KR20200079039A - Two stage centrifugal compressor - Google Patents

Abstract

The present invention relates to a two-stage centrifugal compressor. According to an embodiment of the present invention, the two-stage centrifugal compressor includes first-stage and second-stage impellers which are coupled to a rotary shaft so as to improve compression performance. The second-stage impeller includes a second blade having a flow cross section that is a flow cut area (A_fc) smaller than and an expansion area (Ae) larger than a first blade of the first-stage impeller, thereby easily adjusting the flow cross section of the second blade in accordance with a required speed.

Description

Two stage centrifugal compressor}

The present invention relates to a two-stage centrifugal compressor.

In general, an air conditioner is a device that cools or heats an indoor space. The air conditioner includes a compressor for compressing a refrigerant, a condenser for condensing the refrigerant discharged from the compressor, an expander for expanding the refrigerant passing through the condenser, and an evaporator for evaporating the refrigerant expanded in the expander.

The turbo freezer includes a compressor that sucks a low-pressure refrigerant and compresses it with a high-pressure refrigerant, and a condenser, an expansion valve, and an evaporator to drive a refrigeration cycle.

The turbo refrigerator is provided with a centrifugal turbo compressor (hereinafter, a turbo compressor). The turbo compressor acts to discharge the gas in a high pressure state while converting the kinetic energy generated by the driving motor into a positive pressure, and may include one or more impellers that rotate by the driving force of the driving motor to compress the refrigerant. For example, when two impellers are provided, two-stage centrifugal compression may be performed, which shows better compression efficiency than one-stage centrifugal compression.

The design conditions of the first and second impellers arranged in the two-stage centrifugal compressor may be set differently depending on the capacity and pressure conditions of the working fluid. Therefore, there are many difficulties in optimizing the shape and size of the first and second impellers.

Korean Registered Patent Publication No. 10-0511934 (August 25, 2005)

In order to solve the above problems, an object of the present invention is to provide a two-stage centrifugal compressor equipped with a sheet metal impeller capable of designing by modifying the shape and size of the blade.

In addition, an object of the present invention is to provide a two-stage centrifugal compressor capable of reducing a flow cross-sectional area by applying a flow cut to a blade of a two-stage impeller.

In addition, it is an object of the present invention to provide a two-stage centrifugal compressor that can prevent the efficiency of the impeller from deteriorating by rapidly increasing the flow rate even by applying a flow cut to the blade by extending the leading edge portion of the blade of the two-stage impeller Should be

In addition, it is an object to provide a two-stage centrifugal compressor capable of improving the efficiency of the impeller by proposing an aspect ratio of the leading edge portion of the blade in an optimal range.

In order to solve the above problems, the two-stage centrifugal compressor according to an embodiment of the present invention includes first and second stage impellers coupled to a rotating shaft to improve compression performance.

The second stage impeller includes a second blade having a flow cross-sectional area smaller than the first blade of the first stage impeller by a flow cut area A _fc and larger by an expansion area Ae. It is easy to adjust the flow cross-sectional area of the blade.

The second stage impeller is attached to the second hub, the second blade, and the second shroud, respectively, to form a sheet metal impeller, so the design of the impeller is easy.

The flow cut region A _fc represents a cross-sectional area reduced by a set width W1 toward the shroud engaging surface based on the hub engaging surface of the first blade.

The hub coupling surface is a surface where the first blade and the first hub are coupled, and the shroud coupling surface may be another surface to which the first blade and the first shroud are coupled.

The extended area A _e may constitute a cross-sectional area having a sector shape rotated by a set angle θ from a point of the shroud engagement surface of the first blade.

When defining a point at which the extension line (ℓs) of the shroud engaging surface of the first blade intersects the first leading edge of the first blade as the origin (C1), the second blade, the origin (C1) And a second leading edge having a shape when the first leading edge is rotated by a set angle (θ) toward the introduction portion as a center.

The extension line Ls of the second leading edge is formed in a direction different from the extension line of the first leading edge.

The distance between the introduction of the second impeller and the second leading edge may be formed closer than the distance between the introduction of the first impeller and the first leading edge.

A first extension line (L1) that divides the thickness of the second blade into two equal parts, and a second extension line (L2) extending in a direction perpendicular to the first extension line (L1) at a point where the thickness of the second blade starts to decrease. When defining ), the second blade includes an edge part defined as a portion from the second extension line l2 toward the leading edge of the second blade.

When the ratio of the distance from the second extension line (L2) to the leading edge with respect to the value (a) obtained by dividing the thickness of the second blade into two equal parts is defined as an aspect ratio (A _R,E ), the The aspect ratio (A _R,E ) is formed in a range of 2 or more and 4 or less.

The second hub is formed larger than the first hub by the flow cut region A _fc .

According to the above-described solution, since the shrouds, hubs, and blades of the impeller are individually manufactured and provided with a sheet metal impeller in a manner of adhering to each other, the shape and size of the blade can be modified and designed, and accordingly, the design freedom of the impeller. There is an advantage that can increase.

In particular, there is an advantage in that the relatively small second stage impeller need not be designed to be a complete part of the first stage impeller.

In addition, by applying a flow cut to the blade of the second stage impeller, the flow cross-sectional area can be reduced to reduce the flow rate of the fluid passing through the impeller.

In addition, by extending the leading edge portion of the blade of the second stage impeller, even if a flow cut is applied to the blade, it is possible to prevent the efficiency of the impeller from deteriorating due to a rapid increase in flow velocity.

In addition, it is possible to improve the efficiency of the impeller by proposing an aspect ratio of the leading edge portion of the blade as an optimal range.

1 is a cross-sectional view showing a partial configuration of a two-stage centrifugal compressor according to an embodiment of the present invention.
2 is an exploded perspective view showing the configuration of a first stage impeller according to an embodiment of the present invention.
3 is a cross-sectional view showing the configuration of the first impeller.
4 is a cross-sectional view showing a state in which a flow cut is applied to the second stage impeller according to an exemplary embodiment of the present invention and the edge part of the blade is extended compared to the first stage impeller.
5 is a view showing the configuration of the edge part of the blade of the second stage impeller according to an embodiment of the present invention.
6 is a graph showing a change in efficiency of an impeller according to an aspect ratio of an edge part of a blade of a second stage impeller according to an embodiment of the present invention.
7 is a graph showing a change in the efficiency of the impeller according to the flow coefficient when the aspect ratio of the edge parts of the blades of the second stage impeller according to an embodiment of the present invention is varied.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. It should be noted that in adding reference numerals to the components of each drawing, the same components have the same reference numerals as possible even though they are displayed on different drawings. In addition, in describing embodiments of the present invention, when it is determined that detailed descriptions of related well-known configurations or functions interfere with understanding of the embodiments of the present invention, detailed descriptions thereof will be omitted.

In addition, in describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only for distinguishing the component from other components, and the nature, order, or order of the component is not limited by the term. When a component is described as being "connected", "coupled" or "connected" to another component, the component may be directly connected to or connected to the other component, but another component between each component It should be understood that may be "connected", "coupled" or "connected".

1 is a cross-sectional view showing a partial configuration of a two-stage centrifugal compressor according to an embodiment of the present invention.

1, the compressor 10 according to an embodiment of the present invention is a two-stage centrifugal compressor (Two stage) capable of compressing a working fluid (refrigerant) in two stages as one component of a refrigeration cycle for driving a turbo refrigerator centrifugal compressor).

In the compressor 10, a main body 20 in which a refrigerant inlet 21 and a refrigerant outlet 25 are formed, a motor (not shown) provided in the body 20, and installed inside the body 20 It includes a rotating shaft 30 that can be rotated by the driving force of the motor.

The refrigerant inlet 21 is connected to a suction pipe for guiding suction of refrigerant evaporated from the evaporator, and the refrigerant outlet 25 can be connected to a discharge pipe extending to the condenser.

The compressor 20 further includes a plurality of impellers 100 and 200 located inside the main body 20 and rotatably provided by the rotation shaft 30. The plurality of impellers 100 and 200 may be sequentially arranged in the longitudinal direction of the rotating shaft 30. The kinetic energy increased according to the rotation of the plurality of impellers 100 and 200 is converted into pressure energy to compress the refrigerant.

In detail, the plurality of impellers (100,200) is disposed adjacent to the refrigerant inlet (21) and is positioned adjacent to the first stage impeller (100) and the refrigerant outlet (25) coupled to the outer circumferential surface of the rotating shaft (30). It is disposed in the second stage impeller 200 is included.

The compressor 20 may further include a fastening member 50 for fastening the first stage impeller 100 and the rotating shaft 30. The fastening member 50 may be fastened to the end of the rotating shaft 30 through the hub of the first stage impeller 100.

The first stage impeller 100 first compresses the refrigerant flowing from the refrigerant inlet 21, and the second stage impeller 200 secondarily compresses the first compressed refrigerant to coolant outlet 25 ).

Between the first and second stage impellers 100 and 200, a return channel 300 is formed to guide the refrigerant compressed in the first stage impeller 100 to the second stage impeller 200 side. The return channel 300 extends roundly from the radially outer side of the first stage impeller 100, and may have a cap shape, for example.

The configuration of the first stage impeller 100 and the second stage impeller 200 are substantially the same. However, since the pressure and flow conditions of the refrigerant passing through the first stage impeller 100 are different from the pressure or flow conditions of the refrigerant passing through the second stage impeller 100, the first stage impeller 100 The size or shape may be formed differently from the size or shape of the first stage impeller 100.

Figure 2 is an exploded perspective view showing the configuration of the first stage impeller according to an embodiment of the present invention, Figure 3 is a cross-sectional view showing the configuration of the first impeller.

2 and 3, the first stage impeller 100 according to an embodiment of the present invention, the hub 110, the blade 120 and the shroud 120 are made of separate parts Later, it is defined as a "sheet metal impeller" constructed in a manner that adheres to each other. And, the second stage impeller 200 is also composed of a "sheet metal impeller".

Hereinafter, the configuration will be described based on the first stage impeller 100. However, it is noted that the description of the basic configuration of the first stage impeller 100 can also be applied to the second stage impeller 200.

The first stage impeller 100 includes a hub 110 coupled to the rotating shaft 30 and a plurality of blades 120 and a plurality of blades 120 having one surface coupled to the upper portion of the hub 110. The shroud 130 is coupled to the other surface of the.

The hub 110 includes an approximately disc-shaped hub body 111 and a central fastening portion 112 protruding from a central portion of the hub body 111. A fastening hole 113 into which the rotating shaft 30 or the fastening member 50 is inserted may be formed in the central fastening part 112.

On one surface of the hub body 111, a blade coupling portion 115 to which the blade 120 is coupled is formed. The blade coupling portion 115 forms a groove into which the hub coupling surface 126 of the blade 120 can be inserted, and corresponding to the shape of the blade 120, bent or rounded in a radial direction Can be.

The plurality of blades 120 may be joined to the blade coupling portion 115. In one example, the plurality of blades 120 may be adhered to the blade coupling portion 115. The plurality of blades 120 are arranged spaced apart in the circumferential direction, and are configured to be bent or rounded in a radial direction.

The plurality of blades 120 is composed of 13 blades, and each blade may have the same thickness. Here, "thickness" means the circumferential width of each blade.

In the blade 120, a leading edge 121 forming a leading edge through which the refrigerant flowing in the axial direction flows in and a trailing edge 125 forming a rear edge through which the refrigerant flowing along the blade 120 is discharged. ) Is included.

In addition, the blade 120 includes a hub coupling surface 126 having a surface coupled to the hub 110 and a surface coupled to the shroud 130 with a shroud coupling surface 127. That is, the blade 120 may be defined by the leading edge 121, trailing edge 125, hub coupling surface 126, and shroud coupling surface 127.

The shroud 130 includes a shroud body 131 joined to the shroud engagement surface 127 of the blade 120. The shroud body 131 may have a ring shape. In addition, the outer peripheral surface of the shroud main body 131 may form a refrigerant outlet portion 138 discharged by the refrigerant.

The shroud 130 includes an extension 132 extending axially from the shroud body 131. The extension portion 132 includes a refrigerant introduction portion 135 for introducing the refrigerant into the first impeller 100. The refrigerant introduction part 135 is formed at an end of the extension part 132 and can be understood as an opening of the shroud 130.

The blade 120 is located between the hub 110 and the shroud 130, and a space between the plurality of blades 120 forms a refrigerant passage through the first impeller 100. . Refrigerant may be introduced in the axial direction of the first impeller 100 through the refrigerant introduction part 135, and may be discharged in the radial direction of the first impeller 100 through the refrigerant outlet part 138.

4 is a cross-sectional view showing a state in which a flow cut is applied to the second stage impeller according to an exemplary embodiment of the present invention and the edge part of the blade is extended compared to the first stage impeller.

4, the size and shape of the second stage impeller 200 according to an embodiment of the present invention is somewhat different when compared to the first stage impeller 100.

The pressure of the refrigerant flowing into the second stage impeller 200 may be higher than the pressure of the refrigerant flowing into the first stage impeller 100. However, since the mass flow rate of the refrigerant passing through the first and second stage impellers 100 and 200 is the same, the volumetric flow rate of the refrigerant passing through the second stage impeller 200 is the refrigerant passing through the first stage impeller 100. It needs to be formed smaller than the volume flow rate of.

Therefore, the flow cross-sectional area of the blade 220 of the second stage impeller 200 is formed smaller than the flow cross-sectional area of the blade 120 of the first stage impeller 100, and accordingly, the second stage impeller 200 The size of the first stage impeller 100 may be formed smaller than the size.

The second stage impeller 200 includes a hub 210, a blade 220 and a shroud 230. The hub 210, blade 220, and shroud 230 may be referred to as “second hub”, “second blade” and “second shroud”.

As described above, since these components are separately manufactured and adhered to form an impeller, when the blade 220 is separately manufactured, it can be designed and manufactured smaller than the size of the blade 120 of the first stage impeller 100. have.

In detail, in this embodiment, the flow cross-sectional area of the second blade 220 may be formed smaller than the flow cross-sectional area of the first blade 120 by the flow cut area A _fc . The flow cut region A _fc represents a cross-sectional area reduced by a set width W1 toward the shroud engaging surface 127 based on the hub engaging surface 126 of the first blade 120.

That is, the flow cut region A _fc is understood as a cross-sectional area extending roundly in the axial and radial directions while having a set width W1 in the first blade 120.

In the second impeller 200, the size of the hub body 211 may be increased by the reduced flow cross-sectional area of the second blade 220. The description of the hub body 211 uses the description of the hub body 111 of the first hub 110. That is, the size of the hub body 211 of the second impeller 200 may be larger than the size of the hub body 111 of the first impeller 100.

In addition, the hub coupling surface 226 of the second blade 220 may be joined to the hub body 211.

Since the flow cross-sectional area of the second blade 220 is relatively small as the flow cut region A _fc , the flow rate of the refrigerant passing through the second blade 220 may be increased too. In this case, a phenomenon in which the flow efficiency of the refrigerant passing through the leading edge 221 of the second blade 220 decreases appears. The leading edge 121 may be referred to as a “first leading edge” and the leading dpt edge 221 may be referred to as a “second leading edge”.

To solve this, in this embodiment, when compared with the first blade 120, the flow cross-sectional area of the second blade 220 may be configured to increase by the expansion area A _e . That is, the second blade 220 may be configured such that the flow cross-sectional area decreases by the flow-cut area A _fc and the flow cross-sectional area increases by the expansion area A _e .

The extended area (A _e ), when compared with the first blade 120, the fan-shaped shape rotated by a set angle (θ) from a point of the shroud engagement surface 127 of the first blade 120 It is possible to construct a cross-sectional area having.

In detail, when defining the point where the extension line (ℓs) of the shroud engaging surface 126 of the first blade 120 and the leading edge 121 intersect as the origin (C1), the second blade 220 is the It includes a leading edge 221 having a shape when the leading edge C1 is rotated by a set angle θ to the refrigerant introduction unit 135 side around the origin C1. That is, the extension line ls of the leading edge 221 of the second blade 220 may be formed in a different direction from the extension line of the leading edge 121 of the first blade 120.

According to this configuration, the distance between the refrigerant introduction portion 235 of the second impeller 200 and the leading edge 221 of the second blade 220 is the refrigerant introduction portion 135 and the first of the first impeller 100. It may be formed closer than the distance between the leading edge 121 of the blade 120.

Accordingly, the refrigerant flowing through the refrigerant introduction portion 235 of the second impeller 200 may achieve speed reduction while passing through the leading edge 221 positioned in the relatively extended region of the second blade 220. There will be.

In summary, the flow cross-sectional area of the second blade 220 is reduced by the flow-cut area A _fc , and thus the flow rate of the refrigerant may increase more than necessary, but the flow cross-sectional area increases by the expansion area A _e . By compensating, the flow rate of the refrigerant can be adjusted.

In addition, since the flow cross-sectional area of the second blade 220 may be relatively large, the strength of the second blade 220 may be reinforced.

As a result, the design of the second blade 220 can be easily performed so that the flow cross-sectional area can be adjusted according to the speed of the refrigerant required by the second impeller 200.

5 is a view showing the configuration of the edge part of the blade of the second stage impeller according to an embodiment of the present invention.

Referring to FIG. 5, the second blade 220 of the second stage impeller 200 according to the embodiment of the present invention has an edge part 221a whose thickness decreases from other parts of the second blade 220. Is included.

The first extension line (l1) that divides the thickness of the second blade 220 into two equal parts, and the first extension line at a point where the thickness of the second blade 220 starts to decrease in the direction toward the leading edge 221 When defining a second extension line (L2) extending in a direction perpendicular to (L1), the edge part (221a) may be defined as a portion from the second extension line (L2) toward the leading edge (221). .

The ratio (b/a) of the distance from the second extension line (L2) to the leading edge (221) with respect to the value (a) of which the thickness of the second blade 220 is bisected is divided into an aspect ratio, A _R,E ). The aspect ratio is a factor that determines the shape of the edge part 221a, and may determine the efficiency of the second impeller 200.

In this embodiment, the aspect ratio (A _R,E ) is determined by a value of 2 or more and 4 or less. In the following, experimental data that proposes a range of such aspect ratios are introduced.

6 is a graph showing a change in efficiency of an impeller according to an aspect ratio of an edge part of a blade of a second-stage impeller according to an embodiment of the present invention, and FIG. 7 is a blade of a second-stage impeller according to an embodiment of the present invention When the aspect ratio of the edge parts is different, it is a graph showing the change in the efficiency of the impeller according to the flow coefficient.

First, FIG. 6 shows a state in which the efficiency of the second impeller 200 of the vertical axis is changed according to the aspect ratios A _{R and E} with respect to the edge part 221a of the horizontal axis.

The efficiency of the second impeller 200 is the actual amount of enthalpy increase with respect to the amount of enthalpy increase from the refrigerant introduction section 235 of the second impeller 200 to the refrigerant outlet section 238 (see FIG. 4) in an ideal state (Isentropic). It can be calculated as a ratio of.

Referring to FIG. 6, in the range of the aspect ratios A _{R and E} for the edge parts 221a of 2 or more and 4 or less, a reference efficiency (ηo) or more required for the efficiency of the second impeller 200 is Can be seen.

On the other hand, when the value of the aspect ratio (A _R,E ) for the edge part 221a is less than 2, the efficiency of the second impeller 200 decreases linearly, and similarly, the aspect ratio (A _R,E) When the value of) is greater than 4, it can be seen that the efficiency of the second impeller 200 decreases linearly.

Next, FIG. 7 shows a state in which the efficiency of the second impeller 200 of the vertical axis is changed according to the aspect ratios A _{R and E} with respect to the edge parts 221a with respect to the flow coefficient of the horizontal axis. The flow coefficient is a value indicating the flow rate of the refrigerant passing through the second impeller 200, and may vary depending on the size of the impeller.

Substantially, the flow coefficient corresponding to the amount of refrigerant flowing through the second impeller 200 according to the embodiment of the present invention falls within the range of 0.25 to 0.27.

In the range of the flow coefficient of 0.25 to 0.27, when the experiment was performed for the case where the aspect ratio (A _R,E ) for the edge part 221a is 1 or 2, the aspect ratio for the edge part 221a (A _{When R, E} ) is 2, the efficiency of the second impeller 200 is formed higher than that of the second impeller 200 when the aspect ratio A _R,E is 1, and indicates a reference efficiency (ηo) or higher. Can be seen.

As a result, when combining FIGS. 6 and 7, the shape of the second blade 220 is implemented such that the range of the aspect ratios A _{R and E} for the edge parts 221a is 2 or more and 4 or less, The efficiency of the second impeller 200 may be improved.

10: 2-stage centrifugal compressor 21: refrigerant inlet
25: refrigerant outlet 30: rotating shaft
100: first stage impeller 110: first hub
120: first blade 130: first shroud
200: second stage impeller 210: second hub
220: 2nd blade 230: 2nd shroud

Claims (12)

Axis of rotation;
A first stage impeller coupled to the rotating shaft and provided with a first hub, a first blade and a first shroud;
It is coupled to the rotating shaft, and includes a second stage impeller that further compresses the working fluid compressed by the first stage impeller,
In the second stage impeller,
A second herb; And
A two-stage centrifugal compressor including a second blade coupled to the second hub and having a flow cross-sectional area smaller than the first blade by a flow cut area (A _fc ) and larger by an expansion area (Ae). According to claim 1,
It is coupled to the second blade, a second shroud having an introduction portion into which the working fluid flows is further included,
The second hub, the second blade and the second shroud are two-stage centrifugal compressors, each of which is adhered. According to claim 2,
The flow cut region (A _fc ),
A two-stage centrifugal compressor showing a cross-sectional area reduced by a set width (W1) toward the shroud engaging surface based on the hub engaging surface of the first blade. The method of claim 3,
The hub coupling surface is a surface where the first blade and the first hub are coupled, and the shroud coupling surface is a two-stage centrifugal compressor that is the other surface to which the first blade and the first shroud are coupled. According to claim 2,
The extended area (A _e ),
A two-stage centrifugal compressor constituting a cross-sectional area having a fan-shaped shape rotated by a set angle (θ) from a point of the shroud coupling surface of the first blade. The method of claim 5,
When defining the point at which the extension line (ℓs) of the shroud engagement surface of the first blade intersects the first leading edge of the first blade as the origin (C1),
The second blade is a two-stage centrifugal compressor including a second leading edge having a shape when the first leading edge is rotated by a set angle (θ) toward the introduction side around the origin (C1). The method of claim 6,
An extension line (ℓs) of the second leading edge is a two-stage centrifugal compressor formed in a direction different from the extension line of the first leading edge. The method of claim 6,
The distance between the second impeller introduction portion and the second leading edge is
A two-stage centrifugal compressor that is formed closer than the distance between the introduction portion of the first impeller and the first leading edge. According to claim 1,
A first extension line (L1) that divides the thickness of the second blade into two equal parts, and a second extension line (L2) extending in a direction perpendicular to the first extension line (L1) at a point where the thickness of the second blade starts to decrease. When defining)
The second blade includes a second stage centrifugal compressor including an edge part defined as a portion facing the leading edge of the second blade from the second extension line (ℓ2). According to claim 1,
When the ratio of the distance from the second extension line (L2) to the leading edge with respect to the value (a) that divides the thickness of the second blade into two equal parts is defined as an aspect ratio (A _R,E ),
The aspect ratio (A _R,E ) is a two-stage centrifugal compressor formed in a range of 2 or more and 4 or less. According to claim 2,
The second hub,
The two-stage centrifugal compressor is formed larger than the first hub by the flow cut area (A _fc ). The method of claim 11,
A two-stage centrifugal compressor that is formed between the first and second stage impellers, and further includes a return channel for guiding the first compressed refrigerant in the first stage impeller toward the second stage impeller.

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