JP6191114B2 - Centrifugal compressor - Google Patents

Description

  The present invention relates to a centrifugal compressor.

  In a centrifugal compressor, velocity energy is imparted to a fluid such as air by a radial impeller, and the fluid to which the velocity energy is imparted is decelerated by a diffuser and pressurized to compress the fluid.

  In such a centrifugal compressor, guide vanes for guiding fluid to the diffuser are installed. This guide vane directs the fluid sent in the radial direction of the radial impeller in the flow direction of the scroll flow path so that the fluid sent from the radial impeller flows smoothly into the scroll flow path provided outside the diffuser. I will guide you.

  By the way, when the guide vanes are installed, the cross section of the flow path becomes small at a portion where the guide vanes are close to each other, and a region where the pressure loss is locally increased occurs. Such a region is a region having the highest pressure loss in the diffuser and is called a throat region. For example, as described in Patent Document 1, in a centrifugal compressor having guide vanes, the pressure recovery rate in the region outside the throat region in the radial direction of the radial impeller is that in the region inside the throat region. It has the characteristic of decreasing with respect to the pressure recovery rate.

  Since the difference in the pressure recovery rate between the two regions sandwiching the throat region causes the occurrence of surging, in Patent Document 1, in the diffuser, the flow path height in the region inside the throat region is set to the throat region. The structure is gradually lowered toward the end. By adopting such a configuration, the pressure recovery rate in the inner region of the throat region is reduced, the pressure recovery rates of the two regions sandwiching the throat region can be brought close, and the occurrence of surging can be suppressed.

JP-A-11-294392

  However, according to Patent Document 1, although a great merit that the occurrence of surging can be suppressed is obtained, the flow passage area of the diffuser is reduced and the flow rate range is reduced.

  The present invention has been made in view of the above-described problems, and in a centrifugal compressor, without reducing the flow rate range, the pressure recovery rates of two regions sandwiching the throat region are brought close to suppress the occurrence of surging. With the goal.

  The present invention adopts the following configuration as means for solving the above-described problems.

  A first aspect of the present invention is a centrifugal compressor comprising a radial impeller that applies velocity energy to a fluid and sends the fluid radially, and a diffuser that decelerates and pressurizes the fluid sent from the radial impeller. Are provided around the radial impeller, a first annular flow path provided around the radial impeller, an outer side of the first annular flow path, and the first annular flow path. A second annular flow path having a larger flow path height than the annular flow path, and the throat region that is the region with the highest pressure loss between the guide vanes or on the downstream side of the throat region. A configuration is adopted in which a boundary between the first annular channel and the second annular channel is provided.

  In a second aspect based on the first aspect, the first annular flow path and the second annular flow path are formed between a pair of planar flow path wall surfaces that face each other in parallel. The configuration is adopted.

  According to a third invention, in the first or second invention, the guide blade is separated into two parts with a boundary between the first annular flow channel and the second annular flow channel interposed therebetween. Is adopted.

  In the present invention, the flow path in the diffuser is divided into a first annular flow path on the radial inner side of the radial impeller and a second annular flow path on the outer side in the radial direction. Is set larger than the channel height of the first annular channel. By setting the flow path height to be large, the spatial volume of the second annular flow path is increased, and the pressure recovery rate in the second annular flow path is higher than that in the case where the flow path height is the same as that of the first annular flow path. growing. Furthermore, in the present invention, the boundary between the first annular flow path and the second annular flow path is provided on the throat region with the highest pressure loss or on the downstream side of the throat region.

  According to the present invention as described above, the pressure recovery rate on the radially outer side of the radial impeller is increased with the throat region or the downstream side of the throat region as a boundary, and the pressure recovery rate of the two regions sandwiching the throat region is increased. You can get closer. Therefore, occurrence of surging can be suppressed. In addition, according to the present invention, it is possible to suppress surging by changing the channel cross-sectional area of the second annular channel larger than that of the first annular channel without changing the channel cross-sectional area of the first annular channel. Is realized. For this reason, there is no site | part where a flow-path cross section reduces in a diffuser, and the maximum flow volume which can pass a diffuser can be maintained. Therefore, the flow range is not reduced.

  As described above, according to the present invention, in the centrifugal compressor, it is possible to bring the pressure recovery rates of the two regions sandwiching the throat region close to each other and reduce the occurrence of surging without reducing the flow rate range.

(A) is a longitudinal cross-sectional view which shows schematic structure of the centrifugal compressor which concerns on one Embodiment of this invention, (b) is a principal part expansion containing the diffuser with which the centrifugal compressor which concerns on one Embodiment of this invention is equipped. FIG. (A) is the figure which showed a part of housing and guide blade with which the centrifugal compressor which concerns on one Embodiment of this invention is provided, It is the figure seen from the right side of Fig.1 (a), (b) These are the graphs for comparing the pressure recovery rate in the diffuser with which the centrifugal compressor which concerns on one Embodiment of this invention is provided, and the pressure recovery rate in the diffuser in the conventional centrifugal compressor. (A) is a longitudinal cross-sectional view which shows schematic structure of the modification of the centrifugal compressor which concerns on one Embodiment of this invention, (b) is equipped with the modification of the centrifugal compressor which concerns on one Embodiment of this invention. It is a principal part enlarged view containing a diffuser. It is a principal part enlarged view containing the diffuser with which the modification of the centrifugal compressor which concerns on one Embodiment of this invention is provided.

  Hereinafter, an embodiment of a centrifugal compressor according to the present invention will be described with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size. Moreover, in the following description, the example applied to the centrifugal compressor which produces | generates compressed air as a centrifugal compressor which concerns on this invention is demonstrated.

  Fig.1 (a) is a longitudinal cross-sectional view which shows schematic structure of the centrifugal compressor 1 of this embodiment, FIG.1 (b) is a principal part expansion containing the diffuser 7 with which the centrifugal compressor 1 of this embodiment is provided. FIG. As shown in FIG. 1A, the centrifugal compressor 1 of the present embodiment includes a radial impeller 2, a shaft 3, a seal plate 4, a housing 5, bolts 6, and a diffuser 7.

  The radial impeller 2 includes a plurality of blades 2b that are fixed to the base 2a. The radial impeller 2 is rotationally driven, thereby giving velocity energy to the air X (fluid) sucked from the axial direction and sending it out in the radial direction. The shaft 3 is fixed to the center of the radial impeller 2 when viewed from the air X intake direction of the radial impeller 2, and rotational power generated by a drive source (not shown) (motor, turbine, etc.) is supplied to the radial impeller 2. introduce.

  The seal plate 4 is disposed so as to face the back surface of the radial impeller 2, and a through hole for inserting the shaft 3 is provided at the center. The housing 5 is a casing that covers the radial impeller 2 from the air X suction side by being fastened to the seal plate 4 with bolts 6. As shown in FIG. 1 (a), the housing 5 has a suction port 5a for sucking air X, a discharge port 5b for discharging air X, and a discharge port 5b for discharging air X sent from the radial impeller 2. And a scroll flow path 5c that leads to The scroll channel 5c is formed outside the radial impeller 2 so as to surround the radial impeller 2 when viewed from the air X suction direction, and the radial impeller 2 is centered when viewed from the same direction. Air X is guided in the circumferential direction. That is, the flow direction of the air X in the scroll flow path 5 c is set to the circumferential direction around the rotation axis of the radial impeller 2. The bolts 6 fasten the seal plate 4 and the housing 5, and a plurality of bolts 6 are discretely provided in the circumferential direction around the rotational axis of the radial impeller 2.

  The diffuser 7 is provided between the radial impeller 2 and the scroll passage 5c, and as shown in FIG. 1B, the first annular passage 7a, the second annular passage 7b, and the guide vane 7c. And.

  The first annular channel 7 a is an annular channel that is provided closer to the radial impeller 2 than the second annular channel 7 b and surrounds the radial impeller 2. As shown in FIG. 1B, the first annular channel 7a is formed between a pair of channel wall surfaces 7a1 and 7a2 facing each other in parallel. The channel wall surface 7a1 is a flat wall surface formed of a part of the surface of the seal plate 4. Further, the flow path wall surface 7 a 2 is a flat wall surface formed of a part of the surface of the housing 5. The flow path height H1 (the size in the axial direction of the radial impeller 2) of the first annular flow path 7a is set to be lower than the height of the blades 2b of the radial impeller 2. In the present embodiment, the flow path height H1 of the first annular flow path 7a is set lower than the height of the blades 2b of the radial impeller 2, but the present invention is not limited to this. For example, a configuration in which the channel height H1 of the first annular channel 7a is the same as or higher than the height of the blades 2b of the radial impeller 2 may be employed.

  The second annular channel 7b is an annular channel that is provided outside the first annular channel 7a, is connected to the first annular channel 7a, and surrounds the first annular channel 7a. As shown in FIG. 1B, the second annular channel 7b is formed between a pair of channel wall surfaces 7b1 and 7b2 facing each other in parallel. The flow path wall surface 7 b 1 is a flat wall surface formed of a part of the surface of the seal plate 4. Further, the flow path wall surface 7 b 2 is a flat wall surface formed of a part of the surface of the housing 5.

  As shown in FIG. 1B, the channel wall surface 7b1 and the channel wall surface 7b2 forming the second annular channel 7b are formed by the channel wall surface 7a1 and the channel wall surface 7a2 forming the first annular channel 7a. Are confronted in parallel at wide intervals. For this reason, the channel height H2 of the second annular channel 7b is larger than the channel height H1 of the first annular channel 7a. As shown in FIG. 1B, in the present embodiment, a step is provided on the surface of the housing 5, and the channel wall surface 7b2 is provided at a position farther from the seal plate 4 than the channel wall surface 7a2. Thus, the flow path height H2 is set to be larger than the flow path height H1.

  The guide vane 7c is provided so as to straddle the first annular channel 7a and the second annular channel 7b. In the guide vane 7c, the blade height H3 of the portion provided in the first annular channel 7a is the same as the channel height H1 of the first annular channel 7a. The blade height H4 of the portion to be provided is the same height as the channel height H2 of the second annular channel. Further, both end surfaces of the guide vane 7c are wall surfaces (the channel wall surface 7a1 and the channel wall surface 7a2) that form the first annular channel 7a and channel wall surfaces (the channel wall surface 7b1 and the channel wall surface that form the second annular channel 7b). It is an abutting surface with the channel wall surface 7b2). For example, the guide vane 7c includes a pin (not shown) protruding from both end faces, and this pin is inserted into a fitting hole formed in the flow path wall (the seal plate 4 and the housing 5 in this embodiment). Is positioned and supported.

  FIG. 2A is a view showing a part of the housing 5 and the guide vane 7c, as viewed from the right side of FIG. As shown in this figure, the guide vane 7c is arranged so that the leading edge faces the radial impeller 2 and the trailing edge faces the downstream side in the flow direction of the scroll flow path 5c, and is sent out from the radial impeller 2. The air X is guided toward the flow direction of the scroll flow path 5c. As shown in FIG. 2A, a plurality of such guide vanes 7c are installed at equal intervals, and are arranged in an annular shape with the radial impeller 2 at the center. Such guide vanes 7c guide the air X sent out from the radial impeller 2 toward the flow direction of the scroll flow path 5c.

  As shown in FIG. 2A, in the diffuser 7, for example, a throat region R where pressure loss is highest is formed in a region where the guide blades 7 c are closest to each other and the flow path cross-section is reduced or in the vicinity thereof. Such throat area | region R is formed in all between the some guide blades 7c. In the centrifugal compressor 1 of the present embodiment, the boundary K between the first annular flow path 7a and the second annular flow path 7b has an annular shape surrounding the radial impeller 2, and is disposed so as to pass through all the throat regions R. Has been. That is, in the centrifugal compressor 1 of the present embodiment, the boundary between the first annular flow path 7a and the second annular flow path 7b is located in the throat region R that is between the guide blades 7c and has the highest pressure loss. K is provided.

  In the centrifugal compressor 1 of the present embodiment configured as described above, the rotational power is transmitted to the radial impeller 2 through the shaft 3, and when the radial impeller 2 is driven to rotate, air is introduced into the housing 5 from the suction port 5a. X flows in. The air X flowing in from the suction port 5a is given velocity energy by the radial impeller 2 and is sent out in the radial direction of the radial impeller 2. The air X sent out from the radial impeller 2 in this way is increased in pressure by being decelerated by the diffuser 7, and is discharged as compressed air from the discharge port 5b through the scroll flow path 5c.

  The operation and effect of the centrifugal compressor 1 of the present embodiment as described above will be described. In the centrifugal compressor 1 of the present embodiment, the flow path in the diffuser 7 is divided into a first annular flow path 7a radially inward of the radial impeller 2 and a second annular flow path 7b radially outward. The channel height H2 of the second annular channel 7b is set to be greater than the channel height H1 of the first annular channel 7a. By setting the flow path height large, the spatial volume of the second annular flow path 7b increases, and the pressure recovery rate in the second annular flow path 7b makes the flow path height the same as that of the first annular flow path 7a. Larger than the case. Furthermore, in the centrifugal compressor 1 of the present embodiment, the boundary K between the first annular flow path 7a and the second annular flow path 7b is provided in the throat region R with the highest pressure loss.

  FIG. 2B shows the pressure recovery rate in the diffuser 7 in the centrifugal compressor 1 of the present embodiment, and the conventional centrifugal compressor (the pressure recovery rate in the second annular flow path 7b determines the flow path height in the first annular shape. It is a graph for comparing with the pressure recovery rate in a diffuser in the centrifugal compressor which is the same as the flow path. In FIG. 2B, the slope of the graph indicated by the solid line indicates the pressure recovery rate in the diffuser 7 in the centrifugal compressor 1 of the present embodiment, and the slope of the graph indicated by the broken line in the conventional centrifugal compressor. It shows the pressure recovery rate at the diffuser. In FIG. 2B, the horizontal axis indicates the radial position with the radial impeller 2 side as the origin, the vertical axis indicates the static pressure of the air X, and the slope of the graph indicates the pressure recovery rate.

  As can be seen from FIG. 2 (b), according to the centrifugal compressor 1 of the present embodiment, the pressure recovery rate on the radially outer side of the radial impeller 2 is increased with the throat region R as a boundary. The pressure recovery rate of the two regions sandwiched can be made closer. Therefore, occurrence of surging can be suppressed.

  Further, according to the centrifugal compressor 1 of the present embodiment, the flow passage cross-sectional area of the second annular flow passage 7b is changed from that of the first annular flow passage 7a without changing the flow passage cross-sectional area of the first annular flow passage 7a. As a result, the surging is suppressed. For this reason, there is no portion in the diffuser 7 where the flow path cross section is reduced as compared with the conventional centrifugal compressor, and the maximum flow rate that can pass through the diffuser 7 can be maintained. Therefore, the flow range is not reduced.

  Therefore, according to the centrifugal compressor 1 of the present embodiment, the pressure recovery rate of the two regions (the first annular channel 7a and the second annular channel 7b) sandwiching the throat region R without reducing the flow rate range. Accordingly, it is possible to suppress the occurrence of surging.

  Further, in the centrifugal compressor 1 of the present embodiment, the first annular flow path 7a and the second annular flow path 7b are a pair of planar flow path wall surfaces (flow path wall surface 7a1 and flow path) that face each other in parallel. The road wall surface 7a2 and the channel wall surface 7b1 and the channel wall surface 7b2) are formed. For this reason, both the abutting surfaces of the guide vanes 7c and the flow path wall surfaces are flat. Therefore, in the centrifugal compressor 1 of the present embodiment, the shape of the abutting surface of the guide blade 7c is a simple flat surface, and it is possible to prevent the processing accuracy and assembly accuracy of the guide blade 7c from being deteriorated.

  If the boundary K between the first annular flow path 7a and the second annular flow path 7b cannot be overlapped with the throat region R due to layout and processing restrictions, the boundary K is downstream of the throat region R. It may be arranged on the side. Even in such a case, since the pressure recovery rate in the downstream region of the throat region R is increased, the two regions (the first annular channel 7a and the first annular channel 7a) sandwiching the throat region R without decreasing the flow rate range. The pressure recovery rate of the two annular channels 7b) can be made close to suppress the occurrence of surging.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the said embodiment. Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the spirit of the present invention.

  For example, in the above-described embodiment, a configuration is adopted in which one guide blade 7c straddles the first annular channel 7a and the second annular channel 7b. However, when such a configuration is adopted, the height of the guide vane 7c differs between the part installed in the first annular flow path and the part installed in the second annular flow path. The shape becomes complicated. Therefore, for example, as shown in FIG. 3A and FIG. 3B, the guide vane 7c is placed between the portion 7c1 installed in the first annular channel and the second annular channel with the boundary K as a boundary. You may isolate | separate into the site | part 7c2 installed. As a result, each part has a simple shape in which the blade height does not change midway, so that it is possible to prevent deterioration in the processing accuracy and assembly accuracy of the guide blade 7c. In the example shown in FIG. 3, the boundary K is arranged slightly displaced downstream from the throat region R.

  Further, for example, as shown in FIG. 4, the boundary K between the first annular flow path 7a and the second annular flow path 7b avoids the portion K1 along each throat region R and the installation region of the guide vanes 7c. You may comprise so that it may consist of the site | part K2 which connects site | part K1. In such a case, since the boundary K is formed along the throat region R between the guide blades 7c, the boundary K is disposed so as to be orthogonal to the flow direction of the air X. It is possible to prevent the timing at which pressure recovery occurs depending on the position where the gas flows. Therefore, it is possible to perform pressure recovery stably. Furthermore, since the boundary K is provided avoiding the installation area of the guide vanes 7c, the height from the front edge to the rear edge of the guide vanes 7c can be made the same. For this reason, it is possible to easily perform the assembling work of the guide vanes 7c.

  Further, in the above-described embodiment, a step is provided on the surface of the housing 5, and the flow path height H2 flows because the flow path wall surface 7b2 is provided at a position farther from the seal plate 4 than the flow path wall surface 7a2. It is made larger than the road height H1. However, the present invention is not limited to this, and a flow path height H2 is provided by providing a step on the surface of the seal plate 4 and providing the flow path wall surface 7a1 at a position farther from the housing 5 than the flow path wall surface 7a1. May be larger than the flow path height H1.

  Moreover, in the said embodiment, the centrifugal compressor which produces | generates compressed air was demonstrated. However, the present invention is not limited to this, and can be applied to a centrifugal compressor that compresses another fluid.

  In the above embodiment, the flow path wall surface 7 a 1 and the flow path wall surface 7 b 1 are part of the surface of the seal plate 4, and the flow path wall surface 7 a 2 and the flow path wall surface 7 b 2 are part of the surface of the housing 5. explained. However, the present invention is not limited to this. For example, when the guide vane 7c is fixed to the vane plate and this vane plate is fixed to the seal plate 4 or the housing 5, the flow path wall surface 7a1, the flow path wall surface 7b1, the flow path wall surface 7a2, and the flow path wall surface 7b2 are vane. A configuration comprising a part of the surface of the plate can also be adopted. In some cases, a shroud for adjusting a gap with the radial impeller 2 may be provided on the housing 5 side. In such a case, a configuration in which the flow path wall surface 7a2 and the flow path wall surface 7b2 are part of the surface of the shroud may be employed.

  DESCRIPTION OF SYMBOLS 1 ... Centrifugal compressor, 2 ... Radial impeller, 2a ... Base, 2b ... Blade, 3 ... Shaft, 4 ... Seal plate, 5 ... Housing, 5a ... Suction port, 5b ... Discharge port 5c: scroll channel, 6: bolt, 7: diffuser, 7a: first annular channel, 7a1: channel wall surface, 7a2: channel wall surface, 7b: second annular channel, 7b1... Channel wall surface, 7b2... Channel wall surface, 7c .. Guide vane, 7c1 .. Site, 7c2 .. Site, K .. Boundary, R .. Throat region, X .. Air (fluid)

Claims (3)

A centrifugal compressor comprising a radial impeller that applies velocity energy to a fluid and sends the fluid in a radial direction, and a diffuser that decelerates and pressurizes the fluid sent from the radial impeller,
The diffuser is
A plurality of guide vanes arranged annularly with the radial impeller at the center;
A first annular flow path provided in parallel with the opposing flow path wall surface and surrounding the radial impeller;
The opposed channel wall surfaces are parallel and are provided outside the first annular channel, and the height of the channel, which is the axial size of the radial impeller, is larger than the first annular channel due to the step. Two annular channels;
With
Centrifugation in which a boundary between the first annular flow channel and the second annular flow channel is provided between the guide blades and in the throat region which is the region with the highest pressure loss or downstream of the throat region. Compressor.   The centrifugal compressor according to claim 1, wherein the first annular channel and the second annular channel are formed between a pair of planar channel walls facing each other in parallel.   The centrifugal compressor according to claim 1 or 2, wherein the guide vane is separated into two parts across a boundary between the first annular flow path and the second annular flow path.

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