COMPRESSOR STABILIZER

Description

TECHNICAL FIELD

[0001] The invention relates to the field of compressors, in particular radial compressors and diagonal compressors. In particular, the invention relates to a stabilizer at the compressor inlet for improving the characteristic map width and the characteristic curve slope of a compressor stage. TECHNICAL BACKGROUND

[0002] Exhaust gas turbochargers are used to increase the performance of internal combustion engines, especially reciprocating piston engines. An exhaust gas turbocharger typically has a radial or diagonal compressor and a radial or axial turbine.

[0003] The operating range of radial and diagonal compressors is limited at lower mass flows by the surge limit / flow instability: As the compressor throttles down, the incidence angles progressively worsen until the flow separates and surge occurs. The permissible incidence angle range at which the flow is still present decreases with increasing flow Mach number. This means that the characteristic map width tends to decrease for stages with high pressure ratios and / or high displacement.

[0004] As a characteristic curve stabilization measure, a bypass in the form of an annular cavity can be provided within the compressor housing above the impeller contour, parallel to the intake port. This type of bypass is also known as a stabilizer chamber or recirculator. By using a recirculator, the mass flow at the compressor impeller inlet can be artificially increased near the surge line. A portion of the mass flow is diverted from the compressor impeller into the side chamber (bypass). This mass flow exhibits a strong swirl component (in the direction of rotation of the impeller - co-swirl). This co-swirl leads to a reduction in the work conversion in the compressor, which results in flat characteristic curves near the surge line.

[0005] Flat characteristic curves near the surge limit can lead to unexpected surge in applications with pressure pulsations (e.g., caused by the valve movement of a turbocharged internal combustion engine). For this reason, a minimum pressure increase between the operating point and the surge limit point on the operating speed curve is required. This requirement can hardly be met for stages with a high pressure ratio and a conventional bypass / stabilizer channel – due to the high energy conversion and the flat curve of the energy coefficient versus the mass flow at constant speed.

[0006] For the prior art, reference is made to document DE 10 2008 026744 A1 as an example. Document DE 10 2008 026744 A1 relates to a compressor, in particular for an exhaust gas turbocharger of an internal combustion engine, comprising a compressor housing and a compressor wheel arranged within the compressor housing, the compressor wheel inlet of which is arranged in the region of an inflow channel of the compressor housing. The compressor housing comprises a gas guide channel, the first flow opening of which is arranged upstream of the compressor wheel inlet and the second flow opening of which is arranged downstream of the compressor wheel inlet. The compressor housing comprises at least one further gas guide channel, by means of which a surge limit of the compressor is to be reduced. BRIEF DESCRIPTION OF THE INVENTION

[0007] The object of the present invention is to provide a stabilizer for a compressor, in particular a radial compressor or diagonal compressor, which is improved with respect to at least one of the disadvantages known from the prior art. Furthermore, the object of the present invention is to provide an improved compressor and an improved turbomachine, in particular an improved turbocharger.

[0008] To achieve the above-mentioned objects, a stabilizer of a compressor, in particular a radial compressor or diagonal compressor, is provided according to independent claim 1. Furthermore, a compressor with a stabilizer according to the embodiments described herein and a turbomachine, in particular a turbocharger, with such a compressor are provided.

[0009] Further aspects, advantages and features of the present invention can be found in the dependent claims, the description and the accompanying figures.

[0010] According to one aspect of the invention, a stabilizer of a compressor, in particular a radial compressor or diagonal compressor, is provided. The stabilizer comprises a first annular stabilizer chamber. The first annular stabilizer chamber surrounds a main flow channel in the intake region of a compressor wheel. The stabilizer further comprises a second annular stabilizer chamber. The second annular stabilizer chamber surrounds the first annular stabilizer chamber.

[0011] Thus, a stabilizer is advantageously provided that enables an improvement in the characteristic map width and the characteristic curve slope of a compressor stage. In particular, the stabilizer described herein, with a first and a second annular stabilizer chamber, can favorably influence the swirl distribution and the axial velocity of the flow at the impeller leading edge, and thus the surge limit.

[0012] According to a second aspect of the invention, a compressor, in particular a radial compressor or a diagonal compressor, is provided which comprises a compressor wheel and a stabilizer according to one of the embodiments described herein. In particular, the compressor wheel comprises a number N 1 of compressor wheel blades in the region of the inlet opening of a first downstream inlet channel of the first annular stabilizer chamber, wherein a number N 2 of first flow guide elements in the first downstream inlet channel is N 2 ≥ 1.5×N 1. Alternatively or additionally, a number N 3 of second flow guide elements in a second downstream inlet channel of the second annular stabilizer chamber can be N 3 ≥ 1.5×N 1.

[0013] Thus, a compressor with improved characteristic map width and characteristic curve slope can advantageously be provided.

[0014] A third aspect of the invention relates to a turbomachine, in particular a turbocharger, with a compressor according to one of the embodiments described herein, so that advantageously a turbomachine, in particular a turbocharger, is provided which is improved compared to the prior art. BRIEF DESCRIPTION OF THE CHARACTERS

[0015] The invention will be explained below with reference to exemplary embodiments illustrated in the figures, from which further advantages and modifications emerge. Herein: Figure 1 shows a schematic view of a stabilizer of a compressor according to the prior art; Figure 2 shows a schematic view of a stabilizer of a compressor according to embodiments described herein; Figure 3a shows a schematic view of a stabilizer according to a further embodiment described herein, in which a radially outer boundary of the second annular stabilizer space is formed by an insert part; Figure 3b shows a schematic view of a stabilizer according to a further embodiment described herein, in which a radially outer boundary of the second annular stabilizer space is formed by an inner compressor housing; and Figures 4 to 7 show schematic views of a stabilizer according to further embodiments described herein. DETAILED DESCRIPTION OF THE FIGURES

[0016] The following will now describe in detail the various embodiments, one or more examples of which are shown in each figure. Each example is provided for illustrative purposes and is not to be construed as limiting. For example, features shown or described as part of one embodiment may be used on or in conjunction with any other embodiment to obtain a further embodiment. The present disclosure is intended to encompass such modifications and variations.

[0017] In the following description of the drawings, the same reference numbers refer to the same or similar components. Generally, only the differences between the individual embodiments will be described. Unless otherwise noted, the description of a part or aspect in one embodiment may also refer to a corresponding part or aspect in another embodiment.

[0018] Figure 1 shows a schematic view of a stabilizer 10 according to the prior art. In particular, Figure 1a section through a housing of a compressor 20, in particular a radial compressor, such as is used for compressing air in exhaust gas turbochargers, taken along the rotational axis 11 of the compressor wheel 21. The compressor wheel 21 comprises compressor wheel blades 23. A stabilizer chamber 12 is arranged in the compressor housing 5. The stabilizer chamber 12 is connected to the main flow channel 13 via an inlet channel 15 and an outlet opening 16. The stabilizer chamber 12 is separated from the main flow channel 13 by an annular web 14. Retaining ribs 6 are arranged in the stabilizer chamber 12 and connect the annular web 14 to the compressor housing.

[0019] With reference to the Figures 2 to 7 Embodiments of a stabilizer 10 of a compressor 20 according to the present disclosure are described. The compressor may be a radial compressor or a diagonal compressor. As in Figure 2As shown, the stabilizer 10 is typically located at the compressor inlet.

[0020] According to an embodiment that can be combined with other embodiments described herein, the stabilizer 10 comprises a first annular stabilizer space 12A, as shown by way of example in Figure 2 is shown. The first annular stabilizer chamber 12A surrounds a main flow channel 13 in the intake region of a compressor wheel 21. Furthermore, the stabilizer 10 comprises a second annular stabilizer chamber 12B. The second annular stabilizer chamber 12B surrounds the first annular stabilizer chamber 12A. The first annular stabilizer chamber 12A and / or the second annular stabilizer chamber 12B can be rotationally symmetrical.

[0021] In this context, it should be noted that in the present disclosure, a "stabilizer chamber" is understood to mean, in particular, a chamber in the compressor inlet region that is configured to improve the characteristic map width of a compressor stage. In particular, the first annular stabilizer chamber 12A and the second annular stabilizer chamber 12B can be configured as recirculation chambers.

[0022] According to one embodiment, which can be combined with other embodiments described herein, an annular separating element 140 is arranged between the first annular stabilizer space 12A and the second annular stabilizer space 12B. The separating element 140 at least partially delimits the first annular stabilizer space 12A from the second annular stabilizer space 12B. By "at least partial delimitation" is meant that the separating element 140 can have one or more connecting openings 143, by means of which the first annular stabilizer space 12A can be connected to the second annular stabilizer space 12B, as is exemplified in Figure 7 is shown.

[0023] According to an embodiment that can be combined with other embodiments described herein, the annular separating element 140 is formed by a first annular web 14A, as shown by way of example in Figure 2Alternatively, the annular separating element 140 can be formed by a separating plate 141, as shown by way of example in Figure 5 is shown.

[0024] In this context, it should be noted that the annular separating element 140 is designed to provide a boundary between the first annular stabilizer space 12A and the second annular stabilizer space 12B, so that a flow in the first annular stabilizer space 12A can be substantially separated from a flow in the second annular stabilizer space 12B. In other words, the annular separating element 140 described herein can advantageously provide two different flows, namely a first flow in the first annular stabilizer space 12A and a second flow in the second annular stabilizer space 12B.

[0025] According to an embodiment that can be combined with other embodiments described herein, one or more struts 121 are arranged in the first annular stabilizer space 12A, as shown by way of example in Figure 6 The struts can be manufactured by drilling, milling, or casting.

[0026] Alternatively or additionally, one or more blades 122 may be arranged in the first annular stabilizer chamber 12A, as shown for example in the Figures 2 , 3a , 3b , and 7 is shown.

[0027] According to one embodiment, which can be combined with other embodiments described herein, the second annular stabilizer chamber 12B is vaneless. In particular, the second annular stabilizer chamber 12B can be vaneless and strutless. In other words, optionally, no vanes, in particular no flow guide vanes, and / or no struts are arranged in the second annular stabilizer chamber 12B.

[0028] According to an embodiment that can be combined with other embodiments described herein, the first annular stabilizer chamber 12A is connected to the main flow channel 13 via a first downstream inlet channel 15A and a first upstream outlet opening 16A, as shown by way of example in the Figures 2 , 3a , 3b , 5 and 6In this context, it should be noted that the first downstream inlet channel 15A can also be the inlet channel for the second annular stabilizer chamber 12B or can open into the second downstream inlet channel 15B, as shown by way of example in Figure 4 is shown.

[0029] In the present disclosure, the term "inlet channel" is understood to mean a channel that serves as a flow entry channel into a stabilizer chamber described herein.

[0030] In the present disclosure, the terms "downstream" and "upstream" refer to the main flow in the main flow channel in the intake area of ​​a compressor wheel. For clarity, the main flow direction 1 is shown in the figures.

[0031] According to one example, the first inlet channel 15A of the first stabilizer chamber 12A may be arranged downstream of a leading edge 24 of the compressor wheel 21, as shown in Figure 2 is shown. The first outlet opening 16A of the first stabilizer chamber 12A is typically arranged upstream of the leading edge 24 of the compressor wheel 21.

[0032] Similarly, the second inlet channel 15B of the second stabilizer chamber 12B is typically arranged downstream of the leading edge 24 of the compressor wheel 21. In particular, the second inlet channel 15B may be arranged downstream of the first inlet channel 15A. The second outlet opening 16B of the second stabilizer chamber 12B is typically arranged upstream of the leading edge 24 of the compressor wheel 21. In particular, the second outlet opening 16B of the second stabilizer chamber 12B may be upstream of the first outlet opening 16A of the first stabilizer chamber 12A.

[0033] According to an embodiment, which can be combined with other embodiments described herein, at least one flow guide element 17 is arranged in the first outlet opening 16A and / or in the second outlet opening 16B, as shown schematically in Fig. 5 is indicated by the dashed elements. The at least one flow guide element 17 in the first outlet opening 16A and / or in the second outlet opening 16B can be configured analogously to the at least one first flow guide element 17A and / or analogously to the at least one second flow guide element 17B, as described herein.

[0034] According to an embodiment, which can be combined with other embodiments described herein, the first downstream inlet channel 15A and / or the second downstream inlet channel 15B extends substantially in the radial direction, as shown for example in Figure 2 is shown.

[0035] In the present disclosure, the term "substantially radial" is understood to mean an angular range of ± 45° or less, in particular of ± 25° or less, relative to the radial direction r. As exemplified in Fig. 2 As shown, the radial direction r extends perpendicular to the central axis 11. According to one example, "substantially radial" is understood to mean an angular range of ±10° or less relative to the radial direction r.

[0036] According to an embodiment which can be combined with other embodiments described herein, the first upstream outlet opening 16A is inclined to the axial direction x of the main flow channel 13 by an angle α, as shown by way of example in Figure 6 Typically, the angle a is selected from a range of 20° ≤ α ≤ 90°.

[0037] According to an embodiment, which can be combined with other embodiments described herein, at least one first flow guide element 17A is arranged in the first downstream inlet channel 15A, as is shown by way of example in Figure 5 is shown. In other words, one or more first flow guide elements 17A can be arranged in the first downstream inlet channel 15A. In the event that a plurality of first flow guide elements 17A are arranged in the first downstream inlet channel 15A, the plurality of first flow guide elements 17A can be arranged circumferentially, in particular concentrically, around the central axis 11 of the main flow channel 13 or around the axis of rotation of the compressor wheel.

[0038] According to an embodiment that can be combined with other embodiments described herein, the at least one or more first flow guide elements 17A has a centering seat that is designed to arrange the one or more first flow guide elements 17A in the first downstream inlet channel 15A, in particular concentrically, around the central axis 11 of the main flow channel 13.

[0039] According to an embodiment that can be combined with other embodiments described herein, the at least one or more second flow guide elements 17B has a centering seat that is designed to arrange the one or more second flow guide elements 17B in the second downstream inlet channel 15B, in particular concentrically, around the central axis 11 of the main flow channel 13.

[0040] The centering seat can be realized, for example, by means of one or more centering elements, one or more centering pins, or a centering edge on the components to be centered.

[0041] In this context, it should be noted that one or more centering shoulders, e.g. conical or cylindrical, can be provided on the ring element 14 and / or on the ring plate 18 and / or on the compressor housing 5 and / or on the insert part 22 and / or on the inner compressor housing 20A in order to center the respective components that are connected to one another.

[0042] According to an embodiment that can be combined with other embodiments described herein, the second annular stabilizer chamber 12B is connected to the main flow channel 13 via a second downstream inlet channel 15B and a second upstream outlet opening 16B, as shown by way of example in the Figures 2 , 3a, 3b , 4 , 5 , 6 and 7 is shown.

[0043] According to an embodiment, which can be combined with other embodiments described herein, at least one second flow guide element 17B is arranged in the second downstream inlet channel 15B, as is shown by way of example in the Figures 2 , 3a , 3b , 4 , 5 , 6 and 7 is shown. In other words, one or more second flow guide elements 17B can be arranged in the second downstream inlet channel 15B. In the event that a plurality of second flow guide elements 17B are arranged in the second downstream inlet channel 15B, the plurality of second flow guide elements 17B can be arranged circumferentially, in particular concentrically, around the central axis 11 of the main flow channel 13 or around the axis of rotation of the compressor wheel.

[0044] According to one embodiment, which can be combined with other embodiments described herein, the at least one first flow guide element 17A and / or the at least one second flow guide element 17B are designed and arranged to provide a deflection grid through which flow can pass. For example, the deflection grid can be designed and arranged to provide a deflection grid through which flow can pass substantially radially.

[0045] The at least one first flow guide element 17A and / or the at least one second flow guide element 17B can, for example, be designed in the form of a spiral. Typically, the at least one first flow guide element 17A and / or the at least one second flow guide element 17B comprises a plurality of flow guide elements arranged circumferentially around a central axis 11 of the main flow channel 13. In particular, the plurality of first flow guide elements 17A and / or the plurality of second flow guide elements 17B can be arranged concentrically around the central axis 11 of the main flow channel 13.

[0046] According to an embodiment, which can be combined with other embodiments described herein, the first downstream inlet channel 15A and the second downstream inlet channel 15B are separated from each other by means of a substantially radially extending annular plate 18, as shown by way of example in Figure 6is shown. The at least one second flow guide element 17B can be formed integrally (in one piece) with the annular plate 18. Alternatively or additionally, the at least one first flow guide element 17A can be formed integrally (in one piece) with the annular plate 18.

[0047] According to an embodiment that can be combined with other embodiments described herein, the second annular stabilizer chamber 12B has a radially outer boundary formed by a part of a compressor housing 5, as shown by way of example in Figure 2 Alternatively, the radially outer boundary of the second annular stabilizer chamber 12B can be formed by an insert part 22 which is inserted into the compressor housing 5, as is shown by way of example in Figure 3aAccording to a further alternative, the radially outer boundary of the second annular stabilizer chamber 12B can be formed by an inner compressor housing 20A, for example in Figure 3b is shown.

[0048] According to one embodiment, which can be combined with other embodiments described herein, the first annular stabilizer chamber 12A has a radially inner boundary. The radially inner boundary is typically formed by a second annular web 14B, as shown by way of example in the Figures 2 , 5 and 6 and 7 is shown. The second annular web 14B delimits the first annular stabilizer chamber 12A from the main flow channel 13.

[0049] According to an embodiment that can be combined with other embodiments described herein, the first annular stabilizer space 12A is provided by an annular groove 142 arranged in a ring element 14 surrounding the main flow channel 13, as shown, for example, in Figure 4 The ring element 14 can be designed as a turning-milling component or a turning-drilling component.

[0050] According to an embodiment, which can be combined with other embodiments described herein, the first annular web 14A and / or the annular plate 18 is connected to the compressor housing 5 via at least one flow guide element, in particular via at least one second flow guide element 17B in the second inlet channel 15B, for example by means of a screw connection, as is exemplified in Figure 6is shown. The screw connection can extend through the at least one flow guide element. It should be noted that the screw connections can also be designed in a different way, i.e., so that they do not extend through the at least one flow guide element. Alternatively or additionally, other types of connection, such as pinning, shrinking, or clamping, can also be used.

[0051] Alternatively, the first annular web 14A and / or the annular plate 18 can be connected to the inner compressor housing 20A or the insert part 22 via at least one flow guide element, in particular via at least one second flow guide element 17B in the second inlet channel 15B

[0052] According to an embodiment that can be combined with other embodiments described herein, the stabilizer 10 further comprises an external gas supply 25. For example, the gas supply 25 can be connected to the first annular stabilizer space 12A and / or to the second annular stabilizer space 12B, as shown in Figure 7 is shown schematically. For example, the gas supply can be a sealing air supply or a premix gas supply.

[0053] According to a second aspect of the present disclosure, a compressor 20, in particular a radial compressor or a diagonal compressor, is provided, which comprises a compressor wheel 21 and a stabilizer 10 according to one of the embodiments described herein. According to one embodiment, which can be combined with other embodiments described herein, the compressor wheel 21 comprises a number N 1 of compressor wheel blades 23 in the region of the inlet opening of the first downstream inlet duct 15A. A number N 2 of first flow guide elements 17A in the first downstream inlet duct 15A is N 2 ≥ 1.5×N 1 . Alternatively or additionally, a number N 3 of second flow guide elements 17B in a second downstream inlet duct 15B can be N 3 ≥ 1.5×N 1. Such a selection of the number N 2 and / or number N 3 is advantageous in order to reduce the noise and vibration development during operation of the compressor.

[0054] A third aspect of the invention relates to a turbomachine, in particular a turbocharger with a compressor according to one of the embodiments described herein, so that advantageously a turbomachine, in particular a turbocharger, is provided which is improved compared to the prior art. LIST OF REFERENCE SYMBOLS

[0055] 1Main flow direction 5Compressor housing 6Strut in the stabilizer according to the state of the art 10Stabilizer 11Central axis / rotation axis of the compressor wheel 12Annular stabilizer chamber according to the state of the art 12AFirst annular stabilizer chamber 12BSecond annular stabilizer chamber 121Several struts of the first annular stabilizer chamber 122Several blades of the first annular stabilizer chamber 13Main flow channel 14Annular web / ring element 14AFirst annular web 14BSecond annular web 140Annular separating element 141Separating plate 142Annular groove 143Connecting opening in the annular separating element between the first and second annular stabilizer chambers,15Inlet channel according to the prior art 15Afirst inlet channel of the first stabilizer chamber 15Bsecond inlet channel of the second stabilizer chamber 16Outlet opening according to the prior art 16Afirst outlet opening of the first stabilizer chamber 16Bsecond outlet opening of the second stabilizer chamber 17at least one flow guide element in the first outlet opening 16Aand / or in the second outlet opening 16B 17Aat least one first flow guide element in the first inlet channel 17Bat least one second flow guide element in the second inlet channel 18ring plate extending substantially in the radial direction 20Compressor 20AIneral compressor housing 20BOuter compressor housing 21Compressor wheel 22Insert part 23Compressor wheel blades 24Leading edge of the compressor wheel 25external Sealing air supply rradial direction xaxial direction αangle of inclination of the first upstream outlet opening 16A relative to the axial direction x of the main flow channel,

Claims

1. A stabilizer (10) of a compressor, in particular of a radial compressor or diagonal compressor, comprising: - a first annular stabilizer chamber (12A), which surrounds a main flow channel (13) in the intake region of a compressor wheel (21), and communicates with the main flow channel (13) via a first downstream inlet channel (15A); and - a second annular stabilizer chamber (12B), which surrounds the first annular stabilizer chamber (12A) and communicates with the main flow channel (13) via a second downstream inlet channel (15B), wherein at least one first flow guiding element (17A) is arranged in the first downstream inlet channel (15A), and / or wherein at least one second flow guiding element (17B) is arranged in the second downstream inlet channel (15B).

2. The stabilizer (10) as claimed in claim 1, wherein an annular separating element (140) is arranged between the first annular stabilizer chamber (12A) and the second annular stabilizer chamber (12B), which separating element at least partially delimits the first annular stabilizer chamber (12A) with respect to the second annular stabilizer chamber (12B).

3. The stabilizer (10) as claimed in claim 1 or 2, wherein one or more struts (121) and / or one or more blades (122) are / is arranged in the first annular stabilizer chamber (12A).

4. The stabilizer (10) as claimed in any of claims 1 to 3, wherein the second annular stabilizer chamber (12B) is free from blades, in particular free from blades and free from struts.

5. The stabilizer (10) as claimed in any of claims 1 to 4, wherein the first annular stabilizer chamber (12A) furthermore communicates with the main flow channel (13) via a first upstream outlet opening (16A).

6. The stabilizer (10) as claimed in claim 5, wherein the first upstream outlet opening (16A) is inclined with respect to the axial direction x of the main flow channel (13) by an angle α, wherein the angle is 20° ≤ α ≤ 90°.

7. The stabilizer (10) as claimed in any of claims 1 to 6, wherein the second annular stabilizer chamber (12B) furthermore communicates with the main flow channel (13) via a second upstream outlet opening (16B).

8. The stabilizer (10) as claimed in any of claims 1 to 7, wherein the first downstream inlet channel (15A) and the second downstream inlet channel (15B) are separated from one another by means of a substantially radially extending annular plate (18), in particular wherein the at least one second flow guiding element (17B) is formed integrally with the annular plate (18).

9. The stabilizer (10) as claimed in any of claims 2 to 8, wherein the annular separating element (140) is formed by a first annular web (14A) or a separating plate (141).

10. The stabilizer (10) as claimed in any of claims 1 to 9, wherein the second annular stabilizer chamber (12B) has a radially outer boundary which is formed by a part of a compressor housing (5), or an insert (22), or an inner compressor housing (20A).

11. The stabilizer (10) as claimed in any of claims 1 to 10, wherein the first annular stabilizer chamber (12A) has a radially inner boundary which is formed by a second annular web (14B).

12. The stabilizer (10) as claimed in any of claims 1 to 11, wherein the first annular stabilizer chamber (12A) is provided by an annular groove (142), which is arranged in an annular element (14) which surrounds the main flow channel (13).

13. The stabilizer (10) as claimed in any of claims 1 to 12, further comprising an external gas supply (25), which is connected to the first annular stabilizer chamber (12A) and / or to the second annular stabilizer chamber (12B).

14. A compressor (20), in particular a radial compressor or a diagonal compressor, having a compressor wheel (21) and a stabilizer (10) as claimed in any of claims 1 to 13, wherein the compressor wheel (21) comprises a number N1 of compressor wheel blades (23) in the region of the inlet opening of the first downstream inlet channel (15A), and wherein a number N2 of first flow guiding elements (17A) in the first downstream inlet channel (15A) is N2 ≥ 1.5×N1, and / or, in particular, wherein a number N3 of second flow guiding elements (17B) in a second downstream inlet channel (15B) is N3 ≥ 1.5×N1.

15. A turbomachine, in particular a turbocharger, having a compressor (20) as claimed in claim 14.