JPH10306704A - Gas turbine blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy the cooling performance to be required as a turbine blade, with a low steam amount by making a ratio of the thickness of a gas turbine blade cooled by passing through the steam to the length of a chord a specific value or less. SOLUTION: The steam for cooling flows in a turbine stationary blade 2, for example, from a basic end of a passage (a) of turbine in a radial direction, is returned on the next passage of turbine at a point thereof, and then flows similarly, to cool the stationary blade 2. On this occasion, the more a ratio (t/c) of the thickness of the blade 2 to the length of a chord is reduced, the more a steam flowing speed is increased under a condition that the steam flowing amount is constant. Further the heat conductivity is similarly increased. Whereby by adjusting t/c to be not more than 0.15 corresponding to the minimum heat conductivity required by the cooling performance of the blade, the blade can be effectively cooled, and the low steam flowing amount suitable as a combined cycle, can be kept. Even when the steam is leaked, the plant performance is hardly affected thereby, because the original steam amount for cooling is small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas turbine blade applied to a case where steam is efficiently cooled by passing steam through the blade of the gas turbine.

[0002]

2. Description of the Related Art A conventional combined cycle gas turbine is shown in FIGS. In the gas turbine 1, turbine vanes 2 and rotor blades 4 are alternately arranged. In addition, stationary blade 2
Is provided with a cooling steam pipe 3. Further, a plurality of radial flow paths a are provided in the stationary blade 2 as shown in FIG.

In the above, a high-temperature mainstream gas is sent from a combustor (not shown) to the gas turbine 1 and acts on the moving blades 4 via the stationary blades 2 to rotate the rotor at high speed to generate power. At this time, the cooling steam 3 is supplied from the cooling steam pipe 3 to the stationary blade 2, flows in the blade 2 in the radial direction, and is cooled from the inner surface. Then the steam is sent to the next system.

As described above, in the combined cycle, steam cooling has been proposed in order to improve thermal efficiency.

FIGS. 7 to 9 show conventional impingement cooling by air. Inserts 5a to 5c having a predetermined interval from the inner surface and having a large number of holes are inserted into the radially divided section of the stationary blade 2. The surface of the wing 2 is also provided with a predetermined pattern of holes.

[0006] Cooling air enters the inserts 5a to 5c and blows out from the respective holes toward the inner surface of the wing 2 to cool as shown in FIG. Thereafter, the film is ejected from the holes on the surface to cool the film.

[0007]

The above-mentioned prior art has the following problems.

(1) In the case of impingement cooling, the ratio t / c of the blade thickness to the cord length is usually 0.2 or more in order to facilitate the insertion of the insert and to make the pressure distribution in the insert uniform.

When a blade having the same shape as that of t / c is used for steam cooling, a large amount of steam is required because convection cooling is required for steam cooling.

(2) Therefore, most of the steam for the combined cycle steam turbine may be required. Furthermore, if there is a leak in the steam cooling pipe, the influence on the combined cycle (bottoming cycle) is large, and the plant may not function.

(3) The diameter of a complicated steam cooling pipe becomes large, and its cost, space, and pipe management become problems.

[0012]

The present invention employs the following means to solve the above-mentioned problems.

That is, in a gas turbine blade cooled through steam, the ratio of the blade thickness of the gas turbine blade to the cord length is set to 0.15 or less.

In the above, the cooling steam flows through the turbine blades to cool the blades. In this case, assuming that the steam flow rate is constant, the steam flow rate increases as the ratio of the blade thickness to the cord length, t / c, decreases. The heat transfer coefficient also increases.

Therefore, by setting t / c to 0.15 or less, which corresponds to the minimum heat transfer coefficient required from the cooling performance of the blade, the blade is effectively cooled, and the appropriate steam flow rate as a combined cycle is achieved. Can be maintained.

Therefore, even if steam leaks,
Since the original amount of cooling steam is small, the effect on plant performance is small. Further, the diameter of the steam pipe can be reduced. This helps save cost and space in the complex piping system of the plant.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The parts described in the conventional example are assigned the same reference numerals, and the description thereof will be omitted. The parts related to the present invention will be mainly described.

In FIG. 1, the profile t / c of the gas turbine stationary blade 2 for steam cooling is set to 0.15 or less.

In the above description, the cooling steam flows in the turbine vane 2 in the radial direction, for example, from the base end of the flow path a, returns to the next flow path at the tip end, and then flows sequentially in the same manner. Cool 2

In this case, if the steam flow rate is constant, FIG.
As shown in the figure, the steam flow velocity increases as the ratio of the blade 2 thickness to the cord length, t / c, decreases. The heat transfer coefficient also increases as shown in FIG.

[0021] Therefore, by setting 0.15 corresponding to t / c the minimum heat transfer coefficient alpha ₁ required from the cooling performance of the wing, with the wing is effectively cooled, suitable as a combined cycle Low steam flow can be maintained.

Therefore, even if there is steam leakage,
Since the original amount of cooling steam is small, the effect on plant performance is small. Further, the pipe diameter of the steam pipe 3 can be reduced. This helps save cost and space in the complex piping system of the plant.

[0023]

As described above, according to the present invention, since the ratio of the blade thickness to the cord length is set to 0.15 or less, it is possible to satisfy the cooling performance required for a turbine blade with a low steam amount. Can be.

[Brief description of the drawings]

FIG. 1 is a sectional view of a stationary blade according to an embodiment of the present invention.

FIG. 2 is an operation explanatory view of the above-described embodiment.

FIG. 3 is an operation explanatory view of the embodiment.

FIG. 4 is a cross-sectional view of the gas turbine according to the embodiment and the conventional example.

FIG. 5 is a detailed view of a stationary blade of the conventional example.

6 is an AA view of FIG. 5 of the conventional example.

FIG. 7 is a longitudinal sectional view of another example of the stationary blade of the conventional example.

FIG. 8 is a cross-sectional view of another example of the conventional stationary vane.

FIG. 9 is a detailed view of a portion B in FIG. 8 of another example of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas turbine 2 Turbine stationary blade 3 Cooling steam pipe 4 Moving blade 5a-5b Insert t Blade thickness c Cord length

Claims (1)

[Claims] 1. A gas turbine blade for cooling through steam, wherein a ratio between a blade thickness of the gas turbine blade and a cord length is 0.15 or less.