Lubrication of volumetrically operating expansion machines

Abstract

The present invention provides a method for lubricating an expansion machine, which method comprises: supplying of an operating medium which contains a lubricant by a vaporizer; separating of at least part of the lubricant from the operating medium which contains a lubricant and is supplied by the vaporizer; and supplying of the operating medium, which is depleted by the separation of the at least one part of the lubricant from the lubricant, to the expansion machine. Furthermore, a device is provided having a vaporizer which is configured for vaporizing an operating medium which contains a lubricant and for supplying it to an expansion machine, and having a lubricant separating device which is configured for separating at least one part of the lubricant from the operating medium which contains the lubricant and is supplied by the vaporizer to the expansion machine.

Claims

1. Method for lubricating an expansion machine, comprising supplying of a vaporized operating medium which contains a lubricant by a vaporizer, the lubricant being present in the operating medium supplied by the vaporizer in the form of oil droplets; separating of only a part of the lubricant from the vaporized operating medium which is supplied by the vaporizer; and supplying of the operating medium which is depleted in the lubricant by the separation of the part of the lubricant from the operating medium to the expansion machine such that the lubricant remaining in the depleted operating medium lubricates parts of the working chamber of the expansion machine that roll or slide on each other.

2. Method according to claim 1, furthermore comprising supplying of at least a part of the separated lubricant to the expansion machine.

3. Method according to claim 1, wherein the operating medium is provided in the form of an organic operating medium.

4. Method according to claim 1, wherein the separated lubricant is collected in a part of a lubrication device under pressure, and then flows, due to said pressure from this part to lubrication points of the expansion machine.

5. Method according to claim 4, furthermore comprising cooling down the separated lubricant before it is supplied to the lubrication points of the expansion machine.

6. Method according to claim 5, wherein the cooling down of the separated lubricant supplied to the lubrication points of the expansion machine is effected with the aid of the operating medium which contains the lubricant and which is supplied to the vaporizer.

7. Method according to claim 1, wherein the operating medium comprises a fluorinated hydrocarbon, and the lubricant comprises a synthetic ester.

8. Device having a vaporizer which is configured to vaporize an operating medium which contains a lubricant and to supply the vaporized operating medium to an expansion machine, the lubricant in the vaporized operating medium supplied by the vaporizer being present in the form of oil droplets; and a lubricant separating device which is configured to separate only a part of the lubricant from the operating medium which contains the lubricant and is supplied by the vaporizer to the expansion machine such that in the operating medium after separation of the part of the lubricant an amount of lubricant remains present to allow lubrication of parts of the working chamber of the expansion machine that roll or slide on each other.

9. Device according to claim 8, wherein the lubricant separating device is furthermore configured for supplying at least a part of the separated lubricant to the expansion machine.

10. Device according to claim 8, wherein the device is an Organic Rankine Cycle device.

11. Device according to claim 8, wherein the expansion machine is selected from the group consisting of a screw expansion machine, a scroll expander, a vane machine, and a roots expander.

12. Device according to claim 8, furthermore comprising a pipeline, wherein the lubricant separated in the lubricant separating device is guided to lubrication points of the expansion machine; and cooling ribs surrounding the pipeline.

13. Device according to claim 8, furthermore comprising a heat exchanger which is provided such that the lubricant and the operating medium are guided through it, so that heat from the lubricant is transferred to the operating medium before the operating medium is supplied to the vaporizer.

14. Steam power station, comprising: an expansion machine; and the device according to claim 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and exemplary embodiments as well as advantages of the present invention will be illustrated more in detail hereinafter with reference to the drawings. It will be understood that the embodiments do not exhaust the field of the present invention. It will be furthermore understood that some or all features described below can also be combined with each other in a different way.

(2) FIG. 1 represents a lubrication system for a volumetric expansion machine according to prior art.

(3) FIG. 2 illustrates, by way of example, a lubrication system for a volumetric expansion machine according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) As is shown in FIG. 2, a lubrication system for a volumetric expansion machine comprises, according to an example of the present invention, a lubricant separating device (below, an oil separator by way of example) 10 which is inserted between a vaporizer 20, which supplies a completely or partially vaporized operating medium, and an expansion machine 30, which is used for obtaining electric energy in cooperation with a generator 40. While in prior art, as is described above with reference to FIG. 1, a separation of the lubricant from the flow of waste steam is effected, according to the invention, at least a part of the lubricant is separated from the live steam of the operating medium which is mixed with the lubricant and supplied to the expansion machine 30. In the oil separator 10, corresponding separation plates can be provided such that in the operating medium reaching the expansion machine 30, still a sufficient amount of lubricant (lubricating oil) is present, so that a reliable lubrication of parts of the working chamber of the volumetrically operating expansion machine 30 that roll or slide on each other can be obtained. As an alternative, the separation of the lubricant in the oil separator 10 could be effected essentially completely, and a suited amount of lubricant could be supplied again to the live steam of the operating medium before the latter enters the expansion machine 30.

(5) The separated lubricating oil is collected in the oil separator 10. Since it has been brought to a high temperature after it has passed the vaporizer together with the operating medium, it is under high pressure in the oil separator 10, so that it can freely flow via a corresponding pipe to the expansion machine 30 to lubricate corresponding lubrication points of the latter there. Besides lubricating bearings, it can also remove lost heat from the bearings. To this end, it can be advantageous to cool down the lubricating oil before or during transport to the lubrication points of the expansion machine 30. This cooling can be done, for example, with the aid of cooling ribs which are provided around the pipeline to the lubrication points of the expansion machine 30. Cooling can also be done by a heat coupling to the operating medium returned by the feed pump 50 which, after expansion in the expansion machine 30, passes a condenser 60 for condensation. The heat can alternatively pass over directly from the pipeline, in which the lubricant is supplied to the lubrication points of the expansion machine, to ambient air. According to a further alternative, the lubricant and the operating medium may flow through a heat exchanger. The heat then passes over from the lubricant to the cold operating medium.

(6) By way of example, the lubricant is present in the operating medium in a dissolved form when it is being supplied to the vaporizer 20 through the feed pump 50. This can be achieved by a suited selection of the operating medium and the lubricant. For example, the operating medium can be provided in the form of a fluorinated hydrocarbon, e. g. R134a, R245fa, and the lubricant in the form of a synthetic ester, e. g. an oil of the series Reniso Triton SE/SEZ of the supplier Fuchs, where it should be taken care that no miscibility gap with a corresponding phase separation of the operating medium and the lubricant occurs in the operational temperature range. The lubricating oil will i. a. have a temperature of ebullition that is clearly higher than that of the operating medium, so that it is present in a liquid state in the form of drops in the operating steam of the operating medium after having passed the vaporizer 20.

(7) Since according to the described example, the lubricating oil separated in the oil separator 10 is under high pressure, so that, caused by the pressure, it can freely flow to the expansion machine 30, there is no need to provide a further pump device for the lubricant. Moreover, compared to prior art, a lower volume per time flows through the oil separator 10, so that the latter can have a comparatively compact design, resulting in savings of space and costs. Furthermore, the pressure loss downstream of the expansion machine 30 is reduced, and thus, the pressure drop via the expansion machine 30 can be increased compared to the conventional configuration with an oil separator 10 disposed downstream of the expansion machine 30, so that the efficiency of the expansion machine 30 can be increased. Moreover, lubricant remains directly in the live steam of the operating medium or it is supplied to the latter at live steam temperature, so that in contrast to prior art, the use of a lubricant does not lead to a reduction in the live steam temperature and enthalpy.

(8) Furthermore, the inventive lubrication of a volumetrically operating expansion machine significantly improves the start-up behavior of an ORC plant. When the ORC plant is being started, a cold operating medium is supplied to the vaporizer 20 by building up thermal pressure by evaporation. The steam is supplied to the condenser 60 in the course of the start-up operation via a bypass line (not shown in FIG. 2). Equally, a liquid lubricant, for example lubricating oil from the oil separator 10, is supplied to the condenser. The liquefied operating medium and the lubricating oil flow into a feed container from where they are supplied to the vaporizer 20 through the feed pump 50. The lubricating oil can also be supplied directly into the feed container for dissolution in the operating medium. Thus, in a time-saving manner, the complete provided lubricant supply can be guided through the vaporizer and brought to operating temperature.