US3877846A - Variable capacity screw compressor - Google Patents

Variable capacity screw compressor Download PDF

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Publication number
US3877846A
US3877846A US388600A US38860073A US3877846A US 3877846 A US3877846 A US 3877846A US 388600 A US388600 A US 388600A US 38860073 A US38860073 A US 38860073A US 3877846 A US3877846 A US 3877846A
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United States
Prior art keywords
working fluid
grooves
casing
inlet
inlet passage
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Expired - Lifetime
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US388600A
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English (en)
Inventor
Anders Lundberg
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Stal Refrigeration AB
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Stal Refrigeration AB
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Publication date
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/10—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber
    • F04C28/12—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves
    • F04C28/125—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves with sliding valves controlled by the use of fluid other than the working fluid

Definitions

  • ABSTRACT A variable capacity screw compressor comprising a casing, housing two intersecting bores defining a working chamber in which a pair of intermeshing screws comprising helical lands and intervening grooves are mounted to rotate and to compress a working fluid as it is being passed axially through the working chamber from a low pressure inlet wall to a high pressure outlet wall, the inlet wall having an inlet passage in substantially axial alignment with the axes of the rotary screws for filling the ends of the grooves facing the axial inlet passage with working fluid.
  • the capacity of the compressor to operate within a predetermined range of load variations from full load to no load conditions is regulated by a slide valve located on the high pressure side of the compressor and being axially displaceable in response to varying load conditions to expose a by-pass opening for venting partially compressed working fluid directly into the grooves of the compressor screws at a location between the bypass opening and the axially aligned inlet passage to thereby interrupt admission of cold working fluid into the grooves from the inlet passage.
  • an axially movable slide valve which forms part of the casing surface of the rotor housing, is located below and between the rotors, serving as adjustable exit for the tapped-off gas, which is led outside the rotor chamber casing, through channels provided in the compressor housing, and back to the inlet end piece.
  • the return channels also serve as draining passages for oil from the bearing on the outlet side and from any shaft seals, carrying the oil to the inlet gate, where it is drained into the operating chamber of the compressor, pumped out on the high pressure side, and separated from the gaseous working medium.
  • the tapped-off gas which is heated by the oil sprayed into the working chamber and by the heat of compression work which may be required to overcome the pressure drop in the gas being tapped off, squirts out and up into the inlet chamber together with possibly hot draining oil and thus heats up the intake or low pressure gas.
  • this occurrence works against the low temperature requirement of the intake gas and results in considerable heat losses with a consequent loss in efficiency.
  • the present invention overcomes the disadvantages of the prior art described above by, reducing the efficiency loss resulting from the heat loss when the compressor is under partial load while permitting a simplified construction of the rotor housing and inlet end piece.
  • the invention is based on the concept that a portion of partially compressed working medium is by-passed to the inlet side which implies that the slide valve must be arranged on the high pressure side. Furthermore, the by-passed medium must not be returned to the inlet chamber but to an opening in the cylindrical casing surrounding the working chamber in order to produce the intended effect and the inlet passage must be located in the end wall of the casing so as to extend substantially in axial alignment with the rotors.
  • the present invention provides at least one opening in the rotor chamber casing surface of the compressor housing, through which tapped-off gas is reintroduced into the rotor chamber, instead of being brought back to the inlet gate, as in the prior art.
  • This opening is located approximately along a helical line on the casing surface which corresponds to the path of the helical ribs of one of the rotors and which passes through the rear edge of the inlet gate. Therefore, the opening will be in communication with the particular helically shaped rotor space which at that specific moment is being closed off by the rear edge of the inlet gate after filling from the inlet gate has been completed.
  • the tapped-off gas from the unloading valve will be supplied through the casing opening to the various helical rotor spaces during the final stage of their intake or suction process, so that the mixing of cold intake gas with hot exhaust gas in the inlet end piece is avoided, and the resultant disadvantages eliminated.
  • FIG. 1 is a partial longitudinal sectional view of a compressor constructed according to this invention
  • FIG. 2 is a transverse sectional view, showing the inlet end piece of the compressor as seen from the inside;
  • FIG. 3 is a transverse section view, showing the outlet end piece of the compressor as seen from the inside;
  • FIG. 4 is a cross-sectional view through the compressor of this invention.
  • FIG. 5 is a developed plan view of the inside surface of the female rotor chamber casing of the compressor.
  • FIG. 6 is a developed plan view similar to FIG. 5 showing both rotor chamber casings developed from 7a to 7b of FIG. 5.
  • FIGS. 1-4 show the screw compressor of this invention with inlet end wall 1, rotor housing 2, outlet housing wall 3, and helical rotors 4a and 4b mounted within rotor casing portion 4 of rotor housing 2.
  • Gaseous working medium unloading means is here illustrated as axially movable slide valve 5.
  • the gas is drawn into the compressor and the helical grooves therein through intake connection 6 by means of inlet gate 7 which is located in the inlet end plane of rotors 4a and 4b and in axial alignment with the axes thereof whereby the gas will pass into the grooves in an axial direction from the end facing the inlet gate 7.
  • slide valve 5 rests against stop 8; during partial load conditions, slide valve 5 is displaced axially from stop 8 and a bypass opening 9 is created to permit exhaust gas to flow out into rotor housing 2.
  • the tapped-off gas proceeds through conventional closed channels in housing 2 to opening 10 located in the wall of casing 4 of the rotor chamber and is drawn into the thread volume of rotors 4a and 4b.
  • inlet gate 7 may be clearly seen in FIG. 2, which shows the inlet end wall 1 as seen from inside rotor housing 2.
  • FIG. 3 shows outlet gate 12 in outlet end wall 3, as seen from inside rotor housing 2.
  • Outlet gate 12 is provided in its lower portion with a recess complementary to and adapted to receive slide valve 5.
  • the positions of male helical rotor 4a, female helical rotor 4b and slide valve 5 relative to each other can readily be observed in FIG. 4, as well as outwardly extending ribs or lands 13 of female rotor 4b, which define intervening spaces or grooves 15.
  • FIG. 5 is a developed plan view of the inside surface of rotor chamber 4 of housing 2.
  • Unbroken double lines 13 indicate the location of the ribs or lands of female rotor 4b as they extend across the surface of casing 4 in the direction of the arrow.
  • Broken line 14 indicates the line on the surface of casing 4 where the rotors diverge (see FIG. 4), i.e., the upper middle edge of rotor housing 4 and where spaces or grooves 15 between rotor lands 13 of rotor 4b are blocked off by the projecting lands of male rotor 4a.
  • exhaust or recirculation opening 10 should be located along line 11 so that opening 10 is closed off from any given groove 15 no later than simultaneously with the closing off of this same groove 15 by rear edge 7a from inlet gate 7. In this way the tapped-off exhaust gas will be supplied to spaces 15 during the final stage of the intake process for each space 15. Therefore, depending on the degree to which slide valve is opened in response to varying load conditions, more or less of the tapped-off exhaust gas will be drawn directly into grooves 15 through casing opening block off gas from intake gate 7, thus controlling the capacity of the compressor.
  • grooves are filled with working medium from the end facing the inlet and passed axially through the working space until one of the corresponding lands a, b, c, d or e is about to pass the upper edge of the exhaust port 10.
  • the corresponding groove becomes aligned with the by-pass opening 9 exposed by the axial displacement of slide valve 5, allowing partially compressed working fluid to enter the inlet end of the groove and thus preventing further working fluid from being drawn into the groove from the axial inlet gate.
  • the partially compressed working fluid entering the groove acts as a stopper or plug. Obviously some mixing will take place between the partially compressed by-passed working fluid and the working fluid ahead of the by-pass, as well as with the non-compressed medium entering through the gate 7.
  • FIG. 6 shows both intersecting bores of the casing developed from to 7b and which include a second opening or port 10. It will be clear that the double lines in the lower half of FIG. 6 represent the lands 13 between the grooves 15 in the female rotor 4b, while the double lines in the upper half represent the narrow grooves 16 between the lands 17 of the male rotor shown in FIG. 4.
  • a variable capacity screw compressor comprising: a. a casing, housing two intersecting bores defining a working chamber in which a pair of intermeshing screws having helical lands and intervening grooves are mounted to rotate and compress a working fluid as it is being passed axially through said working chamber from a low pressure inlet wall to a high pressure outlet wall, said walls being located at opposite axial ends of said casing; b. an inlet passage in said inlet wall located in substantially axial alignment with the axes of said screws for admitting working fluid into the ends of valve to vent partially compressed air from the" working chamber; 7
  • variable capacity screw compressor according to claim 1, in which the means for passing the vented working fluid comprises a port in the working chamber casing, said port being so located that the leading flank of the lands of said screws will commence to pass across the rear edge of said axial inlet passage as the 7 following grooves become aligned with said port.
  • a variable capacity screw compressor in which a port is provided in said casing for each of the two bores.
  • variable capacity screw compressor in which the width of the port in the casing is of the same order of magnitude as the distance between the leading flanks of two successive lands. 7

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Rotary-Type Compressors (AREA)
US388600A 1972-08-28 1973-08-15 Variable capacity screw compressor Expired - Lifetime US3877846A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE11092/72A SE366374B (sv) 1972-08-28 1972-08-28

Publications (1)

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US3877846A true US3877846A (en) 1975-04-15

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US388600A Expired - Lifetime US3877846A (en) 1972-08-28 1973-08-15 Variable capacity screw compressor

Country Status (5)

Country Link
US (1) US3877846A (sv)
JP (1) JPS52251B2 (sv)
GB (1) GB1444373A (sv)
SE (1) SE366374B (sv)
SU (1) SU873894A3 (sv)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4003199A (en) * 1976-03-01 1977-01-18 General Motors Corporation Turbine engine with air brake
US4004864A (en) * 1974-07-01 1977-01-25 Svenska Rotor Maskiner Aktiebolag Method for modifying a compressing apparatus unit
EP0171180A1 (en) * 1984-07-04 1986-02-12 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US4770615A (en) * 1985-10-21 1988-09-13 Hitachi, Ltd. Screw compressor with scavenging port
US5052901A (en) * 1988-04-25 1991-10-01 Svenska Rotor Maskiner Ab Lift valve in a rotary screw machine
US6082985A (en) * 1997-09-10 2000-07-04 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US20110256011A1 (en) * 2008-11-20 2011-10-20 Aaf Mcquay Incorporated Screw compressor
US9057373B2 (en) 2011-11-22 2015-06-16 Vilter Manufacturing Llc Single screw compressor with high output
CN105386980A (zh) * 2015-11-30 2016-03-09 珠海格力电器股份有限公司 一种螺杆压缩机及空调系统

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0191715U (sv) * 1987-12-07 1989-06-15

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3088658A (en) * 1959-06-04 1963-05-07 Svenska Rotor Maskiner Ab Angularly adjustable slides for screw rotor machines
US3088659A (en) * 1960-06-17 1963-05-07 Svenska Rotor Maskiner Ab Means for regulating helical rotary piston engines

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3088658A (en) * 1959-06-04 1963-05-07 Svenska Rotor Maskiner Ab Angularly adjustable slides for screw rotor machines
US3088659A (en) * 1960-06-17 1963-05-07 Svenska Rotor Maskiner Ab Means for regulating helical rotary piston engines

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4004864A (en) * 1974-07-01 1977-01-25 Svenska Rotor Maskiner Aktiebolag Method for modifying a compressing apparatus unit
US4003199A (en) * 1976-03-01 1977-01-18 General Motors Corporation Turbine engine with air brake
EP0171180A1 (en) * 1984-07-04 1986-02-12 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US4770615A (en) * 1985-10-21 1988-09-13 Hitachi, Ltd. Screw compressor with scavenging port
US5052901A (en) * 1988-04-25 1991-10-01 Svenska Rotor Maskiner Ab Lift valve in a rotary screw machine
US6082985A (en) * 1997-09-10 2000-07-04 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US20110256011A1 (en) * 2008-11-20 2011-10-20 Aaf Mcquay Incorporated Screw compressor
US8702408B2 (en) * 2008-11-20 2014-04-22 Aaf Mcquay Incorporated Slide for use in a screw compressor
AU2009316974B2 (en) * 2008-11-20 2014-09-18 Aaf Mcquay Incorporated Screw compressor
US9057373B2 (en) 2011-11-22 2015-06-16 Vilter Manufacturing Llc Single screw compressor with high output
CN105386980A (zh) * 2015-11-30 2016-03-09 珠海格力电器股份有限公司 一种螺杆压缩机及空调系统

Also Published As

Publication number Publication date
JPS52251B2 (sv) 1977-01-06
SE366374B (sv) 1974-04-22
GB1444373A (en) 1976-07-28
SU873894A3 (ru) 1981-10-15
JPS4959309A (sv) 1974-06-08

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