US2605081A - Cooling means for gas turbine wheels - Google Patents

Description

Jul 29, 1952 I J. s. ALFORD COOLING MEANS FOR GAS TURBINE WHEELS Filed April '25, 1946 FEW 53: A;

Inventpr. Joseph SJAlf-ord,

. His Attorney.

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Patented July 29, 1952 COOLING MEANS FOR GAS TURBINE WHEELS Joseph S. Alford, N ahant, Mass., assignor to, General Electric Company, a corporation of New York Application April 25, 1946, Serial No. 664,852 7 This invention relates to an improved arrangement for cooling the disk of a high temperature turbine bucket wheel, specifically to a novel form of combined cooling cap and exhaust hood for a single stage axial flow gas turbine wheel. The invention is particularly adaptable to gas turbines such as those used for driving a compressor to supercharge a reciprocating internal combustion engine.

' An object of the invention is to provide an improved arrangement for cooling the downstream or exhaust side of the disk of a high temperature turbine bucket wheel.

Another object is to provide an improved form of combined exhaust hood and radiation type cooling cap for a gas turbine such as those used in turbosuperchargers.

A further object is to provide a cooling cap and exhaust hood arrangement which is simple in construction and can readily be disassembled for inspection and servicing. I

A still further object is to provide an improved form of radiation type cooling cap for turbine disks.

Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawings, in which Fig. 1 is a sectional view of a gas turbine having an exhaust hood and cooling cap in accordance with the invention; Fig. 2 is an end view, partly cut away, taken in the direction of the arrows 2-2 in Fig. l; and Fig. 3 is an enlarged sectional view of a portion of the structure shown in Fig. 1.

Referring now to Fig. l, a turbine bucketwheel consisting of a disk I with a circumferential row of buckets 2 is secured, as for instance by welding, to a flanged shaft 3 supported in suitable bearings (not shown) in a bearing housing 4. Motive fluid is supplied to the flanged inlet opening 5 of an annular nozzle-box 6, which has a cast nozzle diaphragm I defining a ring of circumferentially spaced nozzles 8.

Surrounding the bucket-wheel is an vannular flange 9, shown in the drawings as being formed integral with the nozzle-box 6. This flange serves to support the exhaust hood lll and'cooling cap ll.

Exhaust hood consists of a casing formed of sheet metal and having at one side a circular opening arranged to surround the bucket wheel. As may be seen more clearly in Fig. 3, the means for supporting the cooling cap and exhaust hood consists of a flanged ring [2, which may be seam-welded to the axially extending flange 9'.

3 Claims. (C1. 253-3915) A ring l3, Z-shaped in cross section, has a vra diallyinner portion secured by a circumferential row of threaded fastenings l5 to the flange [2. The radially outer portion of Z-ring; I3 forms a flange to which .is secured exhaust hood l0 by means of a circumferential flange l6, which may be welded to the exhaust hood in the manner indicated in Fig. 3; The exhaust hood flange I6 maybe secured to Z-ring 13 by any suitable clamping device, as for instance a (mick-detach able band clamp 11. The clamping device comprises a split ring. u-shaped in cross section, and having the split. ends of the ring drawn together by means of a bolt [8 arranged in suitable lugs l9 welded to the respective ends of the split ring. Such quick-detachable. clamping bands are Well-known in the art, and further details of the device shown in the drawings are not necessary to an understanding of the. present invention.

The exhaust hood I0 is provided withadischarge portion 20, which may be connected to an exhaust gas conduit '(not shown), or may be shaped to define a nozzle 2i arranged to discharge the turbine exhaust gases" directly into the atmosphere. Nozzle 2| may be designed to produce a certain amount of jet thrust, when used in an aircraft.

The cooling cap ll'is of a type known as a radiation cooling cap because the coolant does not contact the turbine wheel directly, heat. being transferred from the bucket-wheel to the ad jacent outer Walls of the cap by radiation and convection. This type of cooling cap has been previously disclosed in U. S. Patents 2,364,037 and 2,370,694, granted November 28,,l944'and March 6, 1945" respectively, on applications of Chester W. Smith. The cooling cap shown in Figs. 1 and 2 consists of anouter dome-shaped member 22 and aninner, concentric wdox'ne 23.. The central portion of dome 23 may be .secured to dome 22 as by spot-welding at the location 24 in Fig. 1. Arranged between the outer circumferential portionsof the domes 22, 23 are a plurality of concentric rings 25, Z-shaped in cross section, and welded together and to the domes in a manner which will be obvious from Figs. 1 and 3. It will be seen that rings 25 form outer concentric annular ribs facing the hot turbine wheel disk and corresponding annular ribs extending in the opposite direction and projecting into the coolant inside the cooling cap, as will appear more clearly hereinafter. Thus, the rings 25 serve as cooling fins for receiving heat by radiation and convection from the hot turbine supplied to the cooling cap.

At diametrically opposite locations, the outer cooling cap dome 22 is provided with radially extending slots 26a. and 26b. Secured to the outer surface of dome 22, as for instance by seamwelding .along'the flanges 2'! in Fig. 2,'is' a substantiallycylindrical conduit 28, which may be formed in two halves seam-welded together at the flanges 29.

bent at right angles to form the supporting bracket 3 I. As may be seen in Fig. 1, the bracket 3| is secured to a Z-shaped bracket 32 by means of suitable threaded fastenings 33, having one or more shims 34 therebetween. Bracket 32 is secured to the nozzle box flange l2 by certain of the threaded fastenings [5. 'The opposite end of conduit 28 is secured to a similar bracket 32a by means of threaded fastenings 35 and shims 34a, through a U-shaped link 36 secured to conduit'28 by means of pivots 31 This pivoted link construction permits differential thermal expansion between the cooling cap assembly and the nozzle-box structure to which it is secured; and it ismore fully described and claimed in U. S. Patent No. 2,362,509 granted November 14, 1944 on an application of Dale D. Streid.

As may be seen in Fig. 3, one end of conduit 28 is arranged to project through a circular opening 38 in the exhaust hood [0. For convenience in assembly and disassembly, some clearance is provided around conduit 28, and this clearance space is sealed by means of a suitable circular packing 39. 'The packing is tightly compressed into contact with the outer surface of conduit 28 by. means of a split clamping band 43 provided with a screw 4| (Fig. 1) arranged to draw together the split ends of the clamping band. Furthermore, packing 39 is held securely against the outer surface of exhaust hood It by means of a plate 42 having associated therewith three or more threaded fastenings 43, which may be secured to the exhaust hood I and project through tubular spacers 44, in a manner which will be obvious from Figs. 1 and 3.

Secured within conduit 28 is a second smaller conduit 45, which has an open end spaced from the end plate 30 of conduit 28, the other end of conduit 45 projecting through the open end of r conduit 28. Conduits 45 and 28 serve as the coolant inlet and outlet respectively, as described below. r

. It will be understood by those skilled in the art thathot motive fluid is supplied to the flanged nozzle-box inlet 5 and flows through the turbine and exhaust hood as indicated by the arrows 43 in Figs. "1 and 2; The flow of coolant through the coolingcap I l is as follows. A suitable cooling fluid,-such as comparatively cold air from the surrounding atmosphere, is supplied through a suitable conduit (not shown) having an open end which faces into the slip-stream to the projecting open end of conduit 45, whence it flows in the direction of the arrows 41, through the other open end of conduit 45 as indicated by arrows 48, thence through slot 26a in dome member22 in the manner indicated by arrows 49. Once inside the annular chamber defined by outer dome 22, inner dome 23, and heat transfer rings 25, the cooling fluid flows around as indi cated by arrows 50, through the second-slot 23b and into the space defined between conduit 45' and conduit 28, as indicated by arrow 5| (Fig. l) A transverse baffle 23a closes the small openings One end of conduit 23 is closed" by a transverse plate 30, whichhas a portion defined on either side of inner conduit 45, so that the coolant fluid cannot flow through but is compelled to flow the path 48, 49, 50, 5|. The spent coolant fluid may be permitted to discharge into the space surrounding the machine, as indicated by arrows 52, or it may be led away by a suitable duct (not shown), which may have an open end adapted to discharge the fluid in a direction generally opposed to, or aspirated by, the slip stream.

In assembling a turbine embodying my invention, the cooling cap H is first secured by means of brackets 32, 32a and threaded fastenings 33 and 35 to the nozzle-box assembly. Any desired clearance between turbine wheel disk I and the adjacent edges of cooling cap domes 22, 23 and rings 25 may be secured by selecting shims 34 and 34a of an appropriate thickness'and number. It will be apparent thatwith the exhaust hood removed, the cooling cap H is completely exposed for inspection and servicing, while convenient access may be had to the turbine buckets 2 and nozzle diaphragm i through the generous opening defined by nozzle-box flange 9. Attention is particularly directed to the fact that the means for supporting the cooling cap is entirely independent of the exhaust hood, so that the cooling cap can be assembled independently of the exhaust hood; and the exhaust hood can be assembled or removed without disturbing the cooling cap. This arrangement greatly facilitates installation and maintenance of the turbine when used in aircraft applications, where space is at a premium and much complex ductwork and other components must be packed into the small space available.

After cooling cap Ii is inplace, the exhaust hood I3 is assembled by slipping the opening 38 over the projecting ends of coolant conduits 45, 28, then sliding the exhaust hood axially along the outer surface of conduit 28; meanwhile causing the lower inner portion 53 (Fig. l) of the exhaust hood flange It to follow the dotted path indicated by arrow 54 until flange l6 reaches its final position relative to Z-ring I3. Band clamp 11 may then be assembled around the cooperating flanges and drawn together with bolt 18, thus affixing exhaust hood [0 firmly .to nozzlebox flange 9.

The packing for the clearance space at 38, ma then be assembled by slipping packing 39 over the projecting end of conduit 28 and assembling the split retainer ring 40 around the packing 39. Plate 42 is then placed on bolts 43 and drawn down onto spacers 44 by tightening the nuts on bolts 43. Packing retainer ring 43 is next drawn tight by means of the screw 4!. Thiscauses the packing to be compressed tightly against the outer surface of coolant conduit 28, and against the outer surface of exhaust hood Ill.

It will be apparent that the length of spacer tubes 44 may be so selected as to limit the degree to which plate 42 can be drawn down against the retainer ring 40, 'thuslimiting the amount packing 39 can be compressed.

It will be noted that the angular relation be,- tween the exterior end of conduit 45 and the exhaust discharge opening 2! may be varied simply by properly locating the opening 38 in the circumference of the exhaust hood.

It will be seen that my invention provides an improved form of radiation type coolingv cap, which may be independently supported from the turbine nozzle-box and requires only one opening through the exhaust hood for providing the flow of coolant'through' the cooling cap. im-

nozzle box.

proved radiation type cooling cap is particularly advantageous when used in connection with an exhaust hood, as shown in the drawings and described above, because'of the extreme ease with which the hood may be assembled and removed for servicing, with only one packed joint to be disassembled and only one quick-detachable coupling device for securing the exhaust hood to the In both military and commercial aircraft, an exhaust hood and cooling cap arrangement made in accordance with my invention provides important savings in the time and cost of inspection and maintenance.

While my invention has been particularly described as applied to a gas turbine for driving a supercharger or other device in an aircraft, it Will'be readily appreciated by those skilled in the art that it is broadly applicable to axial flow high temperature turbines used for other pur- Doses.

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

1. In a high temperature turbine having a bucket-wheel and nozzle means for supplying motive fluid thereto, an exhaust hood detachably secured to the nozzle means around the bucket wheel and having an exhaust gas discharge opening and a single coolant conduit opening and means within the exhaust hood for cooling the exit side of the bucket-wheel disk, said means including a radiation type cooling cap, means securing the cooling cap to the nozzle means at locations surrounded by said hood whereby the exhaust hood may be removed without disturbing the cooling cap, an inlet conduit for supplying a cooling fluid to the cooling cap and a discharge conduit for conducting used coolant from the cooling cap, one of said coolant conduits being contained within the other with said coolant conduits projecting through said coolant conduit opening in the exhaust hood.

2. In a high temperature turbine having a bucket-wheel and a nozzle-box for supplying motive fluid t the bucket-wheel, an exhaust hood detachably secured to the nozzle-box around the bucket-wheel and having a single coolant opening and an exhaust opening, means within the exhaust hood for cooling the exit side of the Within the coolant discharge conduit and the end of said coolant conduits projecting through said coolant opening in the exhaust hood.

3. In a high temperature turbine having a bucket-wheel and a nozzle-box for supplying motive fluid thereto, an exhaust hood detachably secured to the nozzle-box around the bucket wheel and having a single'coolant opening and an exhaust opening, means within the exhaust hood for cooling the exit side of the bucket wheel disk, said means including a radiation type cooling cap, means supporting the cooling cap from the nozzle-box, said supporting means being enclosed by said exhaust hood, an inlet conduit for supplying a cooling fluid to the cooling cap, a discharge conduit for conducting used coolant from the cooling cap, the coolant inlet conduit being contained within the discharge conduit and the ends of said coolant conduits projecting through said single coolant opening in the exhaust hood, and packing means for sealing the clearance space between said coolant conduits and the exhaust hood.

JOSEPH S. ALFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,234,757 Gibson Mar. 11, 1941 2,348,748 Nichols May 16, 1944 2,362,509 Streid Nov. 14, 1944 2,364,037 Smith Nov. 28, 1944 2,370,694 Smith Mar. 6, 1945 2,388,952 Clark Nov. 13, 1945 2,414,840 Streid Jan. 28, 1947 2,434,134 Whittle Jan. 6, 1948 2,465,846 Clegern Mar. 29, 1949

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