Motor driven two-stage centrifugal air-conditioning compressor

• US 6,997,686 B2
• Filed: 12/19/2003
• Issued: 02/14/2006
• Est. Priority Date: 12/19/2002
• Status: Active Grant

• Current Assignee: R&D Dynamics Corporation
• Original Assignee: R&D Dynamics Corporation
• Inventors: Agrawal, Giridhari L., Jorgensen, Niels A.
• Primary Examiner(s): Koczo, Jr., Michael
• Application Number:
  US10/741,924
• Publication Number:
  US 20040179947A1
• Time in Patent Office: 788 Days
• Field of Search: 384/105, 384/107, 417/44.1, 417/247, 417/250, 417/350, 417/365, 417/370, 417/423.8, 417/423.12, 417/185
• US Class Current: 417/350
• CPC Class Codes: F04D 17/12 Multi-stage pumps
• CPC Class Codes: F04D 25/0606 the electric motor being specially adapted for integration in the pump
• CPC Class Codes: F04D 29/057 hydrostatic; hydrodynamic
• CPC Class Codes: F04D 29/284 for compressors
• CPC Class Codes: F04D 29/5806 Cooling the drive system
• CPC Class Codes: F04D 29/584 cooling or heating the machine F04D29/5846, F04D29/5853 take precedence
• CPC Class Codes: F04D 29/624 especially adapted for elastic fluid pumps

Abstract

A two-stage compressor for generating necessary pressure differential for air-conditioning applications with air-cooled, water-cooled and evaporative-cooled condensing systems using low-pressure refrigerant, such as R134a, is provided. A rotating assembly is mounted for rotation in a compressor housing and includes a shaft, a thrust bearing disk associated with the shaft to maintain an axial position of the rotating assembly, a motor rotor mounted on the shaft, and first and second impellers mounted for rotation with the shaft. First and second journal bearings are mounted in the compressor housing to support the shaft and maintain radial positioning of the rotating assembly. Volute housings including a spiral-shaped volute are associated with each of the impellers to collect and further discharge gas compressed by the impellers. Diffusers having air-foil shaped vanes are locate in the volute channels adjacent the discharge outlets of the impellers to aide in the discharge of gas from the impellers.

Claims

1. A compressor assembly for compressing gas, comprising:

a compressor housing having a gas inlet for receiving gas to be compressed and a gas outlet for the compressed gas;

a rotating assembly mounted for rotation about an axis within the compressor housing including;

a shaft being supported for rotation within the compressor housing;

a thrust bearing disk for maintaining an axial position of the rotating assembly along its axis within the compressor housing;

a motor rotor mounted on the shaft; and

first and second impellers mounted for rotation with the shaft at opposite ends of the shaft, each impeller having an inlet, a discharge outlet and an integral shroud cover cooperating with impeller blades to define passages for gas passing through the impellers between the inlet and the outlet;

a motor stator supported by the compressor housing and cooperating with the motor rotor for driving the rotating assembly;

first and second journal bearings mounted in the compressor housing for supporting the shaft for rotation and for maintaining a radial position of the rotating assembly with respect to its axis within the compressor housing;

first and second volute housings connected with the compressor housing and respectively associated with the discharge outlets of the first and second impellers for collecting gas discharged thereby and further discharging the gas, each said volute housing defining a logarithmic spiral-shaped volute in which discharged gas is received from the associated impeller; and

first and second diffusers associated with the first and second volute housings, respectively, each diffuser having air-foil shaped vanes located in the volute adjacent the discharge outlet of the respective impeller with which the respective volute housing is associated.

2. The compressor assembly of claim 1, further comprising a tie rod for holding the first impeller, the thrust bearing disk, the shaft and the second impeller under preload.

3. The compressor assembly of claim 1, wherein the first impeller and the second impeller are oriented to generate thrust in opposing axial directions.

4. The compressor assembly of claim 1, further comprising a transition pipe for conveying discharged gas from the first volute housing to the second impeller inlet.

5. The compressor assembly of claim 4, further comprising an injection vapor port communicating with the transition pipe for funneling vapor into the second impeller.

6. The compressor assembly of claim 1, the first and second journal bearings being oil-less foil gas bearings.

7. The compressor assembly of claim 1, further comprising first and second thrust bearings mounted in a bearing housing connected to the compressor housing, the first and second thrust bearings cooperating with the thrust bearing disk to maintain an axial position of the rotating assembly along its axis within the compressor housing.

8. The compressor assembly of claim 7, the first and second thrust bearings being oil-less foil gas thrust bearing.

9. The compressor assembly of claim 1, the compressor housing further comprising:

a cooling inlet;

a cooling outlet; and

a cooling jacket surrounding the motor stator and defining a cooling path for circulating coolant between the cooling inlet and the cooling outlet.

10. The compressor assembly of claim 9, the cooling jacket further including a corkscrew-shaped groove for circulating the coolant.

11. The compressor assembly of claim 1, further comprising a leakage path for gas passing through the compressor assembly, said path flowing from the second impeller discharge outlet, through the second journal bearing, through a gap defined between the motor rotor and the motor stator, through the first journal bearing, through the thrust bearing disk, and out the first impeller discharge outlet.

12. The compressor assembly of claim 1, the rotating assembly further comprising an encoder disk mounted on the shaft for sensing the rotational speed of the rotating assembly.

13. The compressor assembly of claim 12, further comprising a drive controller communicating with the encoder disk and the motor rotor for controlling rotational speed of the rotating assembly.

14. The compressor assembly of claim 1, further comprising a mass flow sensor positioned along the gas inlet of the compressor housing for monitoring compressor capacity.

15. The compressor assembly of claim 1, each impeller including a plurality of three-dimensional impeller blades having full inducers at the impeller inlet.

16. The compressor assembly of claim 15, each volute being axially overhung away from the respective diffuser with which it is associated.

17. A two-stage compressor assembly for compressing gas, comprising:

a compressor housing having a gas inlet for receiving gas to be compressed and a gas outlet for the compressed gas;

a rotatable shaft supported for rotation in the compressor housing by first and second journal bearings, the first and second journal bearings maintain a radial position of the rotatable shaft within the compressor housing;

a first compressor stage including;

a first impeller mounted on the rotatable shaft adjacent one end thereof and receiving gas from the compressor gas inlet through a first impeller axial inlet port and discharging gas through a first impeller discharge outlet;

a first volute in which discharged gas is collected from the first impeller and further discharged; and

a first diffuser having air-foil shaped vanes located in the first volute adjacent the first impeller discharge outlet;

a second compressor stage including;

a second impeller mounted on the rotatable shaft adjacent the other end thereof and receiving gas through a second impeller axial inlet port and discharging gas through a second impeller discharge outlet;

a second volute in which discharged gas is collected from the second impeller and further discharged through the compressor gas outlet;

a second diffuser having air-foil shaped vanes located in the second volute adjacent the second impeller discharge outlet;

a transition pipe for conveying discharged gas from the first compressor stage to the second compressor stage;

a motor for driving the shaft, the motor including a rotor mounted on the rotatable shaft between the first and second impellers and a stator supported by the compressor housing and cooperating with the rotor; and

a thrust bearing disk and first and second thrust bearings mounted on either side of the disk for maintaining an axial position of the rotatable shaft within the compressor housing.

18. The two-stage compressor assembly of claim 17, wherein the first impeller and the second impeller are oriented to generate thrust in opposing axial directions.

19. The two-stage compressor assembly of claim 17, further comprising an injection vapor port communicating with the transition pipe for funneling vapor into the second impeller.

20. The compressor assembly of claim 17, further comprising a mass flow sensor positioned along the gas inlet of the compressor housing for monitoring compressor capacity.