Unequal injection ports for scroll compressors

Details Unequal injection ports for scroll compressors Unequal injection ports for scroll compressors

1999-04-12

2001-03-06

Denion, Thomas (Department: 3748)

Rotary expansible chamber devices

Working member has planetary or planetating movement

Helical working member, e.g., scroll

C418S097000

Reexamination Certificate

active

06196816

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to the optimization of the size and/or location of injection ports for use in scroll compressors.
Scroll compressors are becoming widely utilized in refrigerant compression applications. Scroll compressors are generally formed of an orbiting and a non-orbiting scroll member. Both of the scroll members have spiral wraps extending from their respective base plates. The spiral wraps of orbiting and non-orbiting members interfit to define compression chambers. Typically, at least two compression chambers are being moved concurrently towards a discharge port compressing the refrigerant.
One compressor feature which has been used in scroll compressors and has increased the efficiency of the overall refrigerant system is an economizer cycle. An economizer cycle provides thermodynamic benefits as a supplemental fluid is injected into the scroll compressor compression chambers at a position downstream of the suction inlet.
In addition to economizer cycle or as a stand alone feature an unloader valves can also be incorporated into scroll compressors design to selectively by-pass the refrigerant from a more compressed location back to a less compressed location.
With either an economizer cycle, and/or with an unloader valve, there is an injection port for each of the two compression chambers. Thus, in known scroll compressors there has typically been a pair of injection ports associated with either the economizer cycle or by-pass operation utilizing the unloader valve.
The injection ports are usually formed through the non-orbiting scroll, and they have both been of an equal cross-sectional area, equal depth, located at equal angular position in each compression chamber with respect to suction chamber seal off point.
The use of equal injection ports has created some inefficiencies and concerns. As an example, there may be unequal pressure drops in the connecting lines leading to each of the ports due to differences in the line geometries.
Also unequal flow may occur due to the use of so-called hybrid profiles for the scroll wraps. Scroll wraps once had an essentially uniform thickness throughout their entire wrap. More recently, scroll wraps have been optimized to have a varying thickness along a wrap. Thus, a scroll wrap portion associated with one injection port may have a very different thickness than a scroll wrap portion associated with the other. The different thickness could then change the amount of time that each of the ports is uncovered by the orbiting scroll wrap.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, the two injection ports are formed to be unequal, and/or be positioned at different angular positions in each compression chamber with respect to suction chambers seal off point to achieve desired design characteristics. As one example, the two injection ports can be of different cross-sectional areas, including width, depth or length. In this way, the scroll designer is able to tailor the flow through the two injection ports to achieve an optimum flow into each compression chamber.
The exact size and position of the two injection ports is preferably tailored to achieve an approximately balanced mass flow of fluid to each of the compression chambers, although in some applications it may be unbalanced flow which is sought by the designer. By providing an approximately balanced amount of refrigerant injection into each chamber, pressure in each compression chamber remains to be equal and thus mixing losses which occur when two chambers merge that may have occurred in the prior art are eliminated. Further, pulsation and sounds due to unequal pressure in compression chambers are reduced.
With the present invention, a scroll compressor designer determines the optimum size (width, length and depth) of the port, and also an optimum location. By doing this, the design of the two injection ports is selected to achieve desired characteristics. The size, position, etc. can be determined experimentally or analytically. It is the use of differently sized or positioned ports which is inventive.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.


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