KR102545557B1 - Centrifugal Compressor - Google Patents

Abstract

The centrifugal compressor includes a motor having a rotating shaft; a first volute casing in which a first inlet and a first volute are formed and a gas chamber separated from the first volute and the first inlet, respectively; a first impeller connected to one side of the rotating shaft and rotatably accommodated in the first volute casing; A vaneless diffuser forming a diffuser passage after the outlet of the first impeller; a second volute casing having a second inlet into which the fluid flowing from the first volute flows, and having a second volute and an outlet formed therein; It includes a second impeller connected to the other side of the rotating shaft and rotatably accommodated in the second volute casing, and a gas control passage communicating the gas chamber and the diffuser passage is formed in at least one of the first volute casing and the vaneless diffuser, , The gas outlet of the gas control passage is directed to a region from an intermediate position between the front end of the diffuser passage and the rear end of the diffuser passage to the rear end of the diffuser passage.

Description

Centrifugal Compressor

The present invention relates to a compressor for compressing fluid, and more particularly, to a centrifugal compressor for compressing gas using centrifugal force.

A centrifugal compressor is a device that rotates an impeller in a casing to compress gas with the centrifugal force.

The centrifugal compressor may be configured to compress gas such as refrigerant gas. When the driving force of the motor is transmitted to the impeller and the impeller rotates, the gas is introduced into the impeller by the rotational force of the impeller, and the gas is moved by the impeller. As it flows, the kinetic energy increases, and the gas with the increased kinetic energy passes through the diffuser, converting the kinetic energy into static pressure and increasing the pressure. The pressure-increased gas sequentially passes through the volute and the discharge port communicating with the volute, and is then discharged to the outside of the centrifugal compressor.

A diffuser converts the kinetic energy of gas into a static pressure. One example of the diffuser may be a vaneless diffuser in which the cross-sectional area of a passage through which the gas passes is gradually reduced in the direction of gas flow, and another example of the diffuser is a diffuser in which the gas passes through. It may be a vane diffuser in which a cross-sectional area of a flow passage is formed gradually smaller in a gas flow direction and a plurality of vanes are installed in the flow passage.

The centrifugal compressor can be configured such that its capacity is adjustable, and an example of a centrifugal compressor capable of adjusting the capacity is disclosed in US Patent Publication No. 9,157,446 B2 (October 13, 2015). Such a centrifugal compressor includes a first impeller provided in the main refrigerant passage, a vane diffuser disposed downstream of the first impeller and having a plurality of vanes, a second impeller provided in the main refrigerant passage downstream of the first impeller, and a second impeller. It includes a refrigerant circulation passage connecting the downstream side and the downstream side of the first impeller, and the refrigerant circulation passage includes a plurality of circulation nozzles for spraying refrigerant, and the outlet of the plurality of circulation nozzles is at least partially disposed outside the leading edge of the vane in a radial direction. .

US Registered Patent Publication US9,157,446 B2 (October 13, 2015)

An object of the present invention is to provide a centrifugal compressor capable of adjusting capacity while minimizing a pressure loss coefficient and maximizing efficiency by injecting gas to an optimal position of a vaneless diffuser.

A centrifugal compressor according to an embodiment of the present invention includes a motor having a rotating shaft; a first volute casing in which a first inlet and a first volute are formed and a gas chamber separated from the first volute and the first inlet, respectively; a first impeller connected to one side of the rotating shaft and rotatably accommodated in the first volute casing; A vaneless diffuser forming a diffuser passage after the outlet of the first impeller; a second volute casing having a second inlet into which the fluid flowing from the first volute flows, and having a second volute and an outlet formed therein; It includes a second impeller connected to the other side of the rotating shaft and rotatably accommodated in the second volute casing, and a gas control passage communicating the gas chamber and the diffuser passage is formed in at least one of the first volute casing and the vaneless diffuser, , The gas outlet of the gas control passage may be directed to a region from an intermediate position between a front end of the diffuser passage and a rear end of the diffuser passage to a rear end of the diffuser passage.

The gas outlet may be closer to a rear end of the diffuser passage among a front end of the diffuser passage and a rear end of the diffuser passage.

The gas outlet may face an area ranging from 50% to 75% of a distance from the front end of the diffuser passage to the rear end of the diffuser passage based on the front end of the diffuser passage.

The gas outlet may face a position that is 50% or 75% of the distance from the front end of the diffuser passage to the rear end of the diffuser passage based on the front end of the diffuser passage.

The gas control passage may include a gradient path that is obliquely inclined with respect to the axial center of the first impeller and includes a gas outlet. The gradient may have an acute angle of inclination with the diffuser passage. The inclination angle may be between 30° and 80°.

The gas control passage may further include a communication passage connecting the gas chamber and the gradient passage and parallel to the shaft center.

A cross-sectional area of the gas chamber may be smaller than that of the first volute and larger than that of the gas outlet.

According to an embodiment of the present invention, the gas in the gas control passage can be injected to a position where the pressure loss coefficient can be minimized and efficiency can be maximized.

In addition, since the gas passing through the gradient of the gas control passage is obliquely injected into the diffuser passage, flow resistance when the gas is injected into the diffuser passage can be minimized.

1 is a diagram showing a refrigerating cycle apparatus to which a centrifugal compressor according to an embodiment of the present invention is applied;
2 is a cross-sectional view of a centrifugal compressor according to an embodiment of the present invention;
3 is an enlarged cross-sectional view of section A shown in FIG. 2;
4 is a side view showing a comparative example of a diffuser according to an embodiment of the present invention;
5 is a side view showing an example of a diffuser according to an embodiment of the present invention;
6 is a side view showing another example of a diffuser according to an embodiment of the present invention;
7 is a side view showing another example of a diffuser according to an embodiment of the present invention;
8 is a graph showing a comparison of pressure loss coefficients of Examples of the present invention and Comparative Examples;
Figure 9 is a graph showing the comparison of the efficiency of the embodiment of the present invention and the comparative example.

Hereinafter, specific embodiments of the present invention will be described in detail with drawings.

1 is a view showing a refrigerating cycle device to which a centrifugal compressor according to an embodiment of the present invention is applied, FIG. 2 is a cross-sectional view showing a centrifugal compressor according to an embodiment of the present invention, and FIG. 3 is A shown in FIG. This is an enlarged cross section.

As shown in FIG. 1, the centrifugal compressor 1 of this embodiment may constitute a refrigerating cycle device together with the condenser 2, the expansion mechanism 3, and the evaporator 4, and the centrifugal compressor 1 compresses the After the refrigerant discharged from the centrifugal compressor 1 passes through the condenser 2, the expansion mechanism 3, and the evaporator 4 sequentially, it may be sucked into the centrifugal compressor 1.

The centrifugal compressor 1 may be connected to the evaporator 4 and the suction passage 5, and may be connected to the condenser 2 and the discharge passage 6.

The centrifugal compressor 1 may be composed of a multi-stage compression type centrifugal compressor capable of compressing refrigerant in multiple stages. In this case, the centrifugal compressor 1 includes a plurality of compression mechanisms C1 connected by a connection passage C3 (see FIG. 2). (C2) may be included.

The centrifugal compressor 1 compresses the refrigerant in the first compression mechanism C1, which is one of the plurality of compression mechanisms C1 and C2, and then discharges the refrigerant to the connection passage C3, and the connection passage C3 The refrigerant discharged into the plurality of compression mechanisms (C1) (C2) can be introduced into the second compression mechanism (C2), which is the other one, and compressed, and the refrigerant compressed in the second compressor (C2) is discharged through the discharge passage (6). It can flow to the condenser (2) through.

The refrigerating cycle device having the centrifugal compressor (1) as described above has a bypass passage (7, see FIG. 1) for bypassing some of the refrigerant compressed in the second compression mechanism (C2) to the first compression mechanism (C2). It may further include, and the capacity of the centrifugal compressor 1 is adjusted by the amount of refrigerant flowing into the first compression mechanism C2 through the bypass passage 7 after being discharged from the second compression mechanism C2. can

At least a part of the bypass passage 7 may be formed by a tube positioned outside the centrifugal compressor 1 .

As shown in FIG. 1, the bypass passage 7 may have an inlet end 7A connected to at least one of the second compression mechanism C2, the discharge passage 6, and the condenser 2, and the first It may have an outlet end 7B connected to the compression mechanism C1.

The inlet end 7A can be connected to a plurality of the second compression mechanism C2, the discharge passage 6, and the condenser 2, and the second compression mechanism C2, the discharge passage 6, and the condenser 2 ) can be connected to only one of them.

When the inlet end 7A is connected to the second compression mechanism C2, the inlet end 7A may be connected to the outlet 52 (see FIG. 2) or the second volute V2 of the second compression mechanism C2. there is. And, the outlet end (7B) may be connected to the first volute casing 20 to be described later of the first compression mechanism (C1).

At least a part of the bypass passage 7 is located outside the centrifugal compressor 1, has an inlet end 7A connected to the second compression mechanism C2 and an outlet end 7B connected to the first compression mechanism C1. It may be formed by a tube.

The centrifugal compressor 1 is not limited to the one in which the bypass passage 7 has the inlet end 7A and the outlet end 7B as described above, and the bypass passage 7 is the inside of the centrifugal compressor 1 ( For example, it is also possible to be formed in the motor housing 12, of course.

On the other hand, a flow controller (8, see FIG. 1) for controlling the flow rate of gas passing through the bypass channel 7 may be disposed in the bypass channel 7, and the flow controller 8 can adjust its opening. It may consist of a valve or the like. When the opening of the flow regulator 8 is increased, the flow rate of the gas compressed in the second compression mechanism C2 and injected into the first compression mechanism C1 through the bypass passage 7 may increase. Conversely, when the opening degree of the flow regulator 8 is reduced, the flow rate of the gas compressed in the second compression mechanism C2 and then injected into the first compression mechanism C1 through the bypass passage 7 may decrease. .

Hereinafter, the centrifugal compressor 1 will be described in detail with reference to FIGS. 2 and 3.

The centrifugal compressor 1 includes a motor 10, a first volute casing 20, a first impeller 30, a vaneless diffuser 40, a second volute casing 50, and a second impeller (60).

The motor 10 may have a rotating shaft 11 . One side of the rotating shaft 11 may extend into the first volute casing 20 , and the other side of the rotating shaft 11 may extend into the second volute casing 50 .

The motor 10 may include a motor housing 12 having a space therein. The motor housing 12 may be formed long in the axial direction of the rotation shaft 11 .

The motor 10 may further include a rotor 13 and a stator 14 accommodated inside the motor housing 12 . The rotor 13 may be disposed on the outer circumference of the rotation shaft 11 and may rotate together with the rotation shaft 11 . The stator 14 may be disposed inside the motor housing 14 to surround the outer circumference of the rotor 13 .

A connection passage C3 may be formed in the motor housing 12 . One end of the connection passage C3 may face the first volute casing 20 , and the other end of the connection passage C3 may face the second volute casing 50 . The connection passage C3 may communicate the outlet 22 of the first volute casing 20 with the inlet 51 of the second volute casing 50 . The gas exiting the first volute V1 of the first volute casing 20 sequentially passes through the outlet 22 of the first volute casing 20 and the connection passage C3 formed in the motor housing 12. After passing through, it may flow into the inlet 51 of the second volute casing 50.

The first volute casing 20 may be fastened to the motor housing 12 with a fastening member such as a screw, and a first impeller accommodating space in which the first impeller 30 may be accommodated may be formed therein. . The first impeller accommodating space may communicate with the first inlet 21 and may be a space larger than the first inlet 21 .

In the first volute casing 20, a first inlet 21 and a first volute V1 are formed and a gas chamber S partitioned from each of the first inlet 21 and the first volute V1 is formed. can be formed

The first volute casing 20 may have a hollow shape. An inner circumferential surface of the first volute casing 20 may form an inlet 21 guiding gas to the first impeller 20 . The first volute V1 and the gas chamber S may be formed between an inner circumferential surface and an outer circumferential surface of the first volute casing 20 .

The first volute V1 may be formed in a circular shape or an arc shape, and may be formed in a shape gradually expanding in a gas flow direction (ie, a gas turning direction).

The gas chamber (S) may be formed spaced apart from the first volute (V1) between the inner circumferential surface and the outer circumferential surface of the first volute casing (20). A distance between the gas chamber S and the inlet 21 may be shorter than a distance between the first volute V1 and the inlet 21 . The gas chamber (S) may be formed in a circular shape or an arc shape.

A gas control passage P may be connected to the gas chamber S, and gas in the gas chamber S may be injected into the diffuser passage D1 of the vaneless diffuser 40 through the gas control passage P. .

The centrifugal compressor 1 may include a plurality of gas control passages P connected to the gas chamber S, and the gas in the gas chamber S passes through the plurality of gas control passages P to the plurality of diffuser passages D1. It can be sprayed while distributing to a location. (See FIGS. 5 to 7)

Each gas control passage (P) may include a gas outlet (T) for guiding gas to the diffuser passage (D1), and the gas control passage (P) communicates with the diffuser passage (D1) by the gas outlet (T). It can be.

In the centrifugal compressor, gas in one gas chamber (S) may be injected into the diffuser passage (D1) through a plurality of gas outlets (T). The cross-sectional area of the gas chamber (S) may be smaller than the cross-sectional area of the first volute (V1), and may be larger than the cross-sectional area of the gas outlet (T).

Here, each of the cross-sectional area of the gas chamber (S), the cross-sectional area of the first volute (V1), and the cross-sectional area of the gas outlet (T) may be a cross-sectional area in a direction perpendicular to the axial direction (ie, radial direction).

An outlet 22 through which gas of the first volute V1 passes to exit the first volute casing 20 may be formed in the first volute casing 20 . One end of the outlet 22 formed in the first volute casing 20 may be connected to the first volute V1, and the other end of the outlet 22 may be connected to the connection passage C3.

On the other hand, in the first volute casing 20, a bypass connection passage 29 communicating the outlet end 7B of the bypass passage 7 (see FIG. 1) and the gas chamber S (see FIGS. 2 and 3) can be formed. Some of the gas discharged from the second volute casing 50 may flow into the gas chamber S after sequentially passing through the bypass passage 7 and the bypass connection passage 29, and the gas chamber S ) After spreading widely, it can be dispersed into a plurality of gas control passages (P).

The first impeller 30 may be connected to one side of the rotating shaft 11 . The first impeller 30 may be rotatably accommodated in the first volute casing 20 . In the first impeller 30, an inlet 31 through which gas is introduced may face an axial direction of the rotating shaft 11, an outlet 32 through which gas is taken out may face a radial direction of the rotating shaft 11, and gas can be sucked in the axial direction and discharged in the centrifugal direction. The first impeller 30 may be rotatably accommodated in a first impeller accommodating space formed between a diffuser body 41 of the vaneless diffuser 40 and the first volute casing 20 .

The vaneless diffuser 40 may form a diffuser passage D1 after the outlet 32 of the first impeller 30 . The diffuser passage (D1) may be a communication passage for communicating the first impeller accommodating space and the first volute (V1) in which the first impeller (30) is accommodated, and extends from the outlet (32) of the first impeller (30). It can be defined as a passage located between 1 volute (V1).

The diffuser passage D1 may have a hollow annular shape as a whole and may be long in a radial direction perpendicular to the axial direction C.

The vaneless diffuser 40 may be disposed between the motor 10 and the first volute casing 20 . A rotary shaft through-hole through which the rotary shaft 11 passes may be formed in the vaneless diffuser 40 . A part of the vaneless diffuser 40 may be disposed between the motor 10 and the first impeller 30, and the vaneless diffuser 40 includes a first impeller accommodating space in which the first impeller 30 is accommodated and a rotor. (13) and the space of the motor 10 in which the stator 13 is accommodated can be partitioned.

The vaneless diffuser 40 may be formed by a plurality of members. The vaneless diffuser 40 may include a diffuser body 41 .

The diffuser body 41 may have an inner area A facing the first impeller 30 and an outer area B surrounding the inner area A and not facing the first impeller 30 .

The vaneless diffuser 40 may further include a diffuser cover 46 . The diffuser cover 46 may be disposed on the first volute casing 20 toward the outer region B. The gas exiting the outlet 32 of the first impeller 30 may pass between the outer area B of the diffuser body 41 and the diffuser cover 46, and the first volute in the diffuser passage D1 (V1).

In the centrifugal compressor, at least one of the first volute casing 20 and the vaneless diffuser 40 may have a gas control passage P communicating the gas chamber S with the diffuser passage D1.

A plurality of gas control passages P may be spaced apart in a circumferential direction.

The gas control passage (P) may include a gradient path (P1) inclined obliquely with respect to the axial center (C) of the first impeller (30), the gradient path (P1) may include a gas outlet (T) can The gas passing through the gradient passage P1 may be injected into the diffuser passage D1 after passing through the gas outlet T.

The gradient passage P1 may be formed to have an acute inclination angle θ with the diffuser passage D1. The gradient path P1 may be inclined to have an inclination angle θ of 30° to 80°.

The gas control passage P may further include a communication passage P2 connecting the gas chamber S and the gradient passage P1. The communication passage (P2) may be formed long in a direction parallel to the axis center (C).

The first volute casing 20, the first impeller 30, and the vaneless diffuser 40 may form a first compression mechanism C1 that primarily compresses the refrigerant introduced into the centrifugal compressor 1. there is.

The second volute casing 50 may have a second inlet 51 into which the fluid flowing from the first volute V1 flows. The second volute casing 50 may include a second volute V2 and an outlet 52 .

The second volute casing 50 may be disposed on the opposite side of the first volute casing 50 . The second volute casing 50 may be fastened to the motor housing 12 with a fastening member such as a screw, and a second impeller accommodating space in which the second impeller 60 may be accommodated may be formed therein. .

The second impeller accommodating space may communicate with the second inlet 51 .

A diffuser passage D2 is formed between the second volute casing 50 and the motor housing 12 to guide the gas flowing from the outlet 62 of the second impeller 60 to the second volute V2. It can be. The diffuser passage D2 formed between the second volute casing 50 and the motor housing 12 includes the second impeller accommodation space formed between the second volute casing 50 and the motor housing 12 and the second ball. It may be positioned between the lutes (V2), and the gas exiting the outlet 62 of the second impeller 60 may be guided to the second volute (V2).

The second volute V2 may be formed in a circular shape or an arc shape, and may be formed in a shape gradually expanding in the flow direction of gas.

The outlet 52 of the second volute casing 50 may be formed to be in communication with the second volute V2, and discharge the gas flowing in the second volute V2 to the outside of the centrifugal compressor 1. can guide you

The second impeller 60 may be connected to the other side of the rotating shaft 11 . The second impeller 60 may be rotatably accommodated in the second volute casing 50 . In the second impeller 60, an inlet 61 through which gas is introduced may face an axial direction of the rotating shaft 11, an outlet 62 through which gas is taken out may face a radial direction of the rotating shaft 11, and gas can be sucked in the axial direction and discharged in the centrifugal direction. The second impeller 60 may be rotatably accommodated in the second impeller accommodating space formed between the second volute casing 50 and the motor housing 12 .

The second volute casing 50 and the second impeller 60 are compressed in the first compression mechanism C1 and then second compression mechanism C2 for secondarily compressing the refrigerant introduced through the connection passage C3 can be configured.

On the other hand, in the centrifugal compressor 1 configured as described above, the pressure loss depends on the position where the gas control passage P injects gas into the diffuser passage D1, that is, the position of the gas outlet T of the gas control passage P. The coefficient of pressure loss and efficiency may be different, and the gas outlet T of the gas control passage is preferably formed at a position capable of maximizing efficiency while minimizing the pressure loss coefficient.

Figure 4 is a side view showing a comparative example of a diffuser according to an embodiment of the present invention, Figure 5 is a side view showing an example of a diffuser according to an embodiment of the present invention, Figure 6 is a diffuser according to an embodiment of the present invention Another example is a side view shown, and FIG. 7 is a side view showing another example of a diffuser according to an embodiment of the present invention. 8 is a graph showing comparison of pressure loss coefficients of Examples of the present invention and Comparative Examples, and FIG. 9 is a graph showing comparison of efficiencies between Examples of the present invention and Comparative Examples.

As shown in FIG. 4, the gas outlet (T'), which is a comparative example of the gas outlet (T, see FIGS. 5 to 7) of the present embodiment, is connected to the tip (Pa) of the diffuser passage (D1) among the diffuser passages (D1). Directed from the middle position (Pc) between the rear end (Pb) of the diffuser passage (D1) to the front end (Pa) of the diffuser passage (D1), but closer to the front end (Pa) of the diffuser passage (D1) than the middle position (Pc) when it is located close to

The front end (Pa) of the diffuser passage (D1) may be defined as the outlet 32 of the first impeller 30, and the rear end (Pb) of the diffuser passage (D1) is the vaneless diffuser 40, in particular, the diffuser body ( 41) can be defined as the outermost circumference.

On the other hand, as shown in FIGS. 5 to 7, the gas outlet T of this embodiment is between the front end Pa of the diffuser passage D1 and the rear end Pb of the diffuser passage D1. It may be directed to a region from the middle position (Pc) of the diffuser passage (D1) to the rear end (Pb).

The gas outlet (T) of this embodiment extends from the position of the first radius (R1) determined by Equation 1 to the position of the second radius (R2) determined by Equation 2 based on the axis center of the first impeller (30). It is possible to form towards the area.

[Equation 1]

R1= (Rimp + Rdiff)/2

[Equation 2]

R2= (Rimp + 3*Rdiff)/4

Here, Rimp is the radius of the first impeller 30, and Rdiff is the radius of the vaneless diffuser 40.

As shown in FIGS. 6 and 7, the gas outlet T of this embodiment is the rear end of the diffuser passage D1 among the front end Pa of the diffuser passage D1 and the rear end Pb of the diffuser passage D1 ( Pb) may be closer.

As shown in FIGS. 5 and 6, the gas outlet T of the present embodiment is a diffuser passage D1 from the front end Pa of the diffuser passage D1 based on the front end Pa of the diffuser passage D1. A region ranging from 50% to 75% of the distance L to the rear end Pb may be directed.

An example of the gas outlet T of this embodiment may be formed toward a position having a first radius R1 determined by Equation 1 based on the axial center of the first impeller 30 . In this case, as shown in FIG. 5, the gas outlet T is formed from the front end Pa of the diffuser passage D1 to the rear end Pb of the diffuser passage D1 based on the front end Pa of the diffuser passage D1. ) to a location that is 50% of the distance L. That is, in one example of the gas outlet (T), the distance from the front end (Pa) of the diffuser passage (D1) to the gas outlet (T) is the distance from the front end (Pa) of the diffuser passage (D1) to the rear end (Pb) of the diffuser passage (D1). This is a case where it is formed at a position that is 0.5 times the distance (L) to . In this case, the gas outlet T may be formed toward a position having a first radius R1 determined by Equation 1 based on the axial center of the first impeller 30 .

Another example of the gas outlet (T) of this embodiment may be formed toward the position of the second radius (R2) determined by Equation 2 based on the axial center of the first impeller (30). In this case, as shown in FIG. 6, the gas outlet T is formed from the front end Pa of the diffuser passage D1 to the rear end Pb of the diffuser passage D1 based on the front end Pa of the diffuser passage D1. ) to a position that is 75% of the distance L. That is, in another example of the gas outlet (T), the distance from the front end (Pa) of the diffuser passage (D1) to the gas outlet (T) is from the front end (Pa) of the diffuser passage (D1) to the rear end (Pb) of the diffuser passage (D1). ) is formed at a position that is 0.75 times the distance (L).

Another example of the gas outlet T of this embodiment is as shown in FIG. 7, the diffuser passage D1 from the front end Pa of the diffuser passage D1 based on the front end Pa of the diffuser passage D1. Although it is a position exceeding 75% of the distance L to the rear end Pb, it may face a position inside the rear end Pb of the diffuser passage D1. That is, another example of the gas outlet (T) is the distance from the front end (Pa) of the diffuser passage (D1) to the gas outlet (T) from the front end (Pa) of the diffuser passage (D1) to the rear end of the diffuser passage (D1) ( This is a case where it is formed at a position that is more than 0.75 times and less than 1 times the distance (L) to Pb).

In FIGS. 8 and 9 , only the formation positions of the gas outlets T' and T are different, and the pressure loss coefficient and efficiency measured under the same conditions are the results of comparing the other configurations, respectively.

As in the present embodiment, the distance from the front end (Pa) of the diffuser passage (D1) to the gas outlet (T) is the distance from the front end (Pa) of the diffuser passage (D1) to the rear end (Pb) of the diffuser passage (D1) ( In the case of 0.5 times or more and less than 1 time of L), as shown in FIG. 8, the pressure loss coefficient is less than 65%, which is lower than that of the comparative example, and as shown in FIG. 9, the efficiency is greater than 70% in the case of the comparative example. higher than

On the other hand, in the case of the comparative example, the pressure loss coefficient is greater than 65%, higher than that of the inventive example, and the efficiency is less than 70%, lower than that of the inventive example.

Referring to FIGS. 8 and 9, it can be seen that the pressure loss coefficient of this embodiment is lower and the efficiency is higher than that of the comparative example.

The above description is merely an example of the technical idea of the present invention, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain, and the scope of the technical idea of the present invention is not limited by these embodiments.

The protection scope of the present invention should be construed according to the following claims, and all technical ideas within the equivalent range should be construed as being included in the scope of the present invention.

10: motor 11: rotation shaft
20: first volute casing 21: first inlet
30: first impeller 40: vaneless diffuser
50: second volute casing 51: second inlet
52: outlet 60: second impeller
Dl: diffuser passage P: gas control passage
S: gas chamber T: gas outlet
V1: 1st volute V2: 2nd volute

Claims (9)

a motor having a rotating shaft;
a first volute casing in which a first inlet and a first volute are formed and a gas chamber separated from the first volute and the first inlet, respectively;
a first impeller connected to one side of the rotating shaft and rotatably accommodated in the first volute casing;
a vaneless diffuser forming a diffuser passage through which the outlet of the first impeller communicates with the first volute;
a second volute casing having a second inlet into which the fluid flowing from the first volute flows, and having a second volute and an outlet;
a second impeller connected to the other side of the rotating shaft and rotatably accommodated in the second volute casing;
A bypass flow path having an inlet end connected to the outlet or the second volute of the second volute casing and an outlet end connected to the gas chamber of the first volute casing,
A gas control passage communicating the gas chamber and the diffuser passage is formed in at least one of the first volute casing and the vaneless diffuser,
The gas outlet of the gas control passage is directed toward a region from an intermediate position between a front end of the diffuser passage and a rear end of the diffuser passage in the diffuser passage to a rear end of the diffuser passage. According to claim 1,
The gas outlet is closer to the rear end of the diffuser passage among the front end of the diffuser passage and the rear end of the diffuser passage. According to claim 1,
The gas outlet is directed toward an area ranging from 50% to 75% of a distance from the front end of the diffuser passage to the rear end of the diffuser passage based on the front end of the diffuser passage. According to claim 1,
The gas outlet is directed toward a position that is 50% or 75% of a distance from the front end of the diffuser passage to the rear end of the diffuser passage based on the front end of the diffuser passage. According to claim 1,
The gas control passage
A centrifugal compressor comprising a gradient path inclined obliquely with respect to the axial center of the first impeller and including the gas outlet. According to claim 5,
The gradient is a centrifugal compressor having an acute angle of inclination with the diffuser passage. According to claim 6,
The inclination angle is 30 ° to 80 ° centrifugal compressor. According to claim 5,
The gas control passage
A centrifugal compressor further comprising a communication passage connecting the gas chamber and the gradient passage and parallel to the shaft center. According to claim 1,
The cross-sectional area of the gas chamber is smaller than the cross-sectional area of the first volute and larger than the cross-sectional area of the gas outlet.

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