JP2011032957A - Screw compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw compressor achieving a high IPLV (Integrated Part Load Value) and improving energy efficiency in the actual operation. <P>SOLUTION: In a casing 1, a fixed port 12 is formed for delivering compressed fluid in a screw groove 2a to a delivery port 11 by being opened to the delivery port 11 when a partial load with respect to the full load is 50-75%. Therefore, it is possible to reduce a discharge pressure loss caused when the partial load is 50-75% in the high speed operation by an inverter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a screw compressor.

  Conventionally, a screw compressor includes a casing, a screw rotor disposed in the casing, and a slide valve that changes an internal volume ratio of the screw rotor (Japanese Patent No. 4147891: Patent Document 1). reference).

Japanese Patent No. 4147891

  However, in the conventional screw compressor, the slide valve only changes the internal volume ratio of the screw rotor, and it has not been considered to improve the energy efficiency of actual operation.

  Here, the energy efficiency of actual operation is determined by the IPLV (Integrated Part Load Value) standard as a period performance coefficient. That is, the conventional screw compressor does not consider this IPLV.

  Therefore, an object of the present invention is to provide a screw compressor that can realize high IPLV and improve the energy efficiency of actual operation.

In order to solve the above problems, the screw compressor of the present invention is
A casing having a discharge port;
A screw rotor disposed in the casing;
A slide valve for adjusting the timing of discharging the compressed fluid in the screw groove of the screw rotor to the discharge port;
A motor that rotationally drives the screw rotor;
An inverter that controls the rotation frequency of the motor according to the load;
A control unit for controlling the discharge timing of the slide valve according to the load,
The casing is provided with a fixed port that opens to the discharge port and discharges the compressed fluid in the screw groove to the discharge port when the partial load is 50% to 75% with respect to the total load. It is characterized by.

  According to the screw compressor of the present invention, when the casing has a partial load of 50% to 75% with respect to the total load, the casing is opened to the discharge port, and the compressed fluid in the screw groove is supplied to the discharge port. Since a fixed port for discharging is provided, it is possible to reduce the discharge pressure loss that occurs when the partial load is 50% to 75% by high-speed operation with an inverter. As a result, high IPLV can be realized, and actual operation To improve energy efficiency.

  Moreover, in the screw compressor of one Embodiment, the said fixed port is located in the screw rotor rotation direction rear side rather than the said slide valve.

  According to the screw compressor of this embodiment, since the fixed port is located behind the slide valve in the rotational direction of the screw rotor, before the screw groove communicates with the discharge port of the slide valve. The screw groove can be communicated with the fixed port, and the discharge pressure loss can be reliably reduced.

  According to the screw compressor of the present invention, when the casing has a partial load of 50% to 75% with respect to the total load, the casing opens to the discharge port and allows the compressed fluid in the screw groove to flow into the discharge port. Since a fixed port for discharging is provided, a high IPLV can be realized and the energy efficiency of actual operation is improved.

It is a simplified lineblock diagram showing one embodiment of a screw compressor of the present invention. It is a simplified top view of a screw compressor. It is a table | surface which shows the relationship between a load factor and IPLV. It is a table | surface which shows the product of the theoretical COP and IPLV weight of each load factor. It is a graph which shows the relationship between a load factor and discharge pressure loss.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

  FIG. 1: has shown the simple block diagram which is one Embodiment of the screw compressor of this invention. FIG. 2 shows a simplified plan view of the expanded state of the screw compressor.

  As shown in FIGS. 1 and 2, the screw compressor includes a casing 1, a screw rotor 2 disposed in a cylinder portion 10 of the casing 1, and a slide disposed along the outer periphery of the screw rotor 2. And a valve 3.

  A pair of gate rotors 4, 4 are arranged outside the screw rotor 2 in the radial direction so as to sandwich the screw rotor 2.

  A plurality of spiral screw grooves 2 a are provided on the outer peripheral surface of the screw rotor 2. The gate rotor 4 has a disk shape, and a plurality of tooth portions 4 a are provided on the outer peripheral surface of the gate rotor 4 along the circumferential direction. The tooth portion 4a meshes with the screw groove 2a. The compression chamber 5 is formed by the meshing of the screw groove 2a and the tooth portion 4a.

  The screw rotor 2 is connected to a motor 6, and the motor 6 drives the screw rotor 2 to rotate around the axis, and the rotation of the screw rotor 2 causes the gate rotor 4 to move to the axis of the screw rotor 2. Rotates around a vertical axis. In FIG. 2, the screw groove 2a moves in the arrow A direction, and the tooth portion 4a moves in the arrow B direction.

  An inverter 7 is connected to the motor 6, and the inverter 7 controls the rotational frequency of the motor 6 according to the load.

  Due to the rotation of the screw rotor 2, the low-pressure fluid (refrigerant gas) sucked from one end side of the screw rotor 2 is sent to the other end side of the screw rotor 2 while being compressed in the compression chamber 5 and compressed. A high-pressure fluid is discharged to a discharge port 11 formed in the cylinder portion 10 of the casing 1. One end side of the screw rotor 2 is a low-pressure LP side filled with a low-pressure fluid, and the other end side of the screw rotor 2 is a high-pressure HP side filled with a high-pressure fluid.

  The slide valve 3 is fitted in a fitting recess 16 formed in the cylinder portion 10 so as to be reciprocally movable along the axial direction of the screw rotor 2. The slide valve 3 adjusts the timing at which the compressed fluid in the screw groove 2 a of the screw rotor 2 is discharged to the discharge port 11. The slide valve 3 performs the maximum efficiency operation according to the load by changing the discharge timing from the screw rotor 2. The lower the load, the faster the discharge timing.

  The slide valve 3 is moved to the low pressure LP side and the high pressure HP side by the drive unit 8. The drive unit 8 is controlled by the control unit 9, and the control unit 9 controls the discharge timing of the slide valve 3 according to the load.

  In order to accelerate the discharge timing of the slide valve 3, the slide valve 3 is moved to the low pressure LP side by moving the slide valve 3 to the low pressure LP side. The discharge port 31 is communicated with the compression chamber 5, and the compression chamber 5 is communicated with the discharge port 11 at an early timing. On the other hand, the discharge timing of the slide valve 3 is delayed by moving the slide valve 3 to the high pressure HP side.

  The cylinder portion 10 of the casing 1 is provided with a fixed port 12 on the other end side (high-pressure HP side) of the screw rotor 2. The fixed port 12 is located behind the slide valve 3 in the rotational direction of the screw rotor 2.

  One of the fixed ports 12 opens to the slide valve 3 side (side surface of the fitting recess 16), and the other opens to the screw rotor 2 side (inner surface of the cylinder portion 10). The fixed port 12 communicates with the discharge port 11 when opened by the slide valve 3, and does not communicate with the discharge port 11 when closed by the slide valve 3.

  The fixed port 12 opens to the discharge port 11 and discharges the compressed fluid in the screw groove 2a to the discharge port 11 when the partial load is 50% to 75% with respect to the total load. That is, when the slide valve 3 is in a position corresponding to a partial load of 50% to 75%, the fixed port 12 is opened by the slide valve 3 so as to communicate with the discharge port 11 and the fixed port 12 is Communicating with the compression chamber 5 before communicating with the discharge port 31 of the slide valve 3.

  Here, the relationship between the load factor and the IPLV will be described with reference to FIG.

  As shown in FIG. 3, (1) load factor, (2) outside air temperature, and (3) water temperature are values determined by standards. The (4) condenser temperature, (5) evaporator temperature, (6) compression ratio, and (7) volume ratio are values that vary depending on the heat exchange system. (8) The theoretical COP is a value determined by (4) condenser temperature and (5) evaporator temperature. (9) The IPLV weight is a value determined by the standard. (10) Theoretical COP × IPLV weight is the product of (8) theoretical COP and (9) IPLV weight. (11) Theoretical IPLV is the sum of (10) Theoretical COP × IPLV weight for each load factor.

  FIG. 4 shows (10) theoretical COP × IPLV weight for each load factor. As shown in FIG. 4, the value when the load factor is 50% is the largest in the IPLV. For this reason, if a fixed port is provided with the aim of reducing the discharge pressure loss at a load factor of 50%, the IPLV can be increased.

  However, in actual operation, the higher the load factor, the faster the screw rotor 2 is operated by the inverter 7, and the higher the operation, the higher the discharge pressure loss. Therefore, the discharge pressure loss is reduced at a load factor of 50% to 75%. IPLV can be increased by providing a fixed port aiming at the above.

  FIG. 5 shows the relationship between the load factor and the discharge pressure loss. The horizontal axis represents the load factor, and the vertical axis represents the discharge pressure loss. The rotational speed of the screw rotor 2 was increased as the load factor was higher. When the fixed port 12 of the present invention is provided, the graph is shown by a solid line a, and when the fixed port 12 of the present invention is not provided, the graph is shown by a dotted line b. As a result, in the present invention shown by the solid line a, the discharge pressure loss can be greatly reduced as compared with the case shown by the dotted line b.

  According to the screw compressor having the above configuration, when the casing 1 has a partial load of 50% to 75% with respect to the total load, the casing 1 opens to the discharge port 11 and discharges the compressed fluid in the screw groove 2a. 11 is provided with a fixed port 12 for discharging, so that the inverter 7 can be operated at high speed and the discharge pressure loss generated when the partial load is 50% to 75% can be reduced. As a result, a high IPLV can be realized. , Improve the energy efficiency of actual operation.

  Further, since the fixed port 12 is located behind the slide valve 3 in the rotational direction of the screw rotor 2, the screw groove 2 a is formed before the screw groove 2 a communicates with the discharge port 31 of the slide valve 3. It is possible to communicate with the fixed port 12 and reliably reduce the discharge pressure loss.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, the slide valve may have a function of changing the internal volume ratio (VI) of the screw rotor in addition to the function of changing the discharge timing. The screw compressor is a twin screw compressor that forms a compression chamber by engagement of two screw rotors, in addition to a single screw compressor that forms a compression chamber by engagement of one screw rotor and a gate rotor. Also good.

DESCRIPTION OF SYMBOLS 1 Casing 10 Cylinder part 11 Discharge port 12 Fixed port 2 Screw rotor 2a Screw groove 3 Slide valve 31 Discharge port 4 Gate rotor 4a Tooth part 5 Compression chamber 6 Motor 7 Inverter 8 Drive part 9 Control part

Claims (2)

A casing (1) having a discharge port (11);
A screw rotor (2) disposed in the casing (1);
A slide valve (3) for adjusting the timing of discharging the compressed fluid in the screw groove (2a) of the screw rotor (2) to the discharge port (11);
A motor (6) for rotationally driving the screw rotor (2);
An inverter (7) for controlling the rotational frequency of the motor (6) according to a load;
A control unit (9) for controlling the discharge timing of the slide valve (3) according to the load,
When the casing (1) has a partial load of 50% to 75% with respect to the total load, the casing (1) opens to the discharge port (11) to allow the compressed fluid in the screw groove (2a) to flow to the discharge port ( 11) A screw compressor characterized in that a fixed port (12) for discharging is provided. The screw compressor according to claim 1,
The screw compressor according to claim 1, wherein the fixed port (12) is located behind the slide valve (3) in the rotational direction of the screw rotor (2).

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