Patent Application
20050223726
(1) Field of the Invention
The invention relates to compressors, and more particularly to screw-type compressors.
(2) Description of the Related Art
Screw-type compressors are commonly used in air conditioning and refrigeration applications. In such a compressor, intermeshed male and female lobed rotors or screws are rotated about their axes to pump the working fluid (refrigerant) from a low pressure inlet end to a high pressure outlet end. During rotation, sequential lobes of the male rotor serve as pistons driving refrigerant downstream and compressing it within the space (compression pocket) between an adjacent pair of female rotor lobes and the housing. Likewise sequential lobes of the female rotor produce compression of refrigerant within a male rotor compression pocket between an adjacent pair of male rotor lobes and the housing. In one implementation, the male rotor is coaxial with an electric driving motor and is supported by bearings on inlet and outlet sides of its lobed working portion. There may be multiple female rotors engaged to a given male rotor or vice versa. With such a compressor, male and female compression pockets may also have multiple inlet and outlet ports.
When a compression pocket is exposed to an inlet port, the refrigerant enters the pocket essentially at suction pressure. As the pocket continues to rotate, at some point during its rotation, the pocket is no longer in communication with the inlet port and the flow of refrigerant to the pocket is cut off. Typically the inlet port geometry is arranged in such a way that the flow of refrigerant is cut off at the time in the cycle when the pocket volume reaches its maximum value. Typically the inlet port geometry is such that both male and female compression pockets are cut off at the same time. The inlet port is typically a combination of an axial port and a radial port. After the inlet port is closed, the refrigerant is compressed as the pockets continue to rotate and their volume is reduced. At some point during the rotation, each compression pocket intersects the associated outlet port and the closed compression process terminates. Typically outlet port geometry is such that both male and female pockets are exposed to the outlet port at the same time. As with the inlet port, the outlet port is normally a combination of an axial port and a radial port. By combining axial and radial ports into one design configuration, the overall combined port area is increased, minimizing throttling losses associated with pressure drop through a finite port opening area. In an exemplary three-rotor configuration, the inlet and outlet ports are respectively formed at common inlet and outlet plenums.
The compressor may be designed and sized for its intended use (e.g., to provide a given compression or volume index and operate at a given flow at a given speed or combination thereof). Different compressors or at least different components (rotors, motors, and the like) may be required for different uses.
One aspect of the invention involves an apparatus comprising: a first rotor enmeshed with second rotors. The rotors are held within a housing for rotation about respective first, second, and third axes. The housing has: a first surface cooperating with the first and second rotors to define a first inlet port; a second surface cooperating with the first and second rotors to define a first outlet port; a third surface cooperating with the first and third rotors to define a second inlet port; and a third surface cooperating with the first and third rotors to define a second outlet port. Either the first and second inlet ports are at a different pressure or the first and second outlet ports are at a different pressure.
In various implementations, the apparatus may further include: a first condenser; a first evaporator; and one or more first conduits coupling the first condenser and the first evaporator to the housing to define a first flowpath from the first outlet port through the first evaporator and first condenser and to the first inlet port. The apparatus may further include: a second condenser; a second evaporator; and one or more second conduits coupling the second condenser and the second evaporator to the housing to define a second flowpath from the second outlet port through the second evaporator and second condenser and to the second inlet port.
The first outlet port may be at the same pressure as the second inlet port. The apparatus of may further include a first condenser, a first expansion device, and a first evaporator. One or more first conduits may couple the first condenser, the first expansion device and the first evaporator to the housing to define a first flowpath from the second outlet port to the first inlet port. There may be no economizer branches off the first flowpath. There may be an economizer heat exchanger having a first leg along the first flowpath and a second leg, in heat exchange relation with the first leg. The second leg may be along a diversion flowpath from a location along the first flowpath between the first condenser and the first leg to join a second flowpath from the first outlet port to the second inlet port.
Either the first and second inlet ports may form a common inlet port or the first and second outlet ports may form a common outlet port. Either the first and second inlet ports may be at like pressure or the first and second outlet ports may be at like pressure. The first rotor may be a male rotor and the second and third rotors may be female rotors
Another aspect of the invention involves an apparatus comprising a first rotor enmeshed with second and third rotors. The rotors are held within a housing for rotation about respective first, second, and third axes. Means cooperate with the first, second, and third rotors for providing: a first volume index associated with interaction of the first and second rotors when the first rotor is driven in the first direction; and a second volume index associated with interaction of the first and third rotors when the first rotor is driven in the first direction. The second volume index is different from the first volume index.
In various implementations, the apparatus may be combined with first and second refrigerant flows along non intersecting first and second flowpaths through the apparatus. T he apparatus may be combined with first and second refrigerant flows along first and second flowpaths through the apparatus intersecting at a suction side of the apparatus. The apparatus may be combined with first and second refrigerant flows along first and second flowpaths through the apparatus intersecting at a discharge side of the apparatus.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Like reference numbers and designations in the various drawings indicate like elements.
In the exemplary embodiment, the motor 24 is an electric motor having a rotor and a stator. A portion of the first shaft stub 39 of the male rotor 26 extends within the stator and is secured thereto so as to permit the motor 24 to drive the male rotor 26 about the axis 500. When so driven in an operative first direction about the axis 500, the male rotor drives the female rotors in opposite directions about their axes 501 and 502.
Surfaces of the housing combine with the enmeshed rotor bodies to define inlet and outlet ports to a two pairs of compression pockets: a first pair of male and female compression pockets formed by the housing, male rotor, and the first female rotor; and a second pair of male and female compression pockets formed by the housing, male rotor and the second female rotor. In each pair, one such pocket is located between a pair of adjacent lobes of each rotor associated rotor. Depending on the implementation, the ports may be radial, axial, or a hybrid of the two.
According to the invention, the compression paths associated with two compression pockets do not meet at one or both of the inlet and outlet ends. In the exemplary embodiment, separate first and second inlet plenums 61 and 62 are respectively associated with the first and second pairs of compression pockets as are first and second outlet plenums 63 and 64. This may be achieved by a simple modification of the housing (e.g. a modification of an actual housing or a modification of the functional design thereof) of a conventional compressor to bifurcate one or both of an initially common suction port and an initially common discharge port. This modification may leave other components (e.g., rotors, motors, and the like) unchanged. More drastic modifications and clean sheet designs are also possible. Reuse of existing designs for varied applications can produce a variety of efficiencies (e.g., economies of scale).
Alternative implementations may involve flowpaths that intersect at one or more individual points or overlap.
In a variation on the basic two-stage system of
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, additional features may be included as are known in the art or are subsequently developed. Accordingly, other embodiments are within the scope of the following claims.
