US2294143A - Centrifugal compressor - Google Patents

Description

Aug. 25, 1942. WATSON 2,294,143

CENTRIFUGAL commssson Original Filed April 13, 1940 4 sh98tS-Sh9t 1 Hal 711 M M51501;

INENTOR ATTORNEY R. M. WATSON 'mRIFueAL COMPRESSOR Original Filed April 13. 1940 4 Sheets-Sheet 2 ATTORNEY 8 1 R. M. WATSON CENTRIFUGAL COMPRESSQR Original Filed A ril 13, 1940 4 Sheets-Sheet 5 Ralph .M; Wazifim IN NTOR ATTORNEY 1942. R. M. WATSON CENTRIFUGAL COMPRESSOR Origin'al Filed April is, 1940 ATTORNEY 4Sheets-Sheet 4 Patented Aug. 25, 1942 CENTRIFUGAL COMPRESSOR Ralph M. Watson, Bloomfield, N.'J., assignor to Worthington Pump. and Machinery Corporation, Harrison, N. J., a corporation of Dela- Ware Original application April 13, 1940, Serial No. 329,498. Divided and this application April 2, 1942, Serial No. 437,405

7 Claims.

This invention relates to centrifugal gas or vapor compressors, and more particularly to a centrifugal compressor for use in refrigerating systems for handling a volatile liquid of low vapor pressure and high density, such for example as trichlorofluoromethane, methylene chloride or the like.

, An object of the present invention is to provide in a centrifugal compressor means for delivering lubricating oil to the bearings of the compressor at a pressure slightly in excess of the-pressure in the compressor at either end of the bearings at the shaft openings to prevent leakage 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.

The present application is a division of my ap- With these and other objects in view, as may appear from the accompanying specification, the 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 compressor of the preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

Figure 1 is a side elevation of the improved centrifugal compressor.

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 sectionthrough the compressor taken'on the line 4-4 of Figure 2.

The centrifugal compressor of the present invention utilizes the principle of impeller and discharge volute in lieu of the general practice of employing difiusion vanes in the discharge passage of the compressor with the result that the eillciency of the compressor is materially increased and frictional losses diminished. The,

compressor, comprises a horizontally split casing I0, through the axis of which extends the driving shaft II. The driving end of the shaft Il may be connected by any approved type of coupling I! with any approved type of prime mover.

The shaft It 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 plication Serial No. 329,498, filed April 13, 1940.

the installation in which the compressor is to be incorporated and the work to be performed by the compressor.

Referring specifically to the drawings, the easing I0 has a suction-or inlet connection I4 at one end thereof, through which the vapors to be compressed enter the compressor. The inlet passage It has a butterfly valve or damper i5 therein, by means of which the active, vapor'passing cross-sectional area of the passage Hi 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 l6. The pinion I6 is in turn rotated by a hand wheel ii. The gear I5 is mounted upon or suitably connected to the carrying shaft I8 of the valve IS. The inlet passage l4 curves upwardly and laterally into the suction or inlet eye 20 of the first or suction stage discharges into a double or twin volute 30 formed of the two volute passages 3i and 32, clearly shown in Figure 4 of the drawings. The defining v walls 33 of the double volute passages curve circumferentially and laterally into the suction passage 34, which opens into the inlet-or suction 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 careof or balance any radial thrust which .may occur in the entire compressor during off standard operating conditions. I

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 thirdstage impeller 39 is shown in the drawings as comprising the nozzles 40 and 4|,

which areformed on the casing IQ of the com pressor and are connected by a U-coupling 42. 1

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 drawings is the final stage, discharges through its volute 45 into a. discharge nozzle 46.

In the drawings, wherein a three stage compressor is shown, it will be noted that the first two stages, that is the impellers 2i and 36, are disposed in a parallel pair, with the back of the first stage impeller 2| facing the suction of the second stage impeller 36. Thus the combined endthrust 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 2i and 38, with its back facing the back of the second stage impeller 36. Consequently the end thrust of the third stage impeller 39 will be toward the left (Fig. 4) and in an opposite direction to the end thrust of the impellers 2i and 35. 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 2i 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 57 in Figure 4 of the drawings.

Centrifugal compressors of the type above described 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 pounds (3 lbs.). Thus it will be seen that the opposite ends of the interior of the casing ID will be subjected to subatmospheric pressure at the initial inlet end of the casing and to approximately atmospheric pressure at the other pressor through a combination of close fittingbearings for the shaft and the lubricating system for such bearings, while a special mechanism is provided for sealing the casing when the compressor is idle.

Due to the arrangement of the impellers in the compressor as above specifically described. not only is end thrust in the compressor approximately counterbalanced, but the arrangement also provides that the shaft opening at the initial suction end of the compressor is subjected to the pressure of the vapor at the initial inlet, while the shaft opening 5| at the opposite end of the casing is subjected to the suction pressure of the vaporatthe third stage suction.

Therefore neither of these openings will be subjected to the highest pressure developed in the compressor, which fact materially simplifies and reduces the cost of'the mechanism for sealing such'openings in that, for one thing, it reduces the pressure of the lubricating'oil.

An oil reservoir 52 is provided in which an oil pump 53, of any approved construction, is mounted. The oil pump 53 is driven from the shaft I! 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 5'! is provided which is carried by the casing in and which has suitable oil ducts 58 extending radially therethrough to lubricate the bearing. Oil is supplied to the ducts 58 from an oil inlet line 59 which receives the oil from the discharge end of an oil cooler 56. The oil is pumped by the pump 53 through a suitable piping system 6! into and through the cooler 60. Pressure regulating valves 62 of any approved type or construction may be connected in the pipe line 6| for the purpose of regulating the pressure of the oil if it is desired. The oil passes through the bearing 51 in both directions and that which passes through the bearing inwardly toward the compressor passes into a chamber 63 and returns through a drain opening or drain openings 64 through the hearing into the chamber 65. 1 The oil which passes through the bearing outwardly or away from the casing l0 passes into the chamber 65 and from this chamber drains into the reservoir 52. .The chamber 65 is under a subatmospheric pressure. That is, it is under the pressure of the vapor as it enters the initial inlet of the compressor. A stationary bushing 66 is mounted about the shaft ll between the bearing 51 and the impeller 2i.

This bushing has its inner surface provided with a, plurality of longitudinally spaced circumferential grooves, as shown at 61, and it prevents creeping of oil along the shaft into the compressor. The bushing 66 has an oil collection chamber 68 formed therein with which a drain opening 69 communicates. The drain opening leads back to the chamber 83 so that any oil which would pass through the bushing 66 into the chamber 68 would be drained back eventually into the reservoir 52.

At the opposite end of the casing 10 from the bearing 51 a second bearing 10 for the shaft ll is provided. While the particular construction of the bearing 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 structure will be specifically described herein to establish its action and cooperation in the general combination of the compressor.

The bearing 10 is a tight-fitting bearing and quently gets slightly out of alignment due to various causes such as whip in the shaft when rotating at high speeds, means are provided to maintain proper tight-fitting engagement between shaft and hearing at all times so as to provide an effective seal for the shaft opening in the casing. The bearing I0 is connected to the casing I 0 by a flexible disc H. This disc H is made of strong, flexible metal so that it will flex during operation of the compressor to permit movement of the bearing II! with movement of the shaft H other than rotary movement so as to maintain at all times the tight flt between the bearing 'of annular grooves 84 -a suitable drain 85 into the chamber 12.

and shaft to preserve the seal and to preventexcess wear. on the hearing. The shaft opening opens into a chamber 12, into which the inner end of the bearing also extends, while the outer end of the bearing extends into a chamber 13. The chamber 12 is subjected to a pressure of approximately atmosphere, that is, a pressure slightly above or below atmosphere, namely the suction pressure of the vapor at the inlet of the impeller 39, while the chamber 13 is subjected to atmospheric pressure. Oil is delivered to the interior of the bearing III intermediate its ends from the oil inlet line 14 through a suitable connection 15. The inlet line 14 receives oil from the outlet end of the oil cooler 60. The oil passes longitudinally through the bearing in both directions, part of it passing intothe chamber 12 from which it drains through suitable drain outlets l1 and pipe connections 18 to a collection chamber 19. From that. chamber 19 the oil returns to the reservoir 52 through the piping system 80. The oil which flows outwardly through the bearing into the chamber 13 passes through suitable drain openings 8| into the collection chamber 82, from which it passes through the collection piping system 80 back to the reservoir 52.

The interior of the oil chamber 52 is under the same pressure as the shaft opening 50, viz., the pressure of the vapor at the initial inlet to the compressor. By having it under such relatively low pressure refrigerant which is carried thereto by the oil and is consequently delivered to the chamber at a pressure in excess of the pressure therein is released.

A bushing 83 is positionedbetween the chamber 12 and the impeller 39, similarin its construction to the bushing 66, having a plurality along-its bore, and is provided with an oil collection chamber 85 from which oil drains through The bushing 83 forms a dam to hinderleakage of oil into the suction of the impeller 39.

The construction of the bearing 10 and the lubrication of the bearing in the manner above spaced longitudinally.

, prevent oil from 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 compressorf But when the compressor is shut down the delivery of lubricating oil to the hearing will be stopped and consequentlyit is necessary to provide means to prevent either internal-leakage of-air or external leakage of vapor out of the casing'through the opening 5l at such times.

The structure provided for this purpose includes a packing collar 90, which is of any suitable type of soft, resilient material not susceptible to objectionabl corrosion or deterioration under action of the refrigerant vapor compressed.

pivotally suported at 95 and is connected to the sleeve 93 and to a pressure actuated piston 96,

' which is shown as connected to a bellows 91.

The piston 96 is urged inwardly, compressing the bellows Si, by a spring 98. Duringthe operation 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 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 lfll is mounted about the shaft I I and engages the inner side of the collar 90 inwardly of the shoulder 9|. A spring 12 engages the follower llll for urging itoutwardly 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 II for rotation therewith, between the collar 90 and the bearing HI, and in the chamber 13. This dish-shaped slinger I03 is provided for throwing oil away from'the shaft ll so as to leaking along the shaft to the collar 90. 4

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. v 1 i A What is claimed is: 1

1. In a centrifugal compressor, a casing, a driv ing shaft, a plurality of stage impellers on said shaft, said casing provided with openings'at its ends through which said shaft extends,'said impellers located and arranged whereby the-casing adjacent one of said openings will have'a maximum pressure therein less than the final discharge pressure of the compressor and the casing adjacent to the other opening will have initial suction pressure of the compressor therein, bearings for said shaft outwardly of said openings, a chamber about the bearing at the suction end i of the compressor and subject to initialsuction pressure of the compressor, a chamber'about a part of the bearing adjacent to the higher pressure end of the casing and subject to the pressure in the casing the maximum pressure of which is less than the discharge pressure of the compressor, a third chamber about the remaining part of said second-namedbearing and subjectto'fapproximately atmospheric pressure, an oil "reservoir for supplying oil to said bearings under pressure slightly in excess of the pressures at both ends of the bearings, and bushings carried by said casing between said bearings and adjacent impellers, said bushings. having oil collection chambers and passages therein for collecting and draining oil back to the bearing enclosingchani-- her adjacent thereto.

2. In a centrifugal compressor, a casing, adriving shaft, a plurality of stage impellers on said shaft, said casing provided with openings at its ends through which said shaft extends, said impellers located and arranged whereby thecaslng adjacent one of said openings will have a maximum pressure therein less than the finaldis charge pressure of the compressor and the casing adjacent to the other opening will have initial suction pressure of the compressor therein, bearin the casing the maximum pressure of which is less than the discharge pressure of the compressor, a third chamber about the remaining part of said second named bearing and subject to approximately atmospheric pressure, an oil reservoir, said chambers all draining back to said reservoir, and means in said reservoir for supplying oil to said bearings under pressure slightly in excess of the pressures at both ends of the bearings, said oil reservoir being subject to the and to release entrained refrigerant carried to the reservoir by the returning oil.

5. In a centrifugal compressor, a casing, a driving shaft, a plurality of stage impellers on said shaft, said casing provided with openings at its ends through which said shaft extends, said impellers located and arranged. whereby the casing adjacent one of said openings will have a maximum pressure therein less than the final discharge pressure of the compressor and the cusing adjacent to the other opening will have initial suction pressure of the compressor therein, bearings for said shaft located exteriorly of said shaft openings in the casing, a chamber about a part of the bearing adjacent to the higher pressure end of the casing and subject to the pressure in the casing the maximum pressure of which is less than the discharge pressure of the compressor, a support for said bearing at the initial suction pressure of the compressor so as so high pressure end of the casing, said support to permit the oil to drain freely thereto and to release entrained refrigerant carried .to the reservoir by the returning oil.

- 3. In a centrifugal compressor, a casing, a driving shaft, a plurality of stage impellers on said :5

shaft, saidmasing provided with openings at its ends through which said shaft extends, said impellers located and arranged whereby the casing adjacent one of said openings will have a maximum pressuretherein less than the final dls- 80 charge pressure of the compressor and the casing adjacent to the other opening will have initial suction pressure of the compressor therein, bearings for said shaft located exteriorly of said shaft openings in the casing, a chamber about apart 38 or the hearing adjacent to-the' higher pressure end of thecasingand subject to'the pressurein thecasing themaximumpressureofwhichisless than the discharge pressure of the compressor, a

of said chamber, an oil reservoir, and means in said reservoir for supplying. oil' to the hearing at the high pressur end oflthe casing under presforming the outer wall of said chamber, an oil reservoir, means in said reservoirfor supplyin oiltothebearingatthehighpressure e'ndofthe casing under pressure slightly in excess of the pressurcinthechambertoformasealin-tbe bearingto prevent leakage of refrigerant through the hearing, means cooperating with said bearing support to form an outer chamber outwardly of said first named chamber, said outer chamber enclosing the portion of said hearing which is not enclosed in said first named chamber and being subject to approximately atmospheric pressure, and means for draining oil from said chambers to said oil reservoir, said oil reservoir being subject to pressure lower than the pressure in thechamberssoastopermittheoiltodrain freely thereto and to release entrained refrigerant carried to thereservoir by the returning oil.

- 6. In a centrifugal compressor, a casing, a

' support for said hearing at the ,high pressure end 40 driving shaft, a plurality ofstage impellers on of the casing, said support forming the outer wall saidshaftsaidcasingpro withopeningsat its ends through which said shaft extends, said impellers located and arranged whereby the easing adjacent one of said openings will have a sure slightly in excess of the pr'essure'in thegmaximum pressure thereinlessthanthe final chamber to form a seal in the bearing to' prevent leakage of refrigerant through the bearing.

' 4. In a centrifugal compressor, a casing, a driving shaft, a plurality of stage impellers on said shaft, said casing provided with openings at its so ends through which said shaft extends, said impellers located and arranged whereby the casing adjacent one of said openings will have a maximumpressurethereinlessthantheiinaldischarge pressure of the compressor and the casing gs adjacent to the other opening will' have initial suction pressure of the compressor therein, bearings for said shaft located exteriorly of saidshaft openings in the casing, a chamber about a part of the bearing adjacent to the higher pressure end ,6

ofthec'asingandsubjecttothepressureinthe casing the maximum pressure of which is less than the discharge pressure of the compressor, a support for said bearing at the high pressure end of the casing, said support forming the outer wall of said chamber, an oil reservoir, means in said ,reservoir for supplying oil to the hearing at the high pressure and of the casing under pressure slightly in excess of the pressure in the chamber to form a seal through the bearing to prevent 0 leakage of refrigerant through the bearing, means for draining oil from said chamber to said 011- reservoir, and said oil reservoir being subject to pressure lower than the pressure in the chamdischargepressureofthecompressorandthc casing adjacent to the other opening will have initial suction pressure of the compressor therein, bearings for said shaft located exteriorly of said shaft openings in the casing, a

aboutapartofthcbearingadjaoenttothehigherpressurcendofthecasingandsubjecttothc pressurcintheccsingthemaximumpressureof whichislessthanthedischargepressureofthe compressor, a support for hearing at the highpremureendotthecasinmsaidsupport formingtheouterwallofsaidchambenanoil reservoir,andmeansinsaidreservoirforsupplyingoiltothebearingatthchighpressurcend amaximumpressurethereinless'thanthennal bersoastopermittheoil todrain freely thereto discharge pressure of the compressor and the casing adjacent to the other opening will have initial suction pressure of the compressor therein, bearings for said shaitlocated exteriorly of said shaft openings in the casing, a chamber about a part of the bearing adjacent to the higher pressure end of the casing and subject to the pressure in the casing the maximum pressure 01' which is less than the discharge pressure 01' the compressor, a support for said bearing at the high pressure end of the casing, said support forming the outer wall of said chamber, an oil reservoir, means in said reservoir for supplying oil to the bearing at the high pressure end oi the casing under pressure slightly in excess of the pressure in the chamber to form a seal in the bearing to prevent leakage of refrigerant through the bearing, means cooperating with said bearing 'sup-.

port to form an outer chamber outwardly of said first named chamber, said outer chamber enclosing the portion of said hearing which is not enclosed in said first named chamber and being subject to approximately atmospheric pressure, means for draining oil from said chambers to said oil reservoir, said oil reservoir being subject to pressure lower than the pressure inthe chambers was to permit the oil to drain freely thereto and to release entrained refrigerant carried to the reservoir by the returning'oil, and a bush.

'ing carried by said casing between said chamber and the adjacent impeller, said bushing having an oil collection chamber and passages therein for-collecting and draining 011- back to the chamher. 4 I a RALPH M. wA'rsou,

Images