US3658439A

US3658439A - Metering of liquid coolant in open-circuit liquid-cooled gas turbines

Info

Publication number: US3658439A
Application number: US93056A
Authority: US
Inventors: Paul H Kydd
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1970-11-27
Filing date: 1970-11-27
Publication date: 1972-04-25
Anticipated expiration: 1989-04-25
Also published as: DE2158242C3; DE2158242B2; NL7116204A; NL169770C; IT941373B; NO134226C; NO134226B; FR2115419A1; JPS5514241B1; GB1327317A; FR2115419B1; NL169770B; DE2158242A1

Abstract

Weir construction precisely located relative to the shaft axis of a liquid-cooled gas turbine is employed to meter coolant flow to the cooling channels in turbine buckets.

Description

United States Patent Kydd METERING OF LIQUID COOLANT IN OPEN-CIRCUIT LIQUID-COOLED GAS UNITED STATES PATENTS TURBINES- 3,446,482 5/ I969 Kydd ..416 /90 [72] Inventor: Paul H. Kydd, Scotia, NY. 2,991,973 7/196! Cole et al ..4l6/97 [73] Assign: General Electric Campany Primary Examiner-Everette A. Powell, Jr. 7 [22] Filed: Nov. 27, 1970 Assistant Examiner-Clemens Schimikowski Attorney-Richard R. Brainard, Paul A. Frank, Charles T. [2]] Appl' 934,56 Watts, Leo l. Malossi, Frank L. Neuhauser, Oscar B. Waddell and Joseph B, Forman [52] [1.5. CI ..416/97, 416/92, 416/95 [51] Int. Cl ..F0ld 5/18 [57] ABSTRACT [58] Field of Search 51 11 Weir construction precisely located relative to the shaft axis of a liquid-cooled gas turbine is employed to meter coolant flow to the cooling channels in turbine buckets.

4 Claims, 4 Drawing Figures a a i l /3 I w, /5 l 4 26 Z6 a Lu, 1

r J I '7 3/ Z8\29 z: 4 24;? j u A 24 References Cited PATENTEDAPR 25 1912 SHEET 10F 2 Z M mu /Mm my 8 V JA @Z 5 ma \..\\&

PATENTEDAPR 25 I972 SHEET 2 BF 2 Paul MK 12') van 602- ydci is Attorney METERING F LIQUID COOLANT IN OPEN-CIRCUIT LIQUID-COOLED GAS TURBINES BACKGROUND OF THE INVENTION Structural arrangements for the liquid cooling of gas turbine buckets are shown in U.S. Pat. Nos. 3,446,481 Kydd. These patents are incorporated by reference.

The provisions for open-circuit liquid cooling disclosed therein are particularly important for the capability offered thereby for increasing the turbine inlet temperature to an operating range of from 2,500 F. to at least 3,500 F. thereby obtaining an increase in power output ranging from aboutlOO to 200 percent and in an increase in thermal efficiency ranging to as high as 50 percent. Such open-circuit liquid-cooled turbine structures are referred to as ultra high temperature gas turbines.

In such turbines the heat flux to the turbine buckets is so high that it is necessary to have a great many coolant channels in each bucket to distribute the coolant uniformly over the bucket surface. Typically, for a small turbine, the channels will measure about 0.02 X 0.025 inch and be spaced from about 0.052 to 0.071 inch on center over different surface areas of the bucket for a total of about 50 coolant channels per bucket. In a complete turbine rotor there may be as many as 100 presenting a total of about 5,000 channels each of which must receive an accurately metered amount of liquid coolant. Also, in ultra high temperature gas turbines it is desirable to employ extremely high bucket tip speeds (e.g. l ,5 00-2,000 feet/second) in order to remove large amounts of energy per turbine stage. These high speeds further complicate the problem of coolant metering. Since the centrifugal field may be as much as 250,000 G under such conditions a difference in water level of as little as 0.001 inch is equivalent to a 20 foot head at l G. Thus, even minor inaccuracies in that portion of a metering system (e.g. locations of metering holes or weirs) served by a single source of coolant will result in large imbalances in flow in that particular portion due to differences in pressure head.

SUMMARY OF THE INVENTION Weir construction forming part of each platform element of the turbine rotor is precisely located relative to the shaft axis of the liquid-cooled gas turbine providing essentially constant flow conditions at all points along all weirs.

BRIEF DESCRIPTION OF THE DRAWING The exact nature of this invention as well as objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings in which:

FIG. 1 is a three-dimensional view partially in cut-away section displaying the relationship of the weir construction as part of individual platform elements relative to the lower ends of the coolant channels of the adjacent turbine bucket;

FIG. 2 shows the unified bucket/rotor disk rim construction in combination with improved bucket tip construction for the open-circuit system for cooling this structure and shows portions of the casing related to the bucket tip construction;

FIG. 3 is a section taken on line 3-3 of FIG. 2 and FIG. 4 is an offset section taken on line 4-4 of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turbine bucket consists of a sheet metal skin 11 affixed (e.g. by brazing) to investment cast hollow core 12 having inwith and terminate at a similar manifold (not shown) recessed into core 12. Near the trailing edge of bucket 10 a cross-over conduit (not shown) connects the manifold on the suction side with manifold 14.

Requisite open-circuit cooling from manifold 14 (and the manifold on the suction side) is ensured by the presence of opening 16, which provides for the exit of the heated cooling fluids from manifold 14 at the trailing edge of bucket 10 as shown. Annular collection slot 17 formed in casing 18 receives the centrifugally directed ejected fluid for the eventual recirculation or disposed thereof.

The turbine bucket manifolding and collection system is described in greater detail and is claimed in U.S. Patent application Ser. No. 93,057 (Docket RD-3206) Kydd (incorporated by reference) filed Nov. 27, 1970, now pending, and assigned to the assigned of the instant invention.

The root end of core 11 consists of a number of finger-like projections, or tines, 19 of varying length. These projections 19 may present a generally rectangular profile as shown or each tine may be tapered toward the distal end thereof to present a generally triangular profile. Rim 21 of turbine disk 22 has grooves 23 machined therein extending to various depths and having widths matching the different lengths and widths of bucket tines 19 such that tines 19 will fit snuggly into the completed grooves 23 in an interlocking relationship. Triangularly shaped bucket tine profiles provide for improved stress distribution in the joints between tines I9 and grooves 23 in shear and in the tines in tension. However, the rectangular profiles are preferred for ease of manufacture.

Once the proper fit has been obtained, the appropriate amount of brazing alloy is placed in each groove 23 and the buckets are inserted and held in fixed position by a fixture. The fixture is biased to maintain a tight fit between tines I9 and grooves 23 regardless of thermal expansion. Conventional brazing alloys having melting points ranging from 700 to l,lO0 C. may be used. Single metals, such as copper, may also be used.

This interlocking bucket/rotor disk construction is more completely described and claimed in US. Patent application Ser. No, 93,058 (Docket RD-3207) Kydd (incorporated by reference), filled Nov. 27, 1970, now pending and assigned to the assignee of the instant invention.

Thereafter, the assembly (the rim with all the buckets properly located) is furnace-brazed to provide an integral structure.

Steel alloys may be used for the skin and core, preferably those containing at least 12 percent'by weight of chromium for corrosion resistance and heat treatable to achieve high strength.

The cutting of grooves 23 into rim 2] not only provides the requisite configuration for fastening the bucket root and lessens the weight of the rim, but in addition the ribs 24 between grooves 23 provide area on the upper surfaces thereof for attachment thereto of investment cast platform elements 26 having cooling channels 27 and 28 formed therein. Platform elements 26 may also be prepared by other methods, such as, by coining. The cooling channels 27 are in juxtaposition with grooves 23 and cooling channels 28 interconnect the cooling channels 27 as shown. The separating walls 29 between cooling channels 27 are dimensioned to coincide with the width of juxtaposed ribs 24.

The improved structure for metering of the liquid coolant is provided during the preparation of platform elements 26 by accurately grinding each edge rib 31 to the radius of the outer diameter of the ribs 24 thereby providing a cylindrical surface (the elements of which extend in the axial direction) following bucket 10 on each side thereof adjacent the cooling channels 13. As will be explained hereinbelow all portions of those cylindrical surfaces receiving coolant from a common distribution path must be accurately located equidistant from the axis of rotation. In operation these edge ribs 31 will function a weirs over which the cooling fluid can distribute uniformly into the bucket cooling channels 13 of each bucket uniform sheet. Ribs 24 are each provided with relief cuts 24a to ensure a clear supply path for the coolant along the length of ribs 31 to grooves 13a leading to channels 13.

Platform elements 26 are affixed to the rotor rim by the electron beam welding of separating walls 29 to ribs 24 after previously grinding the distal face of each wall 29 to a radius common to the outer diameter of ribs 24.

Although the platform construction shown herein consists of individual platform elements prepared separate from buckets 10 and from each other, other constructions are equally feasible. For example, the platform components may be made integral with each bucket or a single continuous platform having holes cut therein to accommodate buckets 10 may be used. In each case the weir surfaces distributing coolant to buckets 10 will be formed as part of the platform construction located adjacent each side of each bucket 10.

Since the leading edge of buckets 10 is exposed to the highest heat flux, it is more directly (not via weir 31) supplied with liquid coolant. The manner in which this liquid coolant is supplied is more completely described hereihbelow.

As is described in the aforementioned Kydd patents, cooling liquid (usually water) is sprayed at low pressure in a generally radially outward direction from nozzles (now shown, but preferably located on each side of disk 22) and impinges on disk 22. The coolant thereupon moves into gutters 32, 32a defined in part by downwardly extending lip portions 33, 33a. The cooling liquid accumulates in gutters 32, 32a (cooling the rim portions with which it comes into contact) being retained therein until this liquid has accelerated to the prevailing disk rim velocity.

After the cooling liquid in gutters 32, 32a has been so accelerated, this liquid continually drains from gutters 32, 32a passing radially outward through

holes

34, 34a of which holes 34 are in flow communication with the two outside grooves 23 (FIGS. 2 and 4) in the regions between buckets 10. As is shown in FIG. 4 specific holes 34a communicate directly with the cooling channel located at the leading edge of each of the buckets 10. Thus, some of the liquid coolant by-passes weirs 31 to be provided directly to the leading edges of buckets 10 while the remainder of the coolant is introduced into the outside grooves 23 from which it is distributed via cooling channels 28 to the cooling channels 27. As the coolant traverses all these surfaces of the platform elements 26, these elements are kept cool. Thereafter, the coolant passes over the distal faces of edge ribs 31 in thin sheets into the radially inner end of cooling channels 13 (via grooves 13a) in adjacent buckets l and thence into and through the turbine buckets.

lt is critical that the portions of gutters 32, 32a draining into

holes

34, 34a be machined to very close tolerances to ensure equidistance thereof from the center of rotation whereby coolant distribution to

holes

34, 34a will be substantially equal. As may be seen in FIG. 4 a set of six holes 34 provides the coolant for the coolant channels in the suction side of one bucket and in the adjacent pressure side of the next bucket. Thus, the pair of edge ribs 31 receiving coolant from such a common source of holes 34 (regardless of whether they are formed in the same platform element as shown herein, or not) must present weir surfaces all points along which are equidistant from the center of rotation to ensure equal distribution of coolant.

As the cooling liquid moves through cooling channels 13 of any given bucket a large portion) or substantially all of the cooling fluid, depending upon the rate of flow) is converted to the gaseous or vapor state as it absorbs heat from the skin ll and core 12 of the bucket. At the outer ends of cooling chan nels 13 the vapor or gas and any remaining liquid coolant pass into manifold 14 and the manifold on the suction face. Thereafter, the flow from the suction manifold is merged with the flow in manifold 14 and the combined flows exit therefrom via opening 16 into collection slot 17 to complete the opencircuit cooling path.

In the construction illustrated and described the weirs (accurately located cylindrical surfaces), one of which is located in the given li uid coolant distribution Kath leadin to each side of each tur me bucket 15 ground to t e radius 0 the outer diameter of ribs 24. However, a radius different from the.

radius of the outer diameter of ribs 24 may be employed, if desired, so long as all portions of those cylindrical surfaces receiving coolant from a common upstream distribution path are located equidistant from the axis of rotation.

If weirs are used, which extend straight across the underside of the platform construction, each cooling channel must extend to a location adjacent the straight weir, so that the liquid coolant traversing the accurated ground cylindrical surface of the weir (located in accordance with this invention) will be fed directly to the coolant channels or extensions thereof.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a gas turbine wherein a turbine disk is mounted on a shaft rotatably supported in a casing, said turbine disk extending substantially perpendicular to the axis of said shaft and having turbine buckets and platform means affixed to the outer rim thereof, said buckets receiving a driving force from a hot motive fluid moving in a direction generally parallel to said axis of said shaft and the driving force being transmitted to said shaft via said turbine disk, means located radially inward of said platform adjacent said turbine disk for introducing liquid coolant within said turbine in a radially outward direction into open-circuit distribution paths by which said coolant traverses surface area of said rim and said platform means, passes into cooling channels in said buckets and exits from said channels in a radially outward direction, the improvement comprising:

a. a plurality of separate cylindrical surfaces, the elements of which extend parallel to the axis of the shaft, each of said surfaces being formed on the radially inward side of the platform means, one of said cylindrical surfaces being located in the given liquid coolant distribution path leading to each side of each turbine bucket adjacent the inward end of the cooling channels therefor and all portions of those cylindrical surfaces receiving coolant from a common downstream distribution path being located equidistant from said axis.

2. The improvement of claim 1 wherein a pair of exposed cylindrical surfaces are formed on a single platform element disposed between a pair of turbine buckets.

3. The improvement of claim 2 wherein the cylindrical surfaces follow the turbine bucket root air-foil configuration.

4. The improvement of claim 1 wherein the platform means has a plurality of grooves in the underside thereof to facilitate the distribution of liquid coolant.

I UNITED STATES PATENT OFFICE CERTIFICATE OF (IQ-ERECTION v 3,658,439 Dated April 25, 1972 Patent No.

Inventor(s) Paul H. Kydd v It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected" as shown below:

In column 1, the sentence in lines 5 and 6 should read:

- Structural arrangements for the liquid cooling of gas turbine buckets are shown in U. S. Patent Nos.

3,446,481- Kydd and 3,446,482 Kydda Signed and sealed this 29th day of August 1972'.

(SEAL) Attesti ROBERT GO-TTSCHALK EDWARD M.FLETCHER,JR. V

Commissioner of Patents Attesting Officer 1'' FORM 30-1050 (1069) USCOMM-DC 60376-P69 U.5. GOVERNMENY PHINYING OFFICE: I959 0-35631l

Claims

1. In a gas turbine wherein a turbine disk is mounted on a shaft rotatably supported in a casing, said turbine disk extending substantially perpendicular to the axis of said shaft and having turbine buckets and platform means affixed to the outer rim thereof, said buckets receiving a driving force from a hot motive fluid moving in a direction generally parallel to said axis of said shaft and the driving force being transmitted to said shaft via said turbine disk, means located radially inward of said platform adjacent said turbine disk for introducing liquid coolant within said turbine in a radially outward direction into open-circuit distribution paths by which said coolant traverses surface area of said rim and said platform means, passes into cooling channels in said buckets and exits from said channels in a radially outward direction, the improvement comprising: a. a plurality of separate cylindrical surfaces, the elements of which extend parallel to the axis of the shaft, each of said surfaces being formed on the radially inward side of the platform means, one of said cylindrical surfaces being located in the given liquid coolant distribution path leading to each side of each turbine bucket adjacent the inward end of the cooling channels therefor and all portions of those cylindrical surfaces receiving coolant from a common downstream distribution path being located equidistant from said axis.