FR2985552A1 - THERMODYNAMIC SYSTEM - Google Patents

Abstract

This compression device (6) comprises first and second compressors (7, 8) connected in parallel, a suction line (19) intended to be connected to an outlet of an evaporator (5), first and second ducts suction means (21) arranged to place the suction line (19) in communication with the inlet ports (15) of the first and second compressors (7, 8) respectively, and a leveling line of oil (24) connecting the oil pans (13) of the first and second compressors (7, 8). The compression device (6) further comprises an oil separator (31) mounted on the suction line (19) or the second suction line (22), and an oil return line (39). ) arranged to connect an oil outlet (36) of the oil separator (31) to the oil sump (13) of the first compressor (7).

Description

The present invention relates to a compression device, a thermodynamic system comprising such a compression device. The document FR 2 605 393 describes a thermodynamic system, and more particularly a refrigeration system, comprising: a circuit for circulating a refrigerant successively comprising a condenser, an expander, a evaporator and a compression device connected in series, the compression device comprising at least a first fixed capacity compressor and a second fixed capacity compressor connected in parallel, each compressor comprising an enclosure comprising on the one hand a low pressure part containing a motor and an oil sump disposed in the bottom of the chamber, and secondly a refrigerant inlet opening opening in the low pressure part, - a suction line connected to the evaporator, - a first suction line connecting the 15 suction line with the inlet of the first compressor, - a second suction line connecting the first suction line with the inlet of the second compressor, - a restriction member disposed in the second suction line and arranged to maintain a pressure in the lower part of the pressure of the first compressor greater than the pressure in the part. low pressure of the second compressor when the first and second compressors operate simultaneously; - a flow separation device arranged between the suction line and the first and second suction lines, the flow separation device being arranged to drive the most of the refrigerant from the evaporator to the first compressor, and - an oil level equalization line promoting the transfer of oil between the two compressors. Such a thermodynamic system ensures that most of the oil entrained by the refrigerant is returned to the first compressor. Due to the high pressure prevailing in the low pressure portion of the first compressor (due to the presence of the restriction member in the second suction line), the oil in the oil sump of the first compressor is driven. to the oil sump of the second compressor, via the oil level equalizing line, so as to balance the oil levels in the first and second compressors.

Such a solution, although satisfactory for a thermodynamic system comprising two compressors with fixed capacity having close capacities, is absolutely not for a thermodynamic system comprising at least one compressor with variable capacity, and more particularly with variable speed, or two fixed capacity compressors with very different capacities. Indeed, when the variable speed compressor operates at low speed, for example less than or of the order of 30 Hz, for a certain period and the second compressor is operating, a pressure imbalance between the oil sump of the two compressors is established, causing a transfer of the majority of the oil from the evaporator towards the second compressor, and therefore a significant increase of the oil level in the oil sump of the second compressor and a depletion of oil in the oil pan of the first compressor can lead to significant damage to the latter. It is the same when both compressors are fixed capacity and the second compressor has a much greater capacity than the first compressor. Consequently, the above-mentioned solution does not make it possible to obtain satisfactory balancing of the oil levels whatever the type of compressor used, and whatever the operating conditions of the latter. The present invention aims to remedy these disadvantages. The technical problem underlying the invention therefore consists in providing a compression device which is of simple and economical structure, making it possible to obtain a balancing of the oil levels in each compressor whatever the operating conditions of the device. compression, and regardless of the type of compressors used. For this purpose, the present invention relates to a compression device comprising: at least a first compressor and a second compressor connected in parallel, each compressor comprising a sealed enclosure comprising on the one hand a low pressure part containing a motor and a housing; of oil, and on the other hand an inlet opening opening into the low pressure part, a suction line intended to be connected to an outlet of an evaporator, a first suction pipe arranged to in communication the suction line with the inlet of the first compressor, - a second suction line arranged to put in communication the suction line with the inlet of the second compressor, and - a oil level equalization line arranged to connect the oil pans of the first and second compressors, characterized in that the compression device comprises d further: - at least one oil separator mounted on the suction line or the second suction line, the oil separator comprising an oil outlet, and - a return line of oil arranged to connect the oil outlet port of the oil separator to the oil pan of the first compressor. The presence of an oil separator on the suction line or on the second suction line makes it possible to ensure, whatever the operating conditions of the compression device, and whatever the type of compressor used. , a return of most of the oil entrained by the refrigerant to the first compressor via the oil return line. The oil in the oil pan of the first compressor is then driven to the oil pan of the second compressor, via the oil level equalizing pipe, so as to balance the oil levels in the oil tanks. first and second compressors. The compression device according to the invention thus ensures a balancing of the oil levels in each compressor whatever the operating conditions of the compression device, and whatever the type of compressors used, all using only a cheap oil separator. In addition, the compression device according to the invention ensures the presence of a minimum amount of oil in the oil sump of the first compressor. Advantageously, the oil separator further comprises an inlet port for connection to the outlet of the evaporator so as to allow the introduction of an oil-refrigerant mixture into the oil separator, and a refrigerant discharge port connected to at least the inlet of the second compressor. Preferably, the oil separator comprises a separation chamber, the inlet port and the refrigerant discharge port of the oil separator being respectively in communication with the separation chamber. The inlet orifice of the oil separator is thus intended to be connected to the outlet of the evaporator so as to allow the introduction of an oil-refrigerant mixture into the separation chamber. According to a first embodiment of the invention, the suction line comprises a first connection line connected to the inlet orifice of the oil separator and intended to be connected to the outlet of the evaporator, and a second connecting line arranged to connect the refrigerant discharge port of the oil separator with the first and second suction lines. The first and second connecting pipes have, for example, substantially identical diameters. Preferably, the first connecting line is arranged to extend from the outlet of the evaporator to the inlet of the oil separator.

According to one embodiment of the invention, the second connecting pipe extends from the refrigerant discharge port of the oil separator to a bypass point, the first suction pipe extends from the bypass point to the inlet of the first compressor, and the second suction pipe extends from the bypass point to the inlet of the second compressor. According to one embodiment of the invention, the second connecting pipe projects inside the separation chamber. According to a second embodiment of the invention, the second suction pipe comprises an upstream pipe portion arranged to communicate the inlet port of the oil separator with the suction line, and a portion downstream conduit arranged to port the refrigerant discharge port of the oil separator to the inlet port of the second compressor. According to one embodiment of the invention, the downstream pipe portion protrudes inside the separation chamber.

Preferably, the suction line is arranged to extend from the outlet of the evaporator to a bypass point, the first suction line extends from the branch point to the orifice of the admitting the first compressor, the upstream pipe portion extends from the diversion point to the oil separator inlet, and the downstream pipe portion extends from the discharge port of refrigerant from the oil separator to the inlet of the second compressor. According to one embodiment of the invention, the oil return line is arranged to open into the first suction line. According to another embodiment of the invention, the oil return line is arranged to open into the oil sump of the first compressor. Advantageously, the second suction line comprises restriction means arranged to reduce the flow section of the refrigerant in the second suction line. The restriction means are preferably arranged to maintain a pressure in the low pressure portion of the first compressor greater than the pressure in the low pressure portion of the second compressor when the first and second compressors operate simultaneously. Advantageously, the restriction means are arranged such that the flow section of the refrigerant at the restriction means is smaller than the flow section of the refrigerant at the inlet of the second compressor. . The restriction means comprise, for example, a restriction member disposed in the second suction line. According to one embodiment of the invention, the first compressor is a variable capacity compressor, and the second compressor is a fixed capacity compressor. Thus, by arranging the oil separator on the suction line or the second suction line and connecting the oil outlet port of the oil separator to the oil pan of the first compressor, it is possible to protect the most expensive compressor from the compression device and undergoing the most pressure variation in its oil sump. Variable capacity compressor means any compressor 35 that can have a variable flow rate (or several flow rates) at the suction of the compressor for the same operating point (an operating point corresponding to a suction pressure, a temperature of suction and a given discharge pressure). Among the known technical solutions for producing a variable capacity compressor, there will be mentioned, for example: a compressor driven by a variable speed motor; a compressor driven by a 2-speed motor (type 2/4 pole motor); a compressor driven by a fixed speed motor plus a gearbox, - a compressor driven by a fixed speed motor plus an epicyclic gear (planetary), - a compressor with relief valves opening or closing an internal bypass to the compressor, a compressor with multiple compression units, some of which can be deactivated; a compressor with internal mechanism to create intermittent compression. According to an alternative embodiment of the invention, the first and second compressors may be fixed capacity compressors. The first and second fixed capacity compressors may have different capacities, for example. Advantageously, the oil separator is a cyclone oil separator. Preferably, the oil level equalization line comprises at least a first end portion projecting inside the enclosure of one of the first and second compressors, the first end portion comprising an end wall extending transversely to the longitudinal direction of said first end portion and an opening formed above said end wall such that when the oil level in the oil sump of the compressor in which the first end portion extends above the upper level of said end wall, oil flows through said opening towards the other compressor. Preferably, the first end portion projecting inside the chamber of the second compressor. The oil level equalization line advantageously comprises a second end portion projecting inside the chamber of the other of the first and second compressors, the second end portion comprising a wall of end extending transversely to the longitudinal direction of said second end portion and an opening formed above the end wall of said second end portion so that when the oil level in the crankcase of the compressor in which the second end portion protrudes extends above the upper level of the end wall of the second end portion, oil flows through the opening of the the second end portion towards the other compressor. According to one embodiment of the invention, at least one of the first and second end portions comprises an oil return orifice located below the upper level of the end wall of said end portion. Each of the first and second compressors is for example a scroll compressor. In any case, the invention will be better understood with the aid of the description which follows with reference to the appended diagrammatic drawing showing, by way of non-limiting examples, two embodiments of this compression device. Figure 1 is a schematic view of a thermodynamic system according to a first embodiment of the invention. Figure 2 is a diagrammatic sectional view of a compression device of the thermodynamic system of Figure 1. Figures 3a and 3b are perspective and top views, respectively, of an end portion of a pipe of FIG. oil level equalization of the compression device of FIG. 2. FIG. 4 is a schematic view of a thermodynamic system according to a second embodiment of the invention. Figure 1 schematically illustrates the main components of a thermodynamic system 1. The thermodynamic system 1 may be a refrigeration system. The thermodynamic system 1 comprises a circulation circuit 2 of a refrigerant successively comprising a condenser 3, an expander 4, an evaporator 5 and a compression device 6 connected in series.

The compression device 6 comprises a first variable capacity compressor 7, and more particularly variable speed, and a second fixed capacity compressor 8, and more particularly at fixed speed, connected in parallel. Each compressor 7, 8 is for example a scroll compressor. Each compressor 7, 8 comprises a body 9 comprising a low pressure portion 11 containing a motor 12 and an oil sump 13 disposed in the bottom of the body 9, and a high pressure portion 14, disposed above the low pressure portion 11 , containing a compression stage.

The body 9 of each compressor 7, 8 further comprises a refrigerant inlet opening 15 opening into an upper portion of the low pressure portion 11, an equalizing orifice 16 opening into the oil sump 13, and a discharge port 17 opening into the high pressure portion 14.

The compression device 6 also comprises a suction line 19 connected to the evaporator 5, a first suction pipe 21 placing the aspiration line 19 in communication with the inlet orifice 15 of the first compressor 7, and a second suction pipe 22 communicating the suction line 19 with the inlet 15 of the second compressor 8. Each suction pipe 21, 22 respectively comprises a suction pipe 21a, 22a connected to the suction line 19 and a connecting sleeve 21b, 22b connected to the corresponding inlet 15. As shown in Fig. 2, the second suction line 22 includes restriction means arranged to reduce the flow section of the refrigerant in said suction line. The restriction means are arranged such that the flow section of the refrigerant at the restriction means is smaller than the flow section of the refrigerant at the inlet 15 of the second compressor 8. The restriction means are advantageously arranged near the inlet 15 of the second compressor 8. The restriction means preferably comprise an annular ring 23 fixed in the second suction pipe 22, for example by brazing or crimping. The annular ring 23 has a longitudinal through orifice centered with respect to the wall of the second suction pipe 22. It should be noted that the outer diameter of the annular ring 23 corresponds substantially to the inside diameter of the bypass tube 22a of the second suction pipe 22. According to an alternative embodiment not shown in the figures, the annular ring 23 could be fixed in the connecting sleeve 22b of the second suction pipe 22. The compression device 6 further comprises a pipe equalizing the oil level 24 connecting the first equalizing orifices 16 of the first and second compressors 7, 8 and thereby bringing into communication the oil sump 13 of the first and second compressors. The compression device 6 also comprises a discharge line 26 connected to the condenser 3, a first discharge line 27 putting the discharge line 26 into communication with the discharge orifice 17 of the first compressor 7, and a second discharge pipe 28 placing the discharge line 26 in communication with the discharge orifice 17 of the second compressor 8. The compression device 6 further comprises control means 29 arranged on the one hand for selectively controlling the respective tilting of the first and second compressors 7, 8 between a running mode and a stop mode, and secondly for modulating the speed of the motor 12 of the first compressor 7 between a minimum speed and a maximum speed. The compression device 6 also comprises an oil separator 31 mounted on the suction line 19. The oil separator 31 comprises a body 32 delimiting a separation chamber 34. The separation chamber 34 comprises a cylindrical upper portion extended by a frustoconical lower portion converging opposite the upper portion. The oil separator 31 thus constitutes a cyclone oil separator. The oil separator 31 also comprises an inlet orifice 35 opening, for example radially or tangentially, into the separation chamber 34, an oil outlet opening 36 opening into the lower end of the separation chamber 34 and a refrigerant discharge port 37 opening axially into the upper end of the separation chamber 34. The suction line 19 more particularly comprises a first connecting pipe 19a connected firstly to the outlet of the evaporator 5, and secondly to the inlet 35 of the oil separator 31 so as to allow the introduction of an oil-refrigerant mixture into the separation chamber 34, and a second conduit of 19b connection connected on the one hand to the discharge port 37 of the oil separator 31 and secondly to the first and second suction lines 21, 22. The first and second rac pipes Cord 19a, 19b have for example substantially identical diameters. Advantageously, the second connecting pipe 19b protrudes inside the separation chamber 34. The second connecting pipe 19b preferably extends from the discharge orifice 37 of the oil separator 31 to a point bypass 38, and the first and second suction lines 21, 22 extend respectively from the branch point 38 to the inlet 15 of the respective compressor. The compression device 6 finally comprises an oil return line 39 arranged to connect the oil outlet orifice 36 of the oil separator 31 to the oil sump 13 of the first compressor 7. The return line of oil 39 is more particularly arranged to open into the first suction pipe 21. The operation of the thermodynamic system 1 will now be described. When the first and second compressors 7, 8 operate, the oil-refrigerant mixture from the evaporator 5 enters the separation chamber 34 of the oil separator 31 via the first connecting pipe 19a and the Then, by the configuration of the separation chamber 34, the oil-refrigerant mixture rotates along the inner wall of the separation chamber 34, causing the mixture to centrifuge. oil-refrigerant. This results in the coalescence of the oil drops on the inner wall of the separation chamber 34, and then the gravity drop of the oil towards the lower end of the separation chamber 34, i.e. to the oil outlet port 36, and the refrigerant flow through the discharge port 37 to the inlet ports 15 of the first and second compressors 7, 8. The refrigerant flow entering the second compressor 8 is then very little loaded with oil. The separated oil in the separation chamber 34 then flows into the oil return line 39 towards the oil sump 13 of the first compressor 7 via the first suction line 21. The refrigerant flow penetrating the first compressor 7 is then very loaded with oil. Due to the high pressure prevailing in the low pressure portion 11 of the first compressor 7 (due to the presence of the restriction member 23 in the second suction pipe 22), the oil in the oil sump 13 of the first compressor 7 is driven to the oil sump 13 of the second compressor 8, via the oil level equalizing line 24, so as to balance the oil levels in the first and second compressors 7, 8.

According to an alternative embodiment of the compression device 6 shown in FIGS. 3a and 3b, the oil level equalizing line 24 comprises at least a first end portion 41 projecting inside one of the first and second compressors 7, 8. The first end portion 41 has an end wall 42 extending transversely to the longitudinal direction of the first end portion 41 and an opening 43 formed above the wall of the end portion. end 42 so that, when the oil level in the oil sump 13 of the compressor in which the first end portion 41 projects, extends above the upper level of the end wall 42, the oil flows through the opening 43 towards the other compressor. Preferably, each opening 43 extends over a portion of the side wall 44 of the corresponding end portion 41. The first end portion 41 further includes an oil return port 45 located below the upper level of the end wall 42 of the first end portion 41. This position of the return port of oil 45 makes it possible to avoid oil storage beyond a predetermined level inside the compressor enclosure in which the first end portion 41 protrudes. According to an alternative embodiment of the compression device 6, the oil level equalization line 24 comprises a second end portion 41 substantially identical to the first end portion, the first end portion 41 projecting inside one of the first and second compressors 7, 8, while the second end portion 41 projecting inside the other of the first and second compressors 7, 8.

Figures 4 and 5 show a thermodynamic system 1 according to a second embodiment of the invention which differs from that shown in Figures 1 and 2 essentially in that the oil separator 31 is mounted on the second pipe of suction 22, in that the second suction pipe 22 comprises an upstream pipe portion 46a arranged to communicate the inlet port 35 of the oil separator 31 with the suction line 19, and a portion downstream pipe 46b arranged to put the discharge port 37 of the oil separator 31 into communication with the inlet port 15 of the second compressor 10 8, and in that the oil return pipe 39 opens directly into the the oil sump 13 of the first compressor 7. According to this second embodiment of the invention, the suction line 19 extends from the outlet of the evaporator 5 to the bypass point 38, the first suction line 21 extends from the bypass point 38 to the inlet 15 of the first compressor 7, the upstream pipe portion 46a extends from the branch point 38 to the inlet port 35. the oil separator 31, and the downstream pipe portion 46b extends from the discharge port 37 of the oil separator 31 to the inlet 15 of the second compressor 8. Advantageously, the portion Downstream pipe 46b protrudes inside the separation chamber 34. According to this second embodiment of the invention, the downstream pipe portion 46b comprises the restriction means, and more particularly the annular ring 23.

According to an alternative embodiment of the second embodiment of the invention, the second suction pipe 22 could be devoid of restriction means in order to limit the manufacturing costs of the compression device. The oil separator is, according to this embodiment, arranged to maintain a pressure in the low pressure portion of the first compressor greater than the pressure in the low pressure portion of the second compressor when the first and second compressors operate simultaneously. As goes without saying, the invention is not limited to the embodiments of this compression device, described above by way of example, it encompasses all the variants.

Claims (13)

REVENDICATIONS1. Compression device (6) comprising: - at least a first compressor (7) and a second compressor (8) connected in parallel, each compressor comprising a sealed enclosure (9) comprising on the one hand a low pressure part (11) containing a motor (12) and an oil sump (13), and on the other hand an inlet opening (15) opening into the low pressure part, - a suction line (19) intended to be connected to a an evaporator outlet (5), a first suction pipe (21) arranged to put the suction line (19) in communication with the inlet (15) of the first compressor (7), a second suction line (22) arranged to communicate the suction line (19) with the inlet (15) of the second compressor (8), and - a level equalization line of oil (24) arranged to put in communication the oil pans (13) of the first and second compressors (7, 8), characterized in that the compression device (6) further comprises: - at least one oil separator (31) mounted on the suction line (19) or on the second suction line (22), the separator of oil (31) comprising an oil outlet (36), and an oil return line (39) arranged to connect the oil outlet (36) of the oil separator (31) to the oil sump (13) of the first compressor (7). The compression device according to claim 1, wherein the oil separator (31) further comprises an inlet (35) for connection to the outlet of the evaporator (5) so as to allow introducing an oil-refrigerant mixture into the oil separator, and a refrigerant discharge port (37) connected to at least the inlet (15) of the second compressor (8). 35 Compression device according to claim 2, wherein the oil separator (31) comprises a separation chamber (34), the inlet port (35) and the refrigerant discharge port (37). the oil separator (31) being respectively in communication with the separation chamber (34). 4. A compression device according to claim 2 or 3, wherein the suction line (19) comprises a first connecting line (19a) connected to the inlet (35) of the oil separator (31). and intended to be connected to the outlet of the evaporator, and a second connecting pipe (19b) arranged to put the refrigerant discharge port (37) of the oil separator (31) in communication with the first and second suction lines (21, 22). The compression device according to claim 2 or 3, wherein the second suction pipe (22) comprises an upstream pipe portion (46a) arranged to communicate the inlet port (35) of the water separator. oil (31) with the suction line (19), and a downstream pipe portion (46b) arranged to communicate the refrigerant discharge port (37) of the oil separator (31) with the inlet port (15) of the second compressor (8). The compression device according to one of claims 1 to 5, wherein the oil return line (39) is arranged to open into the first suction line (21). 7. A compression device according to one of claims 1 to 5, wherein the oil return line (39) is arranged to open into the oil sump (13) of the first compressor (7). 30 8. A compression device according to one of claims 1 to 7, wherein the second suction pipe (22) comprises restriction means (23) arranged to reduce the flow section of the refrigerant in the second pipe d suction. 35 9. A compression device according to one of claims 1 to 8, wherein the restriction means (23) are arranged to maintain a pressure in the low pressure portion (11) of the first compressor (7) greater than the pressure in the low pressure portion (11) of the second compressor (8) when the first and second compressors operate simultaneously. The compression device according to one of claims 1 to 9, wherein the first compressor (7) is a variable capacity compressor. 11. The compression device according to one of claims 1 to 10, wherein the second compressor (8) is a fixed capacity compressor. 15 12. The compression device according to one of claims 1 to 11, wherein the oil separator (31) is a cyclone oil separator. 13. Thermodynamic system (1), comprising a condenser (3), an expander (4), an evaporator (5) and a compression device (6) according to one of claims 1 to 12 connected in series.