JP2009264136A - Diffuser for compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diffuser for a compressor, improving the compression efficiency of the compressor such as a barrel compressor without increasing a pressure loss by a simple structure. <P>SOLUTION: In each diffuser 2 for the compressor, each diffuser vane 4 is provided along a swirl flow S of compressed gas in a diffuser disk 3, and a gas channel 5 is formed between the vanes 4. The downstream side of the diffuser vane 4 extends continuously along the outside shape of each diffuser vane 4. In the plan view of the longitudinal section of the compressor including an axis C, the extended diffuser vane 4 has a curved portion 4b to be terminated immediately before the compressed gas is directed to an outlet channel 8. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a diffuser of a compressor such as a barrel-type compressor (hereinafter also simply referred to as a compressor) in which a housing for housing an impeller has a barrel shape, and more specifically, increases pressure loss with a simple structure. The present invention relates to a diffuser for a compressor that can improve the compression efficiency of a barrel type compressor.

  If the swirl speed at which the gas compressed by the compressor flows out of the impeller is large and is not suitable for sending the gas flow directly to the spiral chamber or the outlet channel, the gas flow is decelerated and the dynamic pressure is reduced. In order to restore most of the pressure to static pressure, a diffuser vane (hereinafter also simply referred to as a vane) is formed on the diffuser disk (hereinafter also simply referred to as a disk) along the flow of compressed gas. Usually, a diffuser having a gas flow path is provided.

  A conventional diffuser of a compressor will be described with reference to FIGS. 4 and 5 by taking a barrel type compressor as an example. FIG. 4 is a longitudinal sectional view of an essential part for explaining a diffuser of a barrel type compressor according to a conventional example, FIG. 5 (a) is a plan sectional view showing a part of arrow XX in FIG. FIG.5 (b) is a longitudinal cross-sectional view which shows arrow YY of Fig.5 (a).

  The gas sucked from the upper part of the axial center C of the barrel type compressor forms a swirl flow S that goes downward of the axial center C of the compressor according to the rotation of the impeller 11, and the outlet flow path part through the diffuser 12. 18 is discharged. The diffuser 12 is provided with a diffuser vane 14 along a swirl flow S of compressed gas in an annular diffuser disk 13, and a gas flow path 15 is formed between the vanes 14. The compressed gas compressed by the impeller 11 flows along the narrow gas flow path 15 formed between the vanes 14 and is decelerated, and after recovering most of the dynamic pressure to static pressure, the outlet flow path The unit 18 is configured to be discharged.

  Such a diffuser 12 generates a complicated flow as the swirl flow S in the compressor is decelerated. Therefore, a short path or a separation flow is generated between the gas flow paths 15 in which the vanes 14 are not formed. As a compressor, the compression efficiency may be reduced. For this reason, various diffusers for preventing the compression efficiency of the compressor from being lowered have been proposed.

  Next, an example of improving the compression efficiency of the diffuser according to the prior art will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing an embodiment of a diffuser according to Prior Art 1, and FIG. 7 is a plan cross-sectional view omitting a part of the description showing an embodiment of the structure of a vaneless portion of a compressor according to Prior Art 2. is there.

  First, as shown in FIG. 6, the blade thrust diffuser of the centrifugal compressor according to the related art 1 has a flow path on one side plate 27 of a pair of side plates 27 and 32 arranged to face each other in the axial direction of the blower fan 22. The blades 29 are integrally provided to boost the pressure of the fluid 25 passing through the blower 26 and lead it to the blower casing 24, and the other side plate 32 is configured to be movable toward the one side plate 27. A communication hole 35 is formed in the other side plate 32 to form the portion 34 and communicate the outlet portion 26 a of the flow path 26 and the cavity portion 34.

  The other side plate 32 can be pressed against the vane 29 by the pressure difference between the front and back sides of the side plate 32 to narrow the gap between the vane 29 and the other side plate 32, so that the flow of the fluid 25 that bypasses the vane 29 The efficiency of the centrifugal compressor 21 is improved (see Patent Document 1).

  Next, the structure of the vaneless portion of the compressor according to the related art 2 is a compressor in which the vaneless portion 47 serving as a connection space is arranged between the centrifugal impeller 41 and the diffuser 42 as shown in FIG. On the inner surface of the side wall that surrounds the vane-less portion 47 at a position spaced apart in the rotation axis direction, a guide wall 48 that protrudes inward along the direction of the inlet air flow in the diffuser 42 is arranged, and a branch flow or separation different from the main flow While suppressing the secondary flow by a flow, the generation | occurrence | production of a peeling phenomenon is suppressed and the compression efficiency of a compressor is improved (refer patent document 2).

Furthermore, although not shown in the drawing, the multistage centrifugal compressor according to Prior Art 3 has a plurality of guide vanes in the circumferential direction in the flow path of the interstage suction nozzle, and each guide vane and each stationary vane By providing an annular partition plate of a predetermined length between the two, the gas flow direction is corrected in the direction along each side surface of the diffuser and mixed, and the stationary blade and the guide blade are smooth at the merging point. Each gas is allowed to pass through to reduce loss due to gas mixing (see Patent Document 3).
Japanese Patent Laid-Open No. 5-71498 JP-A-9-177698 JP-A-6-257590

  However, the above prior art 1 increases the manufacturing cost due to the complicated structure, and the side plate 32 cannot move due to clogging of fine dust in the sliding portion between the other side plate 32 and the casing 30 or the occurrence of rust. May be possible. Further, since the conventional technology 2 has a small distance in the flow direction of the vaneless portion 47, there is a question as to how much efficiency is improved. Furthermore, the prior art 3 can be applied only to a multistage compressor.

  Accordingly, an object of the present invention is to provide a compressor diffuser capable of improving the compression efficiency of a compressor such as a barrel compressor without increasing pressure loss with a simple structure.

  In order to achieve the above object, the means adopted by the diffuser of the compressor according to claim 1 of the present invention is provided with a diffuser vane along the swirling flow of the gas compressed in the diffuser disk, and between these vanes. In the compressor diffuser in which the gas flow path is formed, the downstream side of the diffuser vane extends continuously along the outer shape of the diffuser vane, and the longitudinal section including the axial center of the compressor is planar. When viewed, the extended diffuser vane is characterized in that it is terminated with a bent portion just before the compressed gas goes to the outlet channel.

  The means adopted by the diffuser of the compressor according to claim 2 of the present invention is the diffuser of the compressor according to claim 1, wherein the gas flow path is a plan view of a plane cross section orthogonal to the axial center of the compressor. In this case, the gas flow path formed between the diffuser vanes is formed in the swiveling direction with respect to the diffuser disk, and is temporarily widened in the downstream direction.

  The means employed by the compressor diffuser according to claim 3 of the present invention is the compressor diffuser according to claim 1 or 2, wherein the upper surface of the bent portion of the diffuser vane includes the axial center of the compressor. When viewed from above, the gas channel has a bending radius that is twice or more the height of the gas flow path.

  The means adopted by the compressor diffuser according to claim 4 of the present invention is the compressor diffuser according to any one of claims 1 to 3, wherein the gas flow path is a shaft of the compressor. A space sandwiched between the upper surface of the diffuser disk and the lower end surface of the scroll in the central direction, and an upstream disk flow path formed by a space between the diffuser vanes in the circumferential direction perpendicular to the axial center; The space formed between the inner wall surface of the compressor housing and the lower end surface of the scroll in the radial direction of the bent portion, and the downstream formed by the space between the diffuser vanes in the circumferential direction perpendicular to the axis. It has a cylindrical flow path part of the side, It is characterized by the above-mentioned.

  According to the diffuser of the compressor according to claim 1 of the present invention, a diffuser vane along a swirling flow of gas compressed in the diffuser disk is provided, and a gas flow path is formed between these vanes. In the diffuser, the diffuser vane has a downstream side continuously extended along the outer shape of the diffuser vane, and the diffuser extended when the longitudinal section including the axial center of the compressor is viewed in plan view. Since the vane is terminated with a bent portion just before the compressed gas heads toward the outlet channel, it prevents the efficiency from being lowered due to the turbulence in the bent portion of the gas channel, such as a barrel compressor. The compression efficiency of the compressor can be improved.

  Moreover, according to the diffuser of the compressor which concerns on Claim 2 of this invention, when the planar cross section orthogonal to the axial center of a compressor is planarly viewed, the said gas flow path forms in a turning direction with respect to the said diffuser disk. Since the gas flow path formed between the diffuser vanes is widened in the downstream direction for a while, the compressed gas is decelerated without disturbing the flow as it goes downstream of the gas flow path, and the static pressure is reduced. Can promote recovery.

  Furthermore, according to the diffuser of the compressor which concerns on Claim 3 of this invention, when the bending part upper surface of the said diffuser vane planarly views the longitudinal cross section containing the axial center of a compressor, it is the height of the said gas flow path. Since the bending radius is twice or more, it is possible to reduce the increase in pressure loss and improve the compression efficiency of the compressor.

  Furthermore, according to the diffuser of the compressor according to claim 4 of the present invention, the gas flow path is sandwiched between the upper surface of the diffuser disk and the lower end surface of the scroll in the axial direction of the compressor, and An upstream disk passage formed by a space between the diffuser vanes in a circumferential direction orthogonal to the axis, and an inner wall surface of a compressor housing and a lower end surface of the scroll in a radial direction at the bent portion And a downstream cylindrical flow path formed by the space between the diffuser vanes in the circumferential direction perpendicular to the axis, and thus constitutes the gas flow path Since the disk flow path portion and the cylindrical flow path portion are formed by a combination of members of the compressor according to the conventional example excluding the diffuser, it is possible to avoid a significant increase in manufacturing cost and a complicated configuration.

  First, a diffuser of a compressor according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a longitudinal sectional view of a main part for explaining a diffuser of a barrel type compressor according to an embodiment of the present invention, and FIG. 2 (a) is shown by omitting a part of an arrow AA in FIG. FIG. 2B is a cross-sectional plan view, and FIG. 2B is a vertical cross-sectional view taken along the line B-B in FIG.

  In the design of a compressor such as a barrel compressor, the diffuser may not be provided if the size of the weight loss operating range is more important than the efficiency, but if the efficiency is important, the diffuser is provided to improve the compression efficiency. It is normal to try.

  The gas sucked from the upper part of the barrel compressor in the axial center C direction is accelerated while forming a swirl flow S directed downward of the compressor shaft C as indicated by an arrow according to the rotation of the impeller 1. It is discharged in the outer peripheral direction of the car 1. The gas released in the outer peripheral direction of the impeller 1 is discharged to the outlet channel portion 8 through the diffuser 2. In this diffuser 2, a diffuser vane 4 along the swirl flow S of the released gas is provided on an annular diffuser disk 3, and a gas flow path 5 is formed between these vanes 4.

  In the diffuser 2 of the compressor according to the embodiment of the present invention, the downstream side of the diffuser vane 4 is continuously extended along the shape of the gas flow path 5. Further, in FIG. 1, which is a plan view of a longitudinal section including the axial center C of the compressor, the extended diffuser vane 4 is perpendicular to the axial center C immediately after the compressed gas flows into the vane 4. The straight portion 4a is formed, and immediately before going to the outlet flow path 8, a bent portion 4b is formed which terminates from the straight portion 4a in a substantially vertical upward direction.

  That is, the diffuser vane 4 is formed to have a straight portion 4a extending in a direction perpendicular to the axis C and a bent portion 4b extending in a straight line and extending substantially vertically upward. Yes. Now, let R be the bend radius of the upper surface of the bend 4b.

  On the other hand, the gas flow path 5 is formed in a swiveling direction with respect to the diffuser disk 3 and between the diffuser vanes 2 in FIG. 2, which is a plan view of a plane cross section orthogonal to the axis C of the compressor. The width w of the gas flow path 5 is configured to be widened for a while as it goes downstream.

  In the diffuser 2 configured in this way, the compressed gas accelerated by the impeller 1 flows along the narrow gas flow path 5 formed between the diffuser vanes 4 and is decelerated, and most of the dynamic pressure is static pressure. After recovering to the above, it is configured to be discharged to the outlet flow path portion 8. Usually, in such a diffuser 2, the disk 3 and the vane 4 are integrally formed by cutting or casting.

  Therefore, the diffuser 2 configured in this manner allows the gas accelerated by the impeller 1 to flow along the narrow gas flow path 5 formed between the diffuser vanes 4 without disturbing the flow through the straight portion 4a. Since most of the dynamic pressure is returned to the static pressure after being led to the bent portion 4b, it is discharged to the outlet flow passage portion 8, so that the compression efficiency of the compressor is not lowered.

  Furthermore, in FIG. 1 in which the upper surface of the bent portion 4b of the diffuser vane 4 is a plan view of the longitudinal section including the axial center C of the compressor, the bent radius R is more than twice the height h of the gas flow path 5. It is preferable to have. If the bending radius R of the bent portion 4 b is equal to the height h of the gas flow path 5, the pressure loss of the bent portion 4 b is 18.0 kPa, but the bending radius R of the bent portion 4 b is equal to that of the gas flow path 5. This is because the pressure loss is significantly reduced to 15.7 kPa when the height h is 2.5 times.

  Here, the gas flow path 5 will be described in more detail. The gas flow path 5 is composed of an upstream disk flow path portion 5a and a downstream cylindrical flow path portion 5b. That is, the disk flow path portion 5a is defined by a space between the diffuser disk 3 and the lower end surface 7a of the scroll 7 in the axial center C direction, and a space between the diffuser vanes 4 in the circumferential direction perpendicular to the axial center C. Is formed. The cylindrical flow path portion 5b is a diffuser in the circumferential direction perpendicular to the axis C, a space sandwiched between the inner wall surface 6a of the housing 6 and the lower end surface 7a of the scroll 7 in the radius R direction of the bent portion 4b. A space between the vanes 4 is formed.

  Therefore, since the disk flow path portion 5a and the cylindrical flow path portion 5b constituting the gas flow path 5 are formed by a combination of members of the compressor according to the conventional example excluding the diffuser 2, the manufacturing cost is significantly increased. And a complicated configuration can be avoided.

  With such a configuration of the gas flow path 5, the swirl flow S of the gas accelerated by the impeller 1 is guided to the bent portion 4 b along the straight portion 4 a of the gas flow path 5 without disturbing the flow, and the dynamic pressure After the most part is efficiently recovered to a static pressure, it can be discharged to the outlet channel portion 8. The outlet channel 8 is a part that collects the compressed gas that has come out of the diffuser 2 and flows it to a gas cooler or other piping outside the compressor system.

  The diffuser 2 of the compressor according to the present invention is preferably applied to the diffuser of the barrel compressor so as to form a smooth gas flow as shown in FIGS. In particular, in the case of a barrel type compressor having a small barrel portion used when there is a demand for making the compressor compact and inexpensive, a conventional diffuser having a long vane length cannot be applied. Any diffuser can be applied. That is, by applying the present invention to a diffuser of a compact barrel compressor, a particularly remarkable improvement in compression efficiency can be desired. However, the diffuser 2 of the compressor which concerns on this invention is not necessarily limited to a barrel type compressor, It can apply also to another centrifugal compressor.

<Example>
In the barrel compressor having the same capacity, the diffuser according to the embodiment of the present invention shown in FIGS. 1 and 2 is adopted (Example), and the diffuser according to the conventional example shown in FIGS. FIG. 3 shows a simulation result comparing the compression efficiencies in the case of (comparative example). In the embodiment, the bending radius R of the bent portion 4b of the diffuser vane 4 is R = 3h.

  According to the simulation result, as shown in FIG. 3, the compression efficiency increases as the ratio Q / N of the discharge flow rate Q of the compressor and the rotational speed N of the impeller increases, and at Q / N = 100%. Compression efficiency is maximized. Furthermore, the compression efficiency decreases rapidly as Q / N increases. Further, in all Q / Ns excluding the region where Q / N is 90% or less, the compression efficiency of the example is higher than that of the comparative example, and the difference is 1% which is the maximum when Q / N = 100%. became.

  That is, according to the diffuser of the compressor according to the present invention, the downstream side of the diffuser vane extends continuously along the shape of the gas flow path, and the longitudinal section including the axial center of the compressor is viewed in plan view. When the diffuser vane extended is terminated by forming a bent portion immediately before the compressed gas heads toward the outlet channel, a simple structure such as a barrel compressor can be used without increasing pressure loss. The compression efficiency of the compressor can be improved by about 0.5 to 1%.

  Moreover, according to the diffuser of the compressor which concerns on this invention, when the bending part of the said diffuser vane planarly views the longitudinal cross section containing the axial center of a compressor, it bends more than twice the height of the said gas flow path. Since it has a radius, it is possible to reduce the increase in pressure loss and improve the compression efficiency of the compressor.

It is a principal part longitudinal cross-sectional view for demonstrating the diffuser of the barrel type compressor which concerns on embodiment of this invention. FIG. 1A is a plan sectional view showing a part of the arrow AA in FIG. 1 omitted, and FIG. 2B is a longitudinal sectional view showing the arrow BB in FIG. In connection with examples of the present invention, the compression efficiency with respect to Q / N when the diffuser according to the embodiment of the present invention is employed (example) and when the diffuser according to the conventional example (comparative example) is employed. It is a figure which shows the result of simulation. It is a principal part longitudinal cross-sectional view for demonstrating the diffuser of the barrel type compressor which concerns on a prior art example. 4A is a plan sectional view showing a part of the arrow XX in FIG. 4 with a part omitted, and FIG. 5B is a longitudinal sectional view showing the arrow YY in FIG. It is sectional drawing which shows one Example of the diffuser which concerns on the prior art 1. FIG. It is the plane sectional view which abbreviate | omitted some description which shows one Embodiment of the structure of the vaneless part of the compressor which concerns on the prior art 2. FIG.

Explanation of symbols

C: Compressor axis, S: Swirl, R: Radius of the upper surface of the bend,
h: height of gas flow path, w: width of gas flow path,
1: Impeller, 2: Diffuser, 3: Diffuser disc,
4: Diffuser vane, 4a: straight portion, 4b: bent portion,
5: Gas channel, 5a: Disk channel, 5b: Cylindrical channel,
6: housing, 6a: inner wall surface,
7: Scroll, 7a: Lower end surface,
8: Outlet channel section

Claims (4)

  In a diffuser of a compressor in which a diffuser vane along a swirling flow of compressed gas is provided in a diffuser disk and a gas flow path is formed between these vanes, the outer shape of these diffuser vanes is on the downstream side of the diffuser vane. When the longitudinal section including the axial center of the compressor is viewed in plan, the diffuser vane that extends is bent immediately before the compressed gas goes to the outlet channel. A compressor diffuser characterized in that it has a section and is terminated.   The gas flow path is formed in a swiveling direction with respect to the diffuser disk when the plane cross section orthogonal to the axial center of the compressor is viewed in plan, and the gas flow path formed between the diffuser vanes is downstream. The diffuser for a compressor according to claim 1, wherein the diffuser is widened in the direction for a while.   The upper surface of the bent portion of the diffuser vane has a bending radius that is at least twice as high as the height of the gas flow path when a longitudinal section including the axial center of the compressor is viewed in plan view. The diffuser of the compressor as described in 1 or 2.   The gas flow path is formed by a space sandwiched between the upper surface of the diffuser disk and the lower end surface of the scroll in the axial direction of the compressor, and a space between the diffuser vanes in the circumferential direction perpendicular to the axial center. The upstream disk flow path portion, the radial direction in the bent portion, the space sandwiched between the inner wall surface of the compressor housing and the lower end surface of the scroll, and the circumferential direction orthogonal to the axis The diffuser for a compressor according to any one of claims 1 to 3, further comprising a downstream cylindrical flow path formed by a space between the diffuser vanes.

Images