Gas Turbine Engine Blades

Abstract

A gas turbine blade has a hollow interior space which is divided to form flow passages for cooling medium. The flow passages are bounded by the sides of a sheet-like insert the two blade walls, and fins between the insert and the blade walls; they commence at one end of the blade and extend in a spiral-like path around the opposite sides of the insert.

Description

This invention relates to the blading of gas turbine engines, and although not so limited, has particular reference to rotor blades for such engines.

As is known, it is advantageous to provide for the cooling of gas turbine rotor blades, and many different ways of doing this are known. In particular, it is known to provide a cooling air flow through the interior of the blade, and the cooling is the more effective, the greater the volume of air flow and the greater the velocity of the air as it passes through the blade.

In very small rotor blades, e.g., less than 11/2 inches long considerable difficulties are encountered in providing flow channels by means of which satisfactory cooling can be achieved. The present invention aims to provide a rotor or stator blade construction which enables improved cooling to be obtained.

An object of the invention is to provide an improved a gas-turbine blade with a hollow interior space which is divided to form flow passages bounded by the sides of a sheet-like insert, the two blade walls and fins between the insert and the blade walls, the flow passages commencing at one end of the blade and extending in a spiral-like path around and along the insert.

In a preferred form, the invention is applied to rotor blades which are fed from the root end.

The invention will now be described with reference to the accompanying drawing, in which:

FIG. 1 shows a sectional elevation of a gas turbine rotor blade according to the invention, the section being taken on the line B--B in FIG. 2;

FIG. 2 shows a section on the line A--A in FIG. 1, to a scale 10 times that of FIG. 1; and

FIG. 3 shows an isometric view of the shroud end of the rotor blade, seen looking from the root towards the shroud.

The rotor blade in FIG. 1 has leading and trailing edges 10, 11, a shroud end 12 and a root end 13. The blade is hollow, and the space within it is effectively divided into two by means of a sheet-metal insert 14 which extends substantially the full radial length of the blade being brazed to the blade at its root end but otherwise unattached to allow for differential expansion. The arrangement of the insert 14 within the blade is clearly seen in FIG. 2.

It will be seen that the insert is located between a large number of pimples 15 (indicated in FIG. 1 by small crosses) and by a series of helical fins 16. The blade is conveniently made with the pimples and fins cast onto the interior surfaces of the blade walls 17, 18. The insert 14 stops short of both the leading and trailing edges of the blade, thus leaving spaces around which air may pass in order to progress from one side of the insert to the other.

Referring now again to FIG. 1, it will be seen that air supplied to the interior of the blade from the root end 13 can enter any one of a series of flow passages extending obliquely up one side of the insert passing round the leading or trailing edge of the insert, and then continuing obliquely up the other side of the insert. An arrow traces one possible path. As it progresses radially outwards, a proportion of the air is allowed to escape through leading edge film cooling holes 20, and through trailing edge slots 21. Since the volume of air flowing through the blade is thus diminished, the flow passages are designed to be of smaller cross section towards the outer shroud end 12 of the blade. This can be achieved by arranging that the spacing of the fins 16 is reduced or, more conveniently, by reducing the width of the passages. This maintains the airflow velocity substantially constant. In addition, the velocity of the air flow may be varied by altering the angle at which the fins 16 are cast onto the interior surfaces of the blade.

In a preferred form of the invention, holes 22 (FIG. 3) may be provided for the final escape of the cooling air in the angle formed by the blade proper wall 17 and the shroud 23. The air thus released can be used to cool the shroud by causing it to spread over the shroud 23 along channels 24 formed in the radially inner surface thereof.

It will be seen that a blade constructed in the fashion described is relatively easy to produce, particularly since the insert is solid and therefore easy both to manufacture and to insert into the blade, while the blade itself can be conveniently cast, together with, fins and pimples, using only a single piece core.

If desired, in the described arrangement the holes 20 and/or the holes 21 and/or the pimples 15 may be omitted, the cooling medium may be liquid or a gas other than air, and the fins 16 and pimples (if provided) may be other than integral with the blade walls.

In a further variation of the described arrangement at least some of the flow passages for cooling air are such that they individually serve either the leading edge of the blade or the trailing edge of the blade, but not both. This may be effected by suitable choice of the inclination of the fins 16. Such an arrangement may enable different supplies to be used for the leading and trailing edges of the blade to make allowance for the different ambient air pressures existing in those regions.

Claims

What is claimed is:

1. A gas turbine blade having opposed walls defining therebetween a hollow interior space, an insert within said space, said insert being formed of a solid sheet curved to the chamber of the blade, and fins carried by said blade and extending between said insert and said blade walls, said walls, said insert and said fins defining in combination a plurality of flow passages for cooling fluid, each said flow passage commencing at one end of the blade and extending in a spiral-like manner around and along the insert.

2. A blade as claimed in claim 1, which includes a plurality of discrete pimples extending between the sides of the insert and the blade walls within the flow passages for providing location for the insert.

3. A blade as claimed in claim 2, wherein the fins and pimples are formed integrally with the blade walls.

4. A blade as claimed in claim 1, wherein holes are formed in the region of the leading edge of the blade for allowing cooling fluid to pass to the exterior of the blade from the flow passages.

5. A blade as claimed in claim 1, wherein holes are formed in the region of the trailing edge of the blade for allowing cooling fluid to pass to the exterior of the blade from the flow passages.

6. A blade as claimed in claim 1, wherein the insert has a root end portion at which it is secured within the blade by brazing, the insert being otherwise unattached to allow for differential expansion.

7. A blade as claimed in claim 1, wherein at least some of the flow passages are arranged for individually serving one edge only of the blade.

8. A gas turbine rotor having a plurality of blades as claimed in claim 1, arranged for supply with cooling fluid at their root ends.

9. A gas turbine rotor according to claim 8, which includes a shroud connecting together the outer ends of the blades, the arrangement being such that cooling fluid may pass from said flow passages into cooling relation with the shroud.

10. A rotor according to claim 9, wherein the radially inner surface of the shroud is formed with channels, and the blade walls are formed with holes arranged for directing cooling fluid from the flow passages along the channels.

11. A blade as claimed in claim 6, wherein said fins are terminated immediately adjacent said root end portion of said insert.

12. A gas turbine blade having opposed walls defining therebetween a hollow interior space, and an insert within said space, said insert being formed of a solid sheet curved to the chamber of the blade and connected to said walls by brazing at the root end of the blade, being otherwise unattached to allow for differential expansion, said walls being integrally formed with fins extending between said insert and said blade walls, said walls, said insert and said fins defining in combination a plurality of flow passages for cooling fluid to flow through the blade commencing at the root end of the blade and passing in a spiral-like manner around and along the insert.