Screw compressor with adjustable passages

Abstract

The screw compressor includes an outlet housing. The outlet housing includes a channel configured to transfer compressed fluid from the screw rotor to a discharge portion. A removable cover plate is configured to cover a portion of the channel. A method of varying a volume index for a screw compressor is also disclosed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 911,592, filed on October 7, 2019, the disclosure of which is incorporated herein by reference in its entirety. Background Art

[0003] Screw compressors typically include multiple rotating rotors, each with an external screw thread. The screw threads cooperate with the screw threads on the other rotors to define a compression chamber. The trapped fluid is compressed and transported toward a downstream location. The compressed fluid is transported to a discharge plenum.

[0004] Screw compressors can be operated at various pressure ratios (eg, the ratio of the pressure of the fluid at the inlet of the compressor to the pressure of the fluid at the outlet of the compressor). Various parameters in the screw compressor can be optimized based on the desired pressure ratio. Summary of the invention

[0005] The screw compressor according to an exemplary embodiment of the present disclosure includes, among other possible components, an outlet housing. The outlet housing includes a passage configured to transfer compressed fluid from the screw rotor to a discharge portion. A removable cover plate is configured to cover a portion of the passage.

[0006] In another example of the foregoing, the portion of the channel includes at least one sub-portion. The cover plate includes a first support and a second support coupled by a bracket, and each of the first support and the second support covers the first sub-portion and the second sub-portion of the at least one sub-portion.

[0007] In additional examples of any of the foregoing, each of the first and second struts has a thickness corresponding to a side of the first subsection and a side of the second subsection, respectively.

[0008] In any additional example of the foregoing, the first leg and the second leg each have a first side adjacent to the bracket and a second side opposite the first side. The cover plate includes an open edge between the second side of the first leg and the second side of the second leg.

[0009] In additional examples of any of the foregoing, the cover plate is attached to the outlet housing by one or more removable fasteners.

[0010] In any additional example of the foregoing, the cover plate is a first cover plate configured to cover a first portion of the channel. The first cover plate is interchangeable with a second cover plate configured to cover a second portion of the channel.

[0011] In further examples of any of the foregoing, the first portion of the channel is a different size than the second portion of the channel.

[0012] In additional examples of any of the foregoing, the two screw rotors are configured to compress a fluid.

[0013] In further examples of any of the foregoing, the channel includes a rotor swept surface, and the cover plate reduces an effective length of the rotor swept surface.

[0014] A method of varying a volume index for a screw compressor according to an exemplary embodiment of the present disclosure includes, among other possible actions, providing a removable cover plate for an outlet housing of a screw compressor. The outlet housing includes a channel configured to transfer a compressed fluid from a screw rotor to a discharge portion. The cover plate is configured to cover a portion of the channel.

[0015] In another of the foregoing examples, the removable cover is selected from a group of removable cover panels.

[0016] In further examples of any of the foregoing, a desired volume index for the screw compressor is selected, and a removable coverplate from the group of removable coverplates is selected based on the desired volume index.

[0017] In any additional example of the foregoing, the removable cover is configured to cover a portion of the channel. The size of the portion corresponds to a desired volume index.

[0018] In additional examples of any of the foregoing, the removable cover is a first removable cover in a group of cover and includes interchanging the removable cover with a second cover from the group of cover.

[0019] In additional examples of any of the foregoing, the first removable cover is configured to cover a first portion of the channel, and the second cover is configured to cover a second portion of the channel, and the first portion has a different size than the second portion.

[0020] In any additional example of the foregoing, the portion of the channel includes at least one sub-portion. The cover includes a first support and a second support connected by a bracket. Each of the first support and the second support covers a first sub-portion and a second sub-portion of the at least one sub-portion.

[0021] In additional examples of any of the foregoing, each of the first and second struts has a thickness corresponding to a side of the first subsection and a side of the second subsection, respectively.

[0022] In any additional example of the foregoing, the first leg and the second leg each have a first side adjacent to the bracket and a second side opposite the first side. The cover plate includes an open edge between the second side of the first leg and the second side of the second leg.

[0023] In additional examples of any of the foregoing, the cover plate is attached to the outlet housing by one or more removable fasteners.

[0024] In further examples of any of the foregoing, the channel includes a rotor swept surface, and the cover plate reduces an effective length of the rotor swept surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 An exemplary screw compressor is schematically shown.

[0026] Figure 2A-2B An exemplary outlet casing for a screw compressor is schematically shown.

[0027] Figures 3A-3C An exemplary cover plate for the outlet housing of FIG. 2 is schematically shown. DETAILED DESCRIPTION

[0028] exist Figure 1 An exemplary screw compressor 20 is schematically illustrated in FIG. The compressor housing 22 carries the screw rotors 24 / 26. Figure 1 Two screw rotors 24 / 26 are shown, but more or fewer screw rotors may be used. The screw rotors 24 / 26 have threads or lobes that cooperate to compress the fluid and drive the fluid toward a discharge 38. The fluid enters at the opposite end through an inlet 39. The rotors 24 / 26 each have a shaft 30 mounted in a bearing assembly 32. The bearing assembly 32 extends into a chamber 34 in an outlet housing 36.

[0029] The outlet housing 36 includes a passage 40 that communicates with the discharge portion 38 and is used to convey the compressed fluid downstream. The discharge housing 46 includes a chamber 50 that communicates with the passage 40.

[0030] Now go to Figure 2A-2B , an exemplary outlet housing 136 is shown. In this example, the outlet housing 136 includes a housing that receives and engages with the screw rotors 24 / 26 ( Figure 1 ) two chambers 134 for the bearings 32 corresponding to each other. Although this example shows two chambers 134 corresponding to the two screw rotors 24 / 26, more or fewer chambers 134 / screw rotor may be used depending on the number of screw rotors.

[0031] The channel 140 is configured to communicate with the discharge portion 38 as discussed above and to deliver the compressed fluid to the downstream discharge portion. In this example, the channel 140 has a radial outer edge 140a with an arcuate shape. The radial outer edge 140a joins the radial inner edge, which defines a rotor swept surface 140b. The rotor swept surface 140b is defined by two side portions 140d, 140e. In one example, the side portions 140d, 140e are non-straight. In a specific example, the left side portion 140d is convex relative to the center of the channel 140, and the right side portion 140e is concave relative to the center of the channel 140. The rotor swept surface 140b has a length L defined between the side portions 140d and the side portions 140e. When the fluid flow leaves the discharge chamber 38, the rotor swept surface 140b maintains the fluid flow in a compressed state. Sidewall 140D and sidewall 140E have curved profiles that generally follow the shape of the lobes of the screw rotors 24 / 26 at the discharge 38. Sidewall 140D is convex and sidewall 140E is concave because one of the rotors 24 / 26 is male and the other of the rotors 24 / 26 is female so that when the lobes of these rotors 24 / 26 open to the discharge 38, the walls of the lobes of the rotors 24 / 26 at the discharge 38 follow their respective curvatures. In this example, rotor 24 is male and rotor 26 is female. In this example, the central portion 140c of the radially inner edge 140b protrudes downwardly into the space between the chambers 134 in a "W" shape (which is also called a "butterfly" shape) at the radially innermost edge. However, other profiles are contemplated.

[0032] The length L of the rotor swept surface 140b and the resulting cross-sectional area of ​​the passage 140 are related to the volume index of the screw compressor 20. The volume index is the ratio of the volume of fluid trapped between the screw rotors 24 / 26 at the beginning of the compression process (e.g., near the inlet 39) to the volume of fluid trapped between the screw rotors 24 / 26 when the screw rotors 24 / 26 are open to the discharge 38. Changing the length L and thus changing the cross-sectional area of ​​the passage 140 changes the volume index of the screw compressor 20 by changing the volume of fluid trapped between the screw rotors 24 / 26 when the screw rotors 24 / 26 are open to the discharge 38.

[0033] The pressure ratio of the screw compressor 20 is the ratio of the pressure of the fluid at the inlet 39 to the pressure of the fluid at the discharge chamber 38. For a given pressure ratio, there is a volume index that maximizes the efficiency of the screw compressor 20.

[0034] Figure 3A-3B The outlet housing 136 is shown with a removable or interchangeable cover plate 200 . Figure 3CThe cover plate 200 is shown alone. The cover plate 200 is attached to the outlet housing 136 via removable fasteners 202, such as screws or another type of fastener. In the example shown, there are four fasteners 202, but more or fewer fasteners may be used.

[0035] The cover plate 200 has an open area 204 corresponding to the effective cross-sectional area of ​​the passage 140 when the cover plate 200 is installed. The cover plate 200 covers a portion of the passage 140, so that the effective cross-sectional area of ​​the passage 140 is reduced, and thus the volume index for the screw compressor 20 is increased. Figures 3A-3C In the example of FIG. 1 , the cover plate includes two posts 206a, 206b on either side of the opening 204. The posts 206a, 206b are connected by a bracket 208 at a first end of each post 206a, 208a. Each of the posts 206a, 206b covers a sub-portion P of the channel 140 on either side of the channel 140 (at Figure 3B ). The top (radially outer) edge of the opening 204 is rectangular in shape, however, other shapes are contemplated.

[0036] The cover plate 200 has an open edge between the second ends of the pillars 206a, 206b, which second ends are opposite to the ends of the pillars 206a, 206b coupled by the bracket 208. In addition, the second end of each pillar 206a, 206b includes a divot 210a, 210b, respectively. The shape of the divot corresponds to the shape of the side portions 140d, 140e of the channel 140 (in Figure 2A-2B ). Thus, the shape or profile of the rotor swept surface 140b is maintained, and only the effective length Le of the rotor swept surface is changed by the cover plate 200.

[0037] Each of the pillars 206a, 206b has a thickness t( Figure 3C ), the thickness t corresponds to the sub-portion P (in Figure 3B The greater the thickness t of the pillars 206a, 206b, the greater the cumulative portion of the passage 140 that is covered (e.g., the sum of the sub-portions P), the smaller the effective length Le of the rotor swept surface 140b, and the smaller the effective cross-sectional area of ​​the passage 140. Therefore, the greater the thickness t, the greater the volume index of the screw compressor 20.

[0038] The exemplary cover plate 200 is part of a group of cover plates 200. The cover plates 200 in the group may have different thicknesses t for the respective struts 206a, 206b. All of the cover plates 200 in the group are removable, meaning that they may be removed and / or interchanged with other cover plates 200 in the group to vary the effective length Le of the rotor swept surface and the cross-sectional area of ​​the channel 140. In this way, the volume index for the screw compressor 20 may be varied. As discussed above, the cover plate 200, and thus the volume index, may be selected to maximize efficiency for a given pressure ratio for the screw compressor 20.

[0039] Although the various examples are illustrated as having specific components, the examples of the present disclosure are not limited to those specific combinations. It is possible to use some components or features from any embodiment in combination with features or components from any other embodiment.

[0040] The foregoing description should be interpreted as illustrative and not interpreted in any restrictive sense. Those of ordinary skill in the art will appreciate that certain modifications may fall within the scope of the present disclosure. For these reasons, the following claims should be studied to determine the true scope and content of the present disclosure.

Claims

1. A screw compressor, comprising: an outlet housing including a passage configured to transfer compressed fluid from the screw rotor to a discharge; as well as a removable cover plate configured to cover a portion of the channel, wherein the removable cover plate includes at least one segment, and wherein the removable cover plate reduces an effective length of the rotor swept surface and the at least one segment maintains a profile of the rotor swept surface; wherein the portion of the channel comprises at least one sub-portion, and wherein the cover plate comprises a first support and a second support coupled by a bracket, and wherein each of the first support and the second support covers a first sub-portion and a second sub-portion of at least one sub-portion.

2. The screw compressor according to claim 1, wherein: Each of the first and second pillars has a thickness, and wherein the thickness corresponds to a side of the first subsection and a side of the second subsection, respectively.

3. The screw compressor according to claim 1, wherein: The first and second legs each have a first side adjacent to the bracket and a second side opposite the first side, and wherein the cover plate includes an open edge between the second side of the first leg and the second side of the second leg.

4. The screw compressor according to claim 1, wherein: The cover plate is attached to the outlet housing by one or more removable fasteners.

5. The screw compressor according to claim 1, wherein: The cover plate is a first cover plate configured to cover a first portion of the channel, and wherein the first cover plate is interchangeable with a second cover plate configured to cover a second portion of the channel.

6. The screw compressor according to claim 5, wherein: The first portion of the channel is a different size than the second portion of the channel.

7. The screw compressor of claim 1, further comprising two screw rotors configured to compress the fluid.

8. The screw compressor according to claim 1, wherein: The channel includes a rotor swept surface, and the cover plate reduces the effective length of the rotor swept surface.

9. A method of varying a volume index for a screw compressor, comprising: Providing a removable cover plate for an outlet housing of a screw compressor, the outlet housing including a passage configured to transfer compressed fluid from a screw rotor to a discharge, the cover plate configured to cover a portion of the passage, wherein the removable cover plate includes at least one segment, and wherein the removable cover plate reduces an effective length of the rotor swept surface, and the at least one segment maintains a profile of the rotor swept surface; wherein the portion of the channel comprises at least one sub-portion, and wherein the cover plate comprises a first support and a second support coupled by a bracket, and wherein each of the first support and the second support covers a first sub-portion and a second sub-portion of at least one sub-portion.

10. The method of claim 9, further comprising selecting the removable cover from a group of removable cover.

11. The method according to claim 10, further comprising: Selecting a desired volume index for the screw compressor; and selecting the removable coverplate from the group of removable coverplates based on the desired volume index.

12. The method according to claim 11, wherein: The removable cover is configured to cover a portion of the channel, and the size of the portion corresponds to the desired volume index.

13. The method according to claim 10, wherein: The removable cover plate is a first removable cover plate in the group of cover plates, and further comprising interchanging the removable cover plate with a second cover plate from the group of cover plates.

14. The method according to claim 13, wherein: The first removable cover is configured to cover a first portion of the channel, and the second cover is configured to cover a second portion of the channel, and the first portion has a different size than the second portion.

15. The method according to claim 9, wherein: Each of the first and second pillars has a thickness, and wherein the thickness corresponds to a side of the first subsection and a side of the second subsection, respectively.

16. The method according to claim 9, wherein: The first and second legs each have a first side adjacent to the bracket and a second side opposite the first side, and wherein the cover plate includes an open edge between the second side of the first leg and the second side of the second leg.

17. The method of claim 9, further comprising attaching the cover plate to the outlet housing via one or more removable fasteners.

18. The method according to claim 9, wherein: The channel includes a rotor swept surface, and the cover plate reduces the effective length of the rotor swept surface.

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