US1097729A - Centrifugal air-compressor. - Google Patents

Description

R. H. RICE. GBNTRIFUGAL AIR COMPRESSOR.

APPLICATION FILED 001 .21, 1911.

1,097,729. Patented May 26,1914.

v 3 SHEETS-SHEET 1.

Fig Hm x i I ff/ Witnesses: Inventor;

- Richard 'H. Rice, 4g? by aqttiy.

R. H. RICE.

GENTRIFUGAL AIR COMPRESSOR.

APPLICATION rum) OUT. 21, 1911.

Patented May 26, 1914.

3 SHEETSSHEET 2.

Inventor? Rlchar'd -H. FQice.

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R. 11.3103 GENTRIFUGAL AIR COMPRESSOR.

APPLICATION TILED OCT. 21, 1911.

Patented ma 26; 1914.

3 SHEETS-SHEET 3.

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Witnesss:

nventor;

ichard H. Rice,

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UNITED STATES PATENT ornion.

RICHARD H. RICE,

0F LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC GOMPANY, A CORPORATION OF NEW YORK.

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Specification of Letters Patent.

Patented May 26, 1914.

Application filed October 21, 1911. Serial N 0. 655,909.

1 0 all whom it may concern:

Be it known that I RICHARD H. RICE, a citizen of the United States, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Centrifugal Air-Compressors, of which the following is a specification.

The present invention relates to centrifugal air compressors andlias for its object to improve their construction.

My improvements are directed-chiefly to the construction of the impellers and tothe means for securing theni -.on the shaft, whereby they are rendered capable of withstanding high centrifugal stresses; to the construction of the impeller, guide-orinle't and discharge vanes; to the balancing arrangen1ents, and to certain details of construction to be referred tolater.

- In the accompanying, drawings, which are illustrative ofmy invention, Figure 1 is a partial axial section of amulti-stage centrifugal air compressor; Fig. 2 is a partial transverse section on a lar er scale, showing the relation of the impeller vanes to the stationary discharge vanes; Fig. 3 is a detail view showing the rotary ruide vanes in side elevation; Fig- 4 is a, lan yiew of these vanes; 5 is. a partial axial View of an impeller showing the means for securing it to the shaft; Fig. 6 is an enlarged sectional view sl'iowing the joint between the parts of the impeller body, and Fig, 7 is a detail view showing the elastic end portion of :1

Referring Fig. 1,110 indicates the easing of the compressor which is divided into an upper and lowerpart, said parts being suitably bolted. together in. an axial plane. 11 indicates the head of .the casing on the inlet end. Formed integral with the head is an inlet conduit 12 of suitable proportions for conveying air to the firstimpeller. 13 indicates the driving. shaft upon which the impellers are inounted. Closely surrounding the shaft. is an annular member 14 that forms .a continuation of the inlet conduit. This member is divided into upper and lower pa-rts'and permits the removal ofthe head 11 without disturbing the shaft cou- Qa-Which is inclos'ed, in the guard or liouslng 15. In this connection it should be noted that the diameter of the bore of the head is greater than the diameter of the coupling inclosed by the guard or housing 15. The guard is made of sheet metal formed into a cylinder and fastened by the strips 16. The guard as a whole is supported by a shouldercdring 17 that is attached to a flange on the head 11. I may employ some or all of the same bolts for securing-this ring that are used to unite the heada'nd the annular casting 14. Located within the casing are diaphragms 18, seated in suitable shouldelfis such as 19, formed on the inside of the casing. The diaphragms are provided with opposed shoulders 20 to receive the plates 21 and 22, between which are secured the curved dis: charge vanes. 23, to be referred to later. The diaphragms are also provided with chambers241 and .25 through which cooling waternia-y be circulated. Mounted on the shaft and in line with each set of discharge vanes, is a rotary impeller 26. This impjeller is provided with vanes 27 and 28 located on opposite sides of the body, which vanes are strictly radial. The impeller is also provided with inlet or guide vanes 29 and 30 that direct the incoming air currents. Air is supplied to opposite sides of the i eller' by the inlet 12 and other passa'ge'sriirmed in the diaphragm. Air is discharged by the impeller with considerable velocity and under a certain amountof pressure dueto centrifugal force. The air thus discharged is received by the discharge vanes which, as shownin Fig. 2, form passages that diverge from their inlet toward their outlet ends. By reason of the divergence of the fluid passages between the vanes, the velocity acquired by the air in the impeller is reduced and the pressure increased, which pressure is added tothat imparted by the vanes due to centrifugal action, Air on leaving the discharge vanes passes into the pressure chamber 31, where the air divides as indicated by the arrows, a part flowing by passage 32 to one side of the next impeller, and a part by passage 33 to the opposite side of said next'impeller. Each succeeding impeller and its discharge vanes acting in the manner aforesaid, inparts vadditional pressure to the airuntil the requisite pressure is obtained when it is discharged by a suitable outlet conduit resembling in appearance, the inlet 12, but smaller in cross-section, because the volume of air has been decreased as its pressure was increased. 7

Referring 'now to Figs. 1 and 2, it will be seen that the discharge vanes 23 are made of heavy sheet stock, and are U shaped in cross-section. The down turned sides of each vane are united by bolts, screws or rivets 34 to the side plates 21 and 22, as is shown in Fig. 1. The side portions of one vane follow at their edges the shape of the adjacent vane, and preferably rest on said vane so as to form good passages and also for supporting purposes. It will be observed that the main body portion of each vane forms a curve, the end of which is substantially tangential to the bore of the side plates 21, 22.

Also that the separation between said bodies increases toward the surrounding pressure chamber 31. In order to stiffen the discharge vanes at their inlet ends, rivets 35 are provided having suitable shoulders or spacing means to preserve the proper separation between the vanes at this point. By making the vanes in the manner described, they can readily be made to conform to the i required dimensions from heavy sheet stock.

The centrifugal stresses in an impeller are very high, and owing to this fact it is a difficult problem to make one which will not burst at'high speed, or the vanes foldover due to centrifugal stresses, or to stretch and become loose on the shaft. To meet the problem presented, I divide the impeller into two parts, which are afterward united by suitable securing means. Each half is provided with a plurality of integral blades 36 that occupy strictly radial positions with respect to the shaft axis. The body is preferably made of a steel casting and sufficient stock is left at all points for machining. By

suitable machine operations, the blades are cut to the required dimensions and the portion of the body 37 between the vanes is made as smooth as possible, also by suitable machine operations. The two parts of the impeller body are finished on their opposed faces as shown in Fig. 5. The parts are also shouldered to insure proper fitting. The

shoulder 38 between the parts is tapered as indicated in exaggerated manner in Fig. 6. In assembling these parts, the female member of the impeller is heated to cause expansion, and it is then assembled in place and as it shrinks it will firmly grasp the shouldered projection on the male member. The parts of the impeller are then united by suitable bolts such as 39, indicated in dotted lines. ,On the periphery of the impeller the two members are united by rivets. Such an impeller has the advantage of possessing very great strength and hence is capable of being rotated at high speeds. By making the impeller in two parts the loss due to imperfect castings is reduced, and if one side is injured in any way it does not necessitate a complete new impeller thereby resulting in a saving,

In order to obtain the highest efficiency in a compressor, the air should be directed into the channels or passages between the impeller vanes at the proper angle, and for this purpose curved inlet or guide vanes 29 and 30 are provided which rotate with the impeller. These vanes are carried by a cast metal support 41 which is slipped over the hub portion of the impeller body. "Each of these vanes is provided with a pair of bosses 42 which engage opposite sides of an impeller vane and prevent the outer ends thereof from moving out of their proper position. By forming these inlet vanes separate from the main impeller vanes, I am able to machine the impeller vanes without difficulty and no trouble is experienced in machining and properly shaping the inlet vanes, owing to the fact that they are relatively small, and the space between them sufliciently wide to permit of inserting the proper tool for finishing. It will be-observed that these inlet vanes are so shaped that they are strictly radial and hence all the stresses due to centrifugal force are radial. This means that there is no tendency for them to fold over, as would be the case if any portion of the metal forming them extended across a radial plane. The vanes are inclined at their receiving ends as shown in Figs. 2 and 4 so that they will receive the air as it enters inv a substantially axial direction and direct it into the radial passages between the main vanes on the impeller. Without these inlet vanes the main vanes 36 are much less efiicient in action. It will be noted-that a small clearance space or relief 41 is provided between the hub and the annular support 41 for a portion of its length. ,Thisis necessary in order to utilize the elastic feature of the ends of the hub. The support 41 carrying the inlet vanes is slipped over the hub 43 of the impeller, and is secured in place by a locking ring'44, Fig. 3.. This ring is provided with an internal shoulder 45 that is seated in a groove formed in the hub. In assembling the parts the support is mounted in place and the ring 44 is then heated and shrunk on the hub. The shoulder 45 in Fig. 3 has been exaggerated for the purpose of illustration. In actual practice a shoulder that is six or seven thousandths of an inch in depth will be sufficient.

Referring to Fig. 5, the means for securing the impellers on the shaft will be described. In the operation of centrifugal compressors at high speed, the metal forming the impeller stretches a certain limited amount when the machine is operating at full speed and unless special 'means are provided for securing the impeller to the shaft the former will get loose on the latter and cause trouble. It sometimes happens also in a high speed air compressor that the shaft whips.

By that is meant, that the shaft bends to a rusting metal of high crushing stress. The

grooves are slightly dove-tailed and the rings are rolled into the grooves under high pressure, which forces the metal under the overhanging Walls of the groove. After the rings are forced in place, they are subsequently machined to the exact predetermined internal diameter. The impellers are then forced endwise on the shaft under pressure and are prevented from rotating by the key 48 as are also the compression rings at. In the form of my invention illustrated, the diameter of the bore of the rings a? is .012 inches smaller in diameter than the portions of the shaft 13, arranged to engage therewith. This means that the metal in the rings and in the adjacent parts of the impeller body is under considerable compression. As a general proposition, it may be stated that the body of the impeller should be so fitted to the shaft that the stretch thereof, when running, does not equal the compression stress.

The 'compressor illustrated is intended to deliver 44:,000 cubic feet of air at a maximum rating of 30 pounds per square inch. The shaft is intended to rotate at 3600 R. P. M. Under operating conditions the stresses on the impeller may rise to 30,000 pounds per square inch. These figures are given as illustrations and'not as limitations of my invention since it is capable of wide application.

Mounted on the shaft are sleeves a9 made of some nonrusting metal. These sleeves are fitted inside of the ends-of the hubs of the impeller. The bore of the hub in the present illustration is .002 of an inch in diameter smaller than the externai diameter of the sleeve, and therefore forms a conipression fit. Surrounding the end of the hub is the shrink ring as previously referred. to in connection with Fig. This ring in addition to preventing the inlet vanes from moving axially on the impeller, serves to hold down the stretching effect of the end of the hub. To obtain the best effects, T find that this ring should be mounted on the hub with a two to four thousandths fit. These figures are, however, to be taken as illustrations and not limitations of my invention.

,@wing to the fact that the shaft may whip or be slightly deflected when in operation, it becomes highly important to provide a means for securing the impeller to said shaft which is unafiected'by said deflections. When a shaft is deflected, the outermost fibers of the shaft considered in the direction in which the bending has taken place elongate While the innermost fibers, those on the opposite side of the shaft contract. As a result. of this elongation and contraction of the fibers, the shaft tends to move axially in the ends of the hub of the impellermounted thereon; In order to permit this movement to take place without constraint ofthe shaft, it is necessary to have approximately a sliding fit between the impeller and the shaft. To this end the hub is slotted at 50 so that in effect a ring 50 is formed, which ring is connected to the hub proper. By reason of the slots 50, the ring 50 is relieved of tangential stresses so that its diameterwill not be perceptibly increased by the action of centrifugal forces in the hub, but will retain, as nearly as possible, its original diameter, and thereby form a support with a constant degree of tightness on the shaft. The ring 50 is seated on the sleeve or bushing- 49 with a relatively easy fit which becomesa slidin fit as soon as the impeller runs at a predetermined speed. The slots as before pointed out permit: the ring 50 to retain as nearly as possible its original diameter and thus obtain the desired sliding fit. "If the'ring 50 were sub jected to all the stresses met with in the main hub of the impeller, it would greatly enlarge in diameter and could only have a sliding fit at one particular speed whioh'is obviously unsatisfactory for a variable speed machine. With my improved construction the sliding fit is maintained throughout the whole range of operative speeds of the impeller. In order to space the impellers on the shaft, cylindrical members 51 are provided that have internal shoulders which engage the sleeves 49, Fig. 5, and since the latter engage shoulders on the impellers, it follows that axial movement is prevented, providing the two end impellers on the shaft are properly anchored. The periphery of the cylindrical member 51 is provided with projections 52, that extend between the con responding projectionson the cylinder 53,. the latter being provided with an external shoulder as by means of which it is bolted to one of the diaphragms. The member 51 and the cylinder 53 and the opposedprojections thereon, form a labyrinth packing to preventthe passage of fluid from one chamber to another, along the shaft bore-.-

ln an apparatus of the character de scribed, the-question of the balance isa very important one. Tothis end each-of the impellers is balanced as carefullyas-possibis-before beingmounted on the shaft elther statically. or dynamically or both. To this end, metal may beadded to or taken away from one or more parts of the impeller as is required. It sometimes happens that where each of the impellers is perfectly balanced individually, when they are all assembled on the shaft, the machine as a whole will be out of balance. In order to permit of balancing the rotating element without taking ofl the top part of the casing when once the machine is assembled, openings are provided at opposite ends. In Fig. 1 the opening at the low pressure end is filled by the removable plug 55 and in Fig. ,5 the opening at the high pressure end is filled by the removable plug 56. By taking out these plugs access can be had to the body of the impeller, so that metal can be added thereto or taken away in the manner customarily followed in balancing apparatus of this kind.

I prefer to make the impeller body in two parts for the reasons before stated and therefore use two compression rings 47. As far as the means for supporting the impeller is concerned it might be made in one piece in which case one compression ring may be used. In this event it should be made wide enough to prevent crushing of the metal when assembled. When it is desired to use single sided impellers, z'. 6., those having vanes on one side only a single compression ring, such as 47, will usually suflice, the hub being elastic as before. When the impeller is made in two parts they should be made as nearly alike as possible.

My invention is directed chiefly to centrifugal air compressors but certain of its features may be utilized in centrifugal pumps and other apparatus having bodies rotating at high speed. In accordance with the provisions of the patent statutes, 1 have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can becarried out by other means.

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

1. An impeller comprising a body having a plurality of radial vanes and spaces between on eachside with rings of inlet vanes mounted on opposite sides of the impeller, said vanes .rotating with the impeller and directing the. incoming fluid into the vane spaces, the surfaces of the inlet vanes forming a continuation of the surfaces of the inner ends of the first vanes and being so shaped as to effect a gradual change in the direction of the fluid.

2. An impeller comprising a body having a plurality of radial vanes, vane spaces an a hub on each side, and a ring of radial vanes whose inner ends are at rlght angles to the axis of the impeller detachably mounted on each hub that engage the inner ends of the first vanes and direct the incoming fluid to the vane spaces.

3. An impeller comprising a body having a plurality of radially extending integral vanes with vane spaces between and a hub on each side, inlet vanes for each side of the impeller that form a continuation of the inner ends of the radial vanes and gradually change the direction of the entering fluid from an axial direction and direct it into the radial vane spaces, a support for each set of vanes that is carried by one of the hubs, and means for uniting the inlet and the said radial vanes.

4. An impeller comprising a cast body portion with radially disposed vanes formed integral therewith, a plurality of curved inlet vanes that form a continuation of the inner ends of the radial vanes and receive fluid in an axial direction and direct it into the radial vane spaces, the said vanes being so disposed that the centrifugal stresses are exerted in a radial direction, and a separate support for the inlet vanes that rotates with said body.

5. An impeller comprising a cast body portion, radially disposed vanes formed integral with the body and located on opposite sides, hubs for the body thatextend on opposite sides thereof, rings of inlet vanes that cooperate with the main vanes to direct the incoming fluid, and supports for the vanes that are mounted on the hubs and rotate therewith.

6. An impeller comprising a body portion and vanes carried thereby, a hub forming a part of said body, inlet vanes, a support for the vanes that is seated on the hub, said hub being cut away for a portion of its length under the support to permit the hub to change its shape without affecting it, and a ring that embraces the end of the hub and holds the said support against axial movement.

7 An impeller comprising a body having a yieldinghub at its outer end with a shaft that passesthrough the impeller and makes a substantially rigid compression fit in the central portion of said body and also engages the hub with a-rela-tively easy fit so that the shaft may move relatively to the hub when said shaft bends or whips.

8. An impeller comprising a body and a hub at the outer end thereof with a shaft on which the impeller is mounted that makes a compression fit with the inner portion of the body and a sliding fit with the hub.

9. An impeller comprising a body whose bore is larger than the shaft, a compression member located in the bore of the body that makes a compression fit with the shaft, a

shaft for the impeller, and a means for supporting the body on the shaft which is located at one side of said member.

10-. An impeller comprising a body and a hub, a ring-like portion, a yielding means connecting said portion with the hub which limits the transmission of tangential stresses from the hub to said portion, and-a shaft that makes a tight fit with the hub and a sliding fit with said ring-like portion.

11. In combination, an impeller comprising a body portion and a hub whose ends are slightly elastic .with a shaft that engages and supports the impeller at the center and ends only.

12. In combination, an impeller comprising a body and a hub whose ends are slotted to prevent the transmission of stresses from the body thereto, a shaft that supports the impeller at the center and ends only, and means for securing the ends of the hub to the shaft.

13. In combination, an impeller comprising a body and a hub whose ends are slotted to prevent transmission of strains from the body thereto and to permit deflections of the shaft, a shaft that supports the impeller only at the center and both ends of the hub, the said impeller being fitted tighter at the center than at the ends of the hub.

14:. In combination, an impeller comprising a body and a hub, said hub containing an elastic portion, a shaft which is fitted to the impeller at the center and both ends only, the metal at the center of the impeller being under compression at all times while the ends are relatively free, and compression rings on the ends of the hub to limit the stretching effects thereof.

15. In combination, an impeller comprising a body and a hub whose ends are slotted, radial vanes on said body, inlet vanes for iding fluid to the radial vanes, supports for the inlet vanes that surround and en gage the slotted end of the hub, and compression rings that hold the supports in place and also limit the stretching eifect of the endsof the hub.

16. In combination, an impeller comprising a body and a hub extending on one side thereof which contains an elastic portion, radial vanes on the side of the body, inlet vanes, cooperating with the radial vanes, an independent support therefor, and a ring that holds the support on the hub and also limits its stretching effect.

17. In combination, an impeller comprising a two-part body with a shoulder between, one of said parts being shrunk on the other, means for securing the parts together at points outside of the shoulder, radial vanes on each part of the body and formed integral therewith, and separate inlet vanes which revolve with the body and direct fluid to the radial vanes.

18. An impeller comprising a body portion thatis made in two symmetrical parts with the plane of division between them perpendicular to the shaft, each of said parts being provided with a hub to receive a shaft and with integral radial vanes, means for securing the parts of body portion together, and curved inlet vanes carried by the hub that rotate with and form a continuation of the inner ends of the radial vanes.

19. In a multi-stage compressor, the combination of a casing, a-shaft, a plurality of impellers mounted thereon, each impeller comprising a plurality of radially arranged vanes provided with detachable fluid directing inlet vanes, spacers between the impellers that surround the shaft and are provided with peripheral projections, diaphragms in the casing for dividing it into impeller compartments, and an annular member carried by a diaphragm that surrounds the spacer and has internal projections that cooperate with those on the spacer to form a tortuous passage that acts as a packing to retard the flow of fluid from one compartment to another, there being a clean ance at all times between the projections on the spacer and the member to avoid rubbing contact.

20. In a compressor, the combination of a casing, an impeller located therein, a shaft, heads for closing the ends of the casing, and removable plugs in the heads and situated in line with the impeller to permit access thereto.

21. In a compressor, the combination of a casing, an impeller, a shaft, a detachable head for the casing that is provided with a fluid carrying conduit, and an annular mem-" her through which the shaft extends that is attached to the head and forms a art of said conduit, said member being divided in an axial plane.

In witness whereof, I have hereunto set 'my hand this nineteenth day of Uctober,

RICHARD II. RICE.

Witnesses:

JOHN A. MoMANUs, Jr., FRANK G. l-Li'rrm.

It is hereby certified that in Letters Patent No. 1,()97,7 29, granted May 26, 1914,

upon the application of Richard H. Rice, of Lynn, Massachusetts, for an improvement in Centrifugal Air-Compressors, an error appears requiring correction as follows: In the drawings, sheet 2, Figs. 2, 3, and 4, for the reference-nnmeral 40, wherever it appears, read 30; and that'the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 4th day of September, A. D. 1917.

[SEAL] R. F. W HITEHEAD,

Acting Commissioner of Patents. Cl. 23011.

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