JP2009197613A - Centrifugal compressor and diffuser vane unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently improve the compressor efficiency of a centrifugal compressor 1 by reducing a large energy loss area on sides of outlets of diffuser vanes 15 after the operating area of the centrifugal compressor 1 is sufficiently secured and an energy loss between the adjacent diffuser vanes 15 is reduced. <P>SOLUTION: A vaned diffuser 11 is provided with an annular diffuser plate 13 buried in the hub-side wall surface 13a of a casing 3, and a plurality of diffuser vanes 15 arranged at intervals in a peripheral direction within an annular diffuser channel DP formed of a shroud-side wall surface 13b wall of the casing 3 of the side of the hub, and the wall surface 3b thereof, and having base edges integrally connected to the diffuser plate 13. A fillet rounded portion 17 is formed at a periphery of each of the base edges of the diffuser vanes 15. The fillet rounded portion 17 of each of the diffuser vanes 15 is so formed that the radius of curvature R of a trailing edge 17p is larger than the radius of curvature R of a leading edge 17f. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor that compresses a gas such as air using centrifugal force, and a diffuser vane unit used in the centrifugal compressor.

  There are two types of diffusers in centrifugal compressors: vaned diffusers and vaneless diffusers. Centrifugal compressors used in marine turbochargers, gas turbines, etc., are designed to increase the compressor efficiency. Diffusers are often used as diffusers. The configuration of a conventional centrifugal compressor employing a vane diffuser will be described with reference to FIGS. 7 and 8A and 8B. Here, FIG. 7 is a sectional view of a conventional centrifugal compressor, FIG. 8 (a) is a view of the conventional diffuser vane as seen from the shroud side wall surface, and FIG. 8 (b) is a view of the conventional diffuser vane. It is a perspective view.

  As shown in FIG. 7, the conventional centrifugal compressor 101 includes a casing 103, and the casing 103 has a compression region CR for compressing air (an example of gas) inside. . Further, an inlet 105 through which air can be introduced to the compression region CR side is formed on the upstream side of the compression region CR of the casing 103.

  A hub 107 is provided in the compression region CR of the casing 103, and the hub 107 is rotatable about an axis (axis of the hub 107). Further, a plurality of impeller blades 109 are provided on the outer peripheral surface of the hub 107 at intervals in the circumferential direction, and the tips of the outer edge portions of the impeller blades 109 are close to the shroud side wall surface 103a of the casing 103, respectively. It is.

  As shown in FIGS. 7 and 8A and 8B, a vane diffuser 111 for converting the velocity energy of air into pressure energy is provided on the downstream side of the compression region CR of the casing 103. The vane diffuser 111 is disposed in an annular diffuser passage DP formed by an arc-shaped diffuser plate 113 embedded in the hub side wall surface 103b of the casing, and the shroud side wall surface 103a and the hub side wall surface 103b in the casing 103. A plurality of diffuser vanes 115 are provided which are disposed at intervals in the circumferential direction and whose base edge portions are integrally connected to the diffuser plate 113, respectively. Further, fillet ares 117 are formed on the periphery of the base edge portion of each diffuser vane 115, and the fillet ares 117 in each diffuser vane 115 have a radius of curvature extending from the leading edge side 117f to the trailing edge side 117p, respectively. The same.

  Therefore, for example, by rotating the hub 107 by rotating a turbine wheel (not shown) or the like and integrally rotating a plurality of impeller blades 109, the air introduced from the inlet 105 to the compression region CR side is subjected to centrifugal force. It can be compressed using. The compressed air is pressurized by the vane diffuser 111 and exhausted from the diffuser flow path DP.

In addition, there exist some which are shown to patent document 1 and patent document 2 as a prior art relevant to this invention.
Japanese Patent Laid-Open No. 10-77997 JP 2004-124715 A

  By the way, the compressed air is pressurized by the vane diffuser 111, and the air pressure on the outlet side of the diffuser vane 115 is higher than the air pressure on the inlet side of the diffuser vane 115. Further, in the vicinity of the boundary portion between the diffuser vane 115 and the diffuser plate 113, the influence of the inertia of the air flow is small and the secondary flow tends to increase. Therefore, a part of the air that has flowed to the outlet side of the diffuser vane 115 flows backward, and as shown in FIGS. 9A and 9B, a region with a large energy loss (pressure loss) on the outlet side of the diffuser vane 115 ( 9 (a) and 9 (b) is enlarged, and the compressor efficiency of the centrifugal compressor 101 is reduced. Here, FIG. 9A is a diagram showing a region where energy loss is large on the equal span surface of the conventional diffuser vane, and FIG. 9B is an exit side of the conventional diffuser vane and orthogonal to the air flow direction. It is a figure which shows the area | region where energy loss is large in the surface to perform, Comprising: The area | region where energy loss is large is calculated | required by CFD (Computational Fluid Dynamics) analysis.

  On the other hand, in order to solve the above-mentioned problem, an improvement measure of increasing the radius of curvature of the fillet are also conceivable. That is, by increasing the radius of curvature of the fillet are 117, the flow passage area on the outlet side of the diffuser vane 115 is reduced, and the pressure increase of the air by the vane diffuser 111 is suppressed, and the diffuser vane 115 and the diffuser plate 113 The influence of the inertia of the air flow in the vicinity of the boundary portion is increased to reduce the secondary flow.

  However, if the radius of curvature of the fillet 117 is increased to suppress the pressure increase of air by the vane diffuser 111 or reduce the secondary flow in the vicinity of the boundary portion between the diffuser vane 115 and the diffuser plate 113, Reduction of the flow path area on the inlet side of the diffuser vane 115 leads to a decrease in the choke flow rate of air and an increase in the Mach number (inlet Mach number) on the inlet side of the diffuser vane 115. For this reason, there arises a new problem that the operating range of the centrifugal compressor 101 is narrowed or the energy loss between the adjacent diffuser vanes 115 is increased, and the above-described improvement measures have not been put into practical use.

  Therefore, the present invention provides a novel configuration of centrifugal compression that can reduce a region of large energy loss on the outlet side of the diffuser vane while suppressing a decrease in the gas choke flow rate and an increase in the diffuser vane inlet Mach number. The purpose is to provide a machine and a diffuser vane unit.

  A first feature of the present invention is a centrifugal compressor that compresses gas using centrifugal force, and has a compression region for compressing gas inside, and the gas is compressed upstream of the compression region. A casing formed with an introduction port that can be introduced to the side, a hub provided in the compression region of the casing and rotatable about an axis, and provided on the outer peripheral surface of the hub at intervals in the circumferential direction. A plurality of impeller blades, a diffuser plate provided on a downstream side of the compression region of the casing and provided on a hub side wall surface or a shroud side wall surface of the casing, and a hub side wall surface and a shroud side wall surface of the casing. Are disposed in the annular diffuser flow path at intervals in the circumferential direction, and the base edge portion is integrally connected to the diffuser plate. Each of the diffuser vanes, and a vane diffuser in which a fillet are formed on the periphery of the base edge portion of each diffuser vane, and the fillet are in each diffuser vane has a downstream curvature, respectively. The gist is that the radius is larger than the upstream radius of curvature.

  In the claims and the description, the “upstream side” refers to the upstream side when viewed from the flow direction of the mainstream gas, and the “downstream side” refers to the flow direction of the mainstream gas. This is the downstream side.

  According to the first feature, by rotating the hub and integrally rotating the plurality of impeller blades, the gas introduced from the inlet to the compression region side is compressed using centrifugal force. Can do. The compressed gas is pressurized by the vane diffuser and exhausted from the diffuser flow path (general operation of the centrifugal compressor).

  In addition, since the fillet are in each diffuser vane has a curvature radius on the downstream side larger than the curvature radius on the upstream side, after sufficiently securing the flow path area on the inlet side of the diffuser vane, The flow area on the outlet side of the diffuser vane can be reduced, and the influence of the inertia of the gas flow in the vicinity of the boundary portion between the diffuser vane and the diffuser plate can be increased. Accordingly, while suppressing a decrease in the choke flow rate of the gas and an increase in the Mach number (inlet Mach number) on the inlet side of the diffuser vane, the pressure increase of the gas by the vane diffuser is suppressed, and the diffuser vane and the diffuser plate are suppressed. The secondary flow in the vicinity of the boundary portion of the diffuser vane can be reduced, and the region where the energy loss is large on the outlet side of the diffuser vane can be reduced (the characteristic action of the centrifugal compressor).

  A second feature of the present invention is that a diffuser vane unit used in a centrifugal compressor that compresses gas using centrifugal force can be disposed on a hub side wall surface or a shroud side wall surface of a casing in the centrifugal compressor. Each of the diffuser vanes, and a plurality of diffuser vanes each having a base edge portion integrally connected to the diffuser plate and having a fillet are formed on the periphery of the base edge portion. The above-mentioned fillet are each characterized in that the curvature radius on the rear edge side is larger than the curvature radius on the front edge side.

  According to the second feature, the fillet radius in each diffuser vane has a radius of curvature on the trailing edge side larger than that on the front edge side, so the diffuser vane unit is used in the centrifugal compressor. Has the same effect as the unique action of the centrifugal compressor.

  According to the present invention, it is possible to reduce a region with a large energy loss on the outlet side of the diffuser vane while suppressing a decrease in the choke flow rate of the gas and an increase in the inlet Mach number of the diffuser vane. The diffuser while suppressing a part of the gas flowing to the outlet side of the diffuser vane from flowing backward while ensuring a sufficient operating range of the machine and reducing energy loss between the adjacent diffuser vanes. It is possible to sufficiently improve the compressor efficiency of the centrifugal compressor by reducing a region where energy loss is large on the outlet side of the vane.

  An embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is a cross-sectional view of a centrifugal compressor according to an embodiment of the present invention, FIG. 2A is a view of a diffuser vane according to an embodiment of the present invention as viewed from a shroud side wall surface of the casing, and FIG. FIG. 3B is a perspective view of the diffuser vane according to the embodiment of the present invention, FIG. 3A is an enlarged cross-sectional view taken along line IIIA-IIIA in FIG. 2A, and FIG. 2 (a) is an enlarged cross-sectional view taken along line IIIB-IIIB, FIG. 3 (c) is an enlarged cross-sectional view taken along line IIIC-IIIC in FIG. 2 (a), and FIGS. 4 (a) and 4 (b) are The figure which shows the blade cross-sectional shape of the upstream edge part of the diffuser vane which concerns on embodiment of this invention, Fig.5 (a) shows the area | region where energy loss is large in the equal span surface of the diffuser vane which concerns on embodiment of this invention. FIG. 5 and FIG. 5 (b) are views at the outlet side of the diffuser vane according to the embodiment of the present invention. One shows a large area of the energy loss in the plane perpendicular to the air flow direction, FIG. 6 is a cross-sectional view of a centrifugal compressor according to a modification of the embodiment of the present invention.

  As shown in FIG. 1, a centrifugal compressor 1 according to an embodiment of the present invention is used for a ship supercharger, a gas turbine, and the like, and compresses air (an example of gas) using centrifugal force. . And the specific structure of the centrifugal compressor 1 which concerns on embodiment of this invention is as follows.

  The centrifugal compressor 1 includes a casing 3, and the casing 3 has a compression region CR for compressing air (an example of gas) inside. Further, an inlet 5 through which air can be introduced to the compression region CR side is formed on the upstream side of the compression region CR of the casing 3. The casing 3 is integrally attached to another casing (not shown).

  A hub 7 is provided in the compression region CR of the casing 3, and the outer peripheral surface of the hub 7 is directed from the axial direction (axial direction of the hub 7) to the outer side in the radial direction (radial direction of the hub 7). It extends. The hub 7 is integrally connected to one end of a turbine shaft TS that is rotatably provided in another casing, and has a shaft center (the axis of the hub 7, in other words, the shaft of the turbine shaft TS. It can be rotated around the center. A turbine wheel (not shown) is integrally connected to the other end of the turbine shaft TS.

  A plurality of impeller blades 9 are provided on the outer peripheral surface of the hub 7 at intervals in the circumferential direction, and each impeller blade 9 extends from the axial center direction of the hub 7 toward the radially outer side of the hub 7. ing. The tip of the outer edge of each impeller blade 9 is close to the shroud side wall surface 3 a of the casing 3.

  As shown in FIGS. 1 and 2A and 2B, a vane diffuser 11 that converts velocity energy of air into pressure energy is provided on the downstream side of the compression region CR of the casing 3. The vane diffuser 11 is an annular diffuser formed by an annular (substantially annular) diffuser plate 13 embedded in the hub side wall surface 3b of the casing 3, and a shroud side wall surface 3a and the hub side wall surface 3b in the casing 3. A plurality of diffuser vanes 15 are provided in the flow path DP at intervals in the circumferential direction and their base edges are integrally connected to the diffuser plate 13. Here, the annular diffuser plate 13 and the plurality of diffuser vanes 15 constitute a diffuser vane unit used in the centrifugal compressor 1. Further, one side surface of the diffuser plate 13 (the surface to which the base end portion of the diffuser vane 15 is connected) is substantially flat.

  Instead of the annular diffuser plate, a diffuser plate that can be divided into a plurality of arc-shaped diffuser plates is used, and the plurality of arc-shaped diffuser plates are arranged in the circumferential direction so that the plurality of diffuser plates are annular. You may make it present. Further, as shown in FIG. 6, the diffuser plate 13 may be embedded in the shroud side wall surface 3 a of the casing 3 instead of being embedded in the hub side wall surface 3 b of the casing 3.

  As shown in FIGS. 1, 2 (a), (b), and FIGS. 3 (a), (b), and (c), fillet ares 17 are formed on the periphery of the base edge of each diffuser vane 15. Yes. The fillet radius 17 in each diffuser vane 15 has a radius of curvature (fillet radius) R on the downstream side (in other words, the trailing edge side) 17p from a curvature radius R of the upstream side (in other words, the leading edge side) 17f. Is also getting bigger.

  Each of the fillet ares 17 in each diffuser vane 15 has a curvature radius R that gradually increases (in a stepless manner) from the upstream side 17f to the downstream side 17p by, for example, casting. The size may be increased stepwise from the upstream side 17f to the downstream side 17p by cutting using a plurality of different cutting tools (for example, a plurality of cutting tools having different blade diameters).

  The blade cross-sectional shape (transverse cross-sectional shape along the arrow IV-IV line in FIG. 1) of the upstream edge portion (front edge portion) of each diffuser vane 15 is a semicircular shape (FIG. 4 (a)). )) And a curved shape in which the radius of curvature gradually decreases toward the tip side (see FIG. 4B). In the embodiment of the present invention, the curve shape specifically refers to the direction along the cord direction as the major axis direction Le and the direction orthogonal to the major axis direction Le as the minor axis direction Ls. However, it may be a parabolic shape in which the radius of curvature gradually decreases toward the tip side.

  A scroll channel (not shown) is formed at the peripheral edge of the diffuser channel DP, and this scroll channel is connected to an intake manifold (not shown) of the internal combustion engine.

  Then, the effect | action and effect of embodiment of this invention are demonstrated.

  By rotating the hub 7 by rotating the turbine wheel and integrally rotating the plurality of impeller blades 9, the air introduced from the inlet 5 to the compression region CR side is compressed using centrifugal force. The compressed air is pressurized by the vane diffuser 11 and exhausted from the diffuser flow path DP. In addition, the air exhausted from the diffuser flow path DP is sent to the intake manifold of the internal combustion engine via the scroll flow path (general operation of the centrifugal compressor 1).

  Further, the fillet radius 17 in each diffuser vane 15 has a curvature radius R on the downstream side 17p larger than a curvature radius R on the upstream side 17f, so that the flow path area on the inlet side of the diffuser vane 15 is sufficiently large. In addition, the flow area on the outlet side of the diffuser vane 15 can be reduced, and the influence of the inertia of the airflow in the vicinity of the boundary portion between the diffuser vane 15 and the diffuser plate 13 can be increased. Thus, while suppressing the decrease in the air choke flow rate and the increase in the Mach number (inlet Mach number) on the inlet side of the diffuser vane 15, the pressure increase of the air by the vane diffuser 11 is suppressed, and the diffuser vane 15 and the diffuser plate 13 are suppressed. As shown in FIGS. 6 (a) and 6 (b), the secondary flow in the vicinity of the boundary portion between and the diffuser vane 15 is reduced in the region where the energy loss is large (in FIGS. 6 (a) and 6 (b)). It is possible to reduce the area to which the point hatch is applied. In addition, the area | region where an energy loss is large is calculated | required by CFD analysis. (Function (1) peculiar to the centrifugal compressor 1).

  Further, when the blade cross-sectional shape of the upstream edge portion of each diffuser vane 15 is a curved shape (semi-elliptical shape or parabolic shape), the air flow having a high inlet Mach number is the upstream edge of the diffuser vane 15. Even if it collides with the part, the flow along the blade surface of the diffuser vane 15 can be sufficiently secured, and the development of the boundary layer on the blade surface of the diffuser vane 15 can be sufficiently suppressed (the characteristic of the centrifugal compressor 1). Action (2)).

  Therefore, according to the embodiment of the present invention, it is possible to reduce the region where the energy loss is large on the outlet side of the diffuser vane 15 while suppressing the decrease in the choke flow rate of the air and the increase in the inlet Mach number of the diffuser vane 15. Therefore, it is possible to secure a sufficient operating range of the centrifugal compressor 1 and reduce energy loss between adjacent diffuser vanes 15 and to prevent a part of the air flowing to the outlet side of the diffuser vanes 15 from flowing backward. However, it is possible to reduce the region where the energy loss is large on the outlet side of the diffuser vane 15 and sufficiently improve the compressor efficiency of the centrifugal compressor 1.

  Further, in the case where the blade cross-sectional shape of the upstream edge of each diffuser vane 15 is a curved shape, even if an air flow having a high inlet Mach number collides with the upstream edge of the diffuser vane 15, the diffuser Since the flow along the blade surface of the vane 15 can be sufficiently secured and the development of the boundary layer on the blade surface of the diffuser vane 15 can be sufficiently suppressed, the adjacent diffuser can be set with a high pressure ratio of the centrifugal compressor 1. The pressure loss between the vanes 15 can be reduced, and the compressor efficiency of the centrifugal compressor 1 can be further improved.

  The present invention is not limited to the description of the above-described embodiment, and can be implemented in various other aspects. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

It is sectional drawing of the centrifugal compressor which concerns on embodiment of this invention. 2A is a view of the diffuser vane according to the embodiment of the present invention as seen from the shroud side wall surface of the casing, and FIG. 2B is a perspective view of the diffuser vane according to the embodiment of the present invention. 3A is an enlarged cross-sectional view taken along line IIA-IIA in FIG. 2A, FIG. 3B is an enlarged cross-sectional view taken along line IIB-IIB in FIG. (C) is an expanded sectional view along the IIC-IIC line in Fig.2 (a). 4A and 4B are views showing the blade cross-sectional shape of the upstream edge portion of the diffuser vane according to the embodiment of the present invention. FIG. 5A is a diagram showing a region with a large energy loss on the equal span surface of the diffuser vane according to the embodiment of the present invention, and FIG. 5B is a diagram showing an outlet side of the diffuser vane according to the embodiment of the present invention. And it is a figure which shows the area | region where the energy loss is large in the surface orthogonal to the flow direction of air. It is sectional drawing of the centrifugal compressor which concerns on the modification to embodiment of this invention. It is sectional drawing of the conventional centrifugal compressor. FIG. 8A is a view of a conventional diffuser vane as viewed from the shroud side wall surface of the casing, and FIG. 8B is a perspective view of the conventional diffuser vane. FIG. 9A is a diagram showing a region where energy loss is large on the equi-span surface of the diffuser vane, and FIG. 9B is a diagram showing large energy loss on the surface on the outlet side of the diffuser vane and perpendicular to the air flow direction. It is a figure which shows an area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Casing 3a Shroud side wall surface 3b Hub side wall surface 5 Inlet 7 Hub 9 Impeller blade 11 Vane diffuser 13 Diffuser plate 15 Diffuser vane 17 Fillet are 17f Front edge side 17p Rear edge side CR Compression area DP Diffuser flow path Le Length Axial direction Ls Short axis direction TS Turbine shaft

Claims (4)

In a centrifugal compressor that compresses gas using centrifugal force,
A casing having a compression region for compressing gas inside, and having an inlet formed on the upstream side of the compression region capable of introducing gas to the compression region side;
A hub provided in the compression region of the casing and rotatable about an axis;
A plurality of impeller blades provided on the outer peripheral surface of the hub at intervals in the circumferential direction;
A diffuser plate provided on the downstream side of the compression region of the casing and provided on a hub side wall surface or a shroud side wall surface of the casing, and an annular diffuser channel formed by the hub side wall surface and the shroud side wall surface of the casing A plurality of diffuser vanes disposed at intervals in the circumferential direction and having base edges integrally connected to the diffuser plate, respectively, and a fillet radius is provided around the base edge of each diffuser vane. Each having a vane diffuser formed thereon,
The fillet are in each diffuser vane is characterized in that the downstream radius of curvature is larger than the upstream radius of curvature.   The centrifugal compressor according to claim 1, wherein the blade cross-sectional shape of the upstream edge portion of each diffuser vane has a curved shape such that the radius of curvature gradually decreases toward the tip side. In a diffuser vane unit used in a centrifugal compressor that compresses gas using centrifugal force,
A diffuser plate that can be disposed on a hub side wall surface or a shroud side wall surface of a casing in the centrifugal compressor;
A plurality of diffuser vanes each having a base edge portion integrally connected to the diffuser plate and having a fillet are formed on the periphery of the base edge portion;
The diffuser vane unit is characterized in that the fillet radius in each diffuser vane has a radius of curvature on the trailing edge side larger than that on the front edge side.   The diffuser vane unit is characterized in that the blade cross-sectional shape of the front edge portion of each diffuser vane has a curved shape such that the radius of curvature gradually decreases toward the tip side.

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