion has a curved surface shape, and the base portion of the protruding portion allows purge air supplied from the radially inner side along the surface of the inner forming portion to pass through the connecting portion. A through hole that flows along the surface of the through hole, the entire through hole is located at the base of the protruding portion, and the outer peripheral surface of the through hole that defines the through hole is closed, and the through hole The hole penetrates the base portion in the direction along the surface of the inner forming portion and the surface of the connecting portion from the radially inner side to the radially outer side in the root portion. Gas turbine purge air blowing structure.

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