Centrifugal compressor and volute thereof

Abstract

The application provides a centrifugal compressor and a volute thereof. The volute comprises a volute body, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover and a second end cover, a first end cover

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of compressors, in particular to a centrifugal compressor and a volute thereof. BACKGROUND

[0002] Centrifugal compressors have the advantages of energy saving, high efficiency, stable operation and long service life. However, in the field of refrigeration, centrifugal compressors are suitable for large flow and low pressure ratio working occasions, and it is difficult to achieve high efficiency small flow and high pressure ratio operation. Therefore, centrifugal compressors are applied to large-capacity water chillers. Small and medium-sized refrigeration systems use screw compressors, scroll compressors (such as small central air conditioners, including multi-connected machines) and rolling rotor compressors more. However, the operating efficiency of these types of compressors is far lower than that of centrifugal compressors. Moreover, most of these types of compressors use lubricating oil for lubrication. It is very easy to cause the accumulation of lubricating oil in the heat exchanger, which leads to the difficulty of returning oil to the compressor, the poor lubrication of the compressor-related components, and the large heat transfer resistance of the heat exchanger.

[0003] Therefore, how to solve the various problems caused by the miniaturization of centrifugal compressors and enable them to be applied to small and medium-sized refrigeration systems to replace screw compressors, scroll compressors and even rolling rotor compressors will make the energy efficiency of these refrigeration systems higher and have a profound impact on the refrigeration industry. SUMMARY

[0004] An object of the present application is to provide a centrifugal compressor and a volute thereof to solve or at least partially solve the above-mentioned problems existing in the prior art.

[0005] An object of the present application is to provide a volute with higher precision of the inner surface of the flow channel.

[0006] In one aspect, the present application provides a volute for a centrifugal compressor, comprising:

[0007] a volute body comprising a cylinder and an exhaust pipe connected to the peripheral wall of the cylinder, the exhaust pipe defining an exhaust flow channel communicating with the interior of the cylinder;

[0008] a first end cover and a second end cover embedded side by side in the cylinder along the axial direction of the cylinder, the first end cover being provided with an inlet flow channel, and the second end cover being provided with a mounting hole for mounting a centrifugal impeller; and

[0009] the first end cover and the second end cover jointly define a volute flow channel surrounding the outer periphery of the mounting hole, the inlet flow channel extends along the axial direction of the volute body and is opposite to the inlet of the centrifugal impeller, and the exhaust flow channel communicates with the outlet of the volute flow channel for discharging the gas flow compressed by the centrifugal impeller.

[0010] Optionally, the end faces of the first end cover and the second end cover are each provided with a volute flow channel groove, and the two volute flow channel grooves are joined together to form the volute flow channel.

[0011] Optionally, one of the first end cover and the second end cover is provided with a volute flow channel groove, and the other end surface covers the volute flow channel groove to define the volute flow channel.

[0012] Optionally, the first end cover and the second end cover are fastened by screws.

[0013] Optionally, the outer end surfaces of the first end cover and the second end cover are flush with the axial end surfaces of the cylinder.

[0014] Optionally, the inner circumferential surface of the cylinder, the outer circumferential surface of the first end cover and the outer circumferential surface of the second end cover are all cylindrical surfaces.

[0015] Optionally, the exhaust pipe is detachably mounted on the cylinder.

[0016] Optionally, the volute flow channel is flat in the thickness direction and parallel to the axial direction of the volute casing, and gradually transitions from the flat shape to a cylindrical shape along the direction of the gas flow.

[0017] In another aspect, the present application also provides a centrifugal compressor comprising a volute casing, which is the volute casing according to any one of the above.

[0018] Optionally, the centrifugal compressor further comprises a casing, a motor and at least one compression unit. The motor is mounted in the casing; each compression unit comprises a volute casing and a centrifugal impeller, the volute casing is mounted in the casing, and the centrifugal impeller is mounted in the volute casing and configured to rotate under the drive of the motor to compress the gas flow entering the volute casing and discharge to the volute flow channel.

[0019] The volute casing of the present application is of a split structure, which solves the problem that the internal flow channel surface of the existing one-piece cast volute casing is not easy to be surface finished. The volute flow channel of the volute casing is defined by the first end cover and the second end cover which are detachably connected, so that the internal surface of the volute flow channel can be surface finished and the corner at the junction can be rounded when the first end cover and the second end cover are respectively manufactured, so that the surface is smoother and the internal flow field distribution is more uniform, the flow loss caused by the too rough surface of the flow channel is reduced, and the operation efficiency of the centrifugal compressor is improved, which is beneficial to the miniaturization of the centrifugal compressor.

[0020] Moreover, the volute casing is split into the volute casing body, the first end cover and the second end cover, so that the shape and the opening of each part are very simple and regular, the processing and forming are very convenient, and the internal wall of the flow channel is fully exposed, so that the surface finishing operation of the flow channel surface is very convenient.

[0021] Further, compared with the conventional centrifugal compressor, the centrifugal compressor of the present application omits the diffuser and directly installs the centrifugal impeller in the volute to avoid the large swirl in the diffuser to cause large diffuser loss, so that the overall efficiency of the compressor is improved, and the structure of the centrifugal compressor is more compact. Therefore, this structure is beneficial to realize the miniaturization of the centrifugal compressor, and makes it maintain high efficiency, so as to be suitable for application in small water chillers or small central air conditioners such as multi-connected machines.

[0022] Further, the centrifugal compressor of the present application can adopt radial magnetic suspension bearing and axial magnetic suspension bearing. The magnetic suspension bearing is oil-free bearing, so that it is not necessary to add lubricating oil in the centrifugal compressor, thereby completely avoiding the oil return problem of the compressor in the small and medium-sized refrigeration system (the conventional screw compressor, scroll compressor and rolling rotor compressor are basically oil-lubricated), improving the heat exchange efficiency of the heat exchanger; and the mechanical wear is small, the energy consumption is low, the noise is small, the stability of the whole machine is enhanced, and the service life is longer.

[0023] Further, the centrifugal compressor of the present application makes the thickness direction of the volute-shaped flow passage defined by the volute parallel to the axial direction of the centrifugal impeller to be flat, so that the volute is flattened as a whole, which is beneficial to realize the miniaturization of the compressor. More importantly, the gas outlet passage gradually transitions from flat to cylindrical from the joint with the volute-shaped flow passage to the outlet of the volute. In this way, the gas flow has very good diffuser effect when entering the cylindrical and more spacious gas outlet passage from the thin and flat volute-shaped flow passage. Moreover, since the gas outlet passage gradually transitions from flat to cylindrical from the joint with the volute-shaped flow passage to the outlet of the volute, the transition is very smooth, which reduces unnecessary resistance loss of the gas flow, and the cylindrical shape is also suitable for connection with the downstream pipeline.

[0024] The above and other objects, advantages and features of the present application will become more apparent from the following detailed description of some embodiments thereof, when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] Some specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. The same reference numbers in the drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that the drawings are not necessarily drawn to scale. In the drawings:

[0026] Figure 1 is a structural schematic view of a volute of an embodiment of the present application;

[0027] Figure 2 is Figure 1 is an exploded schematic view of the volute shown in FIG. 8;

[0028] Figure 3 isFigure 2 A schematic diagram of the structure of the first end cap in the volute shown;

[0029] Figure 4 yes Figure 2 The diagram shows the structure of the second end cap in the volute.

[0030] Figure 5 This is a schematic diagram of the centrifugal impeller in a centrifugal compressor according to an embodiment of the present invention;

[0031] Figure 6 yes Figure 5 A schematic diagram of the blade profile of the centrifugal impeller shown;

[0032] Figure 7 yes Figure 5 An exploded view of the centrifugal impeller shown.

[0033] Figure 8 yes Figure 7 A schematic diagram of the structure of the second impeller body. Detailed Implementation

[0034] The following reference Figures 1 to 8 The centrifugal compressor and its volute 100 according to embodiments of the present invention are described below. In some figures, the x-axis indicates the axial direction of the volute 100 and the centrifugal impeller 200; solid arrows indicate the airflow direction.

[0035] Figure 1 This is a schematic diagram of the structure of the volute 100 according to an embodiment of the present invention; Figure 2 yes Figure 1 An exploded view of the volute 100 shown; Figure 3 yes Figure 2 A schematic diagram of the structure of the first end cap 130 in the volute 100 shown; Figure 4 yes Figure 2 A schematic diagram of the structure of the second end cap 140 in the volute 100 shown.

[0036] like Figures 1 to 4 As shown, the volute 100 of this embodiment generally includes a volute body 110, a first end cap 130, and a second end cap 140. The volute body 110 includes a cylindrical body 111 and an exhaust pipe 112 connected to the peripheral wall of the cylindrical body 111. The exhaust pipe 112 defines an air outlet passage 103 communicating with the interior of the cylindrical body 111.

[0037] The first end cover 130 and the second end cover 140 are embedded in the cylinder body 111 in parallel along the axial direction (x-axis direction) of the cylinder body 111, the first end cover 130 is provided with the inlet flow channel 101, and the second end cover 140 is provided with a mounting hole 141 for mounting the centrifugal impeller. The first end cover 130 and the second end cover 140 jointly define a volute flow channel 102 surrounding the outer periphery of the mounting hole 141, the inlet flow channel 101 extends along the axial direction of the volute body 110 and is opposite to the inlet of the centrifugal impeller, and the outlet flow channel 103 is communicated with the outlet of the volute flow channel 102 for discharging the airflow compressed by the centrifugal impeller.

[0038] The volute in the prior art is usually integrally cast, and the inner flow channel surface is not easy to process during the machining process, so that the surface roughness is high, the flow field near the flow channel surface is affected, and the efficiency of the centrifugal compressor is affected. The volute 100 is designed as a split structure in the embodiment of the application, which solves this problem.

[0039] The volute flow channel 102 of the volute 100 is jointly defined by the first end cover 130 and the second end cover 140 which are detachably connected in the embodiment of the application, so that the inner surface of the volute flow channel 102 is surface finished and the corner is rounded when the first end cover 130 and the second end cover 140 are respectively manufactured, the surface is smoother, the internal flow field distribution is more uniform, and the flow loss caused by the too rough flow channel surface is reduced. Therefore, the operation efficiency of the centrifugal compressor is improved, which is beneficial to the miniaturization of the centrifugal compressor. Furthermore, the volute 100 is split into the volute body 110, the first end cover 130 and the second end cover 140 in the embodiment of the application, so that the shape and the opening of each part are very simple and regular, the machining of each part itself is very convenient, the inner wall of the flow channel is fully exposed, and the surface finishing operation of the flow channel surface is very convenient.

[0040] In some embodiments, the inner circumferential surface of the cylinder body 111, the outer circumferential surface of the first end cover 130 and the second end cover 140 can be cylindrical surfaces, so as to facilitate the machining. The exhaust pipe 112 can be detachably mounted on the cylinder body 111, so as to facilitate the fine grinding of the inner circumferential surface of the cylinder body 111.

[0041] The first end cover 130 and the second end cover 140 can be fastened by screw connection. Further, the positions of the first end cover 130 and the second end cover 140 can be positioned by using pins and pin holes, so that the mounting positions are more accurate. The outward end faces of the first end cover 130 and the second end cover 140 are flush with the axial end faces of the cylinder body 111, so that the positions of the first end cover 130 and the second end cover 140 are more stable and are not easily affected by the outside. The first end cover 130 and the second end cover 140 and the cylinder body 111 can be fixed by screws or other ways, which will not be described herein.

[0042] In some embodiments, asFigures 1 to 4 As shown, each of the end faces of the first end cap 130 and the second end cap 140 that can fit together is provided with a spiral flow channel groove 1021 and 1022, and the two spiral flow channel grooves 1021 and 1022 are joined together to form a spiral flow channel 102.

[0043] In other embodiments, one of the first end cap 130 and the second end cap 140 may have a spiral flow channel groove, while the end face of the other end cap may cover the flow channel groove to define the aforementioned spiral flow channel 102. This eliminates the need for a spiral flow channel groove, simplifying the manufacturing process.

[0044] In some embodiments, such as Figures 2 to 4 As shown, the volute 102 can be flattened with its thickness direction parallel to the axial direction of the volute 100, meaning the flow cross-section is a long rectangular strip. Along the airflow direction, the outlet airflow channel 103 gradually transitions from a flattened shape adapted to the volute 102 to a cylindrical shape. The flattened volute 102 flattens the entire volute 100, facilitating a reduction in the axial dimension of the centrifugal compressor and enabling compressor miniaturization. More importantly, because the outlet airflow channel 103 gradually transitions from flat to cylindrical, the airflow experiences excellent diffusion as it enters the cylindrical, wider outlet airflow channel 103 from the thinner, flattened volute 102. Furthermore, the smooth transition from flat to cylindrical shape reduces unnecessary airflow resistance losses, and the cylindrical shape is also suitable for connection to downstream pipes.

[0045] In another aspect, the present invention provides a centrifugal compressor. The volute of the centrifugal compressor is the volute 100 of any of the above embodiments.

[0046] Furthermore, the centrifugal compressor also includes a housing, a motor, and at least one compression unit.

[0047] The casing defines a receiving space, and the motor is mounted inside the casing. The motor includes a stator and a rotor; the stator is fixed to the casing, and the rotor can rotate relative to the stator. The number of compression units can be one or more. For example, the centrifugal compressor can be a single-stage compression type, with only one compression unit. Alternatively, the centrifugal compressor can be a multi-stage compression type, with multiple compression units. Each compression unit includes a volute 100 mounted in the casing and a centrifugal impeller 200 disposed within the volute 100. The centrifugal impeller 200 is configured to rotate under the drive of the motor to compress the airflow entering the volute 100 and discharge it into the volute channel 102, finally exiting from the outlet through the volute 100.

[0048] Traditional centrifugal compressors typically have a diffuser downstream of the centrifugal impeller in each stage. The centrifugal impeller discharges the airflow into the diffuser, and the airflow is diffused by the diffuser before entering the volute 100.

[0049] Compared with the conventional centrifugal compressor, the centrifugal compressor of the present application omits the diffuser, and directly installs the centrifugal impeller 200 in the volute 100, so as to avoid the large swirl in the diffuser and the relatively large diffuser loss caused thereby, so that the overall efficiency of the centrifugal compressor is improved, and the structure of the centrifugal compressor is more compact. Therefore, the structure is conducive to the miniaturization of the centrifugal compressor, and the centrifugal compressor maintains high efficiency, so as to be suitable for application in small water chillers or small central air conditioners such as multi-connected machines.

[0050] In some embodiments, the centrifugal compressor further comprises at least one radial magnetic suspension bearing and / or at least one axial magnetic suspension bearing installed in the casing to support the rotor of the motor. The centrifugal compressor further comprises an axial magnetic suspension bearing to offset the axial force generated by the centrifugal impeller movement to the rotor. The magnetic suspension bearing is made of magnetic suspension principle, and is an oil-free bearing. Therefore, it is not necessary to add lubricating oil in the centrifugal compressor, so as to completely avoid the oil return problem of the compressor in a small and medium-sized refrigeration system (the conventional screw compressor, scroll compressor and rolling rotor compressor are basically oil-lubricated), and the heat exchange efficiency of the heat exchanger is improved. Moreover, the use of the magnetic suspension bearing makes the centrifugal compressor have small mechanical wear, low energy consumption, small noise, enhanced stability and longer service life.

[0051] Further, the two planes in the thickness direction of the volute flow passage 102 and the circumferential volute side can be transitioned with a round corner, so as to increase the strength of the volute, relieve the local stress concentration, eliminate the corner vortex, and ensure the uniformity of the flow field. The round corner radius can be selected according to the thickness of the volute flow passage 102. The split structure of the volute 100 facilitates the machining of the round corner.

[0052] Figure 5 is a structural schematic view of the centrifugal impeller 200 in the centrifugal compressor of an embodiment of the present application; Figure 6 is Figure 5 is a blade profile schematic view of the centrifugal impeller 200 shown in

[0053] In some embodiments, the thickness of the volute flow passage 102 is greater than the outlet width of the centrifugal impeller 200. The thickness of the volute flow passage 102 refers to the dimension of the volute flow passage 102 in the direction of the axis (x-axis) of the centrifugal impeller 200, and the outlet width B of the centrifugal impeller 200 refers to the dimension of the outlet 202 of the centrifugal impeller 200 in the direction of the axis of the centrifugal impeller 200, which is specifically marked in Figure 5 Specifically, the inventors have confirmed through multiple tests that the ratio of the thickness of the volute flow passage 102 to the outlet width of the centrifugal impeller 200 is between 1.5 and 2, and the optimal effect can be achieved.

[0054] The inventor realizes that directly discharging the centrifugal impeller 200 to the volute 100 will result in an increase in the Mach number of the airflow, a large centrifugal effect of the airflow and accumulation to the radial outside, resulting in an uneven flow field and causing large flow loss. To eliminate or at least alleviate the above-mentioned adverse effects, the embodiment of the present application particularly makes the thickness of the volute flow passage 102 greater than the outlet width B of the centrifugal impeller 200, so that the airflow expands and slows down after entering the volute 100 (the volute flow passage 102), the Mach number decreases, the centrifugal effect decreases, and finally the uniformity of the flow field at the outlet of the volute 100 is significantly increased, and finally the efficiency of the compressor is improved.

[0055] In some embodiments, the centrifugal impeller 200 is a strong back-curved closed impeller. As shown in Figure 6 , the centrifugal impeller 200 has a plurality of blades 203 arranged circumferentially along the centrifugal impeller 200, and each adjacent two blades 203 forms a flow passage 212. The airflow enters the radial inside of each flow passage 212 through the inlet 201 of the centrifugal impeller 200, rotates through the centrifugal impeller 200, and flows to the radial outside of each flow passage to flow out of the centrifugal impeller 200 and flow to the volute flow passage 102 of the volute 100. During this period, each blade 203 does work on the airflow to increase the pressure of the airflow. Figure 6 The arrow indicates the rotation direction of the centrifugal impeller 200. Each blade 203 of the centrifugal impeller 200 is a back-curved structure, and the blade end (the end close to the radial outer edge of the centrifugal impeller 200) is bent backward compared to the rest of the section, so that each blade of the centrifugal impeller 200 forms a strong back-curved structure, as shown in Figure 6 .

[0056] The embodiment of the present application makes the centrifugal impeller 200 a strong back-curved type, so that the work done by the centrifugal impeller 200 on the airflow is more converted into static pressure increase and less converted into speed increase. Because the absolute airflow angle at the outlet of the strong back-curved centrifugal impeller is large, if a traditional diffuser is used, it will result in a larger airflow vorticity and larger diffuser loss. The embodiment of the present application directly connects the centrifugal impeller 200 to the volute 100 with the special design of the volute 100 as described above, which can effectively avoid this problem. As can be seen, the improvements of the embodiment of the present application are not isolated from each other, but work together. Specifically, the embodiment of the present application comprehensively installs the centrifugal impeller 200 directly in the volute 100, specially designs the flow passage of the volute 100, and combines these improvements of the strong back-curved centrifugal impeller 200, not only obtains the beneficial effects of each structural improvement, but also greatly avoids the adverse effects of each, so that the overall efficiency of the centrifugal compressor is higher, and the structure is more compact, which is beneficial to miniaturization.

[0057] Figure 7 is Figure 5 the exploded view of the centrifugal impeller 200 shown in Figure 8 is Figure 7 the structural view of the second impeller body 220 in

[0058] In some embodiments, such as Figures 6 to 8 As shown, the centrifugal impeller 200 can be a split type. Specifically, the centrifugal impeller 200 includes a first impeller body 210 and a second impeller body 220. Both the first impeller body 210 and the second impeller body 220 are disc-shaped and connected together. Each of their opposing surfaces has a blade half formed thereon, and the blade half of each impeller body is connected to form a complete blade 203.

[0059] The first impeller body 210 and the second impeller body 220 can be connected and fastened by multiple fasteners such as rivets 230. One or more positioning grooves 2113 can be formed on the first impeller body 210, and the same number of positioning protrusions 2214 can be formed on the second impeller body 220. Each positioning protrusion 2214 is engaged in a positioning groove 2113, making the position between the first impeller body 210 and the second impeller body 220 more stable, and making the alignment between the blade halves more precise, thus preventing misalignment of the blades 203 from affecting the performance of the centrifugal impeller 200.

[0060] The first impeller body 210 is provided with a rotating shaft 214, with a mounting hole 215 formed in the center for connection to the rotor by a screw 300. The second impeller body 220 is provided with the inlet 201 of the centrifugal impeller 200. Traditional centrifugal impellers are all integrally cast, and their surface precision is not ideal, which affects their compression efficiency and causes undesirable noise. Especially for closed impellers, where the blades are inside, it is even more difficult to guarantee the surface precision of the blades. In this embodiment, the centrifugal impeller 200 is set as described above as a split type, so that the two impeller bodies are manufactured separately, and the blades of each impeller body are exposed to allow for surface treatment to make them smoother.

[0061] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A volute casing for a centrifugal compressor, characterized in that... include: The volute body includes a cylindrical body and an exhaust pipe connected to the peripheral wall of the cylindrical body, wherein an air outlet passage communicating with the interior of the cylindrical body is defined within the exhaust pipe. A first end cap and a second end cap are fitted side-by-side inside the cylinder along its axial direction. The first end cap has an air inlet channel, and the second end cap has a mounting hole for installing a centrifugal impeller. The first end cap and the second end cap together define a volute flow channel surrounding the outer periphery of the mounting hole. The inlet flow channel extends axially along the volute body and is opposite to the inlet of the centrifugal impeller. The outlet flow channel communicates with the outlet of the volute flow channel to discharge the airflow compressed by the centrifugal impeller. One of the first end cap and the second end cap has a volute-shaped flow channel groove, and the end face of the other end cap covers the volute-shaped flow channel groove to define the volute-shaped flow channel. The volute flow channel is flat, with its thickness direction parallel to the axial direction of the volute shell; and Along the airflow direction, the outlet airflow channel gradually transitions from a flat shape adapted to the volute flow channel to a cylindrical shape; The outward-facing end faces of the first end cap and the second end cap are flush with the axial end faces of the cylinder, respectively.

2. The volute according to claim 1, characterized in that, The first end cap and the second end cap are fastened together by screws.

3. The volute according to claim 1, characterized in that, The inner circumferential surface of the cylinder, the outer circumferential surface of the first end cap, and the outer circumferential surface of the second end cap are all cylindrical surfaces.

4. The volute according to claim 1, characterized in that, The exhaust pipe is detachably installed on the cylinder.

5. A centrifugal compressor, comprising a volute, characterized in that... The volute is the volute as described in any one of claims 1 to 4.

6. The centrifugal compressor according to claim 5, characterized in that... include: chassis; The motor is installed inside the housing; and At least one compression unit, each of the compression units including a volute and a centrifugal impeller, the volute being mounted in the housing, the centrifugal impeller being mounted inside the volute, the centrifugal impeller being configured to rotate under the drive of the motor to compress the airflow entering the volute and discharge it into the volute channel.

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