US2873087A - Means for cooling gas turbines - Google Patents

Description

Feb. 10, I959 a. J. TERRELL ETAL MEANS FOR 000mm; GAs TURBINES 2 Sheets-Sheet 1 Filed J l 1a, 1953 Feb. 10, 1959 B. J. TERRELL EIAL 2,873,087

MEANS FOR COOLING GAS TURBINES Filed July 16, 1953 2 Sheets-Sheet 2 lzzvezafiam jJTennelL United States Patent MEANS non COOLING GAS TURBINES Basil Joseph Terrell and Frederick John Bayley, Monkseaton, England, assignors to The Parsons and Marine Engineering Turbine Research and Development Association, Wallsend, England Application July 16, 1953, Serial No. 368,402

7 Claims. (Cl. 253-39.15)

but ifcirculated from an outside source through the narrow and thin walled passages which are inevitable in typical internally, cooled turbine blades, the corrosion and fouling associated with its use is a serious difiiculty. One of the advantages secured by the present invention is that it enables water to be circulated through a bladed turbine rotor disc or drum in such a way as to protect the blade root and more highly stressed parts of the rotor from the effect of the hot gases, and to efiectively cool the blades without traversing the latter internally. Other advantages are that the invention does not rely on the normal blade-to-disc attachment for sealing the water in the rotor, and it provides a construction giving the necessary flexibility to the blading while also adding to its strength.

. The invention consists in a gas turbine bladed rotor having features as set forth in the claims appended hereto.

In the preferred construction, the rotor disc or drum is circumferentially channelled in way of the blade row or each blade row, the blades being attached to the disc or drum by a blade root at the bottom of the channel, and a cap or collar is inserted over the blades and attached to said disc or drum and to said blades so as to form conjointly with the channel a closed annular space, the space being in communication with passages in the rotor whereby coolant is circulated through the channel around the blades and roots. Grooves or indentations may be provided in the cap or collar, disposed between the blades, for the purpose of providing a degree of tangential flexibility in the blade row or rows to take up uneven thermal expansions, and for providing additional strength to resist the pressure of the liquid coolant Within the channel. Preferably also, baffles are provided in the channel to direct the flow of coolant around the blades in a controlled manner, for example the coolant may be made to traverse each blade twice, i. e. on opposite sides, the passages between the blades having roughly the same shape as the gas passages outside the drum or disc periphery. An advantage of this construction is that the turbulence stimulated by changes in flow direction increases the rate of the heat transfer to the coolant.

The coolant may flow from a collector ring on the rotor shaft, axially along a shaft bore to a point roughly corresponding to the cooled blade row centre-line; then along a radial passage to the blade roots, through suitable channels in one or more of these as convenient into the beforementioned annular channel surrounding the blades. The coolant may then flow in the circumferential direction around a suitable proportion of the turbine disc or drum periphery to a second radial return pas sage into the shaft bore and so to a return collector ring on the shaft. It is convenient to divide the annular channel into four equal sections, so that the water may flow outwards along two diametrically opposite radial channels and return to the shaft in directions normal to its outward path, but this arrangement may be varied as required.

In order that the invention may be more fully understood it will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a radial section of the outer part of a turbine disc, with blades each having an inverted T-root, and shows the cooling arrangements;

Figure 2 is a transverse section taken on the plane II, II of Figure 1;

Figure 3 is a view looking in the direction of the arrow III of Figure 1, showing the cap or collar removed and the blades in section;

Figure 4 is a longitudinal section on one side of the axis of a four-stage turbine, showing the drum with blading having a serrated root, and cooling arrangments therefor;

Figure'S is a broken view of two adjacent blades forming part of a blade row, and shows a method of at-- taching the cap or collar;

Figure 6 is a broken view of one blade corresponding to Figure 5, and showing an alternative method of attaching the cap or collar;

Figure 7 is a view in the direction of the arrow VII of Figuire 5 showing an identation in the cap or collar. Like parts in the dilferent figures are designated where practicable by like reference numerals.

Referring to Figure 1 a turbine disc 1 is channelled inwards from the outper periphery so as to form an annular channel 1. The disc 1 is bladed with blades such as 2having an inverted T-root 2 seated on the bottom or inner periphery 1A of the channel 1 which surrounds a part 2 of the blade 2 additional to its efiective length or span. A cap or collar 3 is inserted over the blades and is welded thereto and to the outer periphery of the disc thereby sealing the channel 1 Referring to Figures 2 and 3, a path for liquid coolant into the annular channel 1 is formed by a radial passage l and two radial passages 2 in the disc 1, and in two adjacent blade roots 2" respectively. Arrowheads are inserted in the Figures 1, 2 and 3 to show the directions of flow of the coolant. It will be seen that coolant from the passage 1* in the disc 1 divides into two streams which flow through the passages 2 in the two adjacent blade roots, into the channel 1., wherein the flow is maintained in two separate streams which are constrained to flow circumferentially in the opposite directions by means of battles 4, shown in Figure 3, fitted on each side of a blade, as shown, so as to bridge the channel 1. Other bafies such as 5 in Figure 3 are arranged to bridge the annular passage 1 on one side only so that the coolant is made to traverse the blade twice, i. e. on opposite sides, with the advantage previously referred to. The blades in this example are hollow, having cavities 2 wherein a heat transfer medium, for example water, is enclosed.

Referring now to Figure 4, a four-stage turbine drum 6 is channelled inwards from its outer periphery so as to form four annular channels 6 corresponding to the blade rows. The drum is bladed with blades 7, 8, 9 and 10 in their respective rows, and having a serrated root in grooves 6 at the bottom of the annular channels 6. Cap or collars 11, 12, 13 and 14 are inserted one over each blade row and are welded to the blades and to the outer periphery of the drum thereby sealing the channels 6. Radial passages 6 are drilled in the drum to carry coolant between a longitudinal bore 6 of the drum and the blade roots, corresponding radial passages 7 8 9 and 10 being arranged in the blade roots to carry the coolant to and from the channels 6 in a manner along the lines described in connection with Fig. l. The channels 6*"- may be fitted with bafiles arranged similarly to tho e described with reference to Figures 1, 2 and 3 in order to direct the coolant around the blades to the best advantage. The blades in this example also are hollow, and their cavities 15 each contain a quantity of heat transfer medium.

Figure 5 shows two adjacent blades 15 and 16 0f a blade row with their corresponding caps or collars 17 and 18 for the purpose of sealing the annular channel in the disc or drum (not shown) to which they are to be fitted. Between the two blades and formed in the cap 17 is a groove or indentation 1'7 which takes the shape of a crescent when seen in the view of Figure 7; similar indentations are arranged in the collars between the remaining blades of the blade row with the object of providing tangential flexibility, and also to give additional strength to resist the pressure of the liquid coolant within the channel. Figure 6 shows the attachment of an alternative form of collar 19, having an inwardly turned flange w to a blade 2%.

We claim:

1. A gas turbine rotor comprising bla es constituting a blade row and said blades havingsolid inner end portions and spaced wall portions of relatively thin crosssectional area extending radially outwardly therefrom, and means constituting an enclosed ch nnel in the rotor periphery, the solid inner end portions being located radially inward of the channel with the wall portions of thin cross-sectional area extending through the channel and terminating outwardly of the channel, the parts of the wall portions of relatively thin cross-sectional area lying within the channel being spaced from the sides of the channel to afford surfaces for the transference of heat from said wall portions to coolantcirculfi fidithrough the said channel,

2. A gas turbine rotor according to claim 1, in which said wall portions constitute a cavitied blade.

3. A gas turbine rotor according to claim 1, in which the blades comprise interior cavities enclosed by said wall portions containing heat transfer medium which is liquid at least at the operational temperature of the turbine.

4. A gas turbine rotor according to claim 1, in which the said enclosed channel extends circurnferentially in the direction of the blade row, and comprising means for attachment of the blades at the bottom of said channel, and a cap adapted to beinserted over the blades and being attached to the latter and to the rotor to constitute the top of the enclosed channel.

5. A gas turbine rotor according to claim 1, comprising means for attaching the blades at the bottom of channel, a cap adapted to be inserted over the blades and attached to the latter and to the rotor to consL tute the top of the said enclosed channel, and grooves in said cap disposed between the blades to afiord tangentialfiezibihty to the bladerow.

6. A gas turbine rotor according .10 cla m 1 Qomprising baffles in the said enclosed channel to direct allow of coolant around the blades in ontrolle manne 7. A gas turbine rotor according to claim '1, comprising eans for subdividing the raid enclosed channel into a number of arcnate portions, each portion having separate coolant inlet and outlet p ssages wmmnn cation respe ely wits coo r- "early and-return .m th cat91- c t Reterenees Cited in thefile of this patent ST TBS PATENTS 1,378,464- Junggren May 17, 1921 2,256,479 Holzworth Sept. 23, 1941 2,5655% Constant Aug. 23, 1951 2,603,453 Sollinger July 15, 1952 FOREHGN PATENTS 569,806 Germany Feb. 8, 1933 824,013 '.'!".".l!".'."'.'-!('9\'1!!! Qi Z i -3

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