WO2021074804A1

WO2021074804A1 - Screw compressor

Info

Publication number: WO2021074804A1
Application number: PCT/IB2020/059633
Authority: WO
Inventors: Guido MANAGO'; Alessandro D'AGOSTINO
Original assignee: Daikin applied Europe S.p.A.
Priority date: 2019-10-15
Filing date: 2020-10-14
Publication date: 2021-04-22
Also published as: IT201900018902A1; EP4045798A1

Abstract

A screw compressor (1), comprising: a housing including an inlet port (11, 13) and an outlet port (12); a screw rotor, arranged into the housing; a compression chamber, delimited by the screw rotor and by the housing; a dampening device for dampening vibrations generated by the screw rotor; wherein the dampening device includes: a duct (2) defining a duct internal volume (23); a mesh (6), positioned in the duct internal volume (23), wherein the duct (2) is connected to either one of the inlet port (11, 13) or the outlet port (12).

Description

DESCRIPTION SCREW COMPRESSOR

Technical field

This invention relates to a screw compressor. In particular, this disclosure regards a screw compressor for a refrigeration system.

Background art

Screw compressors commonly include at least a screw rotor, rotatable within a compression chamber; the rotation of the screw rotor generate pulsations propagating in the piping of the refrigeration system upstream or downstream of the compressor. These pulsations cause vibration of the piping, leading to noise and possible sudden break of the piping. In particular, piping which connect economizer heat exchanger to the screw compressor may be subject to high vibrations. Furthermore, also the branches of the system upstream of the suction port of the compressor, and/or downstream of the discharge port of the compressor, may incur in noise and breaking of the piping.

Hence, dampening systems are known, which are provided in the refrigeration system for dampening the pulsations generated by rotation of the screw rotor. Patent document EP2634432A1 discloses a refrigeration system wherein the economizer circuit includes a resonance space, for retaining an intermediate pressure refrigerant, and a resonance passage, having an end communicating with the compression chamber and the other end communication with the resonance space; hence, the resonance space provides a sound attenuation effect which reduces the pressure pulsation of the refrigerant flowing through the economizer circuit. Patent document US2018/0156501 A1 discloses a screw compressor comprising a male and a female screw rotor, and a chamber located upstream of the economizer port of the compressor, the chamber having predetermined volume for dampening the pulsations generated by the male and female screw rotors. Patent document WO2017058369A1 discloses a screw compressor including a group of cavities, functioning as a resonator and being located between the discharge port and the screw rotors. Other screw compressors having dampening systems are disclosed in patent documents BE857230A and EP2199613A2.

Known dampening devices have the drawback that they introduce high pressure drops, leading to an important reduction of the performance of the refrigeration system. Moreover, known dampening devices are calibrated for a certain frequency of vibration; in cases where the screw compressor is provided with an inverter for rotating at variable speed, they barely adapt to a wide range of frequencies of vibration of the compressor. Also, known dampening devices require a complex design.

Disclosure of the invention

Scope of the present invention is to provide a screw compressor and a method for dampening vibrations in a screw compressor which overcome at least one of the aforementioned drawbacks.

This scope is achieved by the screw compressor and the method according to the appended claims.

The present disclosure regards a screw compressor. The screw compressor comprises a housing, or external casing. The housing has an inlet port and an outlet port. The screw compressor comprises a screw rotor arranged into the housing. In particular, the housing has an internal volume, and the rotor is positioned within the internal volume of the housing.

It is observed that the compressor, in one example, is a single screw compressor; in another example, the compressor has two or more screws. The screw compressor comprises a compression chamber, delimited by the screw rotor and by the housing. In particular, the compression chamber is defined by (part of) the internal volume of the housing not occupied by the screw rotor. The screw rotor is rotatable about a rotation axis for compressing a flow of refrigerant fluid (or refrigerant gas), by drawing the flow of refrigerant fluid through the compression chamber, along a flow path within the housing, from the inlet port to the outlet port. Hence, a path for the refrigerant fluid is defined within the housing, from the inlet port to the outlet port; in said path, the refrigerant fluid is moved and compressed by rotation of the screw rotor.

The screw compressor includes a dampening device, configured for dampening vibrations generated by the screw rotor.

According to an aspect of the present disclosure, the dampening device includes a duct, defining a duct internal volume. The duct extends from an inlet opening (or first opening) to an outlet opening (second opening). In detail, the duct is elongated from an inlet end (or first end) to an outlet end (or second end), opposite to the inlet end, and includes the inlet opening at the inlet end, and the outlet opening at the outlet end. A flow of the refrigerant gas through the duct is defined from the inlet end to the outlet end. In an embodiment, the duct is elongated along a first axis and the inlet port and the outlet port are aligned along said axis.

The duct is connected to either one of the inlet port or the outlet port, so that the duct internal volume is in fluid communication with the compression chamber.

In particular, in an embodiment, the outlet opening of the duct is connected to the inlet port, so that the internal volume is in fluid communication with the compression chamber through the inlet port.

In an embodiment, the inlet opening of the duct is connected to the port, so that the internal volume is in fluid communication with the compression chamber through the outlet port.

The dampening device may also include a mesh, positioned in the duct internal volume. Thus, the refrigerant gas at low pressure, entering the compression chamber, or the refrigerant gas has at high pressure, exiting the compression chamber, passes through a duct in which a mesh is arranged; the mesh provides a dissipative effect, which dampens of pressure pulsations generated by rotation of the screw rotor. Hence, the piping of refrigeration circuit upstream of the inlet of the compressor, or downstream of the outlet of the compressor, undergo lower vibrations and, consequently, lower stress, thanks to the mesh.

In particular, the duct internal volume includes a first zone occupied by the mesh and a second zone free (not occupied) by the mesh, the first zone being in fluid communication with the second zone. Hence, the mesh does not fill the whole volume of the duct, leaving a so called second zone free from the mesh, which allows to limit pressure drops in the duct.

Preferably, the second zone extends from the inlet opening to the outlet opening in a central part of the duct; the first zone is positioned in a peripheral part of the duct, externally to the second zone. Preferably, the first zone surrounds the second zone.

For example, the second zone may be shaped as a cylinder elongated along a first axis, from the inlet opening to the outlet opening, and the first zone may be shaped as a hollow cylinder surrounding the second zone. In other words, the first zone may be shaped as a hollow cylinder defining an internal elongated hole, elongated along the first axis of the duct, and the second zone may be formed as a cylinder elongated along the axis of the duct and positioned inside the internal elongated hole of the hollow cylinder.

It is also provided that the dampening device may include a separating wall having a plurality of apertures, being positioned within the duct internal volume, and having a first face, facing the first zone, and a second face, opposite to the first face, facing the second zone. In the example wherein the first zone is formed as a hollow cylinder and the second zone is positioned inside the hole of the hollow cylinder, the separating wall, where provided, will be shaped as a cylindrical tube surrounding the second zone and positioned inside the hole defined by the first zone.

As for the material of the mesh, the mesh may include (or consist in) a metallic knitted wire. In particular, the mesh may be made of stainless steel, or copper, or any other metal. Moreover, the mesh may include (or consist in) glass wool and/or mineral wool, and/or polymeric foam, and/or polymeric fiber, and/or expanded bead material (e.g. expanded polypropylene).

According to an aspect of the present disclosure, the dampening device includes an inner conduit and an outer shell.

The inner conduit has a wall extending from a first opening to a second opening and defining an inner conduit internal volume; the inner conduit is connected to either one of the inlet port or the outlet port, so that the inner conduit internal volume is in fluid communication with the compression chamber. The outer shell surrounds the inner conduit to form, between the inner conduit and the outer shell, a dissipation chamber. The wall of the inner conduit defines a plurality of lateral apertures, so that the inner conduit internal volume and the dissipation chamber are in fluid communication through the plurality of lateral apertures. In other words, the inner conduit has a perforated wall. Hence, the inner conduit may define said separating wall, provided between the first zone and the second zone.

Thus, the refrigerant gas at low pressure, entering the compression chamber, or the refrigerant gas has at high pressure, exiting the compression chamber, passes through a perforated inner conduit, surrounded by an outer shell; the perforated conduit provides a reactive effect, which dampens of pressure pulsations generated by rotation of the screw rotor. Hence, the piping of refrigeration circuit upstream of the inlet of the compressor, or downstream of the outlet of the compressor, undergo lower vibrations and, consequently, lower stress.

In particular, the inner conduit has a cylindrical shape extending along a first axis. The outer shell includes a cylindrical portion elongated along the first axis. In particular, the cylindrical portion of the outer shell surrounds and is coaxial with the inner conduit. In an embodiment, the lateral apertures of said plurality of lateral apertures are uniformly distributed on a surface of the wall of the inner conduit. In particular, the lateral apertures are distributed on a portion of the surface of the inner conduit which extends from the inlet to the outlet.

Preferably, the plurality of lateral apertures includes a first group of lateral apertures having a first dimension and a second group of lateral apertures having a second dimension, different from the first dimension. The first group of lateral apertures includes at least one aperture; the second group of lateral apertures also includes at least one aperture. Therefore, the plurality of lateral apertures includes at least two apertures having dimensions different one from another. In particular, the lateral apertures may have circular shape; in this case, their dimension is defined by their diameter.

It is here observed that having apertures of a plurality of different dimensions allows to effectively dampen vibrations in a wide range of frequencies, which is particularly desired where the compressor is equipped with an inverter (or VFD-Variable Frequency Drive), to work at a plurality of different speeds. In fact, each aperture dimension is optimal for dampening vibrations at a certain frequency; when the compressor works at variable speed, it generates vibrations in a wide range of frequencies; hence, having apertures of a plurality of different dimensions allows to effectively dampen the vibrations in the whole operating range of the compressor.

The outer shell preferably includes an additional wall, extending parallel to the wall of the inner conduit, from a first end to a second end. The outer shell may also include a first side (or first side wall), connected to the wall of the inner conduit and to the additional wall of the outer shell, at the first end, and a second side (or second side wall) connected to the wall of the inner conduit and to the additional wall of the outer shell, at the second end.

It is here observed that the inner conduit and the outer shell may be part of the duct above disclosed. Hence, the duct above may include the inner conduit and the outer shell; in this case, it is here observed that, preferably, the inlet (or first) opening of the duct is defined by the first (or inlet) opening of the inner conduit and the outlet (or second) opening of the duct is defined by the second (or outlet) opening of the inner conduit. Therefore, the dampening device according to the present disclosure may include the duct containing the mesh, or the perforated inner conduit surrounded by the outer shell, or a combination thereof. In fact, the reactive effect provided by the perforated inner conduit surrounded by the outer shell may be advantageously combined with the dissipative effect provided by the mesh, leading to high dampening potential of the dampening device.

In particular, in an embodiment, the mesh may be positioned in the dissipation chamber (defined between the inner conduit and the outer shell). Hence, the dissipation chamber defines the first zone of the duct internal volume, occupied by the mesh, while the inner conduit internal volume defines the second zone of the duct internal volume, free (not occupied) by the mesh.

In a further embodiment, the outer shell forms a plurality of dissipation chambers. The dissipation chambers of said plurality may be disposed one next to the other along the first axis (of the duct); alternatively, the dissipation chambers of said plurality may be disposed in radial fashion around the firs axis; it is also provided that the plurality of dissipation chambers includes some chambers disposed one next to the other along the first axis and some other chambers disposed in radial fashion around the firs axis. In these embodiments, the mesh may include a plurality of mesh portions, positioned in respective dissipation chambers of said plurality of dissipation chambers.

It is here observed that the mesh may be disposed in other locations within the duct, for instance it may be disposed in the internal volume of the inner conduit. As stated above, the dampening device (in particular, the duct or the inner conduit) may be connected to either one of the inlet port or outlet port of the compressor.

In one or more embodiments, the housing includes a plurality of inlet ports; said plurality of inlet ports includes a suction inlet port, for receiving a main flow of refrigerant fluid, and an economizer inlet port, for receiving, downstream of the suction inlet port and upstream of the outlet port, an economizer flow of refrigerant fluid. The refrigerant fluid received at the economizer inlet port has higher pressure than the refrigerant fluid received at the suction inlet port; hence, the economizer flow is added to the main flow in course of compression. The flow of refrigerant fluid which is discharged at the outlet port is given by the main flow and the economizer flow, mixed together and compressed. The pressure of the flow of refrigerant fluid which is discharged at the outlet is then higher than the pressure of the refrigerant fluid received at the economizer inlet port and, also, of the pressure of the refrigerant fluid received at the suction inlet port.

The dampening device (in particular, the duct or the inner conduit) may be connected to either one of the following: the economizer inlet port; the suction inlet port; the outlet port.

In an example, the dampening device is positioned externally to the housing of the compressor. In other words, the dampening device is connected to a port of the compressor (in particular, the economizer inlet port, the suction inlet port, or the outlet port) externally with respect to the housing of the compressor. The dampening device may be connected removably or unremovably.

Hence, it is here observed that the dampening device may be formed as a muffler connected to the housing of the compressor, externally with respect to the housing. This structure is very versatile and does not require a particular design of the compressor; hence, the dampening device formed as a muffler may be applied to any kind of compressor, even already existent ones, just by attaching it to the housing of the compressor (e.g. by welding or screwing). In particular, in a case where the dampening device is connected to the economizer inlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, connected to an economizer branch of the refrigeration circuit and the outlet end, defining the outlet opening, connected to the economizer inlet port of the housing of the compressor. Similarly, in a case where the dampening device is connected to the suction inlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, connected to a suction branch of the refrigeration circuit (positioned upstream of the compressor) and the outlet end, defining the outlet opening, connected to the suction inlet port of the housing of the compressor. Similarly, in a case where the dampening device is connected to the outlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, connected to the outlet port of the housing of the compressor and the outlet end connected, defining the outlet opening, connected to a discharge branch of the refrigeration circuit (positioned downstream of the compressor). Hence, in these embodiments, the dampening device is interconnected between the housing of the compressor and a respective branch of the refrigeration circuit.

It is further observed that the dampening device may be connected to the economizer inlet port or the suction inlet port or the outlet port internally to the housing. In other words, the dampening device may be positioned between the screw rotor and the economizer inlet port or the suction inlet port or the outlet port. In particular, in a case where the dampening device is connected to the economizer inlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, connected to the inlet port and the outlet end, defining the outlet opening, opened to the compression chamber. Similarly, in a case where the dampening device is connected to the suction inlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, connected to the suction inlet port and the outlet end, defining the outlet opening, opened to the compression chamber. Similarly, in a case where the dampening device is connected to the outlet port, the duct (or the inner conduit) of the dampening device will have the inlet end, defining the inlet opening, opened to the compression chamber and the outlet end connected, defining the outlet opening, connected to the outlet port of the housing of the compressor. Hence, in these embodiments, the dampening device is interconnected between the housing of the compressor and a respective branch of the refrigeration circuit.

In one or more embodiments, the screw compressor includes a plurality of dampening devices, wherein each dampening device of said plurality of dampening devices is according to one or more of the aspects of the present disclosure. In particular, each dampening device of said plurality of dampening devices is connected to either one of the following: the economizer inlet port; the suction inlet port; the outlet port.

Each dampening device of said plurality of dampening devices may be formed as a muffler external to the housing; in this case, for each dampening device one of the following conditions is verified: the outlet opening of the duct is connected to the suction inlet port, so that the duct internal volume is in fluid communication with the compression chamber through the suction inlet port; the outlet opening of the duct is connected to the economizer inlet port, so that the duct internal volume is in fluid communication with the compression chamber through the economizer inlet port; the inlet opening of the duct is connected to the outlet port, so that the duct internal volume is in fluid communication with the compression chamber through the outlet port.

Moreover, each dampening device of said plurality of dampening devices may be formed integrally within the housing. Moreover, one or more dampening device of said plurality may be formed integrally within the housing and one or more (other) dampening device of said plurality may formed as a muffler external to the housing.

Hence, for example, the screw compressor may comprise a first dampening device connected to the economizer inlet port, and/or a second dampening device connected to the suction inlet port, and/or a third dampening device connected to the outlet port.

In an embodiment, the dampening device comprises a perforated plate oriented transversally to the inner conduit. Preferably, in this embodiment, the dampening device is connected to the outlet port; however, it could be connected to the suction inlet port and/or to the economizer outlet port. Indeed, the screw compressor may be provided with two or more dampening devices, at different locations.

The perforated plate has a first face facing the outlet port (or the suction inlet port or the economizer outlet port); the first face delimits a further chamber (or intermediate chamber). The perforated plate has a second face opposite the first face; the second face may delimit the dissipation chamber or part of the dissipation chamber. Preferably, the first aperture of the inner conduit is open to the further chamber and the lateral apertures of the inner conduit are open on the dissipation chamber. Hence, the dissipation chamber is provided with two group of apertures: a first group of apertures provided on the inner conduit and a second group of apertures provided on the perforated plate. Preferably, the inner conduit is substantially aligned with the outlet port of the compressor (or the suction inlet port, or the economizer inlet port); the inner conduit and the outlet port are aligned along an axis which is transversal (orthogonal) to the perforated plate. Preferably, the perforated plate surrounds the inner conduit. Preferably, the inner conduit is elongated along a first axis and the perforated plate includes a plurality of holes having respective axes parallel to the first axis. Preferably, a passage section of the inner conduit is greater than a passage section of each hole provided in the perforated plate. The present disclosure also provides a refrigeration system. The refrigeration system includes a refrigerant fluid and a refrigeration circuit for circulating the refrigerant fluid. The refrigeration circuit includes: a condenser, for condensing the refrigerant fluid; an expansion device, for expanding the refrigerant fluid; an evaporator, for evaporating the refrigerant fluid, and a screw compressor. The screw compressor is according to one or more aspects of the present disclosure.

In particular, the refrigeration circuit includes a suction branch to feed (a main flow of) the refrigerant fluid to the suction of the compressor and a discharge branch to direct the refrigerant fluid which has been discharged from the compressor towards the condenser.

Preferably, the refrigeration circuit includes an economizer circuit. The economizer circuit includes an economizer valve, configured to receive an economizer flow of refrigerant fluid from a branch the refrigeration circuit upstream of the expansion device. The economizer circuit includes an economizer branch for directing an economizer flow of refrigerant fluid from the economizer heat exchanger to the screw compressor. The economizer circuit includes an economizer heat exchanger configured to provide heat exchange between the economizer flow, flowing in the economizer branch, and the refrigerant fluid flowing in the refrigeration circuit downstream of the condenser.

The dampening device of the screw compressor may be interconnected between the suction branch and the suction inlet port of the housing, or between the discharge branch and the outlet port of the housing, or between the economizer branch and the economizer inlet port of the housing. Moreover, the dampening device may be arranged inside the housing, between the screw rotor and one of said suction inlet port, economizer inlet port and outlet port of the housing.

In one or more embodiments, the refrigeration system comprises a variable frequency drive (VFD) for driving the screw compressor at variable speed. In particular, the compressor includes an electric motor connected to the screw rotor to transfer rotational movement to the screw rotor; the variable frequency drive is connected to electric motor of the compressor.

The present disclosure also relates to a method for dampening vibrations in a screw compressor. The vibrations are generated by rotation of a screw rotor within a housing. The housing includes (or defines) an inlet port and an outlet port, wherein the screw rotor rotation draws a flow of refrigerant fluid from the inlet port to the outlet port through a compression chamber delimited by the screw rotor and by the housing.

The method includes a step of providing a dampening device. The dampening device is according to one or more aspects of the present disclosure. In particular, the dampening device may include a duct defining a duct internal volume; the dampening device may also include a mesh, positioned in the duct internal volume. The dampening device (or the duct) may include an inner conduit, having a wall extending from a first (or inlet) opening to a second (or outlet) opening and defining an inner conduit internal volume; an outer shell, surrounding the inner conduit to form, between the inner conduit and the outer shell, a dissipation chamber, wherein the wall of the inner conduit defines a plurality of lateral apertures, so that the inner conduit internal volume and the dissipation chamber are in fluid communication through the plurality of lateral apertures. In an embodiment, the mesh is positioned in the dissipation chamber.

The method includes a step of connecting the duct (or the inner conduit) to either one of the inlet port or the outlet port of the housing, to put in fluid communication the duct internal volume (or the inner conduit internal volume) with the compression chamber.

In an embodiment, the duct (or the inner conduit) is connected to the outlet port of the housing, so that the refrigerant fluid exiting the compression chamber flows through the duct (or the inner conduit).

In an embodiment, the duct (or the inner conduit) is connected to the inlet port of the housing, so that the refrigerant fluid flows through the duct (or the inner conduit) before entering the inlet port. In particular, in an embodiment, the screw compressor includes a suction inlet port, for receiving a main flow of refrigerant fluid, and an economizer inlet port, for receiving, downstream of the suction inlet port and upstream of the outlet port, an economizer flow of refrigerant fluid; the duct (or the inner conduit) may be connected to the economizer inlet port, so that the economizer flow of refrigerant fluid flows through dampening device before entering the economizer inlet port, or to the suction inlet port, so that the main flow of refrigerant fluid flows through dampening device before entering the suction inlet port.

The method may comprise a step of connecting a first dampening device to the outlet port, and/or a step of connecting a second dampening device to the economizer inlet port, and/or a step of connecting a third dampening device to the suction inlet port.

The dampening device(s) may be connected internally or externally with respect to the housing.

The present disclosure also relates to a use of a dampening device for dampening vibrations in a screw compressor of a refrigeration system; the dampening device is according to one or more of the aspects of the present disclosure.

Brief description of drawings

This and other features of the invention will become more apparent from the following detailed description of a preferred, non-limiting example embodiment of it, with reference to the accompanying drawings, in which:

- Figure 1 illustrates a refrigeration system comprising a screw compressor according to the present disclosure;

- Figure 2 illustrates a dampening device of the screw compressor of figure 1, in longitudinal sectional view;

- Figure 3 illustrates the dampening device of figure 2, in cross sectional view; - Figure 4 illustrates an inner conduit of the dampening device of figure 3;

- Figures 5 to 8 illustrate alternatives embodiment of the dampening device of figure 2, in longitudinal sectional views;

- Figure 9 schematically illustrates the screw compressor of figure 1. With reference to the accompanying drawings, the numeral 100 denotes a refrigeration system;

- Figure 10A illustrates the dampening device of figure 2, in an embodiment wherein it is located internally to the housing of the compressor at the suction inlet port of the compressor; however, this embodiment may apply also to a dampening device located at the economizer inlet port or at the outlet port of the compressor;

- Figure 10B illustrates the dampening device of figure 2, in a further embodiment wherein it is located internally to the housing of the compressor at the suction inlet port of the compressor; however, this embodiment may apply also to a dampening device located at the economizer inlet port or at the outlet port of the compressor;

- Figure 11 illustrates the dampening device of figure 2, in an embodiment wherein it is located internally to the housing of the compressor at the outlet port of the compressor; however, this embodiment may apply also to a dampening device located at the suction inlet port or at the economizer inlet port of the compressor;

- Figure 12 illustrates the dampening device of figure 2, in an embodiment wherein it is located externally with respect to the housing of the compressor, at the economizer inlet of the compressor; however, this embodiment may apply also to a dampening device located at the suction inlet port or at the outlet port of the compressor.

Detailed description of preferred embodiments of the invention The refrigeration system 100 comprises a compressor 1 , a first heat exchanger 102, an expansion valve 103 and a second heat exchanger 104. Furthermore, the refrigeration system 100 includes a four-way valve

105, which is operable in a first position to make the refrigeration circuit functioning in a refrigeration mode and in a second position to make the refrigeration circuit functioning in a heating mode. In the refrigeration mode, the refrigerant fluid exiting the compressor 1 is fed to the first heat exchanger 102 (functioning as a condenser), then it is fed to the expansion valve 103, and then to the second heat exchanger 104 (functioning as an evaporator). In the heating mode the refrigerant fluid exiting the compressor 1 is fed to the second heat exchanger 104 (functioning as a condenser), while the first heat exchanger 102 functions as an evaporator. It is here observed that, in the context of the present description, the expressions “upstream” “downstream”, “evaporator”, “condenser” refer to a circulation of the refrigerant fluid in the refrigeration mode.

The refrigeration system 100 includes an economizer valve 107, configured to receive an economizer flow of refrigerant fluid from a branch the refrigeration circuit upstream of the expansion device 103. The economizer valve 107 is configured for providing an expansion of the refrigerant fluid, until a pressure which is intermediate between the pressure of the refrigerant fluid entering the compressor 1 and the pressure of the refrigerant fluid exiting the compressor 1. Preferably, the economizer valve 107 is adjustable to vary a (economizer) flow of refrigerant fluid passing thereof.

The refrigeration system 100 includes an economizer branch 130 configured for connecting the economizer valve 107 to the compressor 1. The refrigeration system 100 an economizer heat exchanger 106, configured to provide heat exchange between the economizer flow, flowing in the economizer branch, and the refrigerant fluid flowing in the branch of the refrigeration circuit located downstream of the condenser 102 (but upstream of the expansion device 103 and the economizer valve 107). The compressor 1 is a screw compressor, including at least a screw rotor 10 and a housing 14. The housing 14 has at least an inlet port 11 , 13 and an outlet port 12.

In particular, in an embodiment, the screw compressor 1 includes a male screw rotor configured to rotate about a respective axis and a female screw rotor, enmeshed with the male screw rotor and configured to rotate about a respective axis. In particular, the male screw rotor has a male lobed working portion and the female screw rotor has a female lobed portion; the male rotor is driven for rotation about the respective axis; the driving of the male screw rotor causes cooperation between the male lobed portion and the female lobed portion. Both the male screw rotor and the female screw rotor are located within the housing. Rotation of the male and female screw rotors compresses a flow of refrigerant fluid by drawing it from the inlet port to the outlet port, through a compression chamber.

In an embodiment, the screw compressor 1 includes a cylinder portion located in the housing, a screw rotor disposed in the cylinder portion and two gate rotors engaged with the screw rotor, as disclosed in patent document EP2634432A1 in the name of the same Applicant, here recalled for reference. It is explicitly provided that all the features of the cylinder portion, the screw rotor and the gate rotos disclosed in patent document EP2634432A1 may be applied to the compressor according to this embodiment of the present disclosure.

The screw compressor comprises a dampening device 20. The dampening device 20 is configured for dampening vibrations generated by the screw rotor 10. The dampening device 20 may be formed as a muffler, arranged externally with respect to the housing 14, or it may be positioned within the housing 14 (upstream or downstream of the compression chamber and/or of the screw rotor).

The housing 14 of the compressor 1 includes a suction inlet port 11 , an economizer inlet port 13 and an outlet port 12. The economizer inlet port 13 receives fluid from the economizer branch 130. The dampening device 20 may be connected to either one of the suction inlet port 11 or the suction inlet port 11 or the outlet port 12.

The dampening device 20 includes a duct 2. The duct 2 has defines a duct internal volume 23. The duct 2 has an external wall which extends from an inlet end (or first end) to an outlet end (or second end). The duct 2 defines, at the inlet end, an inlet opening (or first opening) 21 and, at the outlet end, an outlet opening (or second opening) 22. The duct 2 is preferably elongated along a first axis A1. However, the duct 2 may also be bended and form angles or curves.

In an embodiment, the outlet opening 22 of the duct 2 is connected to the suction inlet port 11 , so that the duct internal volume 23 is in fluid communication with the compression chamber through the suction inlet port 11.

In an embodiment, the outlet opening 22 of the duct 2 is connected to the economizer inlet port 13, so that the duct internal volume 23 is in fluid communication with the compression chamber through the economizer inlet port 13.

In particular, in an embodiment, the dampening device 20 includes an inner conduit 3 elongated along the first axis A1 and an outer shell 4 elongated along a second axis A2 perpendicular to the first axis A1. For instance, the outer shell 4 may be shaped as a cylinder extending about the second axis A2. Hence, the inner conduit 3 has a first opening connected to a branch of the refrigeration circuit (for instance, the economizer branch 130) and a second opening connected to a port of the compressor 1 (for instance, the economizer inlet port 13); between the first opening and the second opening, the inner conduit 3 is surrounded by the outer shell 4. The outer shell 4 may include a vent 700 to drain the oil. The inner conduit 3 comprises lateral apertures 34 which put the inner volume of the inner conduit 3 in communication with the dissipation chamber 5, which is defined between the outer shell 6 and the inner conduit 3. Into the dissipation chamber 5 a mesh may be provided. In an embodiment, the inlet opening of the duct 2 is connected to the outlet port 12, so that the duct internal volume 23 is in fluid communication with the compression chamber through the outlet port 12. In this embodiment, the outlet opening of the duct 2 may be in fluid communication with an inlet 7 of an oil separator 70. Hence, the duct 2 receives the refrigerant discharged by the compressor and feeds said refrigerant to the inlet 7 of the oil separator 70.

It is also provided that the compressor 1 may include a plurality of dampening devices including respective ducts 2, wherein each duct 2 is connected to either one of the suction inlet port 11 , the economizer inlet port 13 or the outlet port 12.

In one or more embodiments, the duct 2 (or the dampening device) includes an inner conduit 3 and an outer (or external) shell 4. The inner conduit 3 has an inner conduit internal volume 33. The inner conduit 3 has a wall 30 which extends from a first opening 31 to a second opening 32. The first opening 31 of the inner conduit 3 defines the inlet (or first) opening 21 of the duct 2. The second opening 32 of the inner conduit 3 defines the outlet (or second) opening 22 of the duct 2. The wall 30 of the inner conduit 3 is elongated along the first axis A1. In particular, the wall 30 of the inner conduit 3 has a cylindrical shape extending along the first axis A1 and having a circular cross section; however, in other embodiments, the wall 30 of the inner conduit 3 could have a square or rectangular or oval cross section. The wall 30 of the inner conduit 3 has a plurality of lateral apertures 34. In an embodiment, the plurality of lateral apertures 34 includes at least a first group of lateral apertures 341 having a first dimension and a second group of lateral apertures 342 having a second dimension, different from the first dimension.

In an embodiment, the lateral apertures 34 are uniformly distributed on the wall 30 of the inner conduit 3. In another embodiment, the apertures 34 include a first group of apertures 34 located in the nearby of the first opening 31 and a second group of apertures 34 (having the same dimension as the apertures of the first group, or different dimension than the apertures of the second group), located in the nearby of the second aperture 32 and, between the first and the second group of apertures 34m a wall portion having no apertures.

The outer shell 4 has a wall 40. In particular, the wall 40 of the outer shell 4 has a cylindrical shape extending along the first axis A1 , surrounding the wall 30 of the inner conduit 3 and having a circular cross section; however, in other embodiments, the wall 40 of the outer shell 4 could have a square or rectangular or oval cross section. Preferably, the wall 40 of the outer shell 4 is coaxial with the wall 30 of the inner conduit 3. In an embodiment, the wall 40 of the outer shell 4 defines, at least partially, the external wall of the duct 2.

The outer shell 4 surrounds the inner conduit 3 to form, between the outer shell 4 and the inner conduit 3, a dissipation chamber 5. Therefore, the dissipation chamber 5 is delimited by the wall 40 of the outer shell 4 and by the wall 30 of the inner conduit 3. Preferably, the dissipation chamber 5 is elongated along the first axis A1. The dissipation chamber 5 is in fluid communication with the inner conduit internal volume 33 through the lateral apertures 34 of the inner conduit 3. In these one or more embodiments, the sum of the inner duct internal volume 33 and of a volume of the dissipation chamber 5 provides the duct internal volume 23. The outer shell 4 further includes a first side (or first side wall) 41 and a second side (or second side wall) 42. The first side 41 and the second side 42 are oriented transversally to the first axis A1. The first side 41 has an outer border connected (e.g. by welding) to the wall 40 of the outer shell 4 and an inner border connected (e.g. by welding) to the wall 30 of the inner conduit 30. The second side 42 has an outer border connected (e.g. by welding) to the wall 40 of the outer shell 4 and an inner border connected (e.g. by welding) to the wall 30 of the inner conduit 30. The first side 41 faces the second side 42, at opposing ends of the outer shell 4 (and/or of the duct 2). Preferably, the first side 41 is located at the first end of the duct 2 and the second side 42 is located at the second end of the duct. Preferably, the dissipation chamber 5 is also delimited by the first side 41 and the second side 42 of the outer shell 4. Hence, the fluid may enter or exit the dissipation chamber 5 only through the lateral apertures 34 of the inner conduit 3.

The dampening device further includes a mesh 6. The mesh 6 is positioned in dissipation chamber 5. The mesh 6 has a longitudinal extension along the first axis A1 ; said longitudinal extension is preferably the same as the extension along the first axis A1 of the wall 40 of the external shell 4. In other words, the mesh 6 extends from the first side 41 to the second side 42. In an embodiment, the mesh 6 occupies the whole volume of the dissipation chamber 5.

The present disclosure also provides one or more embodiments wherein the perforated inner conduit 3 surrounded by the outer shell 4 is not provided in the duct 2. In fact, in an embodiment, the mesh 6 is positioned is the duct internal volume 23 so to occupy both in a central zone and in a peripheral zone of the duct internal volume 23. In an embodiment, the mesh 6 is positioned in a peripheral part of the duct 2, said peripheral part being elongated along the duct 2 and surrounding a central part of the duct 2, which provides a preferential passage for the flow of the refrigerant gas. In particular, the mesh 6 may be shaped as a hollow cylinder, defining an internal passage for the preferential passage of the flow of the refrigerant gas. The hollow cylinder may be in contact with the wall of the duct 2.

Moreover, in one or more embodiments, the wall of the duct 2 defines one or more cavities (or recesses) 24 in which the mesh 6 is positioned. Preferably, the one or more cavities 24 are formed externally with respect to the central a part of the duct 2, which provides a preferential passage for the flow of the refrigerant gas.

The dampening device (or the duct 2) may also include one or more separating walls (or grids) 25, wherein each separating wall 25 provides a separation between a respective cavity 24 and the part of the duct 2, which provides a preferential passage for the flow of the refrigerant gas. The wall of the duct 2 may define a first cavity and a second cavity opposing each with respect to a flow path of the refrigerant gas into the duct. The wall of the duct 2 may define a first cavity and a second cavity spaced one from another along the duct 2. The wall of the duct 2 may define a loop cavity surrounding the flow path of the refrigerant gas into the duct 2 (for example, in a case where the duct 2 is cylindrical, the loop cavity is ring shaped).

The mesh 6 may include a plurality of mesh portions positioned in respective cavities 24. In an embodiment, the duct 2 defines a plurality of cavities including a first group of cavities filled with respective mesh portions 6 and a second group of cavities not filled with the mesh 6.

In an embodiment wherein the dampening device 20 is located internally to the housing 14 and, preferably, is located at the outlet port 12 of the compressor 1 , the dampening device 2 may include a transversal perforate plate 8. The transversal perforated plate 8 is oriented transversally to the axis of the inner conduit 3. The transversal perforated plate 8 supports the inner conduit 3. The transversal perforated plate 8 has a first wall facing the outlet port 12 of the compressor 1 and a second wall, opposing the first wall, facing one or more cavities 24; hence, an intermediate chamber (or further chamber) 81 is defined between the outlet port 12 and the first wall of the transversal perforated plate 8. Int this embodiment, both the inner conduit internal volume 33, through the apertures 34, and the intermediate chamber 81 , through the perforations of the transversal perforated plate 8, are in fluid communication with said one or more cavities 24 (or at least some of them). Said cavities 24 may be filled with the mesh 6. The first (or inlet) opening 31 of the inner conduit 3 is opened to said intermediate chamber 81 Hence, the intermediate chamber 81 is in communication with the outlet port 12 of the compressor 1 , the inner conduit 3 internal volume (through the inlet opening 31) and the cavities 24 (through the perforated plate 8); the cavities 24 are in fluid communication with the intermediate chamber 81 (through the perforated plate 8) and with the inner conduit internal volume (through the apertures 34).

Claims

1. A screw compressor (1), comprising: a housing (14) including an inlet port (11 , 13) and an outlet port

(12); a screw rotor (10), arranged into the housing (14); a compression chamber, delimited by the screw rotor (10) and by the housing (14), wherein the screw rotor (10) is rotatable about a rotation axis for compressing a flow of refrigerant fluid, by drawing the flow of refrigerant fluid through the compression chamber, along a flow path within the housing from the inlet port (11 , 13) to the outlet port (12); a dampening device (20) for dampening vibrations generated by the screw rotor, the dampening device (20) including a duct (2), extending from an inlet opening (21) to an outlet opening (22) and defining a duct internal volume (23), and a mesh (6), positioned in the duct internal volume (23), characterized in that the outlet opening (22) of the duct is connected to the inlet port (11 , 13), so that the duct internal volume (23) is in fluid communication with the compression chamber through the inlet port (11, 13).

2. The screw compressor (1) according to claim 1 , wherein the housing (14) includes a plurality of inlet ports (11 , 13), said plurality of inlet ports including a suction inlet port (11), for receiving a main flow of refrigerant fluid, and an economizer inlet port (13), for receiving, downstream of the suction inlet port (11) and upstream of the outlet port (12), an economizer flow of refrigerant fluid, wherein one of the following conditions is verified: i) the outlet opening (22) of the duct is connected to the suction inlet port (11), so that the duct internal volume (23) is in fluid communication with the compression chamber through the suction inlet port (11); ii) the outlet opening (22) of the duct is connected to the economizer inlet port (13), so that the duct internal volume (23) is in fluid communication with the compression chamber through the economizer inlet port (13).

3. The screw compressor (1) according to claim 2, wherein the screw compressor (1) includes a plurality of dampening devices (20), wherein each dampening device (20) of said plurality of dampening devices (20) includes: a respective duct (2) defining a respective duct internal volume (23); a respective mesh (6), positioned in the respective duct internal volume (23), wherein, for each dampening device (20) of said plurality of dampening devices (20) one of the following conditions is verified: i) the outlet opening (22) of the duct is connected to the suction inlet port (11), so that the duct internal volume (23) is in fluid communication with the compression chamber through the suction inlet port (11); ii) the outlet opening (22) of the duct is connected to the economizer inlet port (13), so that the duct internal volume (23) is in fluid communication with the compression chamber through the economizer inlet port (13); iii) the inlet opening of the duct (2) is connected to the outlet port (12), so that the duct internal volume (23) is in fluid communication with the compression chamber through the outlet port (12).

4. The screw compressor (1) according to any of the previous claims, wherein the duct internal volume (23) includes a first zone occupied by the mesh (6) and a second zone free from the mesh (6), the first zone being in fluid communication with the second zone.

5. The screw compressor (1) according to claim 4, wherein the second zone extends from the inlet opening (21) to the outlet opening (22) in a central part of the duct (2), and wherein the first zone is positioned in a peripheral part of the duct (2), externally to the second zone.

6. The screw compressor (1) according to claim 5, wherein the first zone surrounds the second zone.

7. The screw compressor (1) according to claim 6, wherein the second zone is shaped as a cylinder elongated along a first axis (A1), from the inlet opening (21) to the outlet opening (22), and the first zone is shaped as a hollow cylinder surrounding the second zone.

8. The screw compressor (1) according to any of the previous claims from 4 to 7, wherein the dampening device includes a separating wall (25) having a plurality of apertures (34), said separating wall being positioned within the duct internal volume (23), and having a first face, facing the first zone, and a second face, opposite to the first face, facing the second zone.

9. The screw compressor (1) according to any of the previous claims, wherein the duct (2) includes: an inner conduit (3), having a wall extending from a first opening (31) to a second opening (32) and defining an inner duct internal volume (23), wherein the inlet opening (21) and the outlet opening (22) of the duct (2) are defined by the first opening (31) and the second opening (32) of the inner conduit (3); an outer shell (4), wherein a dissipation chamber (5) is formed between the inner conduit (3) and the outer shell (4); wherein the wall of the inner conduit (3) defines a plurality of lateral apertures (34), so that the inner conduit internal volume (33) and the dissipation chamber (5) are in fluid communication through the plurality of lateral apertures (34), wherein the mesh (6) is positioned into the dissipation chamber (5).

10. The screw compressor (1) according to claim 9, wherein the duct (2) extends along a first axis (A1) and wherein the outer shell (4) forms a plurality of dissipation chambers (5), disposed one next to the other along the first axis (A1), wherein the mesh (6) includes a plurality of mesh portions (61), positioned in respective dissipation chambers (5) of said plurality of dissipation chambers (5).

11. The screw compressor (1) according to any of the previous claims, wherein the mesh (6) includes a metallic knitted wire.

12. The screw compressor (1) according to any of the previous claims, wherein the dampening device (20) is located externally to the housing (14).

13. The screw compressor (1) according to claim 12, wherein the outlet opening (22) of the duct (2) is removably connected to the inlet port (11 , 13) of the housing (14).

14. A refrigeration system (100) comprising:

- a refrigerant fluid;

- a refrigeration circuit for circulating the refrigerant fluid, said refrigeration circuit including: a condenser (102), for condensing the refrigerant fluid; an expansion device (103), for expanding the refrigerant fluid; an evaporator (104), for evaporating the refrigerant fluid; and a screw compressor (1), according to any of the preceding claims.

15. A method for dampening vibrations in a screw compressor (1), the vibrations being generated by rotation of a screw rotor (10) within a housing (14) including an inlet port (11 , 13) and an outlet port (12), wherein the screw rotor (10) rotation draws a flow of refrigerant fluid from the inlet port (11 , 13) to the outlet port (12) through a compression chamber delimited by the screw rotor and by the housing (14), wherein the method comprises the following steps:

- providing a dampening device (20) including a duct (2), extending from an inlet opening (21) to an outlet opening (22) and defining a duct internal volume (23), and a mesh (6), positioned in the duct internal volume (23),

- connecting the outlet opening (22) of the duct to the inlet port (11, 13), to put the duct internal volume (23) in fluid communication with the compression chamber through the inlet port (11 , 13).

16. The method according to claim 15, wherein the housing includes a plurality of inlet ports (11 , 13), said plurality of inlet ports including a suction inlet port (11), for receiving a main flow of refrigerant fluid, and an economizer inlet port (13), for receiving, downstream of the suction inlet port (11) and upstream of the outlet port (12), an economizer flow of refrigerant fluid, wherein the connecting step includes connecting the outlet opening (22) of the duct to the economizer inlet port (13), so that the duct internal volume (23) is in fluid communication with the compression chamber through the economizer inlet port (13).

17. Use of a dampening device (20) for dampening vibrations in a screw compressor (1) of a refrigeration system (100), the screw compressor including a housing (14) having an inlet port (11 , 13) and an outlet port (12); a screw rotor (10), arranged into the housing (14); and a compression chamber, delimited by the screw rotor (10) and by the housing (14), wherein the screw rotor (10) is rotatable about a rotation axis for compressing a flow of refrigerant fluid, by drawing the flow of refrigerant fluid through the compression chamber, along a flow path within the housing (14) from the inlet port (11 , 13) to the outlet port (12); wherein the dampening device (20) includes: a duct (2) extending from an inlet opening (21) to an outlet opening (22) and defining a duct internal volume (23); a mesh (6), positioned in the duct internal volume (23), wherein the outlet opening (22) of the duct is connected to the inlet port (11 , 13), so that the duct internal volume (23) is in fluid communication with the compression chamber through the inlet port (11 , 13).