KR20220159795A - Turbo Compressor - Google Patents

Abstract

One objective of the present invention is to provide a turbo compressor having a structure capable of cooling a motor while preventing a decrease in refrigerating performance of a refrigerating cycle. The present invention provides a turbo compressor including: a driving unit capable of generating rotational power for compression of refrigerant; a shaft extending in one direction and rotatably coupled to the driving unit at one side and rotated by the power generated from the driving unit; and first to third compression units including first to third impellers installed on the shaft to receive the rotational power by the shaft, respectively. The first to third impellers are installed to be rotatable on the other side of the shaft so as to be provided on the opposite side to the driving unit.

Description

Turbo Compressor {Turbo Compressor}

The present invention relates to a turbo compressor, and more particularly, to a turbo compressor that can be miniaturized while applying a structure of a three-stage impeller.

In general, compressors are applied to vapor compression type refrigerating cycles (hereinafter, abbreviated as refrigerating cycles) such as refrigerators or air conditioners. The compressor may be classified into a reciprocating type, a rotary type, a scroll type, and the like according to a method of compressing refrigerant.

A reciprocating compressor is a compressor in which a piston in a cylinder compresses gas by reciprocating motion. Among them, a scroll compressor engages a fixed scroll fixed in the inner space of an airtight container to perform a orbital motion, thereby performing a orbital movement with a fixed wrap of the fixed scroll and an orbiting scroll. It is a compressor in which a compression chamber is formed between the orbiting wraps of the

A turbo compressor is a type of centrifugal compressor, which compresses gas with centrifugal force by rotating the impeller wheels of the curved blades in the casing. Turbo compressors have advantages over reciprocating and screw-type compressors such as large capacity, low noise, and low maintenance. In addition, it is possible to produce clean compressed gas that does not contain oil.

A turbo compressor has a relatively low compression ratio and a high flow rate compared to a positive displacement compressor such as a scroll compressor generally applied to a refrigerating cycle device, and a multi-stage turbo compressor to compensate for the low compression ratio of the turbo compressor is known.

A centrifugal turbocompressor consists of an impeller to compress the gas and a diffuser to decelerate the accelerated gas flow and convert it to pressure. When the motor rotates the impeller at high speed, external gas is sucked in along the axial direction of the impeller, and the sucked gas is discharged in the centrifugal direction of the impeller. The fluid discharged in the centrifugal direction of the impeller is compressed while moving along a flow path formed inside the turbo compressor.

FIG. 1 is a cross-sectional view showing a turbo compressor 2 of the counter type of the conventional patent document 1. As shown in FIG.

1 of Patent Document 1 discloses a turbo compressor 2, in which an impeller is installed on the left end of the rotating shafts 4 and 7, and a turbo compressor of an example in which a drive unit 38 is also provided on the right side of the casing 3 is shown.

In addition, Patent Document 1 discloses a counter-type turbo compressor among two-stage turbo compressors. In the counter-type turbo compressor, first and second-stage impellers are arranged to face each other on both sides of the motor with the motor as the center. In this structure, both the impeller and the journal bearing that apply the load to the shaft are symmetrically arranged to take a mechanically stable structure.

As a method for cooling the motor of the counter-type turbo compressor, liquid refrigerant at a cold temperature is injected into the motor unit. Its advantage is that it can quickly and reliably lower the temperature of the motor. However, there is a disadvantage in that the refrigerant performance of the entire refrigeration cycle may be partially reduced by partially bypassing the refrigerant of the refrigeration cycle and using it for motor cooling.

On the other hand, in order to achieve a higher compression ratio, the turbo compressor should be designed with three stages. The two-stage turbo compressor should be designed so that the thrust applied to each is offset by arranging two impellers facing in opposite directions, but the three-stage impeller must be divided into two and one, so In this case, there is a problem that the thrust is not offset.

In particular, in the case of a three-stage turbo compressor, the length of the shaft becomes longer as more than one impeller is disposed compared to the two-stage turbo compressor, and the impeller must be disposed at one end of the shaft, resulting in reliability problems or aerodynamic efficiency degradation due to impeller gaps. Problems can arise.

Therefore, it is required to develop a turbo compressor capable of preventing a problem of reliability or a problem of deterioration in aerodynamic efficiency due to a gap between impellers while applying a three-stage impeller.

International Publication Patent WO 2018/162660 (2018.9.13)

The present invention has been made to solve the above problems, and one object of the present invention is to provide a turbo compressor having a structure capable of cooling a motor while preventing a decrease in refrigerating performance of a refrigerating cycle.

Another object of the present invention is to provide a turbo compressor capable of preventing a reliability problem or a decrease in aerodynamic efficiency due to an impeller gap while applying a three-stage impeller.

Another object of the present invention is to provide a turbo compressor having a structure that can be miniaturized while providing a high compression ratio while applying a three-stage impeller.

In order to solve the above problems, the turbo compressor of the present invention, a driving unit capable of generating rotational power for compression of the refrigerant; a shaft extending in one direction and rotatably coupled to the drive unit at one side and rotated by power generated from the drive unit; and first to third compression units including first to third impellers installed on the shaft to receive rotational force by the shaft, wherein the first to third impellers are on opposite sides of the drive unit. It is installed to be rotatable on the other side of the shaft so as to be provided.

According to an example related to the present invention, the first impeller is disposed so that one side faces the drive unit, the second impeller is disposed to face the same direction as the first impeller, and the third impeller Is arranged to face a different direction from the first impeller.

The driving unit is provided with a refrigerant suction passage formed to allow the first impeller to suck the refrigerant discharged from the evaporator and introduced into the compressor, and the first compression unit accommodates the first impeller, and the first compression unit accommodates the first impeller. It further includes a first impeller housing having a first inlet through which refrigerant flows into one side of the impeller, and one side of the first impeller is disposed toward the drive unit so that the refrigerant suction passage and the first inlet communicate with each other. It can be.

Preferably, the second compression unit further includes a second impeller housing accommodating the second impeller and having a second inlet through which refrigerant flows into one side of the second impeller, wherein the second impeller , The second inlet may be disposed in the same direction as the first impeller so that the refrigerant discharged from the first impeller can be introduced.

The third compression unit may further include a third impeller housing accommodating the third impeller and having a third inlet through which refrigerant flows into one side of the third impeller.

According to another example related to the present invention, the drive unit includes a stator fixedly coupled to an inner circumferential surface of the casing; And a rotor located inside the stator and coupled to the shaft to an inner circumference to enable rotation of the shaft by a rotational force generated by interaction with the stator, wherein the refrigerant inlet passage is generated in the stator It may be provided along at least one direction in the stator so as to be able to cool the heat.

The thrust applied to the third impeller may be 1.3 to 1.5 times higher than the thrust applied to the first or second impeller.

In addition, the thrust of the first impeller is, [Equation 1] can be defined as

[Equation 1]

F ₁ = (P ₂ - P ₁ ) * A _i1 + (P ₂ - P _1.5 ) * A _o1

In [Equation 1], F ₁ is the thrust of the first impeller, P ₁ is the pressure on the suction side of the first impeller, P _1.5 is the pressure on the wing side of the first impeller, and P ₂ is the pressure applied to the rear surface of the first impeller The pressure, A _i1 , is the area of the first impeller at the suction side, and A _o1 is the cross-sectional area in the radial direction at the wing side of the first impeller at the discharge port.

The thrust of the second impeller may be defined by [Equation 2].

[Equation 2]

F ₂ = [(P _3.5 - P ₂ ) * A _i2 + (P _3.5 - P _2.5 ) * A _o2 ]

In [Equation 2], F ₂ is the thrust of the second impeller, P ₂ is the pressure on the suction side of the second impeller, P _2.5 is the pressure on the wing side of the second impeller, P ₃ is the pressure on the suction side of the second impeller, P _3.5 is the pressure applied to the rear surface of the second impeller, A _i2 is the area of the second impeller on the suction side, and A _o2 is the cross-sectional area in the radial direction from the wing side of the second impeller.

The thrust of the third impeller can be defined as [Equation 3].

[Equation 3]

F ₃ = -(P ₄ - P _3.5 ) * A _o3 - (P ₄ - P ₃ ) * A _i3 + P ₃ * A _s ]

In [Equation 3], F ₃ is the thrust of the third impeller, P ₃ is the pressure at the suction side of the second impeller, P _3.5 is the pressure applied to the rear surface of the second impeller, and P ₄ is the pressure at the rear surface of the third impeller. The pressure, A _i3 is the area of the third impeller at the suction side, A _o3 is the cross-sectional area in the radial direction from the wing side of the third impeller at the discharge port, and _As is the cross-sectional area of the shaft.

According to another example related to the present invention, the turbo compressor of the present invention further includes a bearing part installed on the shaft to support a load applied to the shaft, and the bearing part is installed to surround an outer circumference of the shaft to Journal bearings supporting loads in the radial direction of the shaft; and a thrust bearing connected to the shaft to support a load in the one direction so as to be disposed in a direction crossing the one direction.

In addition, the distance between both ends of the journal bearing and the positions where the first to third impellers are disposed can be derived by [Equation 5].

[Equation 5]

ε _seal = ls * tan(2ε/lb)

In [Equation 5], ε _seal is the gap between the inner circumference of the journal bearing and the outer circumference of the shaft, ls is the maximum distance in the axial direction between the adjacent impeller and the journal bearing, and ε is the gap between the inner circumference of the impeller and the outer circumference of the shaft. , lb is the axial distance between the two journal bearings.

In the turbocompressor of the present invention, the first to third impellers are disposed on one side of the motor so that the refrigerant sucked into the impeller cools the motor while passing through the motor and can be sucked into the impeller.

In addition, since the turbocompressor of the present invention does not require an additional injection line, unlike the counter-type turbocompressor, the disadvantage that the injection can be cooled is eliminated.

In addition, since the turbocompressor of the present invention uses a gaseous suction refrigerant instead of a cold liquid refrigerant, it is possible to prevent a decrease in efficiency or a reliability problem of the aerodynamic unit due to the inflow of liquid refrigerant.

1 is a cross-sectional view showing a conventional counter-type turbo compressor.
2 is a cross-sectional view showing a turbo compressor of the present invention.
3 is a conceptual diagram showing a refrigerant intake path of a turbo compressor according to the present invention;
Figure 4 is a conceptual diagram showing the thrust applied to the impeller.
5 is a conceptual diagram showing the pressure for each position in each of the first to third impellers and showing the cross-sectional area of the shaft and the impeller.

In this specification, the same or similar reference numerals are given to the same or similar components even in different embodiments, and overlapping descriptions thereof will be omitted.

In addition, a structure applied to one embodiment may be equally applied to another embodiment as long as there is no structural or functional contradiction between different embodiments.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In describing the embodiments disclosed in this specification, if it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in this specification, the detailed descriptions thereof will be omitted.

The accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea disclosed in this specification is not limited by the accompanying drawings, and all changes and equivalents included in the spirit and technical scope of the present invention are included. It should be understood to include water or substitutes.

The turbo compressor 100 of the present invention includes a driving unit 120, a shaft 125, and first to third compression units 130, 140, and 180.

The drive unit 120 can generate rotational power for compression of the refrigerant.

The shaft 125 extends in one direction, and is rotatably coupled to the drive unit 120 at one side and rotated by power generated from the drive unit 120 . The shaft 125 may be a rotational shaft that enables rotation of the first to third impellers 131, 141, and 181 to be described later.

The first to third compression units 130, 140, and 180 include first to third impellers 131, 141, and 181 installed on the shaft 125 to receive rotational force by the shaft 125, respectively. .

In addition, the first to third impellers 131 , 141 , and 181 are installed to be rotatable on the other side of the shaft 125 so as to be provided on the opposite side to the drive unit 120 .

The turbo compressor 100 of the present invention can perform multi-stage compression by means of the first to third impellers 131, 141, and 181.

2 is a cross-sectional view of the turbo compressor 100 of the present invention. 3 shows a refrigerant intake path of the turbo compressor 100 of the present invention.

First, the structure of the turbo compressor 100 according to the present invention will be described in detail with reference to FIGS. 2 and 3 .

As shown in FIG. 2, in the turbo compressor 100 according to the present invention, the drive unit 120 is installed in the inner space of the casing 110, and the first compression unit 130 is installed outside the casing 110. , The second compression unit 140 and the third compression unit 180 are installed, and a shaft 125 is connected between the drive unit 120 and the compression units 130, 140, and 180.

The casing 110 may include a shell 111 having a cylindrical shape with both ends open, and a front frame 112 and a rear frame 113 covering both open ends of the shell 111, respectively.

A stator 121 of a driving unit 120 to be described later is fixedly coupled to the inner circumferential surface of the shell 111, and a shaft 125 to be described later passes through the center of the front frame 112 and the rear frame 113. Holes 112a and 113a are formed, respectively, and the hole 112a of the front frame 112 and the hole 113a of the rear frame 113 are journal bearings for radially supporting the shaft 125 ( journal bearing, 151, 152) can be installed respectively.

The journal bearings 151 and 152 may also be radial bearings.

In addition, a first thrust bearing 153 is coupled to the inner surface of the front frame 112 and a second thrust bearing 154 is coupled to the inner surface of the rear frame 113, respectively, and a shaft 125 to be described later. ), the first axial support plate (thrust runner, 161) and the second axial support plate (thrust runner, 162) may be fixedly coupled to face the first thrust bearing 153 and the second thrust bearing 154, respectively. have. That is, the first thrust bearing 153 together with the first axial support plate 161 forms a first direction thrust limiter, and the second thrust bearing 154 together with the second axial support plate (thrust runner 162) A second direction thrust limiting portion is formed. Thus, the first direction thrust limiting unit and the second direction thrust limiting unit cancel thrust on the rotating element including the shaft 125 while forming thrust bearings in opposite directions.

Meanwhile, the driving unit 120 serves to generate rotational power for compressing the refrigerant. The drive unit 120 may include a stator 121 and a rotor 122, and at the center of the rotor 122, a first impeller 131 and a second impeller 141, which will be described later, provide rotational force of the rotor 122. ) and the shaft 125 for transmission to the third impeller 181 are coupled.

The stator 121 may be fixed by being press-fitted to the inner circumferential surface of the casing 110 or welded to the casing 110 . For example, the outer circumferential surface of the stator 121 is formed to be decut in a D shape, and a passage through which fluid can move may be formed between the inner circumferential surface of the casing 110.

The stator 121 may include a refrigerant inlet passage 121a, and the refrigerant inlet passage 121a may be formed in the stator 121 along at least one direction. The refrigerant inlet passage 121a may be formed inside the stator 121 or may be provided so that the refrigerant flows on the outer circumference of the stator 121 .

2 shows an example in which the stator 121 is provided with the refrigerant inlet passage 121a in the left-down direction, but is not necessarily limited to this structure.

The rotor 122 is located inside the stator 121 and is spaced apart from the stator 121 . Balance weights may be coupled to both ends of the rotor 122 in the axial direction to offset eccentric loads generated by the first impeller 131 and the second impeller 141, which will be described later. However, the balance weight may be coupled to the shaft 125 without being installed on the rotor 122 .

When the balance weight is coupled to the shaft 125, the first axial support plate 161 and the second axial support plate (thrust runner) 162 may be used as the balance weight.

The shaft 125 is press-fitted through the center of the rotor 122 .

Therefore, the shaft 125 receives the rotational force generated by the interaction between the stator 121 and the rotor 122 and rotates together with the rotor 122, and this rotational force is transmitted to the first impeller 131, which will be described later, The refrigerant is transferred to the second impeller 141 and the third impeller 181 to suck, compress, and discharge the refrigerant.

On the other hand, on both sides of the rotor 122, a first axial support plate 161 and a second axial support plate (thrust runner, 162) are fixedly coupled, respectively, and the first axial support plate 161 and the second axial support plate 162 is axially supported by first and second thrust bearings 153 and 154 provided in the casing 110 .

Accordingly, as described above, the shaft 125 is a first thrust bearing (where the first axial support plate 161 and the second axial support plate 162 provided on the shaft 125 are provided on the casing 110), as described above. 153) and the second thrust bearing 154, while being supported in opposite directions to each other, the thrust generated by the first compression unit 130 and the second compression unit 140 can be effectively offset.

The first axial support plate 161 and the second axial support plate 162 may be integrally provided at both ends of the rotor 122, but in this case, the first axial support plate 161 and the second axial support plate ( Frictional heat generated in the process of 162 supporting the shaft 125 in the axial direction may be transferred to the rotor 122, and when each of the support plates 161 and 162 is deformed under load in the axial direction, the rotor 122 ) can be transformed. Accordingly, it is preferable that the first axial support plate 161 and the second axial support plate 162 are spaced apart from both ends of the rotor 122 .

In addition, when the first axial support plate 161 and the second axial support plate 162 are fixedly coupled to the shaft 125, as described above, the first axial support plate 161 and the second axial support plate 162 ) may be used as a balance weight by adjusting the weight or fixing position. In this case, since there is no need to install a separate balance weight on the rotor 122, not only can the weight of the rotating element be reduced, but also the axial length of the turbo compressor 100 can be reduced, thereby miniaturizing the turbo compressor 100. can

Here, the first thrust bearing 153 and the second thrust bearing 154 are not installed on the front frame 112 and the rear frame 113, but are disposed on the inner side of the casing. The first axial support plate 161 And it may be installed on the second axial support plate (162).

In addition, the inside of the casing 110, that is, between the front frame 112 and the rotor 122 or between the rear frame 113 and the rotor 122 is a separate front side fixed to the casing 110, respectively. A side fixing plate (not shown) and a rear fixing plate (not shown) may be further provided, and the first thrust bearing 153 and the second thrust bearing 154 may be respectively installed on the front fixing plate and the rear fixing plate.

In this case, although the axial length of the turbo compressor 100 may increase and the number of assembly man-hours may increase, reliability may be improved compared to installing a thrust bearing directly on the casing 10.

Here, although not shown in the drawings, the first thrust bearing 153 and the second thrust bearing 154 are gathered on one side of the driving unit 120, that is, on either the front side or the rear side with respect to the stator 121. may be provided.

Meanwhile, as described above, in the present invention, the compression units 130, 140, and 180 may be formed of three compression units 130, 140, and 180 to perform multi-stage compression. In addition, in the present invention, the compression units 130, 140, and 180 are all disposed on opposite sides of the drive unit 120, which may be preferable in terms of high efficiency and miniaturization.

Hereinafter, when three compression units 130, 140, and 180 are provided to compress the refrigerant in multiple stages, the first to third compression units 130, 140, and 180 are divided into first to third compression units 130, 140, and 180 according to the order of compressing the refrigerant. Let's explain.

The first compression unit 130 , the second compression unit 140 , and the third compression unit 180 are continuously installed on one side of the casing 110 along the axial direction.

In addition, each of the impellers (131, 141, 181) of the first compression unit 130, the second compression unit 140, and the third compression unit 180 are each of the impeller housings (132, 142, 182) can be accepted and combined.

That is, in the first compression unit 130, the first impeller 131 is accommodated in the first impeller housing 132 and coupled to the shaft 125, and the second compression unit 140 has a second impeller 141 The second impeller housing 142 is accommodated and coupled to the shaft 125, and in the third compression unit 180, the third impeller 181 is accommodated in the third impeller housing 182 and coupled to the shaft 125. can

However, in some cases, the first impeller 131, the second impeller 141, and the third impeller 181 may be continuously arranged in one impeller housing and coupled to the shaft 125. However, when a plurality of impellers are installed in one impeller housing, the shape of the impeller housing may become considerably complicated.

The first compression unit 130 includes a first inlet 132b through which the refrigerant discharged from the evaporator can be sucked. In addition, the first compression unit 130 may include a first impeller housing 132 capable of accommodating the first impeller 131, the first inlet 132b is, for example, the first impeller housing ( 132) may be formed on one side. 1 shows an example in which the first inlet 132b is formed in a direction parallel to the axis 125 in the first impeller housing 132 near the center of the turbo compressor 100.

A first impeller accommodating space 132a in which the first impeller 131 is accommodated is formed inside the first impeller housing 132, and a suction pipe 115 is connected to one end of the first impeller housing 132 to cycle the refrigeration cycle. A first inlet 132b through which refrigerant is sucked from the evaporator is formed, and at the other end of the first impeller housing 132, a first outlet 132c guides the refrigerant compressed in the first stage to the second impeller housing 142 to be described later. ) is formed.

The first impeller accommodating space 132a may be formed in a closed shape except for the first inlet 132b and the first outlet 132c so as to completely accommodate the first impeller 131, but the first impeller 131 It may be formed in a semi-enclosed shape in which the rear side of the is opened and the open side is sealed to the front side of the second impeller housing 142 to be described later.

Between the first inlet 132b and the first outlet 132c, the first diffuser 133 is formed by being spaced apart from the outer circumferential surface of the wing 131b of the first impeller 131 by a predetermined interval, and the first diffuser 133 The first volute 134 is formed on the downstream side of ). In addition, the first inlet 132b is formed at the center of one end of the first diffuser 133 in the axial direction, and the first outlet 132c is formed at the downstream side of the first volute 134, respectively.

The first impeller 131 includes a first disc portion 131a coupled to the shaft 125 and a plurality of first wing portions 131b formed on the front surface of the first disc portion 131a. The first disc portion 131a has a plurality of first wing portions 131b formed in a conical shape on its front surface, but its rear surface may be formed in a flat plate shape to receive back pressure.

Here, although not shown in the drawing, a first back pressure plate (not shown) coupled to the shaft 125 is provided at the rear of the first disk part 131a at a predetermined interval, and the first back pressure plate has A first sealing member (not shown) having an annular shape may be provided. Accordingly, a first back pressure space (not shown) filled with a predetermined refrigerant may be formed between the front surface of the second impeller housing 142 and the first back pressure plate at the rear of the first disc unit. However, since the pressure of the refrigerant sucked through the first inlet 132b is not so high, the thrust to the shaft 125 may not be large, so the first back pressure space may be excluded.

The second compression unit 140 may have a second outlet 142d that enables the refrigerant discharged from the second impeller 141 to be provided to the third compression unit 180 . For example, as will be described later, the second outlet 142d may be provided in the second impeller housing 142 . In addition, the third compression unit 180 may include an inflow passage 182f communicating with the second outlet 142d. The inflow passage 182f can communicate with the second outlet 142d and allows the refrigerant discharged from the second impeller 141 to flow into the third impeller 181 .

Meanwhile, a second impeller accommodating space 142a in which the second impeller 141 is accommodated is formed inside the second impeller housing 142, and one end of the second impeller housing 142 has a first impeller housing 132 is connected to the first outlet 132c of the second inlet 142b through which the first-stage compressed refrigerant is sucked, and a discharge pipe 116 is connected to the other end of the second impeller housing 142 to form a second-stage compressed refrigerant. A second outlet 142c is formed to guide the refrigerant to the condenser of the refrigerating cycle.

A second diffuser 143 is formed between the second inlet 142b and the second outlet 142c by being spaced apart from the outer circumferential surface of the wing 141b of the second impeller 141 by a predetermined interval, and the second diffuser 143 The second volute 144 is formed on the downstream side of ). In addition, the second inlet 142b is formed at the center of one end of the second diffuser 143 in the axial direction, and the second outlet 142c is formed at the downstream side of the second volute 144, respectively.

The second impeller 141 includes a second disk portion 141a coupled to the shaft 125 and a plurality of second wing portions 141b formed on the front surface of the second disk portion 141a. The second disc portion 141a has a plurality of second wing portions 141b formed in a conical shape on its front surface, but its rear surface may be formed in a flat plate shape to receive back pressure.

Here, a second back pressure plate (not shown) coupled to the shaft 125 is provided at the rear of the second disc portion 141a and is spaced apart by a predetermined interval, and the second back pressure plate has an annular second sealing groove. (not shown) is formed and a second sealing member (not shown) may be inserted into the second sealing groove. Thus, a second back pressure space (not shown) filled with a predetermined refrigerant may be formed between the second back pressure plate and the front surface of the casing 110 at the rear of the second disc portion 141a. And, as a part of the refrigerant flowing into the second back pressure space flows into the second sealing groove and pushes up the second sealing member, the second sealing member comes into close contact with the front surface of the front frame 112 to generate the second back pressure. to seal the space.

The second back pressure space is connected to a back pressure passage to be described later, and the back pressure passage is selectively connected to the back pressure passage so that the pressure in the second back pressure space can be varied according to the operating speed of the compressor (ie, compression ratio). A back pressure regulating valve that opens and closes may be installed.

For example, the back pressure passage may be formed through the inside of the second impeller housing 142 and the casing 110 . That is, a first back pressure passage is formed inside the housing constituting the wall of the second impeller housing 142, and a second back pressure passage communicates with the first back pressure passage inside the front frame 112 of the casing 110. can be formed. Of course, the back pressure flow path may be formed in the form of a pipe branched from the middle of the discharge pipe, but it may be preferable to form the back pressure flow path inside the impeller housing and the front frame to reduce manufacturing cost by reducing the number of parts.

However, in some cases, the back pressure passage may be formed by assembling a separate valve frame equipped with the back pressure passage on the front surface of the casing.

As described above, the first to third impellers 131, 141, and 181 are installed on the shaft 125 and rotated so as to be spaced apart from each other by a predetermined distance on one side of the shaft 125.

When the first to third impellers 131, 141, and 181 rotate, pressure is formed around each impeller, and the pressure acting on each impeller is balanced in the circumferential direction, and their resultant force is axial heading in the direction

As described above, the first to third impellers 131 , 141 , and 181 may be disposed on one side of the shaft 125 . 2 shows an example in which the first to third impellers 131, 141, and 181 are disposed on the left side opposite to the right side where the driving unit 120 is located.

As such, in the present invention, the first to third impellers 131, 141, and 181 disposed on one side of the shaft 125 have a conventional structure in which two impellers are disposed on both sides of the shaft 125, respectively. There is a difference with

In addition, as shown in FIG. 2, the first impeller 131 and the second impeller 141 are disposed facing the same direction, and the third impeller 181 is the first and second impellers 131 and 141 ) and can be arranged in the opposite direction.

As shown in FIG. 2, the first impeller 131 and the second impeller 141 are disposed in the direction in which the refrigerant flows from the right side, and the third impeller 181 includes the first and second impellers 131, 141) is arranged so that the refrigerant discharged from the first and second impellers 131 and 141 flows in from the left direction.

For this reason, after the refrigerant introduced from the right side of FIG. 2 is compressed in the first and second stages, the refrigerant compressed in the first and second stages flows in from the left side and is compressed in the third stage.

As described above, in the turbo compressor 100 of the present invention, the first to third impellers 131, 141, and 181 are all disposed on the opposite side of the driving unit 120. In this way, the first to third impellers 131 , 141, 181) When disposed on the opposite side of the driving unit 120, the refrigerant sucked into the impeller cools the motor while passing through the motor and is sucked into the impeller.

Therefore, since an additional injection passage is not required, the disadvantage of counter-type injection cooling is eliminated. In addition, since a gaseous suction refrigerant is used instead of a cold liquid refrigerant, a decrease in efficiency of the aerodynamic part or a reliability problem due to the inflow of liquid refrigerant does not occur.

Therefore, the method of arranging all of the first to third impellers 131, 141, and 181 on the opposite side of the drive unit 120 is compared to a structure in which impellers are disposed on both sides of the drive unit 120 in the related art. It is advantageous in cooling of (120).

In addition, the turbocompressor 100 of the present invention secures reliability by a structure described later and can produce a higher compression ratio than before.

In the present invention, a three-stage impeller is applied to the turbo compressor 100 to obtain a higher compression ratio.

In the case of the conventional turbo compressor 100 having a two-stage structure, the impellers are arranged to face in opposite directions on both sides of the shaft 125 so that the thrust applied to each impeller cancels each other.

However, the turbo compressor 100 of the present invention is a three-stage turbo compressor 100 including first to third impellers 131, 141, and 181, and as shown in FIG. 2, the drive unit 120 On the opposite side of the first to third impellers (131, 141, 181) are disposed.

In the turbocompressor 100 of the present invention, the turbocompressor 100 is designed to include first to third compression units, so that the turbocompressor 100 can be miniaturized while achieving a high compression ratio through three-stage compression.

4 is a conceptual diagram showing the thrust applied to the impellers 131, 141, and 181.

Referring to FIG. 4, the forces acting on the impellers 131, 141, and 181 are shown, and the thrust pushed outward in the axial direction of the impellers 131, 141, and 181 by the refrigerant compressed and discharged from the impellers 131, 141, and 181 ( F _back ) acts toward the left direction as shown by an arrow on the drawing.

In addition, the force (F _inlet ) generated by the inflow of the refrigerant and the shroud force ₍ F _shroud ) applied to the wings of the impeller act on the impellers 131, 141, and 181.

In the conventional first-stage turbo compressor 100, since the pressure on the rear side of the first-stage impeller is equal to the first-stage discharge pressure, a non-contact type sealing member is not applied. On the other hand, in the two-stage turbo compressor 100, the pressure on the rear surface of the impeller approaches the discharge pressure of the three-stage turbo compressor 100. Therefore, in the two-stage turbo compressor 100, a non-contact type sealing member is installed on the impeller to prevent an increase in pressure of the two-stage impeller, thereby attenuating thrust. For example, in the two-stage turbo compressor 100, a non-contact type sealing member is installed on the rear surface of each impeller.

On the other hand, in the turbo compressor 100 of the present invention, as the thrust acting on the rear surfaces of each of the first to third impellers 131, 141, and 181 increases, the overall thrust decreases, so it is preferable that no sealing member is applied. do.

The thrust applied to the first to third impellers 131, 141, and 181 may be calculated based on the suction pressure, discharge pressure, inlet diameter, and outlet diameter of the impeller.

As described above, the first impeller 131 and the second impeller 141 are disposed to face the same direction, and the third impeller 181 faces the opposite direction to the first and second impellers 131 and 141. Examples that can be arranged in the direction are shown in FIGS. 3 and 4 .

As shown in FIGS. 3 and 4, the first and second impellers 131 and 141 face the same direction, and the third impeller 181 faces the opposite direction of the first and second impellers 131 and 141. When disposed in the direction toward the first to third impellers (131, 141, 181) respectively, the thrust applied may be defined by [Equation 1] to [Equation 3], respectively.

The thrust of the first impeller 131 is [Equation 1] can be expressed as

[Equation 1]

F ₁ = (P ₂ - P ₁ ) * A _i1 + (P ₂ - P _1.5 ) * A _o1

In [Equation 1], F ₁ is the thrust of the first impeller 131, P ₁ is the pressure on the suction side of the first impeller 131, P _1.5 is the pressure on the wing side of the first impeller 131, P ₂ Is the pressure applied to the rear surface of the first impeller 131 and the pressure on the suction side of the second impeller 141, A _i1 is the area of the first impeller 131 on the suction side (A _i in FIG. 5), A _o1 is the first 1 is the cross-sectional area in the radial direction from the blade side of the impeller 131 (A _o in FIG. 5 ).

In addition, the thrust of the second impeller 141 can be expressed by [Equation 2].

[Equation 2]

F ₂ = [(P _3.5 - P ₂ ) * A _i2 + (P _3.5 - P _2.5 ) * A _o2 ]

In [Equation 2], F ₂ is the thrust of the second impeller 141, P ₂ is the pressure on the suction side of the second impeller 141, P _2.5 is the pressure on the wing side of the second impeller 141, P ₃ is the pressure at the side of the second impeller 141, P _3.5 is the pressure applied to the rear surface of the second impeller 141, A _i2 is the area of the second impeller 141 on the suction side (A _i in FIG. 5), A _o2 is a cross-sectional area (A _o in FIG. 5 ) of the second impeller 141 in the radial direction from the wing portion side.

In addition, the thrust of the third impeller 181 can be expressed by [Equation 3].

[Equation 3]

F ₃ = -(P ₄ - P _3.5 ) * A _o3 - (P ₄ - P ₃ ) * A _i3 + P ₃ * A _s ]

In [Equation 3], F ₃ is the thrust of the third impeller 181, P ₃ is the pressure on the suction side of the second impeller 141, P _3.5 is the pressure on the wing side of the third impeller 181, P ₄ Is the pressure at the rear of the third impeller 181, A _i3 is the area of the third impeller 181 at the suction side (A _i in FIG. 5), A _o3 is at the wing side of the third impeller 181 at the discharge port. The cross-sectional area in the radial direction (A _o in FIG. 5 ), A _s is the cross-sectional area of the shaft 125 .

Based on [Equation 1] to [Equation 3], in order to secure reliability while minimizing the sum of the thrust applied to the first to third impellers 131, 141, and 181, the third impeller 181 The applied thrust should be designed to be 1.3 to 1.5 times higher than the thrust applied to the first impeller 131 or the second impeller 141 .

For example, the thrust applied to the third impeller 181 is preferably designed to be 1.4 times higher than the thrust applied to the first impeller 131 or the second impeller 141 .

In the present invention, the first to third impellers 131, 141, and 181 rotate at the same rotational speed, and therefore, the pressure ratio of each impeller is proportional to the square of the discharge hole diameter, and the third impeller 181 ) should be designed to be 17% to 19% larger than the diameters of the outlets of the first and second impellers 131 and 141.

For example, it is preferable that the discharge port diameter of the third impeller 181 is designed to be 18% larger than the discharge port diameters of the first and second impellers 131 and 141 .

As shown in FIG. 5, the first and second impellers 131 and 141 face the same direction, and the third impeller 181 faces the first and second impellers 131 and 141 in the opposite direction. When disposed, the sum of thrust applied to the first to third impellers 131, 141, and 181 may be derived by [Equation 4].

[Equation 4]

F _thrust = [(P ₂ - P ₁ ) * A _i1 + (P ₂ - P _1.5 ) * A _o1 ] + [(P _3.5 - P ₂ ) * A _i2 + (P _3.5 - P _2.5 ) * A _o2 ] + [-(P ₄ - P _3.5 ) * A _o3 - (P ₄ - P ₃ ) * A _i3 + P ₃ * A _s ]

In [Equation 4], F _thrust is the sum of the thrusts applied to the first to third impellers 131, 141, and 181, P ₁ is the pressure at the suction side of the first impeller 131, P _1.5 is the first The pressure at the wing side of the impeller 131, P ₂ is the pressure applied to the rear surface of the first impeller 131 and the pressure at the suction side of the second impeller 141, A _i1 is the area of the first impeller 131 at the suction side (A _i in FIG. 5 ), A _o1 is the cross-sectional area in the radial direction from the wing side of the first impeller 131 (A _o in FIG. 5 ), P _2.5 is the pressure on the wing side of the second impeller 141, P ₃ is the pressure on the suction side of the second impeller 141, P _3.5 is the pressure applied to the rear surface of the second impeller 141, A _i2 is the area of the second impeller 141 on the suction side (A _i in FIG. 5), A _o2 is the cross-sectional area in the radial direction from the wing side of the second impeller 141 (A _o in FIG. 5 ), P ₄ is the pressure at the back of the third impeller 181, P ₃ is the third impeller 181 The pressure at the suction side of , P _3.5 is the pressure at the wing side of the third impeller 181, A _i3 is the area of the third impeller 181 on the suction side (A _i in FIG. 5 ), A _o3 is the third at the discharge port The cross-sectional area of the impeller 181 in the radial direction from the blade side (A _o in FIG. 5 ), _As is the cross-sectional area of the shaft 125 .

In addition, [Equation 4] includes three square brackets, the first square bracket is the thrust of the first impeller 131, the second square bracket is the thrust of the second impeller 141, and the third square bracket is the third impeller 181 ), and these are described above in [Equation 1] to [Equation 3].

The thrust of the first impeller 131 is a positive (+) value, and is a force acting in the rightward direction on the drawing, and the thrust of the second impeller 141 is a positive (+) value, and the right side on the drawing It is a force acting in the direction, and the thrust of the third impeller 181 is a negative (-) value, and is a force acting in a direction toward the left on the drawing.

The resultant thrust of the first impeller 131 and the second impeller 141 is preferably balanced with the thrust of the third impeller 181.

In order to prevent leakage to the rear surface of the impeller, a sealing member may be installed.

The turbo compressor 100 of the present invention may further include a bearing part.

The bearing part is installed on the shaft 125 to support a load applied to the shaft 125 .

The bearing unit may include journal bearings 151 and 152 and thrust bearings 153 and 154 . Detailed structures of the journal bearings 151 and 152 and the thrust bearings 153 and 154 have been described above.

The journal bearings 151 and 152 are installed to surround the shaft 125 and support a load of the shaft 125 in a radial direction.

The thrust bearings 153 and 154 are installed on the shaft 125 so as to be disposed in a direction crossing one direction to support a load in the one direction.

In the turbo compressor 100 of the present invention, in order to increase the efficiency of the non-contact type sealing member, the above-described impeller arrangement, journal bearings 151 and 152, and thrust bearings 153 and 154 may also be considered.

In the present invention, since the first to third impellers 131, 141, and 181 are disposed on one side of the shaft 125, both ends of the journal bearings 151 and 152 are also disposed on one side of the shaft 125. do.

A gap between each of the journal bearings 151 and 152 and the shaft 125 and a distance between both ends of the journal bearings 151 and 152 determine the deflection of the shaft 125 .

In addition, in order to safely minimize the gap between the first to third impellers 131, 141, 181 and the shaft 125, the distance between both ends of the journal bearings 151 and 152 and the first to third impellers 131 and 141 , 181) needs to be designed.

The distance between both ends of the journal bearings 151 and 152 is the extension direction of the shaft 125 between the journal bearing 151 (first journal bearing) near the center and the journal bearing 152 (second journal bearing) near the right side in FIG. 3 . may be a distance to

To this end, [Equation 5] may be applied in relation to the distance between both ends of the journal bearings 151 and 152 and the positions where the first to third impellers 131, 141 and 181 are disposed.

[Equation 5]

ε _seal = ls * tan(2ε/lb)

In [Equation 5], ε _seal is the journal bearing gap, ls is the maximum distance between the impeller and the journal bearing, ε is the impeller tip gap, and lb is the distance between both ends of the journal bearing.

For example, if the maximum distance between one of the first to third impellers 131, 141, and 181 and the journal bearing is 200 mm and the gap between the journal bearings is 120 µm, the tip gap of the impeller is designed to be 200 µm. , The distance between both ends of the journal bearings 151 and 152 should be 115 mm or more, and may be about 175% of the maximum distance between the first to third impellers 131, 141, and 181 and the journal bearings 151 and 152. have.

The gap between the journal bearings 151 and 152 is the gap between the inner circumference of the journal bearing and the outer circumference of the shaft 125, and the maximum distance between the impellers 131, 141 and 181 and the journal bearings 151 and 152 is the adjacent impeller 131, 141, 181) and the journal bearing, the maximum distance in the direction of the shaft 125, and the tip clearance of the impellers 131, 141, 181 are the inner circumference of the impellers 131, 141, 181 and the outer circumference of the shaft 125. There may be a gap between Also, the distance between both ends of the journal bearings 151 and 152 may be an axial distance between the two journal bearings 151 and 152 .

As described above, the turbo compressor 100 of the present invention includes the first to third compression units 130, 140, and 180, the arrangement of the first to third impellers 131, 141, and 181, and the non-contact Reliability can be secured through the arrangement of seals and the pressure ratio division design of each impeller.

As such, as in the present invention, the first to third impellers 131, 141, and 181 are disposed on one side of the shaft 125, so that the compression ratio is higher than that of the conventional turbo compressor 100. And it is also advantageous in cooling the drive unit 120.

The turbo compressor 100 described above is not limited to the configuration and method of the above-described embodiments, but the embodiments may be configured by selectively combining all or part of each embodiment so that various modifications can be made.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above detailed description should not be construed as limiting in all respects and should be considered illustrative. The scope of the present invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

100: turbo compressor
110: casing 111: shell
112: front frame 113: rear frame
120: driving unit 121a: refrigerant inlet passage
121: stator 122: rotor
125 axis
130: first compression unit 131: first impeller
132: first impeller housing 132b: first inlet
132c: first exit
140: second compression unit 141: second impeller
142: second impeller housing 142b: second inlet
142d: second outlet 180: third compression unit
181: third impeller 182: third impeller housing
182b: third entrance 182g: third exit 182f: inflow passage

Claims (12)

a driving unit capable of generating rotational power for compression of the refrigerant;
a shaft extending in one direction and rotatably coupled to the drive unit at one side and rotated by power generated from the drive unit; and
And first to third compression units each including first to third impellers installed on the shaft to receive rotational force by the shaft,
The first to third impellers are installed to be rotatable on the other side of the shaft so as to be provided on a side opposite to the driving unit. According to claim 1,
The first impeller is disposed such that one side faces the drive unit, the second impeller is disposed to face the same direction as the first impeller, and the third impeller faces a direction different from that of the first impeller. Turbocompressor, characterized in that arranged to face. According to claim 2,
The driving unit is provided with a refrigerant suction passage formed to allow the first impeller to suck the refrigerant discharged from the evaporator and introduced into the compressor,
The first compression unit further includes a first impeller housing accommodating the first impeller and having a first inlet through which refrigerant flows into one side of the first impeller,
A turbocompressor, characterized in that one side of the first impeller is disposed to face the drive unit so that the refrigerant suction passage and the first inlet communicate with each other. According to claim 2 or 3,
The second compression unit further includes a second impeller housing accommodating the second impeller and having a second inlet through which refrigerant flows into one side of the second impeller,
The turbocompressor, characterized in that the second impeller is disposed in the same direction as the first impeller so that the second inlet allows the introduction of the refrigerant discharged from the first impeller. According to claim 2,
The turbo compressor of claim 1 , wherein the third compression unit further includes a third impeller housing accommodating the third impeller and having a third inlet through which refrigerant flows into one side of the third impeller. According to claim 3,
The driving unit is
A stator fixedly coupled to an inner circumferential surface of the casing; and
A rotor located inside the stator and coupled to the shaft to an inner circumference to enable rotation of the shaft by a rotational force generated by interaction with the stator,
The turbocompressor, characterized in that the refrigerant inlet passage is provided along at least one direction in the stator to be able to cool the heat generated in the stator. According to claim 2,
The thrust applied to the third impeller is 1.3 to 1.5 times higher than the thrust applied to the first or second impeller. According to claim 7,
The thrust of the first impeller is, [Equation 1] Turbocompressor, characterized in that defined as.
[Equation 1]
F ₁ = (P ₂ - P ₁ ) * A _i1 + (P ₂ - P _1.5 ) * A _o1
In [Equation 1], F ₁ is the thrust of the first impeller, P ₁ is the pressure on the suction side of the first impeller, P _1.5 is the pressure on the wing side of the first impeller, and P ₂ is the pressure applied to the rear surface of the first impeller The pressure, A _i1 , is the area of the first impeller at the suction side, and A _o1 is the cross-sectional area in the radial direction at the wing side of the first impeller at the discharge port. According to claim 7,
A turbocompressor, characterized in that the thrust of the second impeller is defined by [Equation 2].
[Equation 2]
F ₂ = [(P _3.5 - P ₂ ) * A _i2 + (P _3.5 - P _2.5 ) * A _o2 ]
In [Equation 2], F ₂ is the thrust of the second impeller, P ₂ is the pressure on the suction side of the second impeller, P _2.5 is the pressure on the wing side of the second impeller, P ₃ is the pressure on the suction side of the second impeller, P _3.5 is the pressure applied to the rear surface of the second impeller, A _i2 is the area of the second impeller on the suction side, and A _o2 is the cross-sectional area in the radial direction from the wing side of the second impeller. According to claim 7,
The thrust of the third impeller is defined by [Equation 3].
[Equation 3]
F ₃ = -(P ₄ - P _3.5 ) * A _o3 - (P ₄ - P ₃ ) * A _i3 + P ₃ * A _s ]
In [Equation 3], F ₃ is the thrust of the third impeller, P ₃ is the pressure at the suction side of the second impeller, P _3.5 is the pressure applied to the rear surface of the second impeller, and P ₄ is the pressure at the rear surface of the third impeller. The pressure, A _i3 is the area of the third impeller at the suction side, A _o3 is the cross-sectional area in the radial direction from the wing side of the third impeller at the discharge port, and _As is the cross-sectional area of the shaft. According to claim 1,
Further comprising a bearing installed on the shaft to support a load applied to the shaft,
the bearing,
a journal bearing installed to surround an outer circumference of the shaft and supporting a load in a radial direction of the shaft; and
and a thrust bearing connected to the shaft to support a load in the one direction so as to be disposed in a direction crossing the one direction. According to claim 11,
The turbocompressor, characterized in that the distance between both ends of the journal bearing and the positions where the first to third impellers are disposed can be derived by [Equation 5].
[Equation 5]
ε _seal = ls * tan(2ε/lb)
In [Equation 5], ε _seal is the gap between the inner circumference of the journal bearing and the outer circumference of the shaft, ls is the maximum distance in the axial direction between the adjacent impeller and the journal bearing, and ε is the gap between the inner circumference of the impeller and the outer circumference of the shaft. , lb is the axial distance between the two journal bearings.

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