CN117167330A - Centrifugal compressor and control method thereof - Google Patents

Abstract

The present application relates to a centrifugal compressor and a control method thereof, the centrifugal compressor comprising: a main shaft; the first impeller and the second impeller are sleeved on the outer peripheral side of the main shaft and are sequentially arranged along the axial direction of the main shaft; the reflux device is used for communicating the air outlet of the first impeller with the air inlet of the second impeller; the first adjustable diffuser is arranged on a first flow passage between the air outlet of the first impeller and the reflux device; the first driving mechanism is used for driving the first adjustable diffuser to axially reciprocate so as to adjust the axial width of the first flow channel; the second adjustable diffuser is arranged at the air outlet of the second impeller and is communicated with the second runner; and the second driving mechanism is used for driving the second adjustable diffuser to reciprocate along the axial direction so as to adjust the axial width of the second flow channel. The application can widen the operation range of the centrifugal compressor under small load, reduce the phenomena of stall, surge and the like, and improve the stability and reliability of the unit.

Description

Centrifugal compressor and control method thereof

Technical Field

The application relates to the technical field of compressors, in particular to a centrifugal compressor and a control method thereof.

Background

In the centrifugal compressor, a diffuser is one of the action components constituting the aerodynamic part thereof, and its action is to slow down the air flow having a relatively large velocity flowing out from the impeller, so that kinetic energy is effectively converted into pressure energy, which has a relatively large influence on the performance of the compressor.

When the unit actually operates, due to the influence of air temperature or load, a diffuser is often required to automatically adjust and change the flow speed and flow of air suction so as to achieve the purpose of adjusting the refrigerating capacity of the unit. For example, as the vane becomes smaller, the suction flow decreases and the diffuser flow path is relatively large, creating a turbulent region, leading to rotating stall, resulting in increased separation losses.

Disclosure of Invention

The application aims to provide a centrifugal compressor, which can widen the operation range of the centrifugal compressor under small load, reduce the occurrence of phenomena such as stall and surge, and improve the stability and reliability of a unit.

In a first aspect, an embodiment of the present application provides a centrifugal compressor comprising: a main shaft; the first impeller and the second impeller are sleeved on the outer peripheral side of the main shaft and are sequentially arranged along the axial direction of the main shaft; the reflux device is used for communicating the air outlet of the first impeller with the air inlet of the second impeller; the first adjustable diffuser is arranged on a first flow passage between the air outlet of the first impeller and the reflux device; the first driving mechanism is used for driving the first adjustable diffuser to axially reciprocate so as to adjust the axial width of the first flow channel; the second adjustable diffuser is arranged at the air outlet of the second impeller and is communicated with the second runner; and the second driving mechanism is used for driving the second adjustable diffuser to reciprocate along the axial direction so as to adjust the axial width of the second flow channel.

In one possible embodiment, the first drive mechanism includes: the motor is connected with the opening degree of the guide vane in a signal communication manner so as to drive the guide vane to rotate, and the moving mechanism is used for converting the rotary motion of the guide vane into axial reciprocating motion.

In one possible embodiment, the moving mechanism includes an eccentric cam and a guide rod, wherein the rotating shaft of the guide vane passes through the shaft hole of the eccentric cam and is fixedly connected with the eccentric cam, one end of the guide rod is matched with the eccentric cam, and the other end of the guide rod is connected with the first adjustable diffuser.

In one possible embodiment, the moving mechanism further includes a first elastic member, and the first elastic member is sleeved on the outer peripheral side of the guide rod, so that one end of the guide rod, which is close to the eccentric cam, abuts against the outer profile of the eccentric cam.

In one possible embodiment, the number of the moving mechanisms is plural, and the plural moving mechanisms are arranged at intervals along the circumferential direction of the first impeller.

In one possible implementation, the second driving mechanism comprises a cylinder with a containing cavity, the cylinder comprises a cylinder body and a piston, one end of the piston is slidably arranged in the containing cavity, the other end of the piston extends out of the cylinder body and is connected with the second adjustable diffuser, and the second driving mechanism drives the piston to slide by changing the capacity of pressure medium in the containing cavity so as to drive the second adjustable diffuser to axially reciprocate.

In one possible embodiment, the second driving mechanism further includes a second elastic member, the piston divides the accommodating chamber into a first chamber and a second chamber, the first chamber allows pressure medium to flow in and out, the second chamber accommodates the second elastic member, and the second elastic member abuts between the piston and an inner wall of the second chamber along a moving direction of the piston.

In one possible embodiment, the piston comprises a stopper body slidably disposed in the receiving chamber and a rod body connected to one side of the stopper body and extending out of the cylinder through the second chamber and connected to the second adjustable diffuser; the second elastic piece is sleeved outside the rod body and is abutted to the plug body and the inner wall of the second cavity.

In one possible implementation manner, the second driving mechanism further comprises an inlet electromagnetic valve and an outlet electromagnetic valve, the first cavity is provided with a medium inlet and a medium outlet, and the inlet electromagnetic valve is arranged at the medium inlet and used for controlling on-off of pressure medium inflow; the outlet electromagnetic valve is arranged at the medium outlet and used for controlling the on-off of the outflow of the pressure medium.

In one possible embodiment, the number of the cylinders is a plurality, the cylinders are distributed at intervals along the circumference of the second adjustable diffuser and are connected with the second adjustable diffuser, and the cylinders are connected in series or in parallel through connecting pipelines.

In a second aspect, an embodiment of the present application further provides a control method of a centrifugal compressor, including: when the centrifugal compressor runs at the maximum rated demand of the refrigerating capacity of the unit, the first flow passage of the first adjustable diffuser is controlled to be at the maximum axial width through the first driving mechanism, and the second flow passage of the second adjustable diffuser is controlled to be at the maximum axial width through the second driving mechanism; when the centrifugal compressor operates in the range of rated demand of unit refrigerating capacity, the axial width of the first flow channel of the first adjustable diffuser controlled by the first driving mechanism and the axial width of the second flow channel of the second adjustable diffuser controlled by the second driving mechanism are gradually reduced, and the axial width of the first flow channel is larger than that of the second flow channel.

According to the centrifugal compressor and the control method thereof provided by the embodiment of the application, the air outlet of the first impeller is communicated with the air inlet of the second impeller through the reflux device, the first adjustable diffuser is arranged between the air outlet of the first impeller and the reflux device, the second adjustable diffuser is arranged at the outlet of the second impeller, the axial width of the first adjustable diffuser is controlled through the first driving mechanism, and the axial width of the second adjustable diffuser is controlled through the second driving mechanism, so that the operation range of the centrifugal compressor in small load can be widened on the premise of not additionally increasing a compressor system, the phenomena of stall, surge and the like are reduced, and the stability and reliability of a unit are improved.

Drawings

Features, advantages, and technical effects of exemplary embodiments of the present application will be described below with reference to the accompanying drawings. In the drawings, like parts are designated with like reference numerals. The drawings are not drawn to scale, but are merely for illustrating relative positional relationships, and the layer thicknesses of certain portions are exaggerated in order to facilitate understanding, and the layer thicknesses in the drawings do not represent the actual layer thickness relationships.

Fig. 1 shows a schematic structural view of a centrifugal compressor provided by an embodiment of the present application;

FIG. 2 shows a schematic structural view of the first drive mechanism shown in FIG. 1;

FIG. 3 illustrates a schematic diagram of a second adjustable diffuser shown in FIG. 1;

FIG. 4 shows a schematic structural view of the second drive mechanism shown in FIG. 3;

fig. 5 shows a flow chart of a control method of a centrifugal compressor provided by an embodiment of the application.

1. A first impeller;

2. a second impeller;

3. a reflow device;

4. a first adjustable diffuser;

5. a first driving mechanism; 51. a motor; 52. a guide vane; 53. a moving mechanism; 531. an eccentric cam; 532. a guide rod; 533. a first elastic member;

6. a second adjustable diffuser; 10. a main shaft;

7. a second driving mechanism; 70. a receiving chamber; 701. a first cavity; 702. a second cavity; 71. a cylinder; 711. a cylinder; 712. a piston; 712a, a plug body; 712b, a rod body; 72. a second elastic member; 73. an inlet solenoid valve; 74. an outlet solenoid valve; 75. and a connecting pipeline.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

As shown in fig. 1, an embodiment of the present application provides a centrifugal compressor, which includes a main shaft 10, a first impeller 1, a second impeller 2, a reflux unit 3, a first adjustable diffuser 4, a first driving mechanism 5, a second adjustable diffuser 6, and a second driving mechanism 7.

The first impeller 1 and the second impeller 2 are sleeved on the outer peripheral side of the main shaft 10 and are sequentially arranged along the axial direction of the main shaft 10; the reflux device 3 is used for communicating the air outlet of the first impeller 1 with the air inlet of the second impeller 2;

the first adjustable diffuser 4 is arranged on a first flow passage between the air outlet of the first impeller 1 and the reflux device 3; the first driving mechanism 5 is used for driving the first adjustable diffuser 4 to axially reciprocate so as to adjust the axial width of the first flow channel;

the second adjustable diffuser 6 is arranged at the air outlet of the second impeller 2 and is communicated with the second flow passage; the second driving mechanism 7 is used for driving the second adjustable diffuser 6 to reciprocate along the axial direction so as to adjust the axial width of the second flow channel.

In the application, the gas still has higher flow speed when flowing out from the gas outlet of the first impeller 1, in order to fully utilize the speed energy to improve the pressure of the gas, the first adjustable diffuser 4 is arranged at the downstream of the first impeller 1, and the first driving mechanism 5 drives the first adjustable diffuser 4 to move so as to adjust the width of the first flow channel, thereby reducing the speed of the gas flow with higher speed flowing out from the first impeller 1 and effectively converting the kinetic energy into pressure energy.

Likewise, a second adjustable diffuser 6 is arranged at the air outlet of the second impeller 2, and the second adjustable diffuser 6 is driven to move by a second driving mechanism 7 to adjust the width of the second flow channel; thus, when the suction flow of the centrifugal compressor is reduced, if the width of the diffuser flow passage is relatively large, a turbulent flow zone will be created, leading to rotating stall, so that the separation loss increases. At the moment, the width of the diffusion flow passage needs to be reduced, so that the diffusion flow passage converges, turbulence is reduced, the requirements of a unit adapting to various working conditions are met, the minimum load value of stable operation of the centrifugal compressor is reduced, the operation range of the centrifugal compressor is widened, and the flow stability of the air flow at the air outlet of the impeller under the small-load working condition is improved.

In addition, the air outlet of the first impeller 1 can be communicated with the air inlet of the second impeller 2 by the reflux device 3, so that the air flow at the air outlet of the first impeller 1 can uniformly enter the second impeller 2 along the axial direction of the main shaft 10, and the diffusion of two-stage air flow is realized. The return 3 comprises a baffle and guide vanes, which are generally circular-arc shaped, and may be cast integrally with the main shaft 10 or manufactured separately and then bolted together.

According to the centrifugal compressor provided by the embodiment of the application, the air outlet of the first impeller 1 is communicated with the air inlet of the second impeller 2 through the reflux device 3, the first adjustable diffuser 4 is arranged between the air outlet of the first impeller 1 and the reflux device 3, the second adjustable diffuser 6 is arranged at the outlet of the second impeller 2, the axial width of the first adjustable diffuser 4 is controlled through the first driving mechanism 5, and the axial width of the second adjustable diffuser 6 is controlled through the second driving mechanism 7, so that the operation range of the centrifugal compressor in small load can be widened on the premise of not additionally increasing a compressor system, phenomena such as stall and surge are reduced, and the stability and reliability of a unit are improved.

In some embodiments, the first drive mechanism 5 comprises: the motor 51, the guide vane 52 and the moving mechanism 53, the guide vane 52 is arranged at the air inlet of the first impeller 1, the rotating shaft of the guide vane 52 passes through the moving mechanism 53, one end of the moving mechanism 53 away from the guide vane 52 is connected with the first adjustable diffuser 4, the motor 51 is connected with the opening degree of the guide vane 52 in signal communication so as to drive the guide vane 52 to rotate, and the moving mechanism 53 is used for converting the rotary motion of the guide vane 52 into the reciprocating motion along the axial direction.

Optionally, the motor 51 is an asynchronous motor, and a communication line of the motor is electrically connected with a unit control cabinet, so that the motor 51 is in signal communication with the opening degree of the guide vane 52 to realize joint debugging. The motor 51 drives the guide vane 52 to rotate so as to adjust the opening degree of the guide vane 52, and then drives the moving mechanism 53 to convert the rotary motion of the guide vane 52 into the reciprocating motion along the axial direction, thereby adjusting the axial width of the first flow passage of the first adjustable diffuser 4.

During operation of the centrifugal compressor, the load state of the centrifugal compressor may be adjusted by the opening of the guide vanes 52. When the opening degree of the guide vane 52 is larger, the amount of the refrigerant entering the centrifugal compressor is relatively larger, the refrigerant is thrown out to the first flow passage of the first adjustable diffuser 4 at a high speed under the action of the first impeller 1, and the axial width of the first flow passage is adjusted through the first adjustable diffuser 4 so as to adapt to the change of the working condition of the centrifugal compressor, and the impact of the refrigerant in the centrifugal compressor can be avoided while the centrifugal compressor keeps high-efficiency running, so that the occurrence of surge is effectively reduced.

Specifically, as shown in fig. 1, when the load required by the unit decreases, the motor 51 controls the opening of the guide vane 52 to decrease, so that the moving mechanism 53 drives the first adjustable diffuser 4 to translate from the left side to the right side, reducing the axial width of the first flow passage, making it convergent, and reducing the turbulence loss. Conversely, when the load required by the unit increases, the motor 51 controls the opening of the guide vane 52 to increase, so that the moving mechanism 53 drives the first adjustable diffuser 4 to translate from the right side to the left side, and the width of the first flow passage is increased, thereby meeting the requirement of large flow.

Further, the moving mechanism 53 includes an eccentric cam 531 and a guide rod 532, the rotation shaft of the guide vane 52 passes through the shaft hole of the eccentric cam 531 and is fixedly connected with the eccentric cam 531, one end of the guide rod 532 is matched with the eccentric cam 531, and the other end is connected with the first adjustable diffuser 4.

As shown in fig. 2, the magnitude of the eccentric amount of the eccentric cam 531 determines the displacement of the guide rod 532 in the axial direction. When the motor 51 controls the opening of the guide vane 52 to decrease, the guide vane 52 drives the eccentric cam 531 to continuously rotate in the counterclockwise direction, so that the axial depth of the guide rod 532 is increased, and the first adjustable diffuser 4 is driven to translate from the left side to the right side, and the axial width of the first flow passage is reduced.

When the motor 51 controls the opening of the guide vane 52 to increase, the guide vane 52 drives the eccentric cam 531 to continuously rotate in the clockwise direction, so that the axial depth of the guide rod 532 is reduced, and the first adjustable diffuser 4 is driven to translate from the right side to the left side, and the width of the first flow passage is increased.

Further, the moving mechanism 53 further includes a first elastic member 533, where the first elastic member 533 is sleeved on the outer peripheral side of the guide rod 532, so that an end of the guide rod 532, which is close to the eccentric cam 531, abuts against the outer surface of the eccentric cam 531.

Alternatively, the first elastic member 533 is a return spring. When the eccentric cam 531 pushes the guide rod 532 to change along the axial depth, the first elastic member 533 can make the guide rod 532 contact with the outer surface of the eccentric cam 531 all the time, and can buffer the impact force of the guide rod 532 during the movement process, so as to prolong the service life of the moving mechanism 53.

In some embodiments, the number of the moving mechanisms 53 is plural, and the plurality of moving mechanisms 53 are arranged at intervals in the circumferential direction of the first impeller 1. The eccentric cams 531 and the guide rods 532 of the plurality of moving mechanisms 53 are connected in series to each other to achieve synchronous control, and improve the working efficiency of the air flow diffusion.

In some embodiments, the second driving mechanism 7 includes a cylinder 71 having a housing chamber 70, the cylinder 71 includes a cylinder body 711 and a piston 712, one end of the piston 712 is slidably disposed in the housing chamber 70, the other end of the piston 712 extends out of the cylinder body 711 and is connected to the second adjustable diffuser 6, and the second driving mechanism 7 drives the piston 712 to slide by changing the volume of the pressure medium in the housing chamber 70, so as to drive the second adjustable diffuser 6 to reciprocate axially.

As shown in fig. 3, the pressure medium is a high pressure gas source, typically originating from the stack condenser or at the discharge of the centrifugal compressor. The second driving mechanism 7 applies a thrust to the second adjustable diffuser 6 through the pressure medium in the accommodating chamber 70 of the cylinder 71 to adjust the axial width of the second flow passage. The second adjustable diffuser 6 is annular, and the pressure medium can generate positive pressure vertical to the surface of the second adjustable diffuser 6 on the second adjustable diffuser 6, so that the annular second adjustable diffuser 6 is accurately pushed to move along the axial direction of the second adjustable diffuser 6, the second adjustable diffuser 6 is prevented from being inclined and blocked due to the fact that the second adjustable diffuser 6 is subjected to the thrust inclined relative to the axial line, and the reliability and stability of the movement of the second adjustable diffuser 6 are improved.

Further, the second driving mechanism 7 further includes a second elastic member 72, the piston 712 divides the accommodating chamber 70 into a first chamber 701 and a second chamber 702, the first chamber 701 allows pressure medium to flow in and out, the second chamber 702 accommodates the second elastic member 72, and the second elastic member 72 abuts between the piston 712 and an inner wall of the second chamber 702 along a moving direction of the piston 712.

As shown in fig. 4, the piston 712 divides the accommodating chamber 70 into a first chamber 701 and a second chamber 702, the first chamber 701 is a closed space, when the pressure in the first chamber 701 increases, the pressure medium pushes the piston 712 to move leftwards, and the connected second adjustable diffuser 6 also moves leftwards, resulting in narrowing of the second flow passage at the air outlet of the second impeller 2; when the pressure in the first chamber 701 decreases, the piston 712 moves rightward by the second elastic member 72, and the second adjustable diffuser 6 is also moved rightward by the piston 712, resulting in widening of the second flow passage at the air outlet of the second impeller 2.

Further, the piston 712 includes a stopper 712a and a rod body 712b, the stopper 712a is slidably disposed in the accommodating cavity 70, the rod body 712b is connected to one side of the stopper 712a, and extends out of the cylinder 711 through the second cavity 702 and is connected to the second adjustable diffuser 6; the second elastic member 72 is sleeved outside the rod 712b and abuts against the stopper 712a and the inner wall of the second cavity 702.

Alternatively, the second elastic member 72 is a compression spring. The second elastic member 72 is sleeved outside the rod 712b and abuts against the stopper 712a and the inner wall of the second cavity 702. When the pressure in the first cavity 701 decreases, the elastic force of the second elastic member 72 may push the plug 712a to move from left to right, and further drive the second adjustable diffuser 6 to move to the right, so as to widen the second flow passage at the air outlet of the second impeller 2.

Further, the second driving mechanism 7 further comprises an inlet electromagnetic valve 73 and an outlet electromagnetic valve 74, the first cavity 701 is provided with a medium inlet and a medium outlet, and the inlet electromagnetic valve 73 is arranged at the medium inlet and is used for controlling on-off of inflow of pressure medium; an outlet solenoid valve 74 is provided at the medium outlet for controlling the on-off of the outflow of the pressure medium.

The second adjustable diffuser 6 has an inlet solenoid valve 73 and an outlet solenoid valve 74 disposed at the inlet and outlet, respectively, and pressure medium enters and exits the cylinder 71 through the inlet solenoid valve 73 and the outlet solenoid valve 74. The inlet solenoid valve 73 and the outlet solenoid valve 74 may be opened or closed by electric signal control to control whether or not the pressure medium can enter the cylinder 71.

When the centrifugal compressor is operated under a heavy load condition, the inlet solenoid valve 73 is closed, the outlet solenoid valve 74 is opened, the pressure in the first chamber 701 is low, and the piston 712 is maintained at the rightmost end by the second elastic member 72, so that the second adjustable diffuser 6 connected to the piston 712 is moved to the rightmost side. At this time, the second flow passage of the air outlet of the second impeller 2 is in the widest state, and the second impeller 2 can perform work with maximum capacity.

When the centrifugal compressor operates under the small-load working condition, if the second flow passage is still kept in the widest state, the refrigerant at the air outlet of the second impeller 2 may stall, surge and the like due to insufficient speed, thereby causing the centrifugal compressor to stop. At this time, the outlet electromagnetic valve 74 needs to be closed, the inlet electromagnetic valve 73 is opened, and a pressure medium enters the first cavity 701, so that the pressure in the first cavity 701 is increased, and then the second elastic piece 72 is compressed to enable the piston 712 to move leftwards, so as to drive the second adjustable diffuser 6 to move leftwards, narrow the second flow passage of the air outlet of the second impeller 2, improve the flow rate of the refrigerant at the air outlet of the second impeller, effectively avoid surging, greatly reduce the minimum load value of the centrifugal compressor, and enlarge the operation range.

In one possible embodiment, the number of the cylinders 71 is plural, the plural cylinders 71 are distributed at intervals along the circumferential direction of the second adjustable diffuser 6, and are connected to the second adjustable diffuser 6, and the plural cylinders 71 are connected in series or parallel to each other through the connecting pipe 75.

The plurality of cylinders 71 are arranged at intervals along the circumferential direction of the annular second adjustable diffuser 6, are mutually communicated through a connecting pipeline 75, and then control the inflow and outflow of pressure medium in the cylinders 71 through the inlet electromagnetic valve 17 and the outlet electromagnetic valve 18, so as to control the axial movement of the second adjustable diffuser 6.

Because the pressure media in the plurality of air cylinders 71 are mutually communicated, the plurality of air cylinders 71 are driven to synchronously move through the flowing pressure media, and then the second adjustable diffuser 6 is synchronously driven to move at a plurality of points, so that the second adjustable diffuser 6 can only move along the axial direction of the second adjustable diffuser, and the positions of the second adjustable diffuser 6 in other directions are kept unchanged, the reliability of smooth movement of the second adjustable diffuser 6 along the axial direction can be ensured, and the operation reliability of the centrifugal compressor is further ensured.

As shown in fig. 5, an embodiment of the present application further provides a control method of a centrifugal compressor as described above, including the following steps S1 to S2, and the control method of the centrifugal compressor is described below with reference to fig. 1.

Step S1: when the centrifugal compressor operates at the maximum rated demand of the refrigerating capacity of the unit, the first flow passage of the first adjustable diffuser 4 is controlled to be at the maximum axial width by the first driving mechanism 5, and the second flow passage of the second adjustable diffuser 6 is controlled to be at the maximum axial width by the second driving mechanism 7;

step S2: when the centrifugal compressor operates in the range of the rated demand of the unit refrigerating capacity, the axial width of the first flow passage of the first adjustable diffuser 4 controlled by the first driving mechanism 5 and the axial width of the second flow passage of the second adjustable diffuser 6 controlled by the second driving mechanism 7 are gradually reduced, and the axial width of the first flow passage is larger than the axial width of the second flow passage.

In step S1, when the maximum rated demand of the unit refrigerating capacity is 100%, the opening of the guide vane 52 is the largest, and the first adjustable diffuser 4 is in a fully open state, that is, the left side of the first adjustable diffuser 4 near the first flow passage is in an optimal state, and the first-stage compression efficiency can meet the design target. At this time, the inlet solenoid valve 17 of the second adjustable diffuser 6 is in a closed state, the outlet solenoid valve 18 is in an open state, and the air in the cylinder 71 is smoothly discharged for a certain period of time, so that the pressure of the first chamber 701 is reduced. When the resultant force of the pressure generated by the gas at the gas outlet of the second impeller 2 and the second elastic member 72 is greater than the pressure of the first chamber 701, the second adjustable diffuser 6 moves leftwards in a fully opened state, and then the outlet electromagnetic valve 18 is closed, preventing the second adjustable diffuser 6 from reciprocating due to pressure fluctuation. At this time, the first adjustable diffuser 4 and the second adjustable diffuser 6 are in a fully opened state, the gas flow of the whole centrifugal compressor is in an optimal state, and the first impeller 1 and the second impeller 2 can exert the maximum working capacity and efficiency.

In the step S2, the interval range of the rated demand of the unit refrigerating capacity can be divided into five interval ranges of 80% -100%, 60% -80%, 40% -60%, 20% -40% and 0% -20%.

When the refrigerating capacity of the unit is 80% -100% of the rated demand, the opening degree of the guide vane 52 is the largest, the first adjustable diffuser 4 is in a fully-opened state, the primary compression efficiency of the centrifugal compressor is located near the optimal point, the gas temperature reaching the position of the air inlet of the second impeller 2 is lower due to high-efficiency operation, and the secondary compression power consumption is reduced. Because the refrigerating capacity is reduced, the inlet electromagnetic valve 17 of the second adjustable diffuser 6 is required to be in a partially opened state, the outlet electromagnetic valve 18 is required to be in a closed state, and the high-pressure gas entering cylinder 71 drives the second adjustable diffuser 6 to move out a partial distance along the axial direction, so that the second flow passage is narrowed, and the refrigerating capacity of the unit is reduced. Since the high-pressure air source is used as the driving force, the opening of the inlet electromagnetic valve 17 is 20% of the full-open state, a certain throttling effect is achieved, the pressure entering the air cylinder 71 can be properly reduced, and the distance requirement of the second flow passage is met. In addition, when the demand load is running, the reduced distance of the second adjustable diffuser 6 accounts for about 10% of the full-open state, that is, the axial width of the second adjustable diffuser 6 is 0.9 times of the full-open state, and the unit can be ensured to run efficiently and stably in the refrigerating section through the process.

When the refrigerating capacity of the unit is 60% -80% of the rated demand, the opening degree of the guide vane 52 starts to be reduced, the moving mechanism 53 consisting of the eccentric cam 531 and the guide rod 532 pushes the first adjustable diffuser 4 to move rightwards, the first flow passage at the downstream of the first impeller 1 is narrowed to adapt to the working condition of reducing the refrigerating capacity, and the turbulence intensity of the first flow passage gas of the first adjustable diffuser 4 is reduced. The inlet electromagnetic valve 17 of the second adjustable diffuser 6 is in a partially opened state, the outlet electromagnetic valve 18 is in a closed state, and the high-pressure gas enters the cylinder 71 to drive the second adjustable diffuser 6 to move out a partial distance, so that the second flow passage is narrowed, and the refrigerating capacity of the unit is reduced. At this time, the opening of the guide vane 52 is 80% of the flow area, and the first adjustable diffuser 4 is driven by the eccentric cam 531 and the guide rod 532 to move rightward to narrow the first flow passage, that is, the flow width of the first adjustable diffuser 4 is 0.9 times of the full opening. The opening degree of the inlet solenoid valve 17 of the second adjustable diffuser 6 is 40% of the full open state, and the flow width of the second adjustable diffuser 6 is 0.7 times of the full open state.

When the unit refrigerating capacity is 40% -60% of the rated demand, the opening degree of the guide vane 52 is further reduced, for example, the opening degree of the guide vane 52 is 50% of the flow area, the first adjustable diffuser 4 is driven by the eccentric cam 531 and the guide rod 532, and the width of the first flow passage is narrowed to the right 0.7 times when the first flow passage is fully opened. The opening degree of the inlet solenoid valve 17 of the second adjustable diffuser 6 is 60% of the full open state, and the flow width of the second adjustable diffuser 6 is 0.5 times of the full open state.

When the unit refrigerating capacity is 20% -40% of the rated demand, the opening degree of the guide vane 52 is reduced to 30% of the flow area, and the width of the first flow passage narrowed by the first adjustable diffuser 4 when moving rightwards is 0.5 times of the width of the first flow passage. The opening degree of the inlet solenoid valve 17 of the second adjustable diffuser 6 is 80% of the full open state, and the flow width of the second adjustable diffuser 6 is 0.3 times of the full open state.

When the unit refrigerating capacity is less than 20% of the rated demand, the opening of the guide vane 52 is 10% of the flow area, and the width of the first flow passage narrowed by the first adjustable diffuser 4 when moving rightwards is 0.3 times of the full opening. The opening degree of the inlet solenoid valve 17 of the second adjustable diffuser 6 is 100% of the fully opened state, and the flow width of the second adjustable diffuser 6 is 0.2 times of the fully opened state.

According to the control method of the centrifugal compressor, the air outlet of the first impeller 1 is communicated with the air inlet of the second impeller 2 through the reflux device 3, the first adjustable diffuser 4 is arranged between the air outlet of the first impeller 1 and the reflux device 3, the second adjustable diffuser 6 is arranged at the outlet of the second impeller 2, the axial width of the first adjustable diffuser 4 is controlled through the first driving mechanism 5, and the axial width of the second adjustable diffuser 6 is controlled through the second driving mechanism 7, so that the operation range of the centrifugal compressor in small load can be widened on the premise that a compressor system is not additionally increased, phenomena such as stall and surge are reduced, and the stability and reliability of a unit are improved.

It should be noted that references in the specification to "one embodiment," "an example embodiment," "some embodiments," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It should be readily understood that the terms "on … …", "above … …" and "above … …" in this disclosure should be interpreted in the broadest sense such that "on … …" means not only "directly on something", but also includes "on something" with intermediate features or layers therebetween, and "above … …" or "above … …" includes not only the meaning "on something" or "above" but also the meaning "above something" or "above" without intermediate features or layers therebetween (i.e., directly on something).

Further, spatially relative terms, such as "below," "beneath," "above," "over," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may have other orientations (rotated 90 degrees or at other orientations), and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application.

Claims (11)

1. A centrifugal compressor, comprising:

a main shaft;

the first impeller and the second impeller are sleeved on the outer peripheral side of the main shaft and are sequentially arranged along the axial direction of the main shaft;

the reflux device is used for communicating the air outlet of the first impeller with the air inlet of the second impeller;

the first adjustable diffuser is arranged on a first flow passage between the air outlet of the first impeller and the reflux device;

the first driving mechanism is used for driving the first adjustable diffuser to axially reciprocate so as to adjust the axial width of the first flow channel;

the second adjustable diffuser is arranged at the air outlet of the second impeller and is communicated with the second runner; and

and the second driving mechanism is used for driving the second adjustable diffuser to reciprocate along the axial direction so as to adjust the axial width of the second flow passage.

2. The centrifugal compressor of claim 1, wherein the first drive mechanism comprises: the motor, the stator and the moving mechanism, the stator set up in the air inlet department of first impeller, the pivot of stator passes moving mechanism, moving mechanism keep away from the one end of stator with first adjustable diffuser is connected, the motor with the aperture signal communication connection of stator, in order to drive the stator rotates, moving mechanism is used for with the rotary motion of stator turns into along axial reciprocating motion.

3. The centrifugal compressor according to claim 2, wherein the moving mechanism includes an eccentric cam and a guide rod, a rotating shaft of the guide vane passes through a shaft hole of the eccentric cam and is fixedly connected with the eccentric cam, one end of the guide rod is matched with the eccentric cam, and the other end of the guide rod is connected with the first adjustable diffuser.

4. A centrifugal compressor according to claim 3, wherein the moving mechanism further comprises a first elastic member, and the first elastic member is sleeved on the outer peripheral side of the guide rod, so that one end of the guide rod, which is close to the eccentric cam, is pressed against the outer profile of the eccentric cam.

5. The centrifugal compressor according to any one of claims 2 to 4, wherein the number of said moving mechanisms is plural, and a plurality of said moving mechanisms are arranged at intervals in the circumferential direction of said first impeller.

6. The centrifugal compressor according to claim 1, wherein the second driving mechanism comprises a cylinder having a receiving chamber, the cylinder comprises a cylinder body and a piston, one end of the piston is slidably disposed in the receiving chamber, the other end of the piston extends out of the cylinder body and is connected with the second adjustable diffuser, and the second driving mechanism drives the piston to slide by changing the volume of the pressure medium in the receiving chamber so as to drive the second adjustable diffuser to reciprocate in the axial direction.

7. The centrifugal compressor according to claim 6, wherein the second driving mechanism further includes a second elastic member, the piston partitions the accommodation chamber into a first chamber in which the pressure medium is allowed to flow in and out, and a second chamber in which the second elastic member is accommodated, and the second elastic member abuts between the piston and an inner wall of the second chamber in a moving direction of the piston.

8. The centrifugal compressor of claim 7, wherein the piston includes a stopper body slidably disposed within the receiving chamber and a rod connected to one side of the stopper body and extending out of the cylinder through the second chamber and connected to the second adjustable diffuser; the second elastic piece is sleeved outside the rod body and is abutted to the plug body and the inner wall of the second cavity.

9. The centrifugal compressor according to claim 7, wherein said second driving mechanism further comprises an inlet solenoid valve and an outlet solenoid valve, said first chamber having a medium inlet and a medium outlet, said inlet solenoid valve being provided at said medium inlet for controlling on-off of said pressure medium inflow; the outlet electromagnetic valve is arranged at the medium outlet and used for controlling the on-off of the outflow of the pressure medium.

10. The centrifugal compressor according to claim 6, wherein the number of the cylinders is plural, the plural cylinders are distributed at intervals along the circumferential direction of the second adjustable diffuser and are each connected with the second adjustable diffuser, and the plural cylinders are connected in series or in parallel with each other through connecting pipes.

11. A control method of a centrifugal compressor according to any one of claims 1 to 10, comprising:

when the centrifugal compressor runs at the maximum rated demand of the refrigerating capacity of the unit, the first flow passage of the first adjustable diffuser is controlled to be at the maximum axial width through the first driving mechanism, and the second flow passage of the second adjustable diffuser is controlled to be at the maximum axial width through the second driving mechanism;

when the centrifugal compressor operates in the range of the rated demand of the unit refrigerating capacity, the axial width of the first flow passage of the first adjustable diffuser controlled by the first driving mechanism and the axial width of the second flow passage of the second adjustable diffuser controlled by the second driving mechanism are gradually reduced, and the axial width of the first flow passage is larger than that of the second flow passage.