JP5322016B2 - Single screw multistage compressor and refrigeration / cooling system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw compressor capable of striking a balance between high efficiency and long service life. <P>SOLUTION: In the single machine screw type multistage compressor 5 in which a high-stage compressor 3 and a low-stage compressor 7 comprising screw rotors and a drive motor 25 are integrally combined in series, the low-stage compressor 7 is provided with a low-stage economizer port 70 to which a low-stage economizer cooler is connected. The motor 25 is connected to a suction side of the low-stage compressor. A balance passage 80 introducing a pressure of an intermediate pressure chamber 63 connecting a discharge port 59 of the low-stage compressor and a suction port 65 of the high-stage compressor or a pressure of a compression stroke part of the high-stage compressor to a motor chamber 82 is provided. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a so-called single-unit multi-stage screw compressor configured on a shaft having the same core and driven by a single motor, and in particular, an economizer cooler is connected to the low-stage compressor and the high-low stage compressor is The present invention relates to a multistage screw compressor in which a theoretical air volume ratio (displacement ratio) is set larger than that in the case where an economizer is not connected to a conventional low stage compressor, and a refrigeration / cooling system configured using the multistage screw compressor.

  In order to obtain a lower freezing temperature, a two-stage compression mechanism is used for food freezing, vacuum freeze drying, process cooling, and the like. In addition, a so-called single-unit compressor in which these two-stage compressors are integrated is used from the viewpoint of miniaturization and weight reduction. For example, a single-machine multi-stage screw compressor in which a two-stage screw compressor is integrally combined with a drive motor is known, and various proposals have been made for this single-machine multi-stage screw compressor.

  For example, Patent Document 1 (Japanese Patent No. 2781523) discloses an invention relating to a two-stage screw compressor used in a refrigeration apparatus, in which the number of teeth of a male and female screw rotor of a single-stage compressor is indicated. 5 (male side) and 6 (female side), and the number of teeth of the male and female screw rotors of the two-stage compressor is 4 (male side) and 6 (female side). A technique for reducing noise by differentiating the noise is shown.

  In order to improve the coefficient of performance (hereinafter referred to as COP) of a multistage compressor, an economizer circuit is added to the compressor. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2006-258397) discloses that As shown in FIG. 10, the suction volume is controlled so that the compression ratios of a plurality of compressors are equal in a multi-stage compressor 03 in which a low-stage compressor 01 and a high-stage compressor 02 are connected in series. In addition, a technique is shown in which a low-stage economizer circuit 04 and a high-stage economizer circuit 05 are connected to a low-stage compressor 01 and a high-stage compressor 02, respectively, and an intermediate cooler 06 is further provided.

  Further, in Patent Document 3 (Japanese Patent Laid-Open No. 2005-83260), in a single-stage screw type compressor that is not multistage, as shown in FIG. 11, refrigerant is efficiently supplied from the economizer port 010 to the screw compressor 011. The port shape for supply is shown, where it is shown that the economizer port 010 is formed along the length direction of the blade 013 of the screw rotor 012.

Japanese Patent No. 2781523 JP 2006-258397 A (FIG. 10) Japanese Patent Laid-Open No. 2005-83260

  However, the two-stage screw compressor disclosed in Patent Document 1 shows a structure in which a first-stage compressor, a two-stage compressor, and a drive motor are integrally assembled in series. It is a technology that suppresses vibration noise by differentiating the combination of the number of teeth of the male and female screw rotors and the number of teeth of the male and female screw rotors of the two-stage compressor. A high-efficiency compressor and a two-stage screw compressor were used. There is no indication of technology to increase the refrigeration capacity of the refrigerator by the ecomizer effect.

Further, in Patent Document 2, a low-stage economizer circuit 04 and a high-stage economizer circuit 05 are connected to a low-stage compressor 01 and a high-stage compressor 02, respectively, to improve the refrigeration capacity by the ecomizer effect. Although shown, the technique of Patent Document 2 controls the suction volume so that the compression ratios of a plurality of compressors are equal, and increases the air volume ratio (displacement ratio) of the high and low stage side compressors. Thus, it is not shown that the compression ratio is increased, the economizer effect of the low stage compressor is enhanced to increase the refrigerating capacity, and the capacity of the high stage compressor is reduced.
Further, there is no disclosure of a specific installation structure of the economizer port, and no practical structure is shown.

  Further, in Patent Document 3, the economizer port 010 is formed along the length direction of the screw blades 013 of the screw rotor 012 in order to efficiently supply the refrigerant from the economizer port 010 to the screw compressor. However, when the number of blades is small, processing is possible. There is a problem that it is difficult to process the economizer port along the length direction and it is difficult to supply a large amount of economizer refrigerant to the screw compressor.

  As described above, in Patent Documents 1 to 3, an economizer circuit is connected in a screw compressor, and an economizer circuit is connected to a low-stage compressor and a high-stage compressor in a screw-type two-stage compressor, respectively. However, when an economizer circuit is connected to a single screw type two-stage compressor, the relationship between the optimum air flow ratio between the low-stage compressor and the high-stage compressor, and the connection of the economizer The structure that enables the refrigerant to flow efficiently into the compressor by increasing the opening area of the economizer port is not fully shown, and it can be applied to refrigeration and cooling devices to achieve high refrigeration capacity. There is a further need for practical improvements to such a single screw two stage compressor.

  Therefore, the present invention has been made in view of such a background, and an economizer is connected to each of the low-stage compressor and the high-stage compressor, and the air volume ratio between the low-stage compressor and the high-stage compressor. In other words, the theoretical displacement ratio of the low-stage compressor is set to be larger than that when the economizer is not connected to the conventional low-stage compressor, and the economizer effect is achieved in the low-stage compressor by setting the low-stage compressor to a high compression ratio. It is an object of the present invention to provide a screw-type multistage compressor having a single machine structure that can be effectively exhibited.

  In addition, an economizer port structure that allows refrigerant from the economizer cooler to more easily flow into the low-stage compressor and discharge from the low-stage compressor in order to increase the compression of the low-stage compressor and exert the economizer effect. It is an object of the present invention to provide a single-screw multi-stage compressor provided with a support structure and the like for dealing with a thrust load acting on a low-stage compressor accompanying an increase in pressure.

  Furthermore, this invention makes it a subject to provide the refrigerating / cooling system which exhibits high COP by comprising a refrigerating / cooling circuit using the single screw type multistage compressor.

  In order to solve the above problems, a reference invention of a single-screw multi-stage compressor according to the present invention is a series of a low-stage compressor, a high-stage compressor, and a drive motor that are made up of a pair of male and female screw rotors. In the combined single-screw multistage compressor, the low stage compressor is provided with a low stage economizer port to which a low stage economizer cooler is connected, and the high stage compressor is provided with a high stage economizer cooler. Is provided, and a theoretical air volume ratio between the low-stage compressor and the high-stage compressor is set to approximately 3.2 or more.

  Further preferably, the reference invention is characterized in that a theoretical air volume ratio between the low-stage compressor and the high-stage compressor is set to 3.2 to 4.5.

According to such a reference invention, since the economizer cooler is connected to the low stage compressor and the refrigerant flows into the compressor, compared to the case where the conventional economizer is not connected so that the refrigerant easily flows, It is necessary to set a large air flow balance of the low stage compressor with respect to the high stage compressor.
In other words, since the high-stage compressor further compresses the fluid compressed by the low-stage compressor, the air volume (displacement amount) is smaller than that of the low-stage compressor. The air volume ratio in the machine is set in a balanced manner so that the performance is optimally exhibited.

  In the case of a conventional single-stage two-stage screw compressor in which an economizer is not connected to a low-stage compressor, COP under general operating conditions (evaporation temperature −50 to −20 ° C., condensation temperature 30 to 45 ° C.) From this aspect, the theoretical air volume ratio between the low stage compressor and the high stage compressor (the theoretical air volume ratio of the low stage compressor to the high stage compressor) was set to 3.0 or less. That is, as shown in the relationship between the airflow ratio and COP in FIG. 9, the airflow ratio becomes maximum at 2.6 to 2.7 without the economizer of the conventional low-stage compressor. It was used at 0 or less.

  However, when an economizer is connected to a low-stage compressor, it is preferable to increase the air volume ratio so that the air volume ratio is 3.2 or more as shown in FIG. In order to exhibit a COP exceeding the maximum COP in the case, it is optimal to set it in the range of 3.2 to 4.5.

In this way, the COP can be improved by connecting the economizer to the low stage compressor and optimizing by increasing the air flow ratio of the low stage compressor.
Furthermore, the increase in the air flow ratio of the low-stage compressor can be achieved by increasing the size of the low-stage compressor or by reducing the size of the high-stage compressor, so that the high-stage compressor can be downsized. As a result, the safety of the single screw compressor is increased, and the installation can be performed without any restriction on the installation location.

  1st invention concerning the single machine screw type multistage compressor of this invention is the single machine screw which combined the low stage compressor and high stage compressor which consist of a male and female pair of screw rotors, and the drive motor integrally in series. In the multi-stage compressor, the low-stage compressor is provided with a low-stage economizer port to which a low-stage economizer cooler is connected, the motor is constituted by a hermetic motor, and the motor is configured as the low-stage compressor. The pressure in the intermediate pressure chamber connecting the discharge port of the low-stage compressor and the suction port of the high-stage compressor, or the pressure in the compression stroke portion of the high-stage compressor It is characterized in that a balance passage leading to is provided.

  If an economizer cooler is connected to the low stage compressor and the air volume ratio is made larger than before, for example, if the air volume ratio is increased as in the invention of claim 1, the discharge pressure of the low stage compressor increases. Since the pressure in the intermediate pressure chamber that connects the discharge port of the low-stage compressor and the suction port of the high-stage compressor becomes higher than before, a thrust load that pushes the low-stage compressor toward the motor acts, so the low-stage compressor The problem is that the life of the compressor bearing is reduced.

  However, according to the first aspect of the present invention, the motor is constituted by a hermetic motor, and the pressure in the intermediate pressure chamber connecting the discharge port of the low stage compressor and the suction port of the high stage compressor, or the high stage By guiding the pressure in the compression process section of the compressor to the hermetic motor chamber, the thrust load acting in the motor direction of the low-stage compressor is reversed so that the thrust load acts in the opposite direction. By balancing the above, it is possible to reduce the load acting on the bearing of the low-stage compressor and achieve a long life. Thus, both high efficiency and long life can be achieved.

  Further preferably, in the first invention, the refrigerant-dissolved lubricating oil supplied to the bearing of the low-stage compressor is returned to the motor chamber of the hermetic motor. According to the invention, When using oil in which refrigerant is dissolved as lubricating oil, if the oil is supplied to the bearing of the low-stage compressor and then returned to the rotor of the low-stage compressor, the dissolved refrigerant will jet out and the performance will be significantly reduced. However, by returning the refrigerant-dissolved lubricating oil supplied to the bearing of the low-stage compressor to the hermetic motor chamber, the motor chamber has the pressure of the intermediate pressure chamber or the compression process section of the high-stage compressor. Since the pressure is guided to a high pressure, it is possible to avoid the problem that the refrigerant-dissolved lubricating oil is ejected and the performance is remarkably deteriorated.

Preferably, in the first invention, the screw rotor of the low-stage compressor is horizontally arranged, and the screw rotor of the high-stage compressor is vertically arranged perpendicular to the arrangement direction of the low-stage compression screw rotor, The balance passage is disposed below a screw rotor disposed horizontally in the low-stage compressor.
Since the low stage side is arranged horizontally and the high stage side is arranged vertically as described above, the balance passage can be installed using the space below the horizontally arranged low stage screw rotor. A single-screw multi-stage compressor in which a low-stage compressor, a high-stage compressor, and a drive motor are integrally combined in series can be configured compactly without increasing the size.

  Next, a third aspect of the invention relates to a refrigeration / cooling system, which is formed by the single-screw multistage compressor according to any one of claims 1 to 6, a condenser, an evaporator, and expansion means. A high-stage economizer circuit and a low-stage economizer circuit in the main refrigerant circuit on the downstream side of the condenser and on the upstream side of the evaporator. The high stage economizer passage is connected to the high stage economizer port of the high stage compressor, and the low stage economizer path of the low stage economizer circuit is connected to the low stage economizer port of the low stage compressor. Features.

  According to this invention, since the single-screw multistage compressor described above is provided, the air volume ratio of the low stage compressor is set large, and the economizer cooler is connected to the low stage compressor. COP of refrigeration / cooling system is improved. Furthermore, it becomes possible to construct a system in which the high-stage compressor is reduced in size and capacity, which increases safety and increases the degree of freedom of the installation location.

  Furthermore, by extending the bearing life of the low-stage compressor and expanding the economizer effect by increasing the opening area of the economizer port of the low-stage compressor, it is possible to achieve both long life and high efficiency of the refrigeration / cooling system. Can be achieved.

  According to the present invention, an economizer is connected to each of the low-stage compressor and the high-stage compressor, and the air volume ratio between the low-stage compressor and the high-stage compressor, that is, the theoretical displacement ratio of the high-low stage compressor is conventionally set. A single-unit screw that can be set larger than when an economizer is not connected to a low-stage compressor and the economizer effect can be effectively demonstrated in the low-stage compressor with the low-stage compressor as a high compression ratio. A multistage compressor can be provided.

  In addition, an economizer port structure that allows refrigerant from the economizer cooler to more easily flow into the low-stage compressor and discharge from the low-stage compressor in order to increase the compression of the low-stage compressor and exert the economizer effect. It is possible to provide a single-screw multi-stage compressor provided with a support structure for dealing with a thrust load acting on a low-stage compressor accompanying an increase in pressure.

  Furthermore, according to the present invention, a refrigeration / cooling system that exhibits high COP can be provided by configuring a refrigeration / cooling circuit using the single-screw multistage compressor.

It is side surface sectional drawing which shows embodiment of the single machine screw type multistage compressor concerning this invention. It is a plane sectional view showing an embodiment of a single machine screw type multistage compressor concerning the present invention. It is an AA line expanded sectional view of FIG. FIG. 3 is an enlarged sectional view taken along line B-B in FIG. 2. 1 is a schematic configuration diagram of a refrigeration / cooling system using a single-screw multi-stage compressor according to an embodiment of the present invention. FIG. 6 is a Mollier diagram of the refrigeration / cooling system of FIG. 5. It is a schematic block diagram which shows other embodiment of the refrigerating / cooling system using the single-machine screw type multistage compressor concerning embodiment of this invention. FIG. 8 is a Mollier diagram of the refrigeration / cooling system of FIG. 7. It is a characteristic view which shows the relationship between the air volume ratio of a low stage compressor and a high stage compressor, and a coefficient of performance (COP). It is explanatory drawing of a prior art. It is explanatory drawing of a prior art.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Only.

FIG. 1 is a side sectional view showing an embodiment of a single-machine screw type multistage compressor according to the present invention, and FIG. 2 is a plan sectional view showing an embodiment of a single-machine screw type multistage compressor.
3 is an enlarged sectional view taken along line AA in FIG. 1, and FIG. 4 is an enlarged sectional view taken along line BB in FIG.
FIG. 5 is a schematic configuration diagram of a refrigeration / cooling system using a single-screw multistage compressor according to an embodiment of the present invention, and FIG. 6 is a Mollier diagram of the refrigeration / cooling system of FIG.
FIG. 7 is a schematic configuration diagram showing another embodiment of a refrigeration / cooling system using a single-screw multistage compressor according to an embodiment of the present invention, and FIG. 8 is a Mollier diagram of the refrigeration / cooling system of FIG. It is. FIG. 9 is a characteristic diagram showing the relationship between the air flow ratio between the low-stage compressor and the high-stage compressor and the coefficient of performance (COP).

As shown in FIG. 1, a single-screw two-stage compressor 5 including a low-stage compressor 1 and a high-stage compressor 3 as a single-screw multistage compressor will be described.
The low-stage compressor 1 is housed in a low-stage compressor casing 11 so that a pair of male and female screw rotors 7 and 9 can be rotated, and the high-stage compressor 3 includes a pair of male and female screw rotors 13, 15 is housed in a high-stage compressor casing 17 so as to be meshed and rotatable. As shown in FIGS. 1 and 2, the pair of male and female screw rotors 7 and 9 of the low-stage compressor 1 are arranged side by side, and the pair of male and female screw rotors 13 of the high-stage compressor 3. , 15 are arranged side by side in the direction perpendicular to each other, with the lower stage side arranged horizontally and the higher stage side arranged vertically.

  The rotor shaft 19 of the low-stage male rotor 7 of the low-stage compressor 1 and the rotor shaft 21 of the high-stage male rotor 13 of the high-stage compressor 3 are coupled via a spline coupling 23 so as to be integrally rotatable. That is, the low-stage compressor 1 and the high-stage compressor 3 have a split shaft structure and are integrally coupled by the spline coupling 23, so that the low-stage compressor 1 and the high-stage compressor 3 are connected by a continuous integral shaft. Compared to the structure, the machining accuracy of the shaft is not required.

The rotor shaft 19 of the low-stage male rotor 7 also serves as the rotating shaft 27 of the motor (drive motor) 25 and has an integral shaft structure. The motor 25 is configured as a sealed motor 25 by attaching a motor casing 29 to the low-stage compressor casing 11 in an airtight state. The motor 25 is a so-called IPM motor in which a permanent magnet is embedded in the motor rotor. It is configured.
The rotating shaft 27, the rotor shaft 19, and the rotor shaft 21 of the motor 25 rotate together.

The rotary shaft 27 of the motor 25 is supported by the low-stage compressor casing 11 by a bearing 31, and the rotor shaft 19 on the discharge side of the low-stage male rotor 7 is supported by the intermediate casing 33 by a bearing 35. The rotor shaft 37 is supported on the low-stage compressor casing 11 by a bearing 39 and on the intermediate casing 33 by a bearing 41.
The rotor shaft 21 of the high-stage male rotor 13 is supported on the high-stage compressor casing 17 by a bearing 43 and supported on the discharge port casing 47 by a bearing 45. Similarly, the rotor shaft 22 of the high stage female rotor 15 is supported by the high stage compressor casing 17 by the bearing 49 and supported by the discharge port casing 47 by the bearing 51.

  An end casing 53 that covers the end portion is attached to an end portion of the rotor shaft 21 of the high-stage male rotor 13, and a lid 55 is further attached.

The low-stage compressor casing 11 is provided with a suction port 57 for working fluid (refrigerant), and is provided so as to be opposed to the end surfaces of the low-stage male rotor 7 and the low-stage female rotor 9 on the motor 25 side. It has been.
The discharge port 59 of the low-stage compressor 1 is provided on the end surface of the low-stage male and female rotors 7 and 9 on the side opposite to the suction port 57 and communicates with the intermediate pressure chamber 63 via the discharge passage 61. .
A suction port 65 of the high-stage compressor 3 opens into the intermediate pressure chamber 63 so that the refrigerant flows in from the end faces of the high-stage male and female rotors 13 and 15.
Further, a discharge port 67 (FIG. 2) of the high stage compressor 3 is formed in the discharge port casing 47 so that the refrigerant compressed by the high stage compressor 3 is discharged.

  The motor casing 29, the low-stage compressor casing 11, the intermediate casing 33, the high-stage compressor casing 17, the discharge port casing 47, the end casing 53, and the lid 55 are combined and joined together by fastening means such as bolts. Assembled into a single machine structure.

(Low stage economizer, High stage economizer)
Next, the low stage economizer port 70 and the high stage economizer port 72 will be described with reference to FIGS.
The low-stage economizer port 70 is a port for supplying refrigerant from the low-stage economizer cooler (described in a refrigeration system described later) into the compression chamber of the low-stage compressor 1, and is formed in one place in the intermediate casing 33. The low-stage economizer port inlet 74 communicates with the male economizer port 76 of the low-stage male rotor 7 and the female economizer port 78 of the low-stage female rotor 9.

The male economizer port 76 and the female economizer port 78 are respectively formed in the intermediate casing 33 and are in the axial direction of the low-stage male / female rotors 7 and 9 and are opposite to the suction port 57. 7 and 9 are open at positions facing the end faces.
The male-side and female-side economizer ports 76 and 78 are formed in a size located between the screw blades formed on the male and female rotors 7 and 9, respectively (see FIG. 3).

  Thus, since the low stage economizer port 70 is formed facing the axial end surfaces of the male and female rotors 7 and 9, even if the number of screw blades of the rotor increases and the blade thickness decreases. Further, it is easy to process the port through which the refrigerant flows between the screw blades, and it is easy to cope with the increase / decrease in the number of ports, and it is easy to cope with the increase in the refrigerant inflow amount of the economizer.

Further, since the refrigerant flows into the low-stage compressor 1 from both the male-side economizer port 76 and the female-side economizer port 78, the opening area of the low-stage economizer port 70 can be increased, so that the economizer The amount can be increased.
Furthermore, since the low-stage economizer port 70 is formed together in the intermediate casing 33 on the end face side of the male / female rotors 7 and 9, the economizer port can be easily processed and manufactured.

  Furthermore, since the male side and female side economizer ports 76 and 78 are formed in the size located between the screw blades of the male and female rotors 7 and 9, respectively, the compression stroke of the male rotor 7 and the female rotor 9 is achieved. The refrigerant can surely flow in.

  The high stage economizer port 72 is formed in the high stage compressor casing 17 in which the intermediate pressure chamber 63 is formed, and refrigerant is sucked into the high stage compressor 3 from the intermediate pressure chamber 63.

(Balance passage)
Next, the balance passage 80 will be described with reference to FIG.
The balance passage 80 is a passage that communicates the intermediate pressure chamber 63 and the motor chamber 82 in the motor casing 29, and guides the high-pressure refrigerant in the intermediate pressure chamber 63 into the motor chamber 82. Further, the pressure in the compression stroke portion of the high stage compressor 3 may be guided to the motor chamber 82 instead of the pressure in the intermediate pressure chamber 63.

  When a low-stage economizer is connected to the low-stage compressor 1 to increase the air flow ratio, the intermediate pressure chamber 63 that connects the discharge port 59 of the low-stage compressor 1 and the suction port 65 of the high-stage compressor 3. The internal pressure becomes higher than before, and a thrust load that presses the low-stage compressor 1 toward the motor 25 acts, so that the life of the bearings 31, 35, 39, 41 of the low-stage compressor 1 is reduced. Is likely to occur.

  However, the motor 25 is constituted by a hermetic type, and the pressure in the intermediate pressure chamber 63 or the pressure in the compression stroke portion of the high stage compressor 3 is guided to the hermetically sealed motor chamber 82, so that the motor of the low stage compressor 1 is provided. Since the thrust load acting in the 25 direction is counteracted so as to cancel out, the load acting on the bearings 31, 35, 39, 41 of the low stage compressor 1 by balancing the thrust load of the low stage compressor 1 It is possible to extend the life by reducing the above.

  The bearing 31 of the low-stage compressor 1 is supplied with refrigerant-dissolved lubricating oil and is returned to the motor chamber 82 of the hermetic motor. Refrigerant-dissolved lubricating oil is stored at the bottoms of the motor chamber 82 and the intermediate pressure chamber 63, and the respective storage portions are communicated with each other by a communication path 84. The oil in the motor chamber 82 can be easily returned from the intermediate pressure chamber 63 to the high stage compressor 3 by the communication passage 84.

  Further, as shown in FIG. 1, the male and female rotors 7 and 9 of the low stage compressor 1 are horizontally arranged, and the male and female rotors 13 and 15 of the high stage compressor 3 are vertically arranged. Thus, the balance passage 80 and the communication passage 84 can be installed using the space below the horizontally disposed low-stage screw rotor, so that the single screw multi-stage compressor can be made compact without increasing the size. A balance passage 80 and a communication passage 84 can be installed.

  When the oil in which the refrigerant is dissolved is used as the lubricating oil, when the oil is supplied to the bearing 31 of the low stage compressor 1 and returned to the male / female rotors 7 and 9 of the low stage compressor 1, the dissolved refrigerant is ejected. However, it is easy to cause a problem that the performance is remarkably deteriorated. However, by returning the refrigerant-dissolved lubricating oil supplied to the bearing 31 of the low-stage compressor 1 into the hermetic motor chamber 82, the motor chamber 82 has an intermediate pressure. Since the pressure in the chamber 63 or the pressure in the compression stroke portion of the high stage compressor 3 is led to a high pressure, the problem that the refrigerant-dissolved lubricating oil is ejected and the performance is remarkably deteriorated can be avoided.

(Male and female rotor screw blades)
Next, refer to FIG. 3 for the cross-sectional shape and meshing state of the screw blades of the low-stage male rotor 7 and the low-stage female rotor 9, and for the high-stage male rotor 13 and the high-stage female rotor 15, see FIG. I will explain.
As shown in FIGS. 3 and 4, the low-stage male rotor 7 has five blades, the low-stage female rotor 9 has six blades, and the high-stage male rotor 13 has five blades, and the high-stage female rotor 15 has five blades. Are also 6 blades, and the high stage male rotor 13 is also composed of 5 blades.
Thus, both the low-stage compressor 1 and the high-stage compressor 3 are set to the same number by combining 5 sheets and 6 sheets. Therefore, a long meshing length can be obtained by a combination of 5 sheets and 6 sheets, so that the sealing performance can be improved and a high compression compressor can be handled.

  Further, since both the low-stage compressor 1 and the high-stage compressor 3 are a combination of 5 and 6, the discharge pulsation frequencies of the low-stage compressor 1 and the high-stage compressor 3 coincide with each other, resulting in vibration noise. Therefore, when the spline coupling 23 is coupled, the rotational phases of both the low-stage compressor 1 and the high-stage compressor 3 are appropriately shifted and combined.

Further, as shown in FIG. 3, the male economizer port 76 is formed so as to open between the screw blades of the low-stage male rotor 7, and the female economizer port 78 is the screw of the low-stage female rotor 9. It is formed so as to open between the blades.
3 and 4 indicate the rotation directions of the respective rotors.

(Air volume ratio)
Next, the air volume ratio between the low stage compressor 1 and the high stage compressor 3 will be described.
Since the high stage compressor 3 further compresses the fluid such as the refrigerant compressed by the low stage compressor 1, the air volume (displacement amount) is smaller than that of the low stage compressor 1. The air volume ratio and the air volume ratio in the high stage compressor 3 are set in a balanced manner so that the performance is optimally exhibited.

  In the case of the conventional single-stage two-stage screw compressor in which the economizer is not connected to the low-stage compressor 1, the operation is performed under general operating conditions (evaporation temperature −50 to −20 ° C., condensation temperature 30 to 45 ° C.). From the viewpoint of COP, the theoretical air volume ratio between the low stage compressor and the high stage compressor (the theoretical air volume ratio of the low stage compressor to the high stage compressor) was set to 3.0 or less. That is, as shown in the relationship between the airflow ratio and COP in FIG. 9, the airflow ratio becomes maximum at 2.6 to 2.7 without the economizer of the conventional low-stage compressor. It was used at 0 or less.

  However, when an economizer is connected to the low-stage compressor 1, it is preferable to increase the air volume ratio so that the air volume ratio is 3.2 or more as shown in FIG. In order to exhibit a COP exceeding the maximum COP in the case of, it is optimal to set it in the range of 3.2 to 4.5.

Thus, COP can be improved by connecting the economizer to the low stage compressor 1 and increasing and optimizing the air flow ratio of the low stage compressor.
Further, the increase in the air flow ratio of the low stage compressor 1 can be achieved by increasing the size of the low stage compressor 1 or by downsizing the high stage compressor 3. The size can be reduced, the safety of the screw type two-stage compressor 5 is increased, and the installation can be performed without being limited by the installation location.

(Refrigeration / cooling system)
Next, the refrigeration / cooling system will be described with reference to FIGS.
FIG. 5 is a configuration diagram in the case where the single screw type two-stage compressor 5 is applied to a refrigeration / cooling system, and is an example in which ammonia is used as a refrigerant.
The refrigeration system 100 includes a single refrigerant screw type two-stage compressor 5, a condenser 102, an evaporator 104, and an expansion means 106, and a main refrigerant circuit 108 formed downstream of the condenser 102. The main refrigerant circuit 108 includes a high-stage economizer circuit 110 and a low-stage economizer circuit 112 on the side and upstream of the evaporator 104.

  The high stage economizer passage 114 of the high stage economizer circuit 110 is connected to the high stage economizer port 72 of the high stage compressor 3, and the low stage economizer path 116 of the low stage economizer circuit 112 is connected to the low stage compressor. The stage economizer port 70 is connected.

  In the high-stage economizer circuit 110, the refrigerant branched from the main refrigerant circuit 108 is guided to the high-stage economizer expansion valve 118 to be depressurized, becomes a low-pressure low-temperature refrigerant, and flows into the high-stage economizer cooler 120 to enter the main refrigerant. The refrigerant in the circuit 108 is cooled and flows into the high stage economizer port 72 of the high stage compressor 3 through the high stage economizer passage 114.

  Similarly, in the low-stage economizer circuit 112, a part of the refrigerant discharged from the high-stage economizer cooler 120 is diverted and led to the low-stage economizer expansion valve 122 to be depressurized to become low-pressure and low-temperature refrigerant. The refrigerant that flows into the low-stage economizer cooler 124 and cools the refrigerant discharged from the high-stage economizer cooler 120, passes through the low-stage economizer passage 116, and enters the low-stage economizer port 70 of the low-stage compressor 1. It is configured to flow in.

FIG. 6 is a Mollier diagram of the refrigeration cycle of FIG. 5, and the flow of the refrigerant will be described with reference to FIGS. 5 and 6.
The refrigerant that has been compressed by the screw-type two-stage compressor 5 to high pressure and high temperature (Td2) flows into the condenser 102 and releases its heat to the outside to condense (condensation temperature Tc) to liquefy and lower the temperature. (TL), and then the refrigerant is diverted, and the diverted refrigerant is decompressed and cooled (Tm2) by the high stage economizer expansion valve 118 and flows into the high stage economizer port 72 through the high stage economizer cooler 120. . Moreover, the refrigerant | coolant which remained without being diverted is cooled by the high stage economizer cooler 120, and is temperature-reduced (TL1).

  Further, a part of the refrigerant cooled and lowered in temperature (TL1) by the high-stage economizer cooler 120 is further divided, and the divided refrigerant is reduced in temperature and reduced in pressure by the low-stage economizer expansion valve 122 (Tm1). Then, the air flows into the low-stage economizer port 70 through the low-stage economizer cooler 124. Further, the refrigerant remaining without being divided is cooled by the low stage economizer cooler 124 to be lowered in temperature (TL2).

  The refrigerant from the low-stage economizer cooler 124 is decompressed and cooled (Te) by the expansion means 106 of the main refrigerant circuit 108 and flows into the evaporator 104. The evaporator 104 takes heat from the outside and evaporates (evaporation temperature Te) to be separated into a gas refrigerant and a liquid refrigerant, and the gas refrigerant (Ts1) is sucked from the suction port 57 of the low-stage compressor 1 and sucked. The gas refrigerant is compressed again by the low-stage compressor 1 and the high-stage compressor 3.

  Note that the discharge temperature of the low stage compressor 1 is Td1, the suction temperature of the high stage compressor 3 is Ts2, the inflow temperature of the high stage economizer port 72 is Tm2s, and the inflow temperature of the low stage economizer port 70 is Tm1s. The temperature of the compression stroke part of the low stage compressor 1 into which the low stage economizer flows is denoted by Ti1.

As described above, the refrigerant is reliably cooled by the high stage economizer cooler 120 and the low stage economizer cooler 124 before being sent to the expansion means 106 of the main refrigerant circuit 108. Specific enthalpy h can be reduced, and the cooling capacity of the refrigeration / cooling system 100 can be improved.
Further, the compression work of the low-stage compressor 1 and the high-stage compressor 3 is reduced by the amount of refrigerant injected into the low-stage and high-stage economizer circuits 110 and 112, and the coefficient of performance COP can be improved.

  Conventionally, in the screw type two-stage compressor having a single machine structure, the economizer effect is not provided on the low pressure stage side so that the economizer effect is difficult to obtain, but the economizer effect is provided on the low stage compressor 1 side as in the present invention. By adding such improvements as shown, the economizer effect on the low-stage compressor 1 side as shown by the line TL1 to Tm1 shown by the thick solid line in FIG. The COP of the refrigeration / cooling system 100 can be improved by improving the refrigeration capacity.

Next, another embodiment of the refrigeration / cooling system will be described with reference to FIGS.
5 and 6 are the same except that the low-stage economizer cooler 124 and the high-stage economizer cooler 120 are different in structure. Description is omitted.

  As shown in FIG. 7, in the refrigeration / cooling system 200, the low-stage economizer cooler 132 of the low-stage economizer circuit 130 and the high-stage economizer cooler 136 of the high-stage economizer circuit 134 are respectively flash type coolers. It is configured.

  The refrigerant flowing through the main refrigerant circuit 108 that has exited the condenser 102 is sent to the high-stage economizer expansion valve 118 without being diverted, and after being reduced in pressure and temperature, the high-stage economizer cooler 136 uses the gas refrigerant and the refrigerant. Separated into liquid refrigerant. Only the gas refrigerant flows into the high stage economizer port 72 through the high stage economizer passage 114.

  Further, only the liquid refrigerant is sent from the high stage economizer cooler 136 to the low stage economizer expansion valve 122, is decompressed and cooled, and is separated into the gas refrigerant and the liquid refrigerant by the low stage economizer cooler 132. Only the gas refrigerant flows into the low-stage economizer port 70 through the low-stage economizer passage 116.

Also, the Mollier diagram of the refrigeration cycle of FIG. 7 is as shown in FIG. 8, and, similar to the embodiment of FIGS. 5 and 6, before the refrigerant is sent to the expansion means 106 of the main refrigerant circuit 108, the high Since it is reliably cooled by the stage economizer cooler 136 and the low stage economizer cooler 132, the specific enthalpy h at the inlet of the evaporator 104 can be reduced, and the cooling capacity of the refrigeration / cooling system 200 is improved. Can do.
Further, the compression work of the low-stage compressor 1 and the high-stage compressor 3 is reduced by the amount of refrigerant injected into the low-stage and high-stage economizer circuits, and the COP of the refrigeration / cooling system 200 can be improved.

As described above, since the refrigeration cycle is configured by including the single-screw type two-stage compressor 5, the air volume ratio of the low-stage compressor 1 is set large, and the low-stage compressor 1 includes an economizer cooler. Since 124 and 132 are connected, the COP of the refrigeration / cooling system is improved.
Furthermore, it becomes possible to construct a system in which the high-stage compressor 3 is reduced in size and capacity, and the safety is increased and the degree of freedom in the installation location is increased.

  Furthermore, by extending the life of the bearings 31, 35, 39, 41 of the low-stage compressor 1, and further expanding the economizer effect by expanding the opening area of the economizer port 70 of the low-stage compressor 1, the refrigeration / cooling system is improved. It is possible to achieve both long life and high efficiency.

According to the present invention, an economizer is connected to each of the low-stage compressor and the high-stage compressor, and the air volume ratio between the low-stage compressor and the high-stage compressor, that is, the theoretical displacement of the low-stage compressor is determined by the conventional method. A single-unit screw type that can be set larger than when an economizer is not connected to the low-stage compressor, and the economizer effect can be effectively demonstrated in the low-stage compressor by setting the low-stage compressor to a high compression ratio. A multi-stage compressor can be provided.
In addition, an economizer port structure that allows refrigerant from the economizer cooler to more easily flow into the low-stage compressor and discharge from the low-stage compressor in order to increase the compression of the low-stage compressor and exert the economizer effect. It is possible to provide a single-screw multi-stage compressor provided with a support structure for dealing with a thrust load acting on a low-stage compressor accompanying an increase in pressure.
Furthermore, according to the present invention, a refrigeration / cooling system that exhibits high COP can be provided by configuring a refrigeration / cooling circuit using the single-screw multistage compressor.
For this reason, it is useful when applied to a refrigeration / cooling circuit configured using a single-screw multistage compressor.

DESCRIPTION OF SYMBOLS 1 Low stage compressor 3 High stage compressor 5 Single machine screw type 2 stage (multistage) compressor 7 Low stage male rotor 9 Low stage female rotor 13 High stage male rotor 15 High stage female rotor 25 Motor 57, 65 Suction port 59, 67 Exhaust Outlet 63 Intermediate pressure chamber 70 Low economizer port 72 High economizer port 76 Male economizer port 78 Female economizer port 80 Balance passage 102 Condenser 104 Evaporator 106 Expansion means 108 Main refrigerant circuit 124, 132 Low stage Economizer cooler 120, 136 High-stage economizer cooler 110, 134 High-stage economizer circuit 112, 130 Low-stage economizer circuit

Claims (4)

In a single-screw multi-stage compressor in which a low-stage compressor and a high-stage compressor comprising a pair of male and female screw rotors and a drive motor are combined in series,
The low-stage compressor is provided with a low-stage economizer port to which a low-stage economizer cooler is connected, the motor is constituted by a hermetic motor, and the motor is connected to the suction side of the low-stage compressor. A balance passage for guiding the pressure of the intermediate pressure chamber connecting the discharge port of the low-stage compressor and the suction port of the high-stage compressor or the pressure of the compression stroke portion of the high-stage compressor to the motor chamber. A single-screw multi-stage compressor characterized by the above.   The single-screw multi-stage compressor according to claim 1, wherein the refrigerant-dissolved lubricating oil supplied to the bearing of the low-stage compressor is returned to the motor chamber of the hermetic motor.   The screw rotor of the low-stage compressor is horizontally arranged, the screw rotor of the high-stage compressor is vertically arranged perpendicular to the arrangement direction of the low-stage compression screw rotor, and the balance passage is horizontally arranged in the low-stage compressor. 2. The single-screw multistage compressor according to claim 1, wherein the single-screw multi-stage compressor is disposed through a lower portion of the disposed screw rotor. A main refrigerant circuit formed by the single-screw multi-stage compressor according to any one of claims 1 to 3, a condenser, an evaporator, and expansion means, a downstream side of the condenser, and a position of the evaporator On the upstream side, the main refrigerant circuit is provided with a high stage economizer circuit and a low stage economizer circuit, and the high stage economizer passage of the high stage economizer circuit is connected to the high stage economizer port of the high stage compressor. And a low-stage economizer passage of the low-stage economizer circuit connected to a low-stage economizer port of the low-stage compressor.

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