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Title:
SCREW COMPRESSOR STRUCTURE, PARTICULARLY FOR REFRIGERATING CIRCUITS
Document Type and Number:
WIPO Patent Application WO/2019/123026
Kind Code:
A1
Abstract:
The present invention concerns a screw compressor structure (10), particularly for refrigerating circuits, comprising: a containment body (11), comprising: an intake mouth (12) for a fluid to be compressed, a discharge mouth (13) for a compressed fluid and a seat (14) for two adjacent helical compression rotors (15, 16); two adjacent helical compression rotors (15, 16), each with a helical protrusion configured to engage with the helical protrusion of the other helical compression rotor to define one or more compression chambers; motorisation means (17) for the helical compression rotors (15, 16); lubrication means (18) with a lubricant fluid for the helical compression rotors (15, 16); filtration means (19) of the compressed fluid for the separation from the compressed fluid of the lubricant fluid. The filtration means (19) comprise a passage duct (20) for the compressed fluid, comprising inside it flow diverting means (21) configured to induce a swirling motion in the compressed fluid.

Inventors:
MALESAN, Michele (Via Padre Osmolowsky 6A, Lonigo, 36045, IT)
PEDROLLO, Lorenzo (Via Ambrosi 42, Soave, 37038, IT)
Application Number:
IB2018/053894
Publication Date:
June 27, 2019
Filing Date:
May 31, 2018
Export Citation:
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Assignee:
REF POWER S.R.L. (Via Enrico Fermi 6, Lonigo, 36045, IT)
International Classes:
F04C18/16
Foreign References:
US20110182762A12011-07-28
US6364645B12002-04-02
US6045344A2000-04-04
DE102013020536A12015-06-18
Attorney, Agent or Firm:
MARCHIORO, Paolo (Studio Bonini Srl, Corso Fogazzaro 8, Vicenza, 36100, IT)
Download PDF:
Claims:
CLAIMS

1 ) Screw compressor structure (10), particularly for refrigerating circuits, comprising:

- a containment body (1 1 ), comprising an intake mouth (12) for a fluid to be compressed, a discharge mouth (13) for a compressed fluid and a seat (14) for two adjacent helical compression rotors (15, 16);

- two adjacent helical compression rotors (15, 16), each with a helical protrusion configured to engage with the helical protrusion of the other helical compression rotor to define one or more compression chambers;

- motorisation means (17) for said helical compression rotors (15, 16);

- lubrication means (18) with a lubricant fluid for said helical compression rotors (15, 16);

- filtration means (19) of the compressed fluid for the separation from said compressed fluid of said lubricant fluid,

characterised in that said filtration means (19) comprise a passage duct (20) for the compressed fluid, comprising inside it flow diverting means (21 ) configured to induce a swirling motion in the compressed fluid.

2) Screw compressor structure according to claim 1 , characterised in that said containment body (1 1 ) comprises a central casing (22), in which the helical compression rotors (15, 16) are arranged, said central casing (22) being fixed on one side to an electric motor (23), defining the motorisation means (17) for the actuation of a first helical compression rotor (15), and on the opposite side to a bell-shaped portion (24) inside which said filtration means (19) are arranged.

3) Screw compressor structure according to the previous claim, characterised in that in the joining area between said central casing (22) and said bell-shaped portion (24) there is a channelling element (25), configured to conduct the flow of compressed fluid coming out from the helical compression rotors (15, 16) towards said filtration means (19).

4) Screw compressor structure according to one or more of the preceding claims, characterised in that said channelling element (25) comprises an inlet mouth and an outlet mouth (25a), facing towards the filtration means (19).

5) Screw compressor structure according to one or more of the preceding claims, characterised in that said filtration means (19) comprise a transversal separator (26), consisting of at least one mesh of metallic material, and positioned transversally with respect to the main axis of symmetry (X) of the bell-shaped portion (24) in which such a transversal separator (26) is positioned.

6) Screw compressor structure according to one or more of the preceding claims, characterised in that said passage duct (20), with the flow diverting means (21 ), is arranged in the bell-shaped portion (24) so as to intercept the compressed fluid coming out from the outlet mouth (25a) of the channelling element (25) before the same compressed fluid crosses the transversal separator (26).

7) Screw compressor structure according to one or more of the preceding claims, characterised in that said passage duct (20) comprises a tubular filtering body (28), arranged passing through the transversal separator (26), and a joining sleeve (29), arranged between the same tubular filtering body (28) and the outlet mouth (25a), the flow diverting means (21 ) being arranged inside the tubular filtering body (28).

8) Screw compressor structure according to one or more of the preceding claims, characterised in that said tubular filtering body (28) has a cylindrical tubular jacket (38), having a first end (30) closed by a bottom plate (31 ) and the opposite second end (32) open on the inside of the bell-shaped portion (24) of the containment body (1 1 ).

9) Screw compressor structure according to one or more of the preceding claims, characterised in that said flow diverting means (21 ) comprise one or more helical protrusions (40) that project from the inner surface (39) of the tubular jacket (38) and extend in a spiral in the direction (X1 ) of the main axis of symmetry of the tubular jacket (38), and around such a direction (X1 ).

10) Screw compressor structure according to one or more of the preceding claims, characterised in that said flow diverting means (21 ) comprise a central diverting body in the radial direction (36) of the flow of compressed fluid coming out from the joining sleeve (29).

11 ) Screw compressor structure according to one or more of the preceding claims, characterised in that said central radial diverting body (36) comprises a diverting portion (41 ), facing the second end (37) of the joining sleeve (29) so as to intercept the flow of compressed fluid coming out from it, and a tubular portion (42) defining with the tubular jacket (38) an annular gap.

12) Screw compressor structure according to one or more of the preceding claims, characterised in that said tubular portion (42) comprises a cylindrical element, coaxial and concentric to the tubular jacket (38), having an outer surface (43) thereof.

13) Screw compressor structure according to one or more of the preceding claims, characterised in that said flow diverting means (21 ) comprise one or more helical protrusions (45) that project from the outer surface (43) of said tubular portion (42) and extend in a spiral in the direction (X1 ) of the main axis of symmetry of said tubular portion (42), and around such a direction (X1 ).

14) Screw compressor structure according to one or more of the preceding claims, characterised in that inside the annular gap defined between said inner surface (39) of the outer tubular jacket (38) and the outer surface (43) of said tubular portion (42) there is an intermediate tubular element (48) for dividing the flow of compressed fluid, said intermediate tubular element (48) having an outer surface (49) and an inner surface (50).

15) Screw compressor structure according to one or more of the preceding claims, characterised in that said flow diverting means (21 ) comprise one or more helical protrusions (51 ) that project from the outer surface (49) of the intermediate tubular element (48) and extend in a spiral in the direction of the main axis of symmetry of the intermediate tubular element (48), also comprising one or more helical protrusions (52) that project from the inner surface (50) of said intermediate tubular element (48) and extend in a spiral in the direction of the main axis of symmetry of the intermediate tubular element (48).

Description:
SCREW COMPRESSOR STRUCTURE, PARTICULARLY FOR REFRIGERATING CIRCUITS.

DESCRIPTION

The invention concerns a screw compressor structure, particularly for refrigerating circuits.

The efficiency of a refrigeration, conditioning or heat pump system depends crucially on its dynamic behaviour. In particular, in the presence of great changes of load it is necessary to have a high quality of regulation with power control that is continuous or in small steps.

The recent and innovative compact screw compressors offer the best features for these requirements, in the field of medium and high refrigerating power, in refrigeration, conditioning and heat pump applications.

Such screw compressors known currently generally comprise:

- a containment body, comprising an inlet mouth for a fluid to be compressed, an outlet mouth for a compressed fluid and a seat for two adjacent helical compression rotors,

- such adjacent helical compression rotors each having a helical protrusion configured to engage with the helical protrusion of the other helical compression rotor to define one or more compression chambers;

- motorisation means for the helical compression rotors;

- lubrication means with a lubricant fluid for said helical compression rotors;

- filtration means of the compressed fluid to separate the compressed fluid, intended for the refrigeration system, from the lubricant fluid.

The fluid processed by the screw compressors is thus made up of a mixture of refrigerating fluid, generally gas, and lubricant fluid, generally an oil, which necessarily must be present both to allow the correct lubrication of the bearings, and to create a sealing film between the portions of the rotors that define the compression chambers.

Once such a function has ended, the oil must be separated from the gas in the most efficient way possible, and remain only inside the compressor to thus allow the conditioning system to carry out the best heat exchange efficiency, with only the circulation of the gas in the refrigerating circuit.

The filtration means generally comprise one or more metallic mesh filters, in the jargon ‘demisters’, arranged inside a bell-shaped portion of the containment body and intended to intercept the droplets of oil and to allow the flow of gas coming out from the compressor to pass towards the circuit.

Such a separation system, commonly used by manufacturers of screw compressors, thus foresees two separation steps, a first separation step of the oil resulting from the impact of the fluid after its compression on the inner wall of the bell-shaped portion, indeed known as“oil separator”, and a second step of passing through the one or more metallic meshes of the“demister”, adapted for holding the droplets of oil and thus allowing almost exclusively gas to pass. Such a separation system, although known and widely available, is effective but with a limit of the migration percentage, i.e. of passage of oil towards the conditioning system, never below 3%.

The task of the present finding is to provide a screw compressor structure capable of avoiding the quoted limits of the prior art.

In particular, a purpose of the finding is to devise a compressor structure capable of obtaining greater efficiency with respect to analogous known screw compressors.

Furthermore, a purpose of the invention is to devise a compressor structure that allows better recovery of the oil present in suspension in the refrigerating fluid.

Another purpose of the present invention is to make a compressor structure that occupies the same space as compressors with integrated oil separator of the known type.

The task as well as the aforementioned purposes are accomplished by a screw compressor structure, particularly for refrigerating circuits, according to claim 1. Further characteristics of the compressor structure according to claim 1 are described in the dependent claims.

The task and the aforementioned purposes, together with the advantages that will be mentioned hereinafter, are highlighted by the description of an embodiment of the invention, which is given, for indicating but not limiting purposes, with reference to the attached tables of drawings, where:

- figure 1 represents a perspective section view of a compressor structure according to the invention;

- figure 2 represents a perspective view of a detail of the compressor structure according to the invention;

- figure 3 represents a perspective section view of the detail of figure 2;

- figure 4 represents a cross section of the detail of figure 2; - figure 5 represents a cross section of a variant embodiment of the detail of figure 2.

With reference to the quoted figures, a screw compressor structure according to the invention is wholly indicated with reference numeral 10.

Such a screw compressor structure 10 comprises:

- a containment body 11 , comprising an intake mouth 12 for a fluid to be compressed, a discharge mouth 13 for a compressed fluid and a seat 14 for two adjacent helical compression rotors 15 and 16;

- two adjacent helical compression rotors 15 and 16, each with a helical protrusion configured to engage with the helical protrusion of the other helical compression rotor to define one or more compression chambers;

- motorisation means 17 for the helical compression rotors 15 and 16;

- lubrication means 18, with a lubricant fluid, for the helical compression rotors 15 and 16;

- filtration means 19 of the compressed fluid for the separation of said lubricant fluid from the compressed fluid.

The special feature of the compressor structure 10 according to the invention is the fact that the filtration means 19 comprise a passage duct 20 for the compressed fluid, comprising inside it flow diverting means 21 configured to induce a swirling motion in the compressed fluid.

In particular, such a passage duct 20 for the compressed fluid is arranged in outlet from the helical compression rotors 15 and 16.

In particular, in the present embodiment, the containment body 11 comprises a central casing 22, in which the helical compression rotors 15 and 16 are arranged, said central casing 22 being fixed on one side to an electric motor 23, defining the motorisation means 17 for the actuation of a first helical compression rotor 15, the so-called“male” rotor, and on the opposite side to a bell-shaped portion 24 inside which the filtration means 19 are arranged.

The lubrication means 18 should be considered to be of the per se known type, and comprise, for example, a collection tank, integrated in the lower part of the central casing 22, and a recirculation circuit for the lubricant fluid, with loading and discharge taps.

In the joining area between the central casing 22 and the bell-shaped portion 24 there is a channelling element 25, configured to conduct the flow of compressed fluid coming out from the helical compression rotors 15 and 16 towards the filtration means 19.

The channelling element 25 comprises an inlet mouth, not visible in the drawings, and an outlet mouth 25a, facing towards the filtration means 19.

The filtration means 19 comprise a transversal separator 26, consisting of at least one mesh of metallic material, known as ‘demister’, and positioned transversally with respect to the main axis of symmetry X of the bell-shaped portion 24 in which such a transversal separator 26 is positioned.

The passage duct 20, with the flow diverting means 21 , is arranged in the bell shaped portion 24 so as to intercept the compressed fluid coming out from the outlet mouth 25a of the channelling element 25 before the same compressed fluid crosses the transversal separator 26.

In particular, in the form herein described of the invention, not limiting the same invention, the passage duct 20 comprises a tubular filtering body 28, arranged passing through the transversal separator 26, and a joining sleeve 29, arranged between the same tubular filtering body 28 and the outlet mouth 25a. The flow diverting means 21 are arranged inside the tubular filtering body 28. The tubular filtering body 28 has a cylindrical tubular jacket 38, having a first end 30 closed by a bottom plate 31 and the opposite second end 32 open on the inside of the bell-shaped portion 24 of the containment body 11 .

The tubular filtering body 28 is substantially cylindrical in shape.

The inner diameter D1 of the tubular jacket 38 of the tubular filtering body 28 is greater than the outer diameter D2 of the joining sleeve 29.

The joining sleeve 29 has a first end 33 equipped with a perimeter flange 34 for fixing to the channelling element 25, flow diverter.

Such a channelling element 25 is, for example, a volute made of metallic material.

The joining sleeve 29 has a second end 37 inserted passing into a counter shaped hole 35 defined on the bottom plate 31 of the tubular filtering body.

The flow diverting means 21 comprise one or more helical protrusions 40 that project from the inner surface 39 of the tubular jacket 38 and extend in a spiral in the direction X1 of the main axis of symmetry of the tubular jacket 38, and around such a direction X1 .

Such helical protrusions 40, when reached by the compressed fluid, divert it radially and tangentially so that it swirls and licks the inner surface 39 for a longer time, so as to leave a greater amount of particles of lubricant fluid, i.e. of oil, than would have been left by flowing in a substantially rectilinear direction, for example in a direction parallel to the direction X1 of the axis of symmetry of the tubular jacket 38.

Moreover, the swirling motion induces a centrifugal force in the oil particles present in the compressed fluid that pushes them towards the inner surface 39, and thus to leave the flow of compressed fluid to deposit on the inner surface 39.

The flow diverting means 21 also comprise a central diverting body in the radial direction 36 of the flow of compressed fluid coming out from the joining sleeve 29.

Such a central radial diverting body 36, as a non-limiting example of the invention, comprises a diverting portion 41 , facing the second end 37 of the joining sleeve 29 so as to intercept the flow of compressed fluid coming out from it, and a tubular portion 42, defining with the tubular jacket 38 an annular passage gap for the compressed fluid.

The diverting portion 41 consists, for example, of an ogive-shaped bottom plate the end of which faces towards the second end of the joining sleeve 29. The shape of such a diverting portion 41 is shaped, for example, like a spherical arc.

The tubular portion 42 consists, for example, of a cylindrical tubular element, coaxial and concentric to the tubular jacket 38.

Such a tubular portion 42 has an outer surface 43 thereof, indicated in figure 4. Thus, the central radial diverting body 36 has a cylindrical tubular portion 42, said tubular portion 42 being closed, at the end facing towards the joining sleeve 29, by the diverting portion 41 , the latter being rounded with convexity facing towards the joining sleeve 29 so as to intercept the fluid and divert it towards the annular gap gradually and without creating sudden changes of direction or swirling motions that would lead to load losses.

The central radial diverting body 36 forces the pressurised fluid coming out from the joining sleeve 29 to cross the annular gap defined between the inner surface 39 of the outer tubular jacket 38 and the outer surface 43 of the tubular portion 42.

In this way the compressed fluid licks one or other or both of such inner and outer surfaces 39, 43, and the removal of oil is thus greater.

The flow diverting means 21 also comprise one or more helical protrusions 45 that project from the outer surface 43 of the tubular portion 42 and extend in a spiral in the direction X1 of the main axis of symmetry of the tubular portion 42, and around such a direction X1.

The screwing direction of the helical protrusions 45 projecting from the outer surface 43 is the same as the screwing direction of the helical protrusions 40 projecting from the inner surface 39.

The central radial diverting body 36 is fixed to the tubular jacket 38 through at least two, for example three, radial supports 47.

Such radial supports 47 are fixed to both the central radial diverting body 36 and tubular jacket 38, for example through welding.

Inside the annular gap defined between the inner surface 39 of the outer tubular jacket 38 and the outer surface 43 of the tubular portion 42 there is an intermediate tubular element 48 for dividing the flow of compressed fluid.

Such an intermediate tubular element 48 is cylindrical.

Such an intermediate tubular element 48 has an outer surface 49 and an inner surface 50, indicated in figure 4.

Such an intermediate tubular element 48 is coaxial and concentric to the tubular jacket 38 and coaxially surrounds the tubular portion 42.

Such an intermediate tubular element 48, with the tubular jacket 38 and the tubular portion 42, makes two concentric annular passage gaps for the flow of compressed fluid, a part of which passes through the outer annular gap and another part of which passes through the inner annular gap.

Overall, the flow of compressed gas is forced to lick four cylindrical surfaces, with a consequent further advantage in terms of filtration and of separation of the lubricant oil from the flow of compressed fluid.

The flow diverting means 21 also comprise one or more helical protrusions 51 that project from the outer surface 49 of the intermediate tubular element 48 and extend in a spiral in the direction of the main axis of symmetry of the intermediate tubular element 48.

The screwing direction of the helical protrusions 51 projecting from the outer surface 49 of the intermediate tubular element 48 is the same as the screwing direction of the helical protrusions 40 projecting from the inner surface 39 of the tubular jacket 38.

The flow diverting means 21 also comprise one or more helical protrusions 52 that project from the inner surface 50 of the intermediate tubular element 48 and extend in a spiral in the direction of the main axis of symmetry of the intermediate tubular element 48.

The screwing direction of the helical protrusions 52 projecting from the inner surface 50 of the intermediate tubular element 48 is the same as the screwing direction of the helical protrusions 45 projecting from the outer surface 43 of the tubular portion 42.

The facing helical protrusions 40 and 51 in the outer gap between the tubular jacket 38 and the intermediate tubular element 48, and the facing helical protrusions 45 and 52 in the inner gap between the tubular portion 42 and the intermediate tubular element 48 define two concentric series of helical channels in which the flow of compressed fluid is made to flow, licking the respective surfaces thereof, with consequent advantages in terms of filtration and of separation of lubricant oil from the compressed work fluid intended for a heat exchange circuit.

Figure 5 represents a cross section view of a variant embodiment of the flow diverting means, indicated here with reference numeral 121.

The duct 120 thus comprises a filtering body 128 inside which the flow diverting means 121 comprise:

- one or more helical protrusions 140 that project from the inner surface 139 of the tubular jacket 138 and extend in a spiral in the direction X1 of the main axis of symmetry of the tubular jacket 138, and around such a direction X1 ;

- and one or more helical protrusions 145 that project from the outer surface

143 of the tubular portion 142 and extend in a spiral in the direction X1 of the main axis of symmetry of the tubular portion 142 of the central radial diverting body 36, and around such a direction X1.

In such a variant embodiment there is no intermediate tubular element.

The flow of compressed fluid is thus filtered and separated in a first step through such flow diverting means 21 and 121 ; thereafter, coming out from the duct 20 and 120 it meets the curved inner surface of the bell-shaped portion 24 for a second filtration and separation step, and it is directed towards the transversal separator 26 for a third filtration and separation step.

In practice, it has been seen how the finding achieves the task and the predetermined purposes.

With the insertion of such flow diverting means, configured to induce in the compressed fluid a swirling motion in the oil separation process, two important principles contained in it are added, which are significantly effective for the predetermined objective. Thanks to its operating principle, indeed, the longitudinal flow of the compressed fluid is added to, as well as by the speed and flow rate already acquired in the compression, with a further separation by impact and particularly a radial dynamicity by means of the helical channels formed in the filtering body 28 and 128.

The compressed fluid thus immediately undergoes a separation step and will be characterised at the outlet of the device by a high-speed“twisted” flow, which allows a filtration and separation such as to result in an oil residue in the compressed fluid of less than 1%, against a minimum of about 3% that can be obtained in known screw compressors.

The finding thus conceived can undergo numerous modifications and variants, all of which are covered by the inventive concept; moreover, all of the details can be replaced by other technically equivalent elements.

In practice, the components and the materials used, provided that they are compatible with the specific use, as well as the contingent shapes and sizes, can be whatever according to the requirements and the state of the art.

Where the characteristics and the techniques mentioned in any claim are followed by reference symbols, such reference symbols should be considered to be applied for the sole purpose of increasing the intelligibility of the claims and consequently such reference symbols do not have any limiting effect on the interpretation of each element identified as an example by such reference symbols.