Twin-screw compressor

Abstract

The invention discloses a double-screw compressor which comprises a shell, a first screw, a second screw, a third screw and a fourth screw, the shell is provided with an inner cavity, an air inlet and an air outlet, and the air inlet and the air outlet are communicated with the inner cavity; the at least one pair of screws are rotatably arranged in the inner cavity of the shell; and the internal volume ratio adjusting mechanism is arranged at the position, close to the exhaust port, of the shell and used for carrying out stepped adjustment on the through-flow area between the inner cavity of the shell and the exhaust port. According to the technical scheme, various working conditions of the compressor can be adapted, components such as a sliding valve are omitted, and the structural complexity and the control complexity are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of compressors, and in particular to a twin-screw compressor. Background Art

[0002] For positive displacement compressors, the internal volume ratio refers to the ratio of exhaust volume to suction volume. It reflects the performance of the compressor, affects energy consumption and efficiency, and therefore needs to be adjusted frequently to meet system requirements and needs to be matched with other parameters in actual applications.

[0003] Most screw refrigeration compressors use sliding valves to adjust the volume ratio of the compressor. However, the energy adjustment of the sliding valve may cause over-compression or under-compression of the gas at partial load. In addition, the fixed-frequency motor has low efficiency at partial load, which leads to low energy efficiency of the compressor and the failure to achieve the optimal Coefficient of Performance (COP) of the compressor.

[0004] Therefore, designing a simple and reliable content volume ratio adjustment solution has become a problem that needs to be solved in the field. Summary of the invention

[0005] In view of this, the present application proposes a twin-screw compressor, the compressor comprising:

[0006] A shell having an inner cavity, and an air inlet and an air outlet communicating with the inner cavity;

[0007] at least one pair of screws rotatably disposed in the inner cavity of the housing; and

[0008] An internal volume ratio adjustment mechanism is arranged on the shell at a position adjacent to the exhaust port and is used for step-adjusting the exhaust position of the compressor to adjust the internal volume ratio of the compressor.

[0009] Preferably, the side wall of the inner cavity comprises a plurality of axially arranged inner row connecting cavities, and the inner row connecting cavities communicate with the inner cavity and the exhaust port;

[0010] The internal volume ratio adjustment mechanism includes an axially movable adjustment member for blocking or opening the inner row connecting cavity.

[0011] Further preferably, the axial movement regulating member comprises a valve core and a driving device, and the driving device controls the axial movement of the valve core.

[0012] Further preferably, the driving device includes a spring and a pneumatic passage, the spring is connected to the valve core, and air is added or released in the pneumatic passage to drive the spring to extend or contract, thereby driving the valve core to move axially.

[0013] Further preferably, the pneumatic passage comprises an air intake control valve for controlling air filling of the pneumatic passage.

[0014] Further preferably, the air intake control valve is communicated with the exhaust port or with an external pipeline.

[0015] Further preferably, the pneumatic passage comprises an exhaust control valve for controlling air release from the pneumatic passage.

[0016] Further preferably, the exhaust control valve is communicated with the air intake port or with an external pipeline.

[0017] Further preferably, the twin-screw compressor comprises: a pair of primary screws and a pair of secondary screws;

[0018] The axial movement adjusting member is arranged in the cavity of the secondary screw at a position adjacent to the exhaust port.

[0019] The twin-screw compressor provided in the present application is provided with a volume ratio adjustment mechanism on the compressor housing near the compressor exhaust port, which is used to perform step-by-step adjustment on the exhaust position of the compressor to adjust the volume ratio of the compressor. This adjustment method can adapt to various working conditions of the compressor, eliminates components such as sliding valves, and reduces structural complexity and control complexity.

[0020] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings constituting a part of the present application are used to provide a further understanding of the present application, and the schematic implementation modes and descriptions of the present application are used to explain the present application. In the accompanying drawings:

[0022] Figure 1 This is a schematic diagram of the transverse structure of a twin-screw compressor according to a preferred embodiment of the present application;

[0023] Figure 2 This is a schematic diagram of the internal structure of a twin-screw compressor according to a preferred embodiment of the present application;

[0024] Figure 3 This is a schematic structural diagram of the content volume ratio adjustment mechanism of the preferred embodiment of the present application.

[0025] Figure numbers: 1-housing; 2-a pair of screws; 21-a pair of primary screws; 22-a pair of secondary screws; 3-internal volume ratio adjustment mechanism; 4-inner row of connecting cavities; 5-valve core; 6-spring; 7-pneumatic passage; 8-intake control valve; 9-exhaust control valve. DETAILED DESCRIPTION

[0026] The technical solution of the present application will be described in detail below with reference to the accompanying drawings and in combination with the implementation modes.

[0027] A screw compressor is a positive displacement gas compression machine whose working volume performs rotary motion. Its working cycle can be divided into three processes: suction, compression and exhaust. As the rotor (screw) rotates, each pair of meshing teeth successively completes the same working cycle.

[0028] Based on this, the present application provides a twin-screw compressor, such as Figure 1-3 As shown, the twin-screw compressor comprises: a shell 1, at least one pair of screws 2 and an internal volume ratio adjustment mechanism 3. The shell 1 has an inner cavity, and an air inlet and an exhaust port communicating with the inner cavity, and at least one pair of screws 2 are rotatably arranged in the inner cavity of the shell 1. The gas enters the inner cavity from the air inlet, and the at least one pair of screws 2 in the inner cavity compresses the gas and then discharges it from the exhaust port. In addition, the internal volume ratio adjustment mechanism 3 is arranged at a position adjacent to the exhaust port on the shell 1, and is used to perform step-by-step adjustment on the exhaust position of the compressor, thereby realizing the adjustment of the internal volume ratio of the compressor.

[0029] Specifically, in one embodiment, the side wall of the inner cavity includes a plurality of axially arranged inner row connecting cavities 4, and the inner row connecting cavities 4 connect the inner cavity and the exhaust port. The inner row connecting cavities 4 can be understood as an air guide passage, which can be specifically expressed as a bypass port and a bypass channel, which is not limited in this application. The "axial" here is relative to the inner cavity. Correspondingly, the content volume ratio adjustment mechanism 3 includes an axially movable adjustment member, which is used to sequentially block or open a plurality of axially arranged inner row connecting cavities 4 when it moves, so as to realize the step adjustment of the flow area between the inner cavity and the exhaust port, that is, to step-adjust the exhaust position of the compressor, thereby adjusting the content volume ratio of the compressor.

[0030] More specifically, the axially movable regulating member includes a valve core 5 and a driving device. The driving device controls the valve core 5 to move along the axial direction of the inner cavity. The valve core 5 is arranged at a position close to the inner row of connecting cavities 4. When the valve core 5 moves axially, each inner row of connecting cavities 4 can be blocked or released. The driving device specifically includes a spring 6 and a pneumatic passage 7. One end of the spring 6 is connected to the valve core 5, and the other end is fixed in position, for example, fixed in the side wall of the inner cavity, which is not limited in this application. A control valve for controlling the air filling or air release of the pneumatic passage 7 is provided in the pneumatic passage 7. When the control valve controls the air filling or air release of the pneumatic passage 7, the spring 6 expands or contracts under the action of the change in air pressure, thereby driving the valve core 5 to move axially to block or release each inner row of connecting cavities 4.

[0031] It can be understood that when the valve core 5 moves to open the inner row connecting cavity 4, it is equivalent to the exhaust position of the screw 2 being advanced, while the quality and flow of the gas do not change, but the exhaust pressure of the gas is reduced, that is, the volume of the compression end of the screw 2 becomes larger, thereby reducing the internal volume ratio. On the contrary, the valve core 5 moves to close the inner row connecting cavity 4 to increase the internal volume ratio, the principle is the same as above, and will not be repeated here.

[0032] Furthermore, the inner row connecting cavities 4 in the present application are multiple, and the number of openings can be set according to actual needs. When adjusting the internal volume ratio, the number of blocked or opened inner row connecting cavities 4 can also be controlled according to needs to form a step adjustment.

[0033] As for the method of adding air or releasing air to the pneumatic passage 7, the pneumatic passage 7 includes an intake control valve 8 for controlling the adding air to the pneumatic passage 7 and / or an exhaust control valve 9 for controlling the releasing air from the pneumatic passage 7. To simplify the structure, the intake control valve 8 can be communicated with the exhaust port of the compressor, and the gas discharged from the exhaust port of the compressor can be used to add air to the pneumatic passage 7. Similarly, the exhaust control valve 9 can be communicated with the suction port of the compressor, and the suction force of the suction port of the compressor can be used to release air from the pneumatic passage 7. Of course, the intake control valve 8 and / or the exhaust control valve 9 can also be communicated with an external pipeline, and the pneumatic passage 7 can be filled with air by an external high-pressure pipeline and / or the pneumatic passage 7 can be released by an external low-pressure pipeline.

[0034] In a specific embodiment, Figure 3 As shown, when the intake control valve 8 is opened, the high-pressure gas discharged from the exhaust side of the compressor enters the left area of ​​the valve core 5, and the spring 4 stretches accordingly, pushing the valve core 5 to move to the right in the figure and sequentially block one or more inner row connecting cavities 4 above to increase the internal volume ratio. When the exhaust control valve 9 is opened, the high-pressure gas on the left side of the valve core 5 is discharged to the suction side of the compressor. At this time, under the action of the exhaust pressure, the valve core 5 overcomes the sum of the elastic force of the spring 4 and the pressure on the suction side, moves to the left in the figure and sequentially opens one or more inner row connecting cavities 4 above to reduce the internal volume ratio.

[0035] In addition, the twin-screw compressor in the present application can be a single-stage screw compressor or a two-stage screw compressor. If the compressor is a two-stage screw compressor, the screw 2 correspondingly includes a stack of primary screws 21 and a pair of secondary screws 22, and the inner cavity also correspondingly includes the cavity of the primary screw 21 and the cavity of the secondary screw 22, and the exhaust port of the compressor is connected to the cavity of the secondary screw 22. The valve core 5 in the axial movement adjustment needs to be arranged in the cavity of the secondary screw 22, and is specifically arranged below the secondary screw 22, and in the same direction as the secondary screw 22. The inner row connecting cavity 4 is opened in the cavity of the secondary screw 22, and the valve core 5 is controlled to move to block or open the inner row connecting cavity 4 to adjust the gas discharge pressure of the secondary screw 22, thereby adjusting the internal volume ratio on the secondary screw 22 side.

[0036] In addition, the twin-screw compressor in the present application further includes a speed regulating mechanism (not shown in the figure) and / or a gas regulating mechanism (not shown in the figure), the speed regulating mechanism is used to adjust the speed of the screw 2, and the gas regulating mechanism is used to adjust the suction flow of the compressor. If the adjustment range of the existing content volume ratio adjustment mechanism 3 is not sufficient to meet the operating requirements, the content volume ratio adjustment mechanism 3 can be made to cooperate with the speed regulating mechanism and / or the gas regulating mechanism to achieve a more comprehensive adjustment of the compressor working mode.

[0037] The twin-screw compressor provided in the present application is provided with a volume ratio adjustment mechanism on the compressor housing near the compressor exhaust port, which is used to perform step-by-step adjustment on the exhaust position of the compressor to adjust the volume ratio of the compressor. This adjustment method can adapt to various working conditions of the compressor, eliminates components such as sliding valves, and reduces structural complexity and control complexity.

[0038] Based on the structure of the twin-screw compressor of the present application, when the compressor is working, the working state of the compressor can be monitored, and the working state of the intake control valve 8 and the exhaust control valve 9 can be automatically or manually adjusted at any time according to the working state of the compressor to adapt to various working conditions of the compressor. Figure 3 As shown, the present application can at least implement the following embodiments in the following working conditions:

[0039] Embodiment 1:

[0040] When the compressor is turned on, the intake control valve 8 and the exhaust control valve 9 are both opened, and the intake and exhaust sides of the pneumatic passage 7 are both opened. At this time, the compressor is equivalent to being in a hot gas bypass state, that is, a part of the hot gas at the exhaust end of the compressor is bypassed to the intake end, so that a certain proportion of hot gas is mixed into the gas at the intake end, thereby optimizing the performance of the compressor.

[0041] When the compressor is stopped, in order to shorten the time for the motor to reverse, the intake control valve 8 and the exhaust control valve 9 are also opened so that the pressure in the compressor cavity can be quickly balanced.

[0042] Embodiment 2:

[0043] When the evaporation temperature of the compressor is lower than a certain temperature, the intake control valve 8 is opened and the exhaust control valve 9 is closed, that is, air is added to the pneumatic passage 7 while air is not released from the pneumatic passage 7, so that the valve core 5 moves to block the inner row connecting cavity 4 to increase the internal volume ratio, and the energy efficiency ratio of the compressor is changed by changing the internal volume ratio. The temperature can be set as needed, for example, it can be set to -25°C.

[0044] Specifically, when the evaporation temperature is too low, the evaporation pressure will also decrease, resulting in an increase in the suction volume of the compressor and a decrease in the suction quality. At the same time, a too low evaporation temperature will also increase the compression ratio of the compressor, resulting in an increase in the unit refrigeration power consumption and a decrease in the energy efficiency ratio. This not only increases energy consumption, but may also cause damage to the compressor. By increasing the content volume ratio, it can better adapt to the operating conditions when the evaporation temperature is too low. This helps to reduce the power consumption and wear of the compressor and improve the energy efficiency ratio and stability of the system. At the same time, when the evaporation temperature is too low, increasing the content volume ratio can reduce the workload of the compressor.

[0045] Embodiment 3:

[0046] When the evaporation temperature of the compressor is higher than a certain temperature, the intake control valve 8 is closed and the exhaust control valve 9 is opened, that is, the air is released from the pneumatic passage 7 to the outside, so that the valve core 5 moves to release the inner row connection chamber 4. For the same reason as above, when the evaporation temperature of the compressor is higher than a certain temperature, the internal volume ratio of the compressor needs to be lowered. The temperature here can be specifically set to -20°C.

[0047] The preferred embodiments of the present application are described in detail above; however, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, a variety of simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the protection scope of the present application.

[0048] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0049] In addition, the various implementation modes of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A twin-screw compressor, comprising: A housing (1), the housing (1) having an inner cavity, and an air inlet and an air outlet communicating with the inner cavity; At least one pair of screw rods (2), the at least one pair of screw rods (2) being rotatably disposed in the inner cavity of the housing (1); and An internal volume ratio adjustment mechanism (3) is arranged on the shell (1) at a position adjacent to the exhaust port and is used to stepwise adjust the exhaust position of the compressor to adjust the internal volume ratio of the compressor.

2. The twin-screw compressor according to claim 1, characterized in that The side wall of the inner cavity comprises a plurality of inner row connecting cavities (4) arranged axially, and the inner row connecting cavities (4) communicate with the inner cavity and the exhaust port; The internal volume ratio adjustment mechanism (3) comprises an axially movable adjustment member, which is used to block or open the inner row connecting cavity (4).

3. The twin-screw compressor according to claim 2, characterized in that The axial movement regulating member comprises a valve core (5) and a driving device, and the driving device controls the axial movement of the valve core (5).

4. The twin-screw compressor according to claim 3, characterized in that The driving device comprises a spring (6) and a pneumatic passage (7); the spring (6) is connected to the valve core (5); air is added or released in the pneumatic passage (7) to drive the spring (6) to expand or contract, thereby driving the valve core (5) to move axially.

5. The twin-screw compressor according to claim 4, characterized in that The pneumatic passage (7) includes an air intake control valve (8) for controlling the air supply to the pneumatic passage (7).

6. The twin-screw compressor according to claim 5, characterized in that The air intake control valve (8) is in communication with the exhaust port or with an external pipeline.

7. The twin-screw compressor according to claim 4, characterized in that The pneumatic passage comprises an exhaust control valve (9) for controlling the exhaust of the pneumatic passage (7).

8. The twin-screw compressor according to claim 7, characterized in that The exhaust control valve (9) is in communication with the air intake port or with an external pipeline.

9. The twin-screw compressor according to claim 2, characterized in that The twin-screw compressor comprises: a pair of primary screws (21) and a pair of secondary screws (22); The axial movement adjusting member is arranged in the cavity of the secondary screw (22) at a position adjacent to the exhaust port.

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