Abstract
The present application discloses a diffuser system and a centrifugal compressor comprising the same. The diffuser system comprises: a passage through which a compressed gas is flowable; and a wall defining the passage, the wall comprising a movable part which is driven to enter the passage so as to change a flow area of the passage, wherein the movable part comprises an elastomer configured to expand to guide the flow of the compressed gas when at least a portion of the movable part enters the passage, and to retract when the movable part withdraws from the passage. The diffuser system involved in the present application re-orients a flow route of the compressed gas in the passage.
Claims
1. A diffuser system, comprising: a passage through which a compressed gas is flowable; a wall defining the passage, the wall comprising a movable part which is driven to enter the passage so as to change a flow area of the passage, wherein the movable part comprises an elastomer configured to expand to guide the flow of the compressed gas when at least a portion of the movable part enters the passage, and to retract when the movable part withdraws from the passage.
2. The diffuser system of claim 1, wherein the elastomer forms a streamline surface in the passage after expanding.
3. The diffuser system of claim 1, wherein the elastomer is a membrane element attached to the wall.
4. The diffuser system of claim 3, wherein the membrane element is made of rubber material or metal material, or wherein the membrane element comprises a core made of metal material and a wrap structure in which the core is contained, the wrap structure being made of rubber material.
5. The diffuser system of claim 4, wherein the membrane element is made of hydrogenated nitrile butadiene rubber.
6. The diffuser system of claim 1, wherein the movable part of the wall further comprises a piston for pushing the elastomer, the piston being arranged within a groove which forms on the wall and is sealed by the elastomer; the elastomer, the wall and the piston are configured to be annular.
7. The diffuser system of claim 6, wherein the piston is of a pneumatic drive, or is a hydraulic drive such as oil hydraulic drive.
8. The diffuser system of claim 7, wherein the piston has a rigid head in contact with the elastomer, the head having a section shape with an arc surface.
9. The diffuser system of claim 6, wherein a pressure balance hole is arranged at the bottom of the groove, the pressure balance hole being in communication with the passage.
10. A centrifugal compressor, comprising: an impeller, a volute arranged on a radially outward side of the impeller, and the diffuser system of claim 1, wherein the passage is positioned between the impeller and the volute.
Description
BRIEF DESCRIPTION OF FIGURES
[0019] Referring to the elaboration of following specific embodiments in combination with the figures, one could understand the present application more sufficiently. And, the identical reference signs in the figures invariably indicate the same elements illustrated by the figures. Details are as follows:
[0020] FIG. 1 is a sectional diagram of the centrifugal compressor in an operating state involved in the present application;
[0021] FIG. 2 is a sectional diagram of the centrifugal compressor in another operating state involved in the present application;
[0022] FIG. 3 is a partial enlargement of the involved diffuser system of the centrifugal compressor illustrated in FIG. 2;
[0023] FIG. 4 is a diagram shown from another angle of the diffuser system of the centrifugal compressor involved in the present application;
[0024] FIGS. 5A and 5B are sectional diagrams of the first embodiment of the piston in the diffuser system involved in the present application;
[0025] FIGS. 6A and 6B are sectional diagrams of the second embodiment of the piston in the diffuser system involved in the present application;
[0026] FIGS. 7A and 7B are sectional diagrams of the third embodiment of the piston in the diffuser system involved in the present application; and,
[0027] FIG. 8 is a diagram of another embodiment of the diffuser system involved in the present application.
EMBODIMENTS
[0028] To help one skilled in the art exactly understand the subject claimed by the present application, the following is the elaboration made in combination with the figure about the embodiments of the present application.
[0029] The diffuser system involved in the present application is intended for boosting the compressed fluid in compressors, especially in centrifugal compressors. The centrifugal compressors are widely employed in industries, and the objects of compression can be such as air or nitrogen gas, or such as liquid refrigerant used in refrigeration compressors. In the application of refrigeration compressors, ideally, liquid refrigerant and/or lubricating oil is not expected to enter the refrigeration compressor, but in reality, the compressor “suction with liquid” still occurs, so the “gas” mentioned in the present application in fact will entrain a small amount of liquid. Known from FIGS. 1-2, a compressor 1 comprises an impeller 3 and a volute 5 arranged on a radially outward side of the impeller 3. The diffuser system 7 is positioned between the impeller 3 and the volute 5. After departing from the impeller 3, a compressed gas will pass through the diffuser system 7 and then enter the volute 5. The dotted line with an arrow in the figures shows the flow route of the compressed gas. In the diffuser system 7, the compressed gas is boosted to convert kinetic energy to pressure energy, and further is boosted within the volute 5.
[0030] Known from the embodiment shown in the figures, the diffuser system 7 can regulate the passing flow of the compressed gas while boosting pressure of the compressed gas in a certain loaded work condition so as to increase the efficiency of compressors. One mode of implementation is that the diffuser blocks the passage where the compressed gas passes. FIG. 1 shows a work state of the compressor when the passage is fully open, i.e., the diffuser stops flow regulation; and, FIG. 2 shows a work state of the compressor when the passage is partially blocked, i.e., the diffuser carries out flow regulation. In the compressor, a passage 12 is an annular space defined by walls 14 of two sides (or called partitions). The wall 14 of one side (the wall 14 of the right in the figure) comprises a movable diffuser part 16 and a fixed diffuser part 18 (hereinafter “movable part 16” and “fixed part 18”). The movable part 16 moves in the passage 12, which can change the flow of the compressed gas. The movable part 16 is driven to translate towards the passage 12 and gradually blocks a portion of the passage 12 so as to reduce a flow area through which the compressed gas passes (i.e., the courses shown from FIG. 1 to FIG. 2). On the contrary, the movable part 16 moves in the opposite direction and gradually withdraws from the passage 12 so as to gradually enlarge the flow area through which the compressed gas passes (i.e., the courses shown from FIG. 2 to FIG. 1).
[0031] FIG. 3 is a partial enlargement of the involved diffuser system illustrated in FIG. 2. Referring to FIG. 3, the movable part 16 comprises an elastomer 24 and a piston 22. The elastomer 24 is a membrane element and is attached onto the wall. The membrane element can be made of rubber material or metal material, or the combination of these two materials. If rubber material is employed, the material of rubber can additionally have an elastic sheet adhering thereon, or can be modified—for example, fibre reinforced materials of high strength, to increase the strength of the membrane element. Alternatively, the membrane element can have a composite body with materials, the body having a core made of metal material and a wrap structure wrapping the core and made of rubber material. The membrane element can be made of hydrogenated nitrile butadiene rubber (HNBR), which has a fine elastic contractibility as well as a relative prolonged lifetime, and is compatible with a customized refrigerant. For example, but not limited to it, the membrane element can be made of Parker N1206 or Parker N1173 produced by Parker; or the membrane element can be made of Novapress850 produced by Frenzelit. The deformation of the elastomer 24 is caused by a movement of a piston 22. The piston 22 is further moved and driven by a drive system 26 at its back side. When the piston 22 moves forwards (see the hollow arrow shown in the figure), the elastomer 24 is pushed into the passage 12. At this moment, the elastomer 24 deforms to expand and make a compressed gas follow and pass its deformed expanding surface, as the dotted line shown in the figure. In the embodiment illustrated by the figure, the elastomer 24 deforms in the passage 12 to form a streamline front surface; and, the compressed gas passes along the surface. A surface shaped like this reduces the resistance against a flowing gas, thereby being able to increase the pneumatic performance and boosting efficiency. In this manner, the deformed elastomer 24 in the passage 12 can establish for a compressed gas an ideal pass route of the compressed gas. When the piston 22 moves in the opposite direction, the elastomer 24 will return to a flat state due to an elastic force after the elastomer 24 withdraws completely from the passage 12.
[0032] The piston 22 is received in a groove 28 of the wall. FIG. 4 illustrates at another angle the structure of this portion of the diffuser system. Known from the figure, the two circles formed by dotted lines define the groove 28 as an annular shape. Thus, the piston and the elastomer 24 received in the groove 28 are both of annular elements. The radial dimension of the elastomer 24 is slightly larger than that of the groove 28 so as to cover and seal the groove 28. An inner diameter edge part and an outer diameter edge part of the elastomer 24 are respectively attached onto the fixed part 18 of the wall 14. A middle part between the inner diameter edge and the outer diameter edge parts, i.e., an expanding part (the deformed shape shown in FIG. 3), can form a fine transition with the fixed part of the wall. As shall be understood, the elastomer 24 can be bonded onto the wall 14 by multiple known means or techniques.
[0033] The elastomer 24 can be driven by the piston 22 and the drive system 26 at the back side of the piston 22; for example, it can be driven directly by an existing drive system of a variable diffuser, or by other drive devices. As for the drive system 26, a pneumatic drive, a hydraulic drive (e.g., an oil hydraulic drive) or other known drive means can be employed. The elastomer 24 is driven to enter the passage and deforms, which re-orients the flow route of a compressed gas while changing the flow area of the compressed gas within the passage.
[0034] The movable part of the variable diffuser with a streamline shape established within the passage 12 will be helpful for flow of the compressed gas. The streamline shape can be enabled by modifying the back of the elastomer 24, i.e., the head of the piston. When the piston pushes the elastomer 24 into the passage 12, the head is in contact with the elastomer 24. Thus, a particular shape of the head can help the elastomer 24 to form an ideal shape. To enable the elastomer 24 to expand to be a streamline shape, the head of the piston 22 is designed to have an arc surface. FIGS. 5-7 show several shapes of the head of the piston 22 in the form of sections. The arc surface can be a symmetrical curve 42 shown in FIG. 5(a), which occupies the surface of the entire head of the piston; a curve 42′ of FIG. 5 (b) differs from FIG. 5 (a) in the radius of curvature—the radius of curvature of the curve 42′ is smaller than the curve 42. FIG. 6 (a) shows another arc surface, in which curves 46 are at the two ends connected by a beeline 48 that is straight. Certainly, an asymmetrical shape can also be allowed; that is, the curve 46 is arranged only at one end, e.g., at one end substantially facing a compressed gas. And, the curve 46 can be a round chamfer like the round chamfer with 45° arc shown in the figures, or be a round chamfer with different degree of arc. The surface illustrated by FIG. 6 (b) is also formed by connecting two curves 46′ with a beeline 48′, wherein the curves 46′ have a radius smaller than the curve 46 of FIG. 6 (a). FIG. 7 (a) further shows another arc surface, which comprises an oblique line 44 and a beeline 45 and wherein the oblique line 44 appears at the lower end, i.e., it faces a compressed gas. Further, the oblique line 44 is a flat chamfer, e.g., a flat chamfer with 45°, which is directly connected with the beeline 45 (as is illustrated in the figure) or smoothly and transitionally connected with the beeline 45. Here, the “arc surface” indicates that, after a piston with this shape acting on the elastomer 24, the elastomer 24 forms a shape with a streamline expanding surface. Depending on an elastic coefficient of the elastomer or a process of the elastomer bonded to the wall, the piston is driven to partially or fully contact with the elastomer. FIG. 7(a) shows an asymmetrical shape while FIG. 7(b) shows a symmetrical one, i.e., two oblique lines 44′ and a beeline 45′ connecting them. As shall be understood, the surface shape of a head of the piston is not limited to aforesaid examples, which may be other shapes that enable the elastomer 24 to deform to have a streamline surface.
[0035] FIG. 8 is a diagram of another embodiment of the diffuser system involved in the present application. The only difference lying between this embodiment and that illustrated by FIG. 3 is: a pressure balance hole 32 is provided at the bottom of the groove 28 and the pressure balance hole 32 is in communication with the passage 12 via a conduit 34. In the design of this type, the groove 28, due to the pressure balance hole 32, keeps a pressure the same as that of the passage 12, which helps the piston 22 to push the elastomer 24 into the passage 12; that is, it is not necessary for the drive system 26 to overcome an enormous resistance. In the embodiment illustrated by the figure, the pressure balance hole 32 is arranged at an end close to the impeller, i.e., the end substantially facing a compressed gas. One could think of that the pressure balance hole may also be arranged at an end close to the volute, i.e., the end substantially deviating from a compressed gas; and, at this end, the pressure of the compressed gas having been boosted will be larger to facilitate the drive system to output a drive force smoothly.
[0036] Although specific embodiments of the present application are already illustrated and elaborated to explain the principle of the present application, one shall understand that the present application may be implemented by other means but without a deviation from such a principle.
