EXPANSION MACHINE HAVING A SHAFT SEALING RING AND A VALVE

Abstract

The invention relates to an expansion machine (20), comprising an output shaft (24) and a shaft sealing ring (25) that interacts with the output shaft. The expansion machine (20) has an inflow region (21) and an outflow region (22). During operation, a working medium flows through the expansion machine (20), wherein compressed working medium flows into the inflow region (21) and expanded working medium flows out of the outflow region (22). The shaft sealing ring (25) separates a valve space (11) filled with working medium from a surrounding space (40). A valve (10) is arranged in the expansion machine (20). The pressure in the valve space (11) can be controlled by means of the valve (10).

Claims

1. An expansion machine (20) having an output shaft (24) and a shaft sealing ring (25) which interacts with the output shaft, wherein the expansion machine (20) has an inflow region (21) and an outflow region (22) and during operation is exposed to a throughflow of a working medium, wherein during operation compressed working medium flows into the inflow region (21) and expanded working medium flows out of the outflow region (22), and wherein the shaft sealing ring (25) separates a valve space (11) filled with working medium from an ambient space (40), characterized in that a valve (10) is arranged in the expansion machine (20) and the pressure in the valve space (11) is controlled by the valve (10).

2. The expansion machine (20) as claimed in claim 1, characterized in that the expansion machine (20) comprises a casing (26) and the valve (10) is arranged in the casing (26).

3. The expansion machine (20) as claimed in claim 1, characterized in that the inflow region (21) is hydraulically connected to the valve space (11) by a throttle (9).

4. The expansion machine (20) as claimed in claim 1, characterized in that the valve (10) comprises an inlet passage (12), an outlet passage (13), and a closing body (15), wherein the closing body (15) interacts with a valve seat (26a), wherein the inlet passage (12) opens into the valve space (11), and wherein the closing body (15) when being brought into contact with the valve seat (26a) closes a hydraulic connection from the inlet passage (12) to the outlet passage (13) and when being lifted from the valve seat (26a) opens the hydraulic connection.

5. The expansion machine (20) as claimed in claim 4, characterized in that the outlet passage (13) is at least indirectly hydraulically connected to the outflow region (22).

6. The expansion machine (20) as claimed in claim 4, characterized in that the valve (10) comprises a control space (60) and a control passage (14) which opens into the control space (60).

7. The expansion machine (20) as claimed in claim 6, characterized in that the control passage (14) is hydraulically connected to the ambient space (40) or to atmosphere.

8. The expansion machine (20) as claimed in claim 6 wherein the valve (10) comprises a membrane (51), and wherein the control space (60) is adjacent to the membrane (51).

9. The expansion machine (20) as claimed in claim 8, characterized in that the membrane (51) on a side opposite the control space (60) at least indirectly interacts with the closing body (15).

10. The expansion machine (20) as claimed in claim 9, characterized in that the membrane (51), with interposition of an auxiliary piston (52), interacts with the closing body (15).

11. The expansion machine (20) as claimed in claim 4, characterized in that the closing body (15) is a membrane (51).

12. The expansion machine (20) as claimed in claim 11, characterized in that an annular chamber (61) is formed in the casing (26), at least partially radially encompassing the inlet passage (12), and the outlet passage (13) opens into the annular chamber (61), wherein the valve seat (26a) is arranged between the inlet passage (12) and the annular chamber (61).

13. The expansion machine (20) as claimed in claim 11, characterized in that a control space (60), which opens into a control passage (14), is formed on the side of the membrane (51) opposite the valve seat (26a).

14. The expansion machine (20) as claimed in claim 13, characterized in that the control space (60) is formed between the membrane (51) and a cover (55), wherein the cover (55) clamps the membrane (51) on its periphery and wherein the control passage (14) is formed in the cover (55).

15. A waste heat recovery system (1) having an expansion machine (20), as claimed in claim 4, a condenser (32), a pump (30) and an evaporator (31).

16. The expansion machine (20) as claimed in claim 1, characterized in that the valve (10) comprises an inlet passage (12), an outlet passage (13), and a spherical closing body (15), wherein the closing body (15) interacts with a valve seat (26a), wherein the inlet passage (12) opens into the valve space (11), and wherein the closing body (15) when being brought into contact with the valve seat (26a) closes a hydraulic connection from the inlet passage (12) to the outlet passage (13) and when being lifted from the valve seat (26a) opens the hydraulic connection.

17. The expansion machine (20) as claimed in claim 6 wherein the valve (10) comprises a membrane (51), and wherein the control space (60) is adjacent to the membrane (51), wherein the membrane (51) consists of a metal or an elastomer.

18. The expansion machine (20) as claimed in claim 9, characterized in that the membrane (51), with interposition of an auxiliary piston (52), interacts with the closing body (15), wherein the auxiliary piston (52) is guided in a longitudinally movable manner in a guide sleeve (53).

19. The expansion machine (20) as claimed in claim 4, characterized in that the closing body (15) is a membrane (51) made from a metal or from an elastomer.

20. The expansion machine (20) as claimed in claim 13, characterized in that the control space (60) is formed between the membrane (51) and a cover (55), wherein the cover (55) clamps the membrane (51) on its periphery and wherein the control passage (14) is formed in the cover (55), and wherein the control passage (14), at an end opposite the control space (60), is hydraulically connected to the ambient space (40) or to atmosphere.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 schematically shows an expansion machine according to the invention inside a waste heat recovery system, wherein only the essential regions are shown.

[0028] FIG. 2 schematically shows an exemplary embodiment of the expansion machine, wherein only the essential regions are shown.

[0029] FIG. 3a shows an exemplary embodiment of a valve of the expansion machine with the valve in the closed position.

[0030] FIG. 3b shows an exemplary embodiment of a valve of the expansion machine with the valve in the open position.

[0031] FIG. 4 shows a further exemplary embodiment of the valve, wherein only the essential regions are shown.

DETAILED DESCRIPTION

[0032] FIG. 1 schematically shows an expansion machine 20 according to the invention inside a waste heat recovery system 1, wherein only the essential regions are shown. Arranged in the waste heat recovery system 1, in the flow direction of a working medium, are a pump 30, an evaporator 31, an expansion machine 20 and a condenser 32. The evaporator 31 is also connected to an exhaust gas pipe, which not shown, of an internal combustion engine, which is not shown.

[0033] Liquid working medium is compressed by the pump 30 and delivered to the evaporator 31 where it is evaporated by means of the thermal energy of the exhaust gas of the internal combustion engine. The evaporated working medium is then fed to the expansion machine 20 where it is expanded, releasing mechanical energy. The working medium is then liquefied again in the condenser 32.

[0034] The expansion machine 20 can in this case be for example a turbine, a piston expander or a scroll expander. In the exemplary embodiment of FIG. 1, the expansion machine 20 is a turbine with an impeller 23 and an output shaft 24.

[0035] The expansion machine 20 furthermore comprises according to the invention an inflow region 21, an outflow region 22, a shaft sealing ring 25, a valve 10, a valve space 11 and a partitioning wall 27. The compressed working medium flows through the inflow region 21 and the outflow region 22 and is expanded in the process. The mechanical energy which is released in the process is transmitted by means of the output shaft 24 to one or more users, which are not shown, for example to a turbocharger, to a gear or to a generator.

[0036] The inflow region 21 is at least indirectly hydraulically connected to the valve space 11 via a throttle 9. The valve 10 opens and closes a hydraulic connection from the valve space 11 to the outflow region 22 or to the condenser 32. The valve space 11 is sealed by means of the partitioning wall 27 in relation to the outflow region and sealed by means of the shaft sealing ring 25 in relation to an ambient space 40. The ambient space 40 can in this case be for example a gear space or even an atmospheric space.

[0037] The partitioning wall 27 is shown in FIG. 1 between the outflow region 22 and the valve space 11, but does not necessarily have to be arranged in this way. The intention is only to indicate that in the valve space 11 there is only a hydraulic inflow via the throttle 9 and a hydraulic outflow via the valve 10, and that the valve space 11 is otherwise isolated from the inflow region 21 and from the outflow region 22. Furthermore, the arrangement of the valve space 11 depends upon on which side the output shaft 24 is guided out of the expansion machine 20 since the shaft sealing ring 25 is customarily arranged at this point and also has to be arranged adjacent to the valve space 11 accordingly.

[0038] In an alternative embodiment, the valve 10 can for example also be arranged in the partitioning wall 27 or the partitioning wall 27 can be arranged between inflow region 21 and valve space 11 and the throttle 9 is then formed in the partitioning wall 27. Also important for the diverse embodiments are in this case the pressures in inflow region 21, outflow region 22, valve space 11 and ambient space 40. This is dealt with in more detail later, however.

[0039] FIG. 2 schematically shows an exemplary embodiment of the expansion machine 20, wherein only the essential regions are shown. The expansion machine 20 is constructed as a radial turbine and comprises a casing 26, in which the valve 10 is arranged. The impeller 23, the output shaft 24 which is fixedly connected to this, and the shaft sealing ring 25 are also advantageously arranged in the casing 26. Furthermore, the inflow region 21, the outflow region 22 and the valve space 11 are formed in the casing 26. In the exemplary embodiment of FIG. 2, the partitioning wall 27, which is schematically shown in FIG. 1, can therefore be considered to be a combination of impeller 23 and output shaft 24.

[0040] The valve space 11 is advantageously formed on a rear side 23b of the impeller 23, that is to say on the side which faces away from the actual flow path of the working medium through the impeller 23. As a result, a positive pressure which prevails in the valve space 11 in relation to the outflow region 22 can bring about an at least partial balance of the pressures or forces in the axial direction which act upon the impeller 23. The shaft sealing ring 25 seals the valve space 11 in relation to the ambient space 40 by a sealing lip 25a, which is arranged on the shaft sealing ring 25, interacting with the output shaft 24.

[0041] The transition from the inflow region 21 to the outflow region 22 is not a boundary which is clear to define. The working medium is expanded on the front side 23a of the impeller 23 when the impeller is exposed to a throughflow of the working medium, wherein as a result of the expansion a pressure drop is created across the impeller 23 or across the front side 23a so that in this case the inflow region 21 is not clearly to be separated from the outflow region 22 but forms a type of mixing region in which the pressure of an inlet pressure upstream of the expansion machine 20 drops to an outlet pressure downstream of the expansion machine 20.

[0042] The valve space 11 is hydraulically connected to the inflow region 21 via the throttle 9. In alternative embodiments, the valve space 11 can also be connected to the mixing region, however. Attention is to be given to the fact, however, that at the throttle 9 the region opposite the valve space 11regardless of whether it is inflow region 21 or mixing regionhas a greater pressure than the ambient space 40 during operation of the expansion machine 20.

[0043] The valve 10 comprises an inlet passage 12, an outlet passage 13, a spherical closing body 15 and a closing spring 16. The inlet passage 12 opens into the valve space 11. The outlet passage 13 advantageously opens into a region which has a lower pressure than the valve space 11, for example into the outflow region 22. The closing body 15 interacts with a valve seat 26a which is formed on the casing 26 and consequently opens and closes a hydraulic connection from the inlet passage 12 to the outlet passage 13. The closing spring 16 presses the closing body 15 against the valve seat 26a. By means of the closing spring 16, a minimum pressure can therefore be established in the valve space 11.

[0044] FIG. 3 shows an exemplary embodiment of the valve 10, wherein FIG. 3a shows the valve 10 in the closed position and FIG. 3b shows the valve 10 in the open position. The valve 10 is arranged in the casing 26 of the expansion machine 20. Alternatively, the valve 10 can also be arranged in any other casing, however.

[0045] The inlet passage 12 is formed in an inlet pipe 12a and the outlet passage 13 is formed in an outlet pipe 13a. The inlet pipe 12a and the outlet pipe 13a are pressed or screwed into the casing 26. Both the inlet passage 12 and the outlet passage 13 open into an inner space 50 which is formed in the casing 26. Arranged on the casing 26 inside the inner space 50, between inlet pipe 12a and outlet pipe 13a, is the valve seat 26a with which interacts the closing body 15 which is arranged inside the inner space 50. In the closed position of the valve 10, the closing body 15, with interposition of an auxiliary piston 52, is pressed against the valve seat 26a by a membrane 51 which in this exemplary embodiment acts like a leaf spring (FIG. 3a). In the open position of the valve 10, the closing body 15 is lifted from the valve seat 26a and therefore opens the hydraulic connection from the inlet passage 12 to the outlet passage 13 (FIG. 3b).

[0046] The auxiliary piston 52 is guided in a longitudinally movable manner in the casing 26, that is to say in the opening and closing directions of the closing body 15, by a guide sleeve 53 which is fixedly connected to the casing 26. The membrane 51 is fixedly connected on its edges by a clamping piece 54 to the guide sleeve 53 and is therefore also indirectly connected to the casing 26. A cover 55 is screwed to the casing 26 and as a result presses the clamping piece 54, with interposition of the edge of the membrane 51, against the guide sleeve 53. The membrane 51 is therefore clamped on its periphery to the casing 26. The contact between guide sleeve 53 and closing body 15 can for example be of convex design in order to optimize the automatic centering of the closing body 15 in the valve seat 26a.

[0047] A control space 60 is formed between membrane 51, clamping piece 54 and cover 55. The membrane 51 in this case seals the control space 60 against the inner space 50. A control passage 14 opens into the control space 60. The control passage 14 can be a hole in the cover 55, as in the exemplary embodiment of FIG. 3. The control passage 14, however, can for example also be formed in a control pipe which is screwed or pressed into the cover 55 or into the casing 26.

[0048] In alternative embodiments, the guide sleeve 53 and/or the clamping piece 54 can even be omitted. The corresponding functionsclamping of the membrane 51 and guiding of the auxiliary piston 52are then for example integrated into the two components comprising casing 26 and cover 55. Furthermore, it is also possible to omit the auxiliary piston 52 and to allow the membrane 51 to act directly upon the closing body 15.

[0049] Preferably, the control passage 14 is hydraulically connected to atmosphere, the inlet passage 12 is hydraulically connected to the valve space 11 and the outlet passage 13 is hydraulically connected to the outflow region 22

[0050] FIG. 4 shows a further exemplary embodiment of the valve 10, wherein only the essential regions are shown. The valve 10 is arranged in the casing 26 of the expansion machine 20. Alternatively, the valve 10 can also be arranged in any other casing, however.

[0051] The inlet passage 12 and the outlet passage 13 are arranged in the casing 26. A membrane 51 is clamped between the casing 26 and the cover 55, wherein in this exemplary embodiment the membrane 51 has the function of the closing body. The cover 55 is screwed to the casing 26. The control passage 14 is formed in the cover 55. Formed between the cover 55 and the membrane 51 is the control space 60 into which opens the control passage 14.

[0052] On the side opposite the control space 60, the membrane 51, in the closed position of the valve 10, seals the inlet passage 12 by it interacting with the valve seat 26a which is formed on the casing 26. An annular chamber 61, into which the outlet passage 13 opens out, is formed in the casing 26, at least partially radially encompassing the inlet passage 12. In the closed position of the valve 10, the hydraulic connection from the inlet passage 12 to the annular chamber 61 is closed by abutment of the membrane 51 against the valve seat 26a. In the open position of the valve 10, the membrane 51 is lifted from the valve seat 26a and as a result opens the hydraulic connection from the inlet passage 12 to the annular chamber 61.

[0053] The principle of operation of the expansion machine 20 according to the invention is as follows:

[0054] The shaft sealing ring 25 seals the valve space 11, filled with working medium, in relation to the ambient space 40. The ambient space 40 can in this case be filled for example with air or with gear oil. In the exemplary embodiment of FIG. 2, the sealing lip 25a of the shaft sealing ring 25 is curved in the direction of the valve space 11, therefore toward the expansion machine. This is a typical arrangement of the sealing lip 25a for an expansion machine 20. That is to say, a greater pressure has to prevail in the valve space 11 than in the ambient space 40 in order to press the sealing lip 25a onto the output shaft 24 and to therefore achieve a sealing effect. The valve 10 is preferably arranged in expansion machines 20 which are operated at least occasionally at negative pressure. That is to say, the outflow region 22 of these expansion machines 20 has at least occasionally a lower pressure than atmospheric pressure.

[0055] The pressure level of the valve space 11 customarily lies at the low pressure level of the expansion machine 20, that is to say at the pressure level of the outflow region 22. If the valve space 11 is therefore hydraulically connected, or able to be hydraulically connected, to the outflow region 22, then by means of a device it has to be maintained at a pressure level which lies above that of the ambient space 40 in order to obtain the sealing effect by means of the shaft sealing ring 25. Along with this, the valve space 11 also has to be maintained above the pressure level of the outflow region 22 if this drops below the pressure level of the ambient space 40.

[0056] The valve 10 fulfills this object: With the valve 10 open, the hydraulic connection from the valve space 11 to the outflow region 22 is opened, the valve space 11 will therefore adopt the pressure level of the outflow region 22. Providing the outflow region 22 has a higher pressure than, or a pressure of equal value to, the ambient space 40, a sealing effect of the shaft sealing ring 25 is consequently therefore still achieved. If the pressure in the outflow region 22 now drops below the pressure of the ambient space 40, for example because the expansion machine 20 is operated at negative pressure, then the valve 10 is closed, and along with it, the hydraulic connection from the valve space 11 to the outflow region 22.

[0057] The valve space 11 is hydraulically permanently connected via the throttle 9 to a region the pressure level of which during operation of the expansion machine 20 lies above the pressure level of the ambient space 40, for example to the inflow region 21, as shown in the exemplary embodiments of FIGS. 1 and 2. With the valve 10 closed, the pressure in the valve space 11 therefore rises to the pressure level of this region. If the valve is opened, then a pressure drop occurs at the throttle 9.

[0058] The controlling of the opening and closing movements of the valve 10, so that during operation of the expansion machine 20 a positive pressure still exists in the valve space 11 in relation to the ambient space 40, even with minimal pressure of the outlet passage 13 or of the outflow region 22 or of the condenser 32, is carried out in different ways in the various embodiments: [0059] In the embodiment of FIG. 2, the controlling is carried out by setting the closing spring 16 in relation to the seat diameter of the valve seat 26a. For example: if the condenser 32 is operated at pK=0.5 bar absolute and the ambient space 40 has atmospheric pressure, that is to say pU=1.0 bar, then the closing spring 16 needs to have a pressure maintaining function of pV=0.7 bar (in this case the hydraulic forces have to be taken into consideration on account of the seat diameter of valve seat 26a) so that on the shaft sealing ring 25 a pressure difference p=0.2 bar prevails for sealing the valve space 11 against the ambient space 40 (p=pK+pVpU). [0060] In the embodiment of FIG. 3, the controlling is carried out by the diameters of the auxiliary piston 52 and of the valve seat 26a. In variants, in which the auxiliary piston 52 is omitted, the relevant diameter of the membrane 51, on which bears the pressure of the inner space 50, is correspondingly used for controlling. [0061] In the embodiment of FIG. 4, the controlling is carried out by the diameters of valve seat 26a, annular chamber 61 and control space 60. In this case, the diameters of annular chamber 61 and control space 60 are preferably approximately of equal size. The diameter of the control space 60, however, has to be larger than the diameter of the valve seat 26a.

[0062] The rigidity of the membrane 51, 51 naturally has an effect upon the opening and closing behavior of the valve 10 in the embodiments of FIGS. 3 and 4. Ideally, the membrane 51, 51 is of soft design, for example as an elastomer membrane or even as a thin metal membrane in order to be able to design the opening and closing behavior of the valve 10 via the aforesaid diameters in a simple and robust manner.