CN114542487A - Centrifugal compressor and volute thereof - Google Patents

Abstract

The invention provides a centrifugal compressor and a volute thereof. The volute comprises a volute body, wherein the volute body comprises a cylinder body and an exhaust pipe connected to the peripheral wall of the cylinder body, and an exhaust flow passage communicated with the inside of the cylinder body is defined in the exhaust pipe; the first end cover and the second end cover are embedded and fixed in the cylinder body side by side along the axial direction of the cylinder body, the first end cover is provided with an air inlet channel, and the second end cover is provided with a mounting hole for mounting a centrifugal impeller; and the first end cover and the second end cover jointly define a volute flow channel surrounding the periphery of the mounting hole, the air inlet flow channel extends along the axial direction of the volute body and is opposite to the inlet of the centrifugal impeller, and the air outlet flow channel is communicated with the outlet of the volute flow channel so as to be used for discharging airflow compressed by the centrifugal impeller. The invention is beneficial to finish machining the inner surface of the volute flow channel.

Description

Centrifugal compressor and volute thereof

Technical Field

The invention relates to the technical field of compressors, in particular to a centrifugal compressor and a volute thereof.

Background

The centrifugal compressor has the remarkable advantages of energy conservation, high efficiency, stable operation and long service life. However, in the refrigeration field, the centrifugal compressor is suitable for large-flow and low-pressure-ratio working occasions, and the efficient low-flow and high-pressure-ratio operation is difficult to realize. Therefore, the centrifugal compressor is applied to a large-cooling-capacity water chilling unit. Medium and small-sized refrigeration systems are increasingly using screw compressors, scroll compressors (such as small central air conditioners including multi-split air conditioners) and rolling rotor compressors. These types of compressors, however, operate far less efficiently than centrifugal compressors. Most of these compressors are lubricated with lubricating oil. The problems that the lubricating oil is accumulated in the heat exchanger, the oil is not returned to the compressor, the lubrication of parts related to compression is poor, the heat exchange resistance of the heat exchanger is increased and the like are easily caused.

Therefore, how to solve various problems caused by the miniaturization of the centrifugal compressor can make the centrifugal compressor applied to small and medium-sized refrigeration systems to replace screw compressors, scroll compressors and even rolling rotor compressors, so that the energy efficiency of the refrigeration systems is higher, and the refrigeration industry is influenced profoundly.

Disclosure of Invention

An object of the present invention is to provide a centrifugal compressor and a volute thereof, which solve or at least partially solve the above problems of the prior art.

The invention aims to provide a volute with higher accuracy of the inner surface of a flow channel.

In one aspect, the present invention provides a volute for a centrifugal compressor, comprising:

the volute body comprises a cylinder and an exhaust pipe connected to the peripheral wall of the cylinder, and an exhaust flow passage communicated with the inside of the cylinder is defined in the exhaust pipe;

the first end cover and the second end cover are embedded and fixed in the cylinder body side by side along the axial direction of the cylinder body, the first end cover is provided with an air inlet channel, and the second end cover is provided with a mounting hole for mounting a centrifugal impeller; and is

The first end cover and the second end cover jointly define a volute flow channel surrounding the periphery of the mounting hole, the air inlet flow channel extends along the axial direction of the volute body and is opposite to an inlet of the centrifugal impeller, and the air outlet flow channel is communicated with an outlet of the volute flow channel and is used for discharging airflow compressed by the centrifugal impeller.

Optionally, the end faces of the first end cover and the second end cover, which are attached to each other, are respectively provided with a volute flow channel groove, and the two volute flow channel grooves are spliced into a volute flow channel.

Optionally, one of the first end cover and the second end cover is provided with a spiral runner groove, and the end face of the other end cover covers the spiral runner groove to define a spiral runner.

Optionally, the first end cap and the second end cap are fastened by a screw connection.

Optionally, the outward end faces of the first end cover and the second end cover are flush with the two axial end faces of the cylinder respectively.

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

Optionally, the exhaust tube is removably mounted to the barrel.

Optionally, the volute flow channel is flat with the thickness direction parallel to the axial direction of the volute; and along the air flow flowing direction, the air outlet flow channel gradually transits from a flat shape matched with the volute flow channel to a cylinder shape.

In another aspect, the present invention also provides a centrifugal compressor, including a volute, which is a volute according to any one of the above.

Optionally, the centrifugal compressor further comprises a casing, a motor and at least one compression unit. The motor is arranged in the shell; each compression unit comprises a volute and a centrifugal impeller, the volute is mounted on the machine shell, the centrifugal impeller is mounted in the volute, and the centrifugal impeller is configured to rotate under the driving of the motor so as to compress airflow entering the volute and is arranged to the volute flow channel.

The volute is of a split structure, and the problem that the surface of the internal flow channel of the existing integrally cast volute is difficult to finish is solved. The volute flow channel of the volute is limited by the first end cover and the second end cover which are detachably connected, so that when the first end cover and the second end cover are manufactured respectively, the surface of the inner surface of the volute flow channel is subjected to surface finish machining, and the included angle is chamfered, so that the surface of the volute flow channel is smoother, the distribution of an internal flow field is more uniform, the flow loss caused by the fact that the surface of the flow channel is too rough is reduced, the operating efficiency of a centrifugal compressor is improved, and the miniaturization of the centrifugal compressor is facilitated.

In addition, the volute is divided into the volute 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 the forming are very convenient, the inner wall of the flow channel is favorably and fully exposed, and the fine machining operation on the surface of the flow channel is very convenient.

Furthermore, compared with the traditional centrifugal compressor, the centrifugal compressor provided by the invention omits a diffuser, and the centrifugal impeller is directly installed in the volute, so that the problem that the rotation degree of the airflow in the diffuser causes large diffusion loss is avoided, the overall efficiency of the compressor is improved, and the structure of the centrifugal compressor is more compact. Therefore, this configuration is advantageous for achieving a compact centrifugal compressor, and is suitable for application to a small central air conditioner such as a small chiller or a multi-split air conditioner, while maintaining high efficiency.

Furthermore, the centrifugal compressor can adopt a radial magnetic suspension bearing and an axial magnetic suspension bearing, and the magnetic suspension bearing is an oilless bearing, so that lubricating oil does not need to be added into the centrifugal compressor, the oil return problem of the compressor of a medium and small refrigeration system is thoroughly avoided (a screw compressor, a scroll compressor and a rolling rotor compressor which are conventionally adopted are basically lubricated by oil), and the heat exchange efficiency of the heat exchanger is improved; and the mechanical abrasion 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.

Furthermore, the volute flow channel defined by the volute is flat in the thickness direction parallel to the axial direction of the centrifugal impeller, and the flat volute flow channel enables the volute to be flat integrally, so that the compressor is favorably miniaturized. More importantly, the air outlet flow channel is gradually transited from a flat shape to a cylindrical shape from the joint of the air outlet flow channel and the volute flow channel to the outlet of the volute. Therefore, the air flow enters the cylindrical and wide air outlet flow channel from the thin and flat volute flow channel, and the excellent diffusion effect can be achieved. And because the air outlet flow channel gradually transits from the flat shape to the cylindrical shape from the joint of the air outlet flow channel and the volute flow channel to the outlet of the volute, the transition is smooth, the unnecessary resistance loss of the air flow is reduced, and meanwhile, the cylindrical shape is also suitable for being connected with a downstream pipeline.

The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.

Drawings

Some specific embodiments of the invention will be described in detail hereinafter, by way of illustration and not limitation, with reference to the accompanying drawings. The same reference numbers in the drawings identify the same or similar elements or components. Those skilled in the art will appreciate that the drawings are not necessarily drawn to scale. In the drawings:

FIG. 1 is a schematic diagram of the structure of a volute of one embodiment of the present invention;

FIG. 2 is an exploded schematic view of the volute of FIG. 1;

FIG. 3 is a schematic structural view of a first end cover in the volute of FIG. 2;

FIG. 4 is a schematic structural view of the second end cover in the volute of FIG. 2;

FIG. 5 is a schematic structural view of a centrifugal impeller in a centrifugal compressor according to an embodiment of the present invention;

FIG. 6 is a blade profile schematic of the centrifugal impeller of FIG. 5;

FIG. 7 is an exploded schematic view of the centrifugal impeller of FIG. 5;

fig. 8 is a schematic structural view of the second impeller body in fig. 7.

Detailed Description

A centrifugal compressor and a scroll 100 thereof according to an embodiment of the present invention will be described with reference to fig. 1 to 8. The axial directions of the volute 100 and the centrifugal impeller 200 are indicated by an x-axis in the partial drawing; the direction of airflow is indicated by the solid arrows.

FIG. 1 is a schematic diagram of the construction of a volute 100 according to one embodiment of the invention; FIG. 2 is an exploded schematic view of the volute 100 of FIG. 1; FIG. 3 is a schematic view of the first end cap 130 of the volute 100 of FIG. 2; fig. 4 is a schematic view of the second end cap 140 in the volute 100 of fig. 2.

As shown in fig. 1-4, a volute 100 of an embodiment of the present invention may generally include a volute body 110, a first end cap 130, and a second end cap 140. The volute body 110 includes a cylinder 111 and an exhaust pipe 112 connected to a peripheral wall of the cylinder 111, and the exhaust pipe 112 defines therein an outlet flow passage 103 communicating with an interior of the cylinder 111.

The first end cap 130 and the second end cap 140 are embedded in the cylinder 111 side by side along an axial direction (x-axis direction) of the cylinder 111, the first end cap 130 is provided with an intake runner 101, and the second end cap 140 is provided with a mounting hole 141 for mounting a centrifugal impeller. The first end cover 130 and the second end cover 140 together define a volute 102 surrounding the periphery of the mounting hole 141, the inlet flow passage 101 extends in the axial direction of the volute body 110 and is opposite to the inlet of the centrifugal impeller, and the outlet flow passage 103 is communicated with the outlet of the volute 102 for discharging the airflow compressed by the centrifugal impeller.

In the prior art, the volute is usually cast integrally, and the surface of an internal flow channel is not easy to process in the processing process, so that the surface roughness of the volute is higher, and a flow field near the surface of the flow channel is influenced, thereby influencing the efficiency of the centrifugal compressor. The embodiment of the present invention solves this problem by designing the volute 100 as a split structure.

In the embodiment of the invention, the volute flow channel 102 of the volute 100 is defined by the first end cover 130 and the second end cover 140 which are detachably connected, so that when the first end cover 130 and the second end cover 140 are manufactured respectively, the surface of the inner surface of the volute flow channel 102 is subjected to surface finish machining and the included angle is chamfered, the surface of the volute flow channel is smoother, the distribution of an internal flow field is more uniform, and the flow loss caused by the fact that the surface of the flow channel is too rough is reduced. Thereby promoting the operating efficiency of the centrifugal compressor and being beneficial to the miniaturization of the centrifugal compressor. In addition, in the embodiment of the present invention, the spiral casing 100 is split into the spiral casing body 110, the first end cap 130 and the second end cap 140, so that the shape and the opening of each part are very simple and regular, the processing of each part is very convenient, the inner wall of the flow channel is also beneficial to being fully exposed, and the finish machining operation on the surface of the flow channel is very convenient.

In some embodiments, the inner circumferential surface of the cylinder 111 and the outer circumferential surfaces of the first end cap 130 and the second end cap 140 may be cylindrical surfaces to facilitate machining. The exhaust pipe 112 may be detachably mounted to the cylinder 111 to facilitate finish grinding of the inner circumferential surface of the cylinder 111.

The first end cap 130 and the second end cap 140 may be fastened by a screw connection. Further, the first end cap 130 and the second end cap 140 may be positioned by using pins and pin holes, so that the installation positions thereof are more accurate. The outward end surfaces of the first end cap 130 and the second end cap 140 are flush with the two axial end surfaces of the barrel 111, so that the positions of the first end cap 130 and the second end cap 140 are more stable and are not easily affected by the outside. The first end cap 130 and the second end cap 140 may be fixed to the cylinder 111 by screws or other methods, which are not described herein.

In some embodiments, as shown in fig. 1 to 4, the end surfaces of the first end cap 130 and the second end cap 140, which are attached to each other, are respectively provided with a spiral channel groove 1021, 1022, and the two spiral channel grooves 1021, 1022 are connected and spliced to form the spiral channel 102.

In other embodiments, one of the first end cap 130 and the second end cap 140 may be formed with a spiral runner groove, and the other end face may cover the runner groove to define the aforementioned spiral runner 102. Thus, a volute runner groove can be omitted, and the processing technology is simplified.

In some embodiments, as shown in fig. 2 to 4, the volute flow channel 102 may be flat with the thickness direction parallel to the axial direction of the volute 100, that is, the flow cross section may be an elongated rectangle. Along the flowing direction of the air flow, the air outlet flow passage 103 gradually changes from a flat shape matched with the volute flow passage 102 into a cylindrical shape. The flat volute flow channel 102 enables the whole volute 100 to be flat, so that the axial size of the centrifugal compressor is reduced, and the compressor is miniaturized. More importantly, because the outlet flow channel 103 gradually changes from flat to cylindrical, the gas flow can have a very good diffusion effect in the process of entering the cylindrical and widely opened outlet flow channel 103 from the thinner and flat volute flow channel 102. Moreover, because the air outlet flow passage 103 gradually changes from a flat shape to a cylindrical shape, the transition is very smooth, unnecessary resistance loss of the air flow is reduced, and meanwhile, the cylindrical shape is also suitable for being connected with a downstream pipeline.

The invention also provides a centrifugal compressor. The volute of the centrifugal compressor is the volute 100 of any one of the above embodiments.

Further, the centrifugal compressor further comprises a casing, a motor and at least one compression unit.

The casing is limited with accommodation space, and the motor is installed in the casing. The motor comprises a stator and a rotor, wherein the stator is fixed on the machine shell, and the rotor can rotate relative to the stator. The number of compression units may be one or more. For example, the centrifugal compressor may be of a single-stage compression type, and only one compression unit may be provided. The centrifugal compressor may be of a multistage compression type in which a plurality of compression units are provided. Each compression unit includes a volute 100 mounted to the casing and a centrifugal impeller 200 disposed within the volute 100. The centrifugal impeller 200 is configured to rotate under the drive of a motor to compress the airflow entering the volute 100 and to be discharged to the volute flow channel 102 and finally out through the outlet of the volute 100.

A conventional centrifugal compressor basically has a diffuser disposed downstream of a centrifugal impeller of each stage, and the centrifugal impeller discharges an air flow into the diffuser, and the air flow is diffused by the diffuser and then enters the scroll casing 100.

Compared with the traditional centrifugal compressor, the centrifugal compressor of the invention omits a diffuser, and the centrifugal impeller 200 is directly arranged in the volute 100, so that the larger diffusion loss caused by the larger rotation degree of the airflow in the diffuser is avoided, the overall efficiency of the centrifugal compressor is improved, and the structure of the centrifugal compressor is more compact. Therefore, this structure is advantageous for the miniaturization of the centrifugal compressor and for the application to a small central air conditioner such as a small chiller or a multi-split air conditioner while maintaining high efficiency.

In some embodiments, the centrifugal compressor further comprises at least one radial magnetic bearing and/or at least one axial magnetic bearing mounted within the casing to support the rotor of the electric machine. The centrifugal compressor further comprises an axial magnetic bearing to counteract axial forces imparted to the rotor by the centrifugal impeller movement. The magnetic suspension bearing is made by adopting a magnetic suspension principle and is an oilless bearing. Therefore, lubricating oil does not need to be added into the centrifugal compressor, so that the oil return problem of the compressor of a small and medium-sized refrigeration system is thoroughly solved (the conventional screw compressor, the scroll compressor and the rolling rotor compressor which are usually adopted are basically lubricated by oil), and the heat exchange efficiency of the heat exchanger is improved. And the magnetic suspension bearing is adopted, so that the centrifugal compressor has the advantages of small mechanical wear, low energy consumption, small noise, enhanced stability and longer service life.

Further, two planes in the thickness direction of the volute flow channel 102 and the circumferential volute side face can be in round angle transition, so that the strength of the volute is increased, the local stress concentration is relieved, the corner vortex is eliminated, and the uniformity of a flow field is ensured. The fillet radius may be selected based on the thickness of the volute 102. The split configuration of the volute 100 facilitates the machining of the aforementioned rounded corners.

Fig. 5 is a schematic structural view of a centrifugal impeller 200 in the centrifugal compressor according to an embodiment of the present invention; fig. 6 is a blade profile schematic of the centrifugal impeller 200 shown in fig. 5.

In some embodiments, the thickness of the volute 102 is made greater than the outlet width of the centrifugal impeller 200. The thickness of the volute 102 refers to the dimension of the volute in the axial direction (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 axial direction of the centrifugal impeller 200, and is specifically marked in fig. 5. Specifically, the inventors have confirmed through a plurality of experiments that the optimum effect can be obtained by setting the ratio of the thickness of the scroll flow passage 102 to the outlet width of the centrifugal impeller 200 to 1.5 to 2.

The inventors have recognized that exhausting centrifugal impeller 200 directly to volute 100 results in an increased mach number of the airflow, a large centrifugal effect of the airflow that accumulates radially outward, resulting in an uneven flow field, resulting in large flow losses. In order to eliminate or at least alleviate the above adverse effects, in the embodiment of the present invention, the thickness of the volute 102 is especially made larger than the outlet width B of the centrifugal impeller 200, so that after the airflow enters (the volute 102 of) the volute 100, the pressure expansion and the speed reduction are performed, the mach number is reduced, the centrifugal effect is reduced, 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.

In some embodiments, centrifugal impeller 200 is a strong back-curved shrouded impeller. As shown in fig. 6, the centrifugal impeller 200 has a plurality of blades 203 arranged along the circumferential direction thereof, a flow channel 212 is formed between every two adjacent blades 203, and the airflow enters the radially inner side of each flow channel 212 through the inlet 201 of the centrifugal impeller 200, and is rotated by the centrifugal impeller 200, so that the airflow flows to the radially outer side of each flow channel in each flow channel, so as to flow out of the centrifugal impeller 200 to the volute flow channel 102 of the volute 100. During which each vane 203 applies work to the airflow to raise the pressure of the airflow. Fig. 6 illustrates the rotation direction of the centrifugal impeller 200 by an arrow. Each blade 203 of the centrifugal impeller 200 has a backward-curved structure, and the tip (end adjacent to the radially outer edge of the centrifugal impeller 200) of each blade is bent backward compared to the remaining section, so that each blade of the centrifugal impeller 200 has a strong backward-curved structure, as shown in fig. 6.

In the embodiment of the present invention, the centrifugal impeller 200 is strongly backward curved, so that the centrifugal impeller 200 applies more work to the air flow and converts the work into static pressure lifting, and the work is converted into speed increase. Because the absolute airflow angle of the outlet of the strong backward-bending centrifugal impeller is larger, if a traditional diffuser form is adopted, the airflow rotation degree is larger, and the diffusion loss is larger. The embodiment of the present invention employs the specially designed volute 100 to directly connect with the centrifugal impeller 200, which can effectively avoid this problem. It follows that the various improvements of the embodiments of the present invention do not act in isolation from each other, but act in combination. Specifically, in the embodiment of the present invention, the centrifugal impeller 200 is integrally and directly installed in the volute 100, the flow channel of the volute 100 is specially designed, and the improvements of the strong backward-bending centrifugal impeller 200 are combined together, so that not only are the beneficial effects of various structural improvements obtained, but also the respective adverse effects are greatly avoided, so that the overall efficiency of the centrifugal compressor is high, the structure is more compact, and the miniaturization is facilitated.

FIG. 7 is an exploded schematic view of the centrifugal impeller 200 shown in FIG. 5; fig. 8 is a schematic structural view of the second impeller body 220 in fig. 7.

In some embodiments, as shown in fig. 6-8, the centrifugal impeller 200 may be split. Specifically, the centrifugal impeller 200 includes a first impeller body 210 and a second impeller body 220, wherein the first impeller body 210 and the second impeller body 220 are both disc-shaped and are in butt joint, and blade halves are formed on opposite surfaces of the first impeller body 210 and the second impeller body 220, and the blade halves are connected to form a complete blade 203.

The first impeller body 210 and the second impeller body 220 may be coupled and fastened by a plurality of fasteners, such as rivets 230. One or more positioning grooves 2113 can be formed on the first impeller body 210, the same number of positioning projections 2214 are formed on the second impeller body 220, and each positioning projection 2214 is clamped into one positioning groove 2113, so that the position between the first impeller body 210 and the second impeller body 220 is more stable, the alignment between the blade halves is more accurate, and the performance of the centrifugal impeller 200 is prevented from being influenced by the misalignment of the blades 203.

The first impeller body 210 is provided with a rotation shaft 214 having a mounting hole 215 formed at the center thereof so as to be coupled to the rotor by a screw 300. The second impeller body 220 is provided with an inlet 201 for the centrifugal impeller 200. The traditional centrifugal impeller is of an integrally cast type, and the surface precision of the traditional centrifugal impeller is not ideal, so that the compression efficiency and the adverse noise of the traditional centrifugal impeller are influenced. Especially for a closed impeller, the blades are inside, and the precision of the blade surface is more difficult to guarantee. In the present embodiment, the centrifugal impeller 200 is configured as a split type as described above, so that the two impeller bodies are separately manufactured, and the blades of each impeller body are exposed to the outside to process the surfaces of the impeller bodies, so that the impeller bodies are smoother.

Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.

Claims (10)

1. A volute for a centrifugal compressor, comprising:

the volute body comprises a cylinder and an exhaust pipe connected to the peripheral wall of the cylinder, wherein an exhaust flow passage communicated with the inside of the cylinder is defined in the exhaust pipe;

the first end cover and the second end cover are embedded and fixed in the cylinder body side by side along the axial direction of the cylinder body, the first end cover is provided with an air inlet flow passage, and the second end cover is provided with a mounting hole for mounting a centrifugal impeller; and is

The first end cover and the second end cover jointly define a volute flow channel surrounding the periphery of the mounting hole, the air inlet flow channel extends along the axial direction of the volute body and is opposite to the inlet of the centrifugal impeller, and the air outlet flow channel is communicated with the outlet of the volute flow channel and is used for discharging airflow compressed by the centrifugal impeller.

2. The spiral casing of claim 1,

the end faces, attached to each other, of the first end cover and the second end cover are respectively provided with a volute flow channel groove, and the two volute flow channel grooves are connected and spliced to form the volute flow channel.

3. The spiral casing of claim 1,

one of the first end cover and the second end cover is provided with a volute runner groove, and the end surface of the other end cover covers the volute runner groove to limit the volute runner.

4. The spiral casing of claim 1,

the first end cover and the second end cover are connected and fastened through screws.

5. The spiral casing of claim 1,

the outward end faces of the first end cover and the second end cover are flush with the two axial end faces of the barrel respectively.

6. The spiral casing of claim 1,

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

7. The spiral casing of claim 1,

the exhaust pipe is detachably mounted to the cylinder.

8. The spiral casing of claim 1,

the volute flow channel is flat with the thickness direction parallel to the axial direction of the volute; and is

Along the airflow flowing direction, the air outlet flow channel gradually transits from a flat shape matched with the volute flow channel to a cylinder shape.

9. A centrifugal compressor comprising a volute, wherein the volute is as claimed in any one of claims 1 to 8.

10. The centrifugal compressor of claim 9, comprising:

a housing;

the motor is arranged in the shell; and

at least one compression unit, each compression unit including a volute and a centrifugal impeller, the volute being mounted to the housing, the centrifugal impeller being mounted within the volute, the centrifugal impeller being configured to rotate under the drive of the motor to compress an airflow entering the volute and discharge the airflow toward the volute.

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