JP2009197614A - Centrifugal compressor and diffuser vane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently improve the compressor efficiency of a centrifugal compressor 1 after the high pressure ratio of the centrifugal compressor 1 is set. <P>SOLUTION: A vaned diffuser 11 is provided with a plurality of diffuser vanes 13 arranged at intervals in a peripheral direction within an annular diffuser channel DP formed the shroud-side wall surface 3a of the casing 3, and the hub-side wall surface 3b thereof. The vane cross-sectional shape of the upstream edge of each of the diffuser vanes 13 is formed into a curved shape with the radius of curvature gradually reduced toward a tip side (for example, a semi-elliptical shape or a parabolic shape). <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 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. And the structure of the conventional centrifugal compressor which employ | adopted the vane diffuser is as follows.

  That is, the conventional centrifugal compressor is provided with a casing, and this casing has a compression region for compressing air (an example of gas) for compressing air inside. Further, an inlet port through which air can be introduced to the compression region side is formed on the upstream side of the compression region of the casing.

  A hub is provided in the compression region of the casing, and the hub can rotate about an axis (axis of the hub). A plurality of impeller blades are provided on the outer peripheral surface of the hub at intervals in the circumferential direction, and the tips of the outer edge portions of the impeller blades are close to the shroud side wall surface of the casing.

  A vane diffuser that converts air velocity energy into pressure energy is provided downstream of the compression region of the casing. The vane diffuser includes a plurality of diffuser vanes disposed at intervals in the circumferential direction in an annular diffuser passage formed by a shroud side wall surface and a hub side wall surface in the casing. In addition, the blade cross-sectional shape (transverse cross-sectional shape) of the upstream edge portion (front edge portion) of each diffuser vane has a semicircular shape.

  Therefore, for example, by rotating a hub by rotating a turbine wheel (not shown) or the like and integrally rotating a plurality of impeller blades, the air introduced from the inlet to the compression region side is compressed using centrifugal force. To do. The compressed air is pressurized by the vane diffuser and exhausted from the diffuser flow path.

In addition, there exist some which are shown to patent document 1 and patent document 2 as a prior art relevant to this invention.
JP 2005-226568 A JP 2004-124715 A

  By the way, in recent years, as the pressure ratio of the centrifugal compressor is increased, as shown in FIG. 5, the Mach number (inlet Mach number) of the air flow (an example of the gas flow) on the inlet side of the diffuser vane tends to increase. . Here, FIG. 5 is a diagram showing a region with a high Mach number around the diffuser vane, and a region with a high Mach number (a region with a point hatch in FIG. 5) is obtained by CFD (Computational Fluid Dynamics) analysis. Looking for. Also, when an air flow with a high inlet Mach number collides with the upstream edge (front edge) of the diffuser vane, the flow along the wing surface of the diffuser vane decreases, and the boundary layer on the wing surface of the diffuser vane becomes downstream. Develop towards. Therefore, the pressure loss between adjacent diffuser vanes becomes large, and the compressor efficiency of the centrifugal compressor is reduced.

  That is, there is a problem that it is difficult to sufficiently improve the compressor efficiency of the centrifugal compressor while setting the pressure ratio of the centrifugal compressor high.

  Then, this invention aims at providing the centrifugal compressor and diffuser vane of a novel structure which can solve the above-mentioned problem.

  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 and a downstream side of the compression region of the casing, and arranged in an annular diffuser flow path formed by a shroud side wall surface and a hub side wall surface in the casing at intervals in the circumferential direction. A vane diffuser including a plurality of diffuser vanes, and a blade cross-sectional shape (transverse cross-sectional shape) of an upstream edge portion (front edge portion) of each diffuser vane, And summarized in that the radius of curvature is curved shape smaller gradually toward the distal end side.

  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. The compressed gas is pressurized by the vane diffuser and exhausted from the diffuser flow path (general operation of the centrifugal compressor).

  Further, the blade cross-sectional shape of the upstream edge portion of each diffuser vane is a curved shape in which the radius of curvature gradually decreases toward the tip side, so that a gas flow having a high inlet Mach number is generated in the diffuser vane. Even if it collides with the upstream edge, it is possible to sufficiently secure the flow along the blade surface of the diffuser vane and sufficiently suppress the development of the boundary layer on the blade surface of the diffuser vane (the centrifugal compressor). Specific action).

  A second feature of the present invention is that, in a diffuser vane used in a centrifugal compressor that compresses gas using centrifugal force, the blade cross-sectional shape (transverse cross-sectional shape) of the leading edge portion has a radius of curvature toward the tip side. The main point is that the curve shape gradually decreases.

  According to the second feature, the blade cross-sectional shape of the leading edge portion of the diffuser vane is a curved shape in which the radius of curvature gradually decreases toward the tip side, so that the diffuser vane is used for the centrifugal compressor. If there is, the same action as the characteristic action of the centrifugal compressor is exhibited.

  According to the present invention, even when a gas flow having a high inlet Mach number collides with the upstream edge portion of the diffuser vane, a sufficient flow along the blade surface of the diffuser vane is ensured, and the blade surface of the diffuser vane is secured. In order to sufficiently suppress the development of the boundary layer, the pressure ratio of the centrifugal compressor is set high, and the pressure loss between the adjacent diffuser vanes is reduced to sufficiently improve the compressor efficiency of the centrifugal compressor. Can be improved.

  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. 2 is a view showing a blade cross-sectional shape of an upstream edge portion of a diffuser vane according to an embodiment of the present invention, and FIG. FIG. 3A is a diagram illustrating a boundary layer generation state on the blade surface near the upstream edge of the diffuser vane according to the embodiment of the present invention, and FIG. 3B is an upstream edge of the diffuser vane according to the comparative example. FIG. 4 is a diagram showing the relationship between the air flow rate and the pressure loss for the example and the comparative example.

  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 a turbine 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 a turbine casing, and has a shaft center (the center of the hub 7, in other words, the turbine shaft TS. It can be rotated around the axis). 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 the outer edge portion of each impeller blade 9 is directed from the axial center direction of the hub 7 to the radially outer side of the hub 7. Each extending. 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. Further, the vane diffuser 11 includes a plurality of diffuser vanes 13 disposed in the annular diffuser flow path DP formed by the shroud side wall surface 3a and the hub side wall surface 3b in the casing 3 at intervals in the circumferential direction. ing. 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.

  The blade cross-sectional shape (transverse cross-sectional shape along the line II-II in FIG. 1) of the upstream edge portion (front edge portion) of each diffuser vane 13 has a radius of curvature gradually toward the tip side. The curve shape is small. Specifically, the curved shape is a semi-elliptical shape in which the direction along the cord direction is defined as the major axis direction Le and the direction orthogonal to the major axis direction Le is defined as the minor axis direction Ls. A relationship of 1 <(Re / Rs) ≦ 5, preferably 1 <(Re / Rs) <3 is established between the semi-elliptical major axis Re and minor axis Rs. Here, 1 <(Re / Rs) is set because, when Re / Rs is less than 1, the radius of curvature of the curved shape does not gradually decrease toward the tip side, while (Re / Rs ) ≦ 5 because, even if Re / Rs exceeds 5, there is no significant change in the specific action of the centrifugal compressor 1 described later, and the arrangement space of the upstream edge of the diffuser vane 13 This is because it is easy to ensure the above and the degree of freedom in design is increased.

  Instead of making the blade cross-sectional shape of the upstream edge of each diffuser vane 13 a semi-elliptical shape, a parabolic shape in which the radius of curvature gradually decreases toward the tip side may be used.

  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. Note that 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 blade cross-sectional shape of the upstream edge portion of each diffuser vane 13 is a curved shape (semi-elliptical shape or parabolic shape) in which the radius of curvature gradually decreases toward the tip side. Even if a high air flow collides with the upstream edge of the diffuser vane 13, a sufficient flow along the blade surface of the diffuser vane 13 is ensured, as shown in FIGS. 3A and 3B. It is possible to sufficiently suppress the development of the boundary layer B on the thirteen blade surfaces (specific action of the centrifugal compressor 1). In addition, the blade | wing cross-sectional shape of the upstream edge part of the diffuser vane (comparative diffuser vane) which concerns on the comparative example in FIG.3 (b) is a semicircle shape, The boundary shown by FIG.3 (a) (b) The generation state of the layer is obtained by CFD analysis.

  Therefore, according to the embodiment of the present invention, even when an air flow having a high inlet Mach number collides with the upstream edge portion of the diffuser vane 13, a sufficient flow along the blade surface of the diffuser vane 13 is ensured. Since the development of the boundary layer B on the blade surface of the vane 13 can be sufficiently suppressed, the pressure loss between the adjacent diffuser vanes 13 is reduced as shown in FIG. 4 after setting the pressure ratio of the centrifugal compressor 1 high. Thus, the compressor efficiency of the centrifugal compressor 1 can be sufficiently improved. The embodiment in FIG. 4 is obtained by calculating the pressure loss between adjacent diffuser vanes 13 by CFD analysis, and the comparative example in FIG. 4 is the pressure loss between adjacent comparative diffuser vanes. It is obtained by CFD analysis.

  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. It is a figure which shows the blade | wing cross-sectional shape of the upstream edge part of the diffuser vane which concerns on embodiment of this invention. FIG. 3A is a view showing a boundary layer generated on the blade surface near the upstream edge of the diffuser vane according to the embodiment of the present invention, and FIG. 3B is an upstream view of the diffuser vane according to the comparative example. It is a figure which shows the production | generation state of the boundary layer in the blade surface near a side edge part. It is a figure which shows the relationship between the flow volume of air and a pressure loss about an Example and a comparative example. It is a figure which shows the area | region with a high Mach number in the periphery of a diffuser vane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Casing 3a Shroud side wall surface 3b Hub side wall surface 5 Inlet port 7 Hub 9 Impeller blade 11 Vane diffuser 13 Diffuser vane CR Compression area DP Diffuser flow path Le Long axis direction Ls Short axis direction TS Turbine axis B Boundary layer

Claims (6)

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 plurality of diffuser vanes provided on the downstream side of the compression region of the casing and disposed in an annular diffuser passage formed by a shroud side wall surface and a hub side wall surface in the casing at intervals in the circumferential direction. A vaned diffuser with
A centrifugal compressor characterized in that 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.   The curved shape is a semi-elliptical shape in which a direction along a cord direction is defined as a major axis direction and a direction orthogonal to the major axis direction is defined as a minor axis direction. Centrifugal compressor.   The centrifugal compressor according to claim 1, wherein the curved shape is a parabolic shape. In diffuser vanes used in centrifugal compressors that compress gas using centrifugal force,
The diffuser vane is characterized in that the blade cross-sectional shape of the leading edge portion is a curved shape whose radius of curvature gradually decreases toward the tip side.   5. The curved shape is a semi-elliptical shape in which a direction along a cord direction is defined as a major axis direction and a direction orthogonal to the major axis direction is defined as a minor axis direction. Diffuser vanes.   The diffuser vane according to claim 4, wherein the curved shape is a parabolic shape.

Images