JPH05223090A - Turbo-compressor - Google Patents

Abstract

PURPOSE:To provide structure for a turbo-compressor which is highly efficient and capable of reducing thrust power produced by compression impellers, in a compressor for turbo type refrigerating machine, etc., especially in a single- shaft two-stage compressor. CONSTITUTION:In a single-shaft two-stage compressor having compression blades 4, 5 on both ends of a motor shaft 3, bypass pipings 9, 10 for using a part of refrigerant 6 compressed by the first stage compression blade 4 to cool a drive motor from the middle of the outlet piping 7 on the first stage compression blade 4 side, and for returning the refrigerant to an inlet piping on the second stage compression blade 5 side after cooling the drive motor, are provided. Thus, structure which is capable of providing resistance equivalent to pressure loss produced due to the passage of the refrigerant through a section of the drive motor between the outlet piping on the first stage side and the inlet piping on the second stage side, is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo compressor used for air conditioning and heating, and more particularly to the structure of the compressor part.

[0002]

2. Description of the Related Art A turbo chiller is used as a relatively large capacity air conditioning system equipment for building air conditioning and district heat supply. The structure of the compressor of this turbo refrigerator is such that the compression vanes are rotated to a predetermined number of rotations through a drive motor and a gearbox to compress the refrigerant, and the refrigerant is compressed to a high temperature and high pressure, and a condenser ( It is used for heating by exchanging heat with cooling water in a heat exchanger). In addition, after passing through the condenser, the refrigerant expands in the expander to a low temperature and low pressure, and this time heat is exchanged with cold water in the evaporator (heat exchanger), and this cold water is used for cooling. The refrigerant that has passed through the evaporator is compressed again by the compression blades, and the cycle is repeated.

The compression blade usually has an oil-lubricated bearing, and this oil needs a lubricating oil that is excellent in mixing and separating properties with the refrigerant, but the lubricating oil mixes in the refrigerant. An oil separator is required, and the performance of the heat exchanger is deteriorated due to the mixing of the lubricating oil, so that the efficiency of the refrigerator is reduced.

When the drive motor is installed externally, heat loss from the drive motor also occurs. Further, in the single-shaft two-stage compressor, the thrust force has a value of several tons, so that the structure of the thrust bearing becomes complicated.

[0005]

As described above, since the thrust force generated by the compression blades of the compressor of the turbo refrigerator, especially the single-shaft two-stage compressor has a value of several tons, the structure of the thrust bearing is Not only becomes complicated, but also heat loss due to thrust force occurs, and the circulating amount of lubricating oil also increases, so that the efficiency of the refrigerator decreases and maintenance also increases.

Further, when the drive motor is installed outside, not only the heat loss from the drive motor cannot be recovered, but also the thrust bearing and the radial bearing need to be lubricated with oil, which lowers the efficiency of the refrigerator and the refrigerant. It is necessary to thoroughly investigate the miscibility with the lubricating oil and the like, and in particular, regarding the compatibility of the lubricating oil with the new refrigerant, there is a problem that a new lubricating oil needs to be developed.

The present invention has been made in view of the above problems, and is directed to a single-shaft two-stage compressor in which an inverter motor or the like is used to drive the motor directly to high speed rotation and to provide compression blades at both ends of the motor shaft. By cooling the drive motor with the refrigerant gas, the thrust force of the thrust bearing is reduced to provide an efficient turbo compressor structure.

[0008]

A single-shaft two-stage compressor in which a drive motor is directly rotated at a high speed. In a single-shaft two-stage compressor having compression blades at both ends of a motor shaft, the first stage is used for cooling the motor. Bypassing a part of the outlet refrigerant gas on the compression blade side and introducing it to the first-stage compression blade side for cooling the motor,
After cooling the motor, a bypass pipe for returning this refrigerant gas to the inlet side on the second-stage compression blade side is provided, and the drive motor portion is connected to the refrigerant between the first-stage side outlet pipe and the second-stage side inlet pipe. It should have a resistance corresponding to the pressure loss due to passage.

Further, if a non-contact type magnetic bearing is used for the bearing portion, oil lubrication is not required, so that oil separation from the refrigerant gas is not required, and not only the structure as a refrigerator is simplified but also an evaporator / The performance of the heat exchanger used for the condenser can be improved, that is, the efficiency of the refrigerator can be improved.

[0010]

[Function] The pressure level on the first stage side of the single-shaft two-stage compressor is, for example, about 0.5ata at the inlet, about 1.1ata at the outlet, and the pressure level at the second stage is about 1.1ata at the inlet and about 1.9ata at the outlet. The level is higher on the second stage side, and the thrust force acting on the motor shaft by the dynamic and static pressure components generated by the compression blades is high on the second stage side even if the first stage side and the second stage side are canceled out. Side to the first stage side, but if configured as described above, that is, the refrigerant gas at the first stage outlet is supplied to the first stage compression blade side of the motor for cooling the motor, and after cooling the motor, the motor is cooled. By returning to the inlet side of the two-stage compression blade, a pressure difference is generated in the motor section, so that thrust force acts from the high-pressure first stage side to the low-pressure second stage side, which causes the thrust force generated by the compression blade. It works like canceling. This relative thrust force becomes smaller as the pressure difference at the motor inlet / outlet increases.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a compressor part of a turbo refrigerator according to the present invention. The compressor part of the turbo refrigerator is a motor / rotor for obtaining a set rotation speed by driving an inverter. 1 and a motor / stator 2 to form a uniaxial two-stage compressor having a two-stage compression vane 4 and a two-stage compression vane 5 at both ends of a motor shaft 3. And is introduced into the two-stage compression blade 5 through the pipe 7. An orifice 8 for providing a pressure difference is provided in the middle of the pipe 7, and the refrigerant gas 6 is divided into two stages by a bypass pipe 9 for cooling the motor from before the orifice 8 and a bypass pipe 10 behind the orifice 8. It is introduced into the compression blade 5. Here, the orifice 8 has an orifice diameter commensurate with the pressure loss in the motor section.

The motor shaft 3 is supported by radial bearings 11 and 12, and axially supported by thrust bearings 13 and 14. In particular, if a non-contact type bearing such as a magnetic bearing is used, friction loss does not occur, resulting in low noise and low loss.
Further, it is possible to have a structure that requires no lubricating oil. By configuring as above,

The pressure level on the one-stage side of the single-shaft two-stage compressor as shown in FIG. 1 is about 0.5ata at the inlet and about 1.1ata at the outlet, and the pressure level at the two-stage side is about 1.1ata at the inlet and about 1.9 outlet. ata,
Naturally, the pressure level is higher on the second stage side, and the thrust force acting on the motor shaft 3 by the dynamic pressure / static pressure components generated by the compression blades 5, 4 cancels the first and second stages. , It acts from the second-stage side with a high pressure level to the first-stage side. Here, for cooling the motor, the refrigerant gas 6 at the first-stage outlet is supplied to the first-stage compression blade side 9 of the motor, and after cooling the motor, it is returned to the inlet-side 10 of the second-stage compression blade of the motor. Since there is a pressure difference between the two parts, the thrust force acts from the high pressure first stage side to the low pressure second stage side, which acts to cancel the thrust force generated by the compression blades, as shown in FIG. Similarly, the larger the pressure difference at the motor inlet / outlet, the smaller the relative thrust force.

Furthermore, when a non-contact type magnetic bearing is used for the bearing portion, oil lubrication is not required, so that separation of refrigerant gas from oil is not required, and thus an oil separator is not required, and a refrigerator is used. Not only does the structure become simpler, but since the refrigerant liquid does not contain oil, the performance of the heat exchanger used in the evaporator / condenser can be improved, and the efficiency of the turbo refrigerator can be improved.

Further, since oil lubrication is not required, any refrigerant liquid can be used, and there is an advantage that oil development and selection for the refrigerant is unnecessary.

[0016]

As described above, according to the present invention, the motor is directly driven by the inverter to rotate at a high speed, and the motor is cooled in the one-shaft two-stage compressor having the compression blades at both ends of the motor shaft. A part of the refrigerant gas at the first-stage outlet is bypassed and introduced to the first-stage blade side of the motor for cooling the motor, and after cooling the motor, the refrigerant gas is returned to the second-stage blade inlet side. As a result, the heat generation loss in the motor section can be recovered, and the thrust force generated by the compression blades can be offset by the pressure difference due to the refrigerant gas, and the generated thrust force can be minimized.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing an embodiment of a turbo compressor of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the pressure difference due to the refrigerant gas and the thrust.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor rotor 2 ... Motor stator 3 ... Motor shaft 4 ... 1st stage compression blade 5 ... 2nd stage compression blade 6 ... Refrigerant gas 7 ... Piping 8 ... Orifice 9,10 ... Bypass piping 11, 12 ... Radial bearing 13, 14 ... Thrust bearing

Claims (1)

[Claims] 1. A compression blade is provided at both ends of a drive motor shaft,
A single-shaft two-stage compressor that rotates the compression blades to a predetermined rotation speed by the drive motor, and sends a cooling medium (hereinafter, referred to as a refrigerant) compressed by the first-stage compression blades to the second-stage compression blades. In the two-stage turbo compressor, the part of the refrigerant compressed by the first-stage compression blade is used for cooling the drive motor from the middle of the outlet pipe on the first-stage compression blade side, and after the drive motor is cooled. Bypass pipes that return to the inlet pipe on the second-stage compression blade side are provided again, and the drive motor portion is cooled by the refrigerant between the outlet pipe on the first-stage compression blade side and the inlet pipe on the second-stage compression blade side. A turbo compressor characterized by having a structure having a resistance commensurate with the pressure loss caused by passage.