A METHOD OF CONTROL OF COMPRESSORS WITH MORE THAN TWO CAPACITY STATES

• US 20160177938A1
• Filed: 02/07/2014
• Published: 06/23/2016
• Est. Priority Date: 09/23/2013
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Prins, Jan
• Granted Patent: US 10,788,030 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F04B 27/005 with two cylinders
• CPC Class Codes: F04B 39/08 Actuation of distribution members
• CPC Class Codes: F04B 49/02 Stopping, starting, unloading or idling control
• CPC Class Codes: F04B 49/03 by means of valves
• CPC Class Codes: F04B 49/16 by adjusting the capacity of dead spaces of working chambers
• CPC Class Codes: F04B 49/22 by means of valves F04B49/03 takes precedence
• CPC Class Codes: F04B 49/225 with throttling valves or valves varying the pump inlet opening or the outlet opening

Abstract

A method of operating a reciprocating compressor for a vapour compression system is disclosed. The reciprocating compressor comprises at least two cylinders and at least two unloaders, each unloader can be operated in an idle mode or in an active mode and therefore the reciprocating compressor can run in more than two capacity states. The capacity states alternates periodically between states in such a way that a substantially continuous range of effective capacities can be obtained while the individual cylinders are evenly loaded

Claims

1. A method of operating a reciprocating compressor defining two or more capacity levels, the reciprocating compressor comprising at least two cylinders and at least two unloaders, each unloader being capable of operating at least one of the cylinders to be in an idle mode or in an active mode, wherein at least some of the capacity levels of the reciprocating compressor are obtainable by two or more setting combinations of the unloaders, the method comprising the steps of:

selecting an effective capacity to be delivered by the reciprocating compressor,

selecting a first sequence of capacity levels of the reciprocating compressor, said first sequence providing the selected effective capacity,

for each of the capacity levels being used in the first sequence, selecting a second sequence of setting combinations of the unloaders which obtain the capacity level, at least one of said second sequences comprising two or more different setting combinations,

defining a final sequence of setting combinations of the unloaders, based on the first sequence of capacity levels and each of the second sequences of setting combinations of the unloaders, in such a manner that;

the capacity levels provided by the setting combinations of the final sequence provides the capacity levels of the first sequence of capacity levels, and

for each of the capacity levels, the final sequence provides the setting combinations of the corresponding second sequence of setting combinations of the unloaders, and

operating the reciprocating compressor in accordance with the final sequence.

2. The method according to claim 1, wherein the final sequence defines a cyclic switching pattern for the unloaders.

3. The method according to claim 1, wherein the final sequence is defined in such a manner that when switching from one setting combination of the unloaders to another, only one of the unloaders is switched between a position providing an idle mode of the corresponding cylinder(s) and a position providing an active mode of the corresponding cylinder(s).

4. The method according to claim 1, wherein the first sequence defines a cyclic switching pattern.

5. The method according to claim 1, wherein the first sequence comprises alternating between a first capacity level of the reciprocating compressor and a second capacity level of the reciprocating compressor.

6. The method according to claim 5, wherein the first capacity level is lower than the effective capacity to be delivered by the reciprocating compressor, and the second capacity level is higher than the effective capacity to be delivered by the reciprocating compressor.

7. The method according to claim 1, wherein the first sequence defines dwelling times of each of the capacity levels, the dwelling times being selected in such a manner that the selected effective capacity of the reciprocating compressor is obtained.

8. The method according to claim 1, wherein the step of operating the reciprocating compressor in accordance with the final sequence comprises alternating between the setting combinations of the unloaders at high frequency, thereby obtaining a substantially continuous range of effective capacities being obtainable.

9. The method according to claim 1, wherein the step of operating the reciprocating compressor in accordance with the final sequence comprises operating the unloaders by forcing at least one suction valve to remain open.

10. The method according to claim 1, wherein the step of operating the reciprocating compressor in accordance with the final sequence comprises operating the unloaders by blocking a flow of gas into at least one cylinder.

11. The method according to claim 2, wherein the final sequence is defined in such a manner that when switching from one setting combination of the unloaders to another, only one of the unloaders is switched between a position providing an idle mode of the corresponding cylinder(s) and a position providing an active mode of the corresponding cylinder(s).

12. The method according to claim 2, wherein the first sequence defines a cyclic switching pattern.

13. The method according to claim 3, wherein the first sequence defines a cyclic switching pattern.

14. The method according to claim 2, wherein the first sequence comprises alternating between a first capacity level of the reciprocating compressor and a second capacity level of the reciprocating compressor.

15. The method according to claim 3, wherein the first sequence comprises alternating between a first capacity level of the reciprocating compressor and a second capacity level of the reciprocating compressor.

16. The method according to claim 4, wherein the first sequence comprises alternating between a first capacity level of the reciprocating compressor and a second capacity level of the reciprocating compressor.

17. The method according to claim 2, wherein the first sequence defines dwelling times of each of the capacity levels, the dwelling times being selected in such a manner that the selected effective capacity of the reciprocating compressor is obtained.

18. The method according to claim 3, wherein the first sequence defines dwelling times of each of the capacity levels, the dwelling times being selected in such a manner that the selected effective capacity of the reciprocating compressor is obtained.

19. The method according to claim 4, wherein the first sequence defines dwelling times of each of the capacity levels, the dwelling times being selected in such a manner that the selected effective capacity of the reciprocating compressor is obtained.

20. The method according to claim 5, wherein the first sequence defines dwelling times of each of the capacity levels, the dwelling times being selected in such a manner that the selected effective capacity of the reciprocating compressor is obtained.