Compressor and a method for compressing fluid

A compressor and a method for compressing fluid according to which a liner is disposed on the inner wall of a housing defining a bore. At least one slot and at least one discharge port are provided in the liner. A rotor is rotated in the housing with its outer surface in a closely spaced relation to the inner wall of the liner, and an additional rotor extends through the slot in the liner and intermeshes with the first rotor to compress fluid introduced between the rotors before it is discharged through the port.

BACKGROUND

This invention is directed to a compressor, such as a rotary screw compressor, for compressing a fluid, such as air.

Screw compressors use two or more intermeshing rotors, each provided with helical lobes to produce compression when the rotors are rotated. A fluid, such as air, is introduced into the compressor and is trapped between the rotors and compressed to the required discharge pressure.

However, these compressors are expensive to manufacture since they are provided with windows, slots, ports, passages, and the like, which are formed by fairly intricate castings and weldments. Also, when it is desired to change the operating parameters of the compressor, such as its discharge pressure, flow rate, and capacity, the housing has to be replaced with a new cast housing having a different arrangement of windows, slots, ports, passages, and the like, which adds to the expense.

Therefore, what is needed is a compressor of the above type that eliminates, or at least reduces, these problems.

DETAILED DESCRIPTION

Referring toFIG. 1of the drawing, a screw compressor according to an embodiment of the invention is referred to, in general, by the reference numeral10. The compressor10includes a housing12, preferably formed of a forged billet and having a series of openings, bores, and chambers formed therein as will be described. A drive shaft14is supported in a longitudinal through bore12aformed in the housing by a pair of axially spaced bearing assemblies16and18which are supported in the housing by two carriers20and22, respectively, that are mounted in the bore. It is understood that the shaft14is connected to a driver, such as an electric motor, for rotating the shaft.

A rotor24is supported on the shaft14for rotation therewith, extends in the above bore12a, and will be described in detail later. A cylindrical liner26is affixed to the inner surface of the housing12defining the bore12a, and is very slightly spaced from the outer surface of the rotor24. The rotor24and the liner26will be described in detail later.

A cover28is bolted over one end of the housing12and has a through opening in alignment with an opening formed in the carrier22to define an inlet30for a fluid, such as air, to be compressed. A passage22ais formed in the carrier22that connects the inlet30to the bore12a. A cover32extends over the other end of the housing12and has a through opening that receives a portion of the bearing16. A radially extending discharge passage34is formed through the housing12for discharging the compressed fluid to external equipment.

A seal36extends adjacent the bearing16and around the shaft14to seal against the egress of the fluid from the bore12a. One end of a drain passage38extends from the bore12anear the seal36, through the carrier20, and is vented to a collection point. A radially extending drain connection42also extends from the bore12athrough the housing12.

The liner26is shown in detail inFIG. 2and includes an elongated, variable-width, slot26aextending through a wall portion of the liner, along with a discharge port26bin a slightly spaced relation to the slot. Although only one slot26aand discharge port26bare shown, it is understood that another slot26aand discharge port26bare formed through the liner26in a diametrically opposed relation to the slot26aand discharge port26bshown inFIG. 2. It is also understood that the discharge ports26bare connected by internal passages2(one shown) in the housing12to the discharge passage34. The liner26is interchangeable, e.g., it can be replaced by a different liner, it can be used to replace a different liner, or it can be added to a compressor that was initially designed without a liner.

Referring toFIG. 3, a gate rotor assembly50is located in a chamber formed in the housing12to one side of the shaft14and the main rotor24, with the axis of the assembly extending transverse to the axis of the rotor. The assembly50includes a cylindrical support54having an annular flange54aextending therefrom. A shaft56extends through the support54and the lower end portion of the shaft56, as viewed inFIG. 3, projects from the corresponding lower end of the support54, through a thrust bearing58and a thrust washer60, and into a cover62bolted to the housing12. The other end portion of the shaft56projects from the upper end of the support54and extends into a cover64affixed to the housing12, to permit rotation of the assembly50in the housing12.

An annular gate rotor66is affixed to the upper surface of the flange54a, and extends, with the flange, through one of the slots26aformed through the liner26, so as to mesh with the main rotor24. Rotation of the main rotor24thus causes corresponding rotation of the gate rotor66for reasons to be described.

Another gate rotor assembly70is provided on the opposite side of the main rotor24, is inverted when compared to the gate rotor assembly50, and includes a rotor72which extends through the other slot26aof the liner26and also meshes with the main rotor24. Since the gate rotor70is identical to the gate rotor assembly50, it will not be described in detail.

As shown inFIG. 4the main rotor24has a plurality of lobes24awhich engage corresponding lobes66aand72aformed on the gate rotors66and72, respectively, so that rotation of the rotor24causes a successive intermeshing with the lobes24aand the lobes66aand72aand thus compresses fluid introduced between the lobes, in a manner to be described.

FIGS. 5A,5B, and5C depict the above compression in various stages of operation. In particular, the shaft14, and therefore the rotor24, is rotated, which causes corresponding rotation of the gate rotors66and72. Fluid, such as air, enters the compressor10via the inlet30(FIG. 1) and passes though the passage22a, into the bore12aand through the slots26a(FIGS. 1 and 2) in the liner26. The fluid then fills the screw grooves defined by the lobes24aof the main rotor24, as shown inFIG. 5A. As the rotors24,66, and72rotate further, lobes66aand72aof the gate rotors66and72, respectively, enter the latter screw grooves, trapping the air, and actual air compression begins, as shown inFIG. 5B. As the rotation continues, the trapped air is compressed as the length and the volume of each groove is reduced. When the main rotor24rotates far enough, each groove passes the discharge ports26b(FIG. 2) of the liner26, thus delivering the compressed air to the discharge passage34, via the above-mentioned internal passages in the housing12, for delivery to external equipment, such as a discharge manifold, or the like.

Also, since the shape and/or location of the slots26aand the discharge ports26bof the liner26dictate the operating parameters of the compressor, including its discharge pressure, flow rate, and capacity, these parameters can be changed by simply replacing the liner26with another liner having slots and/or discharge ports of a different shape and/or location. Thus, a compressor system could consist of the compressor10, and two or more liners similar to the liner26, with the location and size of the slots and/or discharge ports of each liner being designed for a particular different application of the system. Also, an existing compressor that does not have a liner can be fitted with a liner similar to the liner26with the slots and discharge ports being designed for the specific desired operating parameters.

As a result, there is provided a simple, easy, and cost-effective technique of varying the operating parameters of the compressor without having to resort to providing a relatively expensive new housing having formed windows, slots, ports, and passages formed therein to achieve the operating parameters. Even if only one liner is used, it also can be appreciated that the liner reduces the number and depth of the passages and ports that must be formed in the housing to achieve the desired flow characteristics.

Although not shown in the drawings, it is understood that the compressor10can be provided with a water injection system that supplies a continuous flow of cool filtered water to the compressor. This water is injected into the air stream as the air passes through the compressor10and is compressed in the above-described manner. The water mixes with the air and the mixture discharges from the compressor10, via the discharge passage34, to a separator (not shown) where the water is removed and collected. The pressure of the compressed air in the separator provides the force to circulate the water through the water injection system and inject it into the compressor10.

It is understood that variations may be made in the foregoing without departing from the scope of the invention. For example, the invention is not limited to a screw compressor, but is equally applicable to any type of rotary machine having two intermeshing rotors. Also, any number of gate, or secondary, rotors that engage the main rotor can be utilized. Also spatial references, such as “upward”, “downward”, “vertical”, etc., are for the purpose of illustration only and also do not limit the specific orientation or location of the structure described above.

Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many other modifications are possible in these embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.