GB2185288A - Screw type compression and expansion machine - Google Patents

Abstract

The machine has the rotors of the compressor 1 directly coupled to the rotors of the expander 11. The positional control or timing function for the expander unit is achieved by the same means as that used for the compressor unit thus deleting the need for two timing devices. In the embodiment shown the timing function is carried out by a pair of timing gears 5, 6 but may instead be achieved by the rotor to rotor contact in the compressor unit. More than one compressor or expander unit may be present. <IMAGE>

Description

SPECIFICATION Direct coupled screw rotor expander compressor This invention relates to a direct coupled screw rotor expander compressor.

Screw rotor positive- displacement machines for an elastic working fluid are well known both as compressors and expanders. In such machines there is a casing enclosing a working space comprising two intersecting bores having parallel axes and forming a boundary wall fortheworking space, a high pressure and a low pressure end wall disposed perpendicuiarly tothe axes ofthe bores andwith high pressure and low pressure parts. Each bore contains one rotor of a pair of intermeshing rotorsofso called male and female form with helical lands and intervening grooves. Each rotor having a wrap angle of less than 360 . The male rotor formed with convex lands usually has the major portions of each land outside the pitch circle.The female rotor, formedwith concave lands usually has the major portion of each land inside the pitch circle.

It is an advantage in compression machines of this type thatwhen running dry i.e. with a gas medium devoid of liquid lubricantthatthe two rotors are kept apart by timing gears in orderto avoid rubbing and seizure of the dry rotor surfaces. The timing gears normally run in a sealed case where they can be lubricated.

Alternatively lubricant may be injected into the gas compression space in which case the rotors may be run one against the other. In this case the need for accurate and expensive timing gears is dispensed with. Howeverthe oil must be separated from the gas after compression. When operated as gas expander units it is usually inconvenient to use lubricant in the gas medium and timing gears must be used.

According to the present invention there is provided a screwtype gas compression and expansion machine comprising a gas expander unit with its two rotors directly coupled respectively to the two rotors of the gas compression unit such that the positional control ortiming function of the expander unit rotors is carried out by the same means as that which positionally controls or times the gas compressor unit rotors.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: *Figure 1 shows in perspective the gas compressor rotors coupled directly to the gas expander.

*Figure 2 shows in perspective the gas compressor rotors and gas expander rotors within their respective casings and also show the gas flows.

Referring to the drawings the gas compressor 1 has a casing 2 a male rotor3 and afemale rotor4 controlled so asto run ata small butfinite clearance to oneanotherbytiming gears5and 6via shafts7 and 8.

The gas expander 11 has a casing 12 and male rotor 13 coupled directly to compressor rotor3 and afemale rotor 14 coupled directly to compressor rotor 4 via shafts9and10.Therotors13and140fthegas expanderarethus also controlled to run at a small but finite clearance to one another by timing gears 5 and 6.

The compressor may be used to accomplish the compression phase of a gas orvapourcycle engine and the expander to accomplish the expansion phase.

The compressor gets its power directly from the expander via shafts 9 and 10. Excess power is taken out via one or more of shafts 15, 16, 17 or 18.

High pressure gas orvapour is supplied to expander 12 at inlet port 19. After expansion the reduced pressure gas or vapour leaves via outlet port 20.

Power is supplied to compressor 1 via shafts 9 and 10 or15 or16. Gas orvapouris drawn into compressor 1 via port 21 and the compressed gas or vapour leaves via port 22.

1. Ascrewtype gas compression and expansion machine comprising a gas expander unit with its two rotors directly coupled respectively to the two rotors ofthe gas compression unitsuch that the positional control ortiming function of the expander unit rotors is carried out by the same means as that which positionally controls or times the gas compressor unit rotors.

2. A screw type gas compression/expansion unit as in claims 1 wherebythetiming function for both expander and compressor rotors is carried out by one pairoftiming gears.

3. Ascrewtype gas compression/expansion unit as in claim 1 whereby the timing function is integral within the compressor units own rotor meshing via rotorto rotor contact in the presence of lubricant.

4. A screw type gas compression/expansion unit as in claim I wherebythetimingfunction is integral within the compressor units own rotor meshing via rotorto rotor contact in the absence of lubricant.

5. Ascrewtypegas compression/expansion unit as in claims 2,3 and 4 in which more than one expander unit is direct coupled to the compressor unit.

6. A screw type gas/compression/expansion unit as in claims 2, 3,4and 5 in which more than one compressor unit is used.

7. A screw type gas compression/expansion unit as in claims 1,2,3,4,5 and 6 in which mechanical power may be fed to or extracted from the unit via a mechanical drive system.

8. A screw type gas compression/expansion unit as in claim 7 in which the mechanical drive system can be decoupled from the unit via an electromagnetic, pneumatic, or other clutch system.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Direct coupled screw rotor expander compressor This invention relates to a direct coupled screw rotor expander compressor. Screw rotor positive- displacement machines for an elastic working fluid are well known both as compressors and expanders. In such machines there is a casing enclosing a working space comprising two intersecting bores having parallel axes and forming a boundary wall fortheworking space, a high pressure and a low pressure end wall disposed perpendicuiarly tothe axes ofthe bores andwith high pressure and low pressure parts. Each bore contains one rotor of a pair of intermeshing rotorsofso called male and female form with helical lands and intervening grooves. Each rotor having a wrap angle of less than 360 . The male rotor formed with convex lands usually has the major portions of each land outside the pitch circle.The female rotor, formedwith concave lands usually has the major portion of each land inside the pitch circle. It is an advantage in compression machines of this type thatwhen running dry i.e. with a gas medium devoid of liquid lubricantthatthe two rotors are kept apart by timing gears in orderto avoid rubbing and seizure of the dry rotor surfaces. The timing gears normally run in a sealed case where they can be lubricated. Alternatively lubricant may be injected into the gas compression space in which case the rotors may be run one against the other. In this case the need for accurate and expensive timing gears is dispensed with. Howeverthe oil must be separated from the gas after compression. When operated as gas expander units it is usually inconvenient to use lubricant in the gas medium and timing gears must be used. According to the present invention there is provided a screwtype gas compression and expansion machine comprising a gas expander unit with its two rotors directly coupled respectively to the two rotors of the gas compression unit such that the positional control ortiming function of the expander unit rotors is carried out by the same means as that which positionally controls or times the gas compressor unit rotors. A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: *Figure 1 shows in perspective the gas compressor rotors coupled directly to the gas expander. *Figure 2 shows in perspective the gas compressor rotors and gas expander rotors within their respective casings and also show the gas flows. Referring to the drawings the gas compressor 1 has a casing 2 a male rotor3 and afemale rotor4 controlled so asto run ata small butfinite clearance to oneanotherbytiming gears5and 6via shafts7 and 8. The gas expander 11 has a casing 12 and male rotor 13 coupled directly to compressor rotor3 and afemale rotor 14 coupled directly to compressor rotor 4 via shafts9and10.Therotors13and140fthegas expanderarethus also controlled to run at a small but finite clearance to one another by timing gears 5 and 6. The compressor may be used to accomplish the compression phase of a gas orvapourcycle engine and the expander to accomplish the expansion phase. The compressor gets its power directly from the expander via shafts 9 and 10. Excess power is taken out via one or more of shafts 15, 16, 17 or 18. High pressure gas orvapour is supplied to expander 12 at inlet port 19. After expansion the reduced pressure gas or vapour leaves via outlet port 20. Power is supplied to compressor 1 via shafts 9 and 10 or15 or16. Gas orvapouris drawn into compressor 1 via port 21 and the compressed gas or vapour leaves via port 22. CLAIMS

1. Ascrewtype gas compression and expansion machine comprising a gas expander unit with its two rotors directly coupled respectively to the two rotors ofthe gas compression unitsuch that the positional control ortiming function of the expander unit rotors is carried out by the same means as that which positionally controls or times the gas compressor unit rotors.

2. A screw type gas compression/expansion unit as in claims 1 wherebythetiming function for both expander and compressor rotors is carried out by one pairoftiming gears.

3. Ascrewtype gas compression/expansion unit as in claim 1 whereby the timing function is integral within the compressor units own rotor meshing via rotorto rotor contact in the presence of lubricant.

4. A screw type gas compression/expansion unit as in claim I wherebythetimingfunction is integral within the compressor units own rotor meshing via rotorto rotor contact in the absence of lubricant.

5. Ascrewtypegas compression/expansion unit as in claims 2,3 and 4 in which more than one expander unit is direct coupled to the compressor unit.

6. A screw type gas/compression/expansion unit as in claims 2, 3,4and 5 in which more than one compressor unit is used.

7. A screw type gas compression/expansion unit as in claims 1,2,3,4,5 and 6 in which mechanical power may be fed to or extracted from the unit via a mechanical drive system.

8. A screw type gas compression/expansion unit as in claim 7 in which the mechanical drive system can be decoupled from the unit via an electromagnetic, pneumatic, or other clutch system.