US 11,841,173 B2
Variable stage compressors
Tianlei Li, Tallahassee, FL (US); Zili Sun, Tallahassee, FL (US); and Lin Sun, Tallahassee, FL (US)
Assigned to Danfoss A/S
Filed by Danfoss A/S, Nordborg (DK)
Filed on Jun. 28, 2019, as Appl. No. 16/455,998.
Claims priority of provisional application 62/691,083, filed on Jun. 28, 2018.
Prior Publication US 2020/0003455 A1, Jan. 2, 2020
Int. Cl. F04D 27/00 (2006.01); F25B 1/053 (2006.01); F04D 29/44 (2006.01)
CPC F25B 1/053 (2013.01) [F04D 27/002 (2013.01); F04D 29/441 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A centrifugal compressor, comprising:
a first stage having a first input speed;
a second stage having a second input speed that is the same as the first input speed; and
a control system configured to determine an overall efficiency of the compressor, to determine a predicted second overall efficiency of the compressor if one of the first stage and the second stage were in a disengaged position, and to move the one of the first stage and the second stage to the disengaged position if the predicted second overall efficiency is greater than the overall efficiency,
wherein the one of the first stage and the second stage includes an impeller and a shroud spaced from the impeller and configured to guide a fluid flow through the impeller, wherein the shroud is selectively moveable between an engaged position and the disengaged position.
 
5. A method of compressing a refrigerant in a centrifugal compressor,
the method comprising:
determining an efficiency of a first stage of a compressor and an efficiency of a second stage of a compressor, wherein the first stage and the second stage have energy input at a same operating speed;
determining an overall efficiency of the compressor;
determining a predicted second overall efficiency of the compressor if one of the first and second stages were disengaged; and
disengaging the one of the first stage and the second stage by moving a shroud away from an impeller if the predicted second overall efficiency is greater than the first overall efficiency.
 
9. A refrigerant cooling system, comprising:
a main refrigerant loop in communication with a compressor, a condenser, an evaporator, and an expansion device;
the compressor comprising
a first stage having a first input speed;
a second stage having a second input speed that is the same as the first input speed; and
a control system configured to determine an overall efficiency of the compressor, to determine a predicted second overall efficiency of the compressor if one of the first stage and the second stage were in a disengaged position, and to move the one of the first stage and the second stage to the disengaged position if the predicted second overall efficiency is greater than the overall efficiency, wherein the one of the first stage and the second stage includes an impeller and a shroud spaced from the impeller and configured to guide a fluid flow through the impeller, wherein the shroud is selectively moveable between an engaged position and the disengaged position.