US2286522A - Centrifugal compressor - Google Patents

Description

Jun 16, 1942. I M, WATSON 2,286,522

CENTRIFUGAL COMPRESSOR Filed April l3, 1940 v Sheets-Sheet 1 Ralph M. -Walson m N R ATTORNEY June '16; 1942.

R. M. WATSON GENTRIFUGAL COMPRESSOR Filed April 15, 1940 I 7 Sheets-Sheet 2 Ralph INVE ATTORN EY June16, 1942. R. M. WATSON 2,21%,522

GENTRIFUGAL COMPRESSOR Filed April 13, 1940 7 Sheets-Sheet 3 Ralph M. Watson IN ENTOR ATTORNEY June16,1942- R. M. WATSON 2,286,522

CENTRIFUGAL COMPRESSOR Filed April 13, 1940 I '7 Sheets-Sheet 4 Ra/pl? M Watson IN R ATTORNEY June 16, 1942. R. M. wA'rsoN CENTRIFUGAL COMPRESSOR Filed April 13, 1940 7 Sheets-Sheet 5 v I I June 16, 1942. R. M. WATSON 2,286,522

CENTRIFUGAL COMfRESSOR Filed April 15, 1940 7 Sheets-Sheet 6 Fig 6 I G a u Z' F157 9 2 j 2 v 65 Ralph M. Watson 2| 6.) IN R ATTORNEY CENTRIFUGAL COMPRESSOR Filed April 13, 1940 7 Sheets-Sheet '7 I Ralph M. Watson INVENTOR ATTORNEY Patented June 16, 1942 CENTRI'FUGAL COMPRESSOR Ralph M. Watson, Bloomfield, N. J., assignor to Worthington Pump and Machinery Corporation, Harrison, N. J., a corporation of Delaware Application April 13, 1940, Serial No. 329,498

9 Claims.

commonly in use, complicated and expensive mechanisms or structures are necessary due to the design of the compressors employed, for balancing the end thrust in the compressor and sealing the openings in the casing through which the driving shaft extends against the compressor pressures to prevent leakage of the refrigerant vapors to the atmosphere and leakage of air into the compressor.

An object of the present invention is to provide a centrifugal compressor in which volutes are employed, in connection with impellers ,arranged in a novel manner to provide a highly efficient, compact compressor in which any end thrust is substantially eliminated by balancing of the impellers in such manner that certain of them provide a counter-balancing end-:wise thrust against the end-wise thrust of the other impellers, thereby eliminating expensive and complicated thrust balancing means.

Another object of the invention is to provide a. centrifugal compressor in which the impellers are arranged whereby the seals or packing at the openings in the casing through which the shaft pressor of the preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings: Figpre 1 is a side elevation of the improved centrifugal compressor. I

Figure 2 is'a top plan view of the compressor. Figure 3 is an end view of the compressor looking toward the suction or inlet end.

Figure 4 is a longitudinal section through the compressor taken on the line 44 of Figure 2. Figure 5 is a cross-section of the compressor taken on line 55 of .Figure 4.

Figure 6 a vertical cross-section through the'suction inlet of the compressor taken approximately on the line 6-6 of Figure 4.

Figure 7 is a' horizontal longitudinal section through the compressor casing alone, showing the volutes and passages, taken on the line of Figure '3.

Figure 8 is a vertical cross-section through the final discharge volute of the compressor taken approximately on the line 88 of Figure 4.

Figure 9 is an enlarged view, in section, of

a portion of the compressorshowing the casing bushing. I

discharge volute in lieu of the general practice of employing diffusion vanes in the discharge passage of the compressor with the result that extends are subjected to pressures below the disleakage of vapor or gas'through the shaft bearings and to provide a lubricating system embodying a plurality of chambers under various degrees of pressure in the return line of the lubricant from the bearings to the circulating oil pump so as to separate the entrained refrigerant from the oil.

With these and other objects in view, as may appear from the accompanying specification, the v invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a centrifugal comthe efliciency of the compressor is materially.

increased and frictional losses diminished. The compressor comprises a horizontally split casing l0, through the axis of which extends the driving shaft H. The driving end of the shaft H may be connected by any approved type of coupling l2 with any approved type of prime mover. The shaft ll carries the various impellers of the centrifugal compressor,the number of which and consequently the number of stages of the compressor depends entirely upon the conditions of the installation in which the compressor is to be incorporated and the work to be performed by the compressor.

In the presentapplication a three stage compressor isillu'strated, but it is to be understood that the principles of the invention as set out in the claims are equally applicable to centrifugal compressors, regardless of the number of passage l4 has a butterfly valve or damper I5 therein, by. means of which the active, vapor passing cross-sectional area of the passage l4 may be regulated. This butterfly valve l5 may be operated by any suitable mechanism. A hand wheel operated gear and pinion structure is shown in Figures 1 and 3 of the drawings, in which the gear I5 is rotated by the pinion IS. The pinion I6 is in turn rotated by a hand wheel H. The gear I5 is mounted upon or suitably connected to the carrying shaft l8 of the valve l5. The inlet passage l4 curves upwardly and laterally into the suction or inlet eye 20 of the first or suction stage impeller 2|.

The inlet passage H is partially bifurcated by means of dividing vapor-directing ribs 22 and 23, the latter of which is substantially an inwardly extending projection of the uppermost portion of the side wall of the inlet passage where the two side sections or portions meet, as clearly shown in Figure 6 of the drawings. This particular construction of the suction inlet passage facilitates the distribution of the refrigerant vapors in the suction or inlet eye of the first stage impeller 2| and suppresses the creation of eddies and vacuous pockets in the inlet passage. By particular reference to Figures 4 and 6 of the drawings it will be noted that the inlet passage l4 curves in a smooth curvature in all directions towards the inlet eye 2l|.

The first stage impeller 2| of the compressor discharges into a double or twin volute 30 formed of the two volute passages 3| and 32, clearly shown in Figures 4 and 5 of the drawings. The defining walls 33 of the double volute passages curve circumferentially and laterally into the suction passage 34, which opens into the inlet or suction eye 35 of the second stage impeller 35.

The provision of the double or twin volute 30 decreases the machine dimensipns and balances any radial thrust which would-arise in the first stage of the compressor due to operation at conditions other than those for which the specific compressor was designed. This provision of the twin or double volute, together with the staggered arrangement of the volutes of the remaining stages of the compressor, will approximately take care of or balance any radial thrust which may occur in the entire compressor during off standard operating conditions.

The second stage impeller 36 discharges into a single volute 31, which is connected by a suitable passage to the suction eye 38 of the third stage impeller 39. The passage which connects the discharge volute 31 of the second stage impeller 36 to the third stage impeller 39 is shown in the drawings as comprising the nozzles 40 and ll, which are formed on the casing of the compressor and are connected by a U-coupling 42. The U-coupling 42 has a connection formed thereon which opens into the passage 44, which establishes communication between the second and third stage impellers so as to permit the introduction of vapors into an intermediate stage of the compressor. While the coupling 43 is shown arranged to permit the introduction of vapor into the third stage of the compressor, it is to be understood that such a connection may be connected. at any suitable point to the casing of the compressor to permit the introduction of vapor into any one of the stages of the compressor following the first stage. The third stage impeller 39, which in the construction shown in the By utilizing volutes at the discharge of the various stages in lieu of difluser vane structures, and by the various construction of cross-over connecting passages between the stages, a compact, relatively inexpensive centrifugal compressor may be provided in which the various 1mpeller stages may be arranged to effect an approximate balance in the compressor, thereby eliminating the need of employing expensive and relatively complicated end thrust balancing mechanism.

In the drawings, wherein a three stage compressor is shown, it will be noted that the first two stages, that is the impellers-2| and 35, are disposed in a parallel pair, with the back of the first stage impeller 2i facing the suction of the second stage impeller 36. Thus the combined end thrust of these two stages will be toward the right (Fig. 4), while the impeller 39 of the third stage of the compressor is disposed in a direction opposite to that of the impellers 2| and 36, with its back facing the back of the second stage impeller 36. Consequently the end thrust of the third stage impeller 33 will be toward the left (Fig. 4) and in an opposite direction to the end thrust of the impellers 2| and 36. Since impeller 39 is the highest pressure impeller and the end thrust produced by this impeller" will be substantially equal to the end thrust produced by impellers 2| and 36, counterbalancing end thrusts are set up in opposite directions in the compressor which will approximately balance each other and. permit the use of a-simple, inexpensive thrust balancing bearing as shown at 51 in absolute discharge pressure of each stage bearing a substantially constant ratio to its inlet pressure, and by reference to Figure 4 of the drawings it will be noted that the successive stages of compression in the compressor decrease in volu-' metric capacity. That is, the secondstage impeller 35, whilebeing of substantially the same,

diameter as the first stage impeller 2|, is narrower and consequently. has less volumetric capacity than the first stage impeller, while the third stage impeller 39, which is also of substantially'rthe same diameter as the impeller 2| and 36; is narrower than the impeller 35 and consequently has less volumetric capacity.

While the drawings show a three stage compressor with the impellers arranged as above specifically described, it is to be understood that the essence of this balancnig feature of the present invention comprises the arranging of the impellers in a multi-stage compressor in such a manner that the stages are divided, each set disposed in the opposite direction to the other set, creating end thrust substantially equal to the end thrust created by the impellers of the other set, for the purpose of counterbalancing end thrust in the compressor.

Centrifugal compressors of the type above de-. scribed and illustrated in the drawings, when used or employed in refrigeration or air conditioning systems generally receive the vapor or refrigerant gases into the first stage suction at a pressure of approximately seven pounds (7 lbs.) below atmosphere. The third or final stage of the compressor receives the vapor into its suction at a pressure slightly above or below atmosphere,

for instance atmosphere plus or minus three aagataa h,

pounds (3 lbs). Thus it will be seen that the opposite ends 01; the interior of the casing it; will be subjected tosubatmospheric pressureja initial inlet end of the casing and'to approxl mately atmospheric pressure at the other end of' the casing, that is, the end adjacent tothe dr ing end of the shaf-t'l I. It is desirable; er course,

to prevent leakage of air into the compressor easel ing, and also to prevent the leakage of 'val ablet refrigerant vapors from the compressor Therefore the present coninto atmosphere.

struction embodies means for efiectivel'ys'ealing l the openings in the ends oithe which the shaft Ii extends.

In the present invention sealing of these casing through c ings is effected during the operation'of the compressor through a combination enclose-fitting bearings for the shaft and the lubricating 'sys:

tem for such bearings, while a special mechanism I is provided for sealing the casing when the-come pressor is idle.

Due to the arrangement of the" impellers in the compressor as above specifically described, not

only is end thrust in the compressor approxi mately counterbalanced, but the'arrangemnt also provides that the shaft opening at the initial suction end of the compressor is'subjecte'd to the pressure of the vapor at the initial inlet, while the shaft opening 5| at the oppositeend of the casing is subjected to the-suction'pres'si re of the vapor at the third stage suction. There fore neither of these openings will be subjected to the highest'pressure developed ii the com pressor, which factmaterially' simplifies and'preduces the cost of the mechanismforsealingisuch openings in that, for one-thing,[itreduc es the pressure of the lubricating oil.

An oil reservoir 52 is provided in which 'z'in oi l pump 53, of any approved construction; is

mounted. The oil pump- 53 is driven fro m shaft ll through a coupling structure '54, shaft 55 and suitable transmission 56, which in the present instance is shown as beveled gears."

At the initial suction end of the compressor-a bearing structure 51 is provided which is carried by the casing l0 and which hassuitableloil' ducts-" 58 extending radially t-herethrough. to -lubricatej;

the bearing. Oil is supplied to the ducts :58 from an oil inlet line 59 which receivesttheuoiifrom the discharge end of an oil cooler 60,. The oil is pumped by the pump 53 througha suitable piping system 6! into and through the --cooler. ,60. Pressure regulating valves 62 of anyapproved;

type or construction may be connectedinhthefl pipe line 6! for the purpose of regulating the pressure of, the oil if it is desired. a The. oilpasses through the bearingil in both directionsand;

that which passes through thebearinginwardlys toward the compressor passes intoachamber 63 I and returns through a drain opening eor drain openings 64 through the bearing into the chamber 65. The oil which passes through-the bearing outwardly or away from the casing- Hipassesinto the chamber 65 and from this chamber "v drains into the reservoir 52. The chamber '65 is under a subatmospheric pressure. That-is, it; under the pressure of the vapor aswit enters the I initial inlet of the compressor. A stationary bushing 66 is mounted about the shaft Il,be

tween the bearing 51 and theim'peller 2|. Y This .pheric"pres'sure. *Oil is delivered to the-in .ter'n Bil-back to the reservoir 52."

formed therein with which a drainopening 69 communicates- The drain" opening leads bee]; 'to the chamber 63 'so 'that"z'ajn'y oil which would pass through 'the" bushing- 56 into: the chamber '68 wouldbe'draine'd back eventually intoth'e reser Kt theleppositeend o fth'e' casing 'lllfr'orn the bearing 5" a-se'cond bearing "HI for the'shaft' H"? is provided; While the particular construction 'of thebearing and its companion parts which form" the seal for the casing ID are the subject matter" of Patent No. 2,254,862 issued September 2, 1941-,: the structu're'wi'll,jbespecitically described hereinf toestablish 'i'ts'actionf andcooperation the general combination is the'comnresser.

a The" bearing ro lsa tight fitting bearing a d 1 since the mach-indie: this typei the shaft fre quently getsslig'htly outof alignment due various causes such? as] whip theshaf t when rotating athigh 'speeds', means 'are provided to n b e a i iiuesiso as torO- vide an"effective"seal for theshaft opening in th casing. '1' The bearing is 'cohrie'cted to thepas I 1 mg m by a flexible disc"II. "'1hisf-disc made 1 of strong, flexible metal sothat twninex d ring;

:shaft to preservegthe seal jan'd-to; prevent V exce'ss'f wear onthe bearing. Thes haft opening .51 opens intoa chamber 1.2, into which the inner end of the bearing Ill also extends, while'theoiiterf of "the bearing" extends into'a'chamber 1 3 The teha'mber "is subjected to'a'pres'sure'of apprexi? mat'ely atmosphere; that i'sj'a' pressure slightly above' orbelow atmosphere, namely the suction pressure'of thevapor atthe'inlct of the impeller: 39; while 'the chamber 13"is'subjectedto atmo ofthe bearing 10' intermediate its enqs rem ,th" jfl oil-inlet line 14 through a suitablefconnection15; f The inlet line 14 receives oil fronr t he o'utletiendf J of the oil cooler 60'. 'Theoil'passesiongitudiiially"e I fm i t e bearing i (bl t d r io s; r of t. passing into the 'chamber '12 from which it drains,

through" suitabledrain outlets 1T; "ai'i Ri e con f nections :18 to =a'"collecti'on "che'n'nberjl9; Fr'o m'fQ thatchan'iber'lil the oil'returns'to thejres'e ryoir 5152 through the pipe'system" 80. The oil whichg' g flo'ws outwardly through' thej bearingfint o th e chamber -'l3"passes through suitable drain open-.4" ingjs 8| into the collection chamber '82", from which it-passe's through the collection piping sysl- The interior of the oil chamber 52 is under th"\ ,2 'same pressure as the shaft 'open 1' ng 5 0, 'v'i'z .,"the. "v pressure of the vapor at the'initial'inletjto the compressor. By having'it under such relatively low pressure refrigerant which is carried thereto by the oil and is consequentlydeliveredto the" chamber at a pressure in excess of the "pressure therein-isreleas'edi h,

A bushing is positioned betweenthe charn-', Q

bBT 1.2 and the impeller" 39 ,"s imilar in its con; 1"

struction to the bushing 66, having a, plurality of annular grooves 84 spaced longitudinally along its bore, and is provided with an on collection chamber at from which oil drains through a suit 'a51e--arem 6 into the chamber 12 The b g .1

83' forms agd'amtd -hinder leakage of oiljinto the suction ofthe impeller 39. c E- e construction of, the bearing n'andthes lubrication of the: bearing in the menheeflebove described will effectively seal the opening 5| from both leakage of vapor out of the casing and leakage of air into the casing, during the operation of the compressor. But when the compressor is shut down the delivery of lubricating oil to the hearing will be stopped and consequently it is necessary to provide means to prevent either internal leakage of air or external leakage of vapor out of the casing through the opening 5| at such times. 7

The structure provided for this purpose in cludes a packing collar 90, which is of any suitable type of soft, resilient material not susceptible to objectionable corrosion or deterioration under action of the refrigerant vapor compressed. There are many substances of which this collar may be constructed, such as Neoprene and the like. This soft resilient packing collar 90 snugly fits about the shaft II and its in- -ner side near its periphery contacts an annular of the compressor the tension of the spring 98 is overcome by the pressure of oil from the lubricating system of the compressor, which is delivered to the interior of the bellows 91 through the connection 99, thus expanding the bellows and forcing the piston 96 outwardly, which moves the sleeve 93 outwardly, relieving the soft, resilient packing collar 90 of pressure from the sleeve 93. When'the compressor is stopped and consequently the pressure of oil in the bellows 91 is relieved, the spring 98 will move the piston 96 inwardly and through the medium of the lever 94 force the sleeve 93 inwardly against the collar 90, tightly squeezing the collar againstthe shaft to form a tight seal about the shaft. For the purpose of insuring the movement of the packing collar 90 into a pressure relieved position during the operation of the compressor, a follower I0! is mounted about the shaft II and engages the inner side of the collar 90 inwardly of the shoulder 9|. A spring I02 engages the follower I01 for urging it outwardly thus moving the collar 90 out of tight sealing engagement with the shaft when the collar is relieved of pressure of the sleeve 93.

A dish-shaped slinger I03 is mounted on the shaft H for rotation therewith,between the collar 90 and the bearing 10, and in the chamber 13. This dish-shaped slinger I03 is provided for throwing oil away from the shaft li so as to preventoil from leaking along the shaft to the collar 90. v

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a multi-stage centrifugal machine for compressing gas or vapor, a casing, three stage impellers in said casing, the first and second stage impellers arranged in'a set with their discharge sides facing the discharge side of the third stage impeller and having combined discharge pressures approximately equal to the discharge pressure of the third stage.

compressing gas or vapor, a casing, three stage impellers in said casing, the first and second stage impellers arranged in a set with their discharge sides facing the discharge side of the third stage impeller and having combined discharge pressures slightly greater than the discharge pressure of the third stage impeller to substantially balance end thrust by leaving a small unbalance of end thrust to avoid reversal of thrust during operation.

3. In a multi-stage centrifugal machine for compressing gas or-vapor, a casing, three stage impellers in said casing, the first and second stage impellers arranged in a set with their discharge s ides facing the discharge side of the third stage impeller and having combined discharge pressures approximately equal to the discharge pressure of the third stage, said first stage impeller having a twin volute casing with thetwo throat sections thereof disposed approximately apart, the second and third stage impellers each having a single volute casing, said single, volute casings being angularly disposed with their throat sections arranged relative to each other so that the side thrusts of one volute are counterbalanced by the side thrusts of the other volute.

4. In a multi-stage centrifugal machine for compressing gas or vapor, a casing, three stage impellers in said casing,the first and second stage impellers arranged in a set with their discharge sides facing the discharge side of the third stage impeller and having combined discharge pressures approximately equal to the discharge pressure of the third stage, said first stage impeller having a twin volute'casing with the two throat sections thereof disposed approximately 180 apart, the second and third stage impellers each having a single volute casing, said single volute casings being angularly disposed with their throat sections arranged relative to each other so that the side thrusts of one volute are counterbalanced by the side thrusts of the other .volute, said second andthird stage impellers being disposed back-to-back and in close relation to each other whereby the side thrusts of the two volutes are approximately in the same plane.

5. In a multi-stage centrifugal machine for compressing gas or vapor wherein the pressure of material compressed increases in geometric proes's fln m stage'to stage with the absolute proximately equalize the end thrust of the impellers.

6. In a multi-stage centrifugal machine for compressing gas or vapor wherein the pressure of material compressed increases in geometric progression from stage to stage with the absolute discharge pressure of each stage bearing a substantially constant ratio to its inlet pressure, a casing, a plurality of impellers of substantially equal diameter in said casing, said impellers arranged in sets of unequal numbers of impellers with the impellers in each set constituting successive stages of compression and with the impellersin one set disposed in back to back relation with the impellers of the other set and with the total absolute discharge pressure of one set being slightly greater than the total absolute discharge pressure of the other set to substantially balance end thrust but leaving a small unbalance of end thrust to avoid reversal of thrust during operation.

'7. In a muiti-stage centrifugal machine for compressing gas or vapor, a casing, three stage impellers in said casing, the first and second stage impellers arranged in a set with their discharge sides facing the discharge side of the third stage impeller and having combined discharge pressure approximately equal to the discharge pressure of the third stage, the discharge stage and oneother of the stages of the compressor being provided with single discharge volutes arranged relative to each other to balance .side thrusts oi the said stages, the remaining stage 01' said compressor being provided with a twin discharge volute with the two throat sections thereof disposed relative to each other to balance the 7 side thrust of said stage of the compressor.

8. In a multi-stage centrifugal machine for compressing gas or vapor wherein the pressure of fluid compressed increases in geometric progression from stage to stage with the absolute discharge pressure of each stage bearing a substantially constant ratio to its inlet pressure,acasing, a plurality of stage impellers in said casing, said impellers having progressively decreased volumetric capacity from the inlet stage to the final discharge stage. said impellers arranged in sets of unequal numbers of impellers with the impellers in each set constituting successive stages of compression, the impellers of one set. having combined discharge pressures approximately equal to the combined discharge pressures oi. the other set and arranged to substantially balance end thrust during operation 01' the compressor.

9. In a multi-stage centrifugal machine for compressing gas or vapor wherein the pressure of fluid compressed increases ingeometric progression from stage to stage with the absolute discharge pressure of each stage bearing a substantially constant ratio to its inlet pressure, .a casing, a plurality 'of stage impellers in said casing, said impellers having progressively decreased volumetric capacity from theinlet stage to the final discharge stage, said impellers arranged in sets of unequal numbersot impellers with the impellers in each set constituting successive stages of compression, the impellers of one set having combined discharge pressures approximately equal to the combined discharge pressures ofthe other set and arranged to substantially balance end thrust during operation of the compressor. one of said stages of the larger volumetric capacity having a twin discharge volute, and the remaining stages being provided with single discharge voiutes arranged relative to each other to balance side thrusts of the stages. I

RALPH M. WATSON. I

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