LUBRICATION OF SCREW MACHINES

• US 20130052072A1
• Filed: 02/14/2011
• Published: 02/28/2013
• Est. Priority Date: 02/12/2010
• Status: Abandoned Application

• Current Assignee: City University
• Original Assignee: City University
• Inventors: Smith, Ian Kenneth, Stosic, Nikola Rudi
• Application Number:
  US13/578,348
• Publication Number:
  US 20130052072A1
• Time in Patent Office: Days
• US Class Current: 418/201.1
• CPC Class Codes: F01C 1/084 Toothed wheels
• CPC Class Codes: F01C 1/16 with helical teeth, e.g. chevron-shaped, screw type for non-parallel axes of movement F01C3/00
• CPC Class Codes: F01C 17/00 Arrangements for drive of co-operating members, e.g. for rotary piston and casing
• CPC Class Codes: F01C 21/045 Control systems for the circulation of the lubricant
• CPC Class Codes: F04C 2210/242 Steam
• CPC Class Codes: F04C 2230/91 Coating
• CPC Class Codes: F04C 2240/52 for assemblies with supports on both sides
• CPC Class Codes: F04C 2240/54 Hydrostatic or hydrodynamic bearing assemblies specially adapted for rotary positive displacement pumps or compressors
• CPC Class Codes: F04C 29/04 Heating; Cooling of machines or engines in general F01P; Heat insulation heat insulation in general F16L59/00
• CPC Class Codes: F05C 2251/14 Self lubricating materials; Solid lubricants
• CPC Class Codes: F16C 17/02 for radial load only
• CPC Class Codes: F16C 17/14 specially adapted for operating in water
• CPC Class Codes: F16N 15/04 with water bearings working in water F16C

Abstract

A screw machine for use with a working fluid with a liquid phase present comprises rotors having meshed, lubricated helical formations. The rotors have an ‘N’ profile as disclosed in WO 97/43550. In use, lubrication of the helical formations of the rotors and optionally of the rotor bearings is achieved substantially exclusively with the liquid phase of the working fluid.

Claims

1. A screw expander for use with wet steam as a working fluid, the expander comprising two or more rotors having meshed, lubricated helical formations, wherein the rotors have an ‘

N’

profile as defined herein and, in use, water entrained in the wet steam working fluid is substantially exclusively responsible for lubricating the helical formations of the rotors.

2. The expander of claim 1, wherein the helical formations are coated with a low-friction coating.

3. The expander of claim 2, wherein the coating comprises a carbide phase and a carbon phase.

4. The expander of any preceding claim, wherein the rotors are supported by at least one bearing that is also substantially exclusively lubricated, in use, by water.

5. The expander of claim 4, wherein the bearing is a hydrodynamic bearing.

6. The expander of claim 4, wherein the bearing is a rolling-element bearing.

7. The expander of any of claims 4 to 6, wherein the bearing is lubricated by water derived from the wet steam working fluid.

8. The expander of any preceding claim, wherein the rotors are synchronised by synchronising torque transmitted from one rotor to another via their meshed helical formations.

9. The expander of claim 8 and having no timing gears acting between the rotors.

10. The expander of any preceding claim, further comprising a thrust piston acting against axial loads on a rotor.

11. The expander of claim 10, wherein the thrust piston is acted on by pressure of the wet steam working fluid.

12. The expander of any preceding claim, wherein the lubricating water entrained in the wet steam working fluid is derived from the wet steam entering the expander, substantially without prior addition of further water to the wet steam.

18. A power generator comprising the screw expander of any of claims 1 to 12, or having a screw expander operating in accordance with the method of any of claims 12 to 17.

13. A method of lubricating a screw expander when using wet steam as a working fluid, the expander comprising two or more rotors having meshed, lubricated helical formations, the rotors having an ‘

N’

profile as defined herein, wherein the method comprises lubricating the helical formations of the rotors substantially exclusively with water entrained in the wet steam working fluid.

14. The method of claim 13, comprising using water to lubricate a bearing that supports the rotors.

15. The method of claim 14, comprising deriving from the wet steam working fluid the water that lubricates the bearing.

16. The method of any of claims 13 to 15, comprising synchronising the rotors by transmitting synchronising torque from one rotor to another via their meshed helical formations.

17. The method of any of claims 13 to 16, wherein the lubricating water entrained in the wet steam working fluid is derived from the wet steam entering the expander, substantially without prior addition of further water to the wet steam.