US2282894A - Elastic fluid turbine - Google Patents

Description

May-L12, 1942. L. A. -sHELDoN 2,282,894

ELAsTIc FLUID'TRBINE Filed April 2, 1940 2 sheetsneet 1 May 12, '1942. 1,. A. sl-IELDQNy ELASTIG FLUID'mURINE 2 She Filed ,April 2, 1940 s-Sheet 2 Invento: L ,Llcjany A Shelclon,

' His Attorney.

` ment of elasticiiuid turbines.

Patented May 12, 1942 Ems'rlc FLUm TunBINE Lucian A. Sheldon, Schenectady, N. Y., assignor to General Electric Company, a corporation of New .Yorkv Application Apriiaimo, serial No. 327,381

(cl. 25a-e9) 4 Claims.

The present invention relates to elastic uid turbines and has for its general object the provision of an improved construction and arrange- A specific object of my invention is to provide an improved casing or shell construction whereby warpage due to high temperature changes is reduced to a minimum. Another object of my invention is to provide an improved arrangement to reduce leakage of elastic uid between successive stages of a multi-stage turbine. Still another object of my invention is to provide an improved shaft packing or sealing device to reduce leakage of elastic uid along the turbine shaft. A further object of my invention is to provide an improved construction and arrangement for centering a turbine diaphragm on a turbine casing. Y

For a consideration of further objects and of what I believe to be novel and my invention, attention is directed to the following description and the claims appended thereto in connection The turbine arrangement shown in the drawings is especially suited for operation with high temperature mercury vapor although it is not necessarily limited thereto. The arrangement Vcomprises a rotor having a shaft I with a plurality of successive bucket wheels II, I2, I3 and I4 securely fastened thereto; bucket wheels II and I4 form Dart of the rst and last turbine stages respectively. Elastic uid is supplied to the first stage bucket wheel II by meansincluding a conduit I5 centrally arranged with the turbine shaft and having a ared end portion surrounding a cap I6 to form therewith an annular channel I'l. Concentrically spaced rings I8Aand I9 are secured to the end portions of the cap I6 and the conduit I5 and in turn act as a support for a nozzle structure 20. This nozzle structure in the present instance extends over 360 annular degrees and thus constitutes a full admission arrangement for the first stage bucket Wheel II.

Elastic iiuid discharged from the first stage wheel Il during operation is conducted to the second stage wheel I2 by means of a diaphragm 2|. Similarly, iiuid discharged from the bucket wheels I2 and I3 is conducted to the succeeding bucket wheels by means of nozzle diaphragms 22 and 23 respectively. Each nozzle diaphragm comprises a disk 24, a row of circumferentially spaced radial blades 25 with inner ends secured to the disk and outer ends secured to a support on an outer ring 26. Blades 25 define the nozzle passages. Theinner portions of the stationary disks 24 are sealed tothe shaft by suitable means such as by labyrinth packings 21 to reduce leakage of elastic fluid from higher to lower stages along the shaft. The diaphragms 2|, 22, 23 may be split along a plane through the center of the shaft I0 to facilitate assembling and dismantling.'

The turbine casing, according to my invention, is composed of a plurality of rings 28, 29 and 30.` one ring for each diaphragm 2I, 22 and 23 respectively. The rings 28, 29 and 30 are secured together by means of rings of circumferentially spaced horizontal bolts 3l. The first ring 28 is secured by bolts to the aforementioned inlet ring I9 and the ring 30 is secured to an outlet ring 432 by horizontal bolts. The various rings of the casing have adjacent shouldered or recessed portions engaging and centering each other and assuring the maintenance of centered relationship during operation. ,The provision of a casing vmade of separate rings reduces the heat transfer from the inlet portion. of the casing toward its outlet portion and thereby reduces warping as compared with an integrally formed casing.

The diaphragms are supported and centered on the casing. To this end each of the casing rings28, 29 and 30 and the corresponding outer diaphragm rings 26 are connected by a plurality (at least 3) of circumferentially substantially uniformly spaced radial pins 33 slidably projecting into radial openings in the outer diaphragm rings 246 and the corresponding casing rings and prevented from outward movement by means of plugs l34 screwed into the openings of the rings 28, 29 and 30. During assembly the pins are inserted from the outside through the radial openings in the rings 28 to 30. The plugs 34 are preferably integral with the pins 33.to facilitate removal of the latter. These radial pins support the diaphragms and maintain concentric relation between them and the shaft. During operation the radial pin support permits relative expension between the diaphragms and the casings without causing the setting up of excessive stresses and at the same time maintains. concentric relation.

At least some of the outer diaphragmrings 26 have annular, conically-shaped projections 35 and 36 on opposite sides thereof. The projections 35 and 36 of adjacent rings are closelyV spaced In lcertain instances the elastic fluid as it leaves the rst stage already contains several percent by weight of moisture and it becomes desirable to provide such moisture-collecting grooves also with regard to the first stage. In the present instance a moisture-collecting chamber 99 for receiving moisture from the fluid discharged from the rst stage bucket wheel is formed by the' projection 95 of the ring 26 of the diaphragm 2| and a projection 39 of the inlet ring I9. A last stage moisture-collecting groove' or chamber 46 is formed by projections 4| and 42 of the casing ring 30 and the end ring 32 respectively to receive liquid particles contained in the fluid discharged from the last stage bucket wheel I4.

In order to reduce leakage oi' elastic fluid through the joints formed between the outer diaphragm rings 26 and the outer casing, means are provided for sealing the outer diaphragm rings 26 to the outer casing. In the present instance eachl of the outer diaphragm rings 26 is sealed to the corresponding casing ring 28, 29 and 30 by means of an annular sealing strip 43 which tion of the outer casing to .reduce temperature has an outer edge secured to the casing or casing V and 32 constitutes an inner casing or shell and is surrounded by an outer casing or shell 81. The outer casing l is fabric-ated and comprises a substantially, cylindrically-shaped outer wall of sheet metal A9 extending axially beyond the inlet ring I9 and secured at'its left-hand end to a y disk 49. An inner portion oi the disk 49 is fused to a heavy ring 50 which is secured by bolts 5| to another heavy/ring 52. The ring 52 is Welded to a cylindrical extension 53 of the inlet ring |9.

In order to prevent leakage of mercury vaporA along the bolts 5| these bolts are sealed by means of concentrically spaced cylinders 54 and 55 fused to the conduit i5 and the -ring 5|! respectively and having outer edges fused to a sealing strip 56.

The right-hand end ofthe outer wall .48 is secured to a comparatively heavy ring 51 which is fastened to another heavy ring 56 by bolts 59. The bolts 59 are sealed to the casing by a sealing strip 60. The ring 58 carries an end wall 6| which, has an outer .portion fused to the 'ring 56 and an inner portion fused to a packing casing 62. The packing casing 62 forms 'part of a packing more fully described hereinaften A lower portion of the outer casing is open and connected to an exhaust conduit 66 for conducting exhaust l drop across and warpage of the inner casing. The pressure maintained in the space between the inner and outer casing is the exhaust pressure of the turbine and the temperature in said vspace is that of the exhaust fluid. Thus, for example, in case of a mercury turbine operated with an inlet temperature of 1000 and an exhaust temperature of 450 the temperature of the huid between the inner and outer casing will be about 450. This means that the maximum temperature drop across the inner casing, more specifically across the inlet ring I9, will be of the order of about 550 which is about one-half of the temperature drop across both caslngs. Thus,

with the provision of a double shell arrangement the temperature drop may be divided up so that the temperature drop across the inner casing is approximately equal to the temperature drop across the outer casing with the space between the casings subject to the exhaust fluid from the last turbine stage. This is particularly important in the oase of mercury vapor operated turbines because of the high temperature at which mercury vapor is exhausted in such turbines. The reduced temperature drop across the inner casing and the provision of an inner casing made of a plurality of rings bolted together reduces considerably warpage of -the inner casing and permits the latter to be made of relatively light weight.

The shaft l0 carrying the turbine bucket wheels is supported on a suitable bearing 64 which may form part of an electric generator driven by the turbine and having a casing 65 suitably brazed on the outer turbine shell or casing. Thus, the bucket wheels in the present instance are secured to an overhung shaft portion I0 supported on the low pressure end by the bearing 64. The elimination of a bearing. for supporting the shaft near the high pressure end of a turbine permits the elimination of a special packing or sealing for the high pressure turbine end which is especially advantageous in the case of mercury vapor turbines.

The packing for sealing the wall 6|, that is, the low pressure end of the outer shell 41 to the shaft I0, as shown in Figs. 3 to 5, comprises the packing casing 62 which has a left-hand portion 65 and a right-hand portion 61 secured to opposite sides of a ring 68 by means of a plurality of bolts 69; the portion 66 is located inside the exhaust space of the turbine. I'he outer edge of the ring 68 is secured to the end wall 6| by a weld 68a. 'I'he casing as awhole is split along a horizontal plane through the center of rotation to form two halves joined together by means of a plurality of bolts 10. 'I'he shaft portion within the packing casing has two grooved sections, an

inner section 1| adjacent the exhaust end of the turbine and within the packing casing portion 66 and an outer grooved portion 12 facing away from the exhaust end and within the casing portion 61. The grooved portion 1| is in cooperative relation with a toothed packing ring 13 suitably supported on the packing casing portion 66 and having teeth in cooperative relation faces which may be formed by hardened metal inserts or covers. 'Ihe groove 19 is connected through a channel in the packing casing to. a conduit 8U for receiving mercury liquid during operation. The liquid thus supplied to the groove 19 forms a liquid seal between the groove' and the impeller 11. Part of the liquid continuously supplied during operation to the groove 19 is discharged therefrom towards the impeller 16 which acts as a guide and throws the liquid outward in the chamber 18. said chamber through a channel 8| in the ring 88 and a conduit 92 connected to the channel. Part of the liquid contained in the groove 19 flows along the labyrinth packing 14 towards a groove 83 formed by the casing portion 61 between the labyrinth packing rings 14, 15. The

groove 83 is connected to a discharge conduit 84. The outer end of the packing arrangement is further sealed by means 'of a packing ring such as a carbon ring 85 biased towards an end plate 86 and towards the shaft I8 by means of a helical spring 81. The end ring 86 is secured to the casing portion 61 by a plurality of bolts 88. The end ring 86 is made up of two halves joined and secured together by bolts 88a. v

During starting of the turbine a considerable amount of mercury is needed to produce a liquid seal between the shaft and the packing casing. For this reason a great amount of liquid is forced into the chamber 18 through the conduit or pipe 82 to flll the space 18 between the inner and outer grooved shaft portions 1| and 12. As soon as the shaft has reached vapproximately half speed the mercury liquid is supplied through the conduit 80 to the groove 19 to form a rotary liquid seal whereupon the supply through the conduit 82 is disconnected'and said conduit becomes a discharge or drain conduit.

With the provision of the outer grooved shaft section 12 and the labyrinth packing rings 14, 15 small particles of mercury leaking along the shaft are prevented from leaking into the atmosphere. In a preferred embodiment non-oxidizing gas, such as nitrogen, is admitted into the space 83 between the' outer labyrinth rings through a pipe 89 at a pressure slightly belowthat of the atmosphere. This gas is discharged from the space between the packing ring 15 and the carbon ring 85 through a pipe 90. The supply of gas maintains the` pressure between the outer labyrinth and the carbon ring to slightly below atmosphere, thus permitting always a slight inflow or leakage of air from the atmo'sphere into the space 89 to prevent any leakage of mercury into the atmosphere. Leakage of fluid along the adjacent surfaces of the casing portion 66 and the ring 68 flows into the exhaust space of the turbine. lLeakage of uid along the adjacent surfaces of the ring 68 and the casing portion 61 is prevented from flowing into the atmosphere by the provision of a sealing strip 9|l secured between the end wall 6| and the casing portion 61. Leakage of fluid into the space The liquid is discharged from,

formed bythe sealing strip 9| and the adjacent elements is drained through a pipe 92.

The arrangement also includes means to reduce leakage of fluid, particularly air from the atmosphere into the turbine, along the joint vformed between the lower and upper halves of the casing portion 61. To this end the joining surfaces of the lower-.and upper halves of these' casing portions are provided with grooves 93 and 94 extending from the outer surface of the casing portion 61 towards the annular groove 19. The grooves 93 and 94 in the present instance are formed in both the lower and upper halves of the casing portion 61. The outer ends of the grooves communicate with pipes 95 and 96 re'- spectively through which a continuous stream of mercury liquid is conducted to the groovesl 93 and 94 respectively during operation. With'this arrangement mercurygparticularly mercury va-- por, leaking along a joint formed between the lower and upper halves of the casing portion 61 in the direction of the arrow 91 indicated in Fig. 5 is collected or condensed in the grooves 93,

`94 and thereby prevented from reaching the outer end of the casing portion L61 and air from the atmosphere is prevented from leaking into the sealing arrangement. The pipes 95 and 96 are connected to the grooves 93 and 94 respectively by means of welds 98 which extend along the entire end portions of the joined casing portions 61 (Fig. 5). A sealing ring 99 is secured to the left-hand end portion of the packing casing and has an inner edge in close proximity to the shaft to prevent mercury liquid particles from being thrown from the packing towards the last stage bucket wheel.

Thus, apacking according to my invention includes a casing forming three axially spaced annular grooves or chambers, a rst groove 18, a second groove `19, and a third groove 83. The second or intermediate groove 19 accommodates an impeller 11 on the shaft. Sealing liquid supplied to the groove 19 during' operation forms an annular liquid seal between the impeller 11 and the surface of the groove 19. The rst groove or chamber 18 accommodates an impeller or deflector 16 to throw outward mercury liquid discharged from the groove 19 during operation,

`such liquid being drained from the groove or pointed out above, is preferably supplied at a pressure slightly below that of the atmosphere whereby a small amount of vaix` may be drawn into the packing casing along the carbon packing ring and the discharge of mercury liquid from the packing casing to the atmosphere is substantially entirely prevented.

The packing casing is made of two halves joined together along a horizontal plane through the axis of the shaft and the joint surfaces have sealing grooves for receiving mercury liquid during operation to prevent the leakage of vapor from the packing along the casing joint.

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

l. Elastic fluid turbine comprising an inner f casing composed of a plurality of rings bolted together, an outer casing enclosing the inner casing, a plurality of diaphragms each having an outer ring, a plurality. of circumferentially spaced radial pins securedto inner casing rings4 and slidably projecting into radial openings of the outer diaphragm rings for centering and supporting the diaphragms and permitting relative radial expansion between the diaphragms and the inner casing, the inner casing and the outer diaphragm rings forming annular grooves for receiving moisture from iiuid passing through the turbine, and sealing strips connected between corresponding outer diaphragm rings and inner casing rings to prevent iiuid from bypassing a diaphragm along the inner and disposed in said space with the legs of the U engaging said cylindrical surfaces and an outer edge fused to the casing and an inner edge fused to the diaphragm.

3. Elastic iiuid multi-stage-turbine comprising a casing having a plurality of rings of successively increasing diameter, separate bolting means for securing adjacent rings together, a plurality of diaphragms disposed within the casing, each diaphragm having an outer ring associated with and supported on a casing ring, the outer diaphragm rings having annular conically-shaped projections forming together with the casing annular grooves for receiving moisture from elastic uid passing through the turbine, the last stage casing rings having inner projections defining a groove for receiving moisture discharged from the last turbine stage, and sealing means for sealing each diaphragm to a casing ring.

4. Elastic fluid turbine comprising a casing with a plurality of axially spaced shoulders, a plurality of diaphragms disposed in the casing and each having a face engaging a shoulder and an outer surface defining an annular groove with the adjacent surface of the casing, and separate sealing means between each diaphragm and the casing, each sealing meansy comprising an annular strip U-shaped in cross-section located in the groove and having inner and outer edges fused to a diaphragm ring and the casing respectively.

LUCIAN A. SHELDON.

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