Air cycle refrigerating/cooling system and turbine unit used therefor

1. A turbine unit used in an air cycle refrigerating/cooling system comprising:

a first heat exchanger for cooling air;

a turbine unit comprising:

a compressor for compressing the air; and

an expansion turbine for adiabatically expanding the air;

a second heat exchanger for cooling the air,

wherein the first heat exchanger, the compressor, the second heat exchanger, and the expansion turbine are cooperatively connected in series by an air path, and

wherein a compressor rotor of the compressor and a turbine rotor of the expansion turbine are attached to a common main shaft in the turbine unit in such a manner that the turbine unit drives the compressor rotor with a power generated by the turbine rotor, and

wherein the main shaft is rotatably supported by a rolling contact bearing, and

wherein part or the entirety of a thrust force applied to the main shaft is supported by an electromagnet; and

a pressure equalizing device for equalizing gas pressures at opposite ends of the rolling contact bearing comprising:

(a) a first gap defined in a part of an outer surface of the main shaft between an inner ring of the rolling contact bearing and the main shaft,

(b) a second gap provided between an outer ring of the rolling contact bearing and a first member in contact with the outer ring, or

(c) a communication passage provided within the first member configured to make contact with the outer ring.

2. The turbine unit for air cycle refrigerating/cooling according to claim 1 , further comprising:

a motor rotor attached to the main shaft; and

a motor stator confronting the motor rotor,

wherein the main shaft is rotated by a magnetic force generated by the motor stator and a power generated by the turbine rotor so as to drive the compressor rotor.

3. The turbine unit for air cycle refrigerating/cooling according to claim 1 , wherein the rolling contact bearing is a type of grease lubricant.

4. The turbine unit for air cycle refrigerating/cooling according to claim 3 , wherein a grease chamber is provided in a second member provided around the rolling contact bearing.

5. The turbine unit for air cycle refrigerating/cooling according to claim 1 , further comprising a non-contact seal for restricting a leakage between the compressor and the turbine.

6. The turbine unit for air cycle refrigerating/cooling according to claim 1 , wherein the pressure equalizing device comprises the first gap.

7. The turbine unit for air cycle refrigerating/cooling according to claim 6 , wherein the main shaft has an outer surface provided with a non-circular portion, and the first gap is formed between the non-circular portion and an inner surface of the inner ring.

8. The turbine unit for air cycle refrigerating/cooling according to claim 7 , wherein the non-circular potion is formed such that a part of the outer surface of the main shaft is processed to a flat surface or is of groove geometry.

9. The turbine unit for air cycle refrigerating/cooling according to claim 1 , wherein the pressure equalizing device comprises the second gap.

10. The turbine unit for air cycle refrigerating/cooling according to claim 9 , wherein the second gap is a notch is groove geometry.

11. The turbine unit for air cycle refrigerating/cooling according to claim 1 , wherein the pressure equalizing device comprises the communication passage.

12. The turbine unit for air cycle refrigerating/cooling according to claim 11 , wherein the communication passage is a through hole in an axial direction of the rolling contact bearing and is provided in a plurality of locations in the circumferential direction.