JP5167403B1 - Centrifugal fluid machine - Google Patents

Abstract

Provided is a centrifugal fluid machine configured so that the separation of flow due to the difference between the angle of a discharge flow from an impeller and the angle of a vane entrance is prevented to improve the performance of a diffuser provided with vanes. A centrifugal fluid machine is provided with blades, an impeller which has the blades, and a diffuser (21) which is provided downstream of the impeller and which has vanes (24) provided between a shroud-side wall surface (22) and a hub-side wall surface (23), the shroud-side wall surface (22) and the hub-side wall surface (23) facing each other. The centrifugal fluid machine is configured so that fluid, the pressure of which has been increased by rotating the impeller, passes through and flows out of the diffuser (21). The centrifugal fluid machine is provided with one or more working fluid ejection openings (25) which are open at the hub-side wall surface (23) and which eject a working fluid in the flow direction of the fluid along the pressure surfaces (24a) of the vanes (24). The working fluid ejection openings (25) are provided at radial positions closer to the front edges of the vanes (24) than positions located at a throat radius (R2).

Description

  The present invention relates to a centrifugal fluid machine including a winged diffuser, and more particularly to a centrifugal fluid machine such as a centrifugal compressor used in a marine supercharger, an automobile supercharger, an aircraft gas turbine, and the like.

  A centrifugal fluid machine used for a centrifugal compressor such as a supercharger rotates an impeller in a casing so that a fluid (gas) to be pressurized flows in a radial direction through most flow paths in the impeller. The pressure is increased mainly by the action of centrifugal force. Since such a centrifugal fluid machine is required to have a high pressure ratio, high efficiency, and a wide operating range, a winged diffuser having a plurality of vanes (diffuser blades) is provided downstream of the impeller. High performance winged diffusers are essential.

In the centrifugal compressor of Patent Document 1, in order to prevent the air flow from being separated from the vane, a communication path is formed that allows the negative pressure surface and the pressure surface of the vane to communicate with each other.
Further, the centrifugal fluid machine of Patent Document 2 includes a groove provided on at least one wall surface of the shroud side wall surface and the side wall surface of the hub, or a communication hole provided at the end of the vane adjacent to the wall surface, A configuration is disclosed in which the radially outer surface and the radially inner surface of the vane are in communication with each other. According to such a configuration, since the thickness of the boundary layer formed on the radially inner side surface of the vane is reduced, the stall limit of the diffuser can be extended to the low flow rate side, and stable operation in a wide flow range can be achieved. It becomes possible.

JP-A-10-331794 JP 2005-155565 A

By the way, the pressurized fluid discharged from the impeller flows into the vane of the centrifugal fluid machine as a distorted flow. For this reason, in order to improve the performance of the vane, it is necessary to improve in consideration of the impeller flow.
The distorted flow will be described in detail. The flow of the pressurized fluid flows into the vane of the diffuser with a velocity distribution in the blade height direction. For this reason, inconsistency of a flow angle and a blade inlet angle will arise in a vane entrance. Such angle mismatch causes separation in the fluid flow that is pressurized at the leading edge of the vane, and this separation causes problems to be improved such as a decrease in efficiency of the vaned diffuser and vane stall. is there.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to suppress the separation of the flow due to the angle mismatch between the impeller discharge flow and the vane inlet and improve the performance of the winged diffuser. It is to provide a centrifugal fluid machine.

In order to solve the above problems, the present invention employs the following means.
A centrifugal fluid machine according to a first aspect of the present invention includes a plurality of blades, an impeller having the plurality of blades, a shroud side wall surface and a hub side wall surface which are provided on the downstream side of the impeller and which are opposed to each other. A centrifugal fluid machine comprising a diffuser having a plurality of vanes in between, and configured to rotate the impeller and pressurize the fluid to flow out through the diffuser. One or a plurality of working fluid ejection ports that open and inject the working fluid along the pressure surface of the vane in the fluid flow direction, and the working fluid ejection port is located in front of the vane from the throat radius (R2). It is provided at a radial position on the edge side.

According to such a centrifugal fluid machine, the working fluid is provided with one or a plurality of working fluid ejection ports that are opened in the side wall surface of the hub and inject the working fluid in the fluid flow direction along the pressure surface of the vane. Since the injection port is provided at a radial position on the leading edge side of the vane with respect to the throat radius (R2), the working fluid injected to the pressure surface hub side of the vane merges with the distorted flow discharged from the impeller. Detachment caused by angle mismatch between the corner and the blade entrance angle is suppressed.
That is, the flow to be separated from the pressure surface of the vane leading edge is not easily separated from the pressure surface because it is affected by the working fluid ejected from the working fluid ejection port along the pressure surface in the fluid flow direction. . In this case, in order to suppress the separation on the pressure surface side, it is desirable to open the working fluid injection port in a region on the pressure surface side that is 20% or less of the throat width to inject the working fluid.

  A centrifugal fluid machine according to a second aspect of the present invention includes a plurality of blades, an impeller having the plurality of blades, a shroud side wall surface and a hub side wall surface which are provided on the downstream side of the impeller and which are opposed to each other. A centrifugal fluid machine comprising a diffuser having a plurality of vanes in between and configured to rotate the impeller and pressurize the fluid to flow out through the diffuser, on the shroud side wall surface One or a plurality of working fluid ejection ports that open and inject the working fluid along the suction surface of the vane in the flow direction of the fluid, and the working fluid ejection port is located in front of the vane from the throat radius (R2). It is provided at a radial position on the edge side.

According to such a centrifugal fluid machine, the working fluid is provided with one or a plurality of working fluid ejection ports that open in the shroud side wall surface and inject the working fluid in the fluid flow direction along the suction surface of the vane. Since the injection port is provided at a radial position on the leading edge side of the vane with respect to the throat radius (R2), the working fluid injected to the suction surface shroud side of the vane merges with the distorted flow discharged from the impeller. Detachment caused by angle mismatch between the corner and the blade entrance angle is suppressed.
That is, the flow to be separated from the suction surface of the leading edge of the vane is affected by the working fluid ejected from the working fluid ejection port along the suction surface in the fluid flow direction, and thus is less likely to be separated from the suction surface. . In this case, in order to suppress separation on the suction surface side, it is desirable to open the working fluid injection port in a region on the suction surface side that is 20% or less of the throat width to eject the working fluid.

  In the centrifugal fluid machine according to the present invention, the radial position at which the working fluid injection port is provided has a minimum radius (Ro) of 95% based on the leading edge radius (R1) of the vane as an inner peripheral limit, and the throat radius. It is preferable to set (R2) to the outer peripheral side limit, so that the working fluid is injected into a region in the vicinity of the leading edge of the vane, and the flow generated due to the angle mismatch between the impeller discharge flow and the vane inlet Separation can be efficiently suppressed with a minimum working fluid injection amount.

  In the above invention, the working fluid ejection angle (θ) of the working fluid ejection port is preferably set to be 60 degrees or less from the wall surface with respect to the fluid flow direction. The working fluid can efficiently flow from the leading edge of the vane along the pressure surface hub side or the suction surface shroud side, and the efficiency of suppression of separation by the injected working fluid is improved.

  In the above invention, it is preferable that the working fluid is a fluid that is partially recirculated from the downstream of the diffuser or a fluid that is introduced from an external pressure source.

According to the present invention described above, a remarkable effect can be obtained in that a centrifugal fluid machine is provided in which the separation of the flow due to the angle mismatch between the impeller discharge flow and the vane inlet is suppressed and the performance of the winged diffuser is improved.
In particular, the working fluid sprayed to the vane's pressure surface hub side is effective in improving performance, and the working fluid sprayed to the vane's suction surface shroud side is effective in expanding the operating range. By injecting the working fluid to both the shroud side, it is possible to realize a centrifugal fluid machine with a high pressure ratio and high efficiency and a wide working range.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the centrifugal fluid machine which concerns on this invention, (a) is a perspective view which shows the principal part structural example of a diffuser with a wing | blade, (b) looks at the diffuser with a wing | blade of (a) from the shroud side. (C) is AA sectional drawing of (b). It is a longitudinal cross-sectional view of the impeller and winged diffuser which show the outline | summary of a centrifugal fluid machine. It is the figure which looked at the centrifugal fluid machine of FIG. 2 from the impeller upstream.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of a centrifugal fluid machine according to the present invention (hereinafter described by exemplifying a centrifugal compressor) will be described with reference to the drawings.
As shown in FIGS. 2 and 3, the centrifugal compressor 10 is configured with an impeller 11 and a diffuser 21 as main elements, and pressurizes and discharges the introduced fluid. The impeller 11 includes a plurality of blades 12 and a hub 13 disposed at the root portion R of the blades 12, and the blades 12 each have a leading edge LE located at a small-diameter side end portion 13 a of the hub 13. At the same time, it is provided on the surface of the hub 13 such that the rear edge TE is located at the large-diameter side end 13b of the hub 13.
In addition, the code | symbol 14 has shown the shroud arrange | positioned so that the front end side of the braid | blade 12 may be covered.

The diffuser 21 is provided on the downstream side of the impeller 11 described above, and has a plurality of vanes (diffuser blades) 24 between the opposed shroud side wall surface 22 and the hub side wall surface 23, and passes through the impeller 11. Thus, the kinetic energy of the pressurized fluid (gas) is converted into pressure energy. That is, in the diffuser 21, the flow dynamic pressure is converted into an increase in static pressure by reducing the flow velocity of the fluid.
The flow with increased static pressure is guided to the outlet of the centrifugal compressor 10 by the spiral volute 31.

  That is, the centrifugal compressor 10 is provided with a plurality of blades 12 and an impeller 11 having a hub 13 disposed at a root portion R of the plurality of blades 12, and a shroud that is opposed to the impeller 11. A diffuser 21 having a plurality of vanes 24 is provided between the side wall surface 22 and the hub side wall surface 23, and is configured so that fluid whose pressure is increased by rotating the impeller 11 flows out through the diffuser 21.

FIG. 1 is an enlarged perspective view of a part of the diffuser 21, as viewed from the trailing edge TE side of the blade 12 that is the outlet side of the fluid that has passed through the impeller 11, that is, from the inlet side of the diffuser 21. .
With respect to the fluid compressor 10 described above, in the first aspect of the present embodiment shown in FIG. 1, the working fluid (arrow Fa in the figure) opens along the pressure surface 24 a of the vane 24 while opening in the hub side wall surface 23. One or a plurality of working fluid ejection ports 25 for ejecting in the flow direction are provided. The working fluid ejection port 25 is provided at a radial position that is closer to the front edge 24c of the vane 24 than the throat radius (R2).

  The working fluid ejection port 25 described above has a vane from a radius R1 corresponding to the front edge 24c of the vane 24, that is, a 95% radial position Ro (95% R1) based on a radius R1 of a circle connecting the positions of the front edge 24c. One or a plurality of holes are provided along the pressure surface 24a in a range up to a radial position R2 where the 24 throats 27 and the blade suction surface 24b intersect. In other words, the radial position (region in the radial direction) where the working fluid ejection port 25 is provided has a minimum radius Ro of 95% determined on the basis of the leading edge radius R1 of the vane 24 as an inner limit, and a throat radius. It is within the range with R2 as the outer limit.

  For example, as shown in FIG. 1C, the hole serving as the working fluid ejection port 25 has a working fluid ejection angle (θ) of 60 degrees or less (θ <60 degrees) from the hub side wall surface 23 with respect to the fluid flow direction. ). The working fluid ejection port 25 generally has a circular cross section, but is not limited to this, and may be an elongated slit along the pressure surface 24a as well as a cross sectional shape such as an ellipse or a quadrangle. .

  Further, the working fluid ejected from the working fluid ejection port 25 may be a fluid partially recirculated from the downstream of the diffuser 21 through the bleed passage 28, as shown in FIG. Fluid introduced from the source 40 may be used.

Since the centrifugal compressor 10 having such a working fluid injection port 25 opens to the hub side wall surface 23 and injects the working fluid Fa to the pressure surface 24a of the vane 24, it is injected to the pressure surface hub side of the vane 24. The working fluid thus joined merges with the distorted flow of the pressurized fluid discharged from the impeller 11 to suppress separation caused by the angle mismatch between the flow angle and the blade inlet angle.
That is, at the front edge portion of the vane 24, the fluid flow to be separated from the pressure surface 24 a around the front edge 24 c is ejected from the working fluid ejection port 25 along the pressure surface 24 a in the fluid flow direction. Since it is influenced by the working fluid Fa, it is difficult to separate from the pressure surface 24a. In other words, the flow of the fluid to be separated from the pressure surface 24a around the leading edge is separated by the flow of the working fluid Fa ejected from the working fluid ejection port 25 along the pressure surface 24a in the fluid flow direction. Since the flow toward is suppressed, it is difficult to separate from the pressure surface 24a.

Thus, by ejecting the working fluid from the working fluid injection port 25 to the pressure surface hub side of the vane 24, separation of the flow due to mismatch between the discharge flow of the impeller 11 and the blade inlet angle of the vane 24 is suppressed, As a result, the performance of the diffuser 21 and the centrifugal compressor 10 is improved.
In this case, in order to efficiently suppress the separation of the fluid flow from the pressure surface 24 a, the working fluid injection port 25 is formed in the region on the pressure surface 24 a side that is 10% or less of the throat width in the width direction of the throat 27. It is desirable to open the flow. That is, in the width direction of the throat 27, it is desirable to eject the working fluid from a position close to the pressure surface 24a that is a target for suppressing separation.

Further, the injection flow rate of the working fluid necessary for suppressing such separation is about 2 to 5% of the fluid flow rate to be compressed, and if it is 5% or more, there is almost no change in the effect of preventing separation, and 2% or less is sufficient. The effect of preventing peeling is not obtained.
The reason why the inner circumferential side limit is set to the minimum radius (Ro) for the radial position where the working fluid ejection port 25 is provided is that the effect of preventing separation by the ejection port working fluid becomes obvious, and the outer circumferential side limit is set to the throat radius. The reason why (R2) is selected is that there is almost no change in the peeling prevention effect above this.

Subsequently, in the second aspect of the present embodiment shown in FIG. 1 with respect to the fluid compressor 10 described above, the working fluid (arrow Fa in the figure) opens to the negative pressure surface 24 b of the vane 24 while opening in the shroud side wall surface 22. One or a plurality of working fluid ejection ports 26 for ejecting along the fluid flow direction are provided.
The working fluid ejection port 26 is provided at a radial position closer to the front edge 24c of the vane 24 than the throat radius (R2), as with the above-described working fluid ejection port 25. That is, although the position of the working fluid ejection port 26 differs from the first aspect described above as the shroud side wall surface 22, the basic matters such as the installation position (region) of the working fluid ejection port 26 and the working fluid are the hub. The side wall surface 23 may be read as the shroud side wall surface 22, and the pressure surface 24a may be read as the negative pressure surface 24a.

  According to such a centrifugal compressor 10, one or a plurality of working fluid ejection ports 26 that are opened in the shroud side wall surface 22 and eject the working fluid along the negative pressure surface 24 b of the vane 24 in the fluid flow direction are provided. Since the working fluid ejection port 26 is provided at a radial position on the front edge 24c side of the vane 24 from the throat radius (R2), the working fluid ejected to the suction surface shroud side of the vane 24 is discharged from the impeller 11. The flow is merged with the distorted flow to suppress separation caused by the angle mismatch between the flow angle and the blade inlet angle. As a result, the operating range of the diffuser 21 and the centrifugal compressor 10, specifically, the high flow rate value (upper limit) defined by the choke generation flow rate value from the low flow rate side (lower limit value) defined by the surging generation flow rate value. Value) can be expanded.

That is, the flow to be separated from the suction surface 24b at the leading edge 24c of the vane 24 is affected by the working fluid ejected from the working fluid ejection port 26 along the suction surface 24b in the fluid flow direction. It becomes difficult to separate from the pressure surface 24b. In this case, in order to suppress separation on the negative pressure surface 24b side, similarly to the working fluid injection port 25, the working fluid injection port 26 is opened in a region on the negative pressure surface 24b side that is 10% or less of the throat width. It is desirable to eject the fluid.
Also, the ratio of the injection flow rate to the fluid flow rate to be compressed, the inner circumferential limit is the minimum radius (Ro), the outer circumferential limit is the throat radius (R2), and the working fluid ejection angle (θ) is 60 degrees. The reason for the following, the supply source of the working fluid, and the like are the same as those of the working fluid ejection port 25 on the hub side wall surface 23 described above.

Finally, in the third aspect of the present embodiment shown in FIG. 1 with respect to the fluid compressor 10 described above, the working fluid opens along the pressure surface 24 a of the vane 24 and opens in the hub side wall surface 23. One or a plurality of working fluid jets 25 to be jetted, and one or a plurality of working fluid jets that open in the shroud side wall surface 22 and jet the working fluid along the negative pressure surface 24b of the vane 24 in the fluid flow direction. 26. That is, the working fluid ejection ports 25 and 26 of the first aspect and the second aspect described above are both provided.
With such a configuration, the effects of the first aspect and the second aspect described above can be obtained, so that the performance of the diffuser 21 and the centrifugal compressor 10 can be improved and the operating range can be expanded.

As described above, according to the present embodiment described above, the centrifugal compressor 10 and the like that improve the performance of the diffuser 21 including the vane 24 by suppressing the separation of the flow due to the angle mismatch between the discharge flow of the impeller 11 and the vane inlet. The centrifugal fluid machine can be provided.
In particular, the working fluid ejected from the working fluid ejection port 25 to the pressure surface hub side of the bay 24 is effective in improving the performance, and the working fluid ejected from the working fluid ejection port 26 to the suction surface shroud side of the vane 24 has a working range. Since it is effective for expansion, it is possible to realize a centrifugal fluid machine with a high pressure ratio and high efficiency and a wide operating range by injecting the working fluid to both the pressure surface hub side and the suction surface shroud side. .
In addition, this invention is not limited to embodiment mentioned above, For example, a centrifugal fluid machine is limited to a centrifugal fluid machine (a marine supercharger, a supercharger for vehicles, an aeronautical gas turbine, etc.). However, it can be appropriately changed within a range not departing from the gist thereof, such as including a centrifugal pump and a centrifugal blower.

10 Centrifugal compressor (centrifugal fluid machine)
11 Impeller 12 Blade 13 Hub 14 Shroud 21 Diffuser 22 Shroud Side Wall 23 Hub Side Wall 24 Vane (diffuser blade)
24a Pressure surface 24b Negative pressure surface 24c Front edge 25, 26 Working fluid injection port 27 Throat 28 Extraction flow path 40 Pressure source

Claims (5)

A plurality of blades, and an impeller having the plurality of blades;
A diffuser provided on the downstream side of the impeller and having a plurality of vanes between the opposing shroud side wall surface and the hub side wall surface;
A centrifugal fluid machine configured such that a fluid whose pressure is increased by rotating the impeller flows out through the diffuser,
There is provided one or a plurality of working fluid jets that open in the side wall surface of the hub and jet the working fluid along the pressure surface of the vane in the fluid flow direction, and the working fluid jet port has a throat radius (R2). The centrifugal fluid machine is further provided at a radial position on the leading edge side of the vane. A plurality of blades, and an impeller having the plurality of blades;
A diffuser provided on the downstream side of the impeller and having a plurality of vanes between the opposing shroud side wall surface and the hub side wall surface;
A centrifugal fluid machine configured such that a fluid whose pressure is increased by rotating the impeller flows out through the diffuser,
One or a plurality of working fluid ejection ports that open to the shroud side wall surface and inject the working fluid along the suction surface of the vane in the fluid flow direction, and the working fluid ejection port has a throat radius (R2). The centrifugal fluid machine is further provided at a radial position on the leading edge side of the vane.   The radial position at which the working fluid ejection port is provided has a minimum radius (Ro) of 95% based on the leading edge radius (R1) of the vane as an inner limit, and the throat radius (R2) as an outer limit. The centrifugal fluid machine according to claim 1 or 2, characterized by the above.   The working fluid ejection angle (θ) of the working fluid ejection port is set so as to be 60 degrees or less from the wall surface with respect to the flow direction of the fluid. The centrifugal fluid machine according to Item. The centrifuge according to any one of claims 1 to 4, wherein the working fluid uses a fluid partially recirculated from the downstream of the diffuser or a fluid introduced from an external pressure source. Fluid machine.

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