Compression device and a thermodynamic system comprising such a compression device

Abstract

A compression device includes a first compressor and a second compressor mounted in parallel, each compressor including a leakproof enclosure including a low pressure portion containing a motor and an oil sump, an oil level equalization conduit putting into communication the oil sumps of the first and second compressors, and control means adapted for controlling the starting and the stopping of the first and second compressors. The first compressor includes first detection means coupled with the control means and adapted for detecting an oil level in the oil sump of the first compressor. The control means are adapted for controlling the stopping of the second compressor when the oil level detected by the first detection means falls below a first predetermined value.

Claims

1. A compression device comprising: at least a first compressor and a second compressor mounted in parallel, each of the first compressor and the second compressor comprising a leakproof enclosure including a low pressure portion containing a motor and an oil sump, an oil level equalization conduit putting into communication the oil sump of the first compressor and the oil sump of the second compressor, the oil level equalization conduit including a first end portion connected to the oil sump of the first compressor and a second end portion connected to the oil sump of the second compressor, the oil level equalization conduit being configured to equalize oil levels in the oil sump of the first compressor and the oil sump of the second compressor, and a controller configured to control starting and stopping of the first compressor and the second compressor, wherein the first compressor is a variable-capacity compressor, and the second compressor is a fixed-capacity compressor, the first compressor comprises a first detector coupled with the controller, the first detector being configured to detect an oil level in the oil sump of the first compressor, the controller is configured to (i) control the stopping of the second compressor when the oil level in the oil sump of the first compressor detected by the first detector falls below a first predetermined value, and (ii) control an increase in capacity of the first compressor when the oil level in the oil sump of the first compressor detected by the first detector falls below the first predetermined value, and wherein the oil level equalization conduit includes at least a first end portion protruding inside the enclosure of a first one of the first compressor and the second compressor, the first end portion including an end wall extending transversely to a longitudinal direction of said first end portion and an aperture arranged above said end wall so that, when the oil level in the oil sump of the compressor in which the first end portion protrudes extends above an upper level of said end wall, oil flows through said aperture towards a second one of the first compressor and the second compressor.

2. The compression device according to claim 1, wherein the controller is configured to control restarting of the second compressor when a predetermined condition is met after stopping the second compressor due to the detection of the oil level below the first predetermined value.

3. The compression device according to claim 2, wherein the controller is configured to control the restarting of the second compressor after elapse of a predetermined time period.

4. The compression device according to claim 3, wherein the controller is configured to control the restarting of the second compressor when the oil level detected by the first detector attains a second predetermined value greater than the first predetermined value.

5. The compression device according to claim 1, wherein the oil level equalization conduit includes a second end portion protruding inside the enclosure of the second one of the first compressor and the second compressor, the second end portion including an end wall extending transversely to a longitudinal direction of said second end portion and an aperture arranged above the end wall of said second end portion so that, when the oil level in the oil sump of the compressor into which the second end portion protrudes extends above an upper level of the end wall of the second end portion, oil flows through the aperture of the second end portion towards the first one of the first compressor and the second compressor.

6. The compression device according to claim 5, wherein at least one of the first end portion and the second end portion includes an oil return orifice located below the upper level of the end wall of said one of the first end portion and the second end portion.

7. A thermodynamic system, comprising a circuit for circulating a coolant fluid, successively including a condenser, an expansion valve, an evaporator, and the compression device according to claim 1, connected in series.

8. A method for controlling the oil supply in the compression device according to claim 1, the control method comprising: controlling starting of the first compressor and the second compressor, detecting an oil level in the oil sump of the first compressor, controlling stopping of the second compressor when the oil level detected in the oil sump of the first compressor falls below a first predetermined value, and increasing a capacity of the first compressor when the oil level detected in the oil sump of the first compressor falls below the first predetermined value.

9. The control method according to claim 8, further comprising: controlling restarting of the second compressor when a predetermined condition is met after the second compressor has stopped due to the detection of the oil level below the first predetermined value.

10. The control method according to claim 9, wherein the predetermined condition is an elapse of a predetermined time period.

11. The control method according to claim 9, wherein the predetermined condition is a detection of a second predetermined value of the oil level in the oil sump of the first compressor, the second predetermined value being greater than the first predetermined value.

12. The control method according to claim 9, further comprising: reducing the capacity of the first compressor when the predetermined condition is met.

13. The compression device according to claim 1, wherein the oil level equalization conduit is configured to permit bi-directional fluid flow between the oil sump of the first compressor and the oil sump of the second compressor.

14. The compression device according to claim 1, wherein the oil level equalization conduit is configured to equalize oil levels in the oil sump of the first compressor and the oil sump of the second compressor under all operating conditions of the compression device.

15. The compression device according to claim 10, wherein the oil level equalization conduit is configured to equalize oil levels in the oil sump of the first compressor and the oil sump of the second compressor under all operating conditions of the compression device.

Description

(1) Anyway, the invention will be well understood by means of the description which follows with reference to the appended schematic drawing illustrating as a non-limiting example, an embodiment of this compression device.

(2) FIG. 1 is a schematic view of a thermodynamic system according to the invention.

(3) FIG. 2 is a perspective view of a compression device of the thermodynamic system of FIG. 1.

(4) FIG. 3 is a schematic sectional view of the compression device of FIG. 2.

(5) FIGS. 4a and 4b are respectively perspective and top views of an end portion of an oil level equalization conduit of the compression device of FIG. 2.

(6) FIG. 1 schematically illustrates the main components of a thermodynamic system 1. The thermodynamic system 1 may be a refrigeration system, such as a reversible refrigeration system.

(7) The thermodynamic system 1 comprises a circuit 2 for circulating a coolant fluid successively including a condenser 3, an expansion valve 4, an evaporator 5 and a compression device 6 connected in series.

(8) The compression device 6 comprises a first compressor 7 with variable capacity and more particularly with variable speed, and a second compressor 8 with fixed capacity and more particularly with fixed speed, mounted in parallel. Each compressor 7, 8 is for example a scroll compressor.

(9) Each compressor 7, 8 comprises a body 9 including a low pressure portion 11 containing a motor 12 and an oil sump 13 positioned in the bottom of the body 9, and a high pressure portion 14, positioned above the low pressure portion 11, containing a compression stage.

(10) The body 9 of each compressor 7, 8 further includes an orifice 15 for admitting coolant fluid opening into an upper portion of the low pressure portion 11, an equalization orifice 16 opening into the oil sump 13, and a discharge orifice 17 opening into the high pressure portion 14.

(11) The compression device 6 also comprises a suction line 19 connected to the evaporator 5, a first suction conduit 21 putting the suction line 19 in communication with the admission orifice 15 of the first compressor 7, and a second suction conduit 22 putting the suction line 19 in communication with the admission orifice 15 of the second compressor 8. Each suction conduit 21, 22 respectively comprises a suction tube 21a, 22a connected to the suction line 19 and a connecting sleeve 21b, 22b connected to the corresponding admission orifice 15.

(12) As shown in FIG. 3, the second suction conduit 22 comprises means for reducing the flow section of the coolant gas in said suction conduits. The reduction means are adapted so that the flow section of the coolant gas at the reduction means is smaller than the flow section of the coolant gas at the admission orifice 15 of the second compressor 8. The reduction means are advantageously positioned in proximity to the admission orifice 15 of the said compressor 8.

(13) The reduction means preferably comprise an annular ring 23 attached in the second suction conduit 22, for example by brazing or crimping. The annular ring 23 includes a longitudinal through-orifice centered relatively to the wall of the second suction conduit 22. It should be noted that the outer diameter of the annular ring 23 substantially corresponds to the inner diameter of the bypass 22a of the second suction conduit 22.

(14) According to an alternative embodiment not shown in the figures, the annular ring 23 may be attached in the connecting sleeve 22b of the second suction conduit 22.

(15) The compression device 6 further comprises an oil level equalization conduit 24 connecting the first equalization orifices 16 of the first and second compressors 7, 8 and consequently putting the oil sumps 13 of the first and second compressors in communication.

(16) The compression device 6 also comprises a discharge line 26 connected to the condenser 3, a first discharge conduit 27 putting the discharge line 26 in communication with the discharge orifice 17 of the first compressor 7, and a second discharge conduit 28 putting the discharge line 26 in communication with the discharge orifice 17 of the second compressor 8.

(17) The compression device 6 further comprises control means 29 adapted for selectively controlling the respective switching of the first and second compressors 7, 8 between an operating mode and a stopping mode on the one hand, and for modulating the speed of the motor 12 of the first compressor 7 between a minimum speed and a maximum speed on the other hand.

(18) The first compressor 7 comprises detection means 30 adapted for detecting an oil level in the oil sump 13 of the first compressor 7. The detection means 30 for example include an oil level sensor or an oil level contactor. The detection means 30 are coupled with the control means 29 for example either by wire or not. Thus, the detection means 30 may for example be electrically coupled or via Wifi or Bluetooth with the control means 29.

(19) The detection means 30 are adapted for transmitting to the control means 29 a measurement signal corresponding to the detected oil level. The control means 29 include signal processing means, such as a microprocessor, adapted for processing each measurement signal generated by the detection means 30 and for emitting a signal for controlling the stopping of the motor 12 of the second compressor 8 when the oil level detected by the detection means 30 falls below the first predetermined value.

(20) The control means 29 are further adapted for controlling the restarting of the second compressor 8 when a predetermined condition is met after the second compressor 8 has stopped due to the detection of an oil level below the first predetermined value. The predetermined condition may be an elapse of a predetermined time period, or further a detection of a second predetermined value of the oil level by the detection means 30, the second predetermined value being greater than the first predetermined value.

(21) The control means 29 are also adapted for controlling an increase in the speed of the first compressor 7 up to a predetermined speed value when the oil level detected by the detection means 30 falls below the first predetermined value, and for maintaining the speed of the first compressor 7 to the predetermined speed value until the predetermined condition is met.

(22) According to a first embodiment of the invention, the control means 29 are adapted for controlling an increase in the speed of the first compressor 7 up to the maximum speed of the latter when the oil level detected by the detection means 30 falls at least twice below the first predetermined value for a predetermined time period.

(23) According to a second embodiment of the invention, the control means 29 are adapted for controlling an increase in the speed of the first compressor 7 up to the maximum speed of the latter when the oil level detected by the detection means 30 falls below the first predetermined value within a predetermined time period starting from the restarting of the second compressor 8 after the latter has stopped due to the detection of an oil level below the first predetermined value.

(24) The compression device 6 may also comprise alarm means adapted for emitting an alarm signal when the oil level detected by the detection means 30 falls at least twice below the thrust predetermined value within a predetermined time period, or when the oil level detected by the detection means 30 falls below the first predetermined value within a predetermined time period starting from the restarting of the second compressor 8, after the latter has stopped, due to the detection of an oil level below the first predetermined value.

(25) According to an alternative embodiment of the compression device 6 illustrated in FIGS. 4a and 4b, the oil level equalization conduit 24 includes two end portions 31 respectively protruding inside the enclosure 9 of the first compressor 7 and inside the enclosure 9 of the second compressor 8. Each end portion 31 includes an end wall 32 extending transversely to the longitudinal direction of said end portion 31 and an aperture 33 made above the end wall 32 so that when the oil level in the oil sump 13 of the compressor, into which opens said end portion 31, extends above the upper level of the end wall 32, oil flows through the aperture 33 towards the other compressor. Preferably each aperture 33 extends over a portion of the side wall 34 of the corresponding end portion 31.

(26) Each end portion 31 further includes an oil return orifice 35 located below the upper level of the end wall 32 offset in portion 31. This position of each oil return orifice 35 gives the possibility of avoiding storage of oil beyond a predetermined level inside the enclosure of each compressor 7, 8.

(27) The method for controlling the oil supply in the compression device 6 according to the invention will now be described. The control method comprises the steps: controlling the starting of the first and second compressors 7, 8 with the control means 29, detecting an oil level in the oil sump 13 of the first compressor 7 with detection means 30, controlling temporary stopping of the second compressor 8 and increasing the speed of the first compressor 7 with the control means 29 when the oil level detected in the oil sump 13 of the first compressor 7 falls below the first predetermined value, maintaining the speed of the first compressor 7 to a predetermined speed value until the predetermined condition is met, and controlling the restarting of the second compressor 8 and reducing the speed of the first compressor 7 with the control means 29 when the predetermined condition is met.

(28) The control method may further comprise a step for controlling an increase in the speed of the first compressor 7 up to the maximum speed of the latter when the oil level detected by the first detection means 30 falls at least twice below the first predetermined value within a predetermined time period, or when the oil level detected by the first detection means 30 falls below the first predetermined value within a predetermined time period starting from the restarting of the second compressor 8 after the latter has stopped due to the detection of an oil level below the first predetermined value. The control method then also comprises a step for maintaining the maximum speed of the first compressor 7 for a predetermined time period.

(29) The control method may also comprise a step for emitting an alarm signal when the oil level detected in the oil sump 13 of the first compressor 7 falls at least twice below the first predetermined value within a predetermined time period, or when the oil level detected in the oil sump 13 of the first compressor 7 falls below the first predetermined value within a predetermined time period starting from the restarting of the second compressor 8 after the latter has stopped due to the detection of an oil level below the first predetermined value.

(30) As this is obvious, the invention is not limited to the sole embodiment of this compression device, described above as an example, it encompasses on the contrary all the alternative embodiments thereof.