JP6160079B2 - Centrifugal compressor - Google Patents

Description

  The present invention relates to a centrifugal compressor that pressurizes a gas by the action of centrifugal force.

  A centrifugal compressor is a device that rotates a compressor impeller (impeller), passes gas through a flow path in a radial direction in the rotating compressor impeller, and boosts the gas mainly by the action of centrifugal force. Such centrifugal compressors are used for industrial compressors and gas turbines, for example.

  In such a centrifugal compressor, when the flow rate of the gas taken into the centrifugal compressor is small or the pressure ratio is high and the rotation speed cannot be set sufficiently high, the specific speed is reduced and the compression efficiency is deteriorated. Therefore, techniques for improving efficiency by increasing the number of compressors have been proposed (for example, Patent Documents 1 and 2).

US Patent Application Publication No. 2007/0122296 U.S. Pat. No. 4,428,715

  However, each of the multistage centrifugal compressors disclosed in Patent Documents 1 and 2 has a complicated structure, and there is a problem in that the manufacturing cost increases. In addition, there is a housing for forming a flow path between multiple compressor impellers configured in multiple stages, so multiple compressor impellers must be installed separately, and sufficient rigidity cannot be obtained. There is also a problem that the balance with respect to the rotating shaft cannot be sufficiently obtained.

  Here, among the multistage centrifugal compressors, by providing the downstream compressor impeller on the radially outer side of the upstream compressor impeller, it is possible to facilitate the assembly without including a housing between them. However, the function of the single stage centrifugal compressor does not change if the radial outer dimensions allowed for the centrifugal compressor are simply bisected, and the specific speed is still low.

  In view of the above problems, an object of the present invention is to provide a centrifugal compressor capable of increasing the specific speed and improving the compression efficiency while simplifying the incorporation of the compressor impeller.

In order to solve the above-described problems, a centrifugal compressor according to the present invention includes a rotating shaft, an upstream impeller body fixed to the rotating shaft, and a plurality of upstream members arranged at intervals in the circumferential direction of the upstream impeller body. an upstream compressor impeller that Yusuke and side wings, the upstream compressor impeller and is integrally formed in the axial direction of the rotating shaft, or axis of the formed upstream compressor impeller and another body upstream compressor impeller rotary shaft are connected in the direction, and fixed to the rotary shaft downstream impeller body, and a downstream compressor impeller that having a, a plurality of downstream blades arranged at intervals in the circumferential direction of the downstream impeller body, comprising a output side outermost diameter of the upstream compressor wheel is an input-side outermost diameter or less of a downstream compressor wheel, an input side innermost diameter of the plurality of downstream wing, a plurality of upstream blade Output side has smaller than the outermost diameter.

A communication passage for communicating the input side of the output side and the downstream side compressor impeller upstream compressor impeller, provided in the communication passage, and the diffuser you position radially outward of the output side of the upstream compressor impeller, a further You may prepare.

A communication passage for communicating the input side of the output side and the downstream side compressor impeller upstream compressor impeller, and a return guide vane you position radially outside the input side of the downstream compressor wheel may further comprise a .

You may further provide the compressor housing in which an upstream compressor impeller and a downstream compressor impeller are accommodated, and the labyrinth seal provided in the boundary of an upstream impeller main body and a compressor housing.
In order to solve the above-described problems, another centrifugal compressor of the present invention is provided with a shaft, an upstream compressor impeller provided on the shaft, and provided integrally with the upstream compressor impeller in the axial direction of the shaft. Or an upstream compressor impeller formed separately from the upstream compressor impeller and connected in the axial direction of the shaft, and the upstream compressor impeller is spaced apart in the circumferential direction of the main body. The downstream compressor impeller includes a plurality of downstream blades arranged at intervals in the circumferential direction of the main body, and the output compressor outermost diameter of the upstream compressor impeller is the downstream compressor. It is less than the outermost diameter on the input side of the impeller.
Input innermost diameter of the downstream wings multiple may be smaller than the output-side outermost diameter of the plurality of upstream blade.
A communication passage that communicates the output side of the upstream compressor impeller and the input side of the downstream compressor impeller, and a diffuser that is provided in the communication passage and is located on the radially outer side of the output side of the upstream compressor impeller. Also good.
You may further provide the communicating path which connects the output side of an upstream compressor impeller, and the input side of a downstream compressor impeller, and the return guide vane located in the radial direction outer side of the input side of a downstream compressor impeller.

  According to the present invention, it is possible to increase the specific speed while simplifying the incorporation of the compressor impeller and to improve the compression efficiency.

It is a schematic sectional drawing of a centrifugal compressor. It is explanatory drawing for demonstrating the relationship between the specific speed and compression efficiency of a single stage type centrifugal compressor and a multistage type centrifugal compressor. It is explanatory drawing seen from the front side for demonstrating the relationship between an upstream compressor impeller and a diffuser. It is explanatory drawing seen from the front side for demonstrating the relationship between a downstream compressor impeller and a return guide vane. It is an enlarged view of A part of Fig.1 (a). It is a schematic sectional drawing which shows the other example of a centrifugal compressor.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating the understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Centrifugal compressor 1)
FIG. 1 is a schematic cross-sectional view of a centrifugal compressor 1. Hereinafter, the direction of the arrow indicated by F will be described as the front side of the centrifugal compressor 1, and the direction of the arrow indicated by R will be described as the rear side of the centrifugal compressor 1. In the description of the compressor impeller described later, the input side indicates the most upstream side of the gas flow in the compressor impeller, and the output side indicates the most downstream side of the gas flow in the compressor impeller. As shown in FIG. 1A, the centrifugal compressor 1 includes a compressor housing 2 and a casing 3 connected to the rear side of the compressor housing 2. The centrifugal compressor 1 can be used for various applications such as an industrial compressor, a gas turbine (combustion air compression), a supercharger, a blower, and a cooling device. Further, the centrifugal compressor 1 has an advantage that it can be made smaller and lighter than the axial flow type compressor.

  On the rear side of the casing 3, for example, a bearing housing (not shown) having a bearing hole in the front-rear direction of the centrifugal compressor 1 is provided, and a shaft 4 as a rotating shaft is rotatably supported by the bearing hole via a bearing. Has been. An upstream compressor impeller 5 and a downstream compressor impeller 6 are formed concentrically and integrally at the front end of the shaft 4 (may be formed separately and connected together), and this upstream compressor impeller. 5 and a downstream compressor impeller 6 are rotatably accommodated in the compressor housing 2 (when both the upstream compressor impeller 5 and the downstream compressor impeller 6 are indicated, they are simply referred to as a compressor impeller). A drive source (not shown) is connected to the rear end portion of the shaft 4, and the upstream compressor impeller 5 and the downstream compressor impeller 6 are forcibly rotated by the drive source.

  The upstream compressor impeller 5 includes an upstream impeller body 5a fixed to the shaft 4 and a plurality of upstream blades 5b arranged at intervals in the circumferential direction of the upstream impeller body 5a. Similarly, the downstream compressor impeller 6 includes a downstream impeller body 6a fixed to the shaft 4 and a plurality of downstream blades 6b arranged at intervals in the circumferential direction of the downstream impeller body 6a. The In FIG. 1 (a), only the upstream impeller body 5a and the downstream impeller body 6a are hatched. However, the upstream impeller body 5a and the upstream blade 5b are also connected to the downstream impeller body 6a and the downstream blade 6b. Are integrally formed. However, it does not exclude being formed separately.

  The compressor housing 2 is formed with an intake port 7 that faces the upstream compressor impeller 5 and that is concentric with the upstream compressor impeller 5 and opens to the front side of the centrifugal compressor 1. Here, the upstream compressor impeller 5 and the downstream compressor impeller 6 are rotated by the drive source, the input side of the upstream compressor impeller 5 becomes negative pressure, and gas is sucked from the intake port 7.

  The output side of the upstream compressor impeller 5 and the input side of the downstream compressor impeller 6 communicate with each other through a communication path 8. Since the communication path 8 communicates the output side of the upstream compressor impeller 5 and the input side of the downstream compressor impeller 6 in the circumferential direction, an annular space is formed around the shaft 4. In addition, a flow path 9 communicating with the circumferential direction is formed on the output side of the downstream compressor impeller 6. The flow path 9 further communicates with an annular compressor scroll flow path 10 located on the radially outer side of the shaft 4 from the downstream compressor impeller 6. The compressor scroll flow path 10 communicates with a discharge port (not shown) that discharges compressed air.

  Therefore, when the upstream compressor impeller 5 rotates via the shaft 4, gas is sucked into the compressor housing 2 from the intake port 7, and the sucked gas is upstream of the upstream impeller body 5 a of the upstream compressor impeller 5. Between the compressor housing 2 and the shroud surface 2a of the compressor housing 2, and is compressed by the action of centrifugal force to escape to the communication passage 8. Then, it again passes between the downstream side impeller body 6a of the downstream side compressor impeller 6 and the shroud surface 2b of the compressor housing 2, and is discharged into the flow path 9 by the action of centrifugal force. The pressure is increased and guided to the discharge port.

  Thus, in this embodiment, the compressor impeller is configured in at least two stages, and the gas compressed by the first-stage upstream compressor impeller 5 is further pressurized by the second-stage downstream compressor impeller 6. .

  If the compressor impeller is formed in a single stage, the blade height must be lowered if the flow rate of the gas taken into the centrifugal compressor is small. In addition, the number of rotations (rotation speed) may not be sufficiently high for reasons such as strength limitations. If it does so, specific speed will become small and compression efficiency will worsen. Therefore, as described above, by configuring the compressor impeller with a plurality of stages (here, two stages), the work per stage can be reduced and the specific speed can be increased. Then, even if the rotation speed is low, the gas can be compressed with high efficiency.

…（数式１）
ここで、Ｎは回転数（ｒｐｍ）、Ｑは体積流量（ｍ^３／ｍｉｎ）、Ｃｐは定圧比熱（Ｊ／ｋｇ・Ｋ）、Ｔは温度（Ｋ）、Πは圧力比、γは比熱比である。 FIG. 2 is an explanatory diagram for explaining the relationship between the specific speed Ns and the compression efficiency η of the single-stage centrifugal compressor and the multistage centrifugal compressor. The specific speed Ns can be expressed by Equation 1 below.

... (Formula 1)
Here, N is the rotational speed (rpm), Q is the volume flow rate (m ³ / min), Cp is the constant pressure specific heat (J / kg · K), T is the temperature (K), Π is the pressure ratio, and γ is the specific heat ratio. It is.

  For example, in a single-stage centrifugal compressor, when an assumed volume flow Q, temperature T, and pressure ratio are determined, a specific speed Ns is also determined. It is only necessary to employ a rotational speed N that allows the specific speed Ns to be an optimum value (0.12). However, as described above, the rotational speed N is set to, for example, only about half of the optimum value due to constraints such as strength. If this is not possible, the specific speed Ns decreases to 0.06, and the compression efficiency η also decreases as indicated by the black circles indicated by arrows in FIG.

  On the other hand, in the multistage centrifugal compressor of the present embodiment, work is distributed in a plurality of stages, so that the specific speed Ns can also be dispersed as 0.08 and 0.10, for example, as indicated by white circles in FIG. The pressure efficiency of each stage becomes higher than the pressure efficiency in the case of a single stage, and the overall compression efficiency can be maintained.

  In addition, by reducing the work per stage, it is possible to reduce the circumferential speed component while maintaining the radial speed component of the gas output from the output side of the compressor impeller. Pressure loss can also be reduced.

  Furthermore, compared to the single-stage type, the outer diameter of each compressor impeller can be reduced, and the surface area (contact area with the gas) on the back of the impeller can be reduced. It is possible to reduce the load, that is, reduce the loss of the bearing.

Here, the structures of the upstream compressor impeller 5 and the downstream compressor impeller 6 will be described. Referring to FIG. 1B in which the upstream compressor impeller 5 and the downstream compressor impeller 6 are extracted from FIG. 1A, the following features are obtained. First, the output side an outermost diameter of the upstream compressor impeller 5, i.e., the output-side outermost diameter L ₁ of the upstream impeller body 5a, the input-side outermost diameter of the downstream compressor impeller 6, i.e., the input of the downstream-side blade 6b The outermost diameter L ₂ is set to be equal to or smaller than the outermost diameter L ₂ (or the innermost diameter of the shroud surface 2b).

  In this way, the upstream compressor impeller 5 and the downstream compressor impeller 6 can be smoothly assembled into the compressor housing 2 from the rear of the compressor housing 2 while being fixed to the shaft 4 without being disassembled. it can. With such a simple configuration, it is possible to assemble compressor impellers in multiple stages while avoiding an increase in manufacturing cost. Further, by configuring the compressor impeller integrally from the beginning, sufficient rigidity can be obtained and a sufficient balance with respect to the shaft 4 can be obtained.

Further, in the present embodiment, the input side innermost diameter L ₃ of the plurality of downstream-side blade 6b is configured to be smaller than the output-side outermost diameter L ₄ of the plurality of upstream blade 5b. By doing so, the sum of the radial lengths of the upstream blade 5b and the downstream blade 6b can be made longer than that of the single-stage type, so that the compression effect can be enhanced. Then, even when the flow rate is small, the specific speed can be increased and the compression efficiency can be improved.

  Moreover, in this embodiment, the diffuser 11a, 11b is provided in the communicating path 8 or the flow path 9 in order to improve compression efficiency. Here, the diffuser 11a provided in the communication path 8 will be described as an example.

  FIG. 3 is an explanatory diagram viewed from the front side for explaining the relationship between the upstream compressor impeller 5 and the diffuser 11a. Here, in order to facilitate understanding, the upstream blade 5b and the diffuser 11a are hatched. As shown in FIGS. 1 (a) and 3, the diffuser 11a is located on the radially outer side on the output side of the upstream compressor impeller 5, and converts the kinetic energy of the gas added by the upstream compressor impeller 5 into pressure energy. Convert.

  Specifically, when the upstream compressor impeller 5 rotates around the shaft 4 as indicated by a white arrow, the gas sucked in the front-rear direction of the centrifugal compressor 1 is a plane perpendicular to the shaft 4 due to the centrifugal force. It changes its direction in the direction (direction of communication path 8) and flows. In the communication path 8, the gas flows at a speed v in the direction of the solid arrow in FIG. The distance between adjacent diffusers 11a increases as the distance from the shaft 4 increases in the radial direction. The velocity of the gas decreases because the cross section of the flow path becomes wider, but the pressure energy increases instead of the kinetic energy.

  In the present embodiment, a return guide vane 12 is provided in the communication path 8 in order to improve compression efficiency (see FIG. 1A).

  FIG. 4 is an explanatory view seen from the front side for explaining the relationship between the downstream compressor impeller 6 and the return guide vane 12. Here, in order to facilitate understanding, the downstream blade 6b and the return guide vane 12 are hatched. As shown in FIGS. 1A and 4, the return guide vane 12 is located on the radially outer side of the gas input side of the downstream compressor impeller 6, and indicates the direction of the gas pressurized by the upstream compressor impeller 5. The circumferential speed component is suppressed by gradually changing in the radial direction.

Specifically, when the downstream compressor impeller 6 rotates around the shaft 4 as indicated by a white arrow, the gas pressurized by the upstream compressor impeller 5 passes through the diffuser 11a in the communication passage 8 and is downstream. Sucked into the input side of the compressor impeller 6. In this case, the communication passage 8, the gas, in FIG. 4, flows at a velocity v ₁ in the direction of solid arrow. The gas velocity v ₁ can be decomposed into a radial velocity component vr and a circumferential velocity component vθ. Since the adjacent return guide vanes 12 are formed such that the angle with the radial direction becomes smaller as the blade approaches the shaft 4, the angle between the direction of the fluid and the radial direction as it approaches the shaft 4. Becomes smaller, for example, the absolute value is equal to the speed v ₂ (| v ₁ | = | v ₂ |), and the speed v ₂ is obtained. That is, it is possible to increase the radial speed component vr and reduce the circumferential speed component vθ while maintaining the absolute value of the speed v ₁ .

  In this way, by returning the gas flow to the radial direction, the gas sucked into the input side of the downstream compressor impeller 6 flows in the radial direction as in the upstream compressor impeller 5, and therefore the inlet of the downstream compressor impeller 6. Can suppress the swirl flow and increase the pressure ratio.

  Further, since the upstream compressor impeller 5 and the compressor housing 2 rotate relative to each other, a clearance is provided at the boundary between the both in order to avoid contact between the two. However, if the clearance is simply increased, the original flow that flows from the surface (blade surface) of the upstream impeller body 5a on which the upstream blade 5b is provided to the back surface of the upstream impeller body 5a via the communication passage 8. Different from the flow, a direct flow between the blade surface and the back surface of the upstream impeller body 5a occurs.

  FIG. 5 is an enlarged view of a portion A in FIG. In order to avoid such a direct flow of gas between the blade surface and the back surface of the upstream impeller body 5a, the upstream impeller is located at the boundary between the upstream impeller body 5a and the compressor housing 2 as shown in FIG. A labyrinth seal 13 that suppresses gas flow between the blade surface and the back surface of the main body 5a is provided. The labyrinth seal 13 has a plurality of concave and convex gaps between the rotating side (upstream compressor impeller 5) and the fixed side (compressor housing 2), and has a sealing property by changing the differential pressure stepwise. It is a thing. With this configuration, it is possible to maintain the original flow from the blade surface of the upstream impeller body 5a to the back surface of the upstream impeller body 5a via the communication path 8 while ensuring the rotation of the upstream compressor impeller 5. It becomes possible.

(Modification)
FIG. 6 is a schematic cross-sectional view showing another example of the centrifugal compressor (centrifugal compressor 21). The constituent elements already described with reference to FIG. 1A have substantially the same functions, and therefore, a duplicate description thereof will be omitted. Here, only portions having different configurations will be described.

  First, in the modification of FIG. 6, unlike FIG. 1A, the diffuser 11 a and the return guide vane 12 are not provided separately in the communication path 8, and an integrated diffuser 11 c is used. With such a configuration, it is possible to reduce the number of manufacturing steps and the number of parts, and to reduce the manufacturing cost, compared to the case where the diffuser 11a and the return guide vane 12 are individually provided. Moreover, it becomes possible to raise the rigidity of the diffuser 11c by making both continuous.

  Further, in the structure of FIG. 6, the upstream compressor impeller 5 is configured such that the radially outermost diameter on the output side of the downstream impeller body 6a of the downstream compressor impeller 6 is smaller than the radially outermost diameter of the downstream blade 6b. In addition, the downstream compressor impeller 6 can be all set to be equal to or smaller than the radially outermost diameter of the downstream blade 6b, and the external appearance size can be reduced, and the compressor impeller can be easily incorporated as in the centrifugal compressor 1 of FIG.

  As described above, in the centrifugal compressors 1 and 21 of this embodiment, it is possible to increase the specific speed and improve the compression efficiency while simplifying the incorporation of the compressor impeller.

  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 this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above-described embodiment, the plurality of stages of the centrifugal compressors 1 and 21 are configured by the centrifugal compressor + centrifugal compressor. That is, an axial flow compressor + centrifugal compressor or a mixed flow compressor + centrifugal compressor may be used.

  INDUSTRIAL APPLICABILITY The present invention can be used for a centrifugal compressor that boosts gas by the action of centrifugal force.

1, 21 ... Centrifugal compressor 2 ... Compressor housing 4 ... Shaft (rotating shaft)
5 ... upstream compressor impeller 5a ... upstream impeller body 5b ... upstream blade 6 ... downstream compressor impeller 6a ... downstream impeller body 6b ... downstream blades 11a, 11b, 11c ... diffuser 12 ... return guide vane 13 ... labyrinth seal

Claims (8)

A rotation axis;
An upstream compressor impeller having an upstream impeller body fixed to the rotating shaft, and a plurality of upstream blades arranged at intervals in the circumferential direction of the upstream impeller body;
Formed integrally with the upstream compressor impeller in the axial direction of the rotary shaft, or formed separately from the upstream compressor impeller and connected to the upstream compressor impeller in the axial direction of the rotary shaft, A downstream compressor impeller having a downstream impeller body fixed to the rotation shaft, and a plurality of downstream blades arranged at intervals in the circumferential direction of the downstream impeller body;
With
The output-side outermost diameter of the upstream compressor impeller is equal to or smaller than the input-side outermost diameter of the downstream compressor impeller,
The centrifugal compressor having an input-side outermost diameter of the plurality of downstream blades smaller than an output-side outermost diameter of the plurality of upstream blades. A communication path communicating the output side of the upstream compressor impeller and the input side of the downstream compressor impeller;
A diffuser which is provided in the communication path and is located on the radially outer side on the output side of the upstream compressor impeller;
The centrifugal compressor according to claim 1, further comprising: A communication path communicating the output side of the upstream compressor impeller and the input side of the downstream compressor impeller;
A return guide vane located radially outside on the input side of the downstream compressor impeller;
The centrifugal compressor according to claim 1 or 2, further comprising: A compressor housing that houses the upstream compressor impeller and the downstream compressor impeller;
A labyrinth seal provided at a boundary between the upstream impeller body and the compressor housing;
The centrifugal compressor according to claim 1, further comprising: A shaft,
An upstream compressor impeller provided on the shaft;
Provided on the shaft and integrally formed with the upstream compressor impeller in the axial direction of the shaft, or formed separately from the upstream compressor impeller and connected in the axial direction of the upstream compressor impeller and the shaft A downstream compressor impeller,
With
The upstream compressor impeller includes a plurality of upstream blades arranged at intervals in the circumferential direction of the main body,
The downstream compressor impeller includes a plurality of downstream blades arranged at intervals in the circumferential direction of the main body,
A centrifugal compressor in which an output-side outermost diameter of the upstream-side compressor impeller is equal to or smaller than an input-side outermost diameter of the downstream-side compressor impeller. Before Symbol input innermost of the plurality of downstream blades, centrifugal compressor according to the output side outermost diameter smaller claim 5 of said plurality of upstream blade. A communication path communicating the output side of the upstream compressor impeller and the input side of the downstream compressor impeller;
A diffuser which is provided in the communication path and is located on the radially outer side on the output side of the upstream compressor impeller;
The centrifugal compressor according to claim 5, further comprising: A communication path communicating the output side of the upstream compressor impeller and the input side of the downstream compressor impeller;
A return guide vane located radially outside on the input side of the downstream compressor impeller;
The centrifugal compressor according to claim 5, further comprising:

Images