US2390506A

US2390506A - Turbine with overhung rotor

Info

Publication number: US2390506A
Application number: US462859A
Authority: US
Inventors: Buchi Alfred
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-05-23
Filing date: 1942-10-21
Publication date: 1945-12-11
Anticipated expiration: 1962-12-11

Description

. 1l, 1945. A. BcHl TURBINE WITH OVERHUNG ROTOR Filed oct. 21, 1942 4 sheets-.sheet 1 fave/2MP' 11, 1945. A. BUcHl TURBINE WITH OVERHUNG ROTOR 4 sheets-sheet 2 Filed Oct. 2l, 1942 11, 1945. A. Buck-u` TURBINE WITH OVERHUNG ROTOR Filed Oct. 2l, 1942 i 4 Sheets-Sheet 5 Dec. l1, 1945. A. BcHl TURBINE WITH OVERHUNG ROTOR Filed Oct. 2l, 1942 4 Sheets-Sheet 4 Potented Dec. l1, 1945 TURBINE ain-ea michi, winterthur, switmima Application october 21, 1942, sei-iai No. 462.859 In switzerland May za, 1942 This invention relates to overhung rotor turlbines, particularly for motive uids, such as hot gases, and is distinguished in that the turbine rotor, to which the motive fluid is admitted tangentially from without through one or more inlet de- `1 vices and a limited number of inlet nozzles, is .l composed of a relatively small number of blades that are approximately radially directed along an i outer portion thereof at least and are substantially plane transversely to the turbine axis, the blad- Y5 claims. loi. 253-39) exit of the turbine rotor immediately as regards the direction o i' the turbine axis, or the ilow of ing being gradually and smoothly so dellected' from the radial into the axial direction that the entering gases are diverted at a great radius of l curvature into the axial direction and then pass `into aldilluser under a lower pressure than the exhaust gas may be compelled to pass over into another differently directed diffuser by means of a ilow change-over device. The coolingot the inner end portion o! the turbine rotorand Vof the adjoining filler piece of the diffuser can be eiected by meansof a cooling medium which may be supplied particularly from the end of the driving shaft remote from the turbine rotor.

The uncooled turbine casing can be closed by meansvof a hollow closure member provided with nal discharge pressure behind the respective turbine" stage but ata relatively high velocity whereupon the velocity of the gases is converted to correspond to the pressure against which the gases discharge. The turbine inlet parts can surround the turbine rotor spirally and their cross sections of free passage may decrease to such an extent that the velocity of admission of the gas is substantially uniform throughout up to the inlet nozzles.

If several conduits supplying the motive gas inv dependently of each other to .the tangentially didesigned for such a discharge velocity that interiorly of the diffuser arrangement a substantially axially directed flowof gas and at the outer periphery of said arrangement a iiow of gas with a rotative component is set up -in order to prevent separation of gas from the outer peripheral portions of the diiuser arrangement and to obtain a satisfactory conversion of velocity into pressure also ina diffuser arrangement which has a relatively short lengthand is flared at a relatively large angle of inclination. I

The rotor blades can be worked out of the mal l terial of the rotor body and may have bases that are thickened particularly in the radial direction, `that is, toward the wheel hub and, if desired,` also the disc of the turbine rotor.

`Inthe interior of the diffuser joining with the ment. The blading of the turbine rotor may be turbine rotor a conically tapering guide or filler; l

piece extending in the direction of the turbine axis may be arranged for the purpose of obtaining conversion of velocity into pressure at a minimum of energy losses.

'I'he ilared diffuser can be arranged to join the a cooling device only at the driving end of the turbine. With a view to ensuring accuratecentering of the hot and consequently expanding turbine casing by means of the cooled scarcely expanding closure member, between these two parts at least'two pairs of diametrically opposed keys l may be arranged the axes of which intersect each other in the turbine axis.

. 'I'he backside of the turbine rotor disc may be provided, for example, with a cooling fan blading and, if desired, also with an associated covering disc for cooling the turbine rotor. by means of cool air. In conjunction with this cooling arrangement cooling air may be forced through the Y turbine rotor blades through bores thereof or through openings in the rotor disc against the jacent to the points of entry of the gases and the blade bases. The cooling air may be derived from the surroundings or any other suitable extraneous place, for example, from any suitable spot on the pressure sides of the turbine driven blower. In such an event the arrangement of a cooling Ian blading on the backside of the turbine rotor can be dispensed with. However, in order to provide substantial cooling also on that side it is appropriate to employ cooling ribs or the like.

l With a `view to obtain equalisation of pressure during the operation in the axial direction of the rotating turbine parts as completely as possible. on the backside of the turbine rotor sealing means are arranged at a portion within the `outer diameter of the turbine rotor. In order to prevent penetration of exhaust gases to the driven side conduction means communicating with the atmosphere or the exhaust gas conduit may be arranged to lead rearwardly away from the point of sealing. l

Two embodiments of the invention and several detail modifications are illustrated by way of example only in the accompanying drawings, in

which Figs. 1 to 6 represent a single stage gasI turbine, as a ilrst embodiment of the invention, the turbine being in driving engagement with a blower rotor and having four different gas supply conduits,

Fig. 1 being a, section on the line I'-I in Fig. 2.

taFlg. la is an enlarged sectional view of a de- Fig. 2 is a section on the line II--II in Fig'.4 1. Fig. 2a is a sectional view on the line IIa-IIa of Fig. 1, the turbine rotor being omitted for the 'sake of simplicity.

Fig. 3 is a section on the line III-III in Fig. 2.,

i n. on the lineVII-VII in Fig. 8 of a lsecond embodiment of the invention.

Fig. 8 is a sectional view on the line VIII-V111 in Fig. '1. n e

Fig. 9 is a sectional view on the line IX-IX in Fig. 1o shows a modification of a detail of Fig. '1, and i Figs. 11 and 12 each represent diagrammatically various velocities.

Fig. v1 shows the overhung turbine rotor I which is rotating in a bearing support 3 by means of a rotor from vanishing abruptly, at loss of energy on the inside of the blading of the turbine rotor. Instead of arranging the diiruser 22 coaxlally with the turbine it may be arranged to discharge in another direction, for example as shown at well as-the cooled closure casing 1, the turbine shaft 2. The numeral 4 designates the turbine A admission casing, whereas 5 refers to the nozzle carrierringcontainlng the inlet blades 6 and I-l, and 1 refers to a closure member which is provided with a cooling space 8 and is arranged between the gas inlet casing 4 and the compressor collector casing 9. A flow of cooling liquid may be maintained through cooling space 3 by inlet pipe 9 and exit pipe 8", and this prevents to a large extent transfer of heat from the hot turbine gases to the cooler air being compressed. 'I'he turbinerotor forms an integral piece having a wheel body I the blades I1 of which are, for example, workedout of the material of this body. These blades Il, one of which is shown in elevation centrally of the wheel, have the characteristic feature that at least the outer portions, that is, the'entrance ends I9 thereof, extendy radially of the rotor axis and the substantially plane blade flanks extend transversely to the turbine axis. At the bases I3-of the blades I1 at the points where the latter are connected to the wheel disc I thickened blade portions are provided for reasons of strength.

rotor I, and the blower casing 9 is maintained both

casings

4 and 1 are ilxedin relative position to each other by'rneans of four keys 21 the axes of which intersect the axis of the turbine.

For cooling the turbine rotor disc provision may be made for supplying cooling air to the backside thereof. To this end, in an arrangement as shown in Fig. 1, on the backside of the turbine rotor I blades 29 are arranged through which coolingmairis withdrawn from a, space 29. This cooling air can be atmospheric air or, for example, air withdrawn from the blower collector casing 9 through a conduit 30. The cooling fan blades 28 are covered by a covering disc 3|. The air thus supplied passes through bores 32- and 32a,V which are appropriately arranged in the disc I at least peripherally thereof and\are so directed as to lead the air in the direction toward the surfaces of the blades Il, that is, the outer ends yI9 adjacent the bases I3 thereof so that the temperature of said parts is also decreased.

For preventing the escape of gases from the backside of the turbine rotor sealing means 33 are provided. For the same purpose similar means 34 of smaller diameters may be provided in con- 4 Junction therewith, for example, on the covering blades also extend radially or are only slightlyv build of the diffuser 22 is such that at the end disc 3|. The space 35 between the'sealing means 33 and 3'4 may be put in communication with the atmosphere or with the discharge conduit 23 of the gas turbine through a conduit 36. These

seals

33 and 34 may be of the conventional labyrinth type as indicated in Fig. la. v

In the center of Fig. 2, being a section on the line II-II in Fig. l, the construction of the turbine rotor blades I1 is shown in detail. v4Of; these blades I'l, which are plane, the outer portions I9, at least, extend in the radial direction while the blades taken as a whole extend transversely to the turbine axis. The discharge edges 20 of these inclined to the radial direction. The inlet casing 4 of the turbine is integral with the diffuser arrangement 22. Four supply conduits IIJ, Il, I2 and I3 (see also Figs. l and 3) form an arrangement of crowded convolutions so that the outer diameter of the casing 4 is reduced to a minimum. The areas of free passage of the spiral entrance portions of the conduits I0, II, I2 and I3 decrease to such an extent that uniformity `oivelocity is maintained up to the entry of all the tapering nozzles I4 and but a relatively slight diversion of the gases into the direction of admission" is required to take place. Between the spiral inlet conduits II), II, I2 andv I3 four separating blades I5 (Fig. 2) are provided and in each interstice therebetween are arranged only two nozzle blades 6 which also extend in the tangential direction and which jointly ensure that the gases are admitted to the turbine rotor in the required direction and at the appropriate velocity. Due to the tangential guiding effect producedby the inlet conduits Il, II, I2 and Il, that is. that of the separating blades Il and the intervening blades 6 the iiow of gas undergoes diverting movements of large radii of curvature throughout. Consequently the losses of energy suffered in advance of the turbine rotor are only small. Fig. 2 further shows plainly the manner in which the supply conduits IIi, II, I2 and Il are crowded into narrow convolutions up to their exit ends. At 22 and 24 in Fig. 1 the outer wall and the inner guide wall respectively of the diifuser are shown in cross section. t

Fig. 3, being a'section on the line III- III in Fig. 2 exemplifies the manner in which the four separate supply conduits I0, II, l2 and I3 are relatively arranged.

Fig. 4, being a perspective view of the turbine rotor I, clearly shows the radially directed entrance ends I 9 and the approximately radially directed exit ends 20 of the turbine rotor blading I1. From this illustration itis plainly discernible that the approximately plane ilanks of the rotor blades extend transversely to the turbine axis and that the thicknessof these blades increases particularly in the radial direction and toward the blade bases I8 at the turbinewheel disc.

Fig. 4 further shows the

bores

32 and 32a as arranged in the turbine rotor disc I on a single common diameter, at least, for the passage of cooling air, thebores being so directed that this air is projected.V onto the surfaces of the blades, particularly those situated adjacent to the entrance edges andthe bases of the blades. Fig. 4 also illustrates that the cooling air is projected onto both flanks of the rotor blades, the front flank as well as the rear flank. 'Ihis feature is also illustrated in enlarged Fig.l 4a. Instead of bores 32, for example, notches 32" serving the same purpose may be provided in the peripheral edge of the turbine rotordisc I (Fig. The cooling air may also ilow over onthe circumference of the turbine disc from its back side into the turbine blading.

The second embodiment of the invention as shown in Fig. 'I comprises a gas 4turbine with only two inlet conduits I0' and II'. The numeral I1' refers to the turbine rotor blades having inlet edges I9' and exit edges 20'. 'I'hese exit edges 2U are cut oif obliquely to the turbine axis. It will 'be clearly seen that the innermost diameter of smallest length of the diffuser 22" lis smaller than the extreme diameter. of the outer exit edges 20' of the turbine blades I1. The reason for this construction is to-maintain the absolute velocity of the gas discharging from the turbine rotor at the inlet end of the diffuser 22 as completely as possible, for the purpose of avoiding energy losses due to vanishing of velocity. This is accomplished by keeping down the cross section of free passage at the inlet end `of the diffuser 22" at least to such a size as to correspond with the effective absolute gas discharge area of the tur- This construction a cooling blading 28 bine rotor I for withdrawing cooling air from the, space 2l.v These cooling blades are again closed,

laterally and towards outside by a covering disc ll. 'I'he individual blades Il are however provided with bores 32' through which-the :cooling air delivered by contrast to the construction shown in Fig. 1. The cooling fan withdraws air through the space 29 fromwlthout by means of a conduit so'. .Tnet

conically tapering interior piece 24 of the diffuser is in this case integral with the turbine rotor I. Alternatively bores 32, 32' and 32" (see also Figs. 4 and '5) for cooling air may be provided in the turbine rotor disc I at 4the same time.

In a construction as shown in Fig. 7 no gap losses arise in the discharging gas in contrast to the construction shown in Fig.` 1, due t'the fact that no gaps exist between the stationary and the rotatable parts.

'I'he central portion of the hub of the rotor I as well as said interior piece of the diffuser 24' are hollowed and cooled by a cooling means entering `at 31 and discharging at 38.

In Fig. 8 representing a section on the line VIII-VIII in Fig. 7, as seen from the left hand side of the Latter, the form of the turbine rotor blades I'I' inclusive of their radially directed inlet edges -I 9' and their substantially radially extending exit edges 20' is shown. The two supply conduits III and Il forming a crowded arrangement of convolutions taper also in this case spirally toward the two blades I5 separating said conduits from each other. Within the interstices between said blades I5 only ilve nozzle blades 6 are arranged in the nozzle carrier ring 5 for each supply conduit, for leading the gases into the turbine l rotor.

bine rotor blading minus the terminal thickness of blades. In this construction the exit edges 20' of the blades lie in a conical surface coaxial with Fig. 9 being a section on the line IX-IX in Fig. 8 shows the conduits I0 and I I' in their collateral disposition in parallelism with the turbine axis.

Fig. 10 representsa modification of the construction of the inlet nozzles Il and a corresponding form of the turbine rotor blading Il". The inlet direction of the nozzles I4 ls not radial, but inclined towards the axis of the turbine rotor I. This results in a reduced angle of diversion of the flow of the entering gas during its passing through the turbine rotor Fig. 10 shows the inclination of the inlet nozzle walls I6 to the turbine axis. 'I'he direction of the hollow parts of the turbine rotor blading I1" must be, of course, in correspondence with this inlet direction, asiwill also be seen in this figure.

Fig. 11 represents the gas inlet velocity triangle at the blade entrance IS-of the turbine in which ci designates the absolute gas admission velocity. u1 the velocity at the circumference of the rotor, Iand w1 the relative gas admission velocity which is approximately radially directed in accordance with the present invention.

Fig. 12 represents the gas velocity diagrams at the exit end 2U of the turbine rotor. The character u2' refers to the circumferential velocity at the extreme outer exit diameter, wz' to the rela- 'tive gas velocity thereat, and c2' to the corresponcling` absolute gas velocity. The character uz" represents the smaller circumferential velo-city at the blade bases, we" the relativegas velocity .at thelastnamed point, and c2" the corresponding absolute gas velocity.

illustrated in Fig. 12, the relative gas velocities the cooling fan is forced, in

from the wall surfaces even in a more widely,

flared and relatively shorter diffuser. For this purpose on the outer end the working angle a3" of the blades must be chosen to be smaller than at the inner end in conformity lwith an. For obtaining the various exit angles an' and an" in an arrangement according to the present invention the blade surfaces can be formed firstly of initially plane surfaces in conformity with the exit angle an" at the blade base' I8 and then the outer exit ends are bent up or pressed into the desired other direction in accordance with the exit angle an', if required in hot state.

Iclaim: i

1. In an overhung rotor turbine, particularly adapted for gaseous motive fluids, such' as hot gases, and discharging through a diffuser, a composlte gas inlet casing having various individual supply conduits, at least part of said conduits extending at the entrance to said casing in the direction of the turbine axis and all said conduits being crowded into` an arrangement of closely spaced convolutions terminating in a nozzle arrangement having a limited number of tangentiallydirected inlet nozzles, a turbine rotor body carrying a blading arranged in said casing within said nozzle arrangement, the individual blades of said rotor body being substantially radially directed along at least a radially outer blade portion and being substantially plane transversely to the turbine axis, said rotor body confining said blading by a concave portion having a relatively large radius of curvature adapting ,said blading to smoothly divert said motive fluid into the direction of said axis and pass it at, a high velocity but under a lower pressure into said diffuser where the gas velocity is converted into a pressure approximating the pressure `confronting the discharging gases.

2. In an overhung rotor turbine, particularly adapted for gaseous motive fluids, such as hot gases, and discharging through a diffuser, an inlet casing terminating in a nozzle arrangement, said arrangement, having av limited number of tangentially directed inlet nozzles, a turbine rotor body carrying a blading arranged in said casing within said nozzle arrangement and having a hub portion prolonged beyond said blading so as to extend into said diffuser to at least some extent thereby forming a rotating 'inner limiting member of said diffuser, the individual blades of said rotorbody being substantially radially directed along at least a radially outer blade portion and being substantially plane transversely to the turbine axis, said rotor body confining said blading by a concave portion having a, relatively large adapted for gaseous motive fluids, such as hot inlet casing having spirally tapering supply conduits terminating in a nozzle arrangement, said nozzle arrangement having a limited number of tangentially directed inlet nozzles, said casing' being integral'with said diffuser, a turbine rotor body carrying a blading arranged in said casing within said nozzle arrangement, the individual blades of said rotor body being substantially radially directed along at least a radially router blade portion and being substantially plane transversely to the turbine axis; said rotorrbody confining said blading by a concave portion h'av-v ing a relatively large radius of curvature adapting said blading to smoothly divert said motive fluid into the direction of said axis and pass it at a high velocity but under a lower pressure intoy said diffuser where the gas velocity is converted into a pressure approximating the pressure confronting the discharging gases.

4. In an overhung rotor turbine, particularly adapted for' gaseous motive fluids, such as hot gases, and discharging through a diffuser, a composite gas inlet casing having various individual supply conduits, at least part of said conduits at the entrance to said casin'g having a, component of extent'in the direction of the turbine axis and all of said conduits being crowded into an arrangement of closely spaced convolutions terminating in a nozzle arrangement having a limited number of tangentially directed inlet nozzles, and a' turbine rotor body carrying a blading arranged in said casing within said nozzle arrangement, the individual blades of said rotor 'body being substantially radiallyk directed along at least a radially outer blade portion and being substan tially Iplane transversely to the turbine axis, said rotor body confining said blading by a concave portion having a relatively large radius of curvature adapting said blading yto smoothly divert said motive fluid into the direction of said axis and pass it at a high velocity but under a lower pressure into said diffuser Where the gas velocity is converted into a pressure approximating the pressure confronting the discharging gases.

5. In an overhung rotor turbine, particularly adapated for gaseous motive fluids, such as hot gases, and discharging through a diffuser, a composite gas inlet lcasing having various individual supply conduits, at least part of said conduits at the entrance to said casing having a component of extent in the direction toward the turbine radius of curvature adapting said blading to.,

axis and all of said conduits being crowded into an arrangement of closely spaced convolutions terminating in a nozzle arrangement having a limited number lof tangentially directed inlet nozzles, and a turbine rotor body carrying ablading arranged in said casing within said nozzle arrangement, the individual blades of said rotor body being substantially radially directed along at least a radially outer blade portion and being substantially plane transversely to the turbine axis, said rotor body confining said blading by a concave portion having a relatively large radius of curvature adapting said blading to smoothly divert said motive-fluid into the direction of' lsaid axis and pass it at a high velocity but under a lower pressure into said diffuser where th'e gas' velocity is converted into al pressure approximating the pressure .confronting the discharging gases.

ALFRED Bcrm