Turbo compressor

Provided is a turbo compressor. The turbo compressor includes a driving shaft, a first impeller, a second impeller, a first shroud, a second shroud, a first-stage outflow passage, and a second-stage outflow passage. Also, the turbo compressor includes a gap adjustment passage that is branched from at least one of the first-stage outflow passage or the second-stage outflow passage to extend to the first shroud.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119 and 35 U.S.C. 365 to Korean Patent Application No. 10-2019-0075260, filed on Jun. 24, 2019, in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a turbo compressor.

In general, compressors are machines that receive power from a power generation device such as an electric motor or a turbine to compress air, a refrigerant, or various working gases, thereby increasing a pressure. Compressors are being widely used in home appliances or industrial fields.

Such a compressor includes a turbo compressor that compresses a fluid by applying a centrifugal force by using a vane wheel (impeller) rotating at a high speed to convert a portion of velocity energy into pressure energy. For example, the turbo compressor may be used in a chiller system. In general, the compressor used in the chiller system corresponds to a turbo compressor.

The chiller system represents a system that supplies cold water to a demand place. In detail, the chiller system cools cold water by heat-exchange between a refrigerant circulating in a refrigerant cycle and cold water circulating in the demand place. Particularly, the chiller system may be understood as being installed in a large building or the like as a relatively large capacity facility.

The turbo compressor includes a driving shaft and an impeller coupled to the driving shaft. Particularly, the turbo compressor includes a two-stage compression tube compressor provided with a first-stage impeller and a second-stage impeller coupled to both ends of the driving shaft. In detail, a refrigerant compressed by the first-stage impeller flows to the second-stage impeller so as to be compressed again.

Here, since the refrigerant compressed in the first-stage impeller is supplied to the second-stage impeller, the refrigerant existing at a second-stage impeller side may have a relatively high pressure. Thus, different pressures may be applied to both the ends of the driving shaft to cause a phenomenon in which the driving shaft is pushed toward a first stage.

Thus, an interference between components may occur, and particularly, an interference between the impeller and the shroud accommodating the impeller may occur. To solve the above-described limitation, the following prior art document 1 has been disclosed.

PRIOR ART DOCUMENT 1

2. Title of Invention: Segregated impeller shroud for clearance control in a centrifugal compressor

In the prior art document 1, a turbo compressor that moves a shroud by using an actuator is disclosed. In detail, the shroud rotates in a circumferential direction by an operation of the actuator, and then, the shroud moves in an axial direction along a screw thread. Thus, a gap between the shroud and the impeller may be adjusted.

In the prior part document 1 as described above, a separate power device that is called the actuator has to be provided. Thus, an additional material cost is required, and a time required for manufacturing and assembly increases.

In addition, a separate shape such as the screw thread so as to move the shroud in the axial direction is necessary. Thus, the compressor may be complicated in configuration. Particularly, since the shroud rotates in the circumferential direction and moves in the axial direction, mechanical coupling and sealing designs may be complicated.

In addition, the gap between the shroud and the impeller may occur during the operation of the compressor. Thus, since the shroud has to move during the flow of the refrigerant, flow resistance may increase.

Also, a separate sensor device measuring the gap between the shroud and the impeller is required. This is done because the gap between the shroud and the impeller has to be known so as to drive the actuator.

SUMMARY

Embodiments provide a turbo compressor including a gap adjustment passage that supplies and moves a refrigerant compressed in an impeller to a first-stage shroud.

Embodiments also provide a turbo compressor that supplies a refrigerant having a high pressure, which is compressed in two stages to the first-stage shroud to reduce a gap between the first-stage shroud and the impeller, thereby improving efficiency.

Embodiments also provide a turbo compressor including a gap adjustment member that assists a gap adjustment passage to more effectively move the shroud.

In one embodiment, a turbo compressor includes a driving shaft, a first impeller and a second impeller, which are respectively coupled to both ends of the driving shaft, a first shroud configured to define a compression space in which the first impeller is disposed, a second shroud configured to define a compression space in which the second impeller is disposed, a first-stage outflow passage through which a refrigerant discharged from the first impeller flows, and a second-stage outflow passage through which a refrigerant discharged from the second impeller flows.

Also, the turbo compressor includes a gap adjustment passage that is branched from at least one of the first-stage outflow passage or the second-stage outflow passage to extend to the first shroud.

The turbo compressor may further include a first gap defined between the first impeller and the first shroud. The gap adjustment passage may be installed at one side of the first shroud so that the first shroud moves in a direction in which the first gap is narrowed by the refrigerant flowing to the gap adjustment passage.

The turbo compressor may further include a gap adjustment member coupled to the first shroud to allow the first shroud to move. The gap adjustment member may include an elastic member configured to apply an elastic force to the first shroud in a direction in which the first gap is widened.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It is noted that the same or similar components in the drawings are designated by the same reference numerals as far as possible even if they are shown in different drawings. In the following description of the present disclosure, a detailed description of known functions and configurations incorporated herein will be omitted to avoid making the subject matter of the present disclosure unclear.

In the description of the elements of the present disclosure, the terms first, second, A, B, (a), and (b) may be used. Each of the terms is merely used to distinguish the corresponding component from other components, and does not delimit an essence, an order or a sequence of the corresponding component. It should be understood that when one component is “connected”, “coupled” or “joined” to another component, the former may be directly connected or jointed to the latter or may be “connected”, coupled” or “joined” to the latter with a third component interposed therebetween.

FIG. 1is a view of a chiller system according to an embodiment.

As illustrated inFIG. 1, a chiller system10according to an embodiment includes a chiller unit100, a cooling tower20, and a demand place30.

The chiller unit100may be understood as a component in which a cooling cycle is provided. The chiller system10may be used in the same manner as the chiller unit100. That is, the chiller unit100may be called the chiller system10.

The cooling tower20may be a component that supplies cooling water to the chiller unit100. Also, in the chiller system10, a blower fan instead of the cooling tower20may be provided to be heat-exchanged with air. For example, the cooling top20may be installed in a chiller system having a relatively large size, and the blower fan may be installed in a chiller system having a relatively small size.

The demand place30may be a component in which the cool water heated-exchanged with the chiller unit100circulates. Here, the demand place30may be understood as a device or body space for conditioning air by using cold water.

A cooling water circulation passage40is disposed between the chiller unit100and the cooling tower20. The cooling water circulation passage40may be a tube that guides the cooling water so that the cooling water is circulated through the cooling tower20and the chiller unit100.

The cooling water circulation passage40may include a cooling water inflow passage42and a cooling water outflow passage44. The cooling water inflow passage42may be a tube that guides the cooling water so that the cooling water is introduced into the chiller unit100. Also, the cooling water outflow passage44may be a tube that guides the cooling water so that the cooling water heated in the chiller unit100flows to the cooling tower20.

A cooling water pump46driven to allow the cooling water to flow may be provided in at least one of the cooling water inflow passage42or the cooling water outflow passage44. For example, inFIG. 1, the cooling water pump46is provided in the cooling water inflow passage42.

An outflow temperature sensor47for detecting a temperature of the cooling water introduced into the cooling tower20is disposed in the cooling water outflow passage44. Also, an inflow temperature sensor48for detecting a temperature of the cooling water discharged from the cooling tower20is disposed in the cooling water inflow passage42.

A cold water circulation passage50is provided between the chiller unit100and the cold water demand place30. The cold water circulation passage50may be a tube that guides the cold water so that the cold water is circulated through the cold water demand place30and the chiller unit100.

The cold water circulation passage50may include a cold water inflow passage52and a cold water outflow passage54. The cold water inflow passage52may be a tube that guides the cold water so that the cold water is introduced into the chiller unit100. The cold water outlet passage54may be a tube that guides the cold water so that the cold water cooled in the chiller unit100flows to the cold water demand place30.

A cold water pump56that is driven to allow the cold water to flow may be provided in at least one of the cold water inflow passage52or the cold water outflow passage54. For example, inFIG. 1, the cold water pump56is provided in the cold water inflow passage52.

Here, the cold water demand place30may be a water cooling type air-conditioner in which air and cold water are heat-exchanged with each other.

For example, the cold water demand place30may include at least one unit of an air handling unit (AHU) in which indoor air and outdoor air are mixed with each other, and the mixed air is heat-exchanged with cold water to discharge the cooled air into an indoor space, a fan coil unit (FCU) disposed in the indoor space to heat-exchange the indoor air with the cold water, thereby discharge the cooled air into the indoor space, and a bottom tube unit buried in the bottom of the indoor space.

InFIG. 1, the cold water demand place30is provided as the AHU.

The cold water demand place30provided as the AHU may include a casing61, a cooling water coil62, and air blowers63and64. The cold water coil62may be a component which is installed in the casing61and through which the cold water passes.

The air blowers63and64may be provided on both sides of the cold water coil62to suction indoor air and outdoor air and then blow the suctioned air to the inner space. The air blowers63and64may include a first air blower63and a second air blower64. The first air blower63is installed so that the indoor air and the outdoor air are suctioned into the casing61. Also, the second air blower64is installed so that the conditioned air is discharged to the outside of the casing61.

Also, an indoor air suction part65, an indoor air discharge part66, an external air suction part67, and a conditioned air discharge part68.

When the air blowers63and64are driven, a portion of the air suctioned into the indoor air suction part65may be discharged to the indoor air discharge part66. Also, remaining air that is not discharged to the indoor air discharge part66may be mixed with the indoor air suctioned to the external air suction part67.

Also, the mixed air is heat-exchanged with the cold water coil62. Also, the mixed air that is heat-exchanged or cooled with the cold water coil62may be discharged into the indoor space through the conditioned air discharge part68. The conditioned air may be supplied to the indoor space to cool an indoor body space through the above-described processes.

Also, the cold water demand place30may correspond to a facility that directly uses the cold water. For example, the cold water demand place30may provide the cold water that is capable of reducing a temperature of a semiconductor component. Also, the chiller system10according to an embodiment may supply the cooling water to a hot water demand place instead of the cooling tower20.

The chiller system10according to an embodiment may be provided as various constituents without being limited to the constituent ofFIG. 1. That is, the constituents of the chiller system10may be merely an example and thus may be added, omitted, or modified.

Hereinafter, the chiller unit100will be described in detail.

FIG. 2is a schematic view illustrating a configuration of the chiller system in which a turbo compressor is installed according to an embodiment. The chiller unit100may be a portion in which a refrigeration cycle is provided in the chiller system10.

As illustrated inFIG. 2, the chiller unit100according to an embodiment includes a compressor200, an evaporator150, and a condenser140.

The compressor200may be a component for compressing a refrigerant. The compressor200according to an embodiment may be provided as a turbo compressor that is a kind of centrifugal compressor. The centrifugal compressor is understood as a compressor in which the refrigerant is compressed and discharged by converting kinetic energy of the refrigerant into static pressure energy through a rotation body such as an impeller or a blade.

The condenser140may be a constituent in which the refrigerant discharged from the compressor200and the cooling water flowing through the cooling water circulation passage40are heat-exchanged with each other. That is, the refrigerant compressed by the compressor200may be introduced into the condenser140. The evaporator150may be a constituent in which the refrigerant discharged from the condenser140and the cold water flowing through the cold water circulation passage50are heat-exchanged with each other.

Here, the condenser140is installed on a bottom surface, the evaporator150is installed above the condenser140, and the compressor200is installed above the evaporator150. The above-described arrangement is merely an example. For example, the compressor200, the evaporator150, and the condenser140may be disposed at various positions.

A condenser body170and an evaporator body180, each of which has a cylindrical shape extending in an axial direction, are provided in the condenser140and the evaporator150, respectively. The condenser body170and the evaporator body180may be provided to have the same length in the axial direction and be installed to be vertically spaced a predetermined distance from each other in parallel to each other. Particularly, the condenser body170and the evaporator body180may be installed so that the axial direction is parallel to the bottom surface.

Plates172and182for installation may be coupled to both ends of each of the condenser body170and the evaporator body180, respectively. Each of the plates172and182may have a rectangular shape and be installed perpendicular to the bottom surface. Also, the plates172and182include a condensation plate172installed on the condenser body170and an evaporation plate182installed on the evaporator body180.

A leg171provided in parallel to the bottom surface may be coupled to the condensation plate172so that the condensation plate172is stably installed on the bottom surface. A lower end of the evaporation plate182may be coupled to an upper end of the condensation plate172. Here, each coupling may be performed through a coupling member such as a bolt or coupled through welding.

A cooling water accommodation part174and a cold water accommodation part184, in which the cooling water and the cold water are accommodated, are provided in the condensation plate172and the evaporation plate182, respectively.

In summary, in the condenser140, the condensation plate172is coupled to each of both ends of the condenser body170, and the cooling water accommodation part174is coupled to the outside of the condensation plate172. Also, in the evaporator150, the evaporation plate182is coupled to each of both ends of the evaporator body180, and the cold water accommodation part184is coupled to the outside of the evaporation plate182.

Cooling water coupling parts176and177and cold water coupling parts186and187, which are coupled to cooling water circulation passage40and the cold water circulation passage50, are provided in the cooling water accommodation part174and the cold water accommodation part184, respectively.

In detail, a first cooling water coupling part176coupled to the cooling water inflow passage42and a second cooling water coupling part coupled to the cooling water outflow passage44may be provided in the cooling water accommodation part174. Also, a first cold water coupling part186coupled to the cold water inflow passage52and a second cold water coupling part coupled to the cold water outflow passage54may be provided in the cold water accommodation part184.

Referring toFIG. 2, the first cold water coupling part186, the second cold water coupling part187, the first cooling water coupling part176, and the second cooling water coupling part187may be sequentially disposed in a vertical direction. However, the above-described arrangement is merely an example.

Also, a chiller unit100according to an embodiment may include a control box160in which a device capable of controlling each component is provided. The control box may be attached in the form of a box to one side of each of the condenser140and the evaporator150.

The above-described constituents of the chiller unit may be merely an example and thus may be added, omitted, or modified. For example, an economizer may be further provided in the chiller unit100.

Also, the compressor200, the condenser140, and the evaporator150are connected to each other through tubes.

Hereinafter, a tube connecting the condenser140to the evaporator150is called a connection tube102. The connection tube102may be understood as a tube through which a liquid refrigerant condensed in the condenser140flows. Also, an expansion device103that expands the refrigerant may be provided in the connection tube102.

Here, the chiller unit100may further include an injection tube104connecting the connection tube102to the compressor200. The injection tube104may be understood as a tube through which at least a portion of the refrigerant flowing to the connection tube102flows.

That is, the injection tube104may be understood as a tube that is branched from the connection tube102. Particularly, the injection tube104may be branched from a rear side rather than the expansion device103in the flow direction. Also, the injection tube104may be provided with an injection expansion device105expanding the refrigerant.

As described above, the arrangement of the connection tube102and the injection tube104may be provided differently according to the design. Also, the expansion device103and the injection expansion device105may be arranged in various shapes and number and at various positions.

For example, the injection expansion device105is omitted, and the injection tube104may be branched from the front side rather than the expansion device103in the flow direction. That is, the refrigerant expanded in the expansion device103may flow into the injection tube104.

Also, the tube connecting the evaporator150to the compressor200is called a compressor inflow tube106. The compressor inflow tube106may be understood as a tube through which the refrigerant evaporated in the evaporator150flows.

Also, a tube connecting the condenser140to the compressor200is called a compressor outflow tube108. The compressor outflow tube108may be understood as a tube through which the refrigerant compressed in the compressor200flows.

Hereinafter, a flow of a fluid in the chiller system10will be described.

The refrigerant compressed by the compressor200flows to the condenser140along the compressor outflow tube108. Also, the refrigerant is heat-exchanged with the cooling water in the condenser140. In detail, the refrigerant flowing in the compressor200is introduced into the condenser body170and heat-exchanged with the cooling water while the refrigerant contacts the cooling water flowing through a plurality of cooling water tubes175provided in the condenser body170.

Here, the refrigerant is condensed by releasing heat to the cooling water, and thus, the cooling water increases in temperature by receiving the heat of the refrigerant. When the cooling tower20is omitted in the chiller system10, the refrigerant may be heat-exchanged with external air.

The refrigerant condensed in the condenser140flows to the evaporator150along the connection tube103. Here, a portion of the refrigerant flowing into the connection tube103may flow to the compressor200along the injection tube104.

Also, the refrigerant flowing into the connection tube103may be expanded in the expansion device103and introduced into the evaporator150. Also, the refrigerant is heat-exchanged with the cold water in the evaporator150.

In detail, the refrigerant is introduced into the evaporator body180and heat-exchanged with the cold water while the refrigerant contacts the cold water flowing through a plurality of cold water tubes185provided in the evaporator body180. Here, the refrigerant absorbs heat of the cold water and then is evaporated, and the cold water loses the heat to the refrigerant to decreases in temperature.

Also, the refrigerant evaporated by being heat-exchanged with the cold water flows to the compressor200along the compressor inflow tube106. Also, the refrigerant may circulate through the above process.

Hereinafter, the compressor200will be described in detail based on the above-described structure.

FIG. 3is a view illustrating a configuration of the turbo compressor according to an embodiment. InFIG. 3, for convenience of illustration, a cross section of the compressor200is schematically illustrated. Thus, the constituents of the compressor200is not limited thereto and may be added or omitted.

As illustrated inFIG. 3, the compressor200includes a stator220, a driving shaft210, impellers230and240, and shrouds250and260. Here, the stator220and the driving shaft210may be classified as a motor part, the impellers230and240and the shrouds250and260may be classified as a compression part.

Referring to the motor part, the stator220corresponds to a fixed constituent, and the driving shaft210corresponds to a rotatable constituent. The stator220and the driving shaft210are spaced apart from each other. Here, the compressor200may be provided with a housing (not shown) to which the stator220is fixed and which defines an outer appearance of the compressor200.

The driving shaft210may be provided with a rotor for generating an electromagnetic force together with the stator220. In detail, the rotor may be disposed within the driving shaft210. However, this is merely an example, and the compressor200may include a shaft and a rotor, which are separated from each other, and the rotor may be disposed outside the shaft.

Here, the driving shaft210is disposed to extend in an axial direction. That is, the axial direction means a direction in which the driving shaft210extends. InFIG. 3, the axial direction corresponds to a horizontal direction. Also, a direction perpendicular to the axial direction is called a radial direction, and a longitudinal direction inFIG. 3corresponds to one of the radial directions.

The stator220is disposed to surround the outside of the driving shaft210. That is, the stator220is disposed outside the driving shaft210in the radial direction. For example, the stator220may be provided in a cylindrical shape having the inside that is penetrated in the axial direction.

Referring to the compression part, the impellers230and240rotate together with the driving shaft210. Also, the shrouds250and260are generally understood as fixed constituents. However, in the compressor200according to an embodiment, a portion of the shrouds250and260are provided to be movable.

The impellers230and240are understood as constituents in which the refrigerant is suctioned in the axial direction and discharged in the radial direction. In detail, the impellers230and240rotate together with the driving shaft210, and the refrigerant is suctioned into the impellers230and240by rotational force. The refrigerant passes through the impellers230and240to increase in flow rate and pressure.

Also, the refrigerant is discharged in the radial direction and increases in pressure by a decrease in flow rate due to the expanded cross-sectional area. Thus, the refrigerant discharged from the impellers230and240may have a high pressure.

Also, the compressor200according to an embodiment includes the pair of impellers230and240respectively disposed at both ends of the driving shaft210. As described above, the impeller is divided into a first impeller230and a second impeller240.

Here, the first impeller230corresponds to a first-stage impeller compressing the refrigerant in one stage, and the second impeller240corresponds to a second-stage impeller compressing the refrigerant in two stages. Thus, the compressor200according to an embodiment may be understood as a two-stage compression turbo compressor.

The shrouds250and260are understood as constituents that accommodate the impellers230and240to provide a compression space. InFIG. 3, only the shrouds250and260are schematically illustrated, but the shrouds250and260may be provided in various shapes, i.e., may provide a diffuser and a volute. Also, the shrouds250and260may be coupled to the housing (not shown) to which the stator220is fixed to define an outer appearance thereof.

The shrouds250and260are also provided in a pair corresponding to the impellers230and240. In detail, the shrouds250and260may be divided into a first shroud250that accommodates the first impeller230and a second shroud260that accommodates the second shroud260.

The first impeller230and the first shroud250may be referred to as a first-stage side, and the second impeller240and the second shroud260may be referred to as a second-stage side. InFIG. 3, a left side corresponds to the first-stage, and a right side corresponds to the second-stage side.

Referring to the flow of the refrigerant, the refrigerant passing through the evaporator150is introduced to the first-stage side. In detail, the refrigerant is introduced into the first shroud250toward the first impeller230in the axial direction. Also, the refrigerant is compressed in one stage and discharged in the radial direction of the first impeller230.

Also, the refrigerant discharged from the first impeller230flows into the second-stage side. In detail, the refrigerant is introduced into the second shroud260toward the second impeller240in the axial direction. Also, the refrigerant is compressed in two stages and discharged in the radial direction of the second impeller240to flow to the condenser140.

Here, a predetermined gap is generated between the shrouds250and260and the impellers230and240. As described above, the impellers230and240are the rotatable constituents, and the shrouds250and260are the fixed constituents. Thus, the shrouds250and260and the impellers230and240are spaced apart from each other so as not to interfere with the rotation of the impellers230and240.

Also, the compressor200may support the driving shaft210with a gas bearing. In detail, the driving shaft210is not disposed in a completely fixed state in the radial direction, but is disposed at a predetermined interval. That is, the driving shaft210may move by the predetermined interval in the radial direction.

Also, the driving shaft210is not disposed in a completely fixed state in the axial direction. That is, the driving shaft210may move in the axial direction. The axial movement of the driving shaft210will be described later in detail.

Also, as the driving shaft210rotates, the driving shaft210is floated by a pressure of the refrigerant. That is, the gas bearing means supporting the driving shaft210by the pressure of the refrigerant.

Here, an axial center when the driving shaft210normally rotates is referred to as a central axis. Before the driving shaft210rotates, the driving shaft210is disposed below the central axis by gravity. Also, as the driving shaft210rotates, it may be supported by a working fluid and disposed in line with the central axis.

Since the impellers230and240are coupled to the driving shaft210, the impellers230and240may move together with the driving shaft210. That is, since the impellers230and240move in a relatively large range according to the driving, the shrouds250and260and the impellers230and240are relatively spaced apart from each other.

Hereinafter, a space by which the first impeller230and the first shroud250are spaced apart from each other is called a first gap270. Also, a space by which the second impeller240and the second shroud260are spaced apart from each other is called a second gap280. The first gap270and the second gap280are defined to surround radially the outside of the impellers230and240.

According to the design and operation, a length of each of the first gap270and the second gap280may vary. Here, the lengths of the first gap270and the second gap280are referred to as a first gap length C1and a second gap length C2, respectively. The first gap length C1is a spaced distance between the first impeller230and the first shroud250, and the second gap length C2is a spaced distance between the second impeller240and the second shroud260.

Particularly, the first gap length C1and the second gap length C2correspond to minimally spaced distances between the first and second impellers230and240and the first and second shrouds250and260. However, this corresponds to an exemplary criterion for comparing the first gap length C1and the second gap length C2. Thus, the first gap length C1and the second gap length C2may be measured differently by different criteria.

As described above, the first and second impellers230and240and the first and second shrouds250and260are relatively largely spaced apart from each other. Thus, the first gap length C1and the second gap length C2correspond to relatively large values. Thus, an interference between the first and second impellers230and240and the first and second shrouds250and260may be prevented.

When the compressor200is driven, the first and second impellers230and240rotate, and the refrigerant is compressed. Here, leakage of the refrigerant may occur through the first gap270and the second gap280. In detail, the refrigerant compressed and discharged by the first and second impellers230and240may flow to a suction side along the first gap270and the second gap280.

Thus, an amount of refrigerant compressed and discharged is reduced, and flow resistance of the suctioned refrigerant may occur. That is, efficiency of the compressor200is deteriorated. Thus, it is necessary to minimize the first gap length C1and the second gap length C2.

In summary, in a driving stop process and a driving preparation process of the compressor200, the first gap length C1and the second gap length C2have be relatively large. Also, in a driving process of the compressor200, the first gap length C1and the second gap length C2have to be relatively small.

Hereinafter, a variation in the first gap length C1and the second gap length C2according to the process of driving the compressor200will be described.

FIGS. 4 to 6are views illustrating a process of driving the turbo compressor according to an embodiment.FIGS. 4 to 6illustrate a variation in the first gap length C1and the second gap length C2, based onFIG. 3. For convenience of description, the first gap length C1and the second gap length C2and their variations are exaggerated.

FIGS. 3 to 6illustrate the driving process of the compressor200in sequence.FIG. 3is classified as a stop process,FIG. 4is classified as a drive preparation process,FIG. 5is classified as a driving process, andFIG. 6is classified as a driving end process.

The stop process of the compressor200illustrated inFIG. 3may be understood as a state in which the flow of the refrigerant is stopped. In detail, it may be understood that the flow of the refrigerant is stabilized so as not to affect each constituent.

As illustrated inFIG. 3, in the stop process of the compressor200, the first gap length C1and the second gap length C2are provided substantially the same (C1=C2). Also, according to the design, the first gap length C1and the second gap length C2may correspond to somewhat different values.

Here, the positions of the driving shaft210and the first and second impellers230and240are referred to as reference positions. Particularly, each of the reference positions means a reference position in the axial direction. As described above, the radial movement of the driving shaft210and the first and second impellers230and240are not illustrated inFIGS. 3 to 6.

In summary, when the driving shaft210and the first and second impellers230and240are disposed at the reference positions, the first gap length C1and the second gap length C2have the same value. Also, the first gap length C1and the second gap length C2correspond to relatively large values.

The driving preparation process of the compressor200illustrated inFIG. 4may be understood as a state in which the flow of the refrigerant is generated by the rotation of the driving shaft210and the first and second impellers230and240. In detail, it may be understood that the compressor200reaches target compression of the refrigerant. That is, this is a case when the flow of the refrigerant does not yet occur normally.

As illustrated inFIG. 4, in the driving preparation process of the compressor200, the first gap length C1and the second gap length C2vary differently. In detail, the first gap length C1becomes large, and the second gap length C2becomes small. That is, the first gap length C1is larger than the second gap length C2(C1>C2).

This is because the driving shaft210and the first and second impellers230and240are moved to the second stage side from the reference position. That is to say, the driving shaft210and the first and second impellers230and240move toward the second shroud260. Thus, the second impeller240and the second shroud260are close to each other, and the first impeller230and the first shroud250are far from each other.

The movement of the driving shaft210and the first and second impellers230and240occur by the pressure difference between the first-stage side and the second-stage side. As described above, the pressure at the second-stage side is higher than that at the first-stage side. Due to the pressure difference, a difference in thrust force on rear surfaces of the first impeller230and the second impeller249occurs.

In detail, the thrust force (the left direction inFIG. 3), which pushes the first impeller230outwardly, is generated by the refrigerant compressed and discharged from the first impeller230. Also, the thrust force (the right direction inFIG. 3), which pushes the second impeller240outward in the axial direction, is generated by the refrigerant compressed and discharged from the second impeller240.

Here, the thrust force on the second impeller240is greater than thrust force on the first impeller230. Thus, the driving shaft210and the first and second impellers230and240generally move outwardly in the axial direction of the second impeller240, that is, in the right direction inFIG. 3.

This difference in thrust force may be greater as the driving shaft210and the first and second impellers230and240rotate at a high speed. Thus, the compressor200starts to be driven, and the driving shaft210and the first and second impellers230and240gradually move to the right side.

In summary, as the refrigerant flows, the driving shaft210and the first and second impellers230and240move to the second-stage side from the reference positions. Thus, the first gap length C1increases, and the second gap length C2decreases. Here, the second gap length C2may be small enough to prevent the leakage of the refrigerant, and thus the efficiency of the second stage may increase.

However, since the first gap length C1is larger, a large amount of refrigerant may leak. That is, the efficiency of the first stage side may be very deteriorated. To prevent this, the first shroud250moves in the axial direction in the compressor200according to an embodiment.

The driving process of the compressor200illustrated inFIG. 5may be understood as a state in which the compressor200is normally driven. In detail, it may be understood that the compressor200operates by reaching the target compression of the refrigerant.

As illustrated inFIG. 5, in the driving process of the compressor200, the first gap length C1and the second gap length C2are provided substantially the same (C1=C2). However, according to the design, the first gap length C1and the second gap length C2may correspond to somewhat different values.

This is because the first shroud250moves toward the first impeller230so that the first gap length C1becomes smaller. That is, the first shroud250moves to the second stage to correspond to the driving shaft210and the first and second impellers230and240, which move from the reference position to the second-stage side.

Here, for convenience of description, the movement of the driving shaft210and the first and second impellers230and240, and the movement of the first shroud250are separately illustrated inFIGS. 4 and 5. However, in practice, the movement of the driving shaft210and the first and second impellers230and240and the movement of the first shroud250may be performed at almost the same time.

That is, when the compressor200is driven, the driving shaft210, the first and second impellers230and240, and the first shroud250move together in the axial direction. Thus, the first gap length C1and the second gap length C2may be reduced to prevent the refrigerant from leaking.

The driving end process of the compressor200illustrated inFIG. 6may be understood as a process in which the driving of the compressor200is stopped. In detail, the driving end process corresponds to an intermediate process converted from the driving process ofFIG. 5to the stop process ofFIG. 3.

As the rotation of the driving shaft210and the first and second impellers230and240is stopped, the thrust force on the first and second impellers230and240is removed. Thus, the driving shaft210and the first and second impellers230and240move to the reference positions. That is, the driving shaft210and the first and second impellers230and240move to the first-stage side. Thus, the second gap length C2gradually increases.

Also, in response to the movement of the driving shaft210and the first and second impellers230and240, the first shroud250moves. The first gap length C1varies according to the moving speeds of the driving shaft210, the first and second impellers230and240, and the first shroud250.

For example, when the driving shaft210, the first and second impellers230and240, and the first shroud250move at the same speed, the first gap length C1is equally maintained. Also, according to the relative movement speed, the first gap length C1may be narrowed or widened.

As a result, each of the first gap length C1and the second gap length C2may be provided to have a length corresponding toFIG. 3. Thus, the interference between the first and second impellers230and240, the first shroud250, and the second shroud260may be prevented.

As described above, the first shroud250moves due to the axial movement of the driving shaft210and the first and second impellers230and240. Thus, the interference between the impellers230and240and the shrouds250and260may be prevented, and also, the leakage of the refrigerant may be prevented.

Hereinafter, a gap adjustment structure for moving the first shroud250will be described according to various embodiments. InFIGS. 7 to 10, the passage of the refrigerant is expressed as an arrow. For example, the arrows illustrated inFIGS. 7 to 10may be understood as refrigerant tubes through which the refrigerant flows.

FIG. 7is a view illustrating a gap adjustment structure of a turbo compressor according to a first embodiment.

As illustrated inFIG. 7, a first shroud250moves by a refrigerant discharged from a second-stage side. Here, for convenience of description, since only a flow of the refrigerant associated with movement of the first shroud250is illustrated, a flow of the refrigerant at a first-stage side is omitted.

Referring to the flow of the refrigerant at the second-stage side, a second-stage inflow passage310through which the refrigerant is suctioned into a second impeller240is provided. The refrigerant discharged from the first-stage side flows through the second-stage inflow passage310. The second-stage inflow passage310is provided in a second impeller240in an axial direction.

Also, a second-stage outflow passage330through which the refrigerant is discharged from the second impeller240is provided. A two-stage compressed refrigerant flows through the second-stage outflow passage330. Also, the two-stage outflow passage330is connected to a condenser140to supply the two-stage compressed refrigerant to the condenser140.

Here, a gap adjustment passage340branched from the second-stage outflow passage330to extend to the first-stage side is provided. In detail, the gap adjustment passage340extends toward the first shroud250. Also, the first shroud250may move toward the second-stage side in the axial direction by the refrigerant flowing into the gap adjustment passage340.

The driving process of the compressor200ofFIGS. 3 to 6will be described through the above-described structure. As the compressor200is driven, a driving shaft210and first and second impellers230and240move to the second-stage side as illustrated inFIGS. 3 to 4.

Also, inFIG. 4, the refrigerant compressed in two stages is supplied to the gap adjustment passage340to allow the first shroud250to move to the second-stage side as illustrated inFIG. 5. As a result, as the compressor200is driven, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 3 to 5.

Also, since the refrigerant having a high pressure is supplied to the first shroud250in two stages, a first gap270may be narrower. As a result, as the compressor200is driven, the first gap270and the second gap280may be narrower.

Here, the compressor200is further provided with a guide device360to guide axial movement of the first shroud250. That is, the guide device360is understood as a constituent configured to prevent the first shroud250from moving in the radial direction, not the axial direction.

Also, as the driving shaft210and the first and second impellers230and240rotate at a higher speed, the driving shaft210and the first and second impellers230and240further move. Also, the first shroud250also correspondingly moves further.

Also, as the driving of the compressor200is stopped, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 5 to 6. Also, the driving shaft210, the first and second impellers230and240and the first shroud250return to reference positions.

That is, the driving shaft210, the first and second impellers230and240, and the first shroud250move according to the pressure of the refrigerant passing through the compressor200. Thus, the driving shaft210, the first and second impellers230and240, and the first shroud250may correspond to each other to move together.

FIG. 8is a view illustrating a gap adjustment structure of a turbo compressor according to a second embodiment.

As illustrated inFIG. 8, a first shroud250moves by a refrigerant discharged from a first-stage side. Here, for convenience of description, since only a flow of the refrigerant associated with movement of the first shroud250is illustrated, a flow of the refrigerant at a second-stage side is partially omitted.

Referring to the flow of the refrigerant at the first-stage side, a first-stage inflow passage300through which the refrigerant is suctioned into a first impeller230is provided. The refrigerant discharged from an evaporator150flows to the first-stage inflow passage300. The first-stage inflow passage300is provided in a first impeller230in an axial direction.

Also, a first-stage outflow passage320through which the refrigerant is discharged from the first impeller230is provided. The first-stage compressed refrigerant flows through the first-stage outflow passage320. Also, the first stage outflow passage320is connected to the second-stage inflow passage310to supply the refrigerant compressed in one stage to the second-stage side.

Here, a gap adjustment passage350branched from the first-stage outflow passage320to extend toward the first shroud250is provided. The gap adjustment passage340ofFIG. 7and the gap adjustment passage350ofFIG. 8have the same function except that the refrigerant flowing to each other is different.

That is, the gap adjustment passage350moves the first shroud250to correspond to the driving shaft210and the first and second impellers230and240. The movement of the first shroud250and the guide device360by the gap adjustment passage350refer to the above description.

Hereinafter, differences between the gap adjustment passage340ofFIG. 7and the gap adjustment passage350ofFIG. 8will be described.

Since the gap adjusting passage340ofFIG. 7supplies the refrigerant compressed in two stages, the first shroud250receives a greater pressure. That is, since the first shroud250further moves to the second-stage side, the first gap270is relatively narrowed. Thus, the leakage of the refrigerant generated between the first impeller230and the first shroud250may be more effectively prevented.

The gap adjustment passage350ofFIG. 8is branched from the first-stage outflow passage320to extend to the first shroud250, thereby providing a simpler structure. That is, the gap adjustment passage350may be shorter in length. Thus, since an amount of refrigerant supplied to the gap adjustment passage350is small, the efficiency of the compressor200may increase.

Also, the compressor200may include the gap adjustment passage branched from the first-stage outflow passage320and the second-stage outflow passage330. That is, the refrigerant that is compressed in one stage and the refrigerant that is compressed in two stages are supplied to the first shroud250to move in the axial direction. Due to the above-described structure, an amount of refrigerant used for the movement of the first shroud250may be reduced, and the first gap length C1may be effectively reduced.

In summary, the gap adjustment passages340and350may extend from the at least one of the first-stage outflow passage320or the second-stage outflow passage330to the first shroud250.

FIG. 9is a view illustrating a gap adjustment structure of a turbo compressor according to a third embodiment.

Referring toFIG. 9, a gap adjustment passage340illustrated inFIG. 7is provided. However, this is merely an example, and the gap adjustment passage350illustrated inFIG. 8may be provided, or the gap adjustment passage branched from the first-stage outflow passage320and the second-stage outflow passage330may be provided.

The compressor200includes a gap adjustment member370coupled to a first shroud250. The gap adjustment member370corresponds to a constituent for moving the first shroud250in an axial direction. Particularly, the gap adjustment member370corresponds to an elastic member having an elastic force in the axial direction.

For example, the gap adjustment member370corresponds to a spring that is tensioned and compressed in the axial direction. Particularly, the gap adjustment member370is disposed outside the first shroud250in the axial direction together with one end of the gap adjustment passage350.

The driving process of the compressor200ofFIGS. 3 to 6will be described through the above-described structure. As the compressor200is driven, a driving shaft210and first and second impellers230and240move to the second-stage side as illustrated inFIGS. 3 to 4.

Also, inFIG. 4, the refrigerant compressed in two stages is supplied to the gap adjustment passage340to allow the first shroud250to move to the second-stage side as illustrated inFIG. 5. Here, the gap adjustment member370is tensioned in the axial direction. That is, the refrigerant flowing into the gap adjustment passage340acts as an external force, and thus, the gap adjustment member370may be tensioned.

As a result, as the compressor200is driven, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 3 to 5.

Also, as the driving of the compressor200is stopped, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 5 to 6. Also, the driving shaft210, the first and second impellers230and240and the first shroud250return to reference positions.

Here, the elastic force is applied to the first shroud250by the gap adjustment member370. That is, as the external force generated by the gap adjustment passage340disappears, the gap adjustment member340is compressed in the axial direction to return.

Thus, the first shroud250may move faster than the driving shaft210and the first and second impellers230and240. As a result, the first gap length C1may be more largely secured, and an interference between the first impeller230and the first shroud250may be prevented.

FIG. 10is a view illustrating a gap adjustment structure of a turbo compressor according to a fourth embodiment.

Referring toFIG. 10, a gap adjustment passage340illustrated inFIG. 7is provided. However, this is merely an example, and the gap adjustment passage350illustrated inFIG. 8may be provided, or the gap adjustment passage branched from the first-stage outflow passage320and the second-stage outflow passage330may be provided.

The compressor200includes a gap adjustment member380coupled to a first shroud250. The gap adjustment member380corresponds to a constituent for moving the first shroud250in an axial direction. Here, the gap adjustment member380may correspond to a thermal expansion member having a large thermal expansion coefficient.

For example, the gap adjustment member380may correspond to a polymer attached to one side of the first shroud250. Particularly, the gap adjustment member380may be disposed to cover an outer surface of the first shroud250in the axial direction. Thus, the refrigerant flowing through the gap adjustment passage350may be directly supplied to the gap adjustment member380.

The driving process of the compressor200ofFIGS. 3 to 6will be described through the above-described structure. As the compressor200is driven, a driving shaft210and first and second impellers230and240move to the second-stage side as illustrated inFIGS. 3 to 4.

Also, inFIG. 4, the refrigerant compressed in two stages is supplied to the gap adjustment passage340to allow the first shroud250to move to the second-stage side as illustrated inFIG. 5. Here, the two-stage compressed refrigerant has a high temperature as well as a high pressure. As a result, the gap adjustment member380may be expanded to move the first shroud250further.

As a result, as the compressor200is driven, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 3 to 5. Here, the first shroud250further moves by the gap adjustment member380so that the first gap270is narrower.

Also, as the driving of the compressor200is stopped, the driving shaft210, the first and second impellers230and240, and the first shroud250move as illustrated inFIGS. 5 to 6. Here, the gap adjustment member380may be contracted, and the first shroud250may move.

Hereinafter, differences between the gap adjustment passage370ofFIG. 9and the gap adjustment passage380ofFIG. 10will be described.

The gap adjustment member370ofFIG. 9has a function of returning the first shroud250more quickly when the driving of the compressor200is stopped. Also, the gap adjustment member370applies an external force to the first shroud250in a direction away from the first impeller230. Thus, the first impeller230and the first shroud250may be prevented from interfering with each other even in an emergency situation due to instability of the refrigerant.

The gap adjustment member380ofFIG. 10functions of moving the first shroud250so that the first gap270is narrowed. Thus, the leakage of the refrigerant between the first impeller230and the first shroud250may be effectively prevented. Also, the gap adjustment member380may be provided to cover one surface of the first shroud250to prevent the refrigerant supplied to the gap adjustment passage to directly affecting the first shroud250.

In summary, the compressor200includes a gap adjustment passage or a gap adjustment passage and a gap adjustment member, by which the first shroud250moves. The gap adjustment passage corresponds to a constituent in which the first shroud250moves by the refrigerant flowing through the compressor200. Also, the gap adjustment member corresponds to a constituent for moving the first shroud250in addition to the gap adjusting passage.

The first gap270may be effectively adjusted by the movement of the first shroud250as described above. Thus, the interference between the impeller and the shroud may be prevented, and also, the leakage of the refrigerant may be prevented.

The turbo compressor including the above-described constituents according to the embodiment may have the following effects.

The flowing refrigerant generated by the driving may be moved to without providing the separate power source to effectively adjust the gap between the impeller and the shroud.

In detail, in the process of stopping the driving of the compressor, the gap between the impeller and the shroud may be widened to prevent the impeller and the shroud from interfering with each other. Thus, each of the components may be prevented from being damaged.

In addition, in the process of driving the compressor, the gap between the impeller and the shroud may be narrowed to prevent the refrigerant from leaking between the impeller and the shroud. Therefore, the compression efficiency may be improved.

Particularly, the shroud may be more efficiently moved by using gap adjustment member coupled to the shroud as well as the gap adjustment passage through which the compressed refrigerant is provided to the shroud.