Pumps – Successive stages – With interstage intake or additional inlet to latter stage
Patent
1998-05-01
2000-09-05
Freay, Charles G.
Pumps
Successive stages
With interstage intake or additional inlet to latter stage
418 15, 418 551, 418 5, F01C 102, F04B 300
Patent
active
061133582
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a gas compressor of the kind using two intermeshed involute scrolls one of which remains stationary and the and the other of which orbits (but does not rotate) about the first scroll. By appropriate sizing of the scrolls and proper movement of one relative to the other, two gas chambers are first opened on diametrically opposite sides of the intermeshed scrolls, these chambers then grow in size until they are closed as "C" shaped pumping chambers which progress symmetrically on diametrically opposite sides of the center of the stationary scroll towards that center reducing in volume as they so progress. On reaching the center, the gas trapped in each chamber when it first closed, has been compressed to a higher pressure and is released from the chamber to the exhaust duct of the compressor. A compressor of this type will herein be referred to as a "scroll compressor" and a pair of gas chambers of one or more scroll compressors ganged together as described in the following paragraph will be referred to as "a scroll compressor arrangement of the kind specified".
For operating a scroll compressor in accordance with the method of this invention it is necessary for the compressor to have at least two "C"-shaped pumping chambers of variable volume, each of which receives fluid to be compressed from a primary inlet when the respective pumping chamber has a first volume at least close to its maximum volume and each of which discharges compressed fluid from an outlet when the respective pumping chamber has a second volume which is less than said first volume, one of said pumping chambers having a secondary inlet open to the said one chamber when it has a third volume intermediate the first and second volumes after said chamber is closed off from its primary inlet but before the said one chamber opens to its outlet.
The invention seeks to improve the efficiency of a scroll compressor arrangement of the kind specified particularly in its application to refrigeration.
The method of the invention may be practiced using two separate scroll compressors one of which provides the first "C"-shaped pumping chamber and the other compressor of which provides the second "C"-shaped pumping chamber. The invention may also be applied to a composite compressor arrangement where the at least two "C"-shaped chambers of varying volume are provided in a common casing.
DISCUSSION OF PRIOR ART
It is known to improve the efficiency of a compression refrigeration system if refrigerant gas is also allowed to enter a pumping chamber via an intermediate port (sometimes called herein an "economiser port"). As the economiser port is open to an intermediate stage of the compression process, for gas to enter the economiser port it must be at a higher pressure than the suction pressure. This is traditionally achieved by the use of an economiser vessel/heat exchanger and its associated control valves and pipework.
The operating principle behind the use of an economiser vessel/heat exchanger (sometimes referred to as "superfeed") is that liquid refrigerant is boiled off in the economiser vessel or heat exchanger at a pressure lower than the delivery pressure but higher than the suction pressure. The gas evolved from the vessel or heat exchanger is returned to the economiser port of the compressor arrangement whilst the liquid subcooled in the economiser vessel is led to the suction evaporator. This liquid subcooling increases the refrigeration capacity of the system. In addition, as the vapor evolved in the economiser vessel or heat exchanger is returned to the compressor arrangement at an intermediate pressure, less power is required to compress this vapor than if it were returned to the compressor arrangement at the suction pressure, thus effecting further economies.
SUMMARY OF THE INVENTION
According to one aspect of this invention a method of operating a scroll compressor arrangement of the kind specified is characterized in that the outlet of the other pumping chamber is fed to the secondary inle
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Roll John Michael
Young Terence William Thomas
AAF - McQuay Inc.
Evora Robert Z.
Freay Charles G.
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