US3051438A

US3051438A - Axial-flow blading with internal fluid passages

Info

Publication number: US3051438A
Application number: US714848A
Authority: US
Inventors: Roberts Derek Aubrey; Page Edward
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1957-02-22
Filing date: 1958-02-12
Publication date: 1962-08-28
Anticipated expiration: 1979-08-28
Also published as: GB855058A; FR1191540A; DE1403089A1

Description

Aug. 28, 1962 D. A. ROBERTS ETAL 3,051,438

AXIAL-FLOW BLADING WITH INTERNAL FLUID PASSAGES Filed Feb. 12, 1958 a 33 zatamw hi 3 2% f I? if 1%1 19 6 37%5 1% F .Z. 3 w

United States Patent Oflice 3,051,438 Patented Aug. 28, 1962 3,051,438 AXIAL-FLOW BLADHNG WITH ENTERNAL FLUID PASSAGES Derek Aubrey Roberts, Breadsall, and Edward Page, Chellaston, Englam;i assikgnors to Rolls-Royce Limited, Derb En land a ritis company ra a Feb. 12, 1958, Ser. No. 114,348 Claims priority, application Great Britain Feb. 22, 1957 7 Claims. (Cl. 25339.15)

This invention comprises improvements in or relating to bladed rotor or stator constructions for axial-flow fluid machines, such for example as compressors or turbines of gas turbine engines, and is concerned more specifiically with such constructions in which a fluid is caused to flow through passages in the blades for heating or cooling purposes.

According to the present invention, a blade for use in bladed constructions as above specified comprises internal bores extending lengthwise of the blade and interconnected at their ends to afford a sinuous flow path having an odd number of courses through which fluid flows in succession, there being an inlet to the one end of the path at one end of the blade and an outlet from the other end of the path at the opposite end of the blade. Each course may be afforded by a single bore or by a plurality of bores in parallel. Also, a blade may be provided with a plurality of such sinuous flow paths, the paths having the same or different odd number of courses and the paths being either completely separate or having one or more courses in common.

By adopting the invention, the bores may be made by acceptable manufacturing methods giving bores of cornparatively large cross-sectional area while also obtaining a high ratio of the internal surface area to the total cross-sectional flow area of a path so obtaining a good cooling efiiciency.

The inlet and the outlet of a sinuous flow path may have each a flow area not less than and preferably substantially equal to the total cross-sectional flow area of the path, and there may be provided a bleed hole of smaller flow area from the first course of the path at said opposite end of the blade, so that a proportion of the fluid flows through a single course of the sinuous flow path and the remainder flows through the whole path. The bleed hole preferably has a flow area which is considerably smaller than that of the inlet and outlet so that only aminor proportion of the fluid flows through a single course of the path. The provision of such a bleed hole assists to prevent blocking of the flow path at the interconnection between the first and second courses by dirt or other matter entrained in the fluid. Furthermore, there may be provided a small area fluid inlet hole to a course or courses other than the first course, for instance to the last course of the path so as to augment the flow in this course, and, by selecting the areas of the inlet hole and the bleed hole in relation to the areas of the inlet and outlet, the cooling or heating effect obtained and the cooling or heating efliciency may be adjusted having regard to the pressure difference in the fluid between the inlet and outlet.

One embodiment of this invention as applied to the cooling of turbine rotor blades will now be described with reference to the accompanying drawings in which:

FIGURE 1 is an axial section through part of a gas turbine, parts being broken away to show details of construction, and

FIGURE 2 is a view in the direction of arrow 2 on FIGURE 1.

The turbine illustrated comprises a casing 10 wherein the turbine rotor 11 is rotatively mounted, a ring of nozzle guide vanes 12 extending from the casing 10 to inner stator structure 13 and guiding the hot working gas to rotor blades 14 mounted at the periphery of the rotor 11, and an exhaust assembly which comprises a bullet 15 which defines with the downstream portion of the casing 10 an annular exhaust passage for gases leaving the turbine.

The blades 14 are shown as being mounted in the rotor by means of roots each of which has a shoulder attachment portion 16 engaging a correspondingly shouldered channel in the rotor discs, a platform portion 17 from which the blade extends and which together with the other platform portions forms an annular portion of the inner wall of the working gas passage of the turbine, and a stem 18 interconnecting the attachment portion '16 and the platform portion 17.

The stems 18 are circumferentially narrower than the platforms 17 so that tunnels 19 are formed between the stems. The blades are retained against disengagement from the channels by tangs 20 on the attachment portions 16, which tangs bear on one axial face of the rotor, and by plate means 21 which is retained against the opposite face of the rotor and engages by its outer edge in inwardly-facing channels 17a in the platform 17. The plate means 21 may be annular and split along one radius so as to be contractible and may be held in place on the rotor by having a flange 21a at its inner edge to occupy an inwardly facing groove 11a on the rotor. The plate means 21 is in contact with the downstream surfaces of the blade roots and of the rotor disc "11 and thus serves to blank off the downstream ends of the tunnels 19.

The blades 14 are also provided with integral tip shrouds 22 which run in a circumferential groove 23 in the casing 10 and which are formed with radially projecting ribs 24 co-operating with the walls of the groove 23 to form gas seals to prevent excessive flow of working gas around the tips of the blades.

The blades 14 are also arranged to be cooled by passing through them a cooling fluid, for example compressed air tapped from the compressor of the gas turbine. The air prior to being fed to the blades may be cooled, say by evaporation therein of a liquid, such as Water, sprayed therein.

Each blade 14 has within it bores forming a sinuous flow path comprising three

courses

25, 26, 27 which extend through the length of the blade and are connected in flow series. The first course 25' is in the form of a drilling adjacent the mid-chord of the blade section and has an inlet 30 thereto from a tunnel 19. The second course 26 is also a drilling at a position between the course 25 and the leading edge of the blade and is connected to the first course 25 at the tip of the blade by means of a cross-passage 28. The outer ends of the

courses

25, 26 are closed by a plate 31 let into the tip shroud 22 of the blade. The course 27 is a further drilling, is adjacent the leading edge of the blade, and is connected at the root end of the blade to course 26 by a cross drilling 25 which is closed by a plug 32. The course 27 has an outlet 33 through the tip shroud 22 into the groove 23.

It will be seen that, in this instance, the areas of the inlet 30 and outlet 33 are substantially equal to the flow crosssection of the sinuous path afforded by the three

courses

25, 26, 27, and further that the path has a high ratio of surface area to flow cross-sectional area giving a good cooling efficiency.

The compressed air for cooling is fed through a conduit 34 to the space 35 between the rotor 11 and the stator structure 13, and then flows partly into the working gas passage at 35 to prevent inward flow of the hot gas, and partly into the tunnels 19 and through the blades 14. The air enters each blade through inlet 30 and then flows through

courses

25, 26, 27 in succession leaving the blade via outlet 33 into the groove 23 whence it passes into the working gas passage.

In the construction shown, there is also provided a bleed hole 37 in the plate 31 at the end of the first course 25. The bleed hole 37 has an area which is considerably smaller than that of the inlet 30 and it permits a small proportion of the air flowing in course 25 to pass directly into the groove 23. This arrangement prevents blocking of the cross-passage 28 by deposition of dirt or other matter, such as products of a cooling liquid spray, entrained in the compressed air.

Also in the construction shown, there is provided an auxiliary inlet hole 38 leading from the tunnel 19 directly to the inlet end of the last course 27 of the flow path. The hole 38 has an area which is considerably smaller than the outlet 33 and it permits a small proportion of the compressed air to flow directly from tunnel 19 into the final course 27 of the sinuous flow path.

By selecting the sizes of the holes 37, 38 in relation to the flow cross-sectional area of the sinuous path, the proportion of air which flows in a single course, to the proportion which flows through the :full length of the sinuous flow path, may be varied, so varying the cooling efiiciency and the cooling effect obtained for a given pressure difference as between tunnel 19 and groove 23.

We claim:

1. A blade for use in a turbo-machine, which blade has an aerofoil section, a leading edge and a trailing edge and has a plurality of bores extending lengthwise within it, the said bores being interconnected at their ends to afford a sinuous flow path having an odd number of courses through which fluid flows in succession, a first of said bores being adjacent the said leading edge and a second of said bores being adjacent the said trailing edge, a fluid inlet to the path opening into said second of the said bores at its end adjacent one end of the blade and a fluid outlet opening from the path leading from the first of said bores at its end adjacent the opposite end of the blade.

2. A blade according to claim 1, wherein each course comprises a single lengthwise bore.

3. A bladed rotor for a gas-turbine Comprising a rotor disc, a ring of aerofoil section blades, each blade having a leading edge and a trailing edge, each blade having at one end a root including a shouldered attachment portion engaging a correspondingly shouldered channel in the rotor disc, each of the blades further having an odd number of bores extending lengthwise therein from the root to adjacent its opposite end, a first of said bores being adjacent the said leading edge, a second of said bores being adjacent the said trailing edge and a third of said bores being between said first and second of said bores, the bores being interconnected adjacent the ends of the blade to form a sinuous flow path having an odd number of courses through which fluid flows in succession, a fluid inlet opening to said path opening into the end of said second of the bores adjacent the said root and a fluid outlet opening from the path leading from the end of said first of the bores adjacent the opposite end of the blade, and means connected to deliver fluid to the inlet openings of the flow paths in the blades, the fluid leaving the blades through the outlet openings adjacent the opposite ends of the blades.

4. A blade :for use in a turbo-machine, which blade has an aerofoil section, a leading edge and a trailing edge and has a plurality of bores extending lengthwise within it, the said bores being interconnected at their ends to afford a sinuous flow path having an odd number of courses through which fluid flows in succession, a first of said bores being adjacent the said leading edge and a second of said bores being adjacent the said trailing edge, a fluid inlet to the path opening into said second of the said bores at its end adjacent one end of the blade and a fluid outlet opening from the path leading from the first of said bores at its end adjacent the opposite end of the blade, each course comprising a single lengthwise bore, the inlet and the outlet opening of the sinuous flow path each having a flow area substantially equal to the cross-sectional area of the bores, said first course of the path having a bleed hole of smaller flow area at said opposite end of the blade, so that a proportion of the fluid flows through a single course of the sinuous flow path and the remainder flows through the whole path.

5. A blade according to claim 4, wherein the bleed hole has a flow area which is considerably smaller than that of the inlet and outlet so that a minor proportion of the fluid flows through only a single course of the path.

6. A blade according to claim 4, comprising also a small area fluid inlet hole to one of said courses other than the first course.

7. A blade according to claim 4, comprising also a small area fluid inlet hole to the last course of the sinuous flow path.

References Cited in the file of this patent UNITED STATES PATENTS 2,364,189 Buchi Dec. 5, 1944 2,603,453 Sollinger July 15, 1952 2,699,598 Daugherty Jan. 18, 1955 2,778,601 Eckert M Jan. 22, 1957 2,883,151 Dolida Apr. 21, 1959' 2,920,865 Lombard Jan. 12, 1960 2,945,671 Petrie July 19, 1960 FOREIGN PATENTS 292,537 Switzerland Nov. 2, 1953 1,130,996 France Oct. 8, 1956