JPH05179902A - Gas turbine air-cooled cascade blade - Google Patents

Abstract

PURPOSE:To secure a large heat transfer rate with cooling air through relatively small flow resistance, thereby improving cooling performance and heat efficiency by installing each projection in each tip of fins at specified intervals, in these fins being projected so as to be crossed with the cooling air in the inner part of a blade. CONSTITUTION:In a gas turbine air-cooled cascade blade, cooling air is made to flow in the inner part of a blade 4, while a lot of fins 1 are projected out of a wall surface 3 of the blade 4 at a specified angle (for example, 60 deg.) so as to be crossed with a flow of the cooling air. In this case, each rectangular projection 2 is installed in respective tips (apex) at specified intervals. In succession, the height (h) from the wall surface 3 to a base of the projection 2 and height H from the wall surface 3 to a tip part of the projection 2 are set up in each fin 1 respectively. With this constitution, when the flow of the cooling air goes beyond each fin 1 and each projection 2, a heat transfer rate with the large cooling air is securable with relatively small flow resistance. Therefore the extent of cooling performance is improved and, what is more, such an air-cooled cascade blade as resistible to high temperature is thus securable.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to gas turbine air cooling blades, and more particularly to cooling fins therein.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are schematic perspective views of the interior of a conventional gas turbine air cooling blade. In both figures, 1 is a fin for cooling promotion which is projected from the wall surface 3 of the blade at a height h so as to intersect with the cooling air flow. FIG. 3 shows an example in which the fins 1 cross at a substantially right angle to the cooling air flow, and FIG. 4 shows an example in which the fins 1 cross at an angle of approximately 60 °.

It can be seen from the literature (Transaction of the ASME, Journal of Heat Transfer) that the heat transfer rate (and hence the cooling rate) is improved when the oblique crossing as shown in FIG. Tenth
7, vol. 628-635 (1985)).

[0004]

The above conventional gas turbine air cooling blade has the following problems to be solved.

That is, the fins shown in FIGS. 3 and 4 separate the cooling air flow to give turbulence to the flow behind the fins.
It increases the heat transfer rate.

As the height of the fins is increased, the peeling that occurs behind the fins becomes more severe and the heat transfer rate is improved, but on the other hand, the flow resistance is increased. That is, in the case of a gas turbine air cooling blade, since the inlet pressure and the outlet pressure of the convective cooling air inside the blade are regulated, the flow velocity of the cooling air decreases as the flow resistance increases, and the heat transfer coefficient increases. There was a problem of lowering.

Therefore, it is necessary to suppress the increase in flow resistance to a minimum while improving the heat transfer coefficient.

In order to solve the above problems, it is an object of the present invention to provide a gas turbine air cooling blade having a higher rate of increase in heat transfer rate than an increase in flow resistance.

[0009]

As a means for solving the above-mentioned problems, the present invention provides a gas turbine air-cooling blade in which cooling air is flown into the blade for promoting cooling and a fin intersecting with the cooling air flow is projected. SUMMARY OF THE INVENTION An object of the present invention is to provide a gas turbine air-cooling blade, characterized in that the tips of the blades are provided with protrusions at required intervals.

[0010]

Since the present invention is constructed as described above, it has the following actions.

That is, when the fins project while intersecting with the cooling air flow in the blade, the flow is disturbed behind them. It is a well known fact that turbulent flow generally has a higher heat transfer coefficient than laminar flow.

Turbulence behind the fins accordingly increases the heat transfer coefficient.

On the other hand, the flow resistance is roughly divided into the form in which the dynamic pressure resistance and the turbulence resistance including vortices are added in the projection body.

Therefore, if the dynamic pressure resistance is small and the turbulence resistance is allowed to increase, it is possible to obtain a protrusion having a larger heat transfer coefficient than the resistance increase.

In the structure of the present invention, since the projections are provided at the required intervals at the tips of the fins which are projected so as to intersect the cooling air flow, the flow is generated by generating vortices or the like as compared with the area where the projections block the flow. The outer peripheral portions of the disturbing protrusions are present on both the left and right sides (in the flow direction) of the protrusions and the tips (tops). That is, since the outer peripheral line of turbulence is longer than the area where the dynamic pressure resistance is generated, the heat transfer coefficient is larger than the flow resistance.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The same components as those in the conventional example are designated by the same reference numerals, and the description thereof will be omitted unless necessary.

FIG. 1 is a schematic perspective view of a part of one side of the inside of the gas turbine air cooling blade of the present embodiment shown corresponding to the conventional example, and FIG. 2 is a gas turbine air cooling blade to which the embodiment of FIG. 1 is applied. It is sectional drawing of the whole inside.

In both figures, 1 is for cooling air flow,
Fins provided so as to project from the wall surface 3 of the blade 4 intersecting at an angle of about 60 °, 2 is a rectangular projection in which the tip (top portion) of the fin 1 is projected in a rectangular shape at a required interval, and 3 is the inside of the blade 4. Walls 4 are blades configured to allow cooling air to flow therethrough.

The rectangular projections 2 are provided in a staggered arrangement among the plurality of fins 1 as shown in the drawing in order to improve the collision efficiency of the cooling air.

The height from the wall surface 3 to the tip of the rectangular protrusion 2 is H, and the height from the base portion is h. In addition, here the rectangular protrusion 2
Seeing it as the addition of multiple independent bodies, or fin 1
Needless to say, even if the tops of the are formed in a concavo-convex pattern at a required interval, and the projections are the same.

Next, the operation of the above configuration will be described.

In FIG. 1, when the cooling air flows as shown by an arrow, the cooling air flows by raising the height h and the height H of the fin 1. Therefore, the subsequent flow is turbulent, but if the fins 1 were uniform at the height h, that is, the fins were uniform at the height H, that is, the fins 1 were uniform at the height H. Comparing the cases, in the case of the height H, since the height from the wall surface 3 and the head difference from the view of the overflow are large, the turbulence is naturally large, and thus the heat transfer coefficient is also large. On the other hand, looking at the flow resistance, the resistance due to turbulence increases correspondingly because the turbulence has increased. The dynamic pressure resistance also increases correspondingly since the height has increased from h to H. That is, when the height is H with respect to h, the turbulence increases and the heat transfer coefficient also increases correspondingly, but the dynamic pressure resistance and the turbulence resistance also increase correspondingly, so the heat transfer coefficient / resistance viewpoint From
Whether increasing h to H is always efficient requires detailed testing.

On the other hand, in the case of this embodiment, the rectangular protrusion 2
2 and 2, the height of the fin 1 is h, and if the spacing between the rectangular protrusions 2 and the width of the rectangular protrusion 2 are the same, the area for the flow of the fin 1 between the height h and H is: It is half of the area difference for each uniform height of h and H. Therefore, the dynamic pressure resistance is correspondingly reduced. However, as for the turbulence, the turbulence due to the drop between the rectangular protrusions 2 is correspondingly reduced, but there are two new turbulences due to the side portions of the rectangular protrusions 2.
As a result, the total turbulence does not become small.
Therefore, in the case of the present embodiment, even if the total resistance becomes small, the turbulence hardly becomes small, and the heat transfer coefficient / resistance is obviously larger than the above, and a large heat transfer coefficient is achieved with a small resistance. In addition to the above, since the rectangular protrusions 2 are arranged in a zigzag manner in FIG. 1, the main part of the flow passing between the rectangular protrusions 2 hits the rectangular protrusions 2 of the fins 1 in the wake, and the turbulence efficiency is Therefore, the heat transfer coefficient is further increased. Further, since the fins 1 intersect the cooling air flow at an oblique angle of about 60 °, a high heat transfer coefficient can be obtained also from this point. However, the staggered arrangement of the rectangular protrusions 2 and the configuration in which the fins 1 cross the cooling air flow at an angle are arbitrary, and the present invention is not limited thereto.

Incidentally, according to the literature cited in the section of the prior art, the inclination angle of the fin with respect to the flow direction is 45 to 75.
In the case of °, the heat transfer coefficient is increased by about 25% compared with the case of 90 ° (orthogonal). In this embodiment, 60 ° is a typical value in this range.
Is adopted.

FIG. 2 is a sectional view of the inside of the gas turbine air-cooling blade of the embodiment of FIG. 1, in which the blades 4 are alternately partitioned by partition walls 4a in order to lengthen the cooling passage and enhance cooling efficiency.
The cooling air meanders between them and cools the blades 4 sufficiently.

As described above, according to the present embodiment, since the tips of the fins 1 are provided with the rectangular protrusions 2 at required intervals, the turbulence becomes large as compared with the resistance of the flow of the cooling air, and the wall surface 3 is efficiently used.
And therefore the blade 4 can be cooled.

[0027]

Since the present invention is constructed as described above, it has the following effects.

That is, according to the present invention, since the tips of the fins projecting so as to intersect the cooling air flow are provided with projections at a required interval inside the gas turbine air cooling blade, heat transfer with the cooling air flow is provided. The cooling rate is improved, the cooling performance is improved, and an air cooling blade that can withstand higher temperature gas can be obtained. As a result, the heat coefficient of the gas turbine is improved.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a part of one side of an inside of an embodiment of the present invention,

FIG. 2 is a sectional view of the entire inside of the gas turbine air-cooling blade (moving blade) of the above embodiment,

FIG. 3 is a perspective view of a part of the inside of a gas turbine air cooling blade having fins arranged orthogonal to the conventional flow;

FIG. 4 is a perspective view of a part of the inside of a gas turbine air-cooling blade having fins arranged to be inclined with respect to a conventional flow.

[Explanation of symbols]

 1 fin 2 rectangular protrusion 3 wall surface 4 blade 4a partition wall

Claims (1)

[Claims] 1. A gas turbine air-cooling blade in which cooling air is flown into the blade to promote cooling, and fins intersecting with the cooling air flow are projected, wherein the tips of the fins are provided with projections at required intervals. A gas turbine air cooling blade characterized by.