US3461685A

US3461685A - Inlet guide vane actuating arrangement for multistage centrifugal compressor

Info

Publication number: US3461685A
Application number: US657914A
Authority: US
Inventors: David C Hoffman; Wyman K Ender; Allan I Wold
Original assignee: Trane Co
Current assignee: Trane US Inc
Priority date: 1967-08-02
Filing date: 1967-08-02
Publication date: 1969-08-19
Anticipated expiration: 1986-08-19

Description

Aug. 19, 1969 c, HOFFMAN ET AL 3,461,685

' mm-rr uuwm VANI-J ACTUATING ARRANGEMENT FOR MULTIS'IAGE CBNTRIFIJGAIJ COMPRESSOR Filed Aug.

3 Sheets-Sheet 1 FIG.

m N 52 QM m K\ 4 2 B MZM 8 I 8 l z 4 3 .l 6 0 3 3M 3 4 6 5 6 8 4 O 4 2k 7 .n 4

INVENTORS DAVID C. HOFFMAN WYMAN K.

[ENDER BMLAN WOLD ATTORNEY Afig. 19, 1969 D, Q HOFFMAN ETAL 3,461,685

INLET GUIDE VANE ACTUA'IING ARRANGEMENT FOR MULTISTAGE CEN'IRTF'UGAL COMPRESSOR I5 Sheets-Sheet 2 Filed Aug.

FIG. 4

I NVENTOR 5 DAVID C. HOFFMAN WYMAN K. EHDER ALLAN I. WOLD m 0 W ATTORNEY Aug. '19, 1 969 c op ETAL 3,461,685

INLET GUIDE vmm ACTUATING ARRANGEMENT FOR MULTIS'IAGE CENIHIFUGAL COMPRESSOR Filed Aug. 2, 1967 s Sheets-Sheet s FIGJ5 IOO INVENTORS DAVID c. HOFFMAN WYMAN K. ENDER B ALLAN I. wow

ATTOIRNEY United States Patent U.S. Cl. 62-510 10 Claims ABSTRACT OF THE DISCLOSURE A multiple stage refrigerant compressor is provided with adjustable guide vanes at the inlet to each stage of compression, with the linkage mechanism for each set of guide vanes being actuated by a common operating shaft which extends through the compressor casing at only one point. The guide vane operating shaft section for an advanced stage of compression extends axially of the compressor casing outside of the interstage crossover passage, thereby minimizing the number of seals required along the operating shaft. The linkage mechanism for the advanced stage adjustable guide vanes is located in a chamber which also serves as a plenum space from which economizer gas is injected into the return passage leading to the advanced stage impeller.

This invention relates to an arrangement for installing and operating inlet guide vanes for the successive stages of a high pressure, centrifugal, refrigerant compressor. Adjustable guide vanes on stages other than the first stage of a multiple stage compressor offer the advantages of betterperformance and capacity range. The positioning of the guide vanes at each stage of compression determines the total capacity developed by the compressor. Better capacity control, especially under light load conditions, could be achieved by utilizing adjustable guide vanes at each compression stage. However, assembly problems and the additional space required to accommodate the linkage mechanism for guide vanes at each impeller inlet have generally discouraged the use of adjustable guide vanes at advanced stages of compression. Also, the additional linkages and operating shafts required for such an adjustable guide vane arrangement have presented complicated seal problems.

By virtue of a unique operating shaft and linkage location and arrangement, the present invention overcomes the aforesaid problems in providing adjustable guide vane control at each stage of a multiple stage refrigerant compressor. The centrifugal compressor of this invention is designed to compress refrigerant gas in a refrigeration system comprising a compressor, condenser, economizer, and evaporator interconnected in refrigerant flow relationship. The economizer is a chamber normally located between the condenser and the evaporator in which the pressure of the liquid refrigerant is reduced before it enters the evaporator. Pressure reduction in the economizer causes a portion of the liquid to fiash to vapor, thereby cooling the remaining liquid. The flash gas from the economizer is normally directed to an intermediate pressure stage of the multiple stage refrigerant compressor. Our improved compressor design incorporates a chamber between the return passage leading to an advanced stage of compression and the diffuser passage connected to the outlet thereof. This chamber serves the dual purpose of accommodating the linkage mechanism for the adjustable guide vanes at the inlet to the advanced stage of compression and also acting as a plenum chamber from which ice economizer gas may be introduced into said return passage.

A particularly advantageous feature of this invention lies in the disposition of the interstage crossover passage between successive stages of compression radially inwardly from the outer casing of the compressor. This provides a space between the crossover passage and the outer casing through which the operating shaft for an advanced stage vane linkage mechanism may extend. By thus avoiding passing the guide vane operating shaft through any portion of the interstage crossover passage the number of seals required along the operating shaft is reduced to a minimum.

These and other advantageous features of our invention will become readily apparent as the following description is read in conjunction with the accompanying drawings.

FIGURE 1 is a front elevation view, partially in section, showing a centrifiugal compressor embodying the guide vane actuating mechanism of this invention.

FIGURE 2 is a vertical section view taken along line 22 of FIGURE 1.

FIGURE 3 is a vertical section view taken along line 33 of FIGURE 1 showing the first adjustable guide vane actuating mechanism,

FIGURE 4 is an enlarged fragmentary view of a portion of the guide vane actuating mechanism for the second stage.

FIGURE 5 is a schematic illustration of a refrigeration system employing the compressor of the present invention.

With reference to FIGURE 1 of the drawings, the multiple stage compressor of this invention is comprised of an outer casing 1 through which a drive shaft 4 extends longitudinally. Shaft 4 may be driven by any con venient means such as an electric motor or a turbine. For purposes of illustration, two axially spaced impeller wheels 6 and 10 are shown mounted upon drive shaft 4. Casing 1 could obviously be enlarged so as to house a larger number of impeller wheels and thereby provide greater compressor capacity. Secured to each of the impeller wheels 6 and 10 are a plurality of blades 8 and 12 which extend radially outwardly to the peripheral discharge area of each of said wheels. An internal wall generally indicated by reference numeral 14 defines a crossover passage 15 which connects the outlet of first stage impeller 6 with the inlet of second stage impeller 10. A first radially extending portion 16 of wall 14 bounds a discharge passage 18 for impeller 6. A second radially extending portion 20 of wall 14 encloses return section 22 of crossover passage 15. Diffuser plate 24 bounds discharge passage 25 communicating with the peripheral outlet of second stage impeller 10. Refrigerant gas passing radially outwardly through discharge passage 25 is collected in annular chamber 26 from which it is directed out of the compressor casing through discharge pipe 28 shown in FIGURE 5.

Refrigerant gas is introduced into compressor casing 1 through suction pipe 30. Suction inlet passage 32 bounded by suction plate 34 serves to direct incoming refrigerant gas radially inwardly and then axially into the inlet of first stage impeller Wheel 6. Adjustable guide vanes 36 located in suction inlet passage 32 operate to control the capacity of first stage impeller 6 and to give the desired pre-rotation to the infiowing refrigerant gas. Vanes 36 are disposed around the entire circumference of inlet passage 32 and are rotatably mounted on pins 38. A second set of adjustable guide vanes 40 are rotatably mounted in return passage 22 leading to the inlet of second stage impeller 10.

With reference to FIGURES 1 and 3, first stage guide vanes 36 are actuated by a linkage mechanism generally indicated by reference numeral 42. Mechanism 42 includes levers 44 which turn vane pins 38 and are operated by rods 46 connected to ring 48. Three equally spaced rollers 50 (only one of which is shown) rotatably support ring 48. Lever 52 for ring 48 is actuated by connecting rod 54 attached to crank 56. The aforesaid linkage mechanism is driven by an operating shaft arrangement comprised of a first operating shaft section 58 and a second section 60. One end of shaft section 58 extends through seal housing 62 in outer casing 2 to a point of connection with external actuating crank 64. Leakage of refrigerant gas outwardly along shaft section 58 is prevented by spring-loaded graphite seal 66. Control apparatus responsive to the cooling load on the refrigeration system in which compressor 1 is installed may be employed to actuate crank 64. Such a control arrangement is shown in US. Patent No. 2,955,436.

Operating shaft section 58 extends inwardly through bearing bracket 68, and is secured at its inner end to crank 70. Rod 72 connects

cranks

70 and 56. The rotation of first operating shaft section 58 and crank 70 therewith actuates interconnected crank 56, and first stage vane linkage 42 connected thereto. In this manner, first stage guide vanes 36 are adjusted to the proper position in response to the load sensing device connected to external crank 64.

As first stage linkage crank 56 rotates, it turns second operating shaft section 60 to which it is fixedly secured. This permits the synchronous actuation of second stage vane linkage 74 which is connected to the inner end of operating shaft section 60. Linkage 74 is comprised of the same basic elements as described above with respect to first stage linkage 42. Referring now to FIGURES l and 2, this includes vane turning levers 76 connected by rods 78 to synchronizing ring 80. Ring 80 is rotated on rollers 82 by lever 84. Movement is imparted to lever 84 by connecting rod 86, which is secured to crank 88 for actuation thereby. Crank 88 is secured to second operating shaft section 60 for rotation therewith. Sleeve bearing 92 mounted in bearing bracket 94 supports shaft section 60 at its inner end. As is indicated in FIGURE 1, bearing bracket 94 is fastened to diffuser plate 24.

FIGURE 4 shows the final drive portion of second stage linkage mechanism 74 on an enlarged scale. Second stage guide vanes 40 are pivotally mounted on pins 90 connected to levers 76. As connecting rods 78 are moved by the rotation of ring 80', the pivot levers 76, and vane pins 90.

FIGURE illustrates the manner in which compressor 1 would normally be connected in a refrigeration circuit. Refrigerant vapor from evaporator 96 is drawn into compressor 1 through suction pipe 30, progressively raised in pressure as it passes through the successive impeller wheels and internal passages, and discharged through pipe 28. The compressed refrigerant gas flows through discharge pipe 28 into condenser 100 where it is cooled and condensed to the liquid state by a cooling medium passing through condenser coil 101. Liquid refrigerant flows out of condenser 100 through liquid line 102 to economizer vessel 104. The refrigerant liquid flashes to an intermediate pressure in economizer 104, as a result of which a certain amount of flash gas is formed, thereby cooling the main body of refrigerant liquid. The chilled refrigerant liquid is directed through pipe 106 and valve 107 to evaporator 96 where it vaporizes to produce the desired cooling effect on a secondary liquid such as water flowing through coil 108. The flash vapor formed in economizer 104 passes through pipe 110 into casing 2 of compressor 1.

As is shown in FIGURE 1, the economizer gas entering compressor 1 is received in chamber 112 formed Within casing 2 between second stage diffuser plate 24 and radially extending portion of wall 14. A plurality of nozzles 114 in wall portion 20 conduct economizer gas from chamber 112 into passage 22 leading to second stage impeller wheel 10. Chamber 112 thus serves as an economizer gas plenum chamber as well as a housing for second stage guide vane linkage mechanism 74.

Wall assembly 14 includes a solid section 116 located between crossover passage 15 and outer casing 2. Operating shaft section 60 extends through solid section 116 radially outwardly from crossover passage 15 into economizer gas chamber 112. Since shaft section 60 does not pass through any portion of crossover passage 15, the problem of providing seals to prevent interstage leakage of refrigerant gas along shaft section 60 is greatly minimized. Leakage can only take place from relatively higher pressure economizer chamber 112 along shaft section 60 into space 33 adjacent first stage suction inlet passage 32. Such leakage is prevented by a single seal 118 positioned between shaft section 60 and wall section 116.

The assembly procedure is simplified by using two operating

shaft sections

58 and 60 rather than one. Section 60 may be inserted through wall section 116 and crank 88 into bearing 92 and aligned in bearing bracket 68 with end cover assembly 3 removed. After first stage linkage 42 is installed and end cover assembly 3 mounted on casing 2, first operating shaft section 58 is inserted through bearing housing 62. The alignment of short shaft section 58 in bearing bracket 68 and the mounting of crank 70 on its inner end is a relatively simple operation. It would be considerably more diflicult to align a single, long operating shaft within the several spaced bearings and seals in casing 2 and connect it to cranks 56 and 88 than to install separate,

short sections

58 and 60.

We claim:

1. A multiple stage refrigerant compressor comprising:

an outer casing;

a drive shaft extending through said casing;

a plurality of Centrifugal impeller wheels mounted on said drive shaft in axially spaced relationship;

wall means within said outer casing defining a cross over passage having a diffuser portion and a return portion connecting the outlet of one of said impeller wheels with the inlet of the next one of said impeller wheels;

a first set of adjustable guide vanes in the suction inlet of said one of said impeller wheels;

a second set of adjustable guide vanes in the suction inlet of said next one of said impeller wheels;

operating shaft means extending within said outer casing through said wall means radially outwardly from said crossover passage, said shaft means having one end portion which passes through said outer casing to a point of connection with external actuating means;

first and second linkage mechanisms operatively connected to said first and second sets of adjustable guide vanes, each of said linkage mechanisms including a crank fixedly secured to said operating shaft means for rotation therewith;

a diffuser plate bounding a diffuser passage communicating with the outlet of said next one of said impeller wheels, said diffuser plate being spaced from said return portion of said wall means so as to define therebetween a chamber within which said second linkage mechanism connected to said second set of adjustable guide vanes is located.

2. A compressor as defined in claim 1 wherein:

said operating shaft means is rotatably supported at the opposite end portion thereof by a bearing mounted on said diffuser plate.

3. A compressor as defined in claim 1 wherein:

said chamber is bounded at its outer extremity by said outer casing; and

said crank of said linkage mechanism for said second set of adjustable guide vanes extends within said chamber in a direction generally normal to said operating shaft means to a point of connection therewith in the portion of said chamber adjacent the inside of said outer casing.

4. A compressor as defined in claim 1 wherein:

said operating shaft means is comprised of first and second sections, said first section including said end portion which passes through said outer casing; and

said cranks of said first and second linkage mechanisms being secured to said second section.

5. A compressor as defined in claim 4 and further including:

linkage means drivingly connecting said first section of said operating shaft means to said crank of said first linkage mechanism.

6. A compressor as defined in claim 1 and further including:

a suction plate bounding a suction inlet passage to said one of said impeller wheels; and

wherein said first linkage mechanism is located outside of said suction inlet passage between said suction plate and one end of said casing in a region where it does not interfere with gas flowing into and through said suction inlet passage.

7. In combination with a condenser, economizer, flow regulating means and an evaporator interconnected in a closed refrigeration circuit, an improved centrifugal compressor connected in said circuit between said evaporator and said condenser and comprising:

an outer casing;

a drive shaft extending through said casing;

wall means within said outer casing defining a crossover passage connecting the outlet of one of said impeller wheels with the inlet of a following one of said impeller wheels, said wall means including a first substantially radially extending portion bounding a discharge section of said crossover passage and a second substantially radially extending portion :bounding a return section of said crossover passage; a diffuser plate enclosing a diffuser passage communicating with the outlet of said following one of said impeller wheels, said diffuser plate being spaced from said second radially extending portion of said wall means so as to provide a chamber therebetween;

a first set of adjustable guide vanes in the suction inlet of said one of said impeller wheels; a second set of adjustable guide vanes in the suction inlet of said following one of said impeller wheels;

first and second linkage mechanisms operatively connected to said first and second sets of adjustable guide vanes, said second linkage mechanism being located in said chamber;

10 end portion which passes through said outer casing to a point of connection with external actuating means, and each of said first and second linkage mechanism being operatively connected to said shaft 5 means for synchronous actuation thereby.

9. Refrigeration apparatus as defined in claim 8 wherein:

said wall means includes a solid section disposed between said crossover passage and said outer casing which separates said chamber from a space within said outer casing adjacent said suction inlet of said one of said impeller wheels; and wherein said operating shaft means passes from said space through said solid section into said chamber; and further including a seal between said operating shaft means and said solid section arranged to prevent leakage of refrigerant gas from said chamber into said space. 30 i0. Refrigeration apparatus as defined in claim 8 wheresaid operating shaft means is comprised of first and second sections, said first section including said end portion which passes through said outer casing, and said second section being connected to said first and second linkage mechanisms.

References Cited UNITED STATES PATENTS MEYER PERLIN, Primary Examiner s. c1. X.R,. 230-114