US2891382A - Liquid-cooled turbine - Google Patents

Description

June 23, 1959 Filed July 29,. 1952 W. S. BROFFITT `LIQUID-COOLED TURBINE 2 sheets-Sheet 1 wt/WVM ATTORNEYS June 23, 1959 w. s. BROFFITT 2,891,382

LIQUID-COOLED TURBINE Filed July 29, 1952 2 Sheets-Sheet 2 INV EN T 0R.

ATTOHMYS States p 2,891,382? Patented .lune 23, 1959 LIQUID-COLED TURBINE Wilgus S'.` Brolitt, Indianapolis, Ind., assigner to General lllloltors Corporation, Detroit, Mich., a corporation of e aware Application July 29, 1952, Serial No'. 301,523

3 Claims. (Cl. 60=39`.66)

My invention relates to turbines, being directed. to the cooling of high-temperature turbines such as gas turbines.

The. -benets to be expected from cooling of gas turbines, both in terms of higher output and higher eici'ency, are so well known as to require no elaboration. Many proposals have been directed to this end", particularly to cooling the turbine blades, which are the most critical point, and the turbine wheel. Notwithstanding these proposals, most gas turbines are kept within endurable temperature limits simply by diluting the motive gases with excess air, which results in low efliciency.

In some cases, turbine wheels yandv buckets have been cooled' by circulation of air over or through the wheel and through the buckets. Since very considera-ble amounts of air are required for a small degree of cooling, and the air must be forced through against the pressure of the 'turbine motive huid, this, too, is inefficient.

Cooling by liquids has also been the subject of numerous proposals. Practical difliculties of great magnitude stand' in the way of exploitation of these proposals.

vMy invention involves the cooling of the turbine by a liquid spray or mist carried by a current of air, the coolant being supplied directly to the turbine. In this way compressor erosion is eliminated'. Also, the amount of cooling obtained from a given weight of liquid is much greater than from injection into the air inlet. This is particularly signicant in aircraft where weight savings are highly important. As a result of the invention, l'ess coolant need be carried, or the same amount will provide effective cooling for a longer time.

The liquid-laden air stream will absorb far more heat than air alone because of heat absorbed by vaporization of the liquid; and the air acting as a carrier provides sui-licient volume for adequate circulation. The loss of power involved in pumping the coolant into the engine is reduced, since less volume of coolant isrequired than when air alone is used.

A further feature of the invention is that. it isV Well adapted to secure the advantages of` air cooling when the liquid coolant is not being supplied.

The principal objects of the invention are to improve the performance of gas turbine engines; to improve the cooling of such engines; to cool a turbine by a mixture of air and a liquid mist or spray; and to provide particularly suitable means for introducing a coolant into a turbine;

The principles and advantages of the invention will be clear to those skilled in the art from the succeeding rdescription of preferred embodiments of the invention and the accompanying drawings in which: Fig. l :isl av longitudinal sectional View of the turbine end of a turbojet engine; Fig. 2 is an enlargement of a portion of Fig. l; and Fig. 3 is a partial sectional view illustrating' a modication.

The invention is illustrated as applied toan engine of known type which need not `be described in detail. Referring to Fig. l, a turbine wheell or disk is` integral with a shaft 11 which drives` a compressor (not shown). The compressor supplies air to combustion cham-bers (not shown) the outlet ends. 12 of which discharge motive Huid into an annular turbine nozzle ll3 mounted in a casing 14 xed to a frame i6 of the engine which also mounts the turbine shaft bearing 17.

A turbine shroud i8 and an exhaust pipe 19 are fixed to the nozzle casing la. The exhaust pipe and a tailcone 21 supported therein by a number of struts 22 (only one of which is shown) define the exhaust passage from the turbine.

The nozzle 13V directs the motive uid against buckets 23 mounted in the rim of the Wheel 10, as by multiple dovetail type roots.

Air is supplied through passages 24 in the frame I6 to a fan 26 on the forward face of theA turbine wheel, from which it is discharged through openings 27 in the frame and flows out between the combustion chambers. This air flow reduces the heating of the bearing 17. An oil seal 28 and a labyrinth seal 29 for the motive uid are provided.

The structure described above is of a known engine. The turbine wheel and buckets are modified, however, to provide for coolant circulation. The buckets are formed with a passage 3l extending the length of the blades and are preferably tted with -blade liners (not shown), which may be as described in my copending application- Serial No. 289,341, tiled May 22, 1952 (now abandoned).

The passages 31 (Pig. 2) communicate with notches 32 in the base of the blade supplied with cooling medium throughv drilled passages 33 extending to the rear face of the turbine disk itl.

A secondary disk 34 mounted on the disk 10 defines a radial path 36 between the disks for coolant, and a cylindrical hub 37 of the disk 34 denes a chamber 38' into which the coolant is introduced. Blades 39 on the disk 34 constitute a centrifugal fan to force the coolant into the turbine.

'1" he disk 34 is mounted on the turbine wheel by means of cap screws 4l extending into bosses 42 on the Wheel, the coolant flowing between the bosses. The margin. of the disk 34 is held in engagement with the wheel 10 by a retainer ring 43 lodged in a groove in the rim of the wheel' and additionally secured by pins 44.

The tailcone structure comprises a front plate 46 bolted to astiiener ring 47 at the forward end of the cone 2L A flanged sleeve 4S constituting a part of the air conduit is bolted' to the plate d'6 and extends into the hub 37. A shaft seal structure Sil) preferably of the piston ring type is iitted' on the sleeve 48 tor co-action with the hub.

The piston ring seal', as illustrated more clearly in Fig. 2, comprises a collar 49, a sleeve 51, a ring 52, a sinuous or wavy spring 53, and a snap ring 54, the latter being lodged in a groove in the sleeve 48 to retain the parts 49, 51, 52, and S3. These parts may be of steel. The sealing is acCompl-ised by two piston ring seal members 56 mounted on an expander S7 between rings 58' and 591. The rin-gs 58 and 59 are Phosphor bronze and act as bea-ri-ng members against the two piston rings and provide axial clearance for the expander 57. It is to fbe understood that the specific character of the seal is immaterial to the invention and that seals of other types as, for example, labyrinth seals might be employed.

A plate 61 which supports the liquid spray nozzle 62 and a flange 63 of a thin-walled air conduit elbow -64 are also bolted to the plate 46. Apertures 66 in the plate 61 permit passage of air. A thin-walled duct 67 (Figs. 1 and 2) which conducts air into the turbine has a bell end which tits over a suitable seal 68 on the elbowv 64.

A pipe 69 running through the duct 67 supplies water or other suitable liquid such as a mixture .of water and alcohol (which wil-l lbe referred to as water) under pressure to the nozzle 62. A fitting 71 on the pipe screws into an elbow 72 which is screwed into the body of the nozzle 62. The tubular nozzle body is fixed to the plate 61 by double nuts 73.

The nozzle body mounts a spray tip 74 which may be of known type defining a swirl chamber 76 into which the water enters through tangential ports 77, the spray being discharged from a reduced outlet '78.

The air duct 67 is mounted within an outer duct or jacket 79 which insulates the duct 67 from the hot combustion gases and serves to bring cooling air into the tailcone 2l. The duct 79 comprises an inner section 31 extending through and welded to the tailcone 21, an intermediate section 82 piloted into the section 8l, and a short outer section 83 which is welded to the duct 67 and closed at the outer end. There is a short gap between the tubular sections 82 and S3, which are coupled together by a coupling of known type comprising a resilient ring 84;- compressed around the circumferentially lribbed ends of the sections by an inwardly flanged ring l86. A ange S7 welded to the duct section 32 is bolted to the exhaust duct 19. A pipe 8S conducts compressed air into the duct 79 from any suitable source (not shown), such as the compressor of the engine, for cooling the tailcone. This air iiows through the duct 79 into the tailcone, through openings S9 in the plate 46, and into the exhaust duct through the gap between the turbine wheel and the ring 47.

A fitting 91 in the form of a anged disk is flexibly mounted on the outer end of the duct 67 by a coupling 92 of the type previously described. The water pipe 69 has brazed thereon a sleeve 93 extending through a central opening in the fitting 91, the disk being clamped 'between a shoulder on the sleeve and double nuts threaded thereon. Holes 94 in the fitting provide for entrance A,of air to the duct 67.

v This air is drawn into the chamber 38 by the fan 39. `If desired, the fan may be omitted and air may be supplied to the duct 67 under pressure. The arrangement illustrated is preferred, however.

Water is supplied to the turbine when needed under control of a valve 96 in the line 97 from any suitable pump (not shown) to the pipe 69. Suitable littings (not shown) may be provided to couple the supply line 97 to the pipe 69.

The slip joints between the duct 67 and elbow 64 and between the outer duct sections S1 and 82, and the exible couplings 84 and 92 provide for diiferential expansion of the radial inlet lines and accommodate relative expansion of the parts of the engine due to heating in service and due to cutting on or off the water.

The operation of the turbine cooling mechanism presumably will be clear from the foregoing, but may be outlined brietly. In normal operation, air is drawn through the duct 67 into the chamber 38 and between the disks 10 and 34 by the fan 39 which forces it through the hollow turbine buckets 23 and discharges into the motive fluid passage at the tips of the blades. In this manner one important advantage of the invention is accomplished; that of obtaining the benefits of air cooling directly applied to the turbine buckets and turbine wheel even when the water cooling is not employed. Cooling air is also introduced from any suitable source of air under pressure, such as the compressor of the engine, through the pipe 83 and shroud or duct 79 into the tailcone, from which it is discharged just aft of the turbine wheel rim, thus cooling the tailcone and the structure by which the air is introduced to the wheel.

When additional cooling is desired in connection with an increase of fuel supply for increased engine output, the valve 96 is opened and a liquid such as water, or preferably water mixed with an anti-freeze liquid such as alcohol, is introduced through the pipe 69 and sprayed by the nozzle 62 into the chamber 38 from which it is carried by the air stream between the two disks and out through the buckets, as previously described. The heating, vaporization, and superheating of the liquid absorb large quantities of heat from the wheel and Ibuckets and, with this additional cooling, the turbine will tolerate a. very substantial increase in the temperature of the mo tive fluid, with a resulting increase in power output either in the form of `a propulsive jet, shaft horsepower, or a combination of the two. It will be understood that in an aircraft installation the water cooling will ordinarily be relied upon primarily as an emergency device on account of the limitation of the quantity of water that can be carried. In stationary installations such limitations will not apply.

Fig. 3 is a partial view of a modification of the invention in which parts which may be the same as those of Figs. l and 2 have the same reference numerals -as Figs. l and 2, and parts which are similar but modified are given primed reference numerals corresponding to those of the other figures. In the modification of Fig. 3, compressed air is supplied to the duct 67 through a conduit 88 supplied with compressed air through any suitable source. Since the air is supplied under pressure, the fan blades 39 of Fig. 2 may be omitted if desired. The water pipe 69 may be the same as in the other form and may be supplied through a suitable valve. The cap 91 at the upper end of the duct 67 is not provided with air openings, and thus closes the outer end of the duct. The outer duct 81 may be similar to the duct 81 except that it is not provided with a compressed air inlet, the air for cooling the duct 81' and the tailcone being supplied through the pipe 88', the upper end of the duct 67', and holes 101 in the wall of the duct 67 which allow compressed air to escape into the duct 81.

The operation will be obvious. Compressed air supplied through the pipe 88 flows through the duct 67, and through the annular passage between this duct and the duct 81' to cool the turbine and tailcone respectively,

as previously described. Water may be supplied either continuously or when load conditions warrant it through the pipe 69 to the spray nozzle 62, and the resulting coolant ows through the turbine in the manner previously described.

The advantages of .the invention by comparison with other arrangements for cooling a turbine and particularly by comparison with the injection of liquid into the compressor inlet will be apparent from the fact that study indicates that for -a given amount of cooling of the turbine only approximately one-fth as much liquid is required in a device according to the present invention as when liquid is injected into the inlet of the compressor.

This means, of course, that for a given capacity for carrying coolant in the aircraft increased thrust may be obtained for a much longer period of time or, if desired, the engine rating can be augmented to a greater extent than when the liquid is fed to the air inlet. l

The preferred embodiments of the invention have been described in detail for the purpose of explaining the principles of the invention and .the best known means of putting the invention into practice. It is to be understood, however, that many modiiications of the structure may be made within the scope of the principles of the invention by the exercise of skill in the art and that the invention is not to be considered as limited by this de,- scription. l

I claim:

l. A turbine comprising, in combination, a turbine wheel; hollow blades thereon; means defining an annular path for motive fluid through the turbine, the said means including a tailcone in the turbine exhaust passage; an air duct leading across the motive tluid path'to the 'turbine wheel and terminating adjacent the wheel at the'axi-s thereof; means for diffusing a liquid in the air'owing through the duct; means defining a chamber between the turbine wheel and the duct; the turbine wheel de;- ning passages from the chamber to the blades for con'- duction of air and liquid spray from the duct and diffus'- ing means; and a jacket surrounding the said duct within the said motive uid path and adapted to conduct cooling air into the tailcone.

2. In a turbine, the combination comprising a turbine rotor including a Wheel having hollow blades thereon, means defining an annular path for motive uid through the turbine, the said means including a tailcone in the turbine exhaust passage, a first cooling air supply duct leading across the motive fluid pathto the turbine Wheel and terminating adjacent the wheel at the axis thereof, a second Icooling air supply duct spacedly embracing said first duct within the said motive fluid path and adapted to conduct cooling air into the tailcone, means deining a chamber between the turbine Wheel and said first duct, means for diffusing a liquid in the air flowing through said first duct into said chamber, said cooling air supply ducts forming insulating jacket means for said liquid diffusing means, and said turbine rotor defining passages from said chamber through said blades for conduction of air and the diffused liquid from said rst duet and from said diffusing means.

3. A turbine as recited in claim 1 including means for supplying air under pressure to the air duct and an air connection from the air duct into the jacket.

References Cited in the le of this patent UNITED STATES PATENTS Re. 23,172 Bchi Nov. 29, 1949 1,824,893 Holzwarth Sept. 29, 1931 2,401,826 Halford June 11, 1946 2,434,134 Whittle Jan. 6, 1948 2,438,998 Halford Apr. 6, 1948 2,440,069 Bloomberg Apr. 20, 1948 2,442,019 Ray May 2S, 1948 2,598,176 Johnstone May 27, 1952 2,620,157 Morley et a1. Dec. 2, 1952 2,636,344 Heath Apr. 28, 1953 2,639,579 Willgoos May 26, 1953 2,647,368 Tn'ebbnigg et al Aug. 24, 1953

Images