Lubrication of expansion machines

Abstract

The invention relates to a thermodynamic circuit process device comprising a working medium having a lubricant additive; an expansion machine (5) for converting enthalpy in the working medium into mechanical energy; a multi-stage pressure-increasing apparatus (1) for the step-by-step pressurization of the working medium; a means (4) for branching a part of the working medium between two stages of the multi-stage pressure-increasing apparatus (1); and a means (4) for feeding the branched off part of the working medium to one or a plurality of bearing points of the expansion machine. The invention further relates to a corresponding method for lubricating an expansion machine in a thermodynamic circuit process device.

Claims

1. A thermodynamic circuit process device, comprising: a working medium with a lubricant additive; an expansion machine for converting enthalpy in the working medium with the lubricant additive into mechanical energy; a multi-stage pressure-increasing pump for a step-by-step pressurization of the working medium with the lubricant additive; a means for branching off a part of the working medium with the lubricant additive between two stages of the multi-stage pressure-increasing pump at a suited pressure level; and a means for feeding the branched off part of the working medium with the lubricant additive at the suited pressure level to one or more bearing points of the expansion machine, wherein the one or more bearing points receive the working medium with the lubricant additive at the suited pressure level.

2. The thermodynamic circuit process device according to claim 1, wherein said multi-stage pump is a multi-stage centrifugal pump.

3. The thermodynamic circuit process device according to claim 2, wherein said means for branching off a part of the working medium with the lubricant additive comprises a bore between two stages of the multi-stage pump.

4. The thermodynamic circuit process device according to claim 1, wherein said means for feeding the branched off part of the working medium with the lubricant additive at the suited pressure level to one or a plurality of bearing points of the expansion machine comprises one or a plurality of pipelines.

5. The thermodynamic circuit process device according to claim 2, wherein the multi-stage pump includes a plurality of impellers, and said means for branching off a part of the working medium with the lubricant additive at the suited pressure level is disposed in a conveying direction of the multi-stage pump between two directly adjacent impellers.

6. The thermodynamic circuit process device according to claim 1, furthermore comprising: a means for discharging said working medium with said lubricant additive from said bearing point or points, wherein said means for discharging the working medium is in fluid communication with an outlet of the expansion machine.

7. The thermodynamic circuit process device according to claim 1, in which the thermodynamic circuit process device is an Organic Rankine Cycle device, and/or in which the expansion machine is selected from the group consisting of a piston expansion machine, a screw expansion machine, a scroll expander, a vane machine, and a roots expander.

8. The thermodynamic circuit process device according to claim 1, wherein said working medium is provided in a form of an organic working medium, said working medium comprising a fluorinated working medium, and/or said lubricant comprising a refrigerant oil, wherein a lubricant proportion of said working medium is between 0.1 and 10 weight percent.

9. A steam power station, comprising the device according to claim 1.

10. A method for lubricating an expansion machine in a thermodynamic circuit process device, wherein said thermodynamic circuit process device comprises an expansion machine, a multi-stage pressure-increasing pump and a working medium with a lubricant additive, and wherein said method comprises the steps of: step-by-step pressurizing the working medium with the lubricant additive with the multi-stage pressure-increasing pump; branching off a part of said working medium with the lubricant additive between two stages of the multi-stage pressure-increasing pump at a suited pressure level; and feeding the branched off part of the working medium with the lubricant additive at the suited pressure level to one or more bearing points of the expansion machine for lubricating the one or more bearing points, wherein the one or more bearing points receive the working medium with the lubricant additive at the suited pressure level.

11. The method according to claim 10, wherein the branching off of a part of the working medium with the lubricant additive via a bore is effected between the two stages of the multi-stage pump.

12. The method according to claim 10, wherein the feeding of the branched off part of the working medium with the lubricant additive at the suited pressure level to one or more bearing points of the expansion machine is effected via one or a plurality of pipelines.

13. The method according to claim 10, wherein the multi-stage pump includes a plurality of impellers, and the branching off of a part of the working medium with the lubricant additive at the suited pressure level is effected in a conveying direction of the multi-stage pump between two directly adjacent impellers.

14. The method according to claim 10, further comprising the step of: discharging said working medium with said lubricant additive from the one or more bearing points, wherein the discharging of said working medium is effected in fluid communication with an outlet of the expansion machine.

15. The method according to claim 10, wherein said working medium comprises a fluorinated working medium, and/or said lubricant comprises refrigerant oil, wherein a lubricant proportion of said working medium is between 0.1 and 10 weight percent.

16. The method according to claim 10, wherein the multi-stage pump is a multi-stage centrifugal pump.

17. The thermodynamic circuit process device according to claim 1, wherein the expansion machine is selected from a group consisting of a piston expansion machine, a scroll expander, a vane machine and a roots expander.

18. The thermodynamic circuit process device according to claim 17, further comprising a means for discharging said working medium with said lubricant additive from said one or more bearing points, wherein said means for discharging the working medium is in fluid communication with an outlet of the expansion machine.

Description

DRAWINGS

(1) FIG. 1 by way of example illustrates a lubrication system for an expansion machine according to the present invention.

EMBODIMENTS

(2) In accordance with the invention, the working medium will be directly branched off from the multi-stage feed pump at a suited pressure level. The solution according to the invention advantageously combines the function of a condensate pump and of the feed pump in one housing and permits the withdrawal of liquid at a suited point, this point (number of already passed stages) determining the pressure level of the withdrawn liquid. If multi-stage feed pumps are employed, a particular property of these pumps may be utilized. The pressure increase in the multi-stage pumps is effected by stringing together several impellers, so that a pressure increase of e. g. 1 bar occurs per stage. The impellers are installed into a housing on a shaft and have equal diameters. In the direction of the shaft, a stepwise pressure increase can be observed. By tapping at a suited point, liquid, in the present case a lubricant/working medium solution, may now be withdrawn at the pressure level that is already the appropriate pressure level. Thus, no further pressure increase of this fluid must be accomplished.

(3) FIG. 1 shows a schematic diagram of a thermodynamic circuit process device according to the present invention.

(4) As is shown in FIG. 1, the thermodynamic circuit process device comprises, according to one example of the present invention, a multi-stage feed pump 1 with several impellers. The multi-stage feed pump 1 is supplied with a liquid working medium/lubricant solution, this solution entering the pump at the inlet 2. The flow stream required for the lubrication of the bearing points 9 of the expansion machine 5 is directly branched off at a suited point 3 between two adjacent impellers at a pressure level prevailing there and provided to the bearing points 9. The bearing points 9 are supplied via the lubricant supply 4, the lubricant passing the bearing points and being discharged via a discharge conduit/device 6. The discharge conduit/device 6 is in communication with the outlet of the expansion machine 5 which in turn is in communication with the condenser 7.

(5) It should be noted that both the lubricant supply 4 and the lubricant discharge conduit 6 may be integrated in the expansion machines 5 and do not have to be designed as separate conduits but may be part of the housing or the rotors. The exhaust steam and the lubricant reach the condenser 7 from which the liquefied working medium/lubricant solution is directed to the bearing points 9 and to the evaporator 8 by means of the feed pump as described. In the evaporator 8, the working medium will evaporate while the lubricant remains liquid and serves to lubricate and seal the flanks of the expansion machine 5.