EP0245427A1 - Screw rotor compressor and refrigeration plant. - Google Patents
Screw rotor compressor and refrigeration plant.Info
- Publication number
- EP0245427A1 EP0245427A1 EP19860906989 EP86906989A EP0245427A1 EP 0245427 A1 EP0245427 A1 EP 0245427A1 EP 19860906989 EP19860906989 EP 19860906989 EP 86906989 A EP86906989 A EP 86906989A EP 0245427 A1 EP0245427 A1 EP 0245427A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- compressor
- rotor
- port
- outlet port
- groove
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- 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
- the present invention relates to a screw compressor, espe ⁇ cially adapted for use within a refrigeration plant with- two stage throttling.
- a compressor comprises a casing with a working space generally composed of intersecting bo- res with parallel axes enclosed by barrel and end walls and provided with spaced apart inlet and outlet ports for com ⁇ munication with inlet and outlet channels, respectively.
- Rotors each having helical lands and intervening grooves, are disposed in the bores and intermesh in pair.
- One rotor of the pair is of male rotor type formed such that at least the major portion of each land and groove is located outsi ⁇ de the pitch circle of the rotor.
- the other rotor is of fe ⁇ male rotor type formed such that at the major portion of each land and groove is located inside the pitch circle of the rotor.
- Two communicating groove portions thus form a chevron-shaped chamber having its base end disposed in a plane transverse to the axes of the bores and adjacent to the outlet port.
- the compressor is provided with capacity control means comprising a bleed port and a valve member having an axially displaceable control edge defining the actual size of the port.
- the compressor is further provided with means for additional supply of working fluid at a pressure higher than the normal inlet pressure.
- a compressor of the above type for use in a re rigeration plant is known from Swedish patent 382 663.
- This compressor is provided with an axially slidable valve of the type shown in Swedish patent 366 375, i.e. a valve member dispo ⁇ sed in the barrel wall of the working space and including the intersection line between the bores so that the valve simultaneously adjusts a bleed port at one end and the out ⁇ let port at the other end.
- This valve member is provided with openings, for additional supply of gas from the first throttling stage, situated so that at maximum capacity the openings are disposed on such a distance from the inlet end wall that they communicate with a chevron-shaped chamber first after the initiation of the compression.
- a valve member of the type shown decreases for a certain displacement thereof the outlet volume, i.e. the volume of the chevron-shaped chamber when opening towards the outlet port, and the inlet volume, i.e. the volume of the chevron-shaped chamber when cut off from the bleed port, with the same quantity.
- the ratio between the inlet volume and the outlet volume, the built-in volume ratio thus increases with increasing bleed off. This effect is further accentuated when additional working fluid is supp ⁇ lied after the cut off from the bleed port.
- the bleed port In order to avoid too high built-in volume ratios and over-compression resulting therefrom the bleed port must when opened momen- tarily mean a considerable reduction of the inlet volume eventhough this on the other hand means a low built-in vo ⁇ lume ratio resulting in under-compression.
- the possibility to vary the volumetric capacity of a compressor without too high losses in the adiabatic efficiency is thus limited.
- With additional supply openings in the valve member there is a further problem that those openings in order to main ⁇ tain a higher pressure therein than the inlet pressure must be located on a considerable distance from the edge thereof controlling the bleed port. Consequently the bleed port in such a compressor must be situated closer to the inlet end wall than in normal compressors.
- the object of the present invention is to provide a comp ⁇ ressor of the type specified where the range of capacity variation with high adiabatic efficiency is considerably extended simultaneously as the intermediate, additional supply pressure is on a steady high level required for an optimum process, which means that the over-all efficiency of the plant at part load is kept on a much higher level than that obtained by earlier used compressors.
- This object is met according to the invention by providing two separate valves, one controlling the bleed port for ad ⁇ justment of the capacity and one controlling the outlet port for adjustment of the built-in volume ratio, where the means for additional supply is located in the capacity control valve in such a position that it will never direct ⁇ ly communicate with the bleed port, and where the outlet port valve is selectively adjustable.
- a further improvement of the efficiency of the compressor may be obtained by providing the outlet port valve with in ⁇ jection means for a cooling and sealing liquid, said injec ⁇ tion means being located such that it never communicates with any of the inlet and outlet ports or with the additio ⁇ nal supply means, at least at low capacity reduction condi- tions.
- Fig. 1 shows a transverse section of a screw compressor ta ⁇ ken along line 1-1 in Fig. 2,
- Fig. 2 shows a developed view of the barrel wall of a screw compressor taken along line 2-2 in Fig. 1
- Fig. 3 shows diagrammatically a refrigeration plant with two stage throttling and a compressor according to Figs. 1 and 2
- Fig. 4 shows diagrammatically the built-in volume ratio of a compressor as shown in Figs. 1 and 2 as a function of the position of the capacity valve
- Fig. 5 shows diagrammatically the thermodynamical process within a plant as shown in Fig. 4.
- the compressor shown in Figs. 1 and 2 comprises a male ro ⁇ tor 10 provided with five helical lands 12 and intervening grooves 14 and a female rotor 16 intermeshing therewith and provided with six helical lands 18 each enclosing a rotor and intervening grooves 20.
- the rotors 10, 16 are mounted in a housing having low and high pressure end wall members and a barrel member 22 comprising two intersecting bores each enclosing a rotor.
- the housing is provided with an in- let port 24 at the low pressure end and extending as a re ⁇ lieved portion into the barrel wall and an outlet port 26 at the high pressure end.
- the barrel member 22 there are further two circular grooves intersecting with the barrel wall and each enclosing an axially adjustable valve member 28, 30 sealingly cooperating with the facing rotor 10, 16.
- One of the valve grooves forms the outlet port 26 and a pressure adjusting valve member 28 enclosed therein is pro ⁇ vided with a control edge 32 defining the actual shape and size of the outlet port 26.
- the other valve groove is loca- ted in the wall of the bore enclosing the male rotor 10, peripherally out of the area of the outlet port 26 and en ⁇ closes a capacity adjusting valve member 30 provided with a control edge 34 facing the inlet port 24 and at full capa ⁇ city defining a part of the edge thereof, whereas at redu- ced capacity this edge defines the size and shape of a bleed port 36 communicating with the inlet port 24.
- the ca ⁇ pacity valve 30 is further provided with an opening 38 for supply of additional working fluid at an intermediate pres ⁇ sure higher than that of the fluid supplied through the in- let port 24. This additional supply opening 38 is located at an axial distance from the control edge 34 corresponding to the axial distance between two consecutive lands 12 of the facing rotor 10.
- the pressure valve 28 is similarly provided with an opening 40 for supply of a cooling and sealing liquid, which in a refrigeration compressor may consist of liquefied working fluid preferably having a tem ⁇ perature below the condensing temperature, which will im ⁇ prove the efficiency of the compressor.
- a refrigeration plant which comprises a compressor 42 of the type specified above, a condenser 44 connected to the compressor outlet port 26, a first thrott ⁇ ling valve 46 located between the condenser 44 and a flash chamber 48, which in turn is connected on the gas side to the intermediate pressure supply opening 38 of the compres ⁇ sor and on the liquid side to a second throttling valve 50, and an evaporator 52 connected to the second throttling valve 50 and the low pressure compressor inlet 24.
- the built-in volume ratio (V ⁇ ) is shown as a function of the position (L) of the control edge 34 when moving from the position for maximum capacity to the posi ⁇ tion for minimum capacity, where a fixed edge of the axial portion may decide the size of the outlet port 26.
- the built-in volume ratio will be kept practically constant at all capacities which means that the efficiency of the compressor can be kept on a high level over a wide field of part load capacity, si ⁇ multaneously as the so called "economizer" effect is main- tained at an optimum level.
- the corresponding function for compressors as shown in Swedish patent 382 663 and in US patent 3 568 466, supplemented by a conventional capacity valve as shown in US patent 3 314 597, respectively.
- the ratio will be lower than the ideal, which means undercompression and consequently a completion of the compression will be by full back pressure compression, which means a loss and consequently a decreased efficiency.
- thermodynamical process within the plant shown in Fig. 3 is indicated in Fig. 5 as a diagram showing the relation between the pressure (log p) and the enthalpy (i).
- the different points thereof related to specific details indicated in the plant shown in Fig. 3 has been denoted by the same reference numbers.
- the line 42 corresponds to the compressor, with its inlet port, additional supply opening, and outlet port at point 24, 38 and 26, respectively.
- Line 44 corresponds to the condenser
- point 46 corresponds to the first throttling valve
- point 48 to the flash chamber
- point 50 corresponds to the second throttling valve
- line 52 corresponds to the evaporator.
- the process drawn in continuous lines indicates the process at full load and at part load according to the invention.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Applications Or Details Of Rotary Compressors (AREA)
Abstract
Compresseur hélicoïdal, surtout adapté à fonctionner en liaison avec une installation frigorifique. Le compresseur est constitué d'un boîtier pourvu d'un espace de travail généralement sous la forme d'alésages se chevauchant à axes parallèles, et pourvu d'orifices d'entrée et de sortie espacés l'un de l'autre, ainsi que d'une paire de rotors mâle et femelle, dont chacun possède des parties hélicoïdales pleines et des rainures intermédiaires. Le compresseur est doté d'un moyen de réglage de la capacité, sous la forme d'un orifice de purge et d'un élément à soupape dont le rebord de régulation est déplaçable dans le sens axial et qui définit la dimension réelle de l'orifice, ainsi que de moyens pour fournir une quantité supplémentaire de fluide de travail à une pression supérieure à la pression d'entrée normale. Le moyen de régulation de la capacité est situé périphériquement à l'extérieur de l'orifice de sortie, et le moyen d'alimentation supplémentaire comporte un orifice à l'intérieur de la soupape de régulation de la capacité, situé à une distance axiale par rapport au rebord de régulation qui correspond au moins à la distance axiale entre deux parties pleines consécutives du rotor opposé. De plus, le compresseur est pourvu de moyens séparés pour le réglage sélectif de l'orifice de sortie.Helical compressor, especially suitable for operating in conjunction with a refrigeration installation. The compressor consists of a housing provided with a working space generally in the form of overlapping bores with parallel axes, and provided with inlet and outlet openings spaced apart from each other, as well as a pair of male and female rotors, each of which has solid helical parts and intermediate grooves. The compressor is provided with a capacity adjustment means, in the form of a purge orifice and of a valve element the regulation flange of which is movable in the axial direction and which defines the actual dimension of the orifice, as well as means for supplying an additional quantity of working fluid at a pressure higher than the normal inlet pressure. The capacity control means is located peripherally outside the outlet port, and the additional supply means has a port inside the capacity control valve, located at an axial distance from ratio to the regulation rim which corresponds at least to the axial distance between two consecutive solid parts of the opposite rotor. In addition, the compressor is provided with separate means for the selective adjustment of the outlet orifice.
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8528211 | 1985-11-15 | ||
GB858528211A GB8528211D0 (en) | 1985-11-15 | 1985-11-15 | Screw compressor |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0245427A1 true EP0245427A1 (en) | 1987-11-19 |
EP0245427B1 EP0245427B1 (en) | 1989-10-04 |
Family
ID=10588296
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19860906989 Expired EP0245427B1 (en) | 1985-11-15 | 1986-11-14 | Screw rotor compressor and refrigeration plant |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0245427B1 (en) |
AU (1) | AU6732287A (en) |
DE (1) | DE3666074D1 (en) |
GB (1) | GB8528211D0 (en) |
WO (1) | WO1987003048A1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5228301A (en) * | 1992-07-27 | 1993-07-20 | Thermo King Corporation | Methods and apparatus for operating a refrigeration system |
US5246357A (en) * | 1992-07-27 | 1993-09-21 | Westinghouse Electric Corp. | Screw compressor with oil-gas separation means |
WO2008112569A2 (en) * | 2007-03-09 | 2008-09-18 | Johnson Controls Technology Company | Refrigeration system |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NO117317B (en) * | 1964-03-20 | 1969-07-28 | Svenska Rotor Maskiner Ab | |
SE338576B (en) * | 1968-05-06 | 1971-09-13 | Stal Refrigeration Ab | |
SE366375B (en) * | 1972-06-30 | 1974-04-22 | Stal Refrigeration Ab | |
SE382663B (en) * | 1974-04-11 | 1976-02-09 | Stal Refrigeration Ab | PROCEED TO INSERT INTERMEDIATE PRESSURE GAS INTO A SCREW COOLER COMPRESSOR AND SCREW COMPRESSOR FOR PERFORMING THE KIT. |
-
1985
- 1985-11-15 GB GB858528211A patent/GB8528211D0/en active Pending
-
1986
- 1986-11-14 DE DE8686906989T patent/DE3666074D1/en not_active Expired
- 1986-11-14 AU AU67322/87A patent/AU6732287A/en not_active Abandoned
- 1986-11-14 EP EP19860906989 patent/EP0245427B1/en not_active Expired
- 1986-11-14 WO PCT/SE1986/000526 patent/WO1987003048A1/en active IP Right Grant
Non-Patent Citations (1)
Title |
---|
See references of WO8703048A1 * |
Also Published As
Publication number | Publication date |
---|---|
EP0245427B1 (en) | 1989-10-04 |
WO1987003048A1 (en) | 1987-05-21 |
AU6732287A (en) | 1987-06-02 |
DE3666074D1 (en) | 1989-11-09 |
GB8528211D0 (en) | 1985-12-18 |
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